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Materials, Volume 11, Issue 6 (June 2018)

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Cover Story (view full-size image) Intermetallic type I clathrates are considered to be potential thermoelectric (TE) materials due to [...] Read more.
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Open AccessArticle Microscopic View of Defect Evolution in Thermal Treated AlGaInAs Quantum Well Revealed by Spatially Resolved Cathodoluminescence
Materials 2018, 11(6), 1049; https://doi.org/10.3390/ma11061049
Received: 12 May 2018 / Revised: 5 June 2018 / Accepted: 16 June 2018 / Published: 20 June 2018
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Abstract
An aluminum gallium indium arsenic (AlGaInAs) material system is indispensable as the active layer of diode lasers emitting at 1310 or 1550 nm, which are used in optical fiber communications. However, the course of the high-temperature instability of a quantum well structure, which
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An aluminum gallium indium arsenic (AlGaInAs) material system is indispensable as the active layer of diode lasers emitting at 1310 or 1550 nm, which are used in optical fiber communications. However, the course of the high-temperature instability of a quantum well structure, which is closely related to the diffusion of indium atoms, is still not clear due to the system’s complexity. The diffusion process of indium atoms was simulated by thermal treatment, and the changes in the optical and structural properties of an AlGaInAs quantum well are investigated in this paper. Compressive strained Al0.07Ga0.22In0.71As quantum wells were treated at 170 °C with different heat durations. A significant decrement of photoluminescence decay time was observed on the quantum well of a sample that was annealed after 4 h. The microscopic cathodoluminescent (CL) spectra of these quantum wells were measured by scanning electron microscope-cathodoluminescence (SEM-CL). The thermal treatment effect on quantum wells was characterized via CL emission peak wavelength and energy density distribution, which were obtained by spatially resolved cathodoluminescence. The defect area was clearly observed in the Al0.07Ga0.22In0.71As quantum wells layer after thermal treatment. CL emissions from the defect core have higher emission energy than those from the defect-free regions. The defect core distribution, which was associated with indium segregation gradient distribution, showed asymmetric character. Full article
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Open AccessArticle Percent Reduction in Transverse Rupture Strength of Metal Matrix Diamond Segments Analysed via Discrete-Element Simulations
Materials 2018, 11(6), 1048; https://doi.org/10.3390/ma11061048
Received: 25 April 2018 / Revised: 5 June 2018 / Accepted: 13 June 2018 / Published: 20 June 2018
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Abstract
The percent TRS reduction, DTRS, which is the percent reduction of the transverse rupture strength of metal matrix diamond segments with or without diamonds, is a key metric for evaluating the bonding condition of diamonds in a matrix. In this work,
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The percent TRS reduction, DTRS, which is the percent reduction of the transverse rupture strength of metal matrix diamond segments with or without diamonds, is a key metric for evaluating the bonding condition of diamonds in a matrix. In this work, we build, calibrate, and verify a discrete-element simulation of a metal matrix diamond segment to obtain DTRS for diamond segments with various diamond-grain sizes, concentrations, and distributions. The results indicate that DTRS increases with increasing diamond-grain concentration and decreases with increasing diamond-grain size. Both factors can be explained by the total diamond contact length, the increase of which causes the increase in DTRS. The distribution of diamond grains in segments also strongly influences the increase of DTRS. The use of DTRS as a metric to assess the bonding condition of diamonds in matrixes is not valid unless the diamond-grain size, concentration, and distribution and total diamond contact length are the same for all diamond segments under consideration. Full article
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Open AccessArticle Study on the Preparation of Plasma-Modified Fly Ash Catalyst and Its De–NOX Mechanism
Materials 2018, 11(6), 1047; https://doi.org/10.3390/ma11061047
Received: 3 May 2018 / Revised: 13 June 2018 / Accepted: 15 June 2018 / Published: 20 June 2018
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Abstract
Fly ash and bentonite were mixed in a certain proportion as raw materials to prepare a denitration catalyst. In previous studies, it has been concluded that fly ash-type catalysts can provide significant catalytic activity for denitrification after being modified with oxygen. In this
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Fly ash and bentonite were mixed in a certain proportion as raw materials to prepare a denitration catalyst. In previous studies, it has been concluded that fly ash-type catalysts can provide significant catalytic activity for denitrification after being modified with oxygen. In this study, the effect of plasma conditions on the denitration performance of the catalyst was investigated from the aspects of plasma modification power, modification time, and the flow rate of the gas. Boehm titration and infrared analysis systems were used to characterize the performance of the catalyst. The experimental results show that the optimal modification power is 60 W, the optimal modification time is 20 min, and the optimal gas flow rate is 40 mL/min. Full article
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Open AccessArticle Quadratic Solid–Shell Finite Elements for Geometrically Nonlinear Analysis of Functionally Graded Material Plates
Materials 2018, 11(6), 1046; https://doi.org/10.3390/ma11061046
Received: 30 May 2018 / Revised: 16 June 2018 / Accepted: 17 June 2018 / Published: 20 June 2018
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Abstract
In the current contribution, prismatic and hexahedral quadratic solid–shell (SHB) finite elements are proposed for the geometrically nonlinear analysis of thin structures made of functionally graded material (FGM). The proposed SHB finite elements are developed within a purely 3D framework, with displacements as
[...] Read more.
