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Materials, Volume 10, Issue 1 (January 2017)

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Cover Story (view full-size image) Breaking the habits is healthy when talking about fundamental researches on materials. Here, the [...] Read more.
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Editorial

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Open AccessEditorial Acknowledgement to Reviewers of Materials in 2016
Materials 2017, 10(1), 62; https://doi.org/10.3390/ma10010062
Received: 12 January 2017 / Revised: 12 January 2017 / Accepted: 12 January 2017 / Published: 12 January 2017
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Abstract
The editors of Materials would like to express their sincere gratitude to the following reviewers for assessing manuscripts in 2016.[...] Full article

Research

Jump to: Editorial, Review, Other

Open AccessArticle Direct Printing of 1-D and 2-D Electronically Conductive Structures by Molten Lead-Free Solder
Materials 2017, 10(1), 1; https://doi.org/10.3390/ma10010001
Received: 5 September 2016 / Revised: 6 December 2016 / Accepted: 16 December 2016 / Published: 22 December 2016
Cited by 15 | PDF Full-text (7173 KB) | HTML Full-text | XML Full-text
Abstract
This study aims to determine the effects of appropriate experimental parameters on the thermophysical properties of molten micro droplets, Sn-3Ag-0.5Cu solder balls with an average droplet diameter of 50 μm were prepared. The inkjet printing parameters of the molten micro droplets, such as
[...] Read more.
This study aims to determine the effects of appropriate experimental parameters on the thermophysical properties of molten micro droplets, Sn-3Ag-0.5Cu solder balls with an average droplet diameter of 50 μm were prepared. The inkjet printing parameters of the molten micro droplets, such as the dot spacing, stage velocity and sample temperature, were optimized in the 1D and 2D printing of metallic microstructures. The impact and mergence of molten micro droplets were observed with a high-speed digital camera. The line width of each sample was then calculated using a formula over a temperature range of 30 to 70 °C. The results showed that a metallic line with a width of 55 μm can be successfully printed with dot spacing (50 μm) and the stage velocity (50 mm∙s−1) at the substrate temperature of 30 °C. The experimental results revealed that the height (from 0.63 to 0.58) and solidification contact angle (from 72° to 56°) of the metallic micro droplets decreased as the temperature of the sample increased from 30 to 70 °C. High-speed digital camera (HSDC) observations showed that the quality of the 3D micro patterns improved significantly when the droplets were deposited at 70 °C. Full article
(This article belongs to the Special Issue Metals for Additive Manufacturing)
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Open AccessArticle Effects of Cracking Test Conditions on Estimation Uncertainty for Weibull Parameters Considering Time-Dependent Censoring Interval
Materials 2017, 10(1), 3; https://doi.org/10.3390/ma10010003
Received: 30 November 2016 / Revised: 13 December 2016 / Accepted: 16 December 2016 / Published: 23 December 2016
Cited by 1 | PDF Full-text (10598 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
It is extremely difficult to predict the initiation time of cracking due to a large time spread in most cracking experiments. Thus, probabilistic models, such as the Weibull distribution, are usually employed to model the initiation time of cracking. Therefore, the parameters of
[...] Read more.
It is extremely difficult to predict the initiation time of cracking due to a large time spread in most cracking experiments. Thus, probabilistic models, such as the Weibull distribution, are usually employed to model the initiation time of cracking. Therefore, the parameters of the Weibull distribution are estimated from data collected from a cracking test. However, although the development of a reliable cracking model under ideal experimental conditions (e.g., a large number of specimens and narrow censoring intervals) could be achieved in principle, it is not straightforward to quantitatively assess the effects of the ideal experimental conditions on model estimation uncertainty. The present study investigated the effects of key experimental conditions, including the time-dependent effect of the censoring interval length, on the estimation uncertainties of the Weibull parameters through Monte Carlo simulations. The simulation results provided quantified estimation uncertainties of Weibull parameters in various cracking test conditions. Hence, it is expected that the results of this study can offer some insight for experimenters developing a probabilistic crack initiation model by performing experiments. Full article
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Open AccessArticle Signal Construction-Based Dispersion Compensation of Lamb Waves Considering Signal Waveform and Amplitude Spectrum Preservation
Materials 2017, 10(1), 4; https://doi.org/10.3390/ma10010004
Received: 13 September 2016 / Revised: 13 December 2016 / Accepted: 19 December 2016 / Published: 23 December 2016
Cited by 4 | PDF Full-text (8727 KB) | HTML Full-text | XML Full-text
Abstract
The results of Lamb wave identification for the aerospace structures could be easily affected by the nonlinear-dispersion characteristics. In this paper, dispersion compensation of Lamb waves is of particular concern. Compared with the similar research works on the traditional signal domain transform methods,
[...] Read more.
The results of Lamb wave identification for the aerospace structures could be easily affected by the nonlinear-dispersion characteristics. In this paper, dispersion compensation of Lamb waves is of particular concern. Compared with the similar research works on the traditional signal domain transform methods, this study is based on signal construction from the viewpoint of nonlinear wavenumber linearization. Two compensation methods of linearly-dispersive signal construction (LDSC) and non-dispersive signal construction (NDSC) are proposed. Furthermore, to improve the compensation effect, the influence of the signal construction process on the other crucial signal properties, including the signal waveform and amplitude spectrum, is considered during the investigation. The linear-dispersion and non-dispersion effects are firstly analyzed. Then, after the basic signal construction principle is explored, the numerical realization of LDSC and NDSC is discussed, in which the signal waveform and amplitude spectrum preservation is especially regarded. Subsequently, associated with the delay-and-sum algorithm, LDSC or NDSC is employed for high spatial resolution damage imaging, so that the adjacent multi-damage or quantitative imaging capacity of Lamb waves can be strengthened. To verify the proposed signal construction and damage imaging methods, the experimental and numerical validation is finally arranged on the aluminum plates. Full article
(This article belongs to the Special Issue Structural Health Monitoring for Aerospace Applications 2017)
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Open AccessArticle Quantification of the Service Life Extension and Environmental Benefit of Chloride Exposed Self-Healing Concrete
Materials 2017, 10(1), 5; https://doi.org/10.3390/ma10010005
Received: 14 November 2016 / Revised: 2 December 2016 / Accepted: 16 December 2016 / Published: 23 December 2016
Cited by 1 | PDF Full-text (2045 KB) | HTML Full-text | XML Full-text
Abstract
Formation of cracks impairs the durability of concrete elements. Corrosion inducing substances, such as chlorides, can enter the matrix through these cracks and cause steel reinforcement corrosion and concrete degradation. Self-repair of concrete cracks is an innovative technique which has been studied extensively
[...] Read more.
Formation of cracks impairs the durability of concrete elements. Corrosion inducing substances, such as chlorides, can enter the matrix through these cracks and cause steel reinforcement corrosion and concrete degradation. Self-repair of concrete cracks is an innovative technique which has been studied extensively during the past decade and which may help to increase the sustainability of concrete. However, the experiments conducted until now did not allow for an assessment of the service life extension possible with self-healing concrete in comparison with traditional (cracked) concrete. In this research, a service life prediction of self-healing concrete was done based on input from chloride diffusion tests. Self-healing of cracks with encapsulated polyurethane precursor formed a partial barrier against immediate ingress of chlorides through the cracks. Application of self-healing concrete was able to reduce the chloride concentration in a cracked zone by 75% or more. As a result, service life of steel reinforced self-healing concrete slabs in marine environments could amount to 60–94 years as opposed to only seven years for ordinary (cracked) concrete. Subsequent life cycle assessment calculations indicated important environmental benefits (56%–75%) for the ten CML-IA (Center of Environmental Science of Leiden University–Impact Assessment) baseline impact indicators which are mainly induced by the achievable service life extension. Full article
(This article belongs to the Special Issue Self-Healing Concrete)
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Open AccessArticle Concrete Cracking Prediction Including the Filling Proportion of Strand Corrosion Products
Materials 2017, 10(1), 6; https://doi.org/10.3390/ma10010006
Received: 21 October 2016 / Revised: 1 December 2016 / Accepted: 20 December 2016 / Published: 23 December 2016
Cited by 1 | PDF Full-text (11082 KB) | HTML Full-text | XML Full-text
Abstract
The filling of strand corrosion products during concrete crack propagation is investigated experimentally in the present paper. The effects of stirrups on the filling of corrosion products and concrete cracking are clarified. A prediction model of crack width is developed incorporating the filling
[...] Read more.
