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Materials, Volume 11, Issue 5 (May 2018)

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Cover Story (view full-size image) The synergistic combination of the excellent bioactivity of mesoporous bioactive glasses (MBGs) and [...] Read more.
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Open AccessArticle A Feasible One-Step Synthesis of Hierarchical Zeolite Beta with Uniform Nanocrystals via CTAB
Materials 2018, 11(5), 651; https://doi.org/10.3390/ma11050651
Received: 26 March 2018 / Revised: 17 April 2018 / Accepted: 20 April 2018 / Published: 24 April 2018
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Abstract
A hierarchical zeolite Beta has been prepared by a feasible one-pot and one-step method, which is suitable for application in industrial production. The synthesis is a simple hydrothermal process with low-cost raw materials, without adding alcohol or adding seeds, and without aging, recrystallization,
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A hierarchical zeolite Beta has been prepared by a feasible one-pot and one-step method, which is suitable for application in industrial production. The synthesis is a simple hydrothermal process with low-cost raw materials, without adding alcohol or adding seeds, and without aging, recrystallization, and other complex steps. The hierarchical zeolite Beta is a uniform nanocrystal (20–50 nm) aggregation with high external surface area (300 m2/g) and mesoporous volume (0.50 cm3/g), with the mesoporous structure composed of intercrystal and intracrystal pores. As an acid catalyst in benzylation of naphthalene with benzyl chloride, the hierarchical zeolite Beta has shown high activity in the bulky molecule reaction due to its introduction of mesostructure. Full article
(This article belongs to the Special Issue Mesoporous Silica Catalysts)
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Open AccessArticle Properties of Basil and Lavender Essential Oils Adsorbed on the Surface of Hydroxyapatite
Materials 2018, 11(5), 652; https://doi.org/10.3390/ma11050652
Received: 30 March 2018 / Revised: 16 April 2018 / Accepted: 18 April 2018 / Published: 24 April 2018
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Abstract
The research conducted in this study presented for the first time results of physico-chemical properties and in vitro antimicrobial activity of hydroxyapatite plant essential oil against Gram-positive bacteria (methicillin-resistant Staphylococcus aureus (MRSA) and S. aureus 0364) and Gram-negative bacteria (Escherichia coli ATCC
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The research conducted in this study presented for the first time results of physico-chemical properties and in vitro antimicrobial activity of hydroxyapatite plant essential oil against Gram-positive bacteria (methicillin-resistant Staphylococcus aureus (MRSA) and S. aureus 0364) and Gram-negative bacteria (Escherichia coli ATCC 25922). The samples were studied by scanning electron microscopy (SEM) and Fourier transform infrared (FTIR) spectroscopy to determine the morphology and structure of the nanocomposites of hydroxyapatite coated with basil (HAp-B) and lavender (HAp-L) essential oils (EOs). The values of the BET specific surface area (SBET), total pore volume (VP) and pore size (DP) were determined. The results for the physico-chemical properties of HAp-L and HAp-B revealed that lavender EOs were well adsorbed on the surface of hydroxyapatite, whereas basil EOs showed a poor adsorption on the surface of hydroxyapatite. We found that the lavender EOs hydroxyapatite (HAp-L) exhibited a very good inhibitory growth activity. The value of the minimum inhibitory concentration (MIC) related to growth bacteria was 0.039 mg/mL for MRSA, 0.02 mg/mL for S. aureus and 0.039 mg/mL E. coli ATCC 25922. The basil EO hydroxyapatite (HAp-B) showed poor inhibition of bacterial cell growth. The MIC value was 0.625 mg/mL for the HAp-B sample in the presence of the MRSA bacteria, 0.313 mg/mL in the presence of S. aureus and 0.078 mg/mL for E. coli ATCC 25922. Full article
(This article belongs to the Special Issue Nanomaterials for Biomedical Applications)
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Open AccessArticle Catalytic Oxidation of Soot on a Novel Active Ca-Co Dually-Doped Lanthanum Tin Pyrochlore Oxide
Materials 2018, 11(5), 653; https://doi.org/10.3390/ma11050653
Received: 7 March 2018 / Revised: 3 April 2018 / Accepted: 19 April 2018 / Published: 24 April 2018
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Abstract
A novel active Ca-Co dually-doping pyrochlore oxide La2−xCaxSn2−yCoyO7 catalyst was synthesized by the sol-gel method for catalytic oxidation of soot particulates. The microstructure, atomic valence, reduction, and adsorption performance were investigated by X-ray powder
[...] Read more.
A novel active Ca-Co dually-doping pyrochlore oxide La2−xCaxSn2−yCoyO7 catalyst was synthesized by the sol-gel method for catalytic oxidation of soot particulates. The microstructure, atomic valence, reduction, and adsorption performance were investigated by X-ray powder diffraction (XRD), scanning electron microscope (SEM), Fourier-transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), H2-TPR (temperature-programmed reduction), and in situ diffuse reflection infrared Fourier transformed (DRIFTS) techniques. Temperature programmed oxidation (TPO) tests were performed with the mixture of soot-catalyst under tight contact conditions to evaluate the catalytic activity for soot combustion. Synergetic effect between Ca and Co improved the structure and redox properties of the solids, increased the surface oxygen vacancies, and provided a suitable electropositivity for oxide, directly resulting in the decreased ignition temperature for catalyzed soot oxidation as low as 317 °C. The presence of NO in O2 further promoted soot oxidation over the catalysts with the ignition temperature decreased to about 300 °C. The DRIFTS results reveal that decomposition of less stable surface nitrites may account for NO2 formation in the ignition period of soot combustion, which thus participate in the auxiliary combustion process. Full article
(This article belongs to the Special Issue Supported Materials for Catalytic Application)
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Open AccessArticle Theoretical Investigations of the Hexagonal Germanium Carbonitride
Materials 2018, 11(5), 655; https://doi.org/10.3390/ma11050655
Received: 21 March 2018 / Revised: 18 April 2018 / Accepted: 19 April 2018 / Published: 24 April 2018
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Abstract
The structural, mechanical, elastic anisotropic, and electronic properties of hexagonal germanium carbonitride (h-GeCN) are systematically investigated using the first-principle calculations method with the ultrasoft pseudopotential scheme in the frame of generalized gradient approximation in the present work. The h-GeCN are
[...] Read more.
The structural, mechanical, elastic anisotropic, and electronic properties of hexagonal germanium carbonitride (h-GeCN) are systematically investigated using the first-principle calculations method with the ultrasoft pseudopotential scheme in the frame of generalized gradient approximation in the present work. The h-GeCN are mechanically and dynamically stable, as proved by the elastic constants and phonon spectra, respectively. The h-GeCN is brittle because the ratio B/G and Poisson’s ratio v of the h-GeCN are less than 1.75 and 0.26, respectively. For h-GeCN, from brittleness to ductility, the transformation pressures are 5.56 GPa and 5.63 GPa for B/G and Poisson’s ratio v, respectively. The h-GeCN exhibits the greater elastic anisotropy in Young’s modulus and the sound velocities. In addition, the calculated band structure of h-GeCN reveals that there is no band gap for h-GeCN with the HSE06 hybrid functional, so the h-GeCN is metallic. Full article
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Open AccessArticle Microstructure and Deformation Response of TRIP-Steel Syntactic Foams to Quasi-Static and Dynamic Compressive Loads
Materials 2018, 11(5), 656; https://doi.org/10.3390/ma11050656
Received: 20 March 2018 / Revised: 18 April 2018 / Accepted: 19 April 2018 / Published: 24 April 2018
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Abstract
The implementation of hollow S60HS glass microspheres and Fillite 106 cenospheres in a martensitically transformable AISI 304L stainless steel matrix was realized by means of metal injection molding of feedstock with varying fractions of the filler material. The so-called TRIP-steel syntactic foams were
[...] Read more.
The implementation of hollow S60HS glass microspheres and Fillite 106 cenospheres in a martensitically transformable AISI 304L stainless steel matrix was realized by means of metal injection molding of feedstock with varying fractions of the filler material. The so-called TRIP-steel syntactic foams were studied with respect to their behavior under quasi-static compression and dynamic impact loading. The interplay between matrix material behavior and foam structure was discussed in relation to the findings of micro-structural investigations, electron back scatter diffraction EBSD phase analyses and magnetic measurements. During processing, the cenospheres remained relatively stable retaining their shape while the glass microspheres underwent disintegration associated with the formation of pre-cracked irregular inclusions. Consequently, the AISI 304L/Fillite 106 syntactic foams exhibited a higher compression stress level and energy absorption capability as compared to the S60HS-containing variants. The α -martensite kinetic of the steel matrix was significantly influenced by material composition, strain rate and arising deformation temperature. The highest ferromagnetic α -martensite phase fraction was detected for the AISI 304L/S60HS batches and the lowest for the TRIP-steel bulk material. Quasi-adiabatic sample heating, a gradual decrease in strain rate and an enhanced degree of damage controlled the mechanical deformation response of the studied syntactic foams under dynamic impact loading. Full article
(This article belongs to the Special Issue Advanced Materials for Transport Applications)
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Open AccessArticle EPDM Rubber Modified by Nitrogen Plasma Immersion Ion Implantation
Materials 2018, 11(5), 657; https://doi.org/10.3390/ma11050657
Received: 30 March 2018 / Revised: 21 April 2018 / Accepted: 22 April 2018 / Published: 24 April 2018
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Abstract
Ethylene-propylene diene monomer rubber (EPDM) was treated by plasma immersion ion implantation (PIII) with nitrogen ions of 20 keV energy and fluence from 1013 to 1016 ions/cm2. The Fourier-transform infrared attenuated total reflection spectra, atomic force microscopy and optical
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Ethylene-propylene diene monomer rubber (EPDM) was treated by plasma immersion ion implantation (PIII) with nitrogen ions of 20 keV energy and fluence from 1013 to 1016 ions/cm2. The Fourier-transform infrared attenuated total reflection spectra, atomic force microscopy and optical microscopy showed significant structure changes of the surface. The analysis of an interface of PIII treated EPDM rubber with polyurethane binder showed a cohesive character of the adhesion joint fracture at the presence of solvent and interpreted as covalent bond network formation between the PIII treated rubber and the adhesive. Full article
(This article belongs to the Special Issue Energetic Materials and Processes)
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Open AccessArticle Application of Recycled Ceramic Aggregates for the Production of Mineral-Asphalt Mixtures
Materials 2018, 11(5), 658; https://doi.org/10.3390/ma11050658
Received: 30 March 2018 / Revised: 18 April 2018 / Accepted: 19 April 2018 / Published: 24 April 2018
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Abstract
This paper describes a method of designing and producing innovative mineral–asphalt mixtures, which utilize waste aggregate from the recycling of sanitary ceramics. The work presents the basic properties of the ceramic material, the investigation concerning the microstructure of the aggregate obtained from the
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This paper describes a method of designing and producing innovative mineral–asphalt mixtures, which utilize waste aggregate from the recycling of sanitary ceramics. The work presents the basic properties of the ceramic material, the investigation concerning the microstructure of the aggregate obtained from the grinding of waste, and a comparison with the images obtained for the aggregates usually employed in mineral–asphalt mixtures. The mixtures were designed for the application in the wearing course. Four series of mixtures were prepared. In the first and second, the ceramic aggregate constituted a partial substitute for dolomite, whereas in the third, we substituted granodiorite, and the fourth series contained only dolomite. The mixtures were examined for the content of soluble binder, the bulk density of samples, the presence of voids, the space filled with binder, and the susceptibility to water and frost corrosion. The obtained results were compared with the standard requirements. The microstructure as well as the contact zone in the considered mineral–asphalt mixtures are presented based on research conducted by means of a scanning electron microscope (SEM). Full article
(This article belongs to the Special Issue Environment-Friendly Construction Materials)
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Open AccessArticle Antibacterial Effects of Magnetically-Controlled Ag/Fe3O4 Nanoparticles
Materials 2018, 11(5), 659; https://doi.org/10.3390/ma11050659
Received: 11 April 2018 / Revised: 21 April 2018 / Accepted: 23 April 2018 / Published: 24 April 2018
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Abstract
This paper presents the use of a magnetic manipulation device to remotely control the movement of Ag/Fe3O4 nanoparticles (NPs) for enhancing the antibacterial effect of Ag particles in aqueous suspensions containing Escherichia coli (E. coli). The Ag/Fe3
[...] Read more.
