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Materials, Volume 11, Issue 11 (November 2018)

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Open AccessArticle Multiscale Analysis of CFRP Laminates with MMF3 Criterion under Different Off-Axis Loading Conditions
Materials 2018, 11(11), 2255; https://doi.org/10.3390/ma11112255 (registering DOI)
Received: 12 October 2018 / Revised: 6 November 2018 / Accepted: 10 November 2018 / Published: 12 November 2018
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Abstract
A multiscale analysis strategy with physical modified-micromechanics of failure (MMF3) criterion was proposed to analyze the failure behaviors of carbon fiber reinforced plastic (CFRP) laminates. The quantitative relationship between the macro- and micro- stresses was determined considering two typical fiber distributions. Thermal residual
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A multiscale analysis strategy with physical modified-micromechanics of failure (MMF3) criterion was proposed to analyze the failure behaviors of carbon fiber reinforced plastic (CFRP) laminates. The quantitative relationship between the macro- and micro- stresses was determined considering two typical fiber distributions. Thermal residual stress was taken into account in the stress transformation. The failures were defined and the properties of damaged elements were degraded at the constituent level. The back-calculation method based on the iteration algorithm was proposed to determine the micro strength with macro mechanical tests. A series of off-axis loading tests were conducted to verify the established multiscale models. The predicted strength was also compared with the results using micromechanics of failure (MMF) criterion to present accuracy improvements. Thermal residual stress was found to affect the strength by contributing to the matrix damage status. Meanwhile, sensitivity analysis was provided for the matrix-dominant micro strength to investigate its physical meaning. Results suggest that the micro tensile and compressive strength of the matrix influenced the off-axis tensile and compressive strengths respectively, with relative large off-axis angles, while the micro shear strength of the matrix dominated when the off-axis angles were relative small. Full article
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Open AccessArticle Rapid Solar-Light Driven Superior Photocatalytic Degradation of Methylene Blue Using MoS2-ZnO Heterostructure Nanorods Photocatalyst
Materials 2018, 11(11), 2254; https://doi.org/10.3390/ma11112254 (registering DOI)
Received: 1 October 2018 / Revised: 3 November 2018 / Accepted: 6 November 2018 / Published: 12 November 2018
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Abstract
Herein, MoS2-ZnO heterostructure nanorods were hydrothermally synthesized and characterized in detail using several compositional, optical, and morphological techniques. The comprehensive characterizations show that the synthesized MoS2/ZnO heterostructure nanorods were composed of wurtzite hexagonal phase of ZnO and rhombohedral phase
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Herein, MoS2-ZnO heterostructure nanorods were hydrothermally synthesized and characterized in detail using several compositional, optical, and morphological techniques. The comprehensive characterizations show that the synthesized MoS2/ZnO heterostructure nanorods were composed of wurtzite hexagonal phase of ZnO and rhombohedral phase of MoS2. The synthesized MoS2/ZnO heterostructure nanorods were used as a potent photocatalyst for the decomposition of methylene blue (MB) dye under natural sunlight. The prepared MoS2/ZnO heterostructure nanorods exhibited ~97% removal of MB in the reaction time of 20 min with the catalyst amount of 0.15 g/L. The kinetic study revealed that the photocatalytic removal of MB was found to be in accordance with pseudo first-order reaction kinetics with an obtained rate constant of 0.16262 min−1. The tremendous photocatalytic performance of MoS2-ZnO heterostructure nanorods could be accredited to an effective charge transportation and inhibition in the recombination of photo-excited charge carriers at an interfacial heterojunction. The contribution of active species towards the decomposition of MB using MoS2-ZnO heterostructure nanorods was confirmed from scavenger study and terephthalic acid fluorescence technique. Full article
(This article belongs to the Special Issue Advanced Functional Nanomaterials and Their Applications)
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Open AccessArticle Electrolytic Surface Treatment for Improved Adhesion between Carbon Fibre and Polycarbonate
Materials 2018, 11(11), 2253; https://doi.org/10.3390/ma11112253 (registering DOI)
Received: 13 October 2018 / Revised: 31 October 2018 / Accepted: 6 November 2018 / Published: 12 November 2018
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Abstract
To achieve good mechanical properties of carbon fibre-reinforced polycarbonate composites, the fibre-matrix adhesion must be dialled to an optimum level. The electrolytic surface treatment of carbon fibres during their production is one of the possible means of adapting the surface characteristics of the
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To achieve good mechanical properties of carbon fibre-reinforced polycarbonate composites, the fibre-matrix adhesion must be dialled to an optimum level. The electrolytic surface treatment of carbon fibres during their production is one of the possible means of adapting the surface characteristics of the fibres. The production of a range of tailored fibres with varying surface treatments (adjusting the current, potential, and conductivity) was followed by contact angle, inverse gas chromatography and X-ray photoelectron spectroscopy measurements, which revealed a significant increase in polarity and hydroxyl, carboxyl, and nitrile groups on the fibre surface. Accordingly, an increase in the fibre-matrix interaction indicated by a higher interfacial shear strength was observed with the single fibre pull-out force-displacement curves. The statistical analysis identified the correlation between the process settings, fibre surface characteristics, and the performance of the fibres during single fibre pull-out testing. Full article
(This article belongs to the Special Issue Carbon Fibers and Their Composite Materials)
Open AccessArticle Effect of Mixture Variables on Durability for Alkali-Activated Slag Cementitious
Materials 2018, 11(11), 2252; https://doi.org/10.3390/ma11112252 (registering DOI)
Received: 16 October 2018 / Revised: 8 November 2018 / Accepted: 12 November 2018 / Published: 12 November 2018
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Abstract
In this study, the influence of three mixture variables named Sand/Aggregate ratio, Liquid/Binder ratio, and Paste/Aggregate ratio on the cementitious properties were studied. The durability of cementitious including absorption, absorption rate, resistivity, rapid chloride permeability index, and carbonation rate were examined. Results showed
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In this study, the influence of three mixture variables named Sand/Aggregate ratio, Liquid/Binder ratio, and Paste/Aggregate ratio on the cementitious properties were studied. The durability of cementitious including absorption, absorption rate, resistivity, rapid chloride permeability index, and carbonation rate were examined. Results showed that the alkali-activated slag cementitious has superior durability. The trends of influences on the composites properties for these three mixture variables are similar to those for the ordinary Portland cement concrete. It means that the experiences for making the ordinary Portland cement concrete should be able to be used for the alkali-activated slag cementitious. This paper also provides a lot of data for the alkali-activated slag cementitious for future development of the mix design. Full article