The filling of strand corrosion products during concrete crack propagation is investigated experimentally in the present paper. The effects of stirrups on the filling of corrosion products and concrete cracking are clarified. A prediction model of crack width is developed incorporating the filling proportion of corrosion products and the twisting shape of the strand. Experimental data on cracking angle, crack width, and corrosion loss obtained from accelerated corrosion tests of concrete beams are presented. The proposed model is verified by experimental data. Results show that the filling extent of corrosion products varies with crack propagation. The rust filling extent increases with the propagating crack until a critical width. Beyond the critical width, the rust-filling extent remains stable. Using stirrups can decrease the critical crack width. Stirrups can restrict crack propagation and reduce the rust filling. The tangent of the cracking angle increases with increasing corrosion loss. The prediction of corrosion-induced crack is sensitive to the rust-filling extent. Full article
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Open AccessArticle Dysprosium Acetylacetonato Single-Molecule Magnet Encapsulated in Carbon Nanotubes
Materials 2017, 10(1), 7; https://doi.org/10.3390/ma10010007
Received: 25 October 2016 / Revised: 9 December 2016 / Accepted: 20 December 2016 / Published: 23 December 2016
Cited by 2 | PDF Full-text (2053 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Dy single-molecule magnets (SMMs), which have several potential uses in a variety of applications, such as quantum computing, were encapsulated in multi-walled carbon nanotubes (MWCNTs) by using a capillary method. Encapsulation was confirmed by using transmission electron microscopy (TEM). In alternating current magnetic
[...] Read more.
Dy single-molecule magnets (SMMs), which have several potential uses in a variety of applications, such as quantum computing, were encapsulated in multi-walled carbon nanotubes (MWCNTs) by using a capillary method. Encapsulation was confirmed by using transmission electron microscopy (TEM). In alternating current magnetic measurements, the magnetic susceptibilities of the Dy acetylacetonato complexes showed clear frequency dependence even inside the MWCNTs, meaning that this hybrid can be used as magnetic materials in devices. Full article
(This article belongs to the Special Issue Advances in Molecular Magnets and related Phenomena)
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Open AccessArticle Comparison of Maraging Steel Micro- and Nanostructure Produced Conventionally and by Laser Additive Manufacturing
Materials 2017, 10(1), 8; https://doi.org/10.3390/ma10010008
Received: 1 December 2016 / Revised: 16 December 2016 / Accepted: 20 December 2016 / Published: 24 December 2016
Cited by 5 | PDF Full-text (12056 KB) | HTML Full-text | XML Full-text
Abstract
Maraging steels are used to produce tools by Additive Manufacturing (AM) methods such as Laser Metal Deposition (LMD) and Selective Laser Melting (SLM). Although it is well established that dense parts can be produced by AM, the influence of the AM process on
[...] Read more.
Maraging steels are used to produce tools by Additive Manufacturing (AM) methods such as Laser Metal Deposition (LMD) and Selective Laser Melting (SLM). Although it is well established that dense parts can be produced by AM, the influence of the AM process on the microstructure—in particular the content of retained and reversed austenite as well as the nanostructure, especially the precipitate density and chemistry, are not yet explored. Here, we study these features using microhardness measurements, Optical Microscopy, Electron Backscatter Diffraction (EBSD), Energy Dispersive Spectroscopy (EDS), and Atom Probe Tomography (APT) in the as-produced state and during ageing heat treatment. We find that due to microsegregation, retained austenite exists in the as-LMD- and as-SLM-produced states but not in the conventionally-produced material. The hardness in the as-LMD-produced state is higher than in the conventionally and SLM-produced materials, however, not in the uppermost layers. By APT, it is confirmed that this is due to early stages of precipitation induced by the cyclic re-heating upon further deposition—i.e., the intrinsic heat treatment associated with LMD. In the peak-aged state, which is reached after a similar time in all materials, the hardness of SLM- and LMD-produced material is slightly lower than in conventionally-produced material due to the presence of retained austenite and reversed austenite formed during ageing. Full article
(This article belongs to the Special Issue Metals for Additive Manufacturing)
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Open AccessArticle A Comprehensive Study of Photorefractive Properties in Poly(ethylene glycol) Dimethacrylate— Ionic Liquid Composites
Materials 2017, 10(1), 9; https://doi.org/10.3390/ma10010009
Received: 28 October 2016 / Revised: 11 December 2016 / Accepted: 19 December 2016 / Published: 24 December 2016
Cited by 2 | PDF Full-text (5020 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
A detailed investigation of the recording, as well as the readout of transmission gratings in composites of poly(ethylene glycol) dimethacrylate (PEGDMA) and ionic liquids is presented. Gratings with a period of about 5.8 micrometers were recorded using a two-wave mixing technique with a
[...] Read more.
A detailed investigation of the recording, as well as the readout of transmission gratings in composites of poly(ethylene glycol) dimethacrylate (PEGDMA) and ionic liquids is presented. Gratings with a period of about 5.8 micrometers were recorded using a two-wave mixing technique with a coherent laser beam of a 355-nm wavelength. A series of samples with grating thicknesses d 0 = 10 150 micrometers, each for two different exposure times, was prepared. The recording kinetics, as well as the post-exposure properties of the gratings were monitored by diffracting a low intensity probe beam at a wavelength of 633 nm for Bragg incidence. To obtain a complete characterization, two-beam coupling experiments were conducted to clarify the type and the strength of the recorded gratings. Finally, the diffraction efficiency was measured as a function of the readout angle at different post-exposure times. We found that, depending on the parameters, different grating types (pure phase and/or mixed) are generated, and at elevated thicknesses, strong light-induced scattering develops. The measured angular dependence of the diffraction efficiency can be fitted using a five-wave coupling theory assuming an attenuation of the gratings along the thickness. For grating thicknesses larger than 85 microns, light-induced scattering becomes increasingly important. The latter is an obstacle for recording thicker holograms, as it destroys the recording interference pattern with increasing sample depth. The obtained results are valuable in particular when considering PEGDMA-ionic liquid composites in the synthesis of advanced polymer composites for applications, such as biomaterials, conductive polymers and holographic storage materials. Full article
(This article belongs to the Section Advanced Composites)
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Open AccessArticle Simulation-Aided Design of Tubular Polymeric Capsules for Self-Healing Concrete
Materials 2017, 10(1), 10; https://doi.org/10.3390/ma10010010
Received: 15 November 2016 / Revised: 17 December 2016 / Accepted: 21 December 2016 / Published: 24 December 2016
Cited by 3 | PDF Full-text (4668 KB) | HTML Full-text | XML Full-text
Abstract
Polymeric capsules can have an advantage over glass capsules used up to now as proof-of-concept carriers in self-healing concrete. They allow easier processing and afford the possibility to fine tune their mechanical properties. Out of the multiple requirements for capsules used in this
[...] Read more.