This paper presents the use of a magnetic manipulation device to remotely control the movement of Ag/Fe3O4 nanoparticles (NPs) for enhancing the antibacterial effect of Ag particles in aqueous suspensions containing Escherichia coli (E. coli). The Ag/Fe3O4 magnetic NPs were prepared by co-precipitation method where the Ag particles are simultaneously synthesized with the Fe3O4 particles to form Ag and Fe3O4 nanocomposite materials. The manipulation system utilized a homogeneous rotating magnetic field to carry out magnetic stirring of NPs in the petri dishes containing bacterial suspensions. The optimum magnetron parameters and best antibacterial effects were implemented with six different concentrations from 0.6 wt % to 6.6 wt % of the NPs at driving frequencies from 50 rpm to 200 rpm for 3 min. The highest antibacterial effect of 99.4% was achieved at 5.4 wt % of NPs and the driving frequency of 100 rpm. A time-dependent antibacterial effect in 0.1 wt % of Ag/Fe3O4 was also observed. The results indicate that the use of specific rotating magnetic fields to manipulate Ag/Fe3O4 magnetic NPs can significantly improve the antibacterial efficacy. Due to the good biocompatibility of the Ag NPs, the presented technique can be applied to clean water resources in the future. Full article
(This article belongs to the Special Issue Selected Papers from IMETI2016)
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Open AccessFeature PaperArticle Nanoscale Topographical Characterization of Orbital Implant Materials
Materials 2018, 11(5), 660; https://doi.org/10.3390/ma11050660
Received: 31 March 2018 / Revised: 14 April 2018 / Accepted: 23 April 2018 / Published: 24 April 2018
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Abstract
The search for an ideal orbital implant is still ongoing in the field of ocular biomaterials. Major limitations of currently-available porous implants include the high cost along with a non-negligible risk of exposure and postoperative infection due to conjunctival abrasion. In the effort
[...] Read more.
The search for an ideal orbital implant is still ongoing in the field of ocular biomaterials. Major limitations of currently-available porous implants include the high cost along with a non-negligible risk of exposure and postoperative infection due to conjunctival abrasion. In the effort to develop better alternatives to the existing devices, two types of new glass-ceramic porous implants were fabricated by sponge replication, which is a relatively inexpensive method. Then, they were characterized by direct three-dimensional (3D) contact probe mapping in real space by means of atomic force microscopy in order to assess their surface micro- and nano-features, which were quantitatively compared to those of the most commonly-used orbital implants. These silicate glass-ceramic materials exhibit a surface roughness in the range of a few hundred nanometers (Sq within 500–700 nm) and topographical features comparable to those of clinically-used “gold-standard” alumina and polyethylene porous orbital implants. However, it was noted that both experimental and commercial non-porous implants were significantly smoother than all the porous ones. The results achieved in this work reveal that these porous glass-ceramic materials show promise for the intended application and encourage further investigation of their clinical suitability. Full article
(This article belongs to the Special Issue State-of-the-Art Materials Science in Italy 2017)
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Open AccessArticle Low-Cycle Fatigue Behavior of 10CrNi3MoV High Strength Steel and Its Undermatched Welds
Materials 2018, 11(5), 661; https://doi.org/10.3390/ma11050661
Received: 30 March 2018 / Revised: 16 April 2018 / Accepted: 23 April 2018 / Published: 24 April 2018
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Abstract
The use of high strength steel allows the design of lighter, more slender and simpler structures due to high strength and favorable ductility. Nevertheless, the increase of yield strength does not guarantee the corresponding improvement of fatigue resistance, which becomes a major concern
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The use of high strength steel allows the design of lighter, more slender and simpler structures due to high strength and favorable ductility. Nevertheless, the increase of yield strength does not guarantee the corresponding improvement of fatigue resistance, which becomes a major concern for engineering structure design, especially for the welded joints. The paper presents a comparison of the low cycle fatigue behaviors between 10CrNi3MoV high strength steel and its undermatched weldments. Uniaxial tension tests, Push-pull, strain-controlled fatigue tests were conducted on base metal and weldments in the strain range of 0.2–1.2%. The monotonic and cyclic stress-strain curves, stress-life, strain-life and energy-life in terms of these materials were analyzed for fatigue assessment of materials discrepancy. The stress-life results of base metal and undermatched weld metal exhibit cyclic softening behaviors. Furthermore, the shapes of 10CrNi3MoV steel hysteresis loops show a satisfactory Masing-type behavior, while the weld metal shows a non-Masing type behavior. Strain, plastic and total strain energy density amplitudes against the number of reversals to failure results demonstrate that the undermatched weld metal presents a higher resistance to fatigue crack initiation than 10CrNi3MoV high strength steel. Finally, fatigue fracture surfaces of specimens were compared by scanning electron microscopy to identify the differences of crack initiation and the propagation between them. Full article
(This article belongs to the Special Issue Deformation, Fatigue and Fracture of Materials)
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Open AccessArticle Influence of Annealing on Microstructure and Mechanical Properties of a Nanocrystalline CrCoNi Medium-Entropy Alloy
Materials 2018, 11(5), 662; https://doi.org/10.3390/ma11050662
Received: 5 April 2018 / Revised: 17 April 2018 / Accepted: 19 April 2018 / Published: 24 April 2018
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Abstract
An equiatomic CrCoNi medium-entropy alloy was subjected to high-pressure torsion. This process led to a refinement of the microstructure to a grain size of about 50 nm, combined with a strong increase in the materials hardness. Subsequently, the thermodynamic stability of the medium
[...] Read more.
An equiatomic CrCoNi medium-entropy alloy was subjected to high-pressure torsion. This process led to a refinement of the microstructure to a grain size of about 50 nm, combined with a strong increase in the materials hardness. Subsequently, the thermodynamic stability of the medium entropy alloy was evaluated by isothermal and isochronal heat treatments. Annealed samples were investigated by scanning and transmission electron microscopy as well as X-ray diffraction, and were subjected to tensile tests to establish microstructure-property relationships. Furthermore, a comparison of mechanical properties with a grade 316L stainless steel was performed in order to evaluate if the CrCoNi alloy is competitive with commercially available structural materials in the nanocrystalline state. A minority phase embedded in the face-centered cubic matrix of the CrCoNi alloy could be observed in multiple annealed states, as well as the as-received and high-pressure torsion processed material. For 200 h of annealing at 500 °C, it was determined that the minority phase has a hexagonal-closed-packed crystal structure. A possible explanation for the formation of the phase is a preferential segregation of Co to stacking faults. Full article
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Open AccessArticle Rupture Predictions of Notched Ti-6Al-4V Using Local Approaches
Materials 2018, 11(5), 663; https://doi.org/10.3390/ma11050663
Received: 10 April 2018 / Revised: 16 April 2018 / Accepted: 21 April 2018 / Published: 25 April 2018
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Abstract
Ti-6Al-4V has been extensively used in structural applications in various engineering fields, from naval to automotive and from aerospace to biomedical. Structural applications are characterized by geometrical discontinuities such as notches, which are widely known to harmfully affect their tensile strength. In recent
[...] Read more.
Ti-6Al-4V has been extensively used in structural applications in various engineering fields, from naval to automotive and from aerospace to biomedical. Structural applications are characterized by geometrical discontinuities such as notches, which are widely known to harmfully affect their tensile strength. In recent years, many attempts have been done to define solid criteria with which to reliably predict the tensile strength of materials. Among these criteria, two local approaches are worth mentioning due to the accuracy of their predictions, i.e., the strain energy density (SED) approach and the theory of critical distance (TCD) method. In this manuscript, the robustness of these two methods in predicting the tensile behavior of notched Ti-6Al-4V specimens has been compared. To this aim, two very dissimilar notch geometries have been tested, i.e., semi-circular and blunt V-notch with a notch root radius equal to 1 mm, and the experimental results have been compared with those predicted by the two models. The experimental values have been estimated with low discrepancies by either the SED approach and the TCD method, but the former results in better predictions. The deviations for the SED are in fact lower than 1.3%, while the TCD provides predictions with errors almost up to 8.5%. Finally, the weaknesses and the strengths of the two models have been reported. Full article
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Open AccessArticle Influence of Surface Features for Increased Heat Dissipation on Tool Wear
Materials 2018, 11(5), 664; https://doi.org/10.3390/ma11050664
Received: 9 March 2018 / Revised: 11 April 2018 / Accepted: 18 April 2018 / Published: 25 April 2018
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Abstract
The critical problems faced during the machining process of heat resistant superalloys, (HRSA), is the concentration of heat in the cutting zone and the difficulty in dissipating it. The concentrated heat in the cutting zone has a negative influence on the tool life
[...] Read more.
The critical problems faced during the machining process of heat resistant superalloys, (HRSA), is the concentration of heat in the cutting zone and the difficulty in dissipating it. The concentrated heat in the cutting zone has a negative influence on the tool life and surface quality of the machined surface, which in turn, contributes to higher manufacturing costs. This paper investigates improved heat dissipation from the cutting zone on the tool wear through surface features on the cutting tools. Firstly, the objective was to increase the available surface area in high temperature regions of the cutting tool. Secondly, multiple surface features were fabricated for the purpose of acting as channels in the rake face to create better access for the coolant to the proximity of the cutting edge. The purpose was thereby to improve the cooling of the cutting edge itself, which exhibits the highest temperature during machining. These modified inserts were experimentally investigated in face turning of Alloy 718 with high-pressure coolant. Overall results exhibited that surface featured inserts decreased flank wear, abrasion of the flank face, cutting edge deterioration and crater wear probably due to better heat dissipation from the cutting zone. Full article
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Open AccessArticle Understanding the Thermal Properties of Precursor-Ionomers to Optimize Fabrication Processes for Ionic Polymer-Metal Composites (IPMCs)
Materials 2018, 11(5), 665; https://doi.org/10.3390/ma11050665
Received: 15 March 2018 / Revised: 18 April 2018 / Accepted: 21 April 2018 / Published: 25 April 2018
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Abstract
Ionic polymer-metal composites (IPMCs) are one of many smart materials and have ionomer bases with a noble metal plated on the surface. The ionomer is usually Nafion, but recently Aquivion has been shown to be a promising alternative. Ionomers are available in the
[...] Read more.
Ionic polymer-metal composites (IPMCs) are one of many smart materials and have ionomer bases with a noble metal plated on the surface. The ionomer is usually Nafion, but recently Aquivion has been shown to be a promising alternative. Ionomers are available in the form of precursor pellets. This is an un-activated form that is able to melt, unlike the activated form. However, there is little study on the thermal characteristics of these precursor ionomers. This lack of knowledge causes issues when trying to fabricate ionomer shapes using methods such as extrusion, hot-pressing, and more recently, injection molding and 3D printing. To understand the two precursor-ionomers, a set of tests were conducted to measure the thermal degradation temperature, viscosity, melting temperature, and glass transition. The results have shown that the precursor Aquivion has a higher melting temperature (240 °C) than precursor Nafion (200 °C) and a larger glass transition range (32–65°C compared with 21–45 °C). The two have the same thermal degradation temperature (~400 °C). Precursor Aquivion is more viscous than precursor Nafion as temperature increases. Based on the results gathered, it seems that the precursor Aquivion is more stable as temperature increases, facilitating the manufacturing processes. This paper presents the data collected to assist researchers in thermal-based fabrication processes. Full article
(This article belongs to the Special Issue Smart Materials for Soft Sensors and Actuators)
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Open AccessArticle Effect of Inoculant Alloy Selection and Particle Size on Efficiency of Isomorphic Inoculation of Ti-Al
Materials 2018, 11(5), 666; https://doi.org/10.3390/ma11050666
Received: 29 March 2018 / Revised: 19 April 2018 / Accepted: 24 April 2018 / Published: 25 April 2018
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The process of isomorphic inoculation relies on precise selection of inoculant alloys for a given system. Three alloys, Ti-10Al-25Nb, Ti-25Al-10Ta, and Ti-47Ta (at %) were selected as potential isomorphic inoculants for a Ti-46Al alloy. The binary Ti-Ta alloy selected was found to be
[...] Read more.