(This article belongs to the Special Issue Selected Papers from IMETI2018)
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Open AccessArticle Preparation of LiFePO4/C Cathode Materials via a Green Synthesis Route for Lithium-Ion Battery Applications
Materials 2018, 11(11), 2251; https://doi.org/10.3390/ma11112251 (registering DOI)
Received: 12 October 2018 / Revised: 8 November 2018 / Accepted: 9 November 2018 / Published: 12 November 2018
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Abstract
In this work, LiFePO4/C composite were synthesized via a green route by using Iron (III) oxide (Fe2O3) nanoparticles, Lithium carbonate (Li2CO3), glucose powder and phosphoric acid (H3PO4) solution as
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In this work, LiFePO4/C composite were synthesized via a green route by using Iron (III) oxide (Fe2O3) nanoparticles, Lithium carbonate (Li2CO3), glucose powder and phosphoric acid (H3PO4) solution as raw materials. The reaction principles for the synthesis of LiFePO4/C composite were analyzed, suggesting that almost no wastewater and air polluted gases are discharged into the environment. The morphological, structural and compositional properties of the LiFePO4/C composite were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscopy (TEM), Raman and X-ray photoelectron spectroscopy (XPS) spectra coupled with thermogravimetry/Differential scanning calorimetry (TG/DSC) thermal analysis in detail. Lithium-ion batteries using such LiFePO4/C composite as cathode materials, where the loading level is 2.2 mg/cm2, exhibited excellent electrochemical performances, with a discharge capability of 161 mA h/g at 0.1 C, 119 mA h/g at 10 C and 93 mA h/g at 20 C, and a cycling stability with 98.0% capacity retention at 1 C after 100 cycles and 95.1% at 5 C after 200 cycles. These results provide a valuable approach to reduce the manufacturing costs of LiFePO4/C cathode materials due to the reduced process for the polluted exhaust purification and wastewater treatment. Full article
(This article belongs to the Special Issue Advances in Electrochemical Energy Materials)
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Open AccessReview Recent Hydrophobic Metal-Organic Frameworks and Their Applications
Materials 2018, 11(11), 2250; https://doi.org/10.3390/ma11112250 (registering DOI)
Received: 12 October 2018 / Revised: 2 November 2018 / Accepted: 8 November 2018 / Published: 12 November 2018
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Abstract
The focus of discussion of this review is the application of the most recent synthesized hydrophobic metal-organic frameworks (MOFs). The most promising hydrophobic MOFs are mentioned with their applications and discussed. The various MOFs considered are sub-sectioned into the main application areas, namely
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The focus of discussion of this review is the application of the most recent synthesized hydrophobic metal-organic frameworks (MOFs). The most promising hydrophobic MOFs are mentioned with their applications and discussed. The various MOFs considered are sub-sectioned into the main application areas, namely alcohol adsorption and oil/water-alcohol/water separation, gas separation and storage, and other applications such as self-cleaning and liquid marbles. Again, the methods of synthesis are briefly described, showing how the features of the end product aid in their applications. The efficiency of the MOF materials and synthesis methods are highlighted and briefly discussed. Lastly, the summary and outlook section concludes the write-up giving suggestions that would be useful to present-day researchers. Full article
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Open AccessArticle Poly(Urethane-Acrylate) Aerogels via Radical Polymerization of Dendritic Urethane-Acrylate Monomers
Materials 2018, 11(11), 2249; https://doi.org/10.3390/ma11112249 (registering DOI)
Received: 15 October 2018 / Revised: 28 October 2018 / Accepted: 7 November 2018 / Published: 12 November 2018
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Abstract
The purpose of this work was to investigate the effect of multifunctionality on material properties of synthetic polymer aerogels. For this purpose, we present the synthesis and characterization of monolithic dendritic-type urethane-acrylate monomers based on an aliphatic/flexible (Desmodur N3300), or an aromatic/rigid (Desmodur
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The purpose of this work was to investigate the effect of multifunctionality on material properties of synthetic polymer aerogels. For this purpose, we present the synthesis and characterization of monolithic dendritic-type urethane-acrylate monomers based on an aliphatic/flexible (Desmodur N3300), or an aromatic/rigid (Desmodur RE) triisocyanate core. The terminal acrylate groups (three at the tip of each of the three branches, nine in total) were polymerized with 2,2′-azobis(isobutyronitrile) (AIBN) via free radical chemistry. The resulting wet-gels were dried with supercritical fluid (SCF) CO2. Aerogels were characterized with ATR-FTIR and solid-state 13C NMR. The porous network was probed with N2-sorption and scanning electron microscopy (SEM). The thermal stability of aerogels was studied with thermogravimetric analysis (TGA). Most aerogels were macroporous materials (porosity > 80%), with high thermal stability (up to 300 °C). Aerogels were softer at low monomer concentrations and more rigid at higher concentrations. The material properties were compared with those of analogous aerogels bearing only one acrylate moiety at the tip of each branch and the same cores, and with those of analogous aerogels bearing norbornene instead of acrylate moieties. The nine-terminal acrylate-based monomers of this study caused rapid decrease of the solubility of the growing polymer and made possible aerogels with much smaller particles and much higher surface areas. For the first time, aliphatic/flexible triisocyanate-based materials could be made with similar properties in terms of particle size and surface areas to their aromatic/rigid analogues. Finally, it was found that with monomers with a high number of crosslinkable groups, material properties are determined by multifunctionality and thus aerogels based on 9-acrylate- and 9-norbornene-terminated monomers were similar. Materials with aromatic cores are carbonizable with satisfactory yields (20–30% w/w) to mostly microporous materials (BET surface areas: 640–740 m2 g−1; micropore surface areas: 360–430 m2 g−1). Full article
(This article belongs to the Special Issue Aerogels: Synthesis, Characterization and Application)
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Open AccessArticle Synthesis of Ge1−xSnx Alloy Thin Films by Rapid Thermal Annealing of Sputtered Ge/Sn/Ge Layers on Si Substrates
Materials 2018, 11(11), 2248; https://doi.org/10.3390/ma11112248 (registering DOI)
Received: 25 October 2018 / Revised: 5 November 2018 / Accepted: 7 November 2018 / Published: 12 November 2018
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Abstract
In this work, nanocrystalline Ge1−xSnx alloy formation from a rapid thermal annealed Ge/Sn/Ge multilayer has been presented. The multilayer was magnetron sputtered onto the Silicon substrate. This was followed by annealing the layers by rapid thermal annealing, at temperatures of