In the current contribution, prismatic and hexahedral quadratic solid–shell (SHB) finite elements are proposed for the geometrically nonlinear analysis of thin structures made of functionally graded material (FGM). The proposed SHB finite elements are developed within a purely 3D framework, with displacements as the only degrees of freedom. Also, the in-plane reduced-integration technique is combined with the assumed-strain method to alleviate various locking phenomena. Furthermore, an arbitrary number of integration points are placed along a special direction, which represents the thickness. The developed elements are coupled with functionally graded behavior for the modeling of thin FGM plates. To this end, the Young modulus of the FGM plate is assumed to vary gradually in the thickness direction, according to a volume fraction distribution. The resulting formulations are implemented into the quasi-static ABAQUS/Standard finite element software in the framework of large displacements and rotations. Popular nonlinear benchmark problems are considered to assess the performance and accuracy of the proposed SHB elements. Comparisons with reference solutions from the literature demonstrate the good capabilities of the developed SHB elements for the 3D simulation of thin FGM plates. Full article
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Open AccessArticle A Novel Multiscale Mathematical Model for Building Bone Substitute Materials for Children
Materials 2018, 11(6), 1045; https://doi.org/10.3390/ma11061045
Received: 30 April 2018 / Revised: 10 May 2018 / Accepted: 12 May 2018 / Published: 20 June 2018
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Abstract
Bone is an engineering marvel that achieves a unique combination of stiffness and toughness exceeding that of synthesized materials. In orthopedics, we are currently challenged for the child population that needs a less stiff but a tougher bone substitute than adults. Recent evidence
[...] Read more.
Bone is an engineering marvel that achieves a unique combination of stiffness and toughness exceeding that of synthesized materials. In orthopedics, we are currently challenged for the child population that needs a less stiff but a tougher bone substitute than adults. Recent evidence suggests that the relationship between inter-molecular connections that involve the two main bone building blocks, TropoCollagen molecules (TC) and carbonated Hydroxyapatite (cAp), and bone macroscopic mechanical properties, stiffness and toughness, are key to building bone substitute materials for children. The goal of our study is to establish how inter-molecular connections that occur during bone mineralization are related to macroscopic mechanical properties in child bones. Our aim is to link the biological alterations of the TC-cAp self assembly process happening during bone mineralization to the bone macroscopic mechanical properties’ alterations during aging. To do so, we have developed a multiscale mathematical model that includes collagen cross links (TC–TC interface) from experimental studies of bone samples to forecast bone macroscopic mechanical properties. Our results support that the Young’s modulus cannot be a linear parameter if we want to solve our system. In relation to bone substitute material with innovative properties for children, our results propose values of several biological parameters, such as the number of crystals and their size, and collagen crosslink maturity for the desired bone mechanical competence. Our novel mathematical model combines mineralization and macroscopic mechanical behavior of bone and is a step forward in building mechanically customized biomimetic bone grafts that would fit children’s orthopedic needs. Full article
(This article belongs to the Special Issue Bone Substitute Materials)
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Open AccessArticle Hot Deformation Behavior and Microstructure Evolution of 14Cr ODS Steel
Materials 2018, 11(6), 1044; https://doi.org/10.3390/ma11061044
Received: 21 May 2018 / Revised: 9 June 2018 / Accepted: 11 June 2018 / Published: 20 June 2018
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Abstract
Hot deformation tests of 14Cr oxide dispersion strengthened (ODS) steel fabricated by mechanical alloying and hot isostatic pressing (HIP) were performed on a Gleeble-1500D simulator at temperatures ranging from 1050 to 1200 °C with the strain rate range of 0.001−1 s−1
[...] Read more.