The process of isomorphic inoculation relies on precise selection of inoculant alloys for a given system. Three alloys, Ti-10Al-25Nb, Ti-25Al-10Ta, and Ti-47Ta (at %) were selected as potential isomorphic inoculants for a Ti-46Al alloy. The binary Ti-Ta alloy selected was found to be ineffective as an inoculant due to its large density difference with the melt, causing the particles to settle. Both ternary alloys were successfully implemented as isomorphic inoculants that decreased the equiaxed grain size and increased the equiaxed fraction in their ingots. The degree of grain refinement obtained was found to be dependent on the number of particles introduced to the melt. Also, more new grains were formed than particles added to the melt. The grains/particle efficiency varied from greater than one to nearly twenty as the size of the particle increased. This is attributed to the breaking up of particles into smaller particles by dissolution in the melt. For a given particle size, Ti-Al-Ta and Ti-Al-Nb particles were found to have a roughly similar grain/particle efficiency. Full article
(This article belongs to the Special Issue Design of Alloy Metals for Low-Mass Structures)
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Open AccessArticle Effect of the Channel Length on the Transport Characteristics of Transistors Based on Boron-Doped Graphene Ribbons
Materials 2018, 11(5), 667; https://doi.org/10.3390/ma11050667
Received: 13 March 2018 / Revised: 21 April 2018 / Accepted: 23 April 2018 / Published: 25 April 2018
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Abstract
Substitutional boron doping of devices based on graphene ribbons gives rise to a unipolar behavior, a mobility gap, and an increase of the ION/IOFF ratio of the transistor. Here we study how this effect depends on
[...] Read more.
Substitutional boron doping of devices based on graphene ribbons gives rise to a unipolar behavior, a mobility gap, and an increase of the I O N / I O F F ratio of the transistor. Here we study how this effect depends on the length of the doped channel. By means of self-consistent simulations based on a tight-binding description and a non-equilibrium Green’s function approach, we demonstrate a promising increase of the I O N / I O F F ratio with the length of the channel, as a consequence of the different transport regimes in the ON and OFF states. Therefore, the adoption of doped ribbons with longer aspect ratios could represent a significant step toward graphene-based transistors with an improved switching behavior. Full article
(This article belongs to the Special Issue Recent Advances in 2D Nanomaterials)
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Open AccessArticle The Combined Influence of Hydrostatic Pressure and Temperature on Nonlinear Optical Properties of GaAs/Ga0.7Al0.3As Morse Quantum Well in the Presence of an Applied Magnetic Field
Materials 2018, 11(5), 668; https://doi.org/10.3390/ma11050668
Received: 2 April 2018 / Revised: 22 April 2018 / Accepted: 24 April 2018 / Published: 25 April 2018
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Abstract
Studies aimed at understanding the nonlinear optical (NLO) properties of GaAs/Ga0.7Al0.3As morse quantum well (QW) have focused on the intersubband optical absorption coefficients (OACs) and refractive index changes (RICs). These studies have taken two complimentary approaches: (1) The compact-density-matrix
[...] Read more.
Studies aimed at understanding the nonlinear optical (NLO) properties of GaAs/Ga0.7Al0.3As morse quantum well (QW) have focused on the intersubband optical absorption coefficients (OACs) and refractive index changes (RICs). These studies have taken two complimentary approaches: (1) The compact-density-matrix approach and iterative method have been used to obtain the expressions of OACs and RICs in morse QW. (2) Finite difference techniques have been used to obtain energy eigenvalues and their corresponding eigenfunctions of GaAs/Ga0.7Al0.3As morse QW under an applied magnetic field, hydrostatic pressure, and temperature. Our results show that the hydrostatic pressure and magnetic field have a significant influence on the position and the magnitude of the resonant peaks of the nonlinear OACs and RICs. Simultaneously, a saturation case is observed on the total absorption spectrum, which is modulated by the hydrostatic pressure and magnetic field. Physical reasons have been analyzed in depth. Full article
(This article belongs to the Special Issue Trends in Nonlinear Optical Materials)
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Open AccessArticle Enhanced Strength of a Mechanical Alloyed NbMoTaWVTi Refractory High Entropy Alloy
Materials 2018, 11(5), 669; https://doi.org/10.3390/ma11050669
Received: 10 April 2018 / Revised: 23 April 2018 / Accepted: 23 April 2018 / Published: 25 April 2018
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Abstract
A NbMoTaWVTi refractory high entropy alloy (HEA) has been successfully synthesized by mechanical alloying (MA) and spark plasma sintering (SPS). The microstructure and mechanical properties of this alloy are investigated. It is observed that only two types of body-centered cubic (BCC) solid solutions
[...] Read more.
A NbMoTaWVTi refractory high entropy alloy (HEA) has been successfully synthesized by mechanical alloying (MA) and spark plasma sintering (SPS). The microstructure and mechanical properties of this alloy are investigated. It is observed that only two types of body-centered cubic (BCC) solid solutions are formed in the powders after ball milling for 40 h. However, a new face-centered cubic (FCC) precipitated phase is observed in the BCC matrix of bulk material consolidated by SPS. The FCC precipitated phase is identified as TiO, due to the introduction of O during the preparing process of HEA. The compressive yield strength, fracture strength, and total fracture strain of the consolidated bulk HEA are 2709 MPa, 3115 MPa, and 11.4%, respectively. The excellent mechanical properties can be attributed to solid solution strengthening and grain boundary strengthening of the fine-grained BCC matrix, as well as the precipitation strengthening owing to the formation of TiO particles. Full article
(This article belongs to the Special Issue High Entropy Alloys)
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Open AccessArticle Synthesis, Characterization, and Photocatalytic Properties of Bamboo Charcoal/TiO2 Composites Using Four Sizes Powder
Materials 2018, 11(5), 670; https://doi.org/10.3390/ma11050670
Received: 25 March 2018 / Revised: 18 April 2018 / Accepted: 20 April 2018 / Published: 25 April 2018
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Abstract
Visible-light-active bamboo biochar/TiO2 composites were fabricated by the calcination method using C16H36O4Ti as the titanium source and bamboo powder with different sizes as the carbon source. The TiO2 nanoparticles were observed to disperse onto the
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Visible-light-active bamboo biochar/TiO2 composites were fabricated by the calcination method using C16H36O4Ti as the titanium source and bamboo powder with different sizes as the carbon source. The TiO2 nanoparticles were observed to disperse onto the surface of bamboo biochar fiber. The sizes of the bamboo powder played an important role in the microstructures and the properties of bamboo biochar/TiO2 composites. The bamboo biochar/TiO2 composites displayed the photocatalytic activities both under visible light irradiation and UV irradiation. The adsorption isotherms better fitted Freundlich isotherm models and the photodegradation reactions followed pseudo-first-order kinetics. Bamboo charcoal/TiO2 composites exhibited high stability after up to four cycles. This research could pave the way for high-value applications of biomass in the environmental field. Full article
(This article belongs to the Section Advanced Composites)
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Open AccessArticle Wide Angle of Incidence-Insensitive Polarization-Independent THz Metamaterial Absorber for Both TE and TM Mode Based on Plasmon Hybridizations
Materials 2018, 11(5), 671; https://doi.org/10.3390/ma11050671
Received: 27 March 2018 / Revised: 20 April 2018 / Accepted: 24 April 2018 / Published: 25 April 2018
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Abstract
An ultra-wide-angle THz metamaterial absorber (MA) utilizing sixteen-circular-sector (SCR) resonator for both transverse electric (TE) and transverse magnetic (TM) mode is designed and investigated numerically. At normal incidence, the absorptivity of the proposed MA is higher than 93.7% at 9.05 THz for different
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An ultra-wide-angle THz metamaterial absorber (MA) utilizing sixteen-circular-sector (SCR) resonator for both transverse electric (TE) and transverse magnetic (TM) mode is designed and investigated numerically. At normal incidence, the absorptivity of the proposed MA is higher than 93.7% at 9.05 THz for different polarization angles, due to the rotational symmetry structure of the unit cell. Under oblique incidence, the absorptivity can still exceed 90%, even when the incident angle is up to 70° for both TE and TM mode. Especially, the frequency variation in TE mode is less than 0.25% for different incident angles from 0° to 70°. The electric field (Ez) distributions are used to explain the absorption mechanism. Numerical simulation results show that the high absorption with wide-angle independence stems from fundamental dipole resonance and gap surface plasmons. The broadband deep-infrared MA is also obtained by stacking three metal-dielectric layers. The designed MA has great potential in bolometric pixel elements, biomedical sensors, THz imaging, and solar cells. Full article
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Open AccessArticle The Design and Optimization of Plasmonic Crystals for Surface Enhanced Raman Spectroscopy Using the Finite Difference Time Domain Method
Materials 2018, 11(5), 672; https://doi.org/10.3390/ma11050672
Received: 30 March 2018 / Revised: 19 April 2018 / Accepted: 24 April 2018 / Published: 26 April 2018
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Abstract
We present computational studies of quasi three-dimensional nanowell (NW) and nanopost (NP) plasmonic crystals for applications in surface enhanced Raman spectroscopy (SERS). The NW and NP plasmonic crystals are metal coated arrays of cylindrical voids or posts, respectively, in a dielectric substrate characterized
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We present computational studies of quasi three-dimensional nanowell (NW) and nanopost (NP) plasmonic crystals for applications in surface enhanced Raman spectroscopy (SERS). The NW and NP plasmonic crystals are metal coated arrays of cylindrical voids or posts, respectively, in a dielectric substrate characterized by a well/post diameter (D), relief depth (R D), periodicity (P), and metal thickness (M T). Each plasmonic crystal is modeled using the three-dimensional finite-difference time-domain (FDTD) method with periodic boundary conditions in the x- and y-directions applied to a computational unit cell to simulate the effect of a periodic array. Relative SERS responses are calculated from time-averaged electric field intensity enhancements at λ exc and λ scat or at λ mid via G SERS 4 = g 2 ( λ exc ) × g 2 ( λ scat ) or G mid 4 = g 4 ( λ mid ) , respectively, where g 2 = | E | 2 / | E 0 | 2 . Comparisons of G SERS 4 and G mid 4 are made to previously reported experimental SERS measurements for NW and NP geometries. Optimized NW and NP configurations based on variations of D, P, R D, and M T using G SERS 4 are presented, with 6× and 2× predicted increases in SERS, respectively. A novel plasmonic crystal based on square NP geometries are considered with an additional 3× increase over the optimized cylindrical NP geometry. NW geometries with imbedded spherical gold nanoparticles are considered, with 10× to 10 3 × increases in SERS responses over the NW geometry alone. The results promote the use of FDTD as a viable in silico route to the design and optimization of SERS active devices. Full article
(This article belongs to the Special Issue SERS-Active Substrates)
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Open AccessArticle Smart Metamaterial Based on the Simplex Tensegrity Pattern
Materials 2018, 11(5), 673; https://doi.org/10.3390/ma11050673
Received: 20 February 2018 / Revised: 8 April 2018 / Accepted: 23 April 2018 / Published: 26 April 2018
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Abstract
In the present paper, a novel cellular metamaterial that was based on a tensegrity pattern is presented. The material is constructed from supercells, each of which consists of eight 4-strut simplex modules. The proposed metamaterial exhibits some unusual properties, which are typical for