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In this work, nanocrystalline Ge1−xSnx alloy formation from a rapid thermal annealed Ge/Sn/Ge multilayer has been presented. The multilayer was magnetron sputtered onto the Silicon substrate. This was followed by annealing the layers by rapid thermal annealing, at temperatures of 300 °C, 350 °C, 400 °C, and 450 °C, for 10 s. Then, the effect of thermal annealing on the morphological, structural, and optical characteristics of the synthesized Ge1−xSnx alloys were investigated. The nanocrystalline Ge1−xSnx formation was revealed by high-resolution X-ray diffraction (HR-XRD) measurements, which showed the orientation of (111). Raman results showed that phonon intensities of the Ge-Ge vibrations were improved with an increase in the annealing temperature. The results evidently showed that raising the annealing temperature led to improvements in the crystalline quality of the layers. It was demonstrated that Ge-Sn solid-phase mixing had occurred at a low temperature of 400 °C, which led to the creation of a Ge1−xSnx alloy. In addition, spectral photo-responsivity of a fabricated Ge1−xSnx metal-semiconductor-metal (MSM) photodetector exhibited its extending wavelength into the near-infrared region (820 nm). Full article
(This article belongs to the Section Thin Films)
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Open AccessArticle Enhanced Ferroelectric and Piezoelectric Properties of (1−x)PMN-xPT Ceramics Based on a Partial Oxalate Process
Materials 2018, 11(11), 2247; https://doi.org/10.3390/ma11112247 (registering DOI)
Received: 12 October 2018 / Revised: 9 November 2018 / Accepted: 10 November 2018 / Published: 12 November 2018
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Abstract
The pyrochlore phase in ferroelectric and piezoelectric materials is the main obstacle device application due to its poor electrical properties. Especially, the pyrochlore phase is frequently observed in the perovskite-based metal-oxide materials including piezoelectric and ferroelectric ceramics, which are based on solid-state reaction
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The pyrochlore phase in ferroelectric and piezoelectric materials is the main obstacle device application due to its poor electrical properties. Especially, the pyrochlore phase is frequently observed in the perovskite-based metal-oxide materials including piezoelectric and ferroelectric ceramics, which are based on solid-state reaction methods for fabrication. To overcome these problems, advanced innovative methods such as partial oxalate process will be investigated. In this method, crystalized magnesium niobite (MN) and lead titanate (PT) powders will be coated with a certain amount of lead oxalate and, then, the calcination process can be carried out to form the PMN-PT without pyrochlore phase. In this study, (1−x)PMN-xPT ceramics near the morphotropic phase boundary (MPB), with compositions of x = 0.25–0.40, have been prepared employing the partial oxalate method at various temperatures. The crystalline, microstructure, and piezoelectric properties of (1−x)PMN-xPT ceramics depending on the sintering temperature were intensively investigated and discussed. By optimizing the sintering temperature and compositions from the PMN-PT ceramics, the maximum value of the piezoelectric charge coefficient (d33) of 665pC/N, planar electromechanical coupling factor (kp) of 77.8%, dielectric constant (εr) of 3230, and remanent polarization (Pr) of 31.67 μC/cm2 were obtained. Full article
(This article belongs to the Special Issue Advanced Functional Nanomaterials and Their Applications)
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Open AccessArticle White-Light Emitting Di-Ureasil Hybrids
Materials 2018, 11(11), 2246; https://doi.org/10.3390/ma11112246 (registering DOI)
Received: 17 October 2018 / Revised: 6 November 2018 / Accepted: 8 November 2018 / Published: 12 November 2018
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Abstract
White-light emitting materials have emerged as important components for solid state lighting devices with high potential for the replacement of conventional light sources. Herein, amine-functionalized organic-inorganic di-ureasil hybrids consisting of a siliceous skeleton and oligopolyether chains codoped with lanthanide-based complexes, with Eu3+
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White-light emitting materials have emerged as important components for solid state lighting devices with high potential for the replacement of conventional light sources. Herein, amine-functionalized organic-inorganic di-ureasil hybrids consisting of a siliceous skeleton and oligopolyether chains codoped with lanthanide-based complexes, with Eu3+ and Tb3+ ions and 4,4′-oxybis(benzoic acid) and 1,10-phenanthroline ligands, and the coumarin 1 dye were synthesized by in situ sol–gel method. The resulting luminescent di-ureasils show red, green, and blue colors originated from the Eu3+, Tb3+, and C1 emissions, respectively. The emission colors can be modulated either by variation of the relative concentration between the emitting centers or by changing the excitation wavelength. White light emission is achieved under UV excitation with absolute quantum yields of 0.148 ± 0.015, 0.167 ± 0.017, and 0.202 ± 0.020 at 350, 332, and 305 nm excitation, respectively. The emission mechanism was investigated by photoluminescence and UV–visible absorption spectroscopy, revealing an efficient energy transfer from the organic ligands to the Ln3+ ions and the organic dye, whereas negligible interaction between the dopants is discerned. The obtained luminescent di-ureasils have potential for optoelectronic applications, such as in white-light emitting diodes. Full article
(This article belongs to the Special Issue From Macromolecules to Materials for Optoelectronic Devices)
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Open AccessArticle Experimental Study of Rubberized Concrete Stress-Strain Behavior for Improving Constitutive Models
Materials 2018, 11(11), 2245; https://doi.org/10.3390/ma11112245 (registering DOI)
Received: 9 October 2018 / Revised: 7 November 2018 / Accepted: 7 November 2018 / Published: 11 November 2018
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Abstract
Inclusion of rubber into concrete changes its behavior and the established shape of its stress-strain curve. Existing constitutive stress-strain models for concrete are not valid in case of rubberized concrete, and currently available modified models require additional validation on a larger database of
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Inclusion of rubber into concrete changes its behavior and the established shape of its stress-strain curve. Existing constitutive stress-strain models for concrete are not valid in case of rubberized concrete, and currently available modified models require additional validation on a larger database of experimental results, with a wider set of influential parameters. By executing uniaxial compressive tests on concrete with rubber substituting 10%, 20%, 30%, and 40% of aggregate, it was possible to study and evaluate the influence of rubber content on its mechanical behavior. The stress-strain curve was investigated in its entirety, including compressive strength, elastic modulus, strains at significant levels of stress, and failure patterns. Experimental results indicated that increase of rubber content linearly decreases compressive strength and elastic modulus, but increases ductility. By comparing experimental stress-strain curves with those plotted using available constitutive stress-strain models it was concluded that they are inadequate for rubberized concrete with high rubber content. Based on determined deviations an improvement of an existing model was proposed, which provides better agreement with experimental curves. Obtained research results enabled important insights into correlations between rubber content and changes of the stress-strain curve required when utilizing nonlinear material properties. Full article