Hot deformation tests of 14Cr oxide dispersion strengthened (ODS) steel fabricated by mechanical alloying and hot isostatic pressing (HIP) were performed on a Gleeble-1500D simulator at temperatures ranging from 1050 to 1200 °C with the strain rate range of 0.001−1 s−1. The relationship between the rheological stress and the deformation condition was studied, and a processing map at the true strain of 0.5 was proposed. Microstructure evolution during the deformation process and the effects of deformation conditions on microstructures were also investigated, as well as the stability of nanoparticles. Results show that the 14Cr ODS steel possesses positive strain rate sensitivity. The flow stress increases with the decrease of deformation temperature and the increase of strain rate. The recrystallization process is promoted by the increase of deformation temperature and the reduction of strain rate. Nanoparticles possess excellent stability during the deformation process and are coherent with the matrix. Full article
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Open AccessArticle Wear Resistance of 3D Printing Resin Material Opposing Zirconia and Metal Antagonists
Materials 2018, 11(6), 1043; https://doi.org/10.3390/ma11061043
Received: 9 May 2018 / Revised: 11 June 2018 / Accepted: 15 June 2018 / Published: 20 June 2018
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Abstract
3D printing offers many advantages in dental prosthesis manufacturing. This study evaluated the wear resistance of 3D printing resin material compared with milling and conventional resin materials. Sixty substrate specimens were prepared with three types of resin materials: 3D printed resin, milled resin,
[...] Read more.
3D printing offers many advantages in dental prosthesis manufacturing. This study evaluated the wear resistance of 3D printing resin material compared with milling and conventional resin materials. Sixty substrate specimens were prepared with three types of resin materials: 3D printed resin, milled resin, and self-cured resin. The 3D printed specimens were printed at a build angle of 0° and 100 μm layer thickness by digital light processing 3D printing. Two kinds of abraders were made of zirconia and CoCr alloy. The specimens were loaded at 5 kg for 30,000 chewing cycles with vertical and horizontal movements under thermocycling condition. The 3D printed resin did not show significant difference in the maximal depth loss or the volume loss of wear compared to the milled and the self-cured resins. No significant difference was revealed depending on the abraders in the maximal depth loss or the volume loss of wear. In SEM views, the 3D printed resin showed cracks and separation of inter-layer bonds when opposing the metal abrader. The results suggest that the 3D printing using resin materials provides adequate wear resistance for dental use. Full article
(This article belongs to the Section Manufacturing Processes and Systems)
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Open AccessArticle Experimental and Theoretical Investigation of Thiazolyl Blue as a Corrosion Inhibitor for Copper in Neutral Sodium Chloride Solution
Materials 2018, 11(6), 1042; https://doi.org/10.3390/ma11061042
Received: 24 May 2018 / Revised: 9 June 2018 / Accepted: 13 June 2018 / Published: 19 June 2018
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Abstract
The anticorrosion effect of thiazolyl blue (MTT) for copper in 3% NaCl at 298 K was researched by electrochemical methods, scanning electron-microscopy (SEM), and atomic force microscopy (AFM). The results reveal that MTT can protect copper efficiently, with a maximum efficiency of 95.7%.
[...] Read more.