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In the present paper, a novel cellular metamaterial that was based on a tensegrity pattern is presented. The material is constructed from supercells, each of which consists of eight 4-strut simplex modules. The proposed metamaterial exhibits some unusual properties, which are typical for smart structures. It is possible to control its mechanical characteristics by adjusting the level of self-stress or by changing the properties of structural members. A continuum model is used to identify the qualitative properties of the considered metamaterial, and to estimate how the applied self-stress and the characteristics of cables and struts affect the whole structure. The performed analyses proved that the proposed structure can be regarded as a smart metamaterial with orthotropic properties. One of its most important features are unique values of Poisson’s ratio, which can be either positive or negative, depending on the applied control parameters. Moreover, all of the mechanical characteristics of the proposed metamaterial are prone to structural control. Full article
(This article belongs to the Special Issue Recent Advances in Smart Materials for the Built Environment)
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Open AccessArticle Fabrication of Metal-Substituted Polyoxometalates for Colorimetric Detection of Dopamine and Ractopamine
Materials 2018, 11(5), 674; https://doi.org/10.3390/ma11050674
Received: 4 April 2018 / Revised: 22 April 2018 / Accepted: 23 April 2018 / Published: 26 April 2018
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Abstract
A novel colorimetric detection method based on the peroxidase-like activity of metal-substituted polyoxometalates (POMs) of SiW9M3 (M = Co2+, Fe3+, Cu2+, Mn2+) has been established. POMs can catalyze oxidation of dopamine (DA)
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A novel colorimetric detection method based on the peroxidase-like activity of metal-substituted polyoxometalates (POMs) of SiW9M3 (M = Co2+, Fe3+, Cu2+, Mn2+) has been established. POMs can catalyze oxidation of dopamine (DA) and ractopamine (RAC) by H2O2 in aqueous solutions. SiW9Co3-based POMs detect DA at concentrations as low as 5.38 × 10−6 mol·L−1 simply by observation of the color change from colorless to orange using the naked eye. RAC is detected by observing the change from colorless to slight red by SiW9Cu3 with a detection limit of 7.94 × 10−5 mol·L−1. This study shows that colorimetric DA and RAC detection using SiW9Co3 and SiW9Cu3 is highly selective and sensitive as well as visually observable. Full article
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Open AccessArticle Effects of Pre-Treatments on Bioactivity of High-Purity Titanium
Materials 2018, 11(5), 675; https://doi.org/10.3390/ma11050675
Received: 3 March 2018 / Revised: 18 April 2018 / Accepted: 23 April 2018 / Published: 26 April 2018
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Abstract
Titanium and its alloys are frequently employed in medical and dental clinics due to their good tissue compatibility, including commercially available pure Ti, Ti6A4V, or Ti-15Zr-4Ta-4Nb. Yet, they may behave very differently when in contact with our plasma because of their own chemical
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Titanium and its alloys are frequently employed in medical and dental clinics due to their good tissue compatibility, including commercially available pure Ti, Ti6A4V, or Ti-15Zr-4Ta-4Nb. Yet, they may behave very differently when in contact with our plasma because of their own chemical composition. The present study was designed to compare the in vitro behavior of highly pure Ti (>99.99%; hpTi) with those of the above titanium specimens when they were subjected to heating in air (HT), H2O2 and heating (CHT), and heating in air after forming grooves on the surface (GT). Since one of the measures of material-tissue compatibility has been in vitro apatite formation in artificial plasma, like simulated body fluid (SBF) of the Kokubo recipe, the apatite deposition in SBF on their surface and in their grooves were examined in terms of the X-ray diffraction, scanning electron microscopy, and energy dispersion X-ray analysis. The results showed that hpTi was as active in in vitro apatite deposition as the other reference titanium samples mentioned above. Moreover, GT specimens of hpTi induced apatite deposition on the platform of the grooves as well as in the grooves. Therefore, hpTi was concluded to have better activity, and to be clinically applicable. Full article
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Open AccessArticle Research on the Single Grit Scratching Process of Oxygen-Free Copper (OFC)
Materials 2018, 11(5), 676; https://doi.org/10.3390/ma11050676
Received: 11 February 2018 / Revised: 29 March 2018 / Accepted: 23 April 2018 / Published: 26 April 2018
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Abstract
Single grit scratching is a basic form of material removal for many processes, such as grinding single point diamond turning and coating bonding performance tests. It has been widely used in the study of micro-scale and nano-scale material removal mechanisms. In this study,
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Single grit scratching is a basic form of material removal for many processes, such as grinding single point diamond turning and coating bonding performance tests. It has been widely used in the study of micro-scale and nano-scale material removal mechanisms. In this study, single grit linearly loading scratching tests were carried out on a scratching tester. A Rockwell indenter made of natural diamond was selected as the tool used, and the material of the workpiece was oxygen-free copper. Scratch topography was measured using a super-depth microscope to analyze the material deformation of the scratching process. A single grit scratching simulation has been developed by AdvantEdge™ to comprehensively study the material deformation of scratching processes. A material constitutive model and friction model were acquired using a quasi-static uniaxial compression experiment and a reciprocating friction test, respectively. These two models were used as the input models in the finite simulations. The simulated scratching forces aligned well with the experimental scratching forces, which verified the precision of the simulation model. Since only the scratching force could be obtained in the scratching experiment, the plastic strain, material flow, and residual stress of the scratching were further analyzed using simulations. The results showed that the plastic strain of the workpiece increased with the increase in scratching depth, and further analysis showed that the workpiece surface was distributed with residual compressive stress and the sub-surface was distributed with residual tensile stress in single grit scratching. Full article
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Open AccessCommunication Synthesis and Luminescent Properties of Europium Complexes Covalently Bonded to Hybrid Materials Based on MCM-41 and Poly(Ionic Liquids)
Materials 2018, 11(5), 677; https://doi.org/10.3390/ma11050677
Received: 13 April 2018 / Revised: 22 April 2018 / Accepted: 24 April 2018 / Published: 26 April 2018
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Abstract
Due to the wide potential application in the fields of sensing, lighting materials, and optical–electrical multifunctional devices, rare earth complex hybrid materials have been studied extensively over the past decades. A poly(ionic liquid)/mesoporous-based hybrid system which has been functionalized by the covalently linked
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Due to the wide potential application in the fields of sensing, lighting materials, and optical–electrical multifunctional devices, rare earth complex hybrid materials have been studied extensively over the past decades. A poly(ionic liquid)/mesoporous-based hybrid system which has been functionalized by the covalently linked europium complexes was reported here. Through surface modification with a coupling agent bearing an vinyl group, MCM-41 was chosen as the carrier matrix for poly(ionic liquids) (PILs) and europium compounds, and based on that, novel luminescent hybrid materials were prepared by confining the ionic liquid and europium complexes into the inorganic Si–O frameworks. The resulting organic/inorganic materials are chemically bonded hybrids which show good photoluminescent properties such as broad excitation spectra, line-like emission spectra, and long luminescence lifetimes. The PILs/MCM-41/Eu3+ hybrid reported here is a rare earth multifunctional material which is believed to have potential applications in the field of optical–electrical materials. Full article
(This article belongs to the Special Issue Hard and Soft Hybrid Functional Materials)
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Open AccessArticle The Incorporation of Strontium to Improve Bone-Regeneration Ability of Mesoporous Bioactive Glasses
Materials 2018, 11(5), 678; https://doi.org/10.3390/ma11050678
Received: 29 March 2018 / Revised: 20 April 2018 / Accepted: 20 April 2018 / Published: 26 April 2018
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Abstract
Over the recent years, mesoporous bioactive glasses (MBGs) gained interest as bone regeneration systems, due to their excellent bioactivity and ability to release therapeutic molecules. In order to improve the bone regeneration ability of MBGs, the incorporation of Sr2+ ions, due to
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Over the recent years, mesoporous bioactive glasses (MBGs) gained interest as bone regeneration systems, due to their excellent bioactivity and ability to release therapeutic molecules. In order to improve the bone regeneration ability of MBGs, the incorporation of Sr2+ ions, due to its recognized pro-osteogenenic potential, represents a very promising strategy. In this study, MBGs based on the SiO2–CaO system and containing different percentages (2 and 4 mol %) of strontium were prepared by two synthesis methods, in the form of microspheres and nanoparticles. Sr-containing MBGs were characterized by FE-SEM, XRD and N2 adsorption/desorption analysis. The in vitro bioactivity in SBF resulted excellent. The assessment of fibroblast cell (line L929) viability showed that Sr-containing MBGs were biocompatible both in form of micro- and nanoparticles. The osteogenic response of osteoblast-like SAOS-2 cells was investigated by analysing the expression of GAPDH, COL1a1, RANKL, SPARC, OPG and ALPL genes, as cell differentiation markers. The results indicate that the incorporation of Sr into MBG is beneficial for bone regeneration as promotes a pro-osteogenic effect, paving the way to the design of advanced devices enabled by these nanocarriers also in combination with drug release, for the treatment of bone pathologies, particularly in patients with osteoporosis. Full article
(This article belongs to the Special Issue State-of-the-Art Materials Science in Italy 2017)
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Open AccessArticle Preparation and Characterization of PVA Alkaline Solid Polymer Electrolyte with Addition of Bamboo Charcoal
Materials 2018, 11(5), 679; https://doi.org/10.3390/ma11050679
Received: 18 March 2018 / Revised: 15 April 2018 / Accepted: 20 April 2018 / Published: 26 April 2018
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Abstract
Natural bamboo charcoal (BC) powder has been developed as a novel filler in order to further improve performances of the polyvinyl alcohol (PVA)-based alkaline solid polymer electrolyte (ASPE) by solution casting method. X-ray diffraction patterns of composite polymer electrolyte with BC revealed the
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Natural bamboo charcoal (BC) powder has been developed as a novel filler in order to further improve performances of the polyvinyl alcohol (PVA)-based alkaline solid polymer electrolyte (ASPE) by solution casting method. X-ray diffraction patterns of composite polymer electrolyte with BC revealed the decrease in the degree of crystallinity with increasing content of BC. Scanning electron microscopy images showed pores on a micrometer scale (average diameter about 2 μm) distributed inside and on the surface of the membranes, indicating a three-dimension network formed in the polymer framework. The ionic conductivity was measured by the alternating-current (AC) impedance method, and the highest conductivity value of 6.63 × 10−2 S·cm−1 was obtained with 16 wt % of BC content and mKOH:mPVA = 2:1.5 at 30 °C. The contents of BC and KOH could significantly influence the conductivity. The temperature dependence of the bulk electrical conductivity displayed a combination of Arrhenius nature, and the activation energy for the ion in polymer electrolyte has been calculated. The electrochemical stability window of the electrolyte membrane was over 1.6 V. The thermogravimetric analysis curves showed that the degradation temperatures of PVA-BC-KOH ASPE membranes shifted toward higher with adding BC. A simple nickel-hydrogen battery containing PVA-BC-KOH electrolyte membrane was assembled with a maximum discharge capacity of 193 mAh·g−1. Full article
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Open AccessArticle Study on the Mechanical Properties of Bionic Coupling Layered B4C/5083Al Composite Materials
Materials 2018, 11(5), 680; https://doi.org/10.3390/ma11050680
Received: 28 February 2018 / Revised: 6 April 2018 / Accepted: 24 April 2018 / Published: 26 April 2018
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Abstract
Based on microstructure characteristics of Meretrix lusoria shell and Rapana venosa shell, bionic coupling layered B4C/5083Al composites with different layered structures and hard/soft combination models were fabricated via hot pressed sintering. The simplified bionic coupling models with hard and soft layers