(This article belongs to the Special Issue Mechanical Characterization of Bio-Based Materials and Structures)
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Open AccessArticle Preparation of Renewable Bio-Polyols from Two Species of Colliguaja for Rigid Polyurethane Foams
Materials 2018, 11(11), 2244; https://doi.org/10.3390/ma11112244 (registering DOI)
Received: 27 September 2018 / Revised: 5 November 2018 / Accepted: 8 November 2018 / Published: 11 November 2018
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Abstract
In this study, we investigated the potential of two non-edible oil extracts from seeds of Colliguaja integerrima (CIO) and Colliguaja salicifolia (CSO) to use as a renewable source for polyols and, eventually, polyurethane foams or biodiesel. For this purpose, two novel polyols from
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In this study, we investigated the potential of two non-edible oil extracts from seeds of Colliguaja integerrima (CIO) and Colliguaja salicifolia (CSO) to use as a renewable source for polyols and, eventually, polyurethane foams or biodiesel. For this purpose, two novel polyols from the aforementioned oils were obtained in a one-single step reaction using a mixture of hydrogen peroxide and acetic acid. The polyol derivatives obtained from the two studied oils were characterized by spectral (FTIR, 1H NMR, and 13C NMR), physicochemical (e.g., chromatographic analysis, acid value, oxidizability values, iodine value, peroxide value, saponification number, kinematic viscosity, density, theorical molecular weight, hydroxyl number, and hydroxyl functionality) and thermal (TGA) analyses according to standard methods. Physicochemical results revealed that all parameters, with the exception of the iodine value, were higher for bio-polyols (CSP and CIP) compared to the starting oils. The NMR, TGA, and FTIR analyses demonstrated the formation of polyols. Finally, the OH functionality values for CIP and CSP were 4.50 and 5.00, respectively. This result indicated the possible used of CIP and CSP as a raw material for the preparation of polyurethane rigid foams. Full article
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Open AccessArticle A DIC-Based Study on Fatigue Damage Evolution in Pre-Corroded Aluminum Alloy 2024-T4
Materials 2018, 11(11), 2243; https://doi.org/10.3390/ma11112243 (registering DOI)
Received: 11 October 2018 / Revised: 2 November 2018 / Accepted: 8 November 2018 / Published: 11 November 2018
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Abstract
This paper investigates the fatigue damage and cracking behavior of aluminum alloy 2024-T4 with different levels of prior corrosion. Damage evolution, crack initiation and propagation were experimentally analyzed by digital image correlation, scanning electron microscopy and damage curves. Prior corrosion is shown to
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This paper investigates the fatigue damage and cracking behavior of aluminum alloy 2024-T4 with different levels of prior corrosion. Damage evolution, crack initiation and propagation were experimentally analyzed by digital image correlation, scanning electron microscopy and damage curves. Prior corrosion is shown to cause accelerated damage accumulation, inducing premature fatigue crack initiation, and affecting crack nucleation location, crack orientation and fracture path. For the pre-corrosion condition, although multiple cracks were observed, only one corrosion-initiated primary crack dominates the failure process, in contrast to the plain fatigue cases, where multiple cracks propagated simultaneously leading to final coalescence and fracture. Based on the experimental observations, a mixed-mode fracture model is proposed and shown to successfully predict fatigue crack growth and failure from the single dominant localized corrosion region. Full article
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Open AccessArticle Microstructure and Mechanical Properties of Hot- Rolled and Cold-Rolled Medium-Mn TRIP Steels
Materials 2018, 11(11), 2242; https://doi.org/10.3390/ma11112242 (registering DOI)
Received: 29 September 2018 / Revised: 8 November 2018 / Accepted: 9 November 2018 / Published: 11 November 2018
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Abstract
This study investigated the microstructure and mechanical properties of hot-rolled and cold-rolled medium-Mn transformation-induced plasticity (TRIP) steel. The experimental steel, processed by quenching and tempering (Q & T) heat treatment, exhibited excellent mechanical properties for hot-rolled and Q & T steels (strength of
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This study investigated the microstructure and mechanical properties of hot-rolled and cold-rolled medium-Mn transformation-induced plasticity (TRIP) steel. The experimental steel, processed by quenching and tempering (Q & T) heat treatment, exhibited excellent mechanical properties for hot-rolled and Q & T steels (strength of 1050–1130 MPa and ductility of 16–34%), as well as for cold-rolled and Q & T steels (strength of 878–1373 MPa and ductility of 18–40%). The mechanical properties obtained after isothermal holding at 775 °C for one hour for cold-rolled/Q & T steel were superior to that of hot-rolled/Q & T steel. Excellent mechanical properties were attributed to the large amount of retained austenite, which produced a discontinuous TRIP effect. Additionally, the differences in mechanical properties correlated with the morphology, stability and content of retained austenite. The cold-rolled sample, quenched from 650 °C (CR 650°C) had extensive TRIP effects in the middle and late stages of the deformation, leading to better mechanical properties. The fracture modes of the hot-rolled sample, quenched from 650 °C, and the cold-rolled sample quenched from 650 °C, were ductile fractures, resulting in excellent ductility. Full article
(This article belongs to the Special Issue Deformation, Fatigue and Fracture of Materials)
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Open AccessArticle Anisotropic Pinning-Effect of Inclusions in Mg-Based Low-Carbon Steel
Materials 2018, 11(11), 2241; https://doi.org/10.3390/ma11112241 (registering DOI)
Received: 24 October 2018 / Revised: 8 November 2018 / Accepted: 9 November 2018 / Published: 11 November 2018
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Abstract
In this study, the effect of austenite grain size on acicular ferrite (AF) nucleation in low-carbon steel containing 13 ppm Mg is determined. The average austenite grain size was calculated using OM Leica software. Results show that the predicted and experimental values of