The anticorrosion effect of thiazolyl blue (MTT) for copper in 3% NaCl at 298 K was researched by electrochemical methods, scanning electron-microscopy (SEM), and atomic force microscopy (AFM). The results reveal that MTT can protect copper efficiently, with a maximum efficiency of 95.7%. The corrosion inhibition mechanism was investigated by X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectral (FT-IR), and theoretical calculation. The results suggest that the MTT molecules are adsorbed on metal surface forming a hydrophobic protective film to prevent copper corrosion. It also indicates that the MTT and copper form covalent bonds. The molecular dynamic simulation further gives the evidence for adsorption. The adsorption isotherm studies demonstrate that a spontaneous, mixed physical and chemical adsorption occurs, which obeys Langmuir adsorption isotherm. The present research can help us better understand the corrosion inhibition process and improve it. Full article
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Open AccessArticle Elucidating the Photocatalytic Behavior of TiO2-SnS2 Composites Based on Their Energy Band Structure
Materials 2018, 11(6), 1041; https://doi.org/10.3390/ma11061041
Received: 29 May 2018 / Revised: 12 June 2018 / Accepted: 14 June 2018 / Published: 19 June 2018
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Abstract
TiO2-SnS2 composite semiconducting photocatalysts with different building component ratios were prepared by hydrothermal synthesis (TiO2-SnS2-HT) and by immobilization of commercial TiO2 and SnS2 particles (TiO2-SnS2-COMM). The band gap values, which
[...] Read more.
TiO2-SnS2 composite semiconducting photocatalysts with different building component ratios were prepared by hydrothermal synthesis (TiO2-SnS2-HT) and by immobilization of commercial TiO2 and SnS2 particles (TiO2-SnS2-COMM). The band gap values, which determine the catalysts’ photoactivity, were examined by diffuse reflectance spectroscopy and Kubelka–Munk transformations. The catalysts’ surface properties: specific surface area, charge and adsorption capacitance at the solid–solution interface were characterized using BET analysis, potentiometric titration and electrochemical impedance spectroscopy, respectively. The electronic band structure of TiO2-SnS2 photocatalyst, as the key property for the solar-driven photocatalysis, was deduced from the thermodynamic data and the semiconducting parameters (type of semiconductivity, concentration of the charge carriers, flat band potential) obtained by Mott–Schottky analysis. The photoactivity of both composites was studied in photocatalytic treatment of diclofenac (DCF) under simulated solar irradiation and was compared to the benchmark photocatalyst (TiO2 P25) activity. The influence of process parameters, such as pH, H2O2, and composite formulation on the effectiveness of DCF removal and conversion was investigated and discussed by employing response surface modeling (RSM) approach. The photocatalytic efficiency of both composite materials was discussed on the basis of the hetereojunction formation that facilitated the photoelectron transfer, promoting more efficient photocatalytic degradation of DCF. Full article
(This article belongs to the Special Issue Photocatalysis for Wastewater Treatment)
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Open AccessReview Magnetic Particle Filled Elastomeric Hybrid Composites and Their Magnetorheological Response
Materials 2018, 11(6), 1040; https://doi.org/10.3390/ma11061040
Received: 14 April 2018 / Revised: 2 June 2018 / Accepted: 13 June 2018 / Published: 19 June 2018
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Abstract
The magnetorheological (MR) elastomer as a hard and soft hybrid functional material, a composite material consisting of magnetic hard particles embedded in elastomeric soft matrix, is a branch of MR materials that are functional smart materials rapidly responding to external magnetic fields. These
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The magnetorheological (MR) elastomer as a hard and soft hybrid functional material, a composite material consisting of magnetic hard particles embedded in elastomeric soft matrix, is a branch of MR materials that are functional smart materials rapidly responding to external magnetic fields. These tunable properties of MR elastomers facilitate a variety of applications. In this brief review paper, in addition to general information on the MR elastomers, recent research not only on a wide variety of MR elastomeric systems focusing on various magnetic particles, elastomeric matrices, additives and particle modification methods, but also on their characteristics including MR properties from dynamic oscillation tests is covered along with their mechanical properties such as the Payne effect, tensile strength and engineering applications. Full article
(This article belongs to the Special Issue Hard and Soft Hybrid Functional Materials)
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Open AccessArticle Giant Enhancement of Magnetostrictive Response in Directionally-Solidified Fe83Ga17Erx Compounds
Materials 2018, 11(6), 1039; https://doi.org/10.3390/ma11061039
Received: 19 May 2018 / Revised: 7 June 2018 / Accepted: 8 June 2018 / Published: 19 June 2018
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Abstract
We report, for the first time, correlations between crystal structure, microstructure and magnetofunctional response in directionally solidified [110]-textured Fe83Ga17Erx (0 < x < 1.2) alloys. The morphology of the doped samples consists of columnar grains, mainly composed of
[...] Read more.