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Based on microstructure characteristics of Meretrix lusoria shell and Rapana venosa shell, bionic coupling layered B4C/5083Al composites with different layered structures and hard/soft combination models were fabricated via hot pressed sintering. The simplified bionic coupling models with hard and soft layers were similar to layered structure and hardness tendency of shells, guiding the bionic design and fabrication. B4C/5083Al composites with various B4C contents and pure 5083Al were treated as hard and soft layers, respectively. Hot pressed sintering maintained the designed bionic structure and enhanced high bonding strength between ceramics and matrix. Compared with B4C/5083Al composites, bionic layered composites exhibited high mechanical properties including flexural strength, fracture toughness, compressive strength and impact toughness. The hard layers absorbed applied loads in the form of intergranular fracture. Besides connection role, soft layers restrained slabbing phenomenon and reset extension direction of cracks among layers. The coupling functions of bionic composites proved the feasibility and practicability of bionic fabrication, providing a new method for improvement of ceramic/Al composite with properties of being lightweight and high mechanical strength. Full article
(This article belongs to the Section Advanced Composites)
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Open AccessArticle Doxorubicin Release Controlled by Induced Phase Separation and Use of a Co-Solvent
Materials 2018, 11(5), 681; https://doi.org/10.3390/ma11050681
Received: 25 March 2018 / Revised: 17 April 2018 / Accepted: 25 April 2018 / Published: 26 April 2018
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Abstract
Electrospun-based drug delivery is emerging as a versatile means of localized therapy; however, controlling the release rates of active agents still remains as a key question. We propose a facile strategy to control the drug release behavior from electrospun fibers by a simple
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Electrospun-based drug delivery is emerging as a versatile means of localized therapy; however, controlling the release rates of active agents still remains as a key question. We propose a facile strategy to control the drug release behavior from electrospun fibers by a simple modification of polymer matrices. Polylactic acid (PLA) was used as a major component of the drug-carrier, and doxorubicin hydrochloride (Dox) was used as a model drug. The influences of a polar co-solvent, dimethyl sulfoxide (DMSO), and a hydrophilic polymer additive, polyvinylpyrrolidone (PVP), on the drug miscibility, loading efficiency and release behavior were investigated. The use of DMSO enabled the homogeneous internalization of the drug as well as higher drug loading efficiency within the electrospun fibers. The PVP additive induced phase separation in the PLA matrix and acted as a porogen. Preferable partitioning of Dox into the PVP domain resulted in increased drug loading efficiency in the PLA/PVP fiber. Fast dissolution of PVP domains created pores in the fibers, facilitating the release of internalized Dox. The novelty of this study lies in the detailed experimental investigation of the effect of additives in pre-spinning formulations, such as co-solvents and polymeric porogens, on the drug release behavior of nanofibers. Full article
(This article belongs to the Section Biomaterials)
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Open AccessArticle Cytokine and Chemokine Recovery Is Increased by Colloid Perfusates during Dermal Microdialysis
Materials 2018, 11(5), 682; https://doi.org/10.3390/ma11050682
Received: 9 February 2018 / Revised: 16 April 2018 / Accepted: 23 April 2018 / Published: 27 April 2018
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Abstract
Cytokines and chemokines play important roles in cell signalling, and microdialysis is a promising tool for monitoring these inflammation markers ex vivo. Therefore, the collecting of these mediators at the highest concentrations possible is crucial. Depending on the size of the mediator of
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Cytokines and chemokines play important roles in cell signalling, and microdialysis is a promising tool for monitoring these inflammation markers ex vivo. Therefore, the collecting of these mediators at the highest concentrations possible is crucial. Depending on the size of the mediator of interest, the collection of these high molecular mass molecules has thus far been difficult due to their low recovery, even when using high cut-off (100 kDa) microdialysis membranes. This study aimed to optimize the recovery of various cytokines and chemokines by validating the use of different perfusates in cutaneous microdialysis, and comparing intravenous (i.v.) colloids, crystalloids, and a lipid emulsion formulations that are approved for i.v. applications. Methods: In vitro and in vivo recovery experiments using six recombinant cytokines varying in molecular size (interleukin-2 (15 kDa), interleukin-6 (20.5 kDa), interleukin-8 (8 kDa), interleukin-12p70 (70 kDa), TNF-α (17.5 kDa), and vascular endothelial growth factor (VEGF) (38 kDa)) were performed in the presence of different perfusates for i.v. applications: Ringer’s lactate, dextran 60 kDa, hydroxyethyl starch 70 kDa, and hydroxyethyl starch 200 kDa solutions as well as a lipid emulsion formulation. Recovery was determined through (i) microdialysis of cytokines and chemokines in Ringer’s lactate solution or human serum in vitro, and (ii) retrodialysis of excised porcine and human skin cadavers in vitro and porcine skin in vivo. Furthermore, we used skin trauma (catheter insertion) and Ultraviolet B irradiation of 3 × 3 cm2 skin areas to sample cytokines and chemokines in vivo and compared the amounts that were obtained using crystalloid and colloid perfusates. All the cytokines and chemokines within the dialysates were quantified through a flow cytometry-based bead array assay. Results: Overall, recovery was strongly increased by the colloids, particularly hydroxyethyl starch 70 kDa, in vitro, ex vivo, and in vivo. When compared with the recovery achieved using Ringer’s lactate, this increase was most effective for proteins ranging from 8 to 20.5 kDa. Hydroxyethyl starch 70 kDa significantly increased the recovery of interleukin (IL)-8 in human serum in vitro when compared with Ringer’s lactate. More cytokines and chemokines were recovered using colloids compared with crystalloids. However, the increase in recovery values was lower for IL-12p70 and VEGF. Conclusions: Regarding the dialysate volumes and final dialysate concentrations, colloid perfusates are overall superior to crystalloid perfusates, such as Ringer’s lactate, when sampling cytokines and chemokines, resulting in higher recoveries. However, the sampling of high-molecular-mass cytokines during microdialysis remains challenging, and experimental in vitro data are not completely comparable with data obtained ex vivo or in vivo. Full article
(This article belongs to the Special Issue Polymeric Materials for Medical Applications)
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Open AccessArticle Atomic Scale Simulation on the Anti-Pressure and Friction Reduction Mechanisms of MoS2 Monolayer
Materials 2018, 11(5), 683; https://doi.org/10.3390/ma11050683
Received: 7 April 2018 / Revised: 24 April 2018 / Accepted: 26 April 2018 / Published: 27 April 2018
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Abstract
MoS2 nanosheets can be used as solid lubricants or additives of lubricating oils to reduce friction and resist wear. However, the atomic scale mechanism still needs to be illustrated. Herein, molecular simulations on the indentation and scratching process of MoS2 monolayer
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MoS2 nanosheets can be used as solid lubricants or additives of lubricating oils to reduce friction and resist wear. However, the atomic scale mechanism still needs to be illustrated. Herein, molecular simulations on the indentation and scratching process of MoS2 monolayer supported by Pt(111) surface were conducted to study the anti-pressure and friction reduction mechanisms of the MoS2 monolayer. Three deformation stages of Pt-supported MoS2 monolayer were found during the indentation process: elastic deformation, plastic deformation and finally, complete rupture. The MoS2 monolayer showed an excellent friction reduction effect at the first two stages, as a result of enhanced load bearing capacity and reduced deformation degree of the substrate. Unlike graphene, rupture of the Pt-supported MoS2 monolayer was related primarily to out-of-plane compression of the monolayer. These results provide a new insight into the relationship between the mechanical properties and lubrication properties of 2D materials. Full article
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Open AccessArticle Conservation of Monuments by a Three-Layered Compatible Treatment of TEOS-Nano-Calcium Oxalate Consolidant and TEOS-PDMS-TiO2 Hydrophobic/Photoactive Hybrid Nanomaterials
Materials 2018, 11(5), 684; https://doi.org/10.3390/ma11050684
Received: 12 March 2018 / Revised: 16 April 2018 / Accepted: 25 April 2018 / Published: 27 April 2018
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Abstract
In the conservation of monuments, research on innovative nanocomposites with strengthening, hydrophobic and self-cleaning properties have attracted the interest of the scientific community and promising results have been obtained as a result. In this study, stemming from the need for the compatibility of
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In the conservation of monuments, research on innovative nanocomposites with strengthening, hydrophobic and self-cleaning properties have attracted the interest of the scientific community and promising results have been obtained as a result. In this study, stemming from the need for the compatibility of treatments in terms of nanocomposite/substrate, a three-layered compatible treatment providing strengthening, hydrophobic, and self-cleaning properties is proposed. This conservation approach was implemented treating lithotypes and mortars of different porosity and petrographic characteristics with a three-layered treatment comprising: (a) a consolidant, tetraethoxysilane (TEOS)-nano-Calcium Oxalate; (b) a hydrophobic layer of TEOS-polydimethylsiloxane (PDMS); and (c) a self-cleaning layer of TiO2 nanoparticles from titanium tetra-isopropoxide with oxalic acid as hole-scavenger. After the three-layered treatment, the surface hydrophobicity was improved due to PDMS and nano-TiO2 in the interface substrate/atmosphere, as proven by the homogeneity and the Si–O–Ti hetero-linkages of the blend protective/self-cleaning layers observed by Scanning Electron Microscope (SEM), Transmission Electron Microscope (TEM) and Fourier-Transform Infrared Spectroscopy (FTIR). The aesthetic, microstructural, mechanical and permeabile compatibility of the majority of treated substrates ranged within acceptability limits. The improved photocatalytic activity, as proven by the total discoloration of methylene blue in the majority of cases, was attributed to the anchorage of TiO2, through the Si–O–Ti bonds to SiO2, in the interface with the atmosphere, thus enhancing photoactivation. Full article
(This article belongs to the Special Issue Selected Papers from TechnoHeritage 2017)
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Open AccessArticle A One-Component, Fast-Cure, and Economical Epoxy Resin System Suitable for Liquid Molding of Automotive Composite Parts
Materials 2018, 11(5), 685; https://doi.org/10.3390/ma11050685
Received: 13 March 2018 / Revised: 24 April 2018 / Accepted: 25 April 2018 / Published: 27 April 2018
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Abstract
Imidazole cured epoxy resin systems were evaluated for one-component, fast-curing resins for liquid molding of automotive composite parts according to industry requirements. It was demonstrated that an epoxy resin-1-(cyanoethyl)-2-ethyl-4-methylimidazol(EP-1C2E4MIM) system would cure in a few minutes at 120 °C, while exhibiting acceptable pot
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Imidazole cured epoxy resin systems were evaluated for one-component, fast-curing resins for liquid molding of automotive composite parts according to industry requirements. It was demonstrated that an epoxy resin-1-(cyanoethyl)-2-ethyl-4-methylimidazol(EP-1C2E4MIM) system would cure in a few minutes at 120 °C, while exhibiting acceptable pot life, viscosity profiles, and low water absorption. Moreover, this system yielded high Tg parts with mechanical properties similar to the amine-epoxy systems, which are the mainstream two-component epoxy resin systems for automobiles. Full article
(This article belongs to the Special Issue Carbon Fiber Reinforced Polymers)
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Open AccessArticle Performance Evaluation and Improving Mechanisms of Diatomite-Modified Asphalt Mixture
Materials 2018, 11(5), 686; https://doi.org/10.3390/ma11050686
Received: 3 April 2018 / Revised: 17 April 2018 / Accepted: 25 April 2018 / Published: 27 April 2018
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Abstract