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In this study, the effect of austenite grain size on acicular ferrite (AF) nucleation in low-carbon steel containing 13 ppm Mg is determined. The average austenite grain size was calculated using OM Leica software. Results show that the predicted and experimental values of austenite grain size are extremely close, with a deviation of less than 20 µm. AF formation is difficult to induce by either excessively small and large austenite grain sizes; that is, an optimal austenite grain size is required to promote AF nucleation probability. The austenite grain size of 164 µm revealed the highest capacity to induce AF formation. The effects of the maximum distance of carbon diffusion and austenite grain size on the microstructure of Mg-containing low carbon steel are also discussed. Next, the pinning ability of different inclusion types in low-carbon steel containing 22 Mg is determined. The in situ observation shows that not every inclusion could inhibit austenite grain migration; the inclusion type influences pinning ability. The grain mobility of each inclusion was calculated using in situ micrographs of confocal scanning laser microscopy (CSLM) for micro-analysis. Results show that the austenite grain boundary can strongly be pinned by Mg-based inclusions. MnS inclusions are the least effective in pinning austenite grain boundary migration. Full article
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Open AccessArticle Long-Term Influence of Laser-Processing Parameters on (Super)hydrophobicity Development and Stability of Stainless-Steel Surfaces
Materials 2018, 11(11), 2240; https://doi.org/10.3390/ma11112240 (registering DOI)
Received: 24 October 2018 / Revised: 7 November 2018 / Accepted: 9 November 2018 / Published: 11 November 2018
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Abstract
Controlling the surface wettability represents an important challenge in the field of surface functionalization. Here, the wettability of a stainless-steel surface is modified by 30-ns pulses of a Nd:YAG marking laser (λ = 1064 nm) with peak fluences within the range 3.3–25.1 J
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Controlling the surface wettability represents an important challenge in the field of surface functionalization. Here, the wettability of a stainless-steel surface is modified by 30-ns pulses of a Nd:YAG marking laser (λ = 1064 nm) with peak fluences within the range 3.3–25.1 J cm−2. The short- (40 days), intermediate- (100 days) and long-term (1 year) superhydrophilic-to-(super)hydrophobic transition of the laser-textured surfaces exposed to the atmospheric air is examined by evaluating its wettability in the context of the following parameters: (i) pulse fluence; (ii) scan line separation; (iii) focal position and (iv) wetting period due to contact angle measurements. The results show that using solely a short-term evaluation can lead to wrong conclusions and that the faster development of the hydrophobicity immediately after laser texturing usually leads to lower final contact angle and vice versa, the slower this transition is, the more superhydrophobic the surface is expected to become (possibly even with self-cleaning ability). Depending on laser fluence, the laser-textured surfaces can develop stable or unstable hydrophobicity. Stable hydrophobicity is achieved, if the threshold fluence of 12 J cm−2 is exceeded. We show that by nanosecond-laser texturing a lotus-leaf-like surface with a contact angle above 150° and roll-off angle below 5° can be achieved. Full article
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Open AccessArticle Electrochemical Comparison of SAN/PANI/FLG and ZnO/GO Coated Cast Iron Subject to Corrosive Environments
Materials 2018, 11(11), 2239; https://doi.org/10.3390/ma11112239 (registering DOI)
Received: 24 September 2018 / Revised: 8 November 2018 / Accepted: 9 November 2018 / Published: 11 November 2018
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Abstract
ZnO/GO (Graphene Oxide) and SAN (Styrene Acrylonitrile)/PANI (Polyaniline)/FLG (Few Layers Graphene) nanocomposite coatings were produced by solution casting and sol-gel methods, respectively, to enhance corrosion resistance of ferrous based materials. Corrosive seawater and ‘produced crude oil water’ environments were selected as electrolytes for
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ZnO/GO (Graphene Oxide) and SAN (Styrene Acrylonitrile)/PANI (Polyaniline)/FLG (Few Layers Graphene) nanocomposite coatings were produced by solution casting and sol-gel methods, respectively, to enhance corrosion resistance of ferrous based materials. Corrosive seawater and ‘produced crude oil water’ environments were selected as electrolytes for this study. Impedance and coating capacitance values obtained from Electrochemical Impedance Spectroscopy (EIS) Alternating Current (AC technique) showed enhanced corrosion resistance of nanocomposites coatings in the corrosive environments. Tafel scan Direct Current (DC technique) was used to find the corrosion rate of nanocomposite coating. SAN/PANI/FLG coating reduced the corrosion of bare metal up to 90% in seawater whereas ZnO/GO suppressed the corrosion up to 75% having the impedance value of 100 Ω. In produced water of crude oil, SAN/PANI/FLG reduced the corrosion up to 95% while ZnO/GO suppressed the corrosion up to 10%. Hybrid composites of SAN/PANI/FLG coatings have demonstrated better performances compared to ZnO/GO in the corrosive environments under investigation. This study provides fabrication of state-of-the-art novel anti corrosive nanocomposite coatings for a wide range of industrial applications. Reduced corrosion will result in increased service lifetime, durability and reliability of components and system and will in turn lead to significant cost savings. Full article
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Open AccessArticle Single Chiral Skyrmions in Ultrathin Magnetic Films
Materials 2018, 11(11), 2238; https://doi.org/10.3390/ma11112238 (registering DOI)
Received: 12 October 2018 / Revised: 30 October 2018 / Accepted: 7 November 2018 / Published: 11 November 2018
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Abstract
The stability and sizes of chiral skyrmions in ultrathin magnetic films are calculated accounting for the isotropic exchange, Dzyaloshinskii–Moriya exchange interaction (DMI), and out-of-plane magnetic anisotropy within micromagnetic approach. Bloch skyrmions in ultrathin magnetic films with B20 cubic crystal structure (MnSi, FeGe) and
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The stability and sizes of chiral skyrmions in ultrathin magnetic films are calculated accounting for the isotropic exchange, Dzyaloshinskii–Moriya exchange interaction (DMI), and out-of-plane magnetic anisotropy within micromagnetic approach. Bloch skyrmions in ultrathin magnetic films with B20 cubic crystal structure (MnSi, FeGe) and Neel skyrmions in ultrathin films and multilayers Co/X (X = Ir, Pd, Pt) are considered. The generalized DeBonte ansatz is used to describe the inhomogeneous skyrmion magnetization. The single skyrmion metastability/instability area, skyrmion radius, and skyrmion width are found analytically as a function of DMI strength d . It is shown that the single chiral skyrmions are metastable in infinite magnetic films below a critical value of DMI d c , and do not exist at d > d c . The calculated skyrmion radius increases as d increases and diverges at d d c 0 , whereas the skyrmion width increases monotonically as d increases up to d c without any singularities. The calculated skyrmion width is essentially smaller than the one calculated within the generalized domain wall model. Full article
(This article belongs to the Special Issue New Developments in Ferromagnetic Materials)
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Open AccessLetter Detrimental Effects of Doping Al and Ba on the Thermoelectric Performance of GeTe
Materials 2018, 11(11), 2237; https://doi.org/10.3390/ma11112237 (registering DOI)
Received: 15 October 2018 / Revised: 6 November 2018 / Accepted: 9 November 2018 / Published: 11 November 2018
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Abstract
