Applied Mechanics and Materials Vols. 341-342

Abstract: Introducing the main compositions and properties of fly ash, and review extraction methods of Si,Al and Fe from fly ash, compare the molecular structure and water treatment results among polysilicate flocculants, PFS and PAM, describe preparation methods, conditions and water treatment results of the polysilicate flocculants with the extracts. At last, providing some advices on how to gain flocculants with better remarkable coagulant performance.

Abstract: Chemical reaction kinetic model of hydrogen production from DME partial oxidation by plasma reforming was found. Mole fractions of main products of DME partial oxidation by spark plasma as the function of inlet gas flow rate were calculated at atmospheric pressure and ambient temperature. Comparing the results of calculation and experiment, the model was proved to be correct. The mechanism research was done by the method of sensitivity analysis and rate of production. The reduced mechanism which includes 16 species and 13 radical reactions was done. The calculation results of reduced mechanism and detailed mechanism were close. The result shows that the reduced mechanism can be used in chemical reaction kinetic calculation of hydrogen production from DME partial oxidation by spark plasma reforming.

Abstract: Studying the deformation and fracture properties of soft materials can not only provide insight into the physical mechanisms underlying their superior properties and functions but also benefit the design and fabrication of rubberlike materials. In this paper, an application of the experimental digital moire method to determine the damage zone around crack tip for rubberlike material is presented. The measurement principles and the basic procedures of the method are explained in detail. The deformation of crack tip fields in the damage zones is analyzed using the sector division mode. Finally, an analysis of the damage zone is proposed to describe crack-tip fields in rubber-like materials with large deformation.

Abstract: Equal channel angular extrusion (ECAE) is a process used to introduce severe plastic deformations (SPD) to processed materials with the aim of improving their mechanical properties by reducing the grain size. In order to investigate the effect of die angle on stress and strain produced by ECAE, a new die was designed and the finite element analysis (FEA) was carried out to simulate the ECAE process. The new die is comprised of one internal mold, two external molds and one pressure rod. The main advantage of new die is it can be used for different die angle wihout changing the external mold. As a reult, the new die design reduces the tool cost and improve the ECAE process efficiency. The FEA results show that shear deformation occurred during ECAE, and the maximum effective strain was about 1.669 locating at bottom of the workpiece.

Abstract: CR is often used to make the foreskin material transport belts, wires, cables, and the manufacture of oil hose, gaskets, equipment and chemical resistant bushing. EPDM is often used to produce heat-resistant conveyor belts, cables, wires, anti-corrosion lining, gaskets, waterproof sheet, door and window seals, etc. The same hardness and different proportions of CR/EPDM blends with steel under dry friction pair as the research object to seek friction characteristics of different formulations of rubber with steel metal in the dynamic coordination. Friction test at a constant low load, constant temperature, the different mixing ratio of CR/EPDM blends, friction, wear, friction coefficient variation with engine speed. The test results to a reasonable choice of conveyor belts to improve the overall efficiency and life of rubber - metal friction pairs.

Abstract: AZ31 magnesium alloy was welded by the YAG laser. The plasma of laser welding was studied by the spectra and the plasma temperature was also calculated. The relationship between the welding parameters and plasma temperature was studied. The paper shows that the cooling effect of the plasma using helium is significant. Laser plasma temperature decreases from the center to the periphery and the temperature in the center is higher than 9000K. The evaporation of Mg element concentrates in the center of the laser plasma.

Abstract: We investigate the electronic structures and optical properties of ZnO with antisite defects O_Zn using the density function pseudopotential method. Our results show that the Fermi level shifts into the conduction band after introducing one or two O_Zn defects into ZnO supercell, indicating that the system displays a metallic-like characteristic. Moreover, the antisite defects lead to a redshift of the optical absorption edge and obvious optical absorption in the visible light region. Especially, the optical properties are influenced by the configurations of two O_Zn defects in our considered ZnO supercell. The strongest optical absorption occurs when the two defects are connected by-Zn-O-Zn-bond in the ab plane. These findings are possibly applicable for designing new optoelectronic and photoelectrochemical devices with improved low energy light absorption.

Abstract: Using layer-by-layer (LBL) assembled method, multilayer films containing multiwall carbon nanotubes (MWNTs) and redox polymer were successfully fabricated on a screen-printed carbon electrode. X-ray photoelectron spectroscopy (XPS) and field-emission scanning electron microscopy (FE-SEM) were used to characterize the assembled multilayer films.

Abstract: ZnO single crystals were prepared and then sequentially annealed from 573 to 1073 K in air atmosphere. Optical transmittance spectra (OTS), X-ray excited luminescence (XEL), and photoluminescence (PL) were measured before and after each step of annealing. The lower temperature annealing can enhance the emission but hardly affect the optical transmittance. Contrarily, higher temperature treatments ameliorated the transmittance but degraded emission. Based on experimental results, the blue and green emissions, as well as the 400-500-nm absorption were assigned to isolated zinc interstitial, zinc vacancy and oxygen vacancy in ZnO, respectively. In addition, the defect complexes play important role on optical properties of ZnO crystal. Our results provide further insight into understanding defects and defect complexes in ZnO crystals.

Abstract: Based on the chaos theory and related algorithm, largest Lyapunov analysis of current of laser-twin-wire pulse MIG welding process are performed from the point of view of nonlinear time sequence. Largest Lyapunov exponent (LLE) of characteristic current under different laser power were calculated, meanwhile synchronous high-speed photography was adopted to observe arc shape and droplet transfer. The results indicate that arc shape and the force state of droplets changes as a result of interactions between laser plasma and arc plasma. Addition of low power laser intensifies the interplay of two arcs, which decreases the stability of welding process. When laser power reaches to a certain extent, a stable cathod spot and a conductive channel are obtained for arcs. Stable welding process and small welding spatter are acquired.