Polymeric capsules can have an advantage over glass capsules used up to now as proof-of-concept carriers in self-healing concrete. They allow easier processing and afford the possibility to fine tune their mechanical properties. Out of the multiple requirements for capsules used in this context, the capability of rupturing when crossed by a crack in concrete of a typical size is one of the most relevant, as without it no healing agent is released into the crack. This study assessed the fitness of five types of polymeric capsules to fulfill this requirement by using a numerical model to screen the best performing ones and verifying their fitness with experimental methods. Capsules made of a specific type of poly(methyl methacrylate) (PMMA) were considered fit for the intended application, rupturing at average crack sizes of 69 and 128 μm, respectively for a wall thickness of ~0.3 and ~0.7 mm. Thicker walls were considered unfit, as they ruptured for crack sizes much higher than 100 μm. Other types of PMMA used and polylactic acid were equally unfit for the same reason. There was overall good fitting between model output and experimental results and an elongation at break of 1.5% is recommended regarding polymers for this application. Full article
(This article belongs to the Special Issue Self-Healing Concrete)
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Open AccessArticle Effects of Alloying Element Ca on the Corrosion Behavior and Bioactivity of Anodic Films Formed on AM60 Mg Alloys
Materials 2017, 10(1), 11; https://doi.org/10.3390/ma10010011
Received: 18 November 2016 / Revised: 12 December 2016 / Accepted: 16 December 2016 / Published: 26 December 2016
Cited by 4 | PDF Full-text (8219 KB) | HTML Full-text | XML Full-text
Abstract
Effects of alloying element Ca on the corrosion behavior and bioactivity of films formed by plasma electrolytic oxidation (PEO) on AM60 alloys were investigated. The corrosion behavior was studied by conducting electrochemical tests in 0.9% NaCl solution while the bioactivity was evaluated by
[...] Read more.
Effects of alloying element Ca on the corrosion behavior and bioactivity of films formed by plasma electrolytic oxidation (PEO) on AM60 alloys were investigated. The corrosion behavior was studied by conducting electrochemical tests in 0.9% NaCl solution while the bioactivity was evaluated by soaking the specimens in simulated body fluid (SBF). Under identical anodization conditions, the PEO film thicknesses increased with increasing Ca content in the alloys, which enhanced the corrosion resistance in NaCl solution. Thicker apatite layers grew on the PEO films of Ca-containing alloys because Ca was incorporated into the PEO film and because Ca was present in the alloys. Improvement of corrosion resistance and bioactivity of the PEO-coated AM60 by alloying with Ca may be beneficial for biodegradable implant applications. Full article
(This article belongs to the Special Issue Calcium Phosphate in Biomedical Applications)
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Open AccessArticle Optically Clear and Resilient Free-Form µ-Optics 3D-Printed via Ultrafast Laser Lithography
Materials 2017, 10(1), 12; https://doi.org/10.3390/ma10010012
Received: 31 October 2016 / Accepted: 20 December 2016 / Published: 2 January 2017
Cited by 17 | PDF Full-text (10651 KB) | HTML Full-text | XML Full-text
Abstract
We introduce optically clear and resilient free-form micro-optical components of pure (non-photosensitized) organic-inorganic SZ2080 material made by femtosecond 3D laser lithography (3DLL). This is advantageous for rapid printing of 3D micro-/nano-optics, including their integration directly onto optical fibers. A systematic study of the
[...] Read more.
We introduce optically clear and resilient free-form micro-optical components of pure (non-photosensitized) organic-inorganic SZ2080 material made by femtosecond 3D laser lithography (3DLL). This is advantageous for rapid printing of 3D micro-/nano-optics, including their integration directly onto optical fibers. A systematic study of the fabrication peculiarities and quality of resultant structures is performed. Comparison of microlens resiliency to continuous wave (CW) and femtosecond pulsed exposure is determined. Experimental results prove that pure SZ2080 is ∼20 fold more resistant to high irradiance as compared with standard lithographic material (SU8) and can sustain up to 1.91 GW/cm2 intensity. 3DLL is a promising manufacturing approach for high-intensity micro-optics for emerging fields in astro-photonics and atto-second pulse generation. Additionally, pyrolysis is employed to homogeneously shrink structures up to 40% by removing organic SZ2080 constituents. This opens a promising route towards downscaling photonic lattices and the creation of mechanically robust glass-ceramic microstructures. Full article
(This article belongs to the Special Issue Ultrafast Laser-Based Manufacturing)
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Open AccessArticle Numerical Simulation on Seismic Response of the Filled Joint under High Amplitude Stress Waves Using Finite-Discrete Element Method (FDEM)
Materials 2017, 10(1), 13; https://doi.org/10.3390/ma10010013
Received: 31 October 2016 / Revised: 16 December 2016 / Accepted: 18 December 2016 / Published: 27 December 2016
Cited by 3 | PDF Full-text (5978 KB) | HTML Full-text | XML Full-text
Abstract
This paper numerically investigates the seismic response of the filled joint under high amplitude stress waves using the combined finite-discrete element method (FDEM). A thin layer of independent polygonal particles are used to simulate the joint fillings. Each particle is meshed using the
[...] Read more.
This paper numerically investigates the seismic response of the filled joint under high amplitude stress waves using the combined finite-discrete element method (FDEM). A thin layer of independent polygonal particles are used to simulate the joint fillings. Each particle is meshed using the Delaunay triangulation scheme and can be crushed when the load exceeds its strength. The propagation of the 1D longitude wave through a single filled joint is studied, considering the influences of the joint thickness and the characteristics of the incident wave, such as the amplitude and frequency. The results show that the filled particles under high amplitude stress waves mainly experience three deformation stages: (i) initial compaction stage; (ii) crushing stage; and (iii) crushing and compaction stage. In the initial compaction stage and crushing and compaction stage, compaction dominates the mechanical behavior of the joint, and the particle area distribution curve varies little. In these stages, the transmission coefficient increases with the increase of the amplitude, i.e., peak particle velocity (PPV), of the incident wave. On the other hand, in the crushing stage, particle crushing plays the dominant role. The particle size distribution curve changes abruptly with the PPV due to the fragments created by the crushing process. This process consumes part of wave energy and reduces the stiffness of the filled joint. The transmission coefficient decreases with increasing PPV in this stage because of the increased amount of energy consumed by crushing. Moreover, with the increase of the frequency of the incident wave, the transmission coefficient decreases and fewer particles can be crushed. Under the same incident wave, the transmission coefficient decreases when the filled thickness increases and the filled particles become more difficult to be crushed. Full article
(This article belongs to the Special Issue Granular Materials)
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Open AccessArticle Tuneable Giant Magnetocaloric Effect in (Mn,Fe)2(P,Si) Materials by Co-B and Ni-B Co-Doping
Materials 2017, 10(1), 14; https://doi.org/10.3390/ma10010014
Received: 25 October 2016 / Revised: 5 December 2016 / Accepted: 15 December 2016 / Published: 27 December 2016
Cited by 5 | PDF Full-text (2012 KB) | HTML Full-text | XML Full-text
Abstract
The influence of Co (Ni) and B co-doping on the structural, magnetic and magnetocaloric properties of (Mn,Fe)2(P,Si) compounds is investigated by X-ray diffraction (XRD), differential scanning calorimetry, magnetic and direct temperature change measurements. It is found that Co (Ni) and B
[...] Read more.
The influence of Co (Ni) and B co-doping on the structural, magnetic and magnetocaloric properties of (Mn,Fe) 2 (P,Si) compounds is investigated by X-ray diffraction (XRD), differential scanning calorimetry, magnetic and direct temperature change measurements. It is found that Co (Ni) and B co-doping is an effective approach to tune both the Curie temperature and the thermal hysteresis of (Mn,Fe) 2 (P,Si) materials without losing either the giant magnetocaloric effect or the positive effect of the B substitution on the mechanical stability. An increase in B concentration leads to a rapid decrease in thermal hysteresis, while an increase in the Co or Ni concentration hardly changes the thermal hysteresis of the (Mn,Fe) 2 (P,Si) compounds. However, the Curie temperature decreases slowly as a function of the Co or Ni content, while it increases dramatically for increasing B concentration. Hence, the co-substitution of Fe and P by Co (Ni) and B, respectively, offers a new control parameter to adjust the Curie temperature and reduce the thermal hysteresis of the (Mn,Fe) 2 (P,Si) materials. Full article
(This article belongs to the Section Energy Materials)
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Open AccessCommunication Enhanced Electrocatalytic Activity for Water Splitting on NiO/Ni/Carbon Fiber Paper
Materials 2017, 10(1), 15; https://doi.org/10.3390/ma10010015
Received: 3 November 2016 / Revised: 20 December 2016 / Accepted: 22 December 2016 / Published: 28 December 2016
Cited by 5 | PDF Full-text (2198 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Large-scale growth of low-cost, efficient, and durable non-noble metal-based electrocatalysts for water splitting is crucial for future renewable energy systems. Atomic layer deposition (ALD) provides a promising route for depositing uniform thin coatings of electrocatalysts, which are useful in many technologies, including the
[...] Read more.
