Synthesis of 2D Molybdenum Disulfide (MoS2) for enhancement of mechanical and electrical properties of polystyrene (PS) polymer

In this research article, ultrasound assisted exfoliation in a liquid phase production process has been adopted for synthesis of 2D Molybdenum Disulfide (MoS₂). The energetic governing dispersion of Nano sheets in a wide range of solvents has been studied. Nano sheets dispersion in an aqueous media has been prepared with the help of high surface tension solvents like N-Methyl-1, 2-Pyyrolidone (NMP) and Tetrahydrofuran (THF). The dispersion was composed of layers of MoS₂ with some quantities of mono and bi-layer materials were observed. Scanning Electron Microscopy (SEM), X-Rays Diffractometry (XRD), Transmission Electron Microscopy (TEM) and Atomic Force Microscopy (AFM) were used to characterize the samples; SEM clearly evident the microstructure of samples while XRD shows the peaks of filler in the polystyrene composite membrane. AFM confirmed the presence of 2D MoS₂ with 0.9–7 nm thickness range of MoS₂ flake. In order to get the surfactant stabilized dispersed material, the processing was enhanced using prolonged sonication to yield maximized concentration. Liquid phase exfoliation allows dispersion to be cast into thin film by using vacuum filtration assembly. The obtained film is dispersed in solvent and is used in polymers. Two sets of concentrations (0.01, 0.03, 0.05 and 0.07% by wt. and 0.1, 0.3, 0.7 and 0.9% by wt.) were analyzed and it was observed during tensile testing that modulus of elasticity (E), percentage elongation and ultimate tensile strength (UTS) of composite material increases maximum up to 741times, 374 times and 200 times as compared to base polymer (PS), respectively. Furthermore, dielectric constant, dielectric loss and electrical conductivity of PS-MoS₂ were also evaluated and finding clearly pointed out that filler loading of MoS₂ has considerable effects on these properties and maximum value of dielectric constant is 3.6 at 0.9% loading as compared with of pure PS (polystyrene) matrix. On the other hand, variation in dielectric loss from lower to higher frequency is 2.5 × 10⁻² on average which is not so significant. Electrical conductivity was also accounted, and measurement results are indicating that conductivity was almost constant at lower frequency in range of 10⁻¹⁰ due to low field strength, but it increases to 10⁻⁹ value at higher frequency due to hoping mechanism and network formation of filler.     

A note on viscoelastic materials that can age

Materials can stress relax for a variety of reasons, for example stress relaxation in classical viscoelastic bodies and that due to aging or damage. Here, within the context of a specific model we show that the stress relaxation that is characteristic of viscoelasticity is distinctly different from that of aging.     

Thermodynamics of polycrystalline materials treated by the theory of mixtures with continuous diversity

The physics of polycrystalline materials is described via microscopic processes such as grain boundary migration, grain growth, grain rotation, polygonization (the bending and breaking of crystallites) and evolution of dislocation density. The importance of taking these processes into account lies in their influence on the macroscopic mechanical behaviour of the material. Constitutive equations to describe such phenomena have been proposed in the literature. The main result of this paper is to give a general and thermodynamically consistent approach for such constitutive equations. The framework of the Theory of Mixtures with Continuous Diversity (TMCD) is used. The inclusion of both orientation and grain-size distributions is presented in this paper for the first time. Their introduction requires the formulation of a new and general constitutive theory that is, therefore, given. The method of Lagrange multipliers used in the context of the entropy principle (Liu, Arch. Rat. Mech. Anal. 46, 131–148 (1972)) provides the restrictions of the second law of thermodynamics on the constitutive equations. The success of this work is that all the main results present in the literature can be incorporated in this framework.     

Couplage dans les alliages à mémoire de formeCoupling in shape memory alloys.

This Note concerns the study of the micromechanic behavior of shape memory alloys. The advantage of this model permits the coupling between the martensitic transformation and microstructural evolution observed after cycling. The model makes it possible to obtain consecutives equations, which explain at the same time, mechanical properties and the changing structures during the transformation. It provides original physical results on the global behavior of shape memory alloys. To cite this article: A. Alhamany et al., C. R. Mecanique 332 (2004).     

Unified model equations for microstructure evolution

Unified model equations hidden in microstructure evolution are discovered in this paper. The governing equations in Lifshitz-Slyozov-Wagner theory, and diffusion screening theory are derived with some approximations from the unified model equations. The governing equations in multiparticle diffusion simulation and phase-field simulation in microstructure evolution are also derived from the unified model equations. The advantages and limitations for different theories and simulations in microstructure evolution are compared in detail. This comparison can guide scientists to select computational tools for their needs in microstructure evolution. The unified model equations can be applied in many new technological fields, such as self-assembly in nanoscience.     

