Next Issue
Previous Issue

E-Mail Alert

Add your e-mail address to receive forthcoming issues of this journal:

Journal Browser

Journal Browser

Table of Contents

Materials, Volume 9, Issue 9 (September 2016)

  • Issues are regarded as officially published after their release is announced to the table of contents alert mailing list.
  • You may sign up for e-mail alerts to receive table of contents of newly released issues.
  • PDF is the official format for papers published in both, html and pdf forms. To view the papers in pdf format, click on the "PDF Full-text" link, and use the free Adobe Readerexternal link to open them.
Cover Story The relatively limited number of efficient energy conversion materials has driven many scientists [...] Read more.
View options order results:
result details:
Displaying articles 1-83
Export citation of selected articles as:

Research

Jump to: Review, Other

Open AccessArticle Fabrication and Physical Evaluation of Gelatin-Coated Carbonate Apatite Foam
Materials 2016, 9(9), 711; doi:10.3390/ma9090711
Received: 18 June 2016 / Revised: 28 July 2016 / Accepted: 16 August 2016 / Published: 23 August 2016
PDF Full-text (13416 KB) | HTML Full-text | XML Full-text
Abstract
Carbonate apatite (CO3Ap) foam has gained much attention in recent years because of its ability to rapidly replace bone. However, its mechanical strength is extremely low for clinical use. In this study, to understand the potential of gelatin-reinforced CO3Ap
[...] Read more.
Carbonate apatite (CO3Ap) foam has gained much attention in recent years because of its ability to rapidly replace bone. However, its mechanical strength is extremely low for clinical use. In this study, to understand the potential of gelatin-reinforced CO3Ap foam for bone replacement, CO3Ap foam was reinforced with gelatin and the resulting physical characteristics were evaluated. The mechanical strength increased significantly with the gelatin reinforcement. The compressive strength of gelatin-free CO3Ap foam was 74 kPa whereas that of the gelatin-reinforced CO3Ap foam, fabricated using 30 mass % gelatin solution, was approximately 3 MPa. Heat treatment for crosslinking gelatin had little effect on the mechanical strength of the foam. The gelatin-reinforced foam did not maintain its shape when immersed in a saline solution as this promoted swelling of the gelatin; however, in the same conditions, the heat-treated gelatin-reinforced foam proved to be stable. It is concluded, therefore, that heat treatment is the key to the fabrication of stable gelatin-reinforced CO3Ap foam. Full article
(This article belongs to the Special Issue Calcium Phosphate in Biomedical Applications)
Figures

Figure 1

Open AccessArticle Experimental Study on Tensile Properties of a Novel Porous Metal Fiber/Powder Sintered Composite Sheet
Materials 2016, 9(9), 712; doi:10.3390/ma9090712
Received: 16 July 2016 / Revised: 15 August 2016 / Accepted: 17 August 2016 / Published: 23 August 2016
Cited by 1 | PDF Full-text (12815 KB) | HTML Full-text | XML Full-text
Abstract
A novel porous metal fiber/powder sintered composite sheet (PMFPSCS) is developed by sintering a mixture of a porous metal fiber sintered sheet (PMFSS) and copper powders with particles of a spherical shape. The characteristics of the PMFPSCS including its microstructure, sintering density and
[...] Read more.
A novel porous metal fiber/powder sintered composite sheet (PMFPSCS) is developed by sintering a mixture of a porous metal fiber sintered sheet (PMFSS) and copper powders with particles of a spherical shape. The characteristics of the PMFPSCS including its microstructure, sintering density and porosity are investigated. A uniaxial tensile test is carried out to study the tensile behaviors of the PMFPSCS. The deformation and failure mechanisms of the PMFSCS are discussed. Experimental results show that the PMFPSCS successively experiences an elastic stage, hardening stage, and fracture stage under tension. The tensile strength of the PMFPSCS is determined by a reticulated skeleton of fibers and reinforcement of copper powders. With the porosity of the PMFSS increasing, the tensile strength of the PMFPSCS decreases, whereas the reinforcement of copper powders increases. At the elastic stage, the structural elastic deformation is dominant, and at the hardening stage, the plastic deformation is composed of the structural deformation and the copper fibers’ plastic deformation. The fracture of the PMFPSCS is mainly caused by the breaking of sintering joints. Full article
(This article belongs to the Section Porous Materials)
Figures

Figure 1

Open AccessArticle The Shear Mechanisms of Natural Fractures during the Hydraulic Stimulation of Shale Gas Reservoirs
Materials 2016, 9(9), 713; doi:10.3390/ma9090713
Received: 27 July 2016 / Revised: 14 August 2016 / Accepted: 18 August 2016 / Published: 23 August 2016
PDF Full-text (6985 KB) | HTML Full-text | XML Full-text
Abstract
The shearing of natural fractures is important in the permeability enhancement of shale gas reservoirs during hydraulic fracturing treatment. In this work, the shearing mechanisms of natural fractures are analyzed using a newly proposed numerical model based on the displacement discontinuities method. The
[...] Read more.
The shearing of natural fractures is important in the permeability enhancement of shale gas reservoirs during hydraulic fracturing treatment. In this work, the shearing mechanisms of natural fractures are analyzed using a newly proposed numerical model based on the displacement discontinuities method. The fluid-rock coupling system of the model is carefully designed to calculate the shearing of fractures. Both a single fracture and a complex fracture network are used to investigate the shear mechanisms. The investigation based on a single fracture shows that the non-ignorable shearing length of a natural fracture could be formed before the natural fracture is filled by pressurized fluid. Therefore, for the hydraulic fracturing treatment of the naturally fractured shale gas reservoirs, the shear strength of shale is generally more important than the tensile strength. The fluid-rock coupling propagation processes of a complex fracture network are simulated under different crustal stress conditions and the results agree well with those of the single fracture. The propagation processes of complex fracture network show that a smaller crustal stress difference is unfavorable to the shearing of natural fractures, but is favorable to the formation of complex fracture network. Full article
(This article belongs to the Section Energy Materials)
Figures

Open AccessArticle Formation and Entrapment of Tris(8-hydroxyquinoline)aluminum from 8-Hydroxyquinoline in Anodic Porous Alumina
Materials 2016, 9(9), 715; doi:10.3390/ma9090715
Received: 31 May 2016 / Revised: 12 August 2016 / Accepted: 16 August 2016 / Published: 24 August 2016
Cited by 1 | PDF Full-text (3101 KB) | HTML Full-text | XML Full-text
Abstract
The formation and entrapment of tris(8-hydroxyquinoline)aluminum (Alq3) molecules on the surface of anodic porous alumina (APA) immersed in an ethanol solution of 8-hydroxyquinoline (HQ) were investigated by absorption, fluorescence, and Raman spectroscopies. The effects of the selected APA preparation conditions (galvanostatic
[...] Read more.
The formation and entrapment of tris(8-hydroxyquinoline)aluminum (Alq3) molecules on the surface of anodic porous alumina (APA) immersed in an ethanol solution of 8-hydroxyquinoline (HQ) were investigated by absorption, fluorescence, and Raman spectroscopies. The effects of the selected APA preparation conditions (galvanostatic or potentiostatic anodization method, anodizing current and voltage values, one- or two-step anodizing process, and sulfuric acid electrolyte concentration) on the adsorption and desorption of Alq3 species were examined. Among the listed parameters, sulfuric acid concentration was the most important factor in determining the Alq3 adsorption characteristics. The Alq3 content measured after desorption under galvanostatic conditions was 2.5 times larger than that obtained under potentiostatic ones, regardless of the adsorbed quantities. The obtained results suggest the existence of at least two types of adsorption sites on the APA surface characterized by different magnitudes of the Alq3 bonding strength. The related fluorescence spectra contained two peaks at wavelengths of 480 and 505 nm, which could be attributed to isolated Alq3 species inside nanovoids and aggregated Alq3 clusters in the pores of APA, respectively. The former species were attached to the adsorption sites with higher binding energies, whereas the latter ones were bound to the APA surface more weakly. Similar results were obtained for the Alq3 species formed from the HQ solution, which quantitatively exceeded the number of the Alq3 species adsorbed from the Alq3 solution. Alq3 molecules were formed in the HQ solution during the reaction of HQ molecules with the Al3+ ions in the oxide dissolution zone near the oxide/electrolyte interface through the cracks and the Al3+ ions adsorbed on surface of pore and cracks. In addition, it was suggested that HQ molecules could penetrate the nanovoids more easily than Alq3 species because of their smaller sizes, which resulted in higher magnitudes of the adsorption. Full article
(This article belongs to the Special Issue Selected Papers from ICASI 2016)
Figures

Open AccessArticle Computational Search for Two-Dimensional MX2 Semiconductors with Possible High Electron Mobility at Room Temperature
Materials 2016, 9(9), 716; doi:10.3390/ma9090716
Received: 18 July 2016 / Revised: 13 August 2016 / Accepted: 18 August 2016 / Published: 23 August 2016
Cited by 8 | PDF Full-text (2743 KB) | HTML Full-text | XML Full-text
Abstract
Neither of the two typical two-dimensional materials, graphene and single layer MoS2, are good enough for developing semiconductor logical devices. We calculated the electron mobility of 14 two-dimensional semiconductors with composition of MX2, where M (=Mo, W, Sn, Hf,
[...] Read more.
Neither of the two typical two-dimensional materials, graphene and single layer MoS 2 , are good enough for developing semiconductor logical devices. We calculated the electron mobility of 14 two-dimensional semiconductors with composition of MX 2 , where M (=Mo, W, Sn, Hf, Zr and Pt) are transition metals, and Xs are S, Se and Te. We approximated the electron phonon scattering matrix by deformation potentials, within which long wave longitudinal acoustical and optical phonon scatterings were included. Piezoelectric scattering in the compounds without inversion symmetry is also taken into account. We found that out of the 14 compounds, WS 2 , PtS 2 and PtSe 2 are promising for logical devices regarding the possible high electron mobility and finite band gap. Especially, the phonon limited electron mobility in PtSe 2 reaches about 4000 cm 2 ·V - 1 ·s - 1 at room temperature, which is the highest among the compounds with an indirect bandgap of about 1.25 eV under the local density approximation. Our results can be the first guide for experiments to synthesize better two-dimensional materials for future semiconductor devices. Full article
Figures

Figure 1

Open AccessArticle New Rhenium-Doped SrCo1−xRexO3−δ Perovskites Performing as Cathodes in Solid Oxide Fuel Cells
Materials 2016, 9(9), 717; doi:10.3390/ma9090717
Received: 8 July 2016 / Revised: 12 August 2016 / Accepted: 18 August 2016 / Published: 24 August 2016
Cited by 2 | PDF Full-text (2941 KB) | HTML Full-text | XML Full-text
Abstract
In the aim to stabilize novel three-dimensional perovskite oxides based upon SrCoO3−δ, we have designed and prepared SrCo1−xRexO3−δ phases (x = 0.05 and 0.10), successfully avoiding the competitive hexagonal 2H polytypes. Their performance as
[...] Read more.
In the aim to stabilize novel three-dimensional perovskite oxides based upon SrCoO3−δ, we have designed and prepared SrCo1−xRexO3−δ phases (x = 0.05 and 0.10), successfully avoiding the competitive hexagonal 2H polytypes. Their performance as cathode materials in intermediate-temperature solid oxide fuel cells (IT-SOFC) has been investigated. The characterization of these oxides included X-ray (XRD) and in situ temperature-dependent neutron powder diffraction (NPD) experiments for x = 0.10. At room temperature, SrCo1−xRexO3−δ perovskites are defined in the P4/mmm space group, which corresponds to a subtle tetragonal perovskite superstructure with unit-cell parameters a = b ≈ ao, c = 2ao (ao = 3.861 and 3.868 Å, for x = 0.05 and 0.10, respectively). The crystal structure evolves above 380 °C to a simple cubic perovskite unit cell, as observed from in-situ NPD data. The electrical conductivity gave maximum values of 43.5 S·cm−1 and 51.6 S·cm−1 for x = 0.05 and x = 0.10, respectively, at 850 °C. The area specific resistance (ASR) polarization resistance determined in symmetrical cells is as low as 0.087 Ω·cm2 and 0.065 Ω·cm2 for x = 0.05 and x = 0.10, respectively, at 850 °C. In single test cells these materials generated a maximum power of around 0.6 W/cm2 at 850 °C with pure H2 as a fuel, in an electrolyte-supported configuration with La0.8Sr0.2Ga0.83Mg0.17O3−δ (LSGM) as the electrolyte. Therefore, we propose the SrCo1−xRexO3−δ (x = 0.10 and 0.05) perovskite oxides as promising candidates for cathodes in IT-SOFC. Full article
(This article belongs to the Section Energy Materials)
Figures

Open AccessArticle One-Step Synthesis of Single-Wall Carbon Nanotube-ZnS Core-Shell Nanocables
Materials 2016, 9(9), 718; doi:10.3390/ma9090718
Received: 21 July 2016 / Revised: 19 August 2016 / Accepted: 19 August 2016 / Published: 24 August 2016
PDF Full-text (7856 KB) | HTML Full-text | XML Full-text
Abstract
Nanocables with a single-wall carbon nanotube (SWCNT) core and a ZnS shell were directly synthesized in one step through a thermal reaction method by using carbon, Zn, and FeS powder as starting materials. The as-fabricated nanocables were studied using scanning electron microscopy, transmission
[...] Read more.
Nanocables with a single-wall carbon nanotube (SWCNT) core and a ZnS shell were directly synthesized in one step through a thermal reaction method by using carbon, Zn, and FeS powder as starting materials. The as-fabricated nanocables were studied using scanning electron microscopy, transmission electron microscopy, and Raman spectroscopy. The nanocables have diameters of ~50 nm, lengths of several micrometers, and shell thickness of ~20 nm. TEM analysis revealed that the shell is polycrystalline wurtzite-type ZnS with good crystallinity, and the core of the nanocables is one to several SWCNTs. Raman results showed that the diameters of SWCNTs core are mainly distributed at 1.28 and 1.16 nm, with high quality and metallic character. A growth mechanism is proposed to explain the formation of the nanocables. This simple method may be applied to other SWCNTs-metal sulfide nanocables, which may have potential applications in photocatalysts, photocurrent, and other optical-electrical devices. Full article
Figures

Figure 1

Open AccessArticle Aluminium Electrodeposition from Ionic Liquid: Effect of Deposition Temperature and Sonication †
Materials 2016, 9(9), 719; doi:10.3390/ma9090719
Received: 17 June 2016 / Revised: 9 August 2016 / Accepted: 12 August 2016 / Published: 24 August 2016
Cited by 3 | PDF Full-text (6910 KB) | HTML Full-text | XML Full-text
Abstract
Since their discovery, ionic liquids (ILs) have attracted a wide interest for their potential use as a medium for many chemical processes, in particular electrochemistry. As electrochemical media they allow the electrodeposition of elements that are impossible to reduce in aqueous media. We
[...] Read more.
Since their discovery, ionic liquids (ILs) have attracted a wide interest for their potential use as a medium for many chemical processes, in particular electrochemistry. As electrochemical media they allow the electrodeposition of elements that are impossible to reduce in aqueous media. We have investigated the electrodeposition of aluminium from 1-butyl-3-methyl-imidazolium chloride ((Bmim)Cl)/AlCl3 (40/60 mol %) as concerns the effect of deposition parameters on the quality of the deposits. Thick (20 μm) aluminium coatings were electrodeposited on brass substrates at different temperatures and mixing conditions (mechanical stirring and sonication). These coatings were investigated by means of scanning electron microscope, roughness measurements, and X-ray diffraction to assess the morphology and the phase composition. Finally, electrochemical corrosion tests were carried out with the intent to correlate the deposition parameters to the anti-corrosion properties. Full article
(This article belongs to the Section Manufacturing Processes and Systems)
Figures