GeTe-based materials are emerging as viable alternatives to toxic PbTe-based thermoelectric materials. In order to evaluate the suitability of Al as dopant in thermoelectric GeTe, a systematic study of thermoelectric properties of Ge1−xAlxTe (x = 0–0.08) alloys processed
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GeTe-based materials are emerging as viable alternatives to toxic PbTe-based thermoelectric materials. In order to evaluate the suitability of Al as dopant in thermoelectric GeTe, a systematic study of thermoelectric properties of Ge1−xAlxTe (x = 0–0.08) alloys processed by Spark Plasma Sintering are presented here. Being isoelectronic to Ge1−xInxTe and Ge1−xGaxTe, which were reported with improved thermoelectric performances in the past, the Ge1−xAlxTe system is particularly focused (studied both experimentally and theoretically). Our results indicate that doping of Al to GeTe causes multiple effects: (i) increase in p-type charge carrier concentration; (ii) decrease in carrier mobility; (iii) reduction in thermopower and power factor; and (iv) suppression of thermal conductivity only at room temperature and not much significant change at higher temperature. First principles calculations reveal that Al-doping increases the energy separation between the two valence bands (loss of band convergence) in GeTe. These factors contribute for Ge1−xAlxTe to exhibit a reduced thermoelectric figure of merit, unlike its In and Ga congeners. Additionally, divalent Ba-doping [Ge1−xBaxTe (x = 0–0.06)] is also studied. Full article
(This article belongs to the Special Issue Advanced Glasses, Composites and Ceramics for High Growth Industries)
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Open AccessArticle A Facile Way to Prolong Service Life of Double Base Propellant
Materials 2018, 11(11), 2236; https://doi.org/10.3390/ma11112236 (registering DOI)
Received: 16 October 2018 / Revised: 8 November 2018 / Accepted: 9 November 2018 / Published: 10 November 2018
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Abstract
The safe storage time for double base propellant (DBP or DB propellant) with stabilizers could usually be calculated to be greater than 40 years. However, the actual service life is far below that, which is largely caused by the decline of propellant mechanical
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The safe storage time for double base propellant (DBP or DB propellant) with stabilizers could usually be calculated to be greater than 40 years. However, the actual service life is far below that, which is largely caused by the decline of propellant mechanical performance. In this work polytetrafluoroethylene (PTFE) was introduced into the double base propellant formula as an additive. The tensile properties of this propellant before and after artificial aging were determined. The evaporation and diffusion characteristics of nitroglycerin (NG) in propellant were evaluated by thermogravimetry analysis (TGA). The results showed that mechanical properties of propellant were improved due to PTFE, especially for elongation at −40 °C, which was greatly increased by 115%. Moreover, the results of TGA showed that NG migration was reduced due to PTFE, which delayed the decline of propellant mechanical performance during aging. The reduction in elongation at −40 °C caused by aging was decreased by 68.5% for PTFE modified DBP. Enhanced mechanical properties and reduced NG migration could potentially prolong propellant service life. Full article
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Open AccessArticle Local Pressure of Supercritical Adsorbed Hydrogen in Nanopores
Materials 2018, 11(11), 2235; https://doi.org/10.3390/ma11112235 (registering DOI)
Received: 16 October 2018 / Revised: 28 October 2018 / Accepted: 8 November 2018 / Published: 10 November 2018
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Abstract
An overview is given of the development of sorbent materials for hydrogen storage. Understanding the surface properties of the adsorbed film is crucial to optimize hydrogen storage capacities. In this work, the lattice gas model (Ono-Kondo) is used to determine the properties of
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An overview is given of the development of sorbent materials for hydrogen storage. Understanding the surface properties of the adsorbed film is crucial to optimize hydrogen storage capacities. In this work, the lattice gas model (Ono-Kondo) is used to determine the properties of the adsorbed hydrogen film from a single supercritical hydrogen isotherm at 77 K. In addition, this method does not require a conversion between gravimetric excess adsorption and absolute adsorption. The overall average binding energy of hydrogen is 4.4 kJ/mol and the binding energy at low coverage is 9.2 kJ/mol. The hydrogen film density at saturation is 0.10 g/mL corresponding to a local pressure of 1500 bar in the adsorbed phase. Full article
(This article belongs to the Section Energy Materials)
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Open AccessArticle Bioactive Sphene-Based Ceramic Coatings on cpTi Substrates for Dental Implants: An In Vitro Study
Materials 2018, 11(11), 2234; https://doi.org/10.3390/ma11112234 (registering DOI)
Received: 27 September 2018 / Revised: 26 October 2018 / Accepted: 5 November 2018 / Published: 9 November 2018
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Abstract
Titanium implant surface modifications have been widely investigated to favor the process of osseointegration. The present work aimed to evaluate the effect of sphene (CaTiSiO5) biocoating, on titanium substrates, on the in vitro osteogenic differentiation of Human Adipose-Derived Stem Cells (hADSCs).
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Titanium implant surface modifications have been widely investigated to favor the process of osseointegration. The present work aimed to evaluate the effect of sphene (CaTiSiO5) biocoating, on titanium substrates, on the in vitro osteogenic differentiation of Human Adipose-Derived Stem Cells (hADSCs). Sphene bioceramic coatings were prepared using preceramic polymers and nano-sized active fillers and deposited by spray coating. Scanning Electron Microscopy (SEM) analysis, surface roughness measurements and X-ray diffraction analysis were performed. The chemical stability of the coatings in Tris-HCl solution was investigated. In vitro studies were performed by means of proliferation test of hADSCs seeded on coated and uncoated samples after 21 days. Methyl Thiazolyl-Tetrazolium (MTT) test and immunofluorescent staining with phalloidin confirmed the in vitro biocompatibility of both substrates. In vitro osteogenic differentiation of the cells was evaluated using Alizarin Red S staining and quantification assay and real-time PCR (Polymerase Chain Reaction). When hADSCs were cultured in the presence of Osteogenic Differentiation Medium, a significantly higher accumulation of calcium deposits onto the sphene-coated surfaces than on uncoated controls was detected. Osteogenic differentiation on both samples was confirmed by PCR. The proposed coating seems to be promising for dental and orthopedic implants, in terms of composition and deposition technology. Full article
(This article belongs to the Special Issue Ti-Based Biomaterials: Synthesis, Properties and Applications)
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Open AccessArticle Effect of Plasma Treatment and Its Post Process Duration on Shear Bonding Strength and Antibacterial Effect of Dental Zirconia
Materials 2018, 11(11), 2233; https://doi.org/10.3390/ma11112233 (registering DOI)
Received: 16 October 2018 / Revised: 6 November 2018 / Accepted: 7 November 2018 / Published: 9 November 2018
