Advanced Materials Research Vols. 299-300

Abstract: PA6 composites filled with nano-SiO₂ were synthesized. The aim of the research article is to study the mechanical and friction and wear behaviour of nano-SiO₂ reinforced PA6 composites. The worn surface of the composite was examined by scanning electron microscopy. The results showed that the addition of nano-SiO₂ can effectively improve the mechancial and tribological properties of the PA6 composites.

Abstract: Cyclic deformation for two magnesium alloys AZ91 and AM50 with different processing status has been performed under total strain amplitude control mode and at room temperature. A serrated flow can be observed in both tensile and compressive directions of the stress-strain hysteresis loop for as-extruded AZ91 and AM50 magnesium alloys. It means that the so-called dynamic strain aging occurs during cyclic deformation. In addition, the dynamic strain aging phenomenon can also be observed in two extruded magnesium alloys subjected to aging treatment as well as the AZ91 alloy subjected to solution treatment. However, the dynamic strain aging seems not to take place in the extruded AM50 alloy subjected to solution treatment because there exists no significant serrated flow behavior in either compressive or tensile direction of the stress-strain hysteresis loop. It is suggested that the occurrence of the dynamic strain aging is associated with collective behavior of many mobile dislocations as well as interactions between solute atoms and dislocations.

Abstract: Equal channel angular pressing (ECAP) was conducted using the die with a 90° angled channel under routes A, B_C and C for hot extruded AZ91 magnesium alloy. Tensile tests were carried out at 300 °C and initial strain rates ranging from 2×10⁻⁴ to 5×10⁻³ s⁻¹. The experimental results show that different routes have obviously effect on elongation to failure. It is found that the highest elongation to failure is 410 % at a strain rate of 2×10⁻⁴ s⁻¹ for the ECAPed AZ91 alloy with route B_C. At the same strain rate, route B_C can bring the greater superplasticitic deformation compared with routes A and C. Moreover, the strain rate sensitivity coefficient m values of about 0.3 to 0.5 are attained for the ECAPed AZ91 alloys with different routes. For the ECAPed AZ91 alloys, the main superplastic deformation mechanism is the grain boundary sliding, while the main accommodation mechanism is the dislocation creep mechanism controlled by the grain boundary diffusion.

Abstract: In the paper, the emulsion graft polymerization is used to prepare stable epoxy resin emulsion by vinyl acetate and polyvinyl alcohol (PVA) as emulsification stabilizer. It is studied for the influence on the properties of emulsion by temperature and dosages of functional monomer, acrylamide and acrylic acid, and initiator. The results show that the optimal conditions: reactive temperature is 75°C, acrylic acid is 2%~4%(mass concentration), acrylamide is 2%~4%(mass concentration) and initiator is 0.7%~0.8%(mass concentration).

Abstract: The interfacial interaction of carbon fiber reinforced polyimide(PI) composites is a very important issue because it is one of the key factors to influence the mechanical properties of materials. In this article, the interfacial interaction among the components in the composites has been studied by three point bending tests. The fracture surface analysis showed the fiber matrix interface dominates the mechanical and tribological properties.

Abstract: Pure anatase TiO₂ spheres with mesoporous structure were prepared by a simple urea assisted hydrothermal process at low temperature. The characterization of TiO₂ was examined by X-ray diffractometer (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM), N₂ adsorption-desorption and ultraviolet visible spectrophotometer (UV-VIS). The TEM and N₂ adsorption-desorption results confirmed that TiO₂ spheres has a mesoporous structure. The surface area of TiO₂ annealed at 400 °C is up to 302.3 m²/g with average pore diameter about 4.1 nm. While after annealed at 500 °C, the average pore diameter of TiO₂ is about 6.8 nm, but the surface area reduces to 142.6 m²/g

Abstract: Against the background of shenyang subway shield tunnel construction, the method of numerical simulation methods are used to analyze the factors of surface subsidence caused by shield construction comprehensively, and the universal finite element program ABAQUS is used to establish mechanical model depended on comprehensive consideration the influence factors of soil warehouses pressure, seepage and groundwater. A dynamic finite element simulation of shield advance process and conclude the surface deformation rule of soil are studied.

Abstract: Statistical values (S′) of phase structure formation factor (S) of alloying elements in cast iron are calculated by the calculation method on statistical value of alloy phases electronic structure parameters based on the empirical electron theory of solids and molecules (EET), and the solidification process of cast iron is discussed by S′. According to the effects of phase structure formation factor (that is S′) on the formation process of graphite, cementite and austenite, electronic structure parameters criterion of graphitization behavior of alloying elements is advanced and the results agree well with the practical cases.

Abstract: Cerium oxide(CeO₂₎ nanoparticles were synthesized via a precipitation method using cerous sulfate, ammonia water and cetyl three methyl brominated ammoniu(CTAB) as raw materials. The effect of thermal treatment temperature and dispersing agent on the crystal structure and morphology were discussed. The structural evolutions and morphological characteristics of the nanoparticles were investigated using X-ray diffractometery, scanning electron microscopy, Fourier transform infrared spectroscopy. The results showed that the broadening of CeO₂ peaks decreases by the increasing in heat-treatment temperature and the dispersing agent playes key roles in microstructure of the CeO₂.

Abstract: The effects of Cu addition on precipitation characteristics in 6082 Al-Mg-Si alloy was investigated by means of DSC、TEM and 3DAP. It was found that addition of Cu has distinct effect on the precipitation and dissolution process of precipitates during heating by DSC measurement, the presence of Cu promotes the formation of GP zone or atomic clusters and accelerates the precipitation of β¢¢ . The precipitation sequence in the 6082 alloy with 0.6%Cu addition is as follows: SSSS atomic clusters/GP-zonesβ¢¢ + Q¢ Q¢.