Figure 1

Open AccessArticle Experimental and Simulated Investigations of Thin Polymer Substrates with an Indium Tin Oxide Coating under Fatigue Bending Loadings
Materials 2016, 9(9), 720; doi:10.3390/ma9090720
Received: 13 July 2016 / Revised: 14 August 2016 / Accepted: 17 August 2016 / Published: 24 August 2016
Cited by 3 | PDF Full-text (3550 KB) | HTML Full-text | XML Full-text
Abstract
Stress-induced failure is a critical concern that influences the mechanical reliability of an indium tin oxide (ITO) film deposited on a transparently flexible polyethylene terephthalate (PET) substrate. In this study, a cycling bending mechanism was proposed and used to experimentally investigate the influences
[...] Read more.
Stress-induced failure is a critical concern that influences the mechanical reliability of an indium tin oxide (ITO) film deposited on a transparently flexible polyethylene terephthalate (PET) substrate. In this study, a cycling bending mechanism was proposed and used to experimentally investigate the influences of compressive and tensile stresses on the mechanical stability of an ITO film deposited on PET substrates. The sheet resistance of the ITO film, optical transmittance of the ITO-coated PET substrates, and failure scheme within the ITO film were measured to evaluate the mechanical stability of the concerned thin films. The results indicated that compressive and tensile stresses generated distinct failure schemes within an ITO film and both led to increased sheet resistance and optical transmittance. In addition, tensile stress increased the sheet resistance of an ITO film more easily than compressive stress did. However, the influences of both compressive and tensile stress on increased optical transmittance were demonstrated to be highly similar. Increasing the thickness of a PET substrate resulted in increased sheet resistance and optical transmittance regardless of the presence of compressive or tensile stress. Moreover, J-Integral, a method based on strain energy, was used to estimate the interfacial adhesion strength of the ITO-PET film through the simulation approach enabled by a finite element analysis. Full article
(This article belongs to the Special Issue Selected Papers from ICBEI2015)
Figures

Figure 1

Open AccessArticle Microstructure Evolution of HSLA Pipeline Steels after Hot Uniaxial Compression
Materials 2016, 9(9), 721; doi:10.3390/ma9090721
Received: 25 July 2016 / Revised: 16 August 2016 / Accepted: 19 August 2016 / Published: 24 August 2016
Cited by 2 | PDF Full-text (8838 KB) | HTML Full-text | XML Full-text
Abstract
The mechanical properties of the high-strength low-alloy pipeline steels were mainly controlled by the subsequent phase transformations after rolling. The influence of hot uniaxial compression on the phase transformation of acicular ferrite was explored by viewing of the deformation degree, the deformation temperature,
[...] Read more.
The mechanical properties of the high-strength low-alloy pipeline steels were mainly controlled by the subsequent phase transformations after rolling. The influence of hot uniaxial compression on the phase transformation of acicular ferrite was explored by viewing of the deformation degree, the deformation temperature, and the strain rate. The results show that the increase of deformation amounts raises the transformation starting and finishing temperature during the subsequent cooling and also promotes the polygonal ferrite transformation, which leads to the decrease of Vickers hardness accordingly. With the increasing of the deformation temperature, the achieved microstructure becomes coarsened and thus decreases the hardness. As the strain rate increases, the microstructure is refined and thus the hardness increases gradually; increasing the strain rate appropriately is beneficial to the refinement of the microstructure. Full article
(This article belongs to the Special Issue Physical Metallurgy of High Performance Alloys)
Figures

Figure 1

Open AccessArticle Phase Morphology and Mechanical Properties of Cyclic Butylene Terephthalate Oligomer-Containing Rubbers: Effect of Mixing Temperature
Materials 2016, 9(9), 722; doi:10.3390/ma9090722
Received: 10 June 2016 / Revised: 31 July 2016 / Accepted: 17 August 2016 / Published: 24 August 2016
PDF Full-text (12868 KB) | HTML Full-text | XML Full-text
Abstract
In this work, the effect of mixing temperature (Tmix) on the mechanical, rheological, and morphological properties of rubber/cyclic butylene terephthalate (CBT) oligomer compounds was studied. Apolar (styrene butadiene rubber, SBR) and polar (acrylonitrile butadiene rubber, NBR) rubbers were modified by CBT
[...] Read more.
In this work, the effect of mixing temperature (Tmix) on the mechanical, rheological, and morphological properties of rubber/cyclic butylene terephthalate (CBT) oligomer compounds was studied. Apolar (styrene butadiene rubber, SBR) and polar (acrylonitrile butadiene rubber, NBR) rubbers were modified by CBT (20 phr) for reinforcement and viscosity reduction. The mechanical properties were determined in tensile, tear, and dynamical mechanical analysis (DMTA) tests. The CBT-caused viscosity changes were assessed by parallel-plate rheometry. The morphology was studied by scanning electron microscopy (SEM). CBT became better dispersed in the rubber matrices with elevated mixing temperatures (at which CBT was in partially molten state), which resulted in improved tensile properties. With increasing mixing temperature the size of the CBT particles in the compounds decreased significantly, from few hundred microns to 5–10 microns. Compounding at temperatures above 120 °C and 140 °C for NBR and SBR, respectively, yielded reduced tensile mechanical properties most likely due to the degradation of the base rubber. The viscosity reduction by CBT was more pronounced in mixes with coarser CBT dispersions prepared at lower mixing temperatures. Full article
(This article belongs to the Special Issue Advances in Research on Elastomers)
Figures

Figure 1

Open AccessArticle Improved Ablation Resistance of Silicone Rubber Composites by Introducing Montmorillonite and Silicon Carbide Whisker
Materials 2016, 9(9), 723; doi:10.3390/ma9090723
Received: 18 June 2016 / Revised: 5 August 2016 / Accepted: 18 August 2016 / Published: 24 August 2016
Cited by 3 | PDF Full-text (8671 KB) | HTML Full-text | XML Full-text
Abstract
Montmorillonite (MMT) was added to silicone rubber (SR) to improve the ablation resistance of the silicone. Following this, different quantities of silicon carbide whiskers (SiCw) were incorporated into the MMT/SR to yield a hybrid, ablative composite. The tensile strength and elongation at break
[...] Read more.
Montmorillonite (MMT) was added to silicone rubber (SR) to improve the ablation resistance of the silicone. Following this, different quantities of silicon carbide whiskers (SiCw) were incorporated into the MMT/SR to yield a hybrid, ablative composite. The tensile strength and elongation at break of the composite increased after the addition of MMT. The ablation test results showed that MMT helped to form a covering layer by bonding with the silica and other components on the ablated surface. The linear and mass ablation rates exhibited decreases of 22.5% and 18.2%, respectively, in comparison to a control sample. After further incorporation of SiCw as the second filler, the resulting composites exhibited significantly higher tensile strength and ablation resistance, but not particularly lower elongation at break in comparison to the control sample. The SiCw/MMT fillers were beneficial in forming a dense and compact covering layer that delayed the heat and oxygen diffusion into the inner layers, which improved the ablation properties effectively. The remaining whiskers acted as a micro skeleton to maintain the composite’s char strength. Compared to the control sample, the linear and mass ablation rates of the composite after incorporating 6 phr SiCw and 10 phr MMT decreased by 59.2% and 43.6%, respectively. These experimental results showed that the fabricated composites exhibited outstanding mechanical properties and excellent ablation resistance. Full article
(This article belongs to the Section Advanced Composites)
Figures

Figure 1

Open AccessArticle Upscaling of a Batch De-Vulcanization Process for Ground Car Tire Rubber to a Continuous Process in a Twin Screw Extruder
Materials 2016, 9(9), 724; doi:10.3390/ma9090724
Received: 28 June 2016 / Revised: 1 August 2016 / Accepted: 17 August 2016 / Published: 24 August 2016
PDF Full-text (2284 KB) | HTML Full-text | XML Full-text
Abstract
As a means to decrease the amount of waste tires and to re-use tire rubber for new tires, devulcanization of ground passenger car tires is a promising process. Being an established process for NR and EPDM, earlier work has shown that for ground
[...] Read more.
As a means to decrease the amount of waste tires and to re-use tire rubber for new tires, devulcanization of ground passenger car tires is a promising process. Being an established process for NR and EPDM, earlier work has shown that for ground passenger car tire rubber with a relatively high amount of SBR, a devulcanization process can be formulated, as well. This was proven for a laboratory-scale batch process in an internal mixer, using diphenyl disulfide as the devulcanization aid and powder-sized material. In this paper, the devulcanization process for passenger car tire rubber is upscaled from 15 g per batch and transformed into a continuous process in a co-rotating twin screw extruder with a capacity of 2 kg/h. As SBR is rather sensitive to devulcanization process conditions, such as thermal and mechanical energy input, the screw design was based on a low shear concept. A granulate with particle sizes from 1–3.5 mm was chosen for purity, as well as economic reasons. The devulcanization process conditions were fine-tuned in terms of: devulcanization conditions (time/temperature profile, concentration of devulcanization aid), extruder parameters (screw configuration, screw speed, fill factor) and ancillary equipment (pre-treatment, extrudate handling). The influence of these parameters on the devulcanization efficiency and the quality of the final product will be discussed. The ratio of random to crosslink scission as determined by a Horikx plot was taken for the evaluation of the process and material. A best practice for continuous devulcanization will be given. Full article
(This article belongs to the Special Issue Advances in Research on Elastomers)
Figures

Figure 1

Open AccessArticle Low–Threshold and High Intensity Random Lasing Enhanced by MnCl2
Materials 2016, 9(9), 725; doi:10.3390/ma9090725
Received: 10 July 2016 / Revised: 17 August 2016 / Accepted: 19 August 2016 / Published: 24 August 2016
Cited by 1 | PDF Full-text (3005 KB) | HTML Full-text | XML Full-text
Abstract
Energy transfer is known to have a significant influence on random lasers. However, the study about the effect of energy transfer between metallic salt and dye molecules on random lasers is still lacking at present. Here, we investigate random lasing actions in Pyrromethene-597
[...] Read more.
Energy transfer is known to have a significant influence on random lasers. However, the study about the effect of energy transfer between metallic salt and dye molecules on random lasers is still lacking at present. Here, we investigate random lasing actions in Pyrromethene-597 (PM597), PM597-doped MnCl2 (manganese (II) chloride), PM597-doped polymer-dispersed liquid crystal (PDLC) and PM597-doped PDLC with MnCl2 capillary systems. We find that random lasing of the systems with MnCl2 exhibits lower threshold, higher intensity, sharper peak and variable resonance wavelength in comparison with the systems without MnCl2. This behavior is closely related to the decrease of fluorescence quenching effect and the enhancement of local field induced by energy transfer between MnCl2 and PM597. Red-shift of wavelength is observed with increasing dosage concentration of MnCl2 in the PM597-doped PDLC with MnCl2 system. Through the analysis of single-shot emission spectra of PM597-doped PDLC without and with MnCl2 systems, the role of MnCl2 in the coupling of lasing modes is confirmed. Lengths of laser oscillation cavities of the PM597-doped PDLC without and with MnCl2 systems are calculated by a power Fourier transform (PFT) analysis of their emission spectra. It well accounts for the effect of MnCl2 on the variation of the oscillation cavity. Full article
(This article belongs to the Section Energy Materials)
Figures

Open AccessArticle Mechanical and Electronic Properties of XC6 and XC12
Materials 2016, 9(9), 726; doi:10.3390/ma9090726
Received: 14 July 2016 / Revised: 14 August 2016 / Accepted: 22 August 2016 / Published: 25 August 2016
Cited by 1 | PDF Full-text (3707 KB) | HTML Full-text | XML Full-text
Abstract
A series of carbon-based superconductors XC6 with high Tc were reported recently. In this paper, based on the first-principles calculations, we studied the mechanical properties of these structures, and further explored the XC12 phases, where the X atoms are from
[...] Read more.
A series of carbon-based superconductors XC6 with high Tc were reported recently. In this paper, based on the first-principles calculations, we studied the mechanical properties of these structures, and further explored the XC12 phases, where the X atoms are from elemental hydrogen to calcium, except noble gas atoms. The mechanically- and dynamically-stable structures include HC6, NC6, and SC6 in XC6 phases, and BC12, CC12, PC12, SC12, ClC12, and KC12 in XC12 phases. The doping leads to a weakening in mechanical properties and an increase in the elastic anisotropy. C6 has the lowest elastic anisotropy, and the anisotropy increases with the atomic number of doping atoms for both XC6 and XC12. Furthermore, the acoustic velocities, Debye temperatures, and the electronic properties are also studied. Full article
(This article belongs to the Special Issue Computational Multiscale Modeling and Simulation in Materials Science)
Figures

Figure 1

Open AccessArticle Design of Decorated Self-Assembling Peptide Hydrogels as Architecture for Mesenchymal Stem Cells
Materials 2016, 9(9), 727; doi:10.3390/ma9090727
Received: 29 April 2016 / Revised: 18 August 2016 / Accepted: 19 August 2016 / Published: 26 August 2016
PDF Full-text (9809 KB) | HTML Full-text | XML Full-text
Abstract
Hydrogels from self-assembling ionic complementary peptides have been receiving a lot of interest from the scientific community as mimetic of the extracellular matrix that can offer three-dimensional supports for cell growth or can become vehicles for the delivery of stem cells, drugs or
[...] Read more.
Hydrogels from self-assembling ionic complementary peptides have been receiving a lot of interest from the scientific community as mimetic of the extracellular matrix that can offer three-dimensional supports for cell growth or can become vehicles for the delivery of stem cells, drugs or bioactive proteins. In order to develop a 3D “architecture” for mesenchymal stem cells, we propose the introduction in the hydrogel of conjugates obtained by chemoselective ligation between a ionic-complementary self-assembling peptide (called EAK) and three different bioactive molecules: an adhesive sequence with 4 Glycine-Arginine-Glycine-Aspartic Acid-Serine-Proline (GRGDSP) motifs per chain, an adhesive peptide mapped on h-Vitronectin and the growth factor Insulin-like Growth Factor-1 (IGF-1). The mesenchymal stem cell adhesion assays showed a significant increase in adhesion and proliferation for the hydrogels decorated with each of the synthesized conjugates; moreover, such functionalized 3D hydrogels support cell spreading and elongation, validating the use of this class of self-assembly peptides-based material as very promising 3D model scaffolds for cell cultures, at variance of the less realistic 2D ones. Furthermore, small amplitude oscillatory shear tests showed that the presence of IGF-1-conjugate did not alter significantly the viscoelastic properties of the hydrogels even though differences were observed in the nanoscale structure of the scaffolds obtained by changing their composition, ranging from long, well-defined fibers for conjugates with adhesion sequences to the compact and dense film for the IGF-1-conjugate. Full article
(This article belongs to the Special Issue Bioinspired and Biomimetic Materials)
Figures

Figure 1

Open AccessArticle Study of Different Sol-Gel Coatings to Enhance the Lifetime of PDMS Devices: Evaluation of Their Biocompatibility
Materials 2016, 9(9), 728; doi:10.3390/ma9090728
Received: 20 July 2016 / Revised: 12 August 2016 / Accepted: 23 August 2016 / Published: 25 August 2016
PDF Full-text (6871 KB) | HTML Full-text | XML Full-text
Abstract
A study of PDMS (polydimethylsiloxane) sol-gel–coated channels fabricated using soft lithography and a laser direct writing technique is presented. PDMS is a biocompatible material that presents a high versatility to reproduce several structures. It is widely employed in the fabrication of preclinical devices
[...] Read more.
A study of PDMS (polydimethylsiloxane) sol-gel–coated channels fabricated using soft lithography and a laser direct writing technique is presented. PDMS is a biocompatible material that presents a high versatility to reproduce several structures. It is widely employed in the fabrication of preclinical devices due to its advantages but it presents a rapid chemical deterioration to organic solvents. The use of sol-gel layers to cover the PDMS overcomes this problem since it provides the robustness of glass for the structures made with PDMS, decreasing its deterioration and changing the biocompatibility of the surface. In this work, PDMS channels are coated with three different kinds of sol-gel compositions (60MTES/40TEOS, 70MTES/30TISP and 80MTES/20TISP). The endothelial cell adhesion to the different coated devices is evaluated in order to determine the most suitable sol-gel preparation conditions to enhance cellular adhesion. Full article
(This article belongs to the Special Issue Advances in Bendable and Soft Material Film)
Figures

Figure 1

Open AccessArticle Combined Effects of Non-Conforming Fly Ash and Recycled Masonry Aggregates on Mortar Properties
Materials 2016, 9(9), 729; doi:10.3390/ma9090729
Received: 2 August 2016 / Revised: 18 August 2016 / Accepted: 19 August 2016 / Published: 25 August 2016
PDF Full-text (3319 KB) | HTML Full-text | XML Full-text
Abstract
This work evaluates the effects of using non-conforming fly ash (Nc-FA) generated in a thermoelectric power plant as filler material for mortars made with natural sand (NA) and recycled sand from masonry waste (FRMA). The incorporation of powdered recycled masonry filler (R-MF) is
[...] Read more.
This work evaluates the effects of using non-conforming fly ash (Nc-FA) generated in a thermoelectric power plant as filler material for mortars made with natural sand (NA) and recycled sand from masonry waste (FRMA). The incorporation of powdered recycled masonry filler (R-MF) is also tested as an alternative to siliceous filler (Si-F). Three families of mortars were designed to study: the effect of replacing Si-F with Nc-FA on mortars made with NA; the effect of replacing Si-F with Nc-FA on mortars made with 50% of NA and 50% of FRMA; and the effect of replacing Si-F with R-MF on mortars made with NA and FRMA. Replacing Si-F with Nc-FA is a viable alternative that increases the mechanical strength, the workability and durability properties and decreases the shrinkage. The use of FRMA and Nc-FA improved the mechanical strength of mortars, and it slightly increased the shrinkage. The replacement of Si-F with R-MF on mortars made with FRMA is not a good alternative, because it has a negative impact on all of the properties tested. This work can help both to reduce cement and natural resources’ consumption and to increase the recycling rate of Nc-FA and FRMA. Full article
Figures