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Abstract
We have investigated the effect of non-thermal atmospheric pressure plasma (NTAPP) treatment and the post process time on the bonding strength and surface sterilization of dental zirconia. Presintered zirconia specimens were manufactured as discs, and then subjected to a 30-min argon treatment (Ar,
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We have investigated the effect of non-thermal atmospheric pressure plasma (NTAPP) treatment and the post process time on the bonding strength and surface sterilization of dental zirconia. Presintered zirconia specimens were manufactured as discs, and then subjected to a 30-min argon treatment (Ar, 99.999%; 10 L/min) using an NTAPP device. Five post-treatment durations were evaluated: control (no treatment), P0 (immediate), P1 (24 h), P2 (48 h), and P3 (72 h). The surface characteristics, shear bonding strength (SBS) with two resin cements, and Streptococcus mutans biofilm formation of these plasma-treated dental zirconia were tested. Plasma did not change the roughness, and caused surface element changes and surface energy increase. Due to this increase in surface energy, SBS increased significantly (p < 0.05) within 48 h when RelyXTM U200 was used. However, the increase of surface oxygen significantly decreased (p < 0.05) the SBS of Panavia F 2.0 when using plasma immediately (P0). S. mutans adhesion decreased significantly (p < 0.05) for the P0, P1, and P2 groups compared to the control. The P0 group exhibited lower biofilm thickness than the other experimental groups due to the increased hydrophilicity (p < 0.05). Our study suggests that there is a suitable time window for the post NTAPP treatment regarding bonding strength and antimicrobial growth persist. Full article
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Open AccessArticle Dual-Emission Fluorescent Microspheres for the Detection of Biothiols and Hg2+
Materials 2018, 11(11), 2232; https://doi.org/10.3390/ma11112232 (registering DOI)
Received: 25 September 2018 / Revised: 7 November 2018 / Accepted: 7 November 2018 / Published: 9 November 2018
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Abstract
Dual-emission nanosensor for Hg2+ detection was prepared by coupling CA-AEAPMS on the surface of RBS-doped modified silica microspheres. The CA-AEAPMS was synthesized by using N-(β-aminoethyl)-γ-aminopropyl methyldimethoxysilane (AEAPMS) and citric acid as the main raw material. The obtained nanosensor showed characteristic fluorescence
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Dual-emission nanosensor for Hg2+ detection was prepared by coupling CA-AEAPMS on the surface of RBS-doped modified silica microspheres. The CA-AEAPMS was synthesized by using N-(β-aminoethyl)-γ-aminopropyl methyldimethoxysilane (AEAPMS) and citric acid as the main raw material. The obtained nanosensor showed characteristic fluorescence emissions of Rhodamine B (red) and CA-AEAPMS (blue) under a single excitation wavelength (360 nm). Upon binding to Hg2+, only the fluorescence of CA-AEAPMS was quenched, resulting in the ratiometric fluorescence response of the dual-emission silica microspheres. This ratiometric nanosensor exhibited good selectivity to Hg2+ over other metal ions, because of the amide groups on the surface of CA-AEAPMS serving as the Hg2+ recognition sites. The ratio of F450/F580 linearly decreased with the increasing of Hg2+ concentration in the range of 0 to 3 × 10−6 M, and a detection limit was as low as 97 nM was achieved. Then, the addition of three thiol-containing amino acids (Cys, Hcy, GSH) to the quenched fluorescence solution with Hg2+ can restore the fluorescence, and the detection limits of the three biothiols (Cys, Hcy, GSH) are 0.133 μM, 0.086 μM, and 0.123 μM, respectively. Full article
(This article belongs to the Special Issue Selected Papers from IEEE ICKII 2018)
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Open AccessArticle Spray Deposition of Ag Nanowire–Graphene Oxide Hybrid Electrodes for Flexible Polymer–Dispersed Liquid Crystal Displays
Materials 2018, 11(11), 2231; https://doi.org/10.3390/ma11112231 (registering DOI)
Received: 18 October 2018 / Revised: 6 November 2018 / Accepted: 6 November 2018 / Published: 9 November 2018
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Abstract
We investigated the effect of different spray-coating parameters on the electro-optical properties of Ag nanowires (NWs). Highly transparent and conductive Ag NW–graphene oxide (GO) hybrid electrodes were fabricated by using the spray-coating technique. The Ag NW percolation network was modified with GO and
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We investigated the effect of different spray-coating parameters on the electro-optical properties of Ag nanowires (NWs). Highly transparent and conductive Ag NW–graphene oxide (GO) hybrid electrodes were fabricated by using the spray-coating technique. The Ag NW percolation network was modified with GO and this led to a reduced sheet resistance of the Ag NW–GO electrode as the result of a decrease in the inter-nanowire contact resistance. Although electrical conductivity and optical transmittance of the Ag NW electrodes have a trade-off relationship, Ag NW–GO hybrid electrodes exhibited significantly improved sheet resistance and slightly decreased transmittance compared to Ag NW electrodes. Ag NW–GO hybrid electrodes were integrated into smart windows based on polymer-dispersed liquid crystals (PDLCs) for the first time. Experimental results showed that the electro-optical properties of the PDLCs based on Ag NW–GO electrodes were superior when compared to those of PDLCs based on only Ag NW electrodes. This study revealed that the hybrid Ag NW–GO electrode is a promising material for manufacturing the large-area flexible indium tin oxide (ITO)-free PDLCs. Full article
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Open AccessArticle Preparation and Thermal Performance Enhancement of Low Temperature Eutectic Composite Phase Change Materials Based on Na2SO4·10H2O
Materials 2018, 11(11), 2230; https://doi.org/10.3390/ma11112230 (registering DOI)
Received: 18 October 2018 / Revised: 6 November 2018 / Accepted: 6 November 2018 / Published: 9 November 2018
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Abstract
In this paper, a series of Na2SO4·10H2O–KCl eutectic mixtures were prepared by adding different mass fractions of KCl (1 wt.%, 3 wt.%, 5 wt.%, or 7 wt.%) to Na2SO4·10H2O. Polyacrylamide (PAM)
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In this paper, a series of Na2SO4·10H2O–KCl eutectic mixtures were prepared by adding different mass fractions of KCl (1 wt.%, 3 wt.%, 5 wt.%, or 7 wt.%) to Na2SO4·10H2O. Polyacrylamide (PAM) was proposed as the thickener, sodium tetraborate decahydrate (STD) was proposed as the nucleating agent, and expanded graphite (EG) was proposed as the high thermal conductivity medium for Na2SO4·10H2O–5 wt.% KCl eutectics. The results showed that in Na2SO4·10H2O–5 wt.% KCl eutectics with 5 wt.% PAM and 5 wt.% STD, almost no phase separation occurred, and the degree of supercooling was reduced to 0.4 °C. The thermal performance of Na2SO4·10H2O–5 wt.% KCl composite phase change materials (CPCMs) with varying contents of EG was explored. The results showed that EG could improve the thermal conductivity effectively and that the mass fraction of EG should be no more than 3%, otherwise the crystallization value and supercooling would deteriorate. The thermal reliability of the Na2SO4·10H2O–5 wt.% KCl eutectic CPCMs containing 5 wt.% PAM, 5 wt.% STD, and 3 wt.% EG was investigated, mainly through the ambient temperature, thermal cycling test, and TGA analysis. The results demonstrated that these CPCMs showed perfect thermal reliability. Full article