Large-scale growth of low-cost, efficient, and durable non-noble metal-based electrocatalysts for water splitting is crucial for future renewable energy systems. Atomic layer deposition (ALD) provides a promising route for depositing uniform thin coatings of electrocatalysts, which are useful in many technologies, including the splitting of water. In this communication, we report the growth of a NiO/Ni catalyst directly on carbon fiber paper by atomic layer deposition and report subsequent reduction and oxidation annealing treatments. The 10–20 nm NiO/Ni nanoparticle catalysts can reach a current density of 10 mA·cm−2 at an overpotential of 189 mV for hydrogen evolution reactions and 257 mV for oxygen evolution reactions with high stability. We further successfully achieved a water splitting current density of 10 mA·cm−2 at 1.78 V using a typical NiO/Ni coated carbon fiber paper two-electrode setup. The results suggest that nanoparticulate NiO/Ni is an active, stable, and noble-metal-free electrocatalyst, which facilitates a method for future water splitting applications. Full article
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Open AccessArticle Phase Equilibria and Magnetic Phases in the Ce-Fe-Co-B System
Materials 2017, 10(1), 16; https://doi.org/10.3390/ma10010016
Received: 3 November 2016 / Revised: 2 December 2016 / Accepted: 20 December 2016 / Published: 28 December 2016
Cited by 3 | PDF Full-text (16006 KB) | HTML Full-text | XML Full-text
Abstract
Ce-Fe-Co-B is a promising system for permanent magnets. A high-throughput screening method combining diffusion couples, key alloys, Scanning Electron Microscope/Wavelength Dispersive X-ray Spectroscope (SEM/WDS), and Magnetic Force Microscope (MFM) is used in this research to understand the phase equilibria and to explore promising
[...] Read more.
Ce-Fe-Co-B is a promising system for permanent magnets. A high-throughput screening method combining diffusion couples, key alloys, Scanning Electron Microscope/Wavelength Dispersive X-ray Spectroscope (SEM/WDS), and Magnetic Force Microscope (MFM) is used in this research to understand the phase equilibria and to explore promising magnetic phases in this system. Three magnetic phases were detected and their homogeneity ranges were determined at 900 °C, which were presented by the formulae: Ce2Fe14−xCoxB (0 ≤ x ≤ 4.76), CeCo4−xFexB (0 ≤ x ≤ 3.18), and Ce3Co11−x FexB4 (0 ≤ x ≤ 6.66). The phase relations among the magnetic phases in this system have been studied. Ce2(Fe, Co)14B appears to have stronger magnetization than Ce(Co, Fe)4B and Ce3(Co, Fe)11B4 from MFM analysis when comparing the magnetic interactions of selected key alloys. Also, a non-magnetic CeCo12−xFexB6 (0 ≤ x ≤ 8.74) phase was detected in this system. A boron-rich solid solution with Ce13FexCoyB45 (32 ≤ x ≤ 39, 3 ≤ y ≤ 10) chemical composition was also observed. However, the crystal structure of this phase could not be found in the literature. Moreover, ternary solid solutions ε1 (Ce2Fe17−xCox (0 ≤ x ≤ 12.35)) and ε2 (Ce2Co17−xFex (0 ≤ x ≤ 3.57)) were found to form between Ce2Fe17 and Ce2Co17 in the Ce-Fe-Co ternary system at 900 °C. Full article
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Open AccessArticle The Effect of Bisphasic Calcium Phosphate Block Bone Graft Materials with Polysaccharides on Bone Regeneration
Materials 2017, 10(1), 17; https://doi.org/10.3390/ma10010017
Received: 29 September 2016 / Revised: 1 December 2016 / Accepted: 6 December 2016 / Published: 1 January 2017
Cited by 4 | PDF Full-text (13135 KB) | HTML Full-text | XML Full-text
Abstract
In this study, bisphasic calcium phosphate (BCP) and two types of polysaccharide, carboxymethyl cellulose (CMC) and hyaluronic acid (HyA), were used to fabricate composite block bone grafts, and their physical and biological features and performances were compared and evaluated in vitro and in
[...] Read more.
In this study, bisphasic calcium phosphate (BCP) and two types of polysaccharide, carboxymethyl cellulose (CMC) and hyaluronic acid (HyA), were used to fabricate composite block bone grafts, and their physical and biological features and performances were compared and evaluated in vitro and in vivo. Specimens of the following were prepared as 6 mm diameter, 2 mm thick discs; BPC mixed with CMC (the BCP/CMC group), BCP mixed with crosslinked CMC (the BCP/c-CMC group) and BCP mixed with HyA (the BCP/HyA group) and a control group (specimens were prepared using particle type BCP). A scanning electron microscope study, a compressive strength analysis, and a cytotoxicity assessment were conducted. Graft materials were implanted in each of four circular defects of 6 mm diameter in calvarial bone in seven rabbits. Animals were sacrificed after four weeks for micro-CT and histomorphometric analyses, and the findings obtained were used to calculate new bone volumes (mm3) and area percentages (%). It was found that these two values were significantly higher in the BCP/c-CMC group than in the other three groups (p < 0.05). Within the limitations of this study, BCP composite block bone graft material incorporating crosslinked CMC has potential utility when bone augmentation is needed. Full article
(This article belongs to the Section Biomaterials)
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Open AccessCommunication Mechanical Fatigue Behavior of Flexible Printed Organic Thin-Film Transistors under Applied Strain
Materials 2017, 10(1), 18; https://doi.org/10.3390/ma10010018
Received: 12 October 2016 / Revised: 28 November 2016 / Accepted: 16 December 2016 / Published: 28 December 2016
Cited by 1 | PDF Full-text (3303 KB) | HTML Full-text | XML Full-text
Abstract
We report on the mechanical fatigue behavior of printed, organic, thin-film transistors (OTFTs) based on a polymer semiconductor, investigated by repeatedly applying strain to the flexible OTFT devices and assessing their electrical characteristics after 60,000 bending cycles. As part of our investigation, we
[...] Read more.
We report on the mechanical fatigue behavior of printed, organic, thin-film transistors (OTFTs) based on a polymer semiconductor, investigated by repeatedly applying strain to the flexible OTFT devices and assessing their electrical characteristics after 60,000 bending cycles. As part of our investigation, we established that the rates of reduction in source/drain currents in the OTFT device depended on bending directions. Our improved understanding of the mechanical fatigue behavior of the flexible printed OTFT devices provides valuable insights into their employment in practical flexible electronics applications. Full article
(This article belongs to the Special Issue Advances in Bendable and Soft Material Film)
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Open AccessArticle Microstructural Evolution of Dy2O3-TiO2 Powder Mixtures during Ball Milling and Post-Milled Annealing
Materials 2017, 10(1), 19; https://doi.org/10.3390/ma10010019
Received: 30 October 2016 / Revised: 21 December 2016 / Accepted: 23 December 2016 / Published: 28 December 2016
Cited by 2 | PDF Full-text (4585 KB) | HTML Full-text | XML Full-text
Abstract
The microstructural evolution of Dy2O3-TiO2 powder mixtures during ball milling and post-milled annealing was investigated using XRD, SEM, TEM, and DSC. At high ball-milling rotation speeds, the mixtures were fined, homogenized, nanocrystallized, and later completely amorphized, and the
[...] Read more.