Figure 1

Open AccessArticle Screening of Osteogenic-Enhancing Short Peptides from BMPs for Biomimetic Material Applications
Materials 2016, 9(9), 730; doi:10.3390/ma9090730
Received: 15 July 2016 / Revised: 17 August 2016 / Accepted: 19 August 2016 / Published: 25 August 2016
PDF Full-text (3790 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Bone regeneration is an important issue in many situations, such as bone fracture and surgery. Umbilical cord mesenchymal stem cells (UC-MSCs) are promising cell sources for bone regeneration. Bone morphogenetic proteins and their bioactive peptides are biomolecules known to enhance the osteogenic differentiation
[...] Read more.
Bone regeneration is an important issue in many situations, such as bone fracture and surgery. Umbilical cord mesenchymal stem cells (UC-MSCs) are promising cell sources for bone regeneration. Bone morphogenetic proteins and their bioactive peptides are biomolecules known to enhance the osteogenic differentiation of MSCs. However, fibrosis can arise during the development of implantable biomaterials. Therefore, it is important to control cell organization by enhancing osteogenic proliferation and differentiation and inhibiting fibroblast proliferation. Thus, we focused on the screening of such osteogenic-enhancing peptides. In the present study, we developed new peptide array screening platforms to evaluate cell proliferation and alkaline phosphatase activity in osteoblasts, UC-MSCs and fibroblasts. The conditions for the screening platform were first defined using UC-MSCs and an osteogenic differentiation peptide known as W9. Next, in silico screening to define the candidate peptides was carried out to evaluate the homology of 19 bone morphogenetic proteins. Twenty-five candidate 9-mer peptides were selected for screening. Finally, the screening of osteogenic-enhancing (osteogenic cell-selective proliferation and osteogenic differentiation) short peptide was carried out using the peptide array method, and three osteogenic-enhancing peptides were identified, confirming the validity of this screening. Full article
(This article belongs to the Special Issue Advances in Biointerfaces)
Figures

Open AccessArticle Preparation and Application of Water-in-Oil Emulsions Stabilized by Modified Graphene Oxide
Materials 2016, 9(9), 731; doi:10.3390/ma9090731
Received: 5 June 2016 / Revised: 20 August 2016 / Accepted: 22 August 2016 / Published: 26 August 2016
Cited by 4 | PDF Full-text (3897 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
A series of alkyl chain modified graphene oxides (AmGO) with different alkyl chain length and content was fabricated using a reducing reaction between graphene oxide (GO) and alkyl amine. Then AmGO was used as a graphene-based particle emulsifier to stabilize Pickering emulsion. Compared
[...] Read more.
A series of alkyl chain modified graphene oxides (AmGO) with different alkyl chain length and content was fabricated using a reducing reaction between graphene oxide (GO) and alkyl amine. Then AmGO was used as a graphene-based particle emulsifier to stabilize Pickering emulsion. Compared with the emulsion stabilized by GO, which was oil-in-water type, all the emulsions stabilized by AmGO were water-in-oil type. The effects of alkyl chain length and alkyl chain content on the emulsion properties of AmGO were investigated. The emulsions stabilized by AmGO showed good stability within a wide range of pH (from pH = 1 to pH = 13) and salt concentrations (from 0.1 to 1000 mM). In addition, the application of water-in-oil emulsions stabilized by AmGO was investigated. AmGO/polyaniline nanocomposite (AmGO/PANi) was prepared through an emulsion approach, and its supercapacitor performance was investigated. This research broadens the application of AmGO as a water-in-oil type emulsion stabilizer and in preparing graphene-based functional materials. Full article
(This article belongs to the Special Issue Pickering Emulsion and Derived Materials) Printed Edition available
Figures

Figure 1

Open AccessArticle Structure and Transport Properties of Dense Polycrystalline Clathrate-II (K,Ba)16(Ga,Sn)136 Synthesized by a New Approach Employing SPS
Materials 2016, 9(9), 732; doi:10.3390/ma9090732
Received: 11 July 2016 / Revised: 15 August 2016 / Accepted: 22 August 2016 / Published: 26 August 2016
Cited by 1 | PDF Full-text (2005 KB) | HTML Full-text | XML Full-text
Abstract
Tin clathrate-II framework-substituted compositions are of current interest as potential thermoelectric materials for medium-temperature applications. A review of the literature reveals different compositions reported with varying physical properties, which depend strongly on the exact composition as well as the processing conditions. We therefore
[...] Read more.
Tin clathrate-II framework-substituted compositions are of current interest as potential thermoelectric materials for medium-temperature applications. A review of the literature reveals different compositions reported with varying physical properties, which depend strongly on the exact composition as well as the processing conditions. We therefore initiated an approach whereby single crystals of two different (K,Ba)16(Ga,Sn)136 compositions were first obtained, followed by grinding of the crystals into fine powder for low temperature spark plasma sintering consolidation into dense polycrystalline solids and subsequent high temperature transport measurements. Powder X-ray refinement results indicate that the hexakaidecahedra are empty, K and Ba occupying only the decahedra. Their electrical properties depend on composition and have very low thermal conductivities. The structural and transport properties of these materials are compared to that of other Sn clathrate-II compositions. Full article
(This article belongs to the Special Issue Inorganic Clathrate Materials)
Figures

Figure 1

Open AccessArticle SEM Analysis of the Interfacial Transition Zone between Cement-Glass Powder Paste and Aggregate of Mortar under Microwave Curing
Materials 2016, 9(9), 733; doi:10.3390/ma9090733
Received: 17 June 2016 / Revised: 15 August 2016 / Accepted: 22 August 2016 / Published: 27 August 2016
PDF Full-text (10039 KB) | HTML Full-text | XML Full-text
Abstract
In order to investigate the effects of microwave curing on the microstructure of the interfacial transition zone of mortar prepared with a composite binder containing glass powder and to explain the mechanism of microwave curing on the improvement of compressive strength, in this
[...] Read more.
In order to investigate the effects of microwave curing on the microstructure of the interfacial transition zone of mortar prepared with a composite binder containing glass powder and to explain the mechanism of microwave curing on the improvement of compressive strength, in this study, the compressive strength of mortar under microwave curing was compared against mortar cured using (a) normal curing at 20 ± 1 °C with relative humidity (RH) > 90%; (b) steam curing at 40 °C for 10 h; and (c) steam curing at 80 °C for 4 h. The microstructure of the interfacial transition zone of mortar under the four curing regimes was analyzed by Scanning electron microscopy (SEM). The results showed that the improvement of the compressive strength of mortar under microwave curing can be attributed to the amelioration of the microstructure of the interfacial transition zone. The hydration degree of cement is accelerated by the thermal effect of microwave curing and Na+ partially dissolved from the fine glass powder to form more reticular calcium silicate hydrate, which connects the aggregate, calcium hydroxide, and non-hydrated cement and glass powder into a denser integral structure. In addition, a more stable triangular structure of calcium hydroxide contributes to the improvement of compressive strength. Full article
Figures

Figure 1

Open AccessArticle New Supercapacitors Based on the Synergetic Redox Effect between Electrode and Electrolyte
Materials 2016, 9(9), 734; doi:10.3390/ma9090734
Received: 27 July 2016 / Revised: 23 August 2016 / Accepted: 23 August 2016 / Published: 29 August 2016
Cited by 1 | PDF Full-text (4325 KB) | HTML Full-text | XML Full-text
Abstract
Redox electrolytes can provide significant enhancement of capacitance for supercapacitors. However, more important promotion comes from the synergetic effect and matching between the electrode and electrolyte. Herein, we report a novel electrochemical system consisted of a polyanilline/carbon nanotube composite redox electrode and a
[...] Read more.
Redox electrolytes can provide significant enhancement of capacitance for supercapacitors. However, more important promotion comes from the synergetic effect and matching between the electrode and electrolyte. Herein, we report a novel electrochemical system consisted of a polyanilline/carbon nanotube composite redox electrode and a hydroquinone (HQ) redox electrolyte, which exhibits a specific capacitance of 7926 F/g in a three-electrode system when the concentration of HQ in H2SO4 aqueous electrolyte is 2 mol/L, and the maximum energy density of 114 Wh/kg in two-electrode symmetric configuration. Moreover, the specific capacitance retention of 96% after 1000 galvanostatic charge/discharge cycles proves an excellent cyclic stability. These ultrahigh performances of the supercapacitor are attributed to the synergistic effect both in redox polyanilline-based electrolyte and the redox hydroquinone electrode. Full article
(This article belongs to the Section Energy Materials)
Figures

Open AccessArticle Improved Bond Equations for Fiber-Reinforced Polymer Bars in Concrete
Materials 2016, 9(9), 737; doi:10.3390/ma9090737
Received: 10 March 2016 / Revised: 12 August 2016 / Accepted: 23 August 2016 / Published: 30 August 2016
Cited by 1 | PDF Full-text (4703 KB) | HTML Full-text | XML Full-text
Abstract
This paper explores a set of new equations to predict the bond strength between fiber reinforced polymer (FRP) rebar and concrete. The proposed equations are based on a comprehensive statistical analysis and existing experimental results in the literature. Namely, the most effective parameters
[...] Read more.
This paper explores a set of new equations to predict the bond strength between fiber reinforced polymer (FRP) rebar and concrete. The proposed equations are based on a comprehensive statistical analysis and existing experimental results in the literature. Namely, the most effective parameters on bond behavior of FRP concrete were first identified by applying a factorial analysis on a part of the available database. Then the database that contains 250 pullout tests were divided into four groups based on the concrete compressive strength and the rebar surface. Afterward, nonlinear regression analysis was performed for each study group in order to determine the bond equations. The results show that the proposed equations can predict bond strengths more accurately compared to the other previously reported models. Full article
(This article belongs to the Section Advanced Composites)
Figures

Figure 1

Open AccessArticle A Facile in Situ and UV Printing Process for Bioinspired Self-Cleaning Surfaces
Materials 2016, 9(9), 738; doi:10.3390/ma9090738
Received: 8 July 2016 / Revised: 24 August 2016 / Accepted: 25 August 2016 / Published: 30 August 2016
Cited by 3 | PDF Full-text (2713 KB) | HTML Full-text | XML Full-text
Abstract
A facile in situ and UV printing process was demonstrated to create self-cleaning synthetic replica of natural petals and leaves. The process relied on the spontaneous migration of a fluorinated acrylate surfactant (PFUA) within a low-shrinkage acrylated hyperbranched polymer (HBP) and its chemical
[...] Read more.
A facile in situ and UV printing process was demonstrated to create self-cleaning synthetic replica of natural petals and leaves. The process relied on the spontaneous migration of a fluorinated acrylate surfactant (PFUA) within a low-shrinkage acrylated hyperbranched polymer (HBP) and its chemical immobilization at the polymer-air interface. Dilute concentrations of 1 wt. % PFUA saturated the polymer-air interface within 30 min, leading to a ten-fold increase of fluorine concentration at the surface compared with the initial bulk concentration and a water contact angle (WCA) of 108°. A 200 ms flash of UV light was used to chemically crosslink the PFUA at the HBP surface prior to UV printing with a polydimethylsiloxane (PDMS) negative template of red and yellow rose petals and lotus leaves. This flash immobilization hindered the reverse migration of PFUA within the bulk HBP upon contacting the PDMS template, and enabled to produce texturized surfaces with WCA well above 108°. The synthetic red rose petal was hydrophobic (WCA of 125°) and exhibited the adhesive petal effect. It was not superhydrophobic due to insufficient concentration of fluorine at its surface, a result of the very large increase of the surface of the printed texture. The synthetic yellow rose petal was quasi-superhydrophobic (WCA of 143°, roll-off angle of 10°) and its self-cleaning ability was not good also due to lack of fluorine. The synthetic lotus leaf did not accurately replicate the intricate nanotubular crystal structures of the plant. In spite of this, the fluorine concentration at the surface was high enough and the leaf was superhydrophobic (WCA of 151°, roll-off angle below 5°) and also featured self-cleaning properties. Full article
(This article belongs to the Special Issue Materials for Photolithography and 3D Printing)
Figures

Open AccessArticle Experimental Study on Full-Scale Beams Made by Reinforced Alkali Activated Concrete Undergoing Flexure
Materials 2016, 9(9), 739; doi:10.3390/ma9090739
Received: 15 May 2016 / Revised: 24 July 2016 / Accepted: 22 August 2016 / Published: 30 August 2016
PDF Full-text (4614 KB) | HTML Full-text | XML Full-text
Abstract
Alkali Activated Concrete (AAC) is an alternative kind of concrete that uses fly ash as a total replacement of Portland cement. Fly ash combined with alkaline solution and cured at high temperature reacts to form a binder. Four point bending tests on two
[...] Read more.
Alkali Activated Concrete (AAC) is an alternative kind of concrete that uses fly ash as a total replacement of Portland cement. Fly ash combined with alkaline solution and cured at high temperature reacts to form a binder. Four point bending tests on two full scale beams made with AAC are described in this paper. Companion small material specimens were also casted with the aim of properly characterizing this new tailored material. The beam’s length was 5000 mm and the cross section was 200 mm × 300 mm. The AAC consisted of fly ash, water, sand 0–4 mm and coarse aggregate 6–10 mm; and the alkaline solution consisted of sodium hydroxide mixed with sodium silicate. No cement was utilized. The maximum aggregate size was 10 mm; fly ash was type F, containing a maximum calcium content of 2%. After a rest period of two days, the beam was cured at 60 °C for 24 h. Data collected and critically discussed included beam deflection, crack patterns, compressive and flexural strength and elastic modulus. Results show how AAC behavior is comparable with Ordinary Portland Cement (OPC) based materials. Nonlinear numerical analyses are finally reported, promoting a better understanding of the structural response. Full article
(This article belongs to the Special Issue Advances in Geopolymers and Alkali-Activated Materials)
Figures

Open AccessArticle A Modelling Study for Predicting Life of Downhole Tubes Considering Service Environmental Parameters and Stress
Materials 2016, 9(9), 741; doi:10.3390/ma9090741
Received: 15 July 2016 / Revised: 19 August 2016 / Accepted: 25 August 2016 / Published: 2 September 2016
PDF Full-text (4603 KB) | HTML Full-text | XML Full-text
Abstract
A modelling effort was made to try to predict the life of downhole tubes or casings, synthetically considering the effect of service influencing factors on corrosion rate. Based on the discussed corrosion mechanism and corrosion processes of downhole tubes, a mathematic model was
[...] Read more.
A modelling effort was made to try to predict the life of downhole tubes or casings, synthetically considering the effect of service influencing factors on corrosion rate. Based on the discussed corrosion mechanism and corrosion processes of downhole tubes, a mathematic model was established. For downhole tubes, the influencing factors are environmental parameters and stress, which vary with service duration. Stress and the environmental parameters including water content, partial pressure of H2S and CO2, pH value, total pressure and temperature, were considered to be time-dependent. Based on the model, life-span of an L80 downhole tube in oilfield Halfaya, an oilfield in Iraq, was predicted. The results show that life-span of the L80 downhole tube in Halfaya is 247 months (approximately 20 years) under initial stress of 0.1 yield strength and 641 months (approximately 53 years) under no initial stress, which indicates that an initial stress of 0.1 yield strength will reduce the life-span by more than half. Full article
(This article belongs to the Special Issue Stress Corrosion Cracking in Materials)
Figures

Figure 1

Open AccessArticle Electricity Recovery from Municipal Sewage Wastewater Using a Hydrogel Complex Composed of Microbially Reduced Graphene Oxide and Sludge
Materials 2016, 9(9), 742; doi:10.3390/ma9090742
Received: 24 June 2016 / Revised: 17 August 2016 / Accepted: 19 August 2016 / Published: 31 August 2016
Cited by 2 | PDF Full-text (2253 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Graphene oxide (GO) has recently been shown to be an excellent anode substrate for exoelectrogens. This study demonstrates the applicability of GO in recovering electricity from sewage wastewater. Anaerobic incubation of sludge with GO formed a hydrogel complex that embeds microbial cells via
[...] Read more.
Graphene oxide (GO) has recently been shown to be an excellent anode substrate for exoelectrogens. This study demonstrates the applicability of GO in recovering electricity from sewage wastewater. Anaerobic incubation of sludge with GO formed a hydrogel complex that embeds microbial cells via π-π stacking of microbially reduced GO. The rGO complex was electrically conductive (23 mS·cm−1) and immediately produced electricity in sewage wastewater under polarization at +200 mV vs. Ag/AgCl. Higher and more stable production of electricity was observed with rGO complexes (179–310 μA·cm−3) than with graphite felt (GF; 79–95 μA·cm−3). Electrochemical analyses revealed that this finding was attributable to the greater capacitance and smaller internal resistance of the rGO complex. Microbial community analysis showed abundances of Geobacter species in both rGO and GF complexes, whereas more diverse candidate exoelectrogens in the Desulfarculaceae family and Geothrix genus were particularly prominent in the rGO complex. Full article
(This article belongs to the Special Issue Microbial Fuel Cells)
Figures