Diatomite is an inorganic natural resource in large reserve. This study consists of two phases to evaluate the effects of diatomite on asphalt mixtures. In the first phase, we characterized the diatomite in terms of mineralogical properties, chemical compositions, particle size distribution, mesoporous
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Diatomite is an inorganic natural resource in large reserve. This study consists of two phases to evaluate the effects of diatomite on asphalt mixtures. In the first phase, we characterized the diatomite in terms of mineralogical properties, chemical compositions, particle size distribution, mesoporous distribution, morphology, and IR spectra. In the second phase, road performances, referring to the permanent deformation, crack, fatigue, and moisture resistance, of asphalt mixtures with diatomite were investigated. The characterization of diatomite exhibits that it is a porous material with high SiO2 content and large specific surface area. It contributes to asphalt absorption and therefore leads to bonding enhancement between asphalt and aggregate. However, physical absorption instead of chemical reaction occurs according to the results of FTIR. The resistance of asphalt mixtures with diatomite to permanent deformation and moisture are superior to those of the control mixtures. But, the addition of diatomite does not help to improve the crack and fatigue resistance of asphalt mixture. Full article
(This article belongs to the Special Issue Environment-Friendly Construction Materials)
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Open AccessArticle Metal/Carbon Hybrid Nanostructures Produced from Plasma-Enhanced Chemical Vapor Deposition over Nafion-Supported Electrochemically Deposited Cobalt Nanoparticles
Materials 2018, 11(5), 687; https://doi.org/10.3390/ma11050687
Received: 5 April 2018 / Revised: 22 April 2018 / Accepted: 23 April 2018 / Published: 27 April 2018
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Abstract
In this work, we report development of hybrid nanostructures of metal nanoparticles (NP) and carbon nanostructures with strong potential for catalysis, sensing, and energy applications. First, the etched silicon wafer substrates were passivated for subsequent electrochemical (EC) processing through grafting of nitro phenyl
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In this work, we report development of hybrid nanostructures of metal nanoparticles (NP) and carbon nanostructures with strong potential for catalysis, sensing, and energy applications. First, the etched silicon wafer substrates were passivated for subsequent electrochemical (EC) processing through grafting of nitro phenyl groups using para-nitrobenzene diazonium (PNBT). The X-ray photoelectron spectroscope (XPS) and atomic force microscope (AFM) studies confirmed presence of few layers. Cobalt-based nanoparticles were produced over dip or spin coated Nafion films under different EC reduction conditions, namely CoSO4 salt concentration (0.1 M, 1 mM), reduction time (5, 20 s), and indirect or direct EC reduction route. Extensive AFM examination revealed NP formation with different attributes (size, distribution) depending on electrochemistry conditions. While relatively large NP with >100 nm size and bimodal distribution were obtained after 20 s EC reduction in H3BO3 following Co2+ ion uptake, ultrafine NP (<10 nm) could be produced from EC reduction in CoSO4 and H3BO3 mixed solution with some tendency to form oxides. Different carbon nanostructures including few-walled or multiwalled carbon nanotubes (CNT) and carbon nanosheets were grown in a C2H2/NH3 plasma using the plasma-enhanced chemical vapor deposition technique. The devised processing routes enable size controlled synthesis of cobalt nanoparticles and metal/carbon hybrid nanostructures with unique microstructural features. Full article
(This article belongs to the Special Issue Supported Materials for Catalytic Application)
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Open AccessArticle Reactive Sintering Mechanism and Phase Formation in Ni-Ti-Al Powder Mixture During Heating
Materials 2018, 11(5), 689; https://doi.org/10.3390/ma11050689
Received: 28 March 2018 / Revised: 23 April 2018 / Accepted: 27 April 2018 / Published: 27 April 2018
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Abstract
This work aims to describe the formation of intermetallics in the Ni-Ti-Al system in dependence on the heating rate, which has been determined previously as the crucial factor of thermal explosion self-propagating synthesis (TE-SHS). The tested alloys contained 1–7 wt % aluminum. Thermal
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This work aims to describe the formation of intermetallics in the Ni-Ti-Al system in dependence on the heating rate, which has been determined previously as the crucial factor of thermal explosion self-propagating synthesis (TE-SHS). The tested alloys contained 1–7 wt % aluminum. Thermal analysis has been realized by the optical pyrometer under the conditions of high heating rates up to 110 °C·min−1. TE-SHS process in Ni-Ti-Al system is initiated by exothermic reaction of nickel aluminides Ni2Al3 and NiAl3 at the temperature of 535–610 °C. The next reactions occur in dependence on the heating rate. Samples containing 1–3 wt % of aluminum exhibit the similar initiation temperature as Ni-Ti binary mixture. The samples containing 5 wt % and more of aluminum were fully reacted after sintering at 800 °C with the heating rate of 300 °C·min−1 and the initiation temperature of the TE-SHS was observed close to Al-Al3Ni eutectic temperature (between 630–640 °C). Full article
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Open AccessArticle Study on Flake Formation Behavior and Its Influence Factors in Cr5 Steel
Materials 2018, 11(5), 690; https://doi.org/10.3390/ma11050690
Received: 4 April 2018 / Revised: 23 April 2018 / Accepted: 23 April 2018 / Published: 27 April 2018
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Abstract
A flake is a crack that is induced by trapped hydrogen within steel. To study its formation mechanism, previous studies mostly focused on the formation process and magnitude of hydrogen pressure in hydrogen traps such as cavities and cracks. However, according to recent
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A flake is a crack that is induced by trapped hydrogen within steel. To study its formation mechanism, previous studies mostly focused on the formation process and magnitude of hydrogen pressure in hydrogen traps such as cavities and cracks. However, according to recent studies, the hydrogen leads to the decline of the mechanical properties of steel, which is known as hydrogen embrittlement, is another reason for flake formation. In addition, the phenomenon of stress induced hydrogen uphill diffusion should not be neglected. All of the three behaviors are at work simultaneously. In order to further explore the formation mechanism of flakes in steel, the process of flake initiation and growth were studied with the following three coupling factors: trap hydrogen pressure, hydrogen embrittlement, and stress induced hydrogen re-distribution. The analysis model was established using the finite element method, and a crack whose radius is 0.5 mm was set in its center. The cohesive method and Bilinear Traction Separate Law (BTSL) were used to address the coupling effect. The results show that trap hydrogen pressure is the main driving force for flake formation. After the high hydrogen pressure was generated around the trap, a stress field formed. In addition, the trap is the center of stress concentration. Then, hydrogen is concentrated in a distribution around this trap, and most of the steel mechanical properties are reduced. The trap size is a key factor for defining the critical hydrogen content for flake formation and propagation. However, when the trap size exceeds the specified value, the critical hydrogen content does not change any more. As for the crack whose radius is 0.5 mm, the critical hydrogen content of Cr5VMo steel is 2.2 ppm, which is much closer to the maximum safe hydrogen concentration of 2.0 ppm used in China. The work presented in this article increases our understanding of flake formation and propagation mechanisms in steel. Full article
(This article belongs to the Special Issue Deformation, Fatigue and Fracture of Materials)
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Open AccessFeature PaperArticle C60 Bioconjugation with Proteins: Towards a Palette of Carriers for All pH Ranges
Materials 2018, 11(5), 691; https://doi.org/10.3390/ma11050691
Received: 16 March 2018 / Revised: 20 April 2018 / Accepted: 23 April 2018 / Published: 27 April 2018
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Abstract
The high hydrophobicity of fullerenes and the resulting formation of aggregates in aqueous solutions hamper the possibility of their exploitation in many technological applications. Noncovalent bioconjugation of fullerenes with proteins is an emerging approach for their dispersion in aqueous media. Contrary to covalent
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The high hydrophobicity of fullerenes and the resulting formation of aggregates in aqueous solutions hamper the possibility of their exploitation in many technological applications. Noncovalent bioconjugation of fullerenes with proteins is an emerging approach for their dispersion in aqueous media. Contrary to covalent functionalization, bioconjugation preserves the physicochemical properties of the carbon nanostructure. The unique photophysical and photochemical properties of fullerenes are then fully accessible for applications in nanomedicine, sensoristic, biocatalysis and materials science fields. However, proteins are not universal carriers. Their stability depends on the biological conditions for which they have evolved. Here we present two model systems based on pepsin and trypsin. These proteins have opposite net charge at physiological pH. They recognize and disperse C60 in water. UV-Vis spectroscopy, zeta-potential and atomic force microscopy analysis demonstrates that the hybrids are well dispersed and stable in a wide range of pH’s and ionic strengths. A previously validated modelling approach identifies the protein-binding pocket involved in the interaction with C60. Computational predictions, combined with experimental investigations, provide powerful tools to design tailor-made C60@proteins bioconjugates for specific applications. Full article
(This article belongs to the Special Issue Surface Modification of Nanoparticles)
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Open AccessArticle Synthesis and Characterization of Silver-Doped Mesoporous Bioactive Glass and Its Applications in Conjunction with Electrospinning
Materials 2018, 11(5), 692; https://doi.org/10.3390/ma11050692
Received: 31 March 2018 / Revised: 19 April 2018 / Accepted: 20 April 2018 / Published: 28 April 2018
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Abstract
Since they were first developed in 2004, mesoporous bioactive glasses (MBGs) rapidly captured the interest of the scientific community thanks to their numerous beneficial properties. MBGs are synthesised by a combination of the sol–gel method with the chemistry of surfactants to obtain highly
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Since they were first developed in 2004, mesoporous bioactive glasses (MBGs) rapidly captured the interest of the scientific community thanks to their numerous beneficial properties. MBGs are synthesised by a combination of the sol–gel method with the chemistry of surfactants to obtain highly mesoporous (pore size from 5 to 20 nm) materials that, owing to their high surface area and ordered structure, are optimal candidates for controlled drug-delivery systems. In this work, we synthesised and characterised a silver-containing mesoporous bioactive glass (Ag-MBG). It was found that Ag-MBG is a suitable candidate for controlled drug delivery, showing a perfectly ordered mesoporous structure ideal for the loading of drugs together with optimal bioactivity, sustained release of silver from the matrix, and fast and strong bacterial inhibition against both Gram-positive and Gram-negative bacteria. Silver-doped mesoporous glass particles were used in three electrospinning-based techniques to produce PCL/Ag-MBG composite fibres, to coat bioactive glass scaffolds (via electrospraying), and for direct sol electrospinning. The results obtained in this study highlight the versatility and efficacy of Ag-substituted mesoporous bioactive glass and encourage further studies to characterize the biological response to Ag-MBG-based antibacterial controlled-delivery systems for tissue-engineering applications. Full article
(This article belongs to the Special Issue Selected papers from EUROMAT 2017 Conference—Biomaterials)
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Open AccessArticle A Tensile Specimen of Tailor Rolled Blanks with Equal Probability in Yield and Its Mechanical Behavior Analysis
Materials 2018, 11(5), 693; https://doi.org/10.3390/ma11050693
Received: 21 March 2018 / Revised: 20 April 2018 / Accepted: 23 April 2018 / Published: 28 April 2018
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Abstract
In this paper, the microstructure and mechanical properties that distribute regulation along the rolling direction of tailor rolled blanks (TRB) were investigated. A tensile specimen with equal probability in yield (EYS) was first designed considering variation both in thickness and in material strength.
