Advanced Materials Research Vols. 148-149

Abstract: The micromechanical properties at bonded Au ball bonds that have undergone three different time intervals of high temperature storage (HTS) have been characterised by using nanoindentation test. 12 indentations have been made at three different locations (Au, IMC and Si area) across the bonded ball bonds to evaluate the variation of hardness with the location of indentation. It was observed that each of the elements and compound that located at the bonded ball bonds exhibit different responses and micromechanical properties upon the nanoindentation tests. Au showed the highest creep behaviour compared to that of IMC and Si. It was observed that the plastic deformation response for Au and IMC were represented in load versus depth profile through the multiple pop-in events that exhibited in loading-unloading curve of Au and IMC. Finally, it was found that the hardness value and the tendency to brittle fracture of IMC were increased with the increment of the HTS time interval.

Abstract: By a simple chemical bath method, new carambola-like structured CuO had been fabricated in a solution composed of Cu(NO3)2, NaOH and hexamethylenetetramine (HMTA). The formation of such structure was caused by in-situ dehydration and separation of flower-like petals composed of several pieces of copper hydroxide sheets. The corresponding electrochemical reactivity of structured CuO has been investigated, which demonstrated the potential application for lithium ion batteries.

Abstract: This paper takes the rear axle cap which is a typical automobile covering part as the research object. 3D and finite element model of it are built, and the drawing process is simulated with Dynaform, then the technological parameters are analyzed and optimized based on the simulation results, finally the part is compared with the one that is processed in practice. The results show that this method is easy and feasible, it not only increase the work efficiency greatly but also improve the quality of products.

Abstract: To improve its surface global performance, 7A52 aluminum alloy was treated by means of supersonic shot peening, then the structure of surface strengthening layer was characterized and its tribological properties were investigated, too. It was found that after having been peened, surface hardness of 7A52 aluminum alloy increased by 80%, surface crystalline grains were refined, a surface compression stress layer with thickness of 320μm was fabricated, which reached maximum 210MPa at the distance of 80~100μm from the top treated surface; The alloy performs superb tribological properties under both unlubrication friction and lubrication friction.

Abstract: Some new techniques include n- shielding, buried channel and field plate are firstly adopted together for design and fabrication of 4H-SiC microwave MESFETs. The testing results show that a relatively broad and uniform transconductance versus gate voltage was obtained using a 0.1m n- shielding. 0.3mm gate periphery device shows good DC and RF performance such as 5.27W/mm power density, 6.7dB power gain and 43% power added efficiency at 2.3GHz under pulse operation. Compared to conventional SiC MESFETs, a gate lag ratio as high as 0.84 can be achieved for the developed devices even under a nearly actual operating condition.

Abstract: Titania nanoparticles were successfully synthesized through an easily controlled and simple autothermal gelation process. Effects of H2O2 concentrations, solvent quantity and dissolving temperature were investigated in detail. DSC–TGA and XRD analysis showed that the synthesized TiO2 nanoparticles were in anatase phase at 400°C and in rutile phase at 650°C. TEM image indicated that the titania nanoparticles were uniform and approximately spherical, the average grain size of the product was about 20 nm.

Abstract: Molecularly imprinted polymer microspheres for selective binding and recognition of atenolol were prepared by means of precipitation polymerization method using methacylic acid as functional monomer and trimethylolpropane trimethacrylate as cross-linker in the presence of atenolol as template molecule in acetonitrile solution. Computer simulation was employed to demonstrate the mechanism of the interaction between methacylic acid and atenolol. The scanning electron microscopy exhibited that the polymers were uniform spheres with the diameter of about 0.6µm. The adsorption properties of atenolol for imprinted microspheres were evaluated by equilibrium rebinding experiments. Scatchard plot analysis revealed that there were two classes of binding sites in the imprinted microspheres. The dissociation constant and the apparent maximum binding capacity were 4.56×10-4mol/L and 186.46μmol/g for the high affinity binding sites, 2.40×10-2mol/L and 4.01mmol/g for the low affinity binding sites. Compared to the structrally analogues, the imprinted microspheres exhibited a high selective reconizable capacity towards the template.

Abstract: Two airfoils of vertical axis wind turbine (VAWT) were designed, and the wind guide vane was added for VAWT. By using Fluent and the environment wind tunnel, some results were simulated and tested for two different types of airfoils and its wind guide vane. The performance data on certain condition was obtained. Research showed that utilization of wind energy with guide vane wind turbine was higher than those without guide vane structure. The performance of airfoil was more excellent than airfoil . Wind guide vane structure is a new structure for wind turbine which will have a wide prospect.

Abstract: The Zn/Sn-composite oxide nanogranules were synthesized via a simple hydrothermal method, and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The results show that the hydrothermal temperature significantly influences the morphology, microstructure, and composition of the as-prepared samples. And the nano-sized ZnO/Zn2SnO4 exhibited high photocatalytic activities on the degradation of methyl orange (MO) under ultraviolet (UV) light irradiation.

Abstract: Uranium doped TiO2 (U-TiO2) nanomaterials, determined by scanning electron micro- graphy (SEM), were successfully synthesized via a simple, effective and environmental benign solid state reaction route. The characterizations via XRD and XPS showed that the uranium has been entered into the framework of anatase TiO2. The DRUV-Vis revealed that the adsorption region of U-TiO2 nanomaterials shifts to the visible light region compared with the pure TiO2. Moreover, the U-TiO2 nanomaterials for photodegradation of quinoline showed a good photocatalytic properties under visible light irradiation. At 298K, within 60 min visible light irradiation, 54.9 % of the initial quinoline was degraded by the U-TiO2 (U/Ti=3:20) catalyst. The visible light degradation rate of the U-TiO2 nanomaterials is negative to the pH value of surface but positive to the visible light absorption range.