Open AccessArticle Effect of Low Pressure on Surface Roughness and Morphological Defects of 4H-SiC Epitaxial Layers
Materials 2016, 9(9), 743; doi:10.3390/ma9090743
Received: 27 June 2016 / Revised: 27 July 2016 / Accepted: 22 August 2016 / Published: 31 August 2016
Cited by 1 | PDF Full-text (18384 KB) | HTML Full-text | XML Full-text
Abstract
In this work, 4H-SiC epilayers are performed on 4° off-axis substrates under low pressure condition by horizontal hot wall chemical vapor deposition (HWCVD) with a standard chemistry of silane-propane-hydrogen, which focuses on the effects of growth pressure on morphology, basal plane dislocations (BPDs)
[...] Read more.
In this work, 4H-SiC epilayers are performed on 4° off-axis substrates under low pressure condition by horizontal hot wall chemical vapor deposition (HWCVD) with a standard chemistry of silane-propane-hydrogen, which focuses on the effects of growth pressure on morphology, basal plane dislocations (BPDs) and crystalline quality. It is found that morphological defects reduce with the decreasing of growth pressure, since the surface diffusion length of absorbed adatoms increases under low growth pressure, which suppresses the nucleation of adatoms on terraces and the formation of morphological defects. However, as the surface diffusion length increases under low growth pressure, the difference of growth velocity at steps is enhanced, which leads to the extension of the steps’ width and the formation of step-bunching. Besides variation of surface diffusion length, the phenomenon described above can be correlated with different dominate modes for the minimization of surface energy at varied growth pressure. Because of the contrary influence of increased C/Si ratio and enhanced step-flow growth on the propagation of BPDs, the dislocation densities of BPDs and threading edge dislocations (TEDs) in epilayers grown at varied pressures remain basically unchanged. The crystalline quality is almost independent of growth pressure based on high resolution X-ray diffraction (HRXRD) measurements. Full article
(This article belongs to the Special Issue Materials Grown by Metal-Organic Vapour Phase Epitaxy)
Figures

Figure 1

Open AccessCommunication Electrochemical Hydrogel Lithography of Calcium-Alginate Hydrogels for Cell Culture
Materials 2016, 9(9), 744; doi:10.3390/ma9090744
Received: 31 July 2016 / Revised: 12 August 2016 / Accepted: 22 August 2016 / Published: 31 August 2016
Cited by 4 | PDF Full-text (2952 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Here we propose a novel electrochemical lithography methodology for fabricating calcium-alginate hydrogels having controlled shapes. We separated the chambers for Ca2+ production and gel formation with alginate with a semipermeable membrane. Ca2+ formed in the production chamber permeated through the membrane
[...] Read more.
Here we propose a novel electrochemical lithography methodology for fabricating calcium-alginate hydrogels having controlled shapes. We separated the chambers for Ca2+ production and gel formation with alginate with a semipermeable membrane. Ca2+ formed in the production chamber permeated through the membrane to fabricate a gel structure on the membrane in the gel formation chamber. When the calcium-alginate hydrogels were modified with collagen, HepG2 cells proliferated on the hydrogels. These results show that electrochemical hydrogel lithography is useful for cell culture. Full article
(This article belongs to the Special Issue Smart Hydrogels for (Bio)printing Applications)
Figures

Figure 1

Open AccessArticle A Scanning Transmission X-ray Microscopy Study of Cubic and Orthorhombic C3A and Their Hydration Products in the Presence of Gypsum
Materials 2016, 9(9), 745; doi:10.3390/ma9090745
Received: 20 June 2016 / Revised: 10 August 2016 / Accepted: 23 August 2016 / Published: 31 August 2016
Cited by 1 | PDF Full-text (5258 KB) | HTML Full-text | XML Full-text
Abstract
This paper shows the microstructural differences and phase characterization of pure phases and hydrated products of the cubic and orthorhombic (Na-doped) polymorphs of tricalcium aluminate (C3A), which are commonly found in traditional Portland cements. Pure, anhydrous samples were characterized using scanning
[...] Read more.
This paper shows the microstructural differences and phase characterization of pure phases and hydrated products of the cubic and orthorhombic (Na-doped) polymorphs of tricalcium aluminate (C3A), which are commonly found in traditional Portland cements. Pure, anhydrous samples were characterized using scanning transmission X-ray microscopy (STXM), X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD) and demonstrated differences in the chemical and mineralogical composition as well as the morphology on a micro/nano-scale. C3A/gypsum blends with mass ratios of 0.2 and 1.9 were hydrated using a water/C3A ratio of 1.2, and the products obtained after three days were assessed using STXM. The hydration process and subsequent formation of calcium sulfate in the C3A/gypsum systems were identified through the changes in the LIII edge fine structure for Calcium. The results also show greater Ca LII binding energies between hydrated samples with different gypsum contents. Conversely, the hydrated samples from the cubic and orthorhombic C3A at the same amount of gypsum exhibited strong morphological differences but similar chemical environments. Full article
(This article belongs to the Section Advanced Composites)
Figures

Figure 1

Open AccessArticle Drilling of Hybrid Titanium Composite Laminate (HTCL) with Electrical Discharge Machining
Materials 2016, 9(9), 746; doi:10.3390/ma9090746
Received: 14 July 2016 / Revised: 13 August 2016 / Accepted: 24 August 2016 / Published: 1 September 2016
Cited by 1 | PDF Full-text (6584 KB) | HTML Full-text | XML Full-text
Abstract
An experimental investigation was conducted to determine the application of die sinker electrical discharge machining (EDM) as it applies to a hybrid titanium thermoplastic composite laminate material. Holes were drilled using a die sinker EDM. The effects of peak current, pulse time, and
[...] Read more.
An experimental investigation was conducted to determine the application of die sinker electrical discharge machining (EDM) as it applies to a hybrid titanium thermoplastic composite laminate material. Holes were drilled using a die sinker EDM. The effects of peak current, pulse time, and percent on-time on machinability of hybrid titanium composite material were evaluated in terms of material removal rate (MRR), tool wear rate, and cut quality. Experimental models relating each process response to the input parameters were developed and optimum operating conditions with a short cutting time, achieving the highest workpiece MRR, with very little tool wear were determined to occur at a peak current value of 8.60 A, a percent on-time of 36.12%, and a pulse time of 258 microseconds. After observing data acquired from experimentation, it was determined that while use of EDM is possible, for desirable quality it is not fast enough for industrial application. Full article
(This article belongs to the Special Issue Machining of Composites and Multi-Stacks of Aerospace Materials)
Figures

Figure 1

Open AccessArticle Annealing Effect on (FAPbI3)1−x(MAPbBr3)x Perovskite Films in Inverted-Type Perovskite Solar Cells
Materials 2016, 9(9), 747; doi:10.3390/ma9090747
Received: 27 June 2016 / Revised: 16 August 2016 / Accepted: 29 August 2016 / Published: 3 September 2016
Cited by 7 | PDF Full-text (2185 KB) | HTML Full-text | XML Full-text
Abstract
This study determines the effects of annealing treatment on the structure and the optical and electronic behaviors of the mixed (FAPbI3)1−x(MAPbBr3)x perovskite system. The experimental results reveal that (FAPbI3)1−x(MAPbBr3)x
[...] Read more.
This study determines the effects of annealing treatment on the structure and the optical and electronic behaviors of the mixed (FAPbI3)1−x(MAPbBr3)x perovskite system. The experimental results reveal that (FAPbI3)1−x(MAPbBr3)x (x ~ 0.2) is an effective light-absorbing material for use in inverted planar perovskite solar cells owing to its large absorbance and tunable band gap. Therefore, good band-matching between the (FAPbI3)1−x(MAPbBr3)x and C60 in photovoltaic devices can be controlled by annealing at various temperatures. Accordingly, an inverted mixed perovskite solar cell with a record efficiency of 12.0% under AM1.5G irradiation is realized. Full article
Figures

Figure 1

Open AccessArticle Effect of Dissolved Oxygen and Immersion Time on the Corrosion Behaviour of Mild Steel in Bicarbonate/Chloride Solution
Materials 2016, 9(9), 748; doi:10.3390/ma9090748
Received: 4 August 2016 / Revised: 20 August 2016 / Accepted: 22 August 2016 / Published: 1 September 2016
PDF Full-text (8780 KB) | HTML Full-text | XML Full-text
Abstract
The electrochemical behavior of mild steel in bicarbonate solution at different dissolved oxygen (DO) concentrations and immersion times has been studied under dynamic conditions using electrochemical techniques. The results show that both DO and immersion times influence the morphology of the corrosion products.
[...] Read more.
The electrochemical behavior of mild steel in bicarbonate solution at different dissolved oxygen (DO) concentrations and immersion times has been studied under dynamic conditions using electrochemical techniques. The results show that both DO and immersion times influence the morphology of the corrosion products. In comparative tests, the corrosion rate was systematically found to be lower in solutions with lower DO, lower HCO3 concentrations and longer immersion time. The SEM analyses reveal that the iron dissolution rate was more severe in solutions containing higher DO. The decrease in corrosion rate can be attributed to the formation of a passive layer containing mainly α -FeO (OH) and ( γ -Fe2O3/Fe3O4) as confirmed by the X-ray diffractometry (XRD) and X-ray photoelectron spectroscopy (XPS). Passivation of mild steel is evident in electrochemical test at ≈ −600 mVSCE at pH 8 in dearated ( 0.8 ppm DO) chloride bicarbonate solution under dynamic conditions. Full article
Figures

Figure 1

Open AccessArticle Passivation Characteristics of Alloy Corrosion-Resistant Steel Cr10Mo1 in Simulating Concrete Pore Solutions: Combination Effects of pH and Chloride
Materials 2016, 9(9), 749; doi:10.3390/ma9090749
Received: 2 July 2016 / Revised: 17 August 2016 / Accepted: 29 August 2016 / Published: 1 September 2016
PDF Full-text (2781 KB) | HTML Full-text | XML Full-text
Abstract
The electrochemical behaviour for passivation of new alloy corrosion-resistant steel Cr10Mo1 immersed in alkaline solutions with different pH values (13.3, 12.0, 10.5, and 9.0) and chloride contents (0.2 M and 1.0 M), was investigated by various electrochemical techniques: linear polarization resistance, electrochemical impedance
[...] Read more.
The electrochemical behaviour for passivation of new alloy corrosion-resistant steel Cr10Mo1 immersed in alkaline solutions with different pH values (13.3, 12.0, 10.5, and 9.0) and chloride contents (0.2 M and 1.0 M), was investigated by various electrochemical techniques: linear polarization resistance, electrochemical impedance spectroscopy and capacitance measurements. The chemical composition and structure of passive films were determined by XPS. The morphological features and surface composition of the immersed steel were evaluated by SEM together with EDS chemical analysis. The results evidence that pH plays an important role in the passivation of the corrosion-resistant steel and the effect is highly dependent upon the chloride contents. In solutions with low chloride (0.2 M), the corrosion-resistant steel has notably enhanced passivity with pH falling from 13.3 to 9.0, but does conversely when in presence of high chloride (1.0 M). The passive film on the corrosion-resistant steel presents a bilayer structure: an outer layer enriched in Fe oxides and hydroxides, and an inner layer, rich in Cr species. The film composition varies with pH values and chloride contents. As the pH drops, more Cr oxides are enriched in the film while Fe oxides gradually decompose. Increasing chloride promotes Cr oxides and Fe oxides to transform into their hydroxides with little protection, and this is more significant at lower pH (10.5 and 9.0). These changes annotate passivation characteristics of the corrosion-resistant steel in the solutions of different electrolyte. Full article
Figures

Open AccessArticle Effect of Stress Ratio and Loading Frequency on the Corrosion Fatigue Behavior of Smooth Steel Wire in Different Solutions
Materials 2016, 9(9), 750; doi:10.3390/ma9090750
Received: 12 July 2016 / Revised: 26 August 2016 / Accepted: 30 August 2016 / Published: 1 September 2016
Cited by 3 | PDF Full-text (15577 KB) | HTML Full-text | XML Full-text
Abstract
In this work, the effects of loading condition and corrosion solution on the corrosion fatigue behavior of smooth steel wire were discussed. The results of polarization curves and weight loss curves showed that the corrosion of steel wire in acid solution was more
[...] Read more.
In this work, the effects of loading condition and corrosion solution on the corrosion fatigue behavior of smooth steel wire were discussed. The results of polarization curves and weight loss curves showed that the corrosion of steel wire in acid solution was more severe than that in neutral and alkaline solutions. With the extension of immersion time in acid solution, the cathodic reaction of steel wire gradually changed from the reduction of hydrogen ion to the reduction of oxygen, but was always the reduction of hydrogen ion in neutral and alkaline solutions. The corrosion kinetic parameters and equivalent circuits of steel wires were also obtained by simulating the Nyquist diagrams. In corrosion fatigue test, the effect of stress ratio and loading frequency on the crack initiation mechanism was emphasized. The strong corrosivity of acid solution could accelerate the nucleation of crack tip. The initiation mechanism of crack under different conditions was summarized according to the side and fracture surface morphologies. For the crack initiation mechanism of anodic dissolution, the stronger the corrosivity of solution was, the more easily the fatigue crack source formed, while, for the crack initiation mechanism of deformation activation, the lower stress ratio and higher frequency would accelerate the generation of corrosion fatigue crack source. Full article
Figures

Figure 1

Open AccessArticle Determination of Actual Friction Factors in Metal Forming under Heavy Loaded Regimes Combining Experimental and Numerical Analysis
Materials 2016, 9(9), 751; doi:10.3390/ma9090751
Received: 8 August 2016 / Revised: 26 August 2016 / Accepted: 29 August 2016 / Published: 1 September 2016
Cited by 2 | PDF Full-text (6051 KB) | HTML Full-text | XML Full-text
Abstract
Tribological conditions can change drastically during heavy loaded regimes as experienced in metal forming; this is especially critical when lubrication can only be applied at the early stage of the process because the homogeneous lubricant layer can break along the die-workpiece interface. In
[...] Read more.
Tribological conditions can change drastically during heavy loaded regimes as experienced in metal forming; this is especially critical when lubrication can only be applied at the early stage of the process because the homogeneous lubricant layer can break along the die-workpiece interface. In these cases, adopting a constant friction factor for the lubricant-surface pair may not be a valid assumption. This paper presents a procedure based on the use of dual friction factor maps to determine friction factors employed in heavy loaded regimes. A finite element (FE) simulation is used to obtain the friction factor map for the alloy UNS A96082. Experiments were conducted using four lubricants (aluminum anti-size, MoS2 grease, silicone oil, and copper paste) to determine the actual friction curves. The experimental procedure is based on the application of lubricant only at the beginning of the first stage of ring compression, and not at intermediate stages as is usual in typical ring compression tests (RCTs). The results show that for small reductions (rh < 20%), the conventional RCT can be applied because the tribological conditions remain similar. For large reductions (rh > 20%), it is recommended to obtain an average value of the friction factor for every lubricant-surface pair in the range of deformation considered. Full article
(This article belongs to the Special Issue Numerical Analysis of Tribology Behavior of Materials)
Figures