(This article belongs to the Section Energy Materials)
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Open AccessArticle Imaging the Polymorphic Transformation in a Single Cu6Sn5 Grain in a Solder Joint
Materials 2018, 11(11), 2229; https://doi.org/10.3390/ma11112229 (registering DOI)
Received: 16 October 2018 / Revised: 2 November 2018 / Accepted: 7 November 2018 / Published: 9 November 2018
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Abstract
In-situ observations of the polymorphic transformation in a single targeted Cu6Sn5 grain constrained between Sn-0.7 wt % Cu solder and Cu-Cu3Sn phases and the associated structural evolution during a solid-state thermal cycle were achieved via a high-voltage transmission
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In-situ observations of the polymorphic transformation in a single targeted Cu6Sn5 grain constrained between Sn-0.7 wt % Cu solder and Cu-Cu3Sn phases and the associated structural evolution during a solid-state thermal cycle were achieved via a high-voltage transmission electron microscope (HV-TEM) technique. Here, we show that the monoclinic η′-Cu6Sn5 superlattice reflections appear in the hexagonal η-Cu6Sn5 diffraction pattern upon cooling to isothermal 140 °C from 210 °C. The in-situ real space imaging shows that the η′-Cu6Sn5 contrast pattern is initiated at the grain boundary. This method demonstrates a new approach for further understanding the polymorphic transformation behavior on a real solder joint. Full article
(This article belongs to the Special Issue Material Interconnections and Microstructure Control-Related)
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Open AccessArticle Preparation and Characterization of Phenolic Foam Modified with Bio-Oil
Materials 2018, 11(11), 2228; https://doi.org/10.3390/ma11112228
Received: 13 October 2018 / Revised: 6 November 2018 / Accepted: 6 November 2018 / Published: 9 November 2018
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Abstract
Bio-oil was added as a substitute for phenol for the preparation of a foaming phenolic resin (PR), which aimed to reduce the brittleness and pulverization of phenolic foam (PF). The components of bio-oil, the chemical structure of bio-oil phenolic resin (BPR), and the
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Bio-oil was added as a substitute for phenol for the preparation of a foaming phenolic resin (PR), which aimed to reduce the brittleness and pulverization of phenolic foam (PF). The components of bio-oil, the chemical structure of bio-oil phenolic resin (BPR), and the mechanical performances, and the morphological and thermal properties of bio-oil phenolic foam (BPF) were investigated. The bio-oil contained a number of phenols and abundant substances with long-chain alkanes. The peaks of OH groups, CH2 groups, C=O groups, and aromatic skeletal vibration on the Fourier transform infrared (FT-IR) spectrum became wider and sharper after adding bio-oil. These suggested that the bio-oil could partially replace phenol to prepare resin and had great potential for toughening resin. When the substitute rate of bio-oil to phenol (B/P substitute rate) was between 10% and 20%, the cell sizes of BPFs were smaller and more uniform than those of PF. The compressive strength and flexural strength of BPFs with a 10–20% B/P substitute rate increased by 10.5–47.4% and 25.0–50.5% respectively, and their pulverization ratios decreased by 14.5–38.6% in comparison to PF. All BPFs maintained good flame-retardant properties, thermal stability, and thermal isolation, although the limited oxygen index (LOI) and residual masses by thermogravimetric (TG) analysis of BPFs were lower and the thermal conducticity was slightly greater than those of PF. This indicated that the bio-oil could be used as a renewable toughening agent for PF. Full article
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Open AccessArticle Effect of the Preparation Method (Sol-Gel or Hydrothermal) and Conditions on the TiO2 Properties and Activity for Propene Oxidation
Materials 2018, 11(11), 2227; https://doi.org/10.3390/ma11112227
Received: 19 October 2018 / Revised: 5 November 2018 / Accepted: 6 November 2018 / Published: 9 November 2018
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Abstract
Since the two most commonly used methods for TiO2 preparation are sol-gel (SG) and hydrothermal (HT) synthesis, this study attempts to compare both methods in order to determine which one is the most suitable to prepare photocatalysts for propene oxidation. In addition,
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Since the two most commonly used methods for TiO2 preparation are sol-gel (SG) and hydrothermal (HT) synthesis, this study attempts to compare both methods in order to determine which one is the most suitable to prepare photocatalysts for propene oxidation. In addition, this work studies how the concentration of the HCl used for hydrolysis of the TiO2 precursor affects the properties of the obtained materials. Also, the effect of avoiding the post-synthesis heat-treatment in a selection of samples is investigated. The photocatalysts are characterized by XRD, N2 adsorption-desorption isotherms and UV-vis spectroscopy, and the study tries to correlate the properties with the photocatalytic performance of the prepared TiO2 samples in propene oxidation. TiO2 materials with high crystallinity, between 67% and 81%, and surface area (up to 134 m2/g) have been obtained both by SG and HT methods. In general, the surface area and pore volume of the TiO2-HT samples are larger than those of TiO2-SG ones. The TiO2-HT catalysts are, in general, more active than TiO2-SG materials or P25 in the photo-oxidation of propene. The effect of HCl presence during the TiO2 synthesis and of the post synthesis heat treatment are much more marked in the case of the SG materials. Full article
(This article belongs to the Special Issue Photocatalytic Materials for Energy and Environmental Applications)
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Open AccessArticle Interfacial Microstructure and Properties of Si3N4 Ceramics/Cu/304 Stainless Steel Brazed by Ti40Zr25B0.2Cu Amorphous Solder
Materials 2018, 11(11), 2226; https://doi.org/10.3390/ma11112226
Received: 18 October 2018 / Revised: 2 November 2018 / Accepted: 6 November 2018 / Published: 9 November 2018
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Abstract
Si3N4 ceramics and 304 stainless steel were brazed by Ti40Zr25B0.2Cu amorphous solder, and the interfacial microstructure of brazed joint Si3N4 ceramics/Ti40Zr25B0.2Cu/Cu/Ti40Zr25B0.2Cu/304 stainless steel was analyzed. The mechanical properties of the brazed joint were overtly affected by the
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Si3N4 ceramics and 304 stainless steel were brazed by Ti40Zr25B0.2Cu amorphous solder, and the interfacial microstructure of brazed joint Si3N4 ceramics/Ti40Zr25B0.2Cu/Cu/Ti40Zr25B0.2Cu/304 stainless steel was analyzed. The mechanical properties of the brazed joint were overtly affected by the brazing temperature and Cu foil thickness. The results revealed that the interface structure of the brazed joint might be 304 stainless steel/FeTi/Cu-Zr+Cu-Ti+Fe-Ti/Cu(s,s)/Cu-Zr+Cu-Ti+Fe-Ti/Ti-Si+Zr-Si/TiN/Si3N4 ceramics. The four-point bending strength of the brazed joint decreased sharply as the brazing temperature increased and reached a maximum of 76 MPa at 1223 K. Furthermore, as the Cu foil thickness was increased from 500 μm to 1000 μm, the joint strength rose to 90 MPa at 1223 K. Full article
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