Applied Mechanics and Materials Vol. 394

Abstract: Spent coffee grounds (SCG) and coffee silverskin (CS), the two main coffee industry residues, were magnetically modified by contact with an aqueous ferrofluid containing magnetite nanoparticles. The materials were characterized by SEMEDX analysis, X-ray diffraction and FTIR spectroscopy. Batch adsorption experiments were performed to assess their suitability as biosorbents, using methylene blue as a model pollutant. Adsorption equilibrium data were analysed by the Langmuir model, which allowed estimation of the maximum adsorption capacity. The magnetic biosorbents were easily regenerated by treatment with hydrochloric acid.

Abstract: Static adsorption of Sb (III) on a porous biomorph-genetic composite of Fe₂O₃/Fe₃O₄/C (PBGC-Fe/C-B) was studied. The results showed that the kinetic curve of Sb (III) adsorption by PBGC-Fe/C-B had same change trend under initial concentration of 5, 10 and 50 mg/L. The fitting and regression analysis of four kinds of kinetic model indicated that, the adsorption kinetics of Sb (III) by the PBGC-Fe/C-B well follow the pseudo-second-order model (R²>0.9999). At different reaction temperature (25 °C, 35 °C and 45 °C), the adsorption capacity of Sb (III) by PBGC-Fe/C-B both increased with increasing the solution equilibrium concentration. While it showed a declined tendency with temperature increased. The Langmuir isotherm model (R²>0.98) and the Freundlich isotherm model (R²>0.95) had both better fitted with the equilibrium data.

Abstract: The article utilizes thermo-electric performance experiments to study four fixed volume kinds of electrolytes (Tap Water, Mineral Water, Sea Water, and Al₂O₃ Nanofluids) under different operating temperatures, distances and areas of electrodes due to the impact of the output currents. The experimental results showed that the rise in operating temperature will significantly affect the magnitude of the output current because of heat convection inside the fluid. And the output current of the seawater was much larger than those of the nanofluids, tap water and mineral water between 27 °C and 90 °C. Its maximum value was up to 4.2 mA. However, the seawater presented unstable for output current. The Al₂O₃ nanofluids had the most stable among them and its output current was about 1.08 mA. If seawater combined with Al₂O₃ nanoparticles, they will be able to achieve a complementary role in the future development.

Abstract: Magnesium alloys due to their low density, high strength to weight ratio and good impact resistance have been increasingly used in automotive, aerospace and electronics industries. However, the poor ductility and low strength of magnesium alloys limit their usage in impact situations. The dynamic properties are critical to evaluate the materials response in impact situations. In this study, magnesium alloy AZ31B and its composite containing 1.0vol% SiC nanoparticles were subjected to quasi-static and dynamic compressive loading to investigate the influence of strain rate and the presence of nanoparticles on the mechanical behavior. The dynamic compressive behaviors of both materials have been examined over a wide range of strain rate between 700 s^-1 and 2800 s^-1. Compared to quasi-static loading, both materials exhibit significantly higher yield stresses and compressive strength, much better ductility, and thus a higher energy absorption capacity under dynamic compression. Under dynamic loading, the flow stress of both materials first increases with increasing strain rate from 700 s^-1 to 2300 s^-1 but then it decreases when the strain rate is above 2300 s^-1. In terms of nanoparticle addition, its influence on the enhancement of yield stress and ultimate compressive strength are notable while the ductility remains the same resulting in better energy absorption performance of nanocomposite. This indicates that the nanocomposite has potential to replace the existing magnesium alloys for various applications where impact/shock loads are encountered.

Abstract: The tungsten oxide (WO₃) thin films on the indium tin oxide (ITO) glass in this study were produced by applying the electrodeposition method (ED). This method involves adjusting ED time to control the structure, film thickness, and morphology of WO₃ thin films. Furthermore, the crystallization of the WO₃ thin films was controlled by annealing them at 200 °C and 500 °C. The results show that the WO₃ coated glass with non-annealed and annealed at 200 °C has a high transmittance of visible light and anti-infrared characteristics. However, the WO₃ coated glass annealed at 500 °C has high infrared transmittance, with the highest infrared transmittance reaching 85% at the 1000 nm wavelength. To improve the heat collecting efficiency of solar water heaters, the high infrared WO₃ coated glass can be applied to the surface of the heat collecting component.

Abstract: The morphology and structure of nanocrystalline diamond films as well as the plasma chemistry were studied by altering the plasma impedance. These impedances related to electron density were altered via the matching system. Two films were grown by the microwave plasma under different values of the plasma impedance, resulting in low and high electron densities in the plasma. By the use of measurements of plasma impedance and optical emission, the lowering of an inductive component of the impedance, indicating an increasing electron density, encouraged H-radical concentration present in the plasma. As the plasma was changed to the high electron density, Raman spectra of the films showed the sp³ Raman peak shifted from 1325 to 1328.5 cm^-1 with narrower broadening. This behavior arose from an increase in grain size, corresponding to images from a field emission scanning electron microscope. Raman spectra of G-peak position and white light reflectometry showed a reduction in sp² carbon content of the film. The G-peak shifted from 1564 to 1541 cm^-1 and refractive index increased from 1.84 to 2.16. The formation of the films related to the concentrations of H and CH₃ radicals. The plasma impedance affected the radical concentrations.

Abstract: Photonic crystals (PCs) have many applications in order to control light-wave propagation. A novel type of two-dimensional anisotropic PC is investigated band gap and optical properties as a hollow semiconductor nanorod with nematicliquid crystals (LC). The PC structure composed of an anisotropic nematicLC in semiconductor square hollow nanorod is designed using the plane wave expansion (PWE) method and finite-difference time-domain (FDTD) method. It has been used 5CB (4-pentyl-4`-cyanobiphenyl) as LC core, and Tellurium (Te) as square hollow nanorod material.The PC with hollow Tenanorod with nematicLC is compared with the PC with solid Tenanorodand the PC with hollow Tenanorod.

Abstract: Liquid energetic materials were not tested through traditional test methods for thermal sensitivity. Accelerating Rate Calorimeter (ARC) was scientific to test thermal sensitivity of energetic materials. The decompositions of Hexogen (RDX), Octogen (HMX), 2,4,6-Trinitrotoluene (TNT), Nitromethane (NM), Iso-propyl Nitrate (IPN) were studied by ARC. Kinetic and thermodynamics parameters were calculated and analyzed. Temperature corresponding different time to maximum rate under adiabatic condition (θ) was calculated. The results show that the thermal sensitivity of energetic materials is NM>IPN>RDX>HMX>TNT, which suggests ARC could be used in the test of thermal sensitivity of liquid energetic materials.

Abstract: The paper deals with thermal analysis, modeling and simulation of the Shape Memory Alloy (SMA) actuator with temperature sensor. Because the capabilities of analytical description of SMA system are limited, numerical simulations of model have to be performed. Two different numerical models are investigated - lumped and continuous model. Simple parametric lumped model of actuator thermal field is developed in order to describe thermal field at the measuring point. The characteristic parameters of the lumped model are set up according to continuous coupled electric-thermal model made in ANSYS FEM program.