Open AccessArticle Protection of Reinforced Concrete Structures of Waste Water Treatment Reservoirs with Stainless Steel Coating Using Arc Thermal Spraying Technique in Acidified Water
Materials 2016, 9(9), 753; doi:10.3390/ma9090753
Received: 20 April 2016 / Revised: 12 August 2016 / Accepted: 29 August 2016 / Published: 3 September 2016
Cited by 3 | PDF Full-text (19273 KB) | HTML Full-text | XML Full-text
Abstract
Waste water treatment reservoirs are contaminated with many hazardous chemicals and acids. Reservoirs typically comprise concrete and reinforcement steel bars, and the main elements responsible for their deterioration are hazardous chemicals, acids, and ozone. Currently, a variety of techniques are being used to
[...] Read more.
Waste water treatment reservoirs are contaminated with many hazardous chemicals and acids. Reservoirs typically comprise concrete and reinforcement steel bars, and the main elements responsible for their deterioration are hazardous chemicals, acids, and ozone. Currently, a variety of techniques are being used to protect reservoirs from exposure to these elements. The most widely used techniques are stainless steel plating and polymeric coating. In this study, a technique known as arc thermal spraying was used. It is a more convenient and economical method for protecting both concrete and reinforcement steel bar from deterioration in waste water treatment reservoirs. In this study, 316L stainless steel coating was applied to a concrete surface, and different electrochemical experiments were performed to evaluate the performance of coatings in different acidic pH solutions. The coating generated from the arc thermal spraying process significantly protected the concrete surface from corrosion in acidic pH solutions, owing to the formation of a double layer capacitance—a mixture of Cr3+ enriched with Cr2O3 and Cr-hydroxide in inner and Fe3+ oxide on the outer layer of the coating. The formation of this passive film is defective owing to the non-homogeneous 316L stainless steel coating surface. In the pH 5 solution, the growth of a passive film is adequate due to the presence of un-dissociated water molecules in the aqueous sulfuric acid solution. The coated surface is sealed with alkyl epoxide, which acts as a barrier against the penetration of acidic solutions. This coating exhibits higher impedance values among the three studied acidic pH solutions. Full article
Figures

Open AccessArticle The Contact Ageing Effect on Fretting Damage of an Electro-Deposited Coating against an AISI52100 Steel Ball
Materials 2016, 9(9), 754; doi:10.3390/ma9090754
Received: 2 July 2016 / Revised: 23 August 2016 / Accepted: 31 August 2016 / Published: 3 September 2016
PDF Full-text (4728 KB) | HTML Full-text | XML Full-text
Abstract
This article investigates the effect of contact ageing on fretting damage of an epoxy-based cathodic electro-deposited coating for use on automotive seat slide tracks (made of cold-rolled high strength steel). Static normal load was induced at the contact between the coating and an
[...] Read more.
This article investigates the effect of contact ageing on fretting damage of an epoxy-based cathodic electro-deposited coating for use on automotive seat slide tracks (made of cold-rolled high strength steel). Static normal load was induced at the contact between the coating and an AISI52100 ball for a certain duration. It was identified that plastically deformed contact area increased logarithmically as a function of time when the contact was under static normal load. Fretting tests after various durations of static contact were conducted using a ball-on-flat plate apparatus. All fretting tests were halted when the friction coefficient reached a critical value of 0.5, indicating complete coating failure. The total number of fretting cycles to the critical friction coefficient was found to vary with the duration of static contact before fretting. It was identified that the number of cycles to the critical friction coefficient decreased with the increased duration of static contact. Meanwhile, the friction coefficient at steady-state sliding was not greatly affected by the duration of static contact before fretting. Finally, the relation between coating thickness after indentation creep and the number of cycles to the critical friction coefficient was found to be linear. Obtained results show that the duration of static contact before fretting has an influence on the fretting lifetime of an electro-deposited coating. Full article
(This article belongs to the Special Issue Tribological Behavior of Materials by Surface Engineering)
Figures

Open AccessFeature PaperArticle A Mathematical Model on the Resolution of Extrusion Bioprinting for the Development of New Bioinks
Materials 2016, 9(9), 756; doi:10.3390/ma9090756
Received: 2 August 2016 / Revised: 29 August 2016 / Accepted: 30 August 2016 / Published: 6 September 2016
Cited by 9 | PDF Full-text (4859 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Pneumatic extrusion-based bioprinting is a recent and interesting technology that is very useful for biomedical applications. However, many process parameters in the bioprinter need to be fully understood in order to print at an adequate resolution. In this paper, a simple yet accurate
[...] Read more.
Pneumatic extrusion-based bioprinting is a recent and interesting technology that is very useful for biomedical applications. However, many process parameters in the bioprinter need to be fully understood in order to print at an adequate resolution. In this paper, a simple yet accurate mathematical model to predict the printed width of a continuous hydrogel line is proposed, in which the resolution is expressed as a function of nozzle size, pressure, and printing speed. A thermo-responsive hydrogel, pluronic F127, is used to validate the model predictions. This model could provide a platform for future correlation studies on pneumatic extrusion-based bioprinting as well as for developing new bioink formulations. Full article
(This article belongs to the Special Issue 3D Printing for Biomedical Engineering)
Figures

Figure 1

Open AccessArticle Electrospun Polymer Nanofibers Reinforced by Tannic Acid/Fe+++ Complexes
Materials 2016, 9(9), 757; doi:10.3390/ma9090757
Received: 8 June 2016 / Revised: 29 August 2016 / Accepted: 30 August 2016 / Published: 6 September 2016
Cited by 1 | PDF Full-text (2623 KB) | HTML Full-text | XML Full-text
Abstract
We report the successful preparation of reinforced electrospun nanofibers and fibrous mats of polyvinyl alcohol (PVA) via a simple and inexpensive method using stable tannic acid (TA) and ferric ion (Fe+++) assemblies formed by solution mixing and pH adjustment. Changes in
[...] Read more.
We report the successful preparation of reinforced electrospun nanofibers and fibrous mats of polyvinyl alcohol (PVA) via a simple and inexpensive method using stable tannic acid (TA) and ferric ion (Fe+++) assemblies formed by solution mixing and pH adjustment. Changes in solution pH change the number of TA galloyl groups attached to the Fe+++ from one (pH < 2) to two (3 < pH < 6) to three (pH < 7.4) and affect the interactions between PVA and TA. At pH ~ 5.5, the morphology and fiber diameter size (FDS) examined by SEM are determinant for the mechanical properties of the fibrous mats and depend on the PVA content. At an optimal 8 wt % concentration, PVA becomes fully entangled and forms uniform nanofibers with smaller FDS (p < 0.05) and improved mechanical properties when compared to mats of PVA alone and of PVA with TA (p < 0.05). Changes in solution pH lead to beads formation, more irregular FDS and poorer mechanical properties (p < 0.05). The Fe+++ inclusion does not alter the oxidation activity of TA (p > 0.05) suggesting the potential of TA-Fe+++ assemblies to reinforce polymer nanofibers with high functionality for use in diverse applications including food, biomedical and pharmaceutical. Full article
Figures

Figure 1

Open AccessArticle Fabrication of Biomass-Derived Carbon Aerogels with High Adsorption of Oils and Organic Solvents: Effect of Hydrothermal and Post-Pyrolysis Processes
Materials 2016, 9(9), 758; doi:10.3390/ma9090758
Received: 17 July 2016 / Revised: 31 August 2016 / Accepted: 1 September 2016 / Published: 6 September 2016
Cited by 1 | PDF Full-text (5056 KB) | HTML Full-text | XML Full-text
Abstract
Biomass is the most plentiful and well-utilized renewable carbon resource on the earth. Direct conversion of biomass to carbon aerogel provides a promising approach to develop adsorbent materials. In the present work, the effect of presence of water during hydrothermal treatment and holding
[...] Read more.
Biomass is the most plentiful and well-utilized renewable carbon resource on the earth. Direct conversion of biomass to carbon aerogel provides a promising approach to develop adsorbent materials. In the present work, the effect of presence of water during hydrothermal treatment and holding temperature during post-pyrolysis process have been investigated for the preparation of carbon aerogels (CAs) using eggplant as raw material. The results showed that the addition of water during hydrothermal treatment was advantageous for the preparation of CA samples with higher surface area and stronger hydrophobicity, resulting in superior adsorption capacities of CAs for both oil and organic solvents compared with that fabricated without the presence of water. The optimized carbon aerogel possessed higher specific surface of 249 m2·g−1 and exhibited excellent hydrophobicity with a water contact angle of 133°. The adsorption capacities of carbon aerogel for oils and organic solvents could reach 35–45 times its own weight. In addition, the adsorbed oil and organic solvents could be recovered by distillation, and the regenerated carbon aerogels samples exhibited the stable performance and outstanding reusability. Therefore, the carbon aerogel has great potential in application of oil recovery and environmental protection. Full article
(This article belongs to the Section Biomaterials)
Figures

Figure 1a

Open AccessArticle Carbon Supported Engineering NiCo2O4 Hybrid Nanofibers with Enhanced Electrocatalytic Activity for Oxygen Reduction Reaction
Materials 2016, 9(9), 759; doi:10.3390/ma9090759
Received: 29 July 2016 / Revised: 26 August 2016 / Accepted: 30 August 2016 / Published: 6 September 2016
Cited by 7 | PDF Full-text (2406 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
The design of cheap and efficient oxygen reduction reaction (ORR) electrocatalysts is of a significant importance in sustainable and renewable energy technologies. Therefore, ORR catalysts with superb electrocatalytic activity and durability are becoming a necessity but still remain challenging. Herein, we report C/NiCo
[...] Read more.
The design of cheap and efficient oxygen reduction reaction (ORR) electrocatalysts is of a significant importance in sustainable and renewable energy technologies. Therefore, ORR catalysts with superb electrocatalytic activity and durability are becoming a necessity but still remain challenging. Herein, we report C/NiCo2O4 nanocomposite fibers fabricated by a straightforward electrospinning technique followed by a simple sintering process as a promising ORR electrocatalyst in alkaline condition. The mixed-valence oxide can offer numerous accessible active sites. In addition, the as-obtained C/NiCo2O4 hybrid reveals significantly remarkable electrocatalytic performance with a highly positive onset potential of 0.65 V, which is only 50 mV lower than that of commercially available Pt/C catalysts. The analyses indicate that C/NiCo2O4 catalyst can catalyze O2-molecules via direct four electron pathway in a similar behavior as commercial Pt/C catalysts dose. Compared to single NiCo2O4 and carbon free NiCo2O4, the C/NiCo2O4 hybrid displays higher ORR current and more positive half-wave potential. The incorporated carbon matrices are beneficial for fast electron transfer and can significantly impose an outstanding contribution to the electrocatalytic activity. Results indicate that the synthetic strategy hold a potential as efficient route to fabricate highly active nanostructures for practical use in energy technologies. Full article
(This article belongs to the Section Energy Materials)
Figures

Figure 1

Open AccessArticle Frontal Conversion and Uniformity in 3D Printing by Photopolymerisation
Materials 2016, 9(9), 760; doi:10.3390/ma9090760
Received: 29 July 2016 / Revised: 31 August 2016 / Accepted: 2 September 2016 / Published: 7 September 2016
Cited by 4 | PDF Full-text (2642 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
We investigate the impact of the non-uniform spatio-temporal conversion, intrinsic to photopolymerisation, in the context of light-driven 3D printing of polymers. The polymerisation kinetics of a series of model acrylate and thiol-ene systems, both neat and doped with a light-absorbing dye, is investigated
[...] Read more.
We investigate the impact of the non-uniform spatio-temporal conversion, intrinsic to photopolymerisation, in the context of light-driven 3D printing of polymers. The polymerisation kinetics of a series of model acrylate and thiol-ene systems, both neat and doped with a light-absorbing dye, is investigated experimentally and analysed according to a descriptive coarse-grained model for photopolymerisation. In particular, we focus on the relative kinetics of polymerisation with those of 3D printing, by comparing the evolution of the position of the conversion profile (zf) to the sequential displacement of the object stage (∆z). After quantifying the characteristic sigmoidal monomer-to-polymer conversion of the various systems, with a combination of patterning experiments, FT-IR mapping, and modelling, we compute representative regimes for which zf is smaller, commensurate with, or larger than ∆z. While non-monotonic conversion can be detrimental to 3D printing, for instance in causing differential shrinkage of inhomogeneity in material properties, we identify opportunities for facile fabrication of modulated materials in the z-direction (i.e., along the illuminated axis). Our simple framework and model, based on directly measured parameters, can thus be employed in photopolymerisation-based 3D printing, both in process optimisation and in the precise design of complex, internally stratified materials by coupling the z-stage displacement and frontal polymerisation kinetics. Full article
(This article belongs to the Special Issue Materials for Photolithography and 3D Printing)
Figures

Open AccessArticle Nonionic Microemulsions as Solubilizers of Hydrophobic Drugs: Solubilization of Paclitaxel
Materials 2016, 9(9), 761; doi:10.3390/ma9090761
Received: 14 July 2016 / Revised: 26 August 2016 / Accepted: 2 September 2016 / Published: 7 September 2016
PDF Full-text (1152 KB) | HTML Full-text | XML Full-text
Abstract
The strategy using nonionic microemulsion as a solubilizer for hydrophobic drugs was studied and is demonstrated in this work. The aqueous phase behaviors of mixed nonionic surfactants with various oils at 37 °C are firstly constructed to give the optimal formulations of nonionic
[...] Read more.
The strategy using nonionic microemulsion as a solubilizer for hydrophobic drugs was studied and is demonstrated in this work. The aqueous phase behaviors of mixed nonionic surfactants with various oils at 37 °C are firstly constructed to give the optimal formulations of nonionic microemulsions with applications in the enhanced solubilization of the model hydrophobic drug, paclitaxel, at 37 °C. Briefly, the suitable oil phase with paclitaxel significantly dissolved is microemulsified with appropriate surfactants. Surfactants utilized include Tween 80, Cremophor EL, and polyethylene glycol (4.3) cocoyl ether, while various kinds of edible oils and fatty esters are used as the oil phase. On average, the apparent solubility of paclitaxel is increased to ca. 70–100 ppm in the prepared microemulsions at 37 °C using tributyrin or ethyl caproate as the oil phases. The sizes of the microemulsions attained are mostly from ca. 60 nm to ca. 200 nm. The cytotoxicity of the microemulsion formulations is assessed with the cellular viability of 3T3 cells. In general, the cell viability is above 55% after 24 h of cultivation in media containing these microemulsion formulations diluted to a concentration of total surfactants equal to 50 ppm and 200 ppm. Full article
(This article belongs to the Special Issue Materials for Drug Delivery and Biomedical Consideration)
Figures

Figure 1a

Open AccessArticle Operation of Thin-Film Electrolyte Metal-Supported Solid Oxide Fuel Cells in Lightweight and Stationary Stacks: Material and Microstructural Aspects
Materials 2016, 9(9), 762; doi:10.3390/ma9090762
Received: 2 August 2016 / Revised: 26 August 2016 / Accepted: 2 September 2016 / Published: 8 September 2016
Cited by 1 | PDF Full-text (10753 KB) | HTML Full-text | XML Full-text
Abstract
In this study we report on the development and operational data of a metal-supported solid oxide fuel cell with a thin film electrolyte under varying conditions. The metal-ceramic structure was developed for a mobile auxiliary power unit and offers power densities of 1
[...] Read more.
In this study we report on the development and operational data of a metal-supported solid oxide fuel cell with a thin film electrolyte under varying conditions. The metal-ceramic structure was developed for a mobile auxiliary power unit and offers power densities of 1 W/cm2 at 800 °C, as well as robustness under mechanical, thermal and chemical stresses. A dense and thin yttria-doped zirconia layer was applied to a nanoporous nickel/zirconia anode using a scalable adapted gas-flow sputter process, which allowed the homogeneous coating of areas up to 100 cm2. The cell performance is presented for single cells and for stack operation, both in lightweight and stationary stack designs. The results from short-term operation indicate that this cell technology may be a very suitable alternative for mobile applications. Full article
(This article belongs to the Special Issue Recent Advances in Materials for Solid Oxide Cells)
Figures

Open AccessArticle Novel Osteointegrative Sr-Substituted Apatitic Cements Enriched with Alginate
Materials 2016, 9(9), 763; doi:10.3390/ma9090763
Received: 8 July 2016 / Revised: 29 August 2016 / Accepted: 2 September 2016 / Published: 8 September 2016
Cited by 2 | PDF Full-text (5270 KB) | HTML Full-text | XML Full-text
Abstract
The present work describes the synthesis of novel injectable, self-setting bone cements made of strontium-substituted hydroxyapatite (Sr-HA), obtained by single-phase calcium phosphate precursors doped with different amounts of strontium and enriched with alginate. The addition of alginate improved the injectability, cohesion, and compression
[...] Read more.
The present work describes the synthesis of novel injectable, self-setting bone cements made of strontium-substituted hydroxyapatite (Sr-HA), obtained by single-phase calcium phosphate precursors doped with different amounts of strontium and enriched with alginate. The addition of alginate improved the injectability, cohesion, and compression strength of the cements, without affecting the hardening process. A Sr-HA cement exhibiting adequate hardening times and mechanical strength for clinical applications was further tested in vivo in a rabbit model, in comparison with a commercial calcium phosphate cement, revealing the maintenance of biomimetic composition and porous microstructure even after one month in vivo, as well as enhanced ability to induce new bone formation and penetration. Full article
(This article belongs to the Special Issue Bioceramics 2016)
Figures