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In this paper, the microstructure and mechanical properties that distribute regulation along the rolling direction of tailor rolled blanks (TRB) were investigated. A tensile specimen with equal probability in yield (EYS) was first designed considering variation both in thickness and in material strength. The uniaxial tension test was carried out with a digital image correlation method to analyze the mechanical behaviors. The results showed that the strain distribution of EYS was homogeneous. From the results, it can be known that a new design philosophy for a TRB tensile specimen is reasonable and EYS is suitable to characterize the mechanical behavior of TRB. The true stress-strain curves of metal in different cross sections of TRB were calculated. On the basis of the true stress-strain curves, a material model of TRB was constructed and then implemented into finite element simulations of TRB uniaxial tensile tests. The strain distribution of numerical and experimental results was similar and the error between the elongation of the specimen after fracture obtained by experiment and FE ranged from 9.51% to 13.06%. Therefore, the simulation results match well with the experimental results and the material model has high accuracy and as well as practicability. Full article
(This article belongs to the Section Structure Analysis and Characterization)
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Open AccessFeature PaperArticle Long-Term Effectiveness, under a Mountain Environment, of a Novel Conservation Nanomaterial Applied on Limestone from a Roman Archaeological Site
Materials 2018, 11(5), 694; https://doi.org/10.3390/ma11050694
Received: 7 March 2018 / Revised: 17 April 2018 / Accepted: 25 April 2018 / Published: 28 April 2018
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Abstract
A novel alkoxysilane-based product was applied on limestone samples from a Roman archaeological site. The study consisted of an initial phase to evaluate site environmental conditions in order to choose the most suitable product type to be applied. The decay that was produced
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A novel alkoxysilane-based product was applied on limestone samples from a Roman archaeological site. The study consisted of an initial phase to evaluate site environmental conditions in order to choose the most suitable product type to be applied. The decay that was produced in the site is mainly caused by natural action, with water being the main vehicle for the decay agents. Thus, the effectiveness of an innovative product with hydrophobic/consolidant properties and two commercial products (consolidant and hydrophobic agent) were evaluated on limestone from Acinipo site, under laboratory conditions. Next, the long-term effectiveness of the three products under study was evaluated by the exposure of limestone samples in the archaeological site for a period of three years. Since the recognized incompatibility between alkoxysilanes and pure carbonate stones, the interaction between the products and the limestones was widely investigated. The results that were obtained allow for it to be concluded that the innovative product presents adequate compatibility and adherence to the limestone under study, producing a long-term effective, homogeneous, and continuous coating with a depth of penetration of up to 10 mm. However, the commercial products produced discontinuous aggregates on the limestone surface, did not penetrate into its porous structure and it did not produce long-lasting effects. Full article
(This article belongs to the Special Issue Selected Papers from TechnoHeritage 2017)
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Open AccessArticle Different Effects of NSF and PCE Superplasticizer on Adsorption, Dynamic Yield Stress and Thixotropy of Cement Pastes
Materials 2018, 11(5), 695; https://doi.org/10.3390/ma11050695
Received: 17 April 2018 / Revised: 24 April 2018 / Accepted: 25 April 2018 / Published: 28 April 2018
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Abstract
This study compares the differences and similarities of two types of superplasticizers—NSF (Naphthalene Sulfonate Formaldehyde) and PCE (PolyCarboxylate Ester)—in fresh cement paste systems, in terms of adsorption, dynamic yield stress, and thixotropic index. Results show that with either NSF or PCE addition, the
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This study compares the differences and similarities of two types of superplasticizers—NSF (Naphthalene Sulfonate Formaldehyde) and PCE (PolyCarboxylate Ester)—in fresh cement paste systems, in terms of adsorption, dynamic yield stress, and thixotropic index. Results show that with either NSF or PCE addition, the more superplasticizer is added, the more it is adsorbed and the more it remains in the interstitial pore solution. The dynamic yield stress and thixotropic index also decrease with increasing addition the amount of either superplasticizer. However, NSF is less efficient in decreasing the dynamic yield stress than PCE. More importantly, the decreasing patterns of dynamic yield stress and thixotropic index are different with NSF and PCE additions; this is tied to the adsorption and dispersing mechanisms of these two types of superplasticizers. Full article
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Open AccessArticle Synthesis and Characterization of pH and Thermo Dual-Responsive Hydrogels with a Semi-IPN Structure Based on N-Isopropylacrylamide and Itaconamic Acid
Materials 2018, 11(5), 696; https://doi.org/10.3390/ma11050696
Received: 17 March 2018 / Revised: 22 April 2018 / Accepted: 24 April 2018 / Published: 28 April 2018
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Abstract
A series of semi-interpenetrating polymer network (semi-IPN) hydrogels were synthesized and investigated in this study. Linear copolymer poly(N-isopropylacrylamide-co-itaconamic acid) p(NIPAM-co-IAM), which is formed by copolymerization of N-isopropylacrylamide (NIPAM) and itaconamic acid (IAM, 4-amino-2-ethylene-4-oxobutanoic acid), was introduced into a solution of
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A series of semi-interpenetrating polymer network (semi-IPN) hydrogels were synthesized and investigated in this study. Linear copolymer poly(N-isopropylacrylamide-co-itaconamic acid) p(NIPAM-co-IAM), which is formed by copolymerization of N-isopropylacrylamide (NIPAM) and itaconamic acid (IAM, 4-amino-2-ethylene-4-oxobutanoic acid), was introduced into a solution of NIPAM to form a series of pH and thermo dual-responsive p(NIPAM-co-IAM)/pNIPAM semi-IPN hydrogels by free radical polymerization. The structural, morphological, chemical, and physical properties of the linear copolymer and semi-IPN hydrogels were investigated. The semi-IPN hydrogel showed high thermal stability according to thermal gravimetric analyzer (TGA). Scanning electronic microscopy (SEM) images showed that the pore size was in the range of 119~297 µm and could be controlled by the addition ratio of the linear copolymer in the semi-IPN structure. The addition of linear copolymer increased the fracture strain from 57.5 ± 2.9% to 91.1 ± 4.9% depending on the added amount, while the compressive modulus decreased as the addition increased. Moreover, the pH and thermo dual-responsive properties were investigated using differential scanning calorimetry (DSC) and monitoring the swelling behavior of the hydrogels. In deionized (DI) water, the equilibrium swelling ratio of the hydrogels decreased as the temperature increased from 20 °C to 50 °C, while it varied in various pH buffer solutions. In addition, the swelling and deswelling rates of the hydrogels also significantly increased. The results indicate that the novel pH-thermo dual-responsive semi-IPN hydrogels were synthesized successfully and may be a potential material for biomedical, drug delivery, or absorption application. Full article
(This article belongs to the Section Smart Materials)
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Open AccessArticle Investigation of the Behavior of Hardening Masonry Exposed to Variable Stresses
Materials 2018, 11(5), 697; https://doi.org/10.3390/ma11050697
Received: 16 March 2018 / Revised: 19 April 2018 / Accepted: 24 April 2018 / Published: 28 April 2018
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Abstract
This paper analyzes the behavior of masonry under variable loads during execution (construction stage). It specifies the creep coefficient for calcium silicate brick masonry, presenting the research data of masonry deformation under variable and constant long-term loads. The interaction of separate layers of
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This paper analyzes the behavior of masonry under variable loads during execution (construction stage). It specifies the creep coefficient for calcium silicate brick masonry, presenting the research data of masonry deformation under variable and constant long-term loads. The interaction of separate layers of composite material in masonry is introduced and the formulae for determining long-term deformations are offered. The research results of masonry’s compressive strength and deformation properties under variable and constant long-term loads are presented. These are then compared to calculated ones. According to the presented comparison, the calculated long-term deformations coincide quite well with those determined experimentally. Full article
(This article belongs to the Section Structure Analysis and Characterization)
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Open AccessArticle Understanding the Interaction between a Steel Microstructure and Hydrogen
Materials 2018, 11(5), 698; https://doi.org/10.3390/ma11050698
Received: 2 April 2018 / Revised: 23 April 2018 / Accepted: 24 April 2018 / Published: 28 April 2018
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Abstract
The present work provides an overview of the work on the interaction between hydrogen (H) and the steel’s microstructure. Different techniques are used to evaluate the H-induced damage phenomena. The impact of H charging on multiphase high-strength steels, i.e., high-strength low-alloy (HSLA), transformation-induced
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The present work provides an overview of the work on the interaction between hydrogen (H) and the steel’s microstructure. Different techniques are used to evaluate the H-induced damage phenomena. The impact of H charging on multiphase high-strength steels, i.e., high-strength low-alloy (HSLA), transformation-induced plasticity (TRIP) and dual phase (DP) is first studied. The highest hydrogen embrittlement resistance is obtained for HSLA steel due to the presence of Ti- and Nb-based precipitates. Generic Fe-C lab-cast alloys consisting of a single phase, i.e., ferrite, bainite, pearlite or martensite, and with carbon contents of approximately 0, 0.2 and 0.4 wt %, are further considered to simplify the microstructure. Finally, the addition of carbides is investigated in lab-cast Fe-C-X alloys by adding a ternary carbide forming element to the Fe-C alloys. To understand the H/material interaction, a comparison of the available H trapping sites, the H pick-up level and the H diffusivity with the H-induced mechanical degradation or H-induced cracking is correlated with a thorough microstructural analysis. Full article
(This article belongs to the Special Issue State-of-the-Art Materials Science in Belgium 2017)
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Open AccessArticle A Study of the Stability Mechanism of the Dispersed Particle Gel Three-Phase Foam Using the Interfacial Dilational Rheology Method
Materials 2018, 11(5), 699; https://doi.org/10.3390/ma11050699
Received: 11 April 2018 / Revised: 22 April 2018 / Accepted: 25 April 2018 / Published: 28 April 2018
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Abstract
The dispersed particle gel (DPG) three-phase foam is a novel profile control and flooding system. The stability mechanism of the DPG three-phase foam was studied using an interfacial dilational rheology method. The results show that the elastic modulus of the DPG three-phase foam
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The dispersed particle gel (DPG) three-phase foam is a novel profile control and flooding system. The stability mechanism of the DPG three-phase foam was studied using an interfacial dilational rheology method. The results show that the elastic modulus of the DPG three-phase foam is up to 14 mN/m, which is much higher than the traditional foam. The increase in interface elasticity produces significantly positive effects on foam stability. Emphasis is given to the influences of frequency, temperature, pressure, and concentration on the viscoelasticity and interfacial adsorption of DPG particles, which change the modules of the foam interface and have a significant effect on foam stability. In addition, the microstructure of the DPG three-phase foam was observed. A viscoelastic shell is formed by the aggregation of the DPG particles on the interface. The irreversible adsorption gives the interface high elasticity and mechanical strength. The electrostatic repulsion between particles increases the spacing between bubbles. The combined effects of these factors give the interface higher mechanical strength, slow down the film drainage, effectively prevent gas permeation, and significantly improve the foam stability. Full article
(This article belongs to the Section Advanced Composites)
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Open AccessArticle Type I Collagen and Strontium-Containing Mesoporous Glass Particles as Hybrid Material for 3D Printing of Bone-Like Materials
Materials 2018, 11(5), 700; https://doi.org/10.3390/ma11050700
Received: 29 March 2018 / Revised: 20 April 2018 / Accepted: 25 April 2018 / Published: 28 April 2018
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Abstract
Bone tissue engineering offers an alternative promising solution to treat a large number of bone injuries with special focus on pathological conditions, such as osteoporosis. In this scenario, the bone tissue regeneration may be promoted using bioactive and biomimetic materials able to direct