The microstructural evolution of Dy2O3-TiO2 powder mixtures during ball milling and post-milled annealing was investigated using XRD, SEM, TEM, and DSC. At high ball-milling rotation speeds, the mixtures were fined, homogenized, nanocrystallized, and later completely amorphized, and the transformation of Dy2O3 from the cubic to the monoclinic crystal structure was observed. The amorphous transformation resulted from monoclinic Dy2O3, not from cubic Dy2O3. However, at low ball-milling rotation speeds, the mixtures were only fined and homogenized. An intermediate phase with a similar crystal structure to that of cubic Dy2TiO5 was detected in the amorphous mixtures annealed from 800 to 1000 °C, which was a metastable phase that transformed to orthorhombic Dy2TiO5 when the annealing temperature was above 1050 °C. However, at the same annealing temperatures, pyrochlore Dy2Ti2O7 initially formed and subsequently reacted with the remaining Dy2O3 to form orthorhombic Dy2TiO5 in the homogenous mixtures. The evolutionary mechanism of powder mixtures during ball milling and subsequent annealing was analyzed. Full article
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Open AccessArticle Experimental Study on Mechanical Properties and Porosity of Organic Microcapsules Based Self-Healing Cementitious Composite
Materials 2017, 10(1), 20; https://doi.org/10.3390/ma10010020
Received: 15 November 2016 / Revised: 14 December 2016 / Accepted: 16 December 2016 / Published: 1 January 2017
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Abstract
Encapsulation of healing agents embedded in a material matrix has become one of the major approaches for achieving self-healing function in cementitious materials in recent years. A novel type of microcapsules based self-healing cementitious composite was developed in Guangdong Provincial Key Laboratory of
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Encapsulation of healing agents embedded in a material matrix has become one of the major approaches for achieving self-healing function in cementitious materials in recent years. A novel type of microcapsules based self-healing cementitious composite was developed in Guangdong Provincial Key Laboratory of Durability for Marine Civil Engineering, Shenzhen University. In this study, both macro performance and the microstructure of the composite are investigated. The macro performance was evaluated by employing the compressive strength and the dynamic modulus, whereas the microstructure was represented by the pore structure parameters such as porosity, cumulative-pore volume, and average-pore diameter, which are significantly correlated to the pore-size distribution and the compressive strength. The results showed that both the compressive strength and the dynamic modulus, as well as the pore structure parameters such as porosity, cumulative-pore volume, and average-pore diameter of the specimen decrease to some extent with the amount of microcapsules. However, the self-healing rate and the recovery rate of the specimen performance and the pore-structure parameters increase with the amount of microcapsules. The results should confirm the self-healing function of microcapsules in the cementitious composite from macroscopic and microscopic viewpoints. Full article
(This article belongs to the Special Issue Self-Healing Concrete)
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Open AccessArticle Photovoltaic Performance Characterization of Textured Silicon Solar Cells Using Luminescent Down-Shifting Eu-Doped Phosphor Particles of Various Dimensions
Materials 2017, 10(1), 21; https://doi.org/10.3390/ma10010021
Received: 30 November 2016 / Revised: 20 December 2016 / Accepted: 26 December 2016 / Published: 1 January 2017
Cited by 4 | PDF Full-text (3926 KB) | HTML Full-text | XML Full-text
Abstract
This paper reports on efforts to enhance the photovoltaic performance of textured silicon solar cells through the application of a layer of Eu-doped silicate phosphor with particles of various dimensions using the spin-on film technique. We examined the surface profile and dimensions of
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This paper reports on efforts to enhance the photovoltaic performance of textured silicon solar cells through the application of a layer of Eu-doped silicate phosphor with particles of various dimensions using the spin-on film technique. We examined the surface profile and dimensions of the Eu-doped phosphors in the silicate layer using optical microscopy with J-image software. Optical reflectance, photoluminescence, and external quantum efficiency were used to characterize the luminescent downshifting (LDS) and light scattering of the Eu-doped silicate phosphor layer. Current density-voltage curves under AM 1.5G simulation were used to confirm the contribution of LDS and light scattering produced by phosphor particles of various dimensions. Experiment results reveal that smaller phosphor particles have a more pronounced effect on LDS and a slight shading of incident light. The application of small Eu-doped phosphor particles increased the conversion efficiency by 9.2% (from 12.56% to 13.86%), far exceeding the 5.6% improvement (from 12.54% to 13.32%) achieved by applying a 250 nm layer of SiO2 and the 4.5% improvement (from 12.37% to 12.98%) observed in cells with large Eu-doped phosphor particles. Full article
(This article belongs to the Special Issue Green Nanotechnology)
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Open AccessArticle Investigation on the Mechanism and Failure Mode of Laser Transmission Spot Welding Using PMMA Material for the Automotive Industry
Materials 2017, 10(1), 22; https://doi.org/10.3390/ma10010022
Received: 22 November 2016 / Revised: 16 December 2016 / Accepted: 26 December 2016 / Published: 1 January 2017
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Abstract
To satisfy the need of polymer connection in lightweight automobiles, a study on laser transmission spot welding using polymethyl methacrylate (PMMA) is conducted by using an Nd:YAG pulse laser. The influence of three variables, namely peak voltages, defocusing distances and the welding type
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To satisfy the need of polymer connection in lightweight automobiles, a study on laser transmission spot welding using polymethyl methacrylate (PMMA) is conducted by using an Nd:YAG pulse laser. The influence of three variables, namely peak voltages, defocusing distances and the welding type (type I (pulse frequency and the duration is 25 Hz, 0.6 s) and type II (pulse frequency and the duration is 5 Hz, 3 s)) to the welding quality was investigated. The result showed that, in the case of the same peak voltages and defocusing distances, the number of bubbles for type I was obviously more than type II. The failure mode of type I was the base plate fracture along the solder joint, and the connection strength of type I was greater than type II. The weld pool diameter:depth ratio for type I was significantly greater than type II. It could be seen that there was a certain relationship between the weld pool diameter:depth ratio and the welding strength. By the finite element simulation, the weld pool for type I was more slender than type II, which was approximately the same as the experimental results. Full article
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Open AccessArticle Determination of Material Strengths by Hydraulic Bulge Test
Materials 2017, 10(1), 23; https://doi.org/10.3390/ma10010023
Received: 18 November 2016 / Revised: 19 December 2016 / Accepted: 22 December 2016 / Published: 30 December 2016
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Abstract
The hydraulic bulge test (HBT) method is proposed to determine material tensile strengths. The basic idea of HBT is similar to the small punch test (SPT), but inspired by the manufacturing process of rupture discs—high-pressure hydraulic oil is used instead of punch to
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The hydraulic bulge test (HBT) method is proposed to determine material tensile strengths. The basic idea of HBT is similar to the small punch test (SPT), but inspired by the manufacturing process of rupture discs—high-pressure hydraulic oil is used instead of punch to cause specimen deformation. Compared with SPT method, the HBT method can avoid some of influence factors, such as punch dimension, punch material, and the friction between punch and specimen. A calculation procedure that is entirely based on theoretical derivation is proposed for estimate yield strength and ultimate tensile strength. Both conventional tensile tests and hydraulic bulge tests were carried out for several ferrous alloys, and the results showed that hydraulic bulge test results are reliable and accurate. Full article
(This article belongs to the Special Issue Selected Papers from SSTT2016)
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Open AccessArticle Effect of Intrinsic Stress on Structural and Optical Properties of Amorphous Si-Doped SnO2 Thin-Film
Materials 2017, 10(1), 24; https://doi.org/10.3390/ma10010024
Received: 13 September 2016 / Revised: 22 December 2016 / Accepted: 22 December 2016 / Published: 1 January 2017
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Abstract
The effect of intrinsic stress on the structure and physical properties of silicon-tin-oxide (STO) films have been investigated. Since a state of tensile stress is available in as-deposited films, the value of stress can be exponentially enhanced when the annealing temperature is increased.