Figure 1

Open AccessArticle Fatigue and Fracture Behavior of a Cold-Drawn Commercially Pure Aluminum Wire
Materials 2016, 9(9), 764; doi:10.3390/ma9090764
Received: 12 July 2016 / Revised: 5 September 2016 / Accepted: 5 September 2016 / Published: 8 September 2016
PDF Full-text (3463 KB) | HTML Full-text | XML Full-text
Abstract
Fatigue properties and cracking behavior of cold-drawn commercially pure aluminum wires (CPAWs) widely used as the overhead transmission conductors were investigated. It was found that the fracture surface of the CPAWs shows an obvious four-stage fracture characteristic, i.e., crack initiation, planar crack propagation,
[...] Read more.
Fatigue properties and cracking behavior of cold-drawn commercially pure aluminum wires (CPAWs) widely used as the overhead transmission conductors were investigated. It was found that the fracture surface of the CPAWs shows an obvious four-stage fracture characteristic, i.e., crack initiation, planar crack propagation, 45°-inclined crack propagation and final rapid fracture. The crack growth mechanisms for the CPAWs were found quite different from those for the conventional coarse-grained materials. The cracks in the CPAWs firstly grow along the grain boundaries (Stage I crack growth), and then grow along the plane of maximum shear stress during the last stage of cycling (Stage II crack growth), leading to the distinctive fracture surfaces, i.e., the granular surface in the planar crack propagation region and the coarse fatigue striations in the 45°-inclined crack propagation region. The grain boundary migration was observed in the fatigued CPAWs. The increase in fatigue load enhances the dislocation recovery, increases the grain boundary migration rate, and thus promotes the occurrence of softening and damage localization up to the final failure. Full article
(This article belongs to the Special Issue Fracture and Fatigue Mechanics of Materials)
Figures

Open AccessArticle Influence of the Conditioning Method for Pre-Sintered Zirconia on the Shear Bond Strength of Bilayered Porcelain/Zirconia
Materials 2016, 9(9), 765; doi:10.3390/ma9090765
Received: 3 August 2016 / Revised: 25 August 2016 / Accepted: 2 September 2016 / Published: 8 September 2016
PDF Full-text (2115 KB) | HTML Full-text | XML Full-text
Abstract
This study evaluated the bond strength of veneering porcelain with an experimental conditioner-coated zirconia. Pre-sintered Y-TZP specimens (n = 44) were divided in two groups based on conditioning type. After sintering, all sample surfaces were sandblasted and layered with veneering porcelain. Additionally,
[...] Read more.
This study evaluated the bond strength of veneering porcelain with an experimental conditioner-coated zirconia. Pre-sintered Y-TZP specimens (n = 44) were divided in two groups based on conditioning type. After sintering, all sample surfaces were sandblasted and layered with veneering porcelain. Additionally, half of the specimens in each group underwent thermal cycling (10,000 cycles, 5–55 °C), and all shear bond strengths were measured. After testing, the failure mode of each fractured specimen was determined. Differences were tested by parametric and Fisher’s exact tests (α = 0.05). The differences in bond strength were not statistically significant. Adhesive fractures were dominantly observed for the non-thermal cycled specimens. After thermal cycling, the conditioner-coated group showed cohesive and mixed fractures (p = 0.0021), whereas the uncoated group showed more adhesive fractures (p = 0.0021). Conditioning of the pre-sintered Y-TZP did not change the shear bond strength of the veneering porcelain, but did improve the failure mode after thermal cycling. Full article
(This article belongs to the Section Biomaterials)
Figures

Figure 1

Open AccessArticle The Synthesis of LiMnxFe1−xPO4/C Cathode Material through Solvothermal Jointed with Solid-State Reaction
Materials 2016, 9(9), 766; doi:10.3390/ma9090766
Received: 6 June 2016 / Revised: 1 August 2016 / Accepted: 29 August 2016 / Published: 8 September 2016
Cited by 1 | PDF Full-text (4043 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
LiMnxFe1−xPO4/C material has been synthesized through a facile solid-state reaction under the condition of carbon coating, using solvothermal-prepared LiMnPO4 and LiFePO4 as precursors and sucrose as a carbon resource. XRD and element distribution analysis
[...] Read more.
LiMnxFe1−xPO4/C material has been synthesized through a facile solid-state reaction under the condition of carbon coating, using solvothermal-prepared LiMnPO4 and LiFePO4 as precursors and sucrose as a carbon resource. XRD and element distribution analysis reveal completed solid-state reaction of precursors. LiMnxFe1−xPO4/C composites inherit the morphology of precursors after heat treatment without obvious agglomeration and size increase. LiMnxFe1−xPO4 solid solution forms at low temperature around 350 °C, and Mn2+/Fe2+ diffuse completely within 1 h at 650 °C. The LiMnxFe1−xPO4/C (x < 0.8) composite exhibits a high-discharge capacity of over 120 mAh·g−1 (500 Wh·kg−1) at low C-rates. This paves a way to synthesize the crystal-optimized LiMnxFe1−xPO4/C materials for high performance Li-ion batteries. Full article
Figures

Figure 1

Open AccessArticle Preparation and Properties of Alkali Activated Metakaolin-Based Geopolymer
Materials 2016, 9(9), 767; doi:10.3390/ma9090767
Received: 14 May 2016 / Revised: 30 August 2016 / Accepted: 2 September 2016 / Published: 8 September 2016
PDF Full-text (2346 KB) | HTML Full-text | XML Full-text
Abstract
The effective activation and utilization of metakaolin as an alkali activated geopolymer precursor and its use in concrete surface protection is of great interest. In this paper, the formula of alkali activated metakaolin-based geopolymers was studied using an orthogonal experimental design. It was
[...] Read more.
The effective activation and utilization of metakaolin as an alkali activated geopolymer precursor and its use in concrete surface protection is of great interest. In this paper, the formula of alkali activated metakaolin-based geopolymers was studied using an orthogonal experimental design. It was found that the optimal geopolymer was prepared with metakaolin, sodium hydroxide, sodium silicate and water, with the molar ratio of SiO2:Al2O3:Na2O:NaOH:H2O being 3.4:1.1:0.5:1.0:11.8. X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FT-IR) were adopted to investigate the influence of curing conditions on the mechanical properties and microstructures of the geopolymers. The best curing condition was 60 °C for 168 h, and this alkali activated metakaolin-based geopolymer showed the highest compression strength at 52.26 MPa. In addition, hollow micro-sphere glass beads were mixed with metakaolin particles to improve the thermal insulation properties of the alkali activated metakaolin-based geopolymer. These results suggest that a suitable volume ratio of metakaolin to hollow micro-sphere glass beads in alkali activated metakaolin-based geopolymers was 6:1, which achieved a thermal conductivity of 0.37 W/mK and compressive strength of 50 MPa. By adjusting to a milder curing condition, as-prepared alkali activated metakaolin-based geopolymers could find widespread applications in concrete thermal protection. Full article
(This article belongs to the Special Issue Advances in Geopolymers and Alkali-Activated Materials)
Figures

Open AccessArticle Compact Holographic Projection Display Using Liquid-Crystal-on-Silicon Spatial Light Modulator
Materials 2016, 9(9), 768; doi:10.3390/ma9090768
Received: 30 July 2016 / Revised: 29 August 2016 / Accepted: 5 September 2016 / Published: 9 September 2016
Cited by 1 | PDF Full-text (4906 KB) | HTML Full-text | XML Full-text
Abstract
This paper presents a holographic projection display in which a phase-only spatial light modulator (SLM) performs three functions: beam shaping, image display, and speckle reduction. The functions of beam shaping and image display are performed by dividing the SLM window into four sub-windows
[...] Read more.
This paper presents a holographic projection display in which a phase-only spatial light modulator (SLM) performs three functions: beam shaping, image display, and speckle reduction. The functions of beam shaping and image display are performed by dividing the SLM window into four sub-windows loaded with different diffractive phase elements (DPEs). The DPEs are calculated using a modified iterative Fourier transform algorithm (IFTA). The function of speckle reduction is performed using temporal integration of display images containing speckles. The speckle contrast ratio of the display image is 0.39 due to the integration of eight speckled images. The system can be extended to display full-color images also by using temporal addition of elementary color images. Because the system configuration needs only an SLM, a Fourier transform lens, and two mirrors, the system volume is very small, becoming a potential candidate for micro projectors. Full article
(This article belongs to the Special Issue Silicon Nanophotonics)
Figures

Open AccessArticle Comprehensive Numerical Simulation of Filling and Solidification of Steel Ingots
Materials 2016, 9(9), 769; doi:10.3390/ma9090769
Received: 4 July 2016 / Revised: 2 August 2016 / Accepted: 5 September 2016 / Published: 9 September 2016
PDF Full-text (6294 KB) | HTML Full-text | XML Full-text
Abstract
In this paper, a complete three-dimensional numerical model of mold filling and solidification of steel ingots is presented. The risk of powder entrapment and defects formation during filling is analyzed in detail, demonstrating the importance of using a comprehensive geometry, with trumpet and
[...] Read more.
In this paper, a complete three-dimensional numerical model of mold filling and solidification of steel ingots is presented. The risk of powder entrapment and defects formation during filling is analyzed in detail, demonstrating the importance of using a comprehensive geometry, with trumpet and runner, compared to conventional simplified models. By using a case study, it was shown that the simplified model significantly underestimates the defects sources, reducing the utility of simulations in supporting mold and process design. An experimental test was also performed on an instrumented mold and the measurements were compared to the calculation results. The good agreement between calculation and trial allowed validating the simulation. Full article
(This article belongs to the Section Manufacturing Processes and Systems)
Figures

Open AccessArticle Flow Chamber System for the Statistical Evaluation of Bacterial Colonization on Materials
Materials 2016, 9(9), 770; doi:10.3390/ma9090770
Received: 14 July 2016 / Revised: 1 September 2016 / Accepted: 2 September 2016 / Published: 10 September 2016
Cited by 1 | PDF Full-text (5508 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Biofilm formation on materials leads to high costs in industrial processes, as well as in medical applications. This fact has stimulated interest in the development of new materials with improved surfaces to reduce bacterial colonization. Standardized tests relying on statistical evidence are indispensable
[...] Read more.
Biofilm formation on materials leads to high costs in industrial processes, as well as in medical applications. This fact has stimulated interest in the development of new materials with improved surfaces to reduce bacterial colonization. Standardized tests relying on statistical evidence are indispensable to evaluate the quality and safety of these new materials. We describe here a flow chamber system for biofilm cultivation under controlled conditions with a total capacity for testing up to 32 samples in parallel. In order to quantify the surface colonization, bacterial cells were DAPI (4`,6-diamidino-2-phenylindole)-stained and examined with epifluorescence microscopy. More than 100 images of each sample were automatically taken and the surface coverage was estimated using the free open source software g’mic, followed by a precise statistical evaluation. Overview images of all gathered pictures were generated to dissect the colonization characteristics of the selected model organism Escherichia coli W3310 on different materials (glass and implant steel). With our approach, differences in bacterial colonization on different materials can be quantified in a statistically validated manner. This reliable test procedure will support the design of improved materials for medical, industrial, and environmental (subaquatic or subaerial) applications. Full article
(This article belongs to the Special Issue Advances in Biointerfaces)
Figures

Figure 1

Open AccessFeature PaperArticle Enhancement of TiO2 NPs Activity by Fe3O4 Nano-Seeds for Removal of Organic Pollutants in Water
Materials 2016, 9(9), 771; doi:10.3390/ma9090771
Received: 28 July 2016 / Revised: 30 August 2016 / Accepted: 5 September 2016 / Published: 10 September 2016
Cited by 3 | PDF Full-text (1463 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
The enhancement of the photocatalytic activity of TiO2 nanoparticles (NPs), synthesized in the presence of a very small amount of magnetite (Fe3O4) nanoparticles, is here presented and discussed. From X-ray diffraction (XRD) and differential scanning calorimetry (DSC) analyses,
[...] Read more.
The enhancement of the photocatalytic activity of TiO2 nanoparticles (NPs), synthesized in the presence of a very small amount of magnetite (Fe3O4) nanoparticles, is here presented and discussed. From X-ray diffraction (XRD) and differential scanning calorimetry (DSC) analyses, the crystallinity of TiO2 nanoparticles (NPs) seems to be affected by Fe3O4, acting as nano-seeds to improve the tetragonal TiO2 anatase structure with respect to the amorphous one. Photocatalytic activity data, i.e., the degradation of methylene blue and the Ofloxacin fluoroquinolone emerging pollutant, give evidence that the increased crystalline structure of the NPs, even if correlated to a reduced surface to mass ratio (with respect to commercial TiO2 NPs), enhances the performance of this type of catalyst. The achievement of a relatively well-defined crystal structure at low temperatures (Tmax = 150 °C), preventing the sintering of the TiO2 NPs and, thus, preserving the high density of active sites, seems to be the keystone to understand the obtained results. Full article
Figures

Open AccessArticle Electrochemical Corrosion Behavior of Ta2N Nanoceramic Coating in Simulated Body Fluid
Materials 2016, 9(9), 772; doi:10.3390/ma9090772
Received: 2 August 2016 / Revised: 1 September 2016 / Accepted: 3 September 2016 / Published: 10 September 2016
PDF Full-text (8109 KB) | HTML Full-text | XML Full-text
Abstract
In order to improve the corrosion and wear resistance of biomedical Ti-6Al-4V implants, a Ta2N nanoceramic coating was synthesized on a Ti-6Al-4V substrate by the double glow discharge plasma process. The Ta2N coating, composed of fine nanocrystals, with an
[...] Read more.
In order to improve the corrosion and wear resistance of biomedical Ti-6Al-4V implants, a Ta2N nanoceramic coating was synthesized on a Ti-6Al-4V substrate by the double glow discharge plasma process. The Ta2N coating, composed of fine nanocrystals, with an average grain size of 12.8 nm, improved the surface hardness of Ti-6Al-4V and showed good contact damage tolerance and good adhesion strength to the substrate. The corrosion resistance of the Ta2N coating in Ringer’s physiological solution at 37 °C was evaluated by different electrochemical techniques: potentiodynamic polarization, electrochemical impedance spectroscopy (EIS), potentiostatic polarization and capacitance measurements (Mott-Schottky approach). The evolution of the surface composition of the passive films at different applied potentials was determined by X-ray photoelectron spectroscopy (XPS). The results indicated that the Ta2N coating showed higher corrosion resistance than both commercially pure Ta and uncoated Ti-6Al-4V in this solution, because of the formed oxide film on the Ta2N coating having a smaller carrier density (Nd) and diffusivity (Do) of point defects. The composition of the surface passive film formed on the Ta2N coating changed with the applied potential. At low applied potentials, the oxidation of the Ta2N coating led to the formation of tantalum oxynitride (TaOxNy) but, subsequently, the tantalum oxynitride (TaOxNy) could be chemically converted to Ta2O5 at higher applied potentials. Full article
Figures

Figure 1

Open AccessArticle Study on Stress Development in the Phase Transition Layer of Thermal Barrier Coatings
Materials 2016, 9(9), 773; doi:10.3390/ma9090773
Received: 23 May 2016 / Revised: 7 September 2016 / Accepted: 7 September 2016 / Published: 13 September 2016
Cited by 1 | PDF Full-text (8537 KB) | HTML Full-text | XML Full-text
Abstract
Stress development is one of the significant factors leading to the failure of thermal barrier coating (TBC) systems. In this work, stress development in the two phase mixed zone named phase transition layer (PTL), which grows between the thermally grown oxide (TGO) and
[...] Read more.
Stress development is one of the significant factors leading to the failure of thermal barrier coating (TBC) systems. In this work, stress development in the two phase mixed zone named phase transition layer (PTL), which grows between the thermally grown oxide (TGO) and the bond coat (BC), is investigated by using two different homogenization models. A constitutive equation of the PTL based on the Reuss model is proposed to study the stresses in the PTL. The stresses computed with the proposed constitutive equation are compared with those obtained with Voigt model-based equation in detail. The stresses based on the Voigt model are slightly higher than those based on the Reuss model. Finally, a further study is carried out to explore the influence of phase transition proportions on the stress difference caused by homogenization models. Results show that the stress difference becomes more evident with the increase of the PTL thickness ratio in the TGO. Full article
(This article belongs to the Special Issue Multiscale Methods and Application to Computational Materials Design)
Figures