We report, for the first time, correlations between crystal structure, microstructure and magnetofunctional response in directionally solidified [110]-textured Fe83Ga17Erx (0 < x < 1.2) alloys. The morphology of the doped samples consists of columnar grains, mainly composed of a matrix phase and precipitates of a secondary phase deposited along the grain boundary region. An enhancement of more than ~275% from ~45 to 170 ppm is observed in the saturation magnetostriction value (λs) of Fe83Ga17Erx alloys with the introduction of small amounts of Er. Moreover, it was noted that the low field derivative of magnetostriction with respect to an applied magnetic field (i.e., dλs/dHapp for Happ up to 1000 Oe) increases by ~230% with Er doping (dλs/dHapp,FeGa= 0.045 ppm/Oe; dλs/dHapp,FeGaEr= 0.15 ppm/Oe). The enhanced magnetostrictive response of the Fe83Ga17Erx alloys is ascribed to an amalgamation of microstructural and electronic factors, namely: (i) improved grain orientation and local strain effects due to deposition of Er in the intergranular region; and (ii) strong local magnetocrystalline anisotropy, due to the highly anisotropic localized nature of the 4f electronic charge distribution of the Er atom. Overall, this work provides guidelines for further improving galfenol-based materials systems for diverse applications in the power and energy sector. Full article
(This article belongs to the Special Issue Magnetostrictive Composite Materials)
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Open AccessArticle Influence of Microstructure and Shot Peening Treatment on Corrosion Resistance of AISI F55-UNS S32760 Super Duplex Stainless Steel
Materials 2018, 11(6), 1038; https://doi.org/10.3390/ma11061038
Received: 5 May 2018 / Revised: 11 June 2018 / Accepted: 15 June 2018 / Published: 19 June 2018
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Abstract
Shot peening is a surface process commonly used in the aeronautic and automotive industries to improve fatigue resistance. Shot peening is proven to be beneficial in the fatigue behavior of components, but rarely has its influence on wear and pitting corrosion resistance been
[...] Read more.
Shot peening is a surface process commonly used in the aeronautic and automotive industries to improve fatigue resistance. Shot peening is proven to be beneficial in the fatigue behavior of components, but rarely has its influence on wear and pitting corrosion resistance been evaluated. In this work, shot peening was performed on AISI F55-UNS S32760 super-duplex stainless steel samples previously submitted to various thermal treatments, to obtain different initial microstructures and properties. Samples have been characterized in terms of microstructure morphology, local chemical composition, microhardness of each constituent phase, and energy dissipation modes. The enhanced properties provided by shot peening has been evaluated through residual stress depth profiles and Full Width at Half Maximum (FWHM) using X-ray diffraction (XRD), surface hardness, surface roughness, and corrosion resistance through salt spray fog tests. The 1400 °C solution thermal treatment was identified as the optimum initial condition, which maximizes the advantages of the shot peening treatment, even pitting corrosion resistance. These results are related to the uniformity of austenite and ferrite in terms of microstructure morphology, micromechanical properties, and alloying elements distribution. Full article
(This article belongs to the Section Manufacturing Processes and Systems)
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Open AccessArticle High-Temperature Tolerance in Multi-Scale Cermet Solar-Selective Absorbing Coatings Prepared by Laser Cladding
Materials 2018, 11(6), 1037; https://doi.org/10.3390/ma11061037
Received: 6 June 2018 / Accepted: 16 June 2018 / Published: 19 June 2018
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Abstract
In order to achieve cermet-based solar absorber coatings with long-term thermal stability at high temperatures, a novel single-layer, multi-scale TiC-Ni/Mo cermet coating was first prepared using laser cladding technology in atmosphere. The results show that the optical properties of the cermet coatings using
[...] Read more.