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Bone tissue engineering offers an alternative promising solution to treat a large number of bone injuries with special focus on pathological conditions, such as osteoporosis. In this scenario, the bone tissue regeneration may be promoted using bioactive and biomimetic materials able to direct cell response, while the desired scaffold architecture can be tailored by means of 3D printing technologies. In this context, our study aimed to develop a hybrid bioactive material suitable for 3D printing of scaffolds mimicking the natural composition and structure of healthy bone. Type I collagen and strontium-containing mesoporous bioactive glasses were combined to obtain suspensions able to perform a sol-gel transition under physiological conditions. Field emission scanning electron microscopy (FESEM) analyses confirmed the formation of fibrous nanostructures homogeneously embedding inorganic particles, whereas bioactivity studies demonstrated the large calcium phosphate deposition. The high-water content promoted the strontium ion release from the embedded glass particles, potentially enhancing the osteogenic behaviour of the composite. Furthermore, the suspension printability was assessed by means of rheological studies and preliminary extrusion tests, showing shear thinning and fast material recovery upon deposition. In conclusion, the reported results suggest that promising hybrid systems suitable for 3D printing of bioactive scaffolds for bone tissue engineering have been developed. Full article
(This article belongs to the Special Issue Selected papers from EUROMAT 2017 Conference—Biomaterials)
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Open AccessArticle A Feasible Strategy for Fabricating Surface Porous Network in Fe-Si Ribbons
Materials 2018, 11(5), 701; https://doi.org/10.3390/ma11050701
Received: 19 March 2018 / Revised: 26 April 2018 / Accepted: 26 April 2018 / Published: 29 April 2018
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Abstract
Porous materials have always attracted extensive attention owing to their low density, tunable porosity and high surface area. Generally, porosity is introduced in amorphous materials through dealloying or electrochemical dealloying processes. In this work, an iron-based surface porous network was successfully fabricated utilizing
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Porous materials have always attracted extensive attention owing to their low density, tunable porosity and high surface area. Generally, porosity is introduced in amorphous materials through dealloying or electrochemical dealloying processes. In this work, an iron-based surface porous network was successfully fabricated utilizing selective electrochemical dissolution of Fe-Si alloy ribbons based on the cellular structure prepared by melt-spinning technique. After 30 s, the surface of the ribbon gradually becomes flat and grains can be observed in the first stage of electrochemistry; after an extra 10 s, the pores spread throughout the surface of the ribbon in the second stage. The average size of pores is about 310 nm and the average size of the ligament is 150 nm. The associated dissolution mechanism has been proposed based on the inhomogeneous composition of the center and edge of the cell. The entire process of electrochemical dissolution has been divided into two stages and the entire duration of synthesis does not exceed one minute. This method is extremely feasible and provides a promising strategy for preparing surface porous materials for selective electrochemical dissolution of cellular structure. Full article
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Open AccessArticle An Electrochemical Sensor of Poly(EDOT-pyridine-EDOT)/Graphitic Carbon Nitride Composite for Simultaneous Detection of Cd2+ and Pb2+
Materials 2018, 11(5), 702; https://doi.org/10.3390/ma11050702
Received: 20 March 2018 / Revised: 17 April 2018 / Accepted: 20 April 2018 / Published: 29 April 2018
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Abstract
In this study, poly(2,5-bis(3,4-ethylenedioxythienyl)pyridine)/graphitic carbon nitride composites (poly(BPE)/g-C3N4) were prepared by an in situ chemical polymerization method. Composites were characterized by using Fourier transform infrared spectroscopy (FT-IR), ultraviolet–visible absorption spectra (UV–vis), X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDS), scanning
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In this study, poly(2,5-bis(3,4-ethylenedioxythienyl)pyridine)/graphitic carbon nitride composites (poly(BPE)/g-C3N4) were prepared by an in situ chemical polymerization method. Composites were characterized by using Fourier transform infrared spectroscopy (FT-IR), ultraviolet–visible absorption spectra (UV–vis), X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDS), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). Furthermore, electrochemical sensors were applied for the electrochemical determination of Cd2+ and Pb2+ using the differential pulse voltammetry (DPV) method. The results indicated that 10 wt % poly(BPE)/g-C3N4 composite-modified electrode exhibited linear detection ranging from 0.12 to 7.2 μM and 0.08 to 7.2 μM for Cd2+ and Pb2+, with detection limits (S/N = 3) of 0.018 μM and 0.00324 μM. Interference analysis suggested that the 10 wt % poly(BPE)/g-C3N4-modified electrode can be applied for the detection of the Cd2+ and Pb2+ in real samples. Full article
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Open AccessArticle Microstructure and Mechanical Properties of the As-Cast and As-Homogenized Mg-Zn-Sn-Mn-Ca Alloy Fabricated by Semicontinuous Casting
Materials 2018, 11(5), 703; https://doi.org/10.3390/ma11050703
Received: 25 March 2018 / Revised: 26 April 2018 / Accepted: 26 April 2018 / Published: 29 April 2018
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Abstract
In this paper, a new type of low-cost Mg-3.36Zn-1.06Sn-0.33Mn-0.27Ca (wt %) alloy ingot with a diameter of 130 mm and a length of 4800 mm was fabricated by semicontinuous casting. The microstructure and mechanical properties at different areas of the ingot were investigated.
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In this paper, a new type of low-cost Mg-3.36Zn-1.06Sn-0.33Mn-0.27Ca (wt %) alloy ingot with a diameter of 130 mm and a length of 4800 mm was fabricated by semicontinuous casting. The microstructure and mechanical properties at different areas of the ingot were investigated. The microstructure and mechanical properties of the alloy under different one-step and two-step homogenization conditions were studied. For the as-cast alloy, the average grain size and the second phase size decrease from the center to the surface of the ingot, while the area fraction of the second phase increases gradually. At one-half of the radius of the ingot, the alloy presents the optimum comprehensive mechanical properties along the axial direction, which is attributed to the combined effect of relatively small grain size, low second-phase fraction, and uniform microstructure. For the as-homogenized alloy, the optimum two-step homogenization process parameters were determined as 340 °C × 10 h + 520 °C × 16 h. After the optimum homogenization, the proper size and morphology of CaMgSn phase are conducive to improve the microstructure uniformity and the mechanical properties of the alloy. Besides, the yield strength of the alloy is reduced by 20.7% and the elongation is increased by 56.3%, which is more favorable for the subsequent hot deformation processing. Full article
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Open AccessArticle Effect of Temperature and Growth Time on Vertically Aligned ZnO Nanorods by Simplified Hydrothermal Technique for Photoelectrochemical Cells
Materials 2018, 11(5), 704; https://doi.org/10.3390/ma11050704
Received: 14 March 2018 / Revised: 3 April 2018 / Accepted: 4 April 2018 / Published: 29 April 2018
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Abstract
Despite its large band gap, ZnO has wide applicability in many fields ranging from gas sensors to solar cells. ZnO was chosen over other materials because of its large exciton binding energy (60 meV) and its stability to high-energy radiation. In this study,
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Despite its large band gap, ZnO has wide applicability in many fields ranging from gas sensors to solar cells. ZnO was chosen over other materials because of its large exciton binding energy (60 meV) and its stability to high-energy radiation. In this study, ZnO nanorods were deposited on ITO glass via a simple dip coating followed by a hydrothermal growth. The morphological, structural and compositional characteristics of the prepared films were analyzed using X-ray diffractometry (XRD), field emission scanning electron microscopy (FESEM), and ultraviolet-visible spectroscopy (UV-Vis). Photoelectrochemical conversion efficiencies were evaluated via photocurrent measurements under calibrated halogen lamp illumination. Thin film prepared at 120 °C for 4 h of hydrothermal treatment possessed a hexagonal wurtzite structure with the crystallite size of 19.2 nm. The average diameter of the ZnO nanorods was 37.7 nm and the thickness was found to be 2680.2 nm. According to FESEM images, as the hydrothermal growth temperature increases, the nanorod diameter become smaller. Moreover, the thickness of the nanorods increase with the growth time. Therefore, the sample prepared at 120 °C for 4 h displayed an impressive photoresponse by achieving high current density of 0.1944 mA/cm2. Full article
(This article belongs to the Section Thin Films)
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Open AccessArticle The Effect of Different Porogens on Porous PMMA Microspheres by Seed Swelling Polymerization and Its Application in High-Performance Liquid Chromatography
Materials 2018, 11(5), 705; https://doi.org/10.3390/ma11050705
Received: 9 April 2018 / Revised: 24 April 2018 / Accepted: 25 April 2018 / Published: 29 April 2018
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Monodisperse cross-linked porous poly (methyl methacrylate) (PMMA) microspheres (~2.5 μm in diameter) were prepared by using an improved two-step seed swelling polymerization method with monodisperse micron-grade PMMA microspheres seeds. The porous PMMA microspheres with diverse surface morphology and pore structure were obtained by
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Monodisperse cross-linked porous poly (methyl methacrylate) (PMMA) microspheres (~2.5 μm in diameter) were prepared by using an improved two-step seed swelling polymerization method with monodisperse micron-grade PMMA microspheres seeds. The porous PMMA microspheres with diverse surface morphology and pore structure were obtained by tuning porogen systems. The monodisperse porous PMMA microspheres, which were prepared using toluene:dibutylphthalate (DBP) = 1:1 (v/v) as a porogen system, had the smallest pore size and the largest specific surface area. Then, the monodisperse porous PMMA microspheres were subjected to high-performance liquid chromatography. The liquid chromatographic column filler successfully realized complete separation of arginine, glycine and glutamic acid, and the separation effect was good. The porous PMMA microspheres provide a new material for the separation of amino acids by liquid chromatography. Full article
(This article belongs to the Section Porous Materials)
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Open AccessArticle Evaluation of Residual Stress Distribution and Relaxation on In Situ TiB2/7050 Al Composites
Materials 2018, 11(5), 706; https://doi.org/10.3390/ma11050706
Received: 2 February 2018 / Revised: 15 March 2018 / Accepted: 24 April 2018 / Published: 30 April 2018
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Abstract
Interior residual stresses induced by quenching may cause distortion during subsequent machining processes. Hence, various strategies have been employed to relieve the interior residual stress, such as stretching, post treatment, and other techniques. In this study, the stress distribution inside TiB2/7050
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Interior residual stresses induced by quenching may cause distortion during subsequent machining processes. Hence, various strategies have been employed to relieve the interior residual stress, such as stretching, post treatment, and other techniques. In this study, the stress distribution inside TiB2/7050 Al composite extrusions was investigated and the effects of different methods on relieving the quenching-induced stress were compared. Firstly, three TiB2/7050 Al composite extrusions were treated by stretching, stretching and heat treatment, and stretching and cold treatment processes, respectively. Then, the multiple-cut contour method was employed to assess the residual stresses in the three workpieces. Experimental results indicate that the interior stress of TiB2/7050 Al composite extrusions after stretching ranges from −89 MPa to +55 MPa, which is larger than that in 7050 aluminum alloy, which ranges from −25 Pa to +25 MPa. The heat treatment performs better than the cold treatment to reduce the post-stretching residual stress, with a reduction of 23.2–46.4% compared to 11.3–40.8%, respectively. From the stress map, it is found that the stress distribution after the heat treatment is more uniform compared with that after the cold treatment. Full article
(This article belongs to the Section Advanced Composites)
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Open AccessArticle Deposition of Zinc Oxide on Different Polymer Textiles and Their Antibacterial Properties
Materials 2018, 11(5), 707; https://doi.org/10.3390/ma11050707
Received: 25 March 2018 / Revised: 26 April 2018 / Accepted: 26 April 2018 / Published: 30 April 2018
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Abstract
A surface modification of polyamide 6 (PA), polyethylene terephthalate (PET) and polypropylene (PP) textiles was performed using zinc oxide to obtain antibacterial layer. ZnO microrods were synthesized on ZnO nanoparticles (NPs) as a nucleus centers by chemical bath deposition (CBD) process. Scanning Electron
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A surface modification of polyamide 6 (PA), polyethylene terephthalate (PET) and polypropylene (PP) textiles was performed using zinc oxide to obtain antibacterial layer. ZnO microrods were synthesized on ZnO nanoparticles (NPs) as a nucleus centers by chemical bath deposition (CBD) process. Scanning Electron Microscopy (SEM) and X-ray diffraction (XRD) indicated that wurzite ZnO microrods were obtained on every sample. Differential Scanning Calorimetry (DSC), Fourier Transform Infrared Spectroscopy (FTIR), Atomic Force Microscopy (AFM) and Liquid Absorption Capacity (LAC) analysis indicate that the amount and structure of antibacterial layer is dependent on roughness and wettability of textile surface. The rougher and more hydrophilic is the material, the more ZnO were deposited. All studied textiles show significant bactericidal activity against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus). A possible mechanism and difference in sensitivity between Gram-negative and Gram-positive bacteria to ZnO is discussed. Considering that antibacterial activity of ZnO is caused by Reactive Oxygen Species (ROS) generation, an influence of surface to volume ratio and crystalline parameters is also discussed. Full article
(This article belongs to the Section Biomaterials)
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