Electrode materials and reaction mechanisms in solid oxide fuel cells: a brief review

Following previous surveys of the solid electrolyte ceramics and electrode reaction mechanisms in solid oxide fuel cells, this review is focused on the comparative analysis of electrochemical performance, thermal expansion, oxygen ionic and electronic transport, and durability-determining factors in the major groups of electrode materials. The properties of mixed-conducting oxide phases with perovskite-related and fluorite structures, ceramic–metal and oxide composites, and catalytically active additives are briefly discussed, with emphasis on the approaches and findings reported during the last 10–15 years. The performance of conventional and alternative electrode materials in the cells with ZrO₂-, CeO₂-, LaGaO₃-, and La₁₀Si₆O₂₇-based electrolytes is appraised in the context of potential optimization strategies. Particular attention is centered on the cathode and anode compositions providing maximum electrochemical activity and stability and on the critical aspects relevant for electrode microstructure engineering.     

Effect of gamma irradiation on hydrothermally synthesized barium titanate nanoparticles

The effect of gamma irradiation on hydrothermally synthesized BaTiO₃ nanoparticles has been investigated. Gamma irradiation was carried out at room temperature from 0, 50, 100, 150, 200?kGy to a maximum dose up to 250?kGy, source being ⁶⁰Co gamma radiations. The structure, size and chemical changes of the BaTiO₃ were studied using X-ray diffraction, Fourier-transform infrared spectrophotometry (FTIR) techniques and scanning electron microscopy (SEM). The optical band gap has been computed by UV–Visible spectroscopy data. From the results obtained, it is evident that the gamma irradiation increases the crystallinity, whereas the particle size of BaTiO₃ nanoparticles is altered. UV–Visible spectroscopy shows a noticeable change in the energy band gap due to gamma irradiation. Significant changes in anharmonicity constant computed using FTIR data due to irradiation has been observed. SEM shows the size and deviation from uniformity of particles.     

氟对连铸保护渣熔体、玻璃和晶体微结构的影响

连铸保护渣的物化性质与其结构密切相关。而氟化物对调节连铸保护渣高温物化性能具有重要作用,因此研究氟对多元硅酸盐结构影响有助于深入了解氟的作用特性,进而为环保型连铸保护渣的开发奠定理论基础。论文通过拉曼光谱研究了氟对保护渣高温熔体、玻璃及晶体中硅酸盐微结构单元的影响。结果表明：随着CaF₂含量的增加,硅酸盐微结构单元种类和相对数量发生变化,硅酸盐网络化程度降低,熔体粘度减小;在性能相近的无氟渣和高氟渣中,高氟渣晶体中硅酸盐微结构单元主要为单体结构硅酸盐,无氟渣主要为链状结构硅酸盐。论文研究结果对无氟保护渣的开发具有一定的指导意义。     

Effects of different annealing atmospheres on the surface and microstructural properties of ZnO thin films grown on p-Si (1 0 0) substrates

Effects of different annealing atmospheres on the surface and microstructural properties of ZnO thin films grown on Si (1 0 0) substrates were investigated. X-ray diffraction results showed that the crystallinity of the ZnO thin film annealed in an oxygen atmosphere was better than that annealed in a nitrogen atmosphere. Atomic force microscopy and transmission electron microscopy (TEM) images showed that the surfaces of the ZnO thin films annealed in a nitrogen atmosphere became very rough in contrast to those annealed in an oxygen atmosphere. High-resolution TEM images showed that many stacking faults and tilted grains could be observed in the ZnO thin films annealed in a nitrogen atmosphere in contrast to those annealed in an oxygen atmosphere. Surface morphology and microstructural property variations due to different annealing atmospheres in ZnO thin films are also described on the basis of the experimental results.     

Structural and magnetic properties of nanocrystalline stannic substituted cobalt ferrite

The structural and magnetic properties of the spinel ferrite system Co_1+xFe_2−2xSn_xO₄ (x=0.0–1.0) have been studied. Samples in the series were prepared by the ceramic technique. The structural and microstructural evolutions of the nanophase have been studied using X-ray powder diffraction and the Rietveld method. The refinement result showed that the type of the cationic distribution over the tetrahedral and octahedral sites in the nanocrystalline lattice is partially an inverse spinel. Far infrared absorption spectra show two significant absorption bands, around 600 cm⁻¹ and 425 cm⁻¹, which are respectively attributed to tetrahedral (A) and octahedral [B] vibrations of the spinel. Scanning Electron Microscopy (SEM) was used to study surface morphology. SEM images reveal particles in the nanosize range. The transmission electronic microscope (TEM) reveals that the grains are spherical in shape. TEM analysis confirmed the X-ray results. The magnetic properties of the prepared samples were characterized by using a vibrating sample magnetometer.