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The effect of intrinsic stress on the structure and physical properties of silicon-tin-oxide (STO) films have been investigated. Since a state of tensile stress is available in as-deposited films, the value of stress can be exponentially enhanced when the annealing temperature is increased. The tensile stress is able to not only suppress the crystallization and widen the optical band gap of STO films, but also reduce defects of STO films. In this report, the good electrical performance of STO thin-film transistors (TFTs) can be obtained when annealing temperature is 450 °C. This includes a value of saturation mobility that can be reached at 6.7 cm2/Vs, a ratio of Ion/Ioff as 7.34 × 107, a steep sub-threshold swing at 0.625 V/decade, and a low trap density of 7.96 × 1011 eV−1·cm−2, respectively. Full article
(This article belongs to the Special Issue Oxide Semiconductor Thin-Film Transistor)
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Open AccessArticle Microwave-Assisted Polyol Synthesis of Water Dispersible Red-Emitting Eu3+-Modified Carbon Dots
Materials 2017, 10(1), 25; https://doi.org/10.3390/ma10010025
Received: 3 November 2016 / Revised: 13 December 2016 / Accepted: 21 December 2016 / Published: 29 December 2016
Cited by 1 | PDF Full-text (5485 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Eu3+-modified carbon dots (C-dots), 3–5 nm in diameter, were prepared, functionalized, and stabilized via a one-pot polyol synthesis. The role of Eu2+/Eu3+, the influence of O2 (oxidation) and H2O (hydrolysis), as well as the
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Eu3+-modified carbon dots (C-dots), 3–5 nm in diameter, were prepared, functionalized, and stabilized via a one-pot polyol synthesis. The role of Eu2+/Eu3+, the influence of O2 (oxidation) and H2O (hydrolysis), as well as the impact of the heating procedure (conventional resistance heating and microwave (MW) heating) were explored. With the reducing conditions of the polyol at the elevated temperature of synthesis (200–230 °C), first of all, Eu2+ was obtained resulting in the blue emission of the C-dots. Subsequent to O2-driven oxidation, Eu3+-modified, red-emitting C-dots were realized. However, the Eu3+ emission is rapidly quenched by water for C-dots prepared via conventional resistance heating. In contrast to the hydroxyl functionalization of conventionally-heated C-dots, MW-heating results in a carboxylate functionalization of the C-dots. Carboxylate-coordinated Eu3+, however, turned out as highly stable even in water. Based on this fundamental understanding of synthesis and material, in sum, a one-pot polyol approach is established that results in H2O-dispersable C-dots with intense red Eu3+-line-type emission. Full article
(This article belongs to the Section Advanced Composites)
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Open AccessArticle Novel Dental Adhesive with Biofilm-Regulating and Remineralization Capabilities
Materials 2017, 10(1), 26; https://doi.org/10.3390/ma10010026
Received: 7 November 2016 / Revised: 18 December 2016 / Accepted: 26 December 2016 / Published: 3 January 2017
Cited by 6 | PDF Full-text (6524 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
The mechanical properties and anti-caries effect of a novel anti-caries adhesive containing poly (amidoamine) dendrimer (PAMAM) and dimethylaminododecyl methacrylate (DMADDM) were investigated for the first time. Microtensile bond strength and surface charge density were measured for the novel anti-caries adhesives. Streptococcus mutans,
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The mechanical properties and anti-caries effect of a novel anti-caries adhesive containing poly (amidoamine) dendrimer (PAMAM) and dimethylaminododecyl methacrylate (DMADDM) were investigated for the first time. Microtensile bond strength and surface charge density were measured for the novel anti-caries adhesives. Streptococcus mutans, Streptococcus sanguinis, and Streptococcus gordonii were chosen to form three-species biofilms. Lactic acid assay, MTT (3-(4,5-Dimethyl-thiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay, exopolysaccharide staining and live/dead staining were performed to study anti-biofilm effect of the adhesive. The TaqMan realtime polymerase chain reaction was used to study the proportion change in three-species biofilms of different groups. The Scanning Electron Microscope (SEM) was used to observe the remineralization effect of PAMAM and DMADDM. The results showed that incorporating PAMAM and DMADDM into adhesive had no adverse effect on the dentin bond strength. The 1% PAMAM and 5% DMADDM adhesive group showed anti-biofilm properties and developed a healthier biofilm with a lower chance of inducing dental caries. Combination of 1% PAMAM and 5% DMADDM solution maintained remineralization capability on dentin, similar to that using 1% PAMAM alone. In conclusion, the adhesive containing PAMAM and DMADDM had strong antimicrobial properties and biological remineralization capabilities, and is promising for anti-caries clinical applications. Full article
(This article belongs to the Section Biomaterials)
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Open AccessArticle Influence of Porous Spherical-Shaped Hydroxyapatite on Mechanical Strength and Bioactive Function of Conventional Glass Ionomer Cement
Materials 2017, 10(1), 27; https://doi.org/10.3390/ma10010027
Received: 29 November 2016 / Revised: 23 December 2016 / Accepted: 26 December 2016 / Published: 3 January 2017
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Abstract
Glass-ionomer-cement (GIC) is helpful in Minimal Intervention Dentistry because it releases fluoride ions and is highly biocompatible. The aim of this study is to investigate the mechanisms by which hydroxyapatite (HAp) improves the mechanical strength and bioactive functioning of GIC when these materials
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Glass-ionomer-cement (GIC) is helpful in Minimal Intervention Dentistry because it releases fluoride ions and is highly biocompatible. The aim of this study is to investigate the mechanisms by which hydroxyapatite (HAp) improves the mechanical strength and bioactive functioning of GIC when these materials are combined to make apatite ionomer cement (AIC). A conventional GIC powder was mixed with porous, spherical-HAp particles (HApS), crystalline HAp (HAp200) or one of two types of cellulose. The micro-compressive strengths of the additive particles were measured, and various specimens were evaluated with regard to their compressive strengths (CS), fluoride release concentrations (fluoride electrode) and multi-element release concentrations. The AIC was found to release higher concentrations of fluoride (1.2 times) and strontium ions (1.5 times) compared to the control GIC. It was detected the more release of calcium originated from HApS than HAp200 in AIC. The CS of the AIC incorporating an optimum level of HAp was also significantly higher than that of the GIC. These results suggest that adding HAp can increase the release concentration of ions required for remineralization while maintaining the CS of the GIC. This effect does not result from a physical phenomenon, but rather from chemical reactions between the HAp and polyacrylic acid of GIC. Full article
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Open AccessArticle Mechanistic Characteristics of Surface Modified Organic Semiconductor g-C3N4 Nanotubes Alloyed with Titania
Materials 2017, 10(1), 28; https://doi.org/10.3390/ma10010028
Received: 8 November 2016 / Revised: 13 December 2016 / Accepted: 15 December 2016 / Published: 3 January 2017
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Abstract
The visible-light-driven photocatalytic degradation of Bisphenol A (BPA) was investigated using the binary composite of alkaline treated g-C3N4 (HT-g-C3N4) deposited over commercial TiO2 (Evonik Degussa GmbH, Essen, Germany). The existence and contribution of both TiO
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The visible-light-driven photocatalytic degradation of Bisphenol A (BPA) was investigated using the binary composite of alkaline treated g-C3N4 (HT-g-C3N4) deposited over commercial TiO2 (Evonik Degussa GmbH, Essen, Germany). The existence and contribution of both TiO2 and g-C3N4/HT-g-C3N4 in the composite was confirmed through various analytical techniques including powder X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), field emission scanning electron microscopy (FESEM), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), ultraviolet-visible diffuse reflectance spectra (UV-vis-DRS), and photoluminescence (PL) analysis. The results showed that the titania in the binary composite exhibited both pure rutile and anatase phases. The morphological analysis indicated that the spongy “morel-like” structure of g-C3N4 turned to nanotube form after alkaline hydrothermal treatment and thereby decreased the specific surface area of HT-g-C3N4. The low surface area of HT-g-C3N4 dominates its promising optical property and effective charge transfer, resulting in a deprived degradation efficiency of BPA two times lower than pure g-C3N4. The binary composite of HT-g-C3N4/TiO2 exhibited excellent degradation efficiency of BPA with 2.16 times higher than the pure HT-g-C3N4. The enhanced photocatalytic activity was mainly due to the promising optical band gap structure with heterojunction interface, favorable specific surface area, and good charge separation. Full article
(This article belongs to the Special Issue Enhancing the Photocatalytic Activity of TiO2 Photocatalysts)
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Open AccessArticle Reduction of Surface Roughness by Means of Laser Processing over Additive Manufacturing Metal Parts
Materials 2017, 10(1), 30; https://doi.org/10.3390/ma10010030
Received: 19 October 2016 / Revised: 20 December 2016 / Accepted: 27 December 2016 / Published: 31 December 2016
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Abstract
Optimization of processing parameters and exposure strategies is usually performed in additive manufacturing to set up the process; nevertheless, standards for roughness may not be evenly matched on a single complex part, since surface features depend on the building direction of the part.