Figure 1

Open AccessArticle Investigation on the Effect of Drill Geometry and Pilot Holes on Thrust Force and Burr Height When Drilling an Aluminium/PE Sandwich Material
Materials 2016, 9(9), 774; doi:10.3390/ma9090774
Received: 14 July 2016 / Revised: 10 August 2016 / Accepted: 25 August 2016 / Published: 13 September 2016
Cited by 1 | PDF Full-text (14161 KB) | HTML Full-text | XML Full-text
Abstract
Composite materials are widely employed in the naval, aerospace and transportation industries owing to the combination of being lightweight and having a high modulus of elasticity, strength and stiffness. Drilling is an operation generally used in composite materials to assemble the final product.
[...] Read more.
Composite materials are widely employed in the naval, aerospace and transportation industries owing to the combination of being lightweight and having a high modulus of elasticity, strength and stiffness. Drilling is an operation generally used in composite materials to assemble the final product. Damages such as the burr at the drill entrance and exit, geometric deviations and delamination are typically found in composites subjected to drilling. Drills with special geometries and pilot holes are alternatives used to improve hole quality as well as to increase tool life. The present study is focused on the drilling of a sandwich composite material (two external aluminum plates bound to a polyethylene core). In order to minimize thrust force and burr height, the influence of drill geometry, the pilot hole and the cutting parameters was assessed. Thrust force and burr height values were collected and used to perform an analysis of variance. The results indicated that the tool and the cutting speed were the parameters with more weight on the thrust force and for burr height they were the tool and the interaction between tool and feed. The results indicated that drilling with a pilot hole of Ø4 mm exhibited the best performance with regard to thrust force but facilitated plastic deformation, thus leading to the elevation of burr height, while the lowest burr height was obtained using the Brad and Spur drill geometry. Full article
(This article belongs to the Special Issue Machining of Composites and Multi-Stacks of Aerospace Materials)
Figures

Figure 1

Open AccessArticle Extensive Characterization of Oxide-Coated Colloidal Gold Nanoparticles Synthesized by Laser Ablation in Liquid
Materials 2016, 9(9), 775; doi:10.3390/ma9090775
Received: 17 August 2016 / Revised: 5 September 2016 / Accepted: 12 September 2016 / Published: 14 September 2016
Cited by 3 | PDF Full-text (1676 KB) | HTML Full-text | XML Full-text
Abstract
Colloidal gold nanoparticles are a widespread nanomaterial with many potential applications, but their aggregation in suspension is a critical issue which is usually prevented by organic surfactants. This solution has some drawbacks, such as material contamination and modifications of its functional properties. The
[...] Read more.
Colloidal gold nanoparticles are a widespread nanomaterial with many potential applications, but their aggregation in suspension is a critical issue which is usually prevented by organic surfactants. This solution has some drawbacks, such as material contamination and modifications of its functional properties. The gold nanoparticles presented in this work have been synthesized by ultra-fast laser ablation in liquid, which addresses the above issues by overcoating the metal nanoparticles with an oxide layer. The main focus of the work is in the characterization of the oxidized gold nanoparticles, which were made first in solution by means of dynamic light scattering and optical spectroscopy, and then in dried form by transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and finally by surface potential measurements with atomic force microscopy. The light scattering assessed the nanoscale size of the formed particles and provided insight in their stability. The nanoparticles’ size was confirmed by direct imaging in transmission electron microscopy, and their crystalline nature was disclosed by X-ray diffraction. The X-ray photoelectron spectroscopy showed measurements compatible with the presence of surface oxide, which was confirmed by the surface potential measurements, which are the novel point of the present work. In conclusion, the method of laser ablation in liquid for the synthesis of gold nanoparticles has been presented, and the advantage of this physical approach, consisting of coating the nanoparticles in situ with gold oxide which provides the required morphological and chemical stability without organic surfactants, has been confirmed by using scanning Kelvin probe microscopy for the first time. Full article
Figures

Figure 1

Open AccessCommunication High-Surface-Area, Emulsion-Templated Carbon Foams by Activation of polyHIPEs Derived from Pickering Emulsions
Materials 2016, 9(9), 776; doi:10.3390/ma9090776
Received: 30 June 2016 / Revised: 31 August 2016 / Accepted: 9 September 2016 / Published: 14 September 2016
Cited by 5 | PDF Full-text (3295 KB) | HTML Full-text | XML Full-text
Abstract
Carbon foams displaying hierarchical porosity and excellent surface areas of >1400 m2/g can be produced by the activation of macroporous poly(divinylbenzene). Poly(divinylbenzene) was synthesized from the polymerization of the continuous, but minority, phase of a simple high internal phase Pickering emulsion.
[...] Read more.
Carbon foams displaying hierarchical porosity and excellent surface areas of >1400 m2/g can be produced by the activation of macroporous poly(divinylbenzene). Poly(divinylbenzene) was synthesized from the polymerization of the continuous, but minority, phase of a simple high internal phase Pickering emulsion. By the addition of KOH, chemical activation of the materials is induced during carbonization, producing Pickering-emulsion-templated carbon foams, or carboHIPEs, with tailorable macropore diameters and surface areas almost triple that of those previously reported. The retention of the customizable, macroporous open-cell structure of the poly(divinylbenzene) precursor and the production of a large degree of microporosity during activation leads to tailorable carboHIPEs with excellent surface areas. Full article
(This article belongs to the Special Issue Pickering Emulsion and Derived Materials) Printed Edition available
Figures

Figure 1

Open AccessArticle Effects of the CO2 Guest Molecule on the sI Clathrate Hydrate Structure
Materials 2016, 9(9), 777; doi:10.3390/ma9090777
Received: 11 July 2016 / Revised: 15 August 2016 / Accepted: 8 September 2016 / Published: 15 September 2016
Cited by 2 | PDF Full-text (5104 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
This paper analyzes the structural, energetic and mechanical properties of carbon dioxide hydrate clathrates calculated using finite cluster and periodic ab initio density-functional theory methodologies. Intermolecular interactions are described by the exchange-hole dipole moment method. The stability, gas saturation energetics, guest–host interactions, cage
[...] Read more.
This paper analyzes the structural, energetic and mechanical properties of carbon dioxide hydrate clathrates calculated using finite cluster and periodic ab initio density-functional theory methodologies. Intermolecular interactions are described by the exchange-hole dipole moment method. The stability, gas saturation energetics, guest–host interactions, cage deformations, vibrational frequencies, and equation of state parameters for the low-pressure sI cubic phase of the CO2@H2O clathrate hydrate are presented. Our results reveal that: (i) the gas saturation process energetically favors complete filling; (ii) carbon dioxide molecules prefer to occupy the larger of the two cages in the sI structure; (iii) blue shifts occur in both the symmetric and antisymmetric stretching frequencies of CO2 upon encapsulation; and (iv) free rotation of guest molecules is restricted to a plane parallel to the hexagonal faces of the large cages. In addition, we calculate the librational frequency of the hindered rotation of the guest molecule in the plane perpendicular to the hexagonal faces. Our calculated spectroscopic data can be used as signatures for the detection of clathrate hydrates in planetary environments. Full article
(This article belongs to the Special Issue Inorganic Clathrate Materials)
Figures

Figure 1

Open AccessArticle Evaluation of the Antimicrobial Activity of Different Antibiotics Enhanced with Silver-Doped Hydroxyapatite Thin Films
Materials 2016, 9(9), 778; doi:10.3390/ma9090778
Received: 4 August 2016 / Revised: 1 September 2016 / Accepted: 8 September 2016 / Published: 16 September 2016
Cited by 5 | PDF Full-text (9686 KB) | HTML Full-text | XML Full-text
Abstract
The inhibitory and antimicrobial effects of silver particles have been known since ancient times. In the last few years, a major health problem has arisen due to pathogenic bacteria resistance to antimicrobial agents. The antibacterial activities of new materials including hydroxyapatite (HAp), silver-doped
[...] Read more.
The inhibitory and antimicrobial effects of silver particles have been known since ancient times. In the last few years, a major health problem has arisen due to pathogenic bacteria resistance to antimicrobial agents. The antibacterial activities of new materials including hydroxyapatite (HAp), silver-doped hydroxyapatite (Ag:HAp) and various types of antibiotics such as tetracycline (T-HAp and T-Ag:HAp) or ciprofloxacin (C-HAp and C-Ag:HAp) have not been studied so far. In this study we reported, for the first time, the preparation and characterization of various thin films based on hydroxyapatite and silver-doped hydroxyapatite combined with tetracycline or ciprofloxacin. The structural and chemical characterization of hydroxyapatite and silver-doped hydroxyapatite thin films has been evaluated by X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR). The morphological studies of the HAp, Ag:HAp, T-HAp, T-Ag:HAp, C-HAp and C-Ag:HAp thin solid films were performed using scanning electron microscopy (SEM). In order to study the chemical composition of the coatings, energy dispersive X-ray analysis (EDX) and glow discharge optical emission spectroscopy (GDOES) measurements have been used, obtaining information on the distribution of the elements throughout the film. These studies have confirmed the purity of the prepared hydroxyapatite and silver-doped hydroxyapatite thin films obtained from composite targets containing Ca10−xAgx(PO4)6(OH)2 with xAg = 0 (HAp) and xAg = 0.2 (Ag:HAp). On the other hand, the major aim of this study was the evaluation of the antibacterial activities of ciprofloxacin and tetracycline in the presence of HAp and Ag:HAp thin layers against Staphylococcus aureus and Escherichia coli strains. The antibacterial activities of ciprofloxacin and tetracycline against Staphylococcus aureus and Escherichia coli test strains increased in the presence of HAp and Ag:HAp thin layers. Full article
(This article belongs to the Special Issue Bioceramics 2016)
Figures

Open AccessArticle Multichromic Polymers Containing Alternating Bi(3-Methoxythiophene) and Triphenylamine Based Units with Para-Protective Substituents
Materials 2016, 9(9), 779; doi:10.3390/ma9090779
Received: 11 August 2016 / Revised: 7 September 2016 / Accepted: 12 September 2016 / Published: 19 September 2016
Cited by 2 | PDF Full-text (11394 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Two novel triphenylamine-based thiophene derivative monomers, 4-cyano-4′,4″-di(4-methoxythiophen-2-yl)triphenylamine and 4-methoxy-4′,4″-di(4-methoxythiophen-2-yl)triphenylamine, were successfully synthesized. The corresponding polymers including poly (4-cyano-4′,4″-di(4-methoxythiophen-2-yl)triphenylamine) and poly (4-methoxy-4′,4″-di(4-methoxythiophen-2-yl)triphenylamine) were electrochemically synthesized and characterized by multiple test method. The electrochemical measurements and spectroelectrochemical analyses revealed that both of the two polymers
[...] Read more.
Two novel triphenylamine-based thiophene derivative monomers, 4-cyano-4′,4″-di(4-methoxythiophen-2-yl)triphenylamine and 4-methoxy-4′,4″-di(4-methoxythiophen-2-yl)triphenylamine, were successfully synthesized. The corresponding polymers including poly (4-cyano-4′,4″-di(4-methoxythiophen-2-yl)triphenylamine) and poly (4-methoxy-4′,4″-di(4-methoxythiophen-2-yl)triphenylamine) were electrochemically synthesized and characterized by multiple test method. The electrochemical measurements and spectroelectrochemical analyses revealed that both of the two polymers had quasi-reversible redox behavior and multi-electrochromic properties. The two polymer films showed reversible electrochemical oxidation, excellent optical contrasts in NIR region (62% at 1070 nm for the first polymer, and 86% at 1255 nm for the second polymer), satisfactory coloration efficiencies and fast switching times. The research on the application of the as prepared polymer in the fabrication of electrochromic device was also conducted, employing PCMTPA or PMMTPA as the anodically coloring materials. Full article
(This article belongs to the Section Structure Analysis and Characterization)
Figures

Open AccessArticle Deformation Behavior of Recycled Concrete Aggregate during Cyclic and Dynamic Loading Laboratory Tests
Materials 2016, 9(9), 780; doi:10.3390/ma9090780
Received: 29 July 2016 / Revised: 6 September 2016 / Accepted: 8 September 2016 / Published: 20 September 2016
Cited by 2 | PDF Full-text (5470 KB) | HTML Full-text | XML Full-text
Abstract
Recycled concrete aggregate (RCA) is a relatively new construction material, whose applications can replace natural aggregates. To do so, extensive studies on its mechanical behavior and deformation characteristics are still necessary. RCA is currently used as a subbase material in the construction of
[...] Read more.
Recycled concrete aggregate (RCA) is a relatively new construction material, whose applications can replace natural aggregates. To do so, extensive studies on its mechanical behavior and deformation characteristics are still necessary. RCA is currently used as a subbase material in the construction of roads, which are subject to high settlements due to traffic loading. The deformation characteristics of RCA must, therefore, be established to find the possible fatigue and damage behavior for this new material. In this article, a series of triaxial cyclic loading and resonant column tests is used to characterize fatigue in RCA as a function of applied deviator stress after long-term cyclic loading. A description of the shakedown phenomenon occurring in the RCA and calculations of its resilient modulus (Mr) as a function of fatigue are also presented. Test result analysis with the stress-life method on the Wohler S-N diagram shows the RCA behavior in accordance with the Basquin law. Full article
Figures

Figure 1

Open AccessArticle Monitoring Poisson’s Ratio Degradation of FRP Composites under Fatigue Loading Using Biaxially Embedded FBG Sensors
Materials 2016, 9(9), 781; doi:10.3390/ma9090781
Received: 20 May 2016 / Revised: 27 August 2016 / Accepted: 3 September 2016 / Published: 19 September 2016
Cited by 1 | PDF Full-text (3865 KB) | HTML Full-text | XML Full-text
Abstract
The significance of strain measurement is obvious for the analysis of Fiber-Reinforced Polymer (FRP) composites. Conventional strain measurement methods are sufficient for static testing in general. Nevertheless, if the requirements exceed the capabilities of these conventional methods, more sophisticated techniques are necessary to
[...] Read more.
The significance of strain measurement is obvious for the analysis of Fiber-Reinforced Polymer (FRP) composites. Conventional strain measurement methods are sufficient for static testing in general. Nevertheless, if the requirements exceed the capabilities of these conventional methods, more sophisticated techniques are necessary to obtain strain data. Fiber Bragg Grating (FBG) sensors have many advantages for strain measurement over conventional ones. Thus, the present paper suggests a novel method for biaxial strain measurement using embedded FBG sensors during the fatigue testing of FRP composites. Poisson’s ratio and its reduction were monitored for each cyclic loading by using embedded FBG sensors for a given specimen and correlated with the fatigue stages determined based on the variations of the applied fatigue loading and temperature due to the autogenous heating to predict an oncoming failure of the continuous fiber-reinforced epoxy matrix composite specimens under fatigue loading. The results show that FBG sensor technology has a remarkable potential for monitoring the evolution of Poisson’s ratio on a cycle-by-cycle basis, which can reliably be used towards tracking the fatigue stages of composite for structural health monitoring purposes. Full article
(This article belongs to the Special Issue Advances in Structural Health Monitoring for Aerospace Structures)
Figures

Figure 1

Open AccessArticle Three-Dimensional Network Model for Coupling of Fracture and Mass Transport in Quasi-Brittle Geomaterials
Materials 2016, 9(9), 782; doi:10.3390/ma9090782
Received: 9 August 2016 / Revised: 12 September 2016 / Accepted: 14 September 2016 / Published: 19 September 2016
Cited by 5 | PDF Full-text (1074 KB) | HTML Full-text | XML Full-text
Abstract
Dual three-dimensional networks of structural and transport elements were combined to model the effect of fracture on mass transport in quasi-brittle geomaterials. Element connectivity of the structural network, representing elasticity and fracture, was defined by the Delaunay tessellation of a random set of
[...] Read more.
Dual three-dimensional networks of structural and transport elements were combined to model the effect of fracture on mass transport in quasi-brittle geomaterials. Element connectivity of the structural network, representing elasticity and fracture, was defined by the Delaunay tessellation of a random set of points. The connectivity of transport elements within the transport network was defined by the Voronoi tessellation of the same set of points. A new discretisation strategy for domain boundaries was developed to apply boundary conditions for the coupled analyses. The properties of transport elements were chosen to evolve with the crack opening values of neighbouring structural elements. Through benchmark comparisons involving non-stationary transport and fracture, the proposed dual network approach was shown to be objective with respect to element size and orientation. Full article
(This article belongs to the Special Issue Numerical Analysis of Concrete using Discrete Elements)
Figures