In order to achieve cermet-based solar absorber coatings with long-term thermal stability at high temperatures, a novel single-layer, multi-scale TiC-Ni/Mo cermet coating was first prepared using laser cladding technology in atmosphere. The results show that the optical properties of the cermet coatings using laser cladding were much better than the preplaced coating. In addition, the thermal stability of the optical properties for the laser cladding coating were excellent after annealing at 650 °C for 200 h. The solar absorptance and thermal emittance of multi-scale cermet coating were 85% and 4.7% at 650 °C. The results show that multi-scale cermet materials are more suitable for solar-selective absorbing coating. In addition, laser cladding is a new technology that can be used for the preparation of spectrally-selective coatings. Full article
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Open AccessFeature PaperArticle Single Step Laser Transfer and Laser Curing of Ag NanoWires: A Digital Process for the Fabrication of Flexible and Transparent Microelectrodes
Materials 2018, 11(6), 1036; https://doi.org/10.3390/ma11061036
Received: 2 May 2018 / Revised: 4 June 2018 / Accepted: 16 June 2018 / Published: 19 June 2018
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Abstract
Ag nanowire (NW) networks have exquisite optical and electrical properties which make them ideal candidate materials for flexible transparent conductive electrodes. Despite the compatibility of Ag NW networks with laser processing, few demonstrations of laser fabricated Ag NW based components currently exist. In
[...] Read more.
Ag nanowire (NW) networks have exquisite optical and electrical properties which make them ideal candidate materials for flexible transparent conductive electrodes. Despite the compatibility of Ag NW networks with laser processing, few demonstrations of laser fabricated Ag NW based components currently exist. In this work, we report on a novel single step laser transferring and laser curing process of micrometer sized pixels of Ag NW networks on flexible substrates. This process relies on the selective laser heating of the Ag NWs induced by the laser pulse energy and the subsequent localized melting of the polymeric substrate. We demonstrate that a single laser pulse can induce both transfer and curing of the Ag NW network. The feasibility of the process is confirmed experimentally and validated by Finite Element Analysis simulations, which indicate that selective heating is carried out within a submicron-sized heat affected zone. The resulting structures can be utilized as fully functional flexible transparent electrodes with figures of merit even higher than 100. Low sheet resistance (<50 Ohm/sq) and high visible light transparency (>90%) make the reported process highly desirable for a variety of applications, including selective heating or annealing of nanocomposite materials and laser processing of nanostructured materials on a large variety of optically transparent substrates, such as Polydimethylsiloxane (PDMS). Full article
(This article belongs to the Special Issue Selective Laser Sintering (SLS) of Materials)
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Open AccessArticle Pore Structure Characterization of Sodium Hydroxide Activated Slag Using Mercury Intrusion Porosimetry, Nitrogen Adsorption, and Image Analysis
Materials 2018, 11(6), 1035; https://doi.org/10.3390/ma11061035
Received: 22 May 2018 / Revised: 15 June 2018 / Accepted: 17 June 2018 / Published: 19 June 2018
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Abstract
The pore structure of alkali-activated slag has a significant influence on its performance. However, the literature shows insufficient studies regarding the suitability of different techniques for characterizing the pore structure and the influences of Na2O and curing age on pore structure
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The pore structure of alkali-activated slag has a significant influence on its performance. However, the literature shows insufficient studies regarding the suitability of different techniques for characterizing the pore structure and the influences of Na2O and curing age on pore structure development. In pursuit of a better understanding, the pore structure of sodium hydroxide activated slag paste was characterized by multiple techniques, e.g., mercury intrusion porosimetry (MIP), nitrogen (N2) adsorption, and scanning electron microscopy (SEM) image analysis. The sodium hydroxide activated slag pastes were prepared with three different contents of Na2O (Na2O/slag = 4, 6, and 8%) and cured for different times up to 360 days. The microstructure observation reveals that outer C–(N–)A–S–H and inner C–(N–)A–S–H grow successively around the reacting slag grains, along with crystalline reaction products which are formed in the empty coarse pore space. The increase of Na2O content and curing age lead to a finer pore structure. The MIP measurements show that the total porosity drops about 70% within the first day, and that one peak at most, corresponding to gel pores, was identified in the differential curves of all the investigated samples from 1 to 360 days. On the contrary, only one peak, corresponding to capillary pores, was identified by SEM-image analysis. The differential curves derived from N2 adsorption generally reveal two peaks, and the trend that the pore diameters of those two peaks vary with curing age depends on the content of Na2O. Compared to Portland cement, sodium hydroxide activated slag has a higher pore space filling capacity (χ, Vproducts/Vslag-reacted), while the capacity decreases with increasing Na2O content and curing age. Full article
(This article belongs to the Section Porous Materials)
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