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Optimization of processing parameters and exposure strategies is usually performed in additive manufacturing to set up the process; nevertheless, standards for roughness may not be evenly matched on a single complex part, since surface features depend on the building direction of the part. This paper aims to evaluate post processing treating via laser surface modification by means of scanning optics and beam wobbling to process metal parts resulting from selective laser melting of stainless steel in order to improve surface topography. The results are discussed in terms of roughness, geometry of the fusion zone in the cross-section, microstructural modification, and microhardness so as to assess the effects of laser post processing. The benefits of beam wobbling over linear scanning processing are shown, as heat effects in the base metal are proven to be lower. Full article
(This article belongs to the Section Manufacturing Processes and Systems)
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Open AccessArticle Numerical Prediction of the Mechanical Failure of the Intervertebral Disc under Complex Loading Conditions
Materials 2017, 10(1), 31; https://doi.org/10.3390/ma10010031
Received: 31 October 2016 / Revised: 6 December 2016 / Accepted: 20 December 2016 / Published: 3 January 2017
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Abstract
Finite element modeling has been widely used to simulate the mechanical behavior of the intervertebral disc. Previous models have been generally limited to the prediction of the disc behavior under simple loading conditions, thus neglecting its response to complex loads, which may induce
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Finite element modeling has been widely used to simulate the mechanical behavior of the intervertebral disc. Previous models have been generally limited to the prediction of the disc behavior under simple loading conditions, thus neglecting its response to complex loads, which may induce its failure. The aim of this study was to generate a finite element model of the ovine lumbar intervertebral disc, in which the annulus was characterized by an anisotropic hyperelastic formulation, and to use it to define which mechanical condition was unsafe for the disc. Based on published in vitro results, numerical analyses under combined flexion, lateral bending, and axial rotation with a magnitude double that of the physiological ones were performed. The simulations showed that flexion was the most unsafe load and an axial tensile stress greater than 10 MPa can cause disc failure. The numerical model here presented can be used to predict the failure of the disc under all loading conditions, which may support indications about the degree of safety of specific motions and daily activities, such as weight lifting. Full article
(This article belongs to the Special Issue Biomaterials and Tissue Biomechanics)
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Open AccessArticle Monitoring the Damage State of Fiber Reinforced Composites Using an FBG Network for Failure Prediction
Materials 2017, 10(1), 32; https://doi.org/10.3390/ma10010032
Received: 15 September 2016 / Revised: 16 December 2016 / Accepted: 20 December 2016 / Published: 3 January 2017
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Abstract
A structural health monitoring (SHM) study of biaxial glass fibre-reinforced epoxy matrix composites under a constant, high strain uniaxial fatigue loading is performed using fibre Bragg grating (FBG) optical sensors embedded in composites at various locations to monitor the evolution of local strains,
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A structural health monitoring (SHM) study of biaxial glass fibre-reinforced epoxy matrix composites under a constant, high strain uniaxial fatigue loading is performed using fibre Bragg grating (FBG) optical sensors embedded in composites at various locations to monitor the evolution of local strains, thereby understanding the damage mechanisms. Concurrently, the temperature changes of the samples during the fatigue test have also been monitored at the same locations. Close to fracture, significant variations in local temperatures and strains are observed, and it is shown that the variations in temperature and strain can be used to predict imminent fracture. It is noted that the latter information cannot be obtained using external strain gages, which underlines the importance of the tracking of local strains internally. Full article
(This article belongs to the Special Issue Advances in Structural Health Monitoring for Aerospace Structures)
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Open AccessArticle Physico-Chemical, In Vitro, and In Vivo Evaluation of a 3D Unidirectional Porous Hydroxyapatite Scaffold for Bone Regeneration
Materials 2017, 10(1), 33; https://doi.org/10.3390/ma10010033
Received: 8 November 2016 / Revised: 25 December 2016 / Accepted: 28 December 2016 / Published: 3 January 2017
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Abstract
The unidirectional porous hydroxyapatite HAp (UDPHAp) is a scaffold with continuous communicated pore structure in the axial direction. We evaluated and compared the ability of the UDPHAp as a three-dimensional (3D) bone tissue engineering scaffold to the interconnected calcium porous HAp ceramic (IP-CHA).
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The unidirectional porous hydroxyapatite HAp (UDPHAp) is a scaffold with continuous communicated pore structure in the axial direction. We evaluated and compared the ability of the UDPHAp as a three-dimensional (3D) bone tissue engineering scaffold to the interconnected calcium porous HAp ceramic (IP-CHA). To achieve this, we evaluated in vitro the compressive strength, controlled rhBMP-2 release behavior, adherent cell morphology, cell adhesion manner, and cell attachment of UDPHAp. As a further in vivo experiment, UDPHAp and IP-CHA with rhBMP-2 were transplanted into mouse calvarial defects to evaluate their bone-forming ability. The Results demonstrated that the maximum compressive strengths of the UDPHAp was 7.89 ± 1.23 MPa and higher than that of IP-CHA (1.92 ± 0.53 MPa) (p = 0.0039). However, the breaking energies were similar (8.99 ± 2.72 vs. 13.95 ± 5.69 mJ, p = 0.055). The UDPHAp released rhBMP-2 more gradually in vivo. Cells on the UDPHAp adhered tightly to the surface, which had grown deeply into the scaffolds. A significant increase in cell number on the UDPHAp was observed compared to the IP-CHA on day 8 (102,479 ± 34,391 vs. 32,372 ± 29,061 estimated cells per scaffold, p = 0.0495). In a mouse calvarial defect model, the percentages of new bone area (mature bone + trabecular bone) in the 2x field were 2.514% ± 1.224% for the IP-CHA group and 7.045% ± 2.055% for the UDPHAp group, and the percentage was significantly higher in the UDPHAp group (p = 0.0209). While maintaining the same strength as the IP-CHA, the UDPHAp with 84% porosity showed a high cell number, high cell invasiveness, and excellent bone formation. We believe the UDPHAp is an excellent material that can be applied to bone regenerative medicine. Full article
(This article belongs to the Special Issue Bioceramics 2016)
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Open AccessArticle Thermo-Mechanical Fatigue Crack Growth of RR1000
Materials 2017, 10(1), 34; https://doi.org/10.3390/ma10010034
Received: 21 June 2016 / Revised: 8 December 2016 / Accepted: 26 December 2016 / Published: 4 January 2017
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Abstract
Non-isothermal conditions during flight cycles have long led to the requirement for thermo-mechanical fatigue (TMF) evaluation of aerospace materials. However, the increased temperatures within the gas turbine engine have meant that the requirements for TMF testing now extend to disc alloys along with
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Non-isothermal conditions during flight cycles have long led to the requirement for thermo-mechanical fatigue (TMF) evaluation of aerospace materials. However, the increased temperatures within the gas turbine engine have meant that the requirements for TMF testing now extend to disc alloys along with blade materials. As such, fatigue crack growth rates are required to be evaluated under non-isothermal conditions along with the development of a detailed understanding of related failure mechanisms. In the current work, a TMF crack growth testing method has been developed utilising induction heating and direct current potential drop techniques for polycrystalline nickel-based superalloys, such as RR1000. Results have shown that in-phase (IP) testing produces accelerated crack growth rates compared with out-of-phase (OOP) due to increased temperature at peak stress and therefore increased time dependent crack growth. The ordering of the crack growth rates is supported by detailed fractographic analysis which shows intergranular crack growth in IP test specimens, and transgranular crack growth in 90° OOP and 180° OOP tests. Isothermal tests have also been carried out for comparison of crack growth rates at the point of peak stress in the TMF cycles. Full article
(This article belongs to the Section Energy Materials)
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Open AccessArticle Customized a Ti6Al4V Bone Plate for Complex Pelvic Fracture by Selective Laser Melting
Materials 2017, 10(1), 35; https://doi.org/10.3390/ma10010035
Received: 11 November 2016 / Revised: 16 December 2016 / Accepted: 29 December 2016 / Published: 4 January 2017