Figure 1

Open AccessArticle Simple Synthesis of Molybdenum Disulfide/Reduced Graphene Oxide Composite Hollow Microspheres as Supercapacitor Electrode Material
Materials 2016, 9(9), 783; doi:10.3390/ma9090783
Received: 22 August 2016 / Revised: 8 September 2016 / Accepted: 12 September 2016 / Published: 20 September 2016
Cited by 7 | PDF Full-text (3086 KB) | HTML Full-text | XML Full-text
Abstract
MoS2/RGO composite hollow microspheres were hydrothermally synthesized by using SiO2/GO microspheres as a template, which were obtained via the sonication-assisted interfacial self-assembly of tiny GO sheets on positively charged SiO2 microspheres. The structure, morphology, phase, and chemical composition
[...] Read more.
MoS2/RGO composite hollow microspheres were hydrothermally synthesized by using SiO2/GO microspheres as a template, which were obtained via the sonication-assisted interfacial self-assembly of tiny GO sheets on positively charged SiO2 microspheres. The structure, morphology, phase, and chemical composition of MoS2/RGO hollow microspheres were systematically investigated by a series of techniques such as FE-SEM, TEM, XRD, TGA, BET, and Raman characterizations, meanwhile, their electrochemical properties were carefully evaluated by CV, GCD, and EIS measurements. It was found that MoS2/RGO hollow microspheres possessed unique porous hollow architecture with high-level hierarchy and large specific surface area up to 63.7 m2·g−1. When used as supercapacitor electrode material, MoS2/RGO hollow microspheres delivered a maximum specific capacitance of 218.1 F·g−1 at the current density of 1 A·g−1, which was much higher than that of contrastive bare MoS2 microspheres developed in the present work and most of other reported MoS2-based materials. The enhancement of supercapacitive behaviors of MoS2/RGO hollow microspheres was likely due to the improved conductivity together with their distinct structure and morphology, which not only promoted the charge transport but also facilitated the electrolyte diffusion. Moreover, MoS2/RGO hollow microsphere electrode displayed satisfactory long-term stability with 91.8% retention of the initial capacitance after 1000 charge/discharge cycles at the current density of 3 A·g−1, showing excellent application potential. Full article
(This article belongs to the Section Energy Materials)
Figures

Figure 1

Open AccessArticle Novel Resorbable and Osteoconductive Calcium Silicophosphate Scaffold Induced Bone Formation
Materials 2016, 9(9), 785; doi:10.3390/ma9090785
Received: 25 July 2016 / Revised: 6 September 2016 / Accepted: 12 September 2016 / Published: 20 September 2016
Cited by 8 | PDF Full-text (11470 KB) | HTML Full-text | XML Full-text
Abstract
This aim of this research was to develop a novel ceramic scaffold to evaluate the response of bone after ceramic implantation in New Zealand (NZ) rabbits. Ceramics were prepared by the polymer replication method and inserted into NZ rabbits. Macroporous scaffolds with interconnected
[...] Read more.
This aim of this research was to develop a novel ceramic scaffold to evaluate the response of bone after ceramic implantation in New Zealand (NZ) rabbits. Ceramics were prepared by the polymer replication method and inserted into NZ rabbits. Macroporous scaffolds with interconnected round-shaped pores (0.5–1.5 mm = were prepared). The scaffold acted as a physical support where cells with osteoblastic capability were found to migrate, develop processes, and newly immature and mature bone tissue colonized on the surface (initially) and in the material’s interior. The new ceramic induced about 62.18% ± 2.28% of new bone and almost complete degradation after six healing months. An elemental analysis showed that the gradual diffusion of Ca and Si ions from scaffolds into newly formed bone formed part of the biomaterial’s resorption process. Histological and radiological studies demonstrated that this porous ceramic scaffold showed biocompatibility and excellent osteointegration and osteoinductive capacity, with no interposition of fibrous tissue between the implanted material and the hematopoietic bone marrow interphase, nor any immune response after six months of implantation. No histological changes were observed in the various organs studied (para-aortic lymph nodes, liver, kidney and lung) as a result of degradation products being released. Full article
(This article belongs to the Special Issue Smart Biomaterials and Biointerfaces)
Figures

Figure 1

Open AccessArticle Imperfection Sensitivity of Nonlinear Vibration of Curved Single-Walled Carbon Nanotubes Based on Nonlocal Timoshenko Beam Theory
Materials 2016, 9(9), 786; doi:10.3390/ma9090786
Received: 2 August 2016 / Revised: 29 August 2016 / Accepted: 6 September 2016 / Published: 21 September 2016
Cited by 1 | PDF Full-text (6575 KB) | HTML Full-text | XML Full-text
Abstract
Imperfection sensitivity of large amplitude vibration of curved single-walled carbon nanotubes (SWCNTs) is considered in this study. The SWCNT is modeled as a Timoshenko nano-beam and its curved shape is included as an initial geometric imperfection term in the displacement field. Geometric nonlinearities
[...] Read more.
Imperfection sensitivity of large amplitude vibration of curved single-walled carbon nanotubes (SWCNTs) is considered in this study. The SWCNT is modeled as a Timoshenko nano-beam and its curved shape is included as an initial geometric imperfection term in the displacement field. Geometric nonlinearities of von Kármán type and nonlocal elasticity theory of Eringen are employed to derive governing equations of motion. Spatial discretization of governing equations and associated boundary conditions is performed using differential quadrature (DQ) method and the corresponding nonlinear eigenvalue problem is iteratively solved. Effects of amplitude and location of the geometric imperfection, and the nonlocal small-scale parameter on the nonlinear frequency for various boundary conditions are investigated. The results show that the geometric imperfection and non-locality play a significant role in the nonlinear vibration characteristics of curved SWCNTs. Full article
(This article belongs to the Section Structure Analysis and Characterization)
Figures

Open AccessArticle Elastic Modulus of the Alkali-Silica Reaction Rim in a Simplified Calcium-Alkali-Silicate System Determined by Nano-Indentation
Materials 2016, 9(9), 787; doi:10.3390/ma9090787
Received: 26 July 2016 / Revised: 31 August 2016 / Accepted: 12 September 2016 / Published: 20 September 2016
Cited by 3 | PDF Full-text (6229 KB) | HTML Full-text | XML Full-text
Abstract
This work aims at providing a better understanding of the mechanical properties of the reaction rim in the alkali-silica reaction. The elastic modulus of the calcium alkali silicate constituting the reaction rim, which is formed at the interface between alkali silicate and Ca(OH)
[...] Read more.
This work aims at providing a better understanding of the mechanical properties of the reaction rim in the alkali-silica reaction. The elastic modulus of the calcium alkali silicate constituting the reaction rim, which is formed at the interface between alkali silicate and Ca(OH)2 in a chemically-idealized system of the alkali-silica reaction, was studied using nano-indentation. In addition, the corresponding calcium to silica mole ratio of the calcium alkali silicate was investigated. The results show that the elastic modulus of the calcium alkali silicate formed at the interface increased with the increase of the calcium to silica mole ratio and vice versa. Furthermore, the more calcium that was available for interaction with alkali silicate to form calcium alkali silicate, the higher the calcium to silica mole ratio and, consequently, the higher the elastic modulus of the formed calcium alkali silicate. This work provides illustrative evidence from a mechanical point of view on how the occurrence of cracks due to the alkali-silica reaction (ASR) is linked to the formation of the reaction rim. It has to be highlighted, however, that the simplified calcium-alkali-silicate system in this study is far from the real condition in concrete. Full article
Figures

Figure 1

Open AccessArticle Characteristics of Ceramic Fiber Modified Asphalt Mortar
Materials 2016, 9(9), 788; doi:10.3390/ma9090788
Received: 5 June 2016 / Revised: 16 August 2016 / Accepted: 12 September 2016 / Published: 21 September 2016
Cited by 1 | PDF Full-text (4263 KB) | HTML Full-text | XML Full-text
Abstract
Ceramic fiber, with a major composition of Al2O3 and SiO2, has advantages of stability at relatively high temperature, big specific surface area and resistance to external mechanical vibration. It has the potential contribution of improving the rutting resistance
[...] Read more.
Ceramic fiber, with a major composition of Al2O3 and SiO2, has advantages of stability at relatively high temperature, big specific surface area and resistance to external mechanical vibration. It has the potential contribution of improving the rutting resistance and temperature sensitivity of modified asphalt binder by proper modification design. In this research, ceramic fiber was introduced into both pen 60/80 and pen 80/100 asphalt binder by different weight ratios. An asphalt penetration test, softening point test, ductility test and dynamic viscoelastic behavior were conducted to characterize and predict the ceramic fiber modified asphalt mortar (CFAM). Research results indicated that the ceramic fiber has a great effect on reinforcement of asphalt, which makes the asphalt stiffer so that the asphalt can only undertake less strain under the same stress. The heat insulation effect of the ceramic fiber will improve the temperature stability. Complex modulus and phase angle results indicate that the ceramic fiber can significantly enhance the high temperature resistance of soft binder. Full article
Figures

Figure 1

Open AccessArticle Photocatalytic, Antimicrobial and Biocompatibility Features of Cotton Knit Coated with Fe-N-Doped Titanium Dioxide Nanoparticles
Materials 2016, 9(9), 789; doi:10.3390/ma9090789
Received: 1 August 2016 / Revised: 29 August 2016 / Accepted: 1 September 2016 / Published: 21 September 2016
Cited by 5 | PDF Full-text (3664 KB) | HTML Full-text | XML Full-text
Abstract
Our research was focused on the evaluation of the photocatalytic and antimicrobial properties, as well as biocompatibility of cotton fabrics coated with fresh and reused dispersions of nanoscaled TiO2-1% Fe-N particles prepared by the hydrothermal method and post-annealed at 400 °C.
[...] Read more.
Our research was focused on the evaluation of the photocatalytic and antimicrobial properties, as well as biocompatibility of cotton fabrics coated with fresh and reused dispersions of nanoscaled TiO2-1% Fe-N particles prepared by the hydrothermal method and post-annealed at 400 °C. The powders were characterized by X-ray diffraction (XRD), Mössbauer spectroscopy and X-ray photoelectron spectroscopy. The textiles coated with doped TiO2 were characterized by scanning electron microscopy and energy dispersive X-ray analyses, and their photocatalytic effect by trichromatic coordinates of the materials stained with methylene blue and coffee and exposed to UV, visible and solar light. The resulting doped TiO2 consists of a mixture of prevailing anatase phase and a small amount (~15%–20%) of brookite, containing Fe3+ and nitrogen. By reusing dispersions of TiO2-1% Fe-N, high amounts of photocatalysts were deposited on the fabrics, and the photocatalytic activity was improved, especially under visible light. The treated fabrics exhibited specific antimicrobial features, which were dependent on their composition, microbial strain and incubation time. The in vitro biocompatibility evaluation on CCD-1070Sk dermal fibroblasts confirmed the absence of cytotoxicity after short-term exposure. These results highlight the potential of TiO2-1% Fe-N nanoparticles for further use in the development of innovative self-cleaning and antimicrobial photocatalytic cotton textiles. However, further studies are required in order to assess the long-term skin exposure effects and the possible particle release due to wearing. Full article
(This article belongs to the Special Issue Materials for Hard and Soft Tissue Engineering: Novel Approaches)
Figures

Figure 1

Open AccessArticle A Multi-Level Decision Fusion Strategy for Condition Based Maintenance of Composite Structures
Materials 2016, 9(9), 790; doi:10.3390/ma9090790
Received: 11 August 2016 / Revised: 5 September 2016 / Accepted: 13 September 2016 / Published: 21 September 2016
Cited by 5 | PDF Full-text (5656 KB) | HTML Full-text | XML Full-text
Abstract
In this work, a multi-level decision fusion strategy is proposed which weighs the Value of Information (VoI) against the intended functions of a Structural Health Monitoring (SHM) system. This paper presents a multi-level approach for three different maintenance strategies in which the performance
[...] Read more.
In this work, a multi-level decision fusion strategy is proposed which weighs the Value of Information (VoI) against the intended functions of a Structural Health Monitoring (SHM) system. This paper presents a multi-level approach for three different maintenance strategies in which the performance of the SHM systems is evaluated against its intended functions. Level 1 diagnosis results in damage existence with minimum sensors covering a large area by finding the maximum energy difference for the guided waves propagating in pristine structure and the post-impact state; Level 2 diagnosis provides damage detection and approximate localization using an approach based on Electro-Mechanical Impedance (EMI) measures, while Level 3 characterizes damage (exact location and size) in addition to its detection by utilising a Weighted Energy Arrival Method (WEAM). The proposed multi-level strategy is verified and validated experimentally by detection of Barely Visible Impact Damage (BVID) on a curved composite fuselage panel. Full article
(This article belongs to the Special Issue Advances in Structural Health Monitoring for Aerospace Structures)
Figures

Figure 1

Open AccessArticle Pickering Particles Prepared from Food Waste
Materials 2016, 9(9), 791; doi:10.3390/ma9090791
Received: 9 August 2016 / Revised: 12 September 2016 / Accepted: 14 September 2016 / Published: 21 September 2016
Cited by 4 | PDF Full-text (5681 KB) | HTML Full-text | XML Full-text
Abstract
In this paper, we demonstrate the functionality and functionalisation of waste particles as an emulsifier for oil-in-water (o/w) and water-in-oil (w/o) emulsions. Ground coffee waste was chosen as a candidate waste material due to its naturally high content of lignin, a chemical component
[...] Read more.
In this paper, we demonstrate the functionality and functionalisation of waste particles as an emulsifier for oil-in-water (o/w) and water-in-oil (w/o) emulsions. Ground coffee waste was chosen as a candidate waste material due to its naturally high content of lignin, a chemical component imparting emulsifying ability. The waste coffee particles readily stabilised o/w emulsions and following hydrothermal treatment adapted from the bioenergy field they also stabilised w/o emulsions. The hydrothermal treatment relocated the lignin component of the cell walls within the coffee particles onto the particle surface thereby increasing the surface hydrophobicity of the particles as demonstrated by an emulsion assay. Emulsion droplet sizes were comparable to those found in processed foods in the case of hydrophilic waste coffee particles stabilizing o/w emulsions. These emulsions were stable against coalescence for at least 12 weeks, flocculated but stable against coalescence in shear and stable to pasteurisation conditions (10 min at 80 °C). Emulsion droplet size was also insensitive to pH of the aqueous phase during preparation (pH 3–pH 9). Stable against coalescence, the water droplets in w/o emulsions prepared with hydrothermally treated waste coffee particles were considerably larger and microscopic examination showed evidence of arrested coalescence indicative of particle jamming at the surface of the emulsion droplets. Refinement of the hydrothermal treatment and broadening out to other lignin-rich plant or plant based food waste material are promising routes to bring closer the development of commercially relevant lignin based food Pickering particles applicable to emulsion based processed foods ranging from fat continuous spreads and fillings to salad dressings. Full article
(This article belongs to the Special Issue Pickering Emulsion and Derived Materials) Printed Edition available
Figures

Figure 1

Open AccessArticle The Effect of 4-Octyldecyloxybenzoic Acid on Liquid-Crystalline Polyurethane Composites with Triple-Shape Memory and Self-Healing Properties
Materials 2016, 9(9), 792; doi:10.3390/ma9090792
Received: 16 August 2016 / Revised: 8 September 2016 / Accepted: 12 September 2016 / Published: 21 September 2016
Cited by 2 | PDF Full-text (10122 KB) | HTML Full-text | XML Full-text
Abstract
To better understand shape memory materials and self-healing materials, a new series of liquid-crystalline shape memory polyurethane (LC-SMPU) composites, named SMPU-OOBAm, were successfully prepared by incorporating 4-octyldecyloxybenzoic acid (OOBA) into the PEG-based SMPU. The effect of OOBA on the structure, morphology, and properties
[...] Read more.
To better understand shape memory materials and self-healing materials, a new series of liquid-crystalline shape memory polyurethane (LC-SMPU) composites, named SMPU-OOBAm, were successfully prepared by incorporating 4-octyldecyloxybenzoic acid (OOBA) into the PEG-based SMPU. The effect of OOBA on the structure, morphology, and properties of the material has been carefully investigated. The results demonstrate that SMPU-OOBAm has liquid crystalline properties, triple-shape memory properties, and self-healing properties. The incorporated OOBA promotes the crystallizability of both soft and hard segments of SMPU, and the crystallization rate of the hard segment of SMPU decreases when the OOBA-content increases. Additionally, the SMPU-OOBAm forms a two-phase separated structure (SMPU phase and OOBA phase), and it shows two-step modulus changes upon heating. Therefore, the SMPU-OOBAm exhibits triple-shape memory behavior, and the shape recovery ratio decreases with an increase in the OOBA content. Finally, SMPU-OOBAm exhibits self-healing properties. The new mechanism can be ascribed to the heating-induced “bleeding” of OOBA in the liquid crystalline state and the subsequent re-crystallization upon cooling. This successful combination of liquid crystalline properties, triple-shape memory properties, and self-healing properties make the SMPU-OOBAm composites ideal for many promising applications in smart optical devices, smart electronic devices, and smart sensors. Full article
(This article belongs to the Section Advanced Composites)
Figures