Cited by 6 | PDF Full-text (6018 KB) | HTML Full-text | XML Full-text
Abstract
In pelvic fracture operations, bone plate shaping is challenging and the operation time is long. To address this issue, a customized bone plate was designed and produced using selective laser melting (SLM) technology. The key steps of this study included designing the customized
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In pelvic fracture operations, bone plate shaping is challenging and the operation time is long. To address this issue, a customized bone plate was designed and produced using selective laser melting (SLM) technology. The key steps of this study included designing the customized bone plate, metal 3D printing, vacuum heat treatment, surface post-processing, operation rehearsal, and clinical application and evaluation. The joint surface of the bone plate was placed upwards with respect to the build platform to keep it away from the support and to improve the quality of the joint surface. Heat conduction was enhanced by adding a cone-type support beneath the bone plate to prevent low-quality fabrication due to poor heat conductivity of the Ti-6Al-4V powder. The residual stress was eliminated by exposing the SLM-fabricated titanium-alloy bone plate to a vacuum heat treatment. Results indicated that the bone plate has a hardness of HV1 360–HV1 390, an ultimate tensile strength of 1000–1100 MPa, yield strength of 900–950 MPa, and an elongation of 8%–10%. Pre-operative experiments and operation rehearsal were performed using the customized bone plate and the ABC-made pelvic model. Finally, the customized bone plate was clinically applied. The intraoperative C-arm and postoperative X-ray imaging results indicated that the customized bone plate matched well to the damaged pelvis. The customized bone plate fixed the broken bone and guides pelvis restoration while reducing operation time to about two hours. The customized bone plate eliminated the need for preoperative titanium plate pre-bending, thereby greatly reducing surgical wounds and operation time. Full article
(This article belongs to the Special Issue 3D Printing for Biomedical Engineering)
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Open AccessArticle A First Principles Study of H2 Adsorption on LaNiO3(001) Surfaces
Materials 2017, 10(1), 36; https://doi.org/10.3390/ma10010036
Received: 28 October 2016 / Revised: 30 December 2016 / Accepted: 31 December 2016 / Published: 5 January 2017
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Abstract
The adsorption of H2 on LaNiO3 was investigated using density functional theory (DFT) calculations. The adsorption sites, adsorption energy, and electronic structure of LaNiO3(001)/H2 systems were calculated and indicated through the calculated surface energy that the (001) surface
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The adsorption of H2 on LaNiO3 was investigated using density functional theory (DFT) calculations. The adsorption sites, adsorption energy, and electronic structure of LaNiO3(001)/H2 systems were calculated and indicated through the calculated surface energy that the (001) surface was the most stable surface. By looking at optimized structure, adsorption energy and dissociation energy, we found that there were three types of adsorption on the surface. First, H2 molecules completely dissociate and then tend to bind with the O atoms, forming two –OH bonds. Second, H2 molecules partially dissociate with the H atoms bonding to the same O atom to form one H2O molecule. These two types are chemical adsorption modes; however, the physical adsorption of H2 molecules can also occur. When analyzing the electron structure of the H2O molecule formed by the partial dissociation of the H2 molecule and the surface O atom, we found that the interaction between H2O and the (001) surface was weaker, thus, H2O was easier to separate from the surface to create an O vacancy. On the (001) surface, a supercell was constructed to accurately study the most stable adsorption site. The results from analyses of the charge population; electron localization function; and density of the states indicated that the dissociated H and O atoms form a typical covalent bond and that the interaction between the H2 molecule and surface is mainly due to the overlap-hybridization among the H 1s, O 2s, and O 2p states. Therefore, the conductivity of LaNiO3(001)/H2 is stronger after adsorption and furthermore, the conductivity of the LaNiO3 surface is better than that of the LaFeO3 surface. Full article
(This article belongs to the Section Energy Materials)
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Open AccessArticle ZnO/Cu2S/ZnO Multilayer Films: Structure Optimization and Its Detail Data for Applications on Photoelectric and Photocatalytic Properties
Materials 2017, 10(1), 37; https://doi.org/10.3390/ma10010037
Received: 10 November 2016 / Revised: 7 December 2016 / Accepted: 27 December 2016 / Published: 5 January 2017
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Abstract
Monolayer Cu2S and ZnO, and three kinds of complex films, Cu2S/ZnO, ZnO/Cu2S, and ZnO/Cu2S/ZnO, were deposited on glass substrates by means of radio frequency (RF) magnetron sputtering device. The impact of the thickness of ZnO
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Monolayer Cu2S and ZnO, and three kinds of complex films, Cu2S/ZnO, ZnO/Cu2S, and ZnO/Cu2S/ZnO, were deposited on glass substrates by means of radio frequency (RF) magnetron sputtering device. The impact of the thickness of ZnO and Cu2S on the whole transmittance, conductivity, and photocatalysis was investigated. The optical and electrical properties of the multilayer were studied by optical spectrometry and four point probes. Numerical simulation of the optical transmittance of the multilayer films has been carried out in order to guide the experimental work. The comprehensive performances of the multilayers as transparent conductive coatings were compared using the figure of merit. Compared with monolithic Cu2S and ZnO films, both the optical transmission property and photocatalytic performance of complex films such as Cu2S/ZnO and ZnO/Cu2S/ZnO change significantly. Full article
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Open AccessArticle Thermal Properties of the Mixed n-Octadecane/Cu Nanoparticle Nanofluids during Phase Transition: A Molecular Dynamics Study
Materials 2017, 10(1), 38; https://doi.org/10.3390/ma10010038
Received: 18 November 2016 / Revised: 27 December 2016 / Accepted: 30 December 2016 / Published: 5 January 2017
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Abstract
Paraffin based nanofluids are widely used as thermal energy storage materials and hold many applications in the energy industry. In this work, equilibrium and nonequilibrium molecular dynamics simulations are employed to study the thermal properties of the mixed nanofluids of n-octadecane and
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Paraffin based nanofluids are widely used as thermal energy storage materials and hold many applications in the energy industry. In this work, equilibrium and nonequilibrium molecular dynamics simulations are employed to study the thermal properties of the mixed nanofluids of n-octadecane and Cu nanoparticles during phase transition. Four different nanofluids systems with different mass ratios between the n-octadecane and Cu nanoparticles have been studied and the results show that Cu nanoparticles can improve the thermal properties of n-octadecane. The melting point, heat capacity and thermal conductivity of the mixed systems are decreased with the increasing of the mass ratio of n-octadecane. Full article
(This article belongs to the Special Issue Thermal Sciences and Thermodynamics of Materials)
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Open AccessArticle A Facile Pathway to Modify Cellulose Composite Film by Reducing Wettability and Improving Barrier towards Moisture
Materials 2017, 10(1), 39; https://doi.org/10.3390/ma10010039
Received: 8 November 2016 / Revised: 19 December 2016 / Accepted: 26 December 2016 / Published: 5 January 2017
PDF Full-text (2560 KB) | HTML Full-text | XML Full-text
Abstract
The hydrophilic property of cellulose is a key limiting factor for its wide application. Here, a novel solution impregnation pathway was developed to increase the hydrophobic properties of cellulose. When compared with the regenerated cellulose (RC), the composite films showed a decrease in
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The hydrophilic property of cellulose is a key limiting factor for its wide application. Here, a novel solution impregnation pathway was developed to increase the hydrophobic properties of cellulose. When compared with the regenerated cellulose (RC), the composite films showed a decrease in water uptake ability towards water vapor, and an increase of the water contact angle from 29° to 65° with increasing resin content in the composites, with only a slight change in the transmittance. Furthermore, the Young’s modulus value increased from 3.2 GPa (RC film) to 5.1 GPa (RCBEA50 film). The results indicated that the composites had combined the advantages of cellulose and biphenyl A epoxy acrylate prepolymer (BEA) resin. The presented method has great potential for the preparation of biocomposites with improved properties. The overall results suggest that composite films can be used as high-performance packaging materials. Full article
(This article belongs to the Special Issue Biobased Polymers for Packaging Applications)
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