Advanced Materials Research Vols. 160-162

Abstract: Methane-utilizing mixed culture HD6T was successfully cultivated in a brief non-sterile process using methanol as a sole carbon and energy source for the production of poly-β-hydroxybutyrate(PHB). Shake-flask experiments showed HD6T could grow well in the mineral salt medium with the addition of methanol exposed to the air directly. This non-sterile process and the use of cheap substrates (methanol) can reduce the production costs of PHB. It was found that HD6T grew better and PHB production in a more effective way with an initial liquid methanol concentration of 0.15%(v/v).The lag phase duration, the maximum growth rate, the biomass concentration and the PHB yield, for the optimal conditions were, respectively, 12.03h, 0.04h-1(OD600), 1.54g/l(dry weight), 0.424g/l(dry weight). Methane-utilizing mixed culture HD6T appears to be a promising organism for PHB production.

Abstract: Micro-nanostructure coatings have been attempted to prepare by Electro-spark deposition (ESD) on cast iron substrate. The microstructures and properties of the coating were investigated by X-ray diffractometer (XRD), scanning electron microscopy (SEM) and microhardness tester. The results show that micro-nanosized particles and fine equiaxed structures prevail in the coating. The primary phases of the coating contain Fe3W3C, Co3W3C, Fe7W6 and W2C. Its average microhardness reaches 1290.1 HV. The results of abrasive test demonstrated that the coating had an excellent sliding wear resistance because the superfine particles distributed dispersedly in the coating increased the resistance to micro-cutting and plowing during the wear test, which effectively improves the surface performance of cast iron substrate.

Abstract: Competitive adsorption experiment of fluoride and phosphate on MgAl-CO3 LDHs has been conducted. A series of batch experiments were performed to study the influence of various experimental parameters such as pH, adsorbent dosage and contact time on the adsorption of fluoride and phosphate on MgAl-CO3 LDHs. Three kinetic models have been evaluated in order to attempt to fit the experimental data, namely the pseudo-first order, the pseudo-second order and the Weber and Morris intraparticle diffusion model. The effects of the initial concentration and the addition order of fluoride and phosphate on their adsorption by MgAl-CO3 LDHs were also investigated. The results show that the optimal pH is 4 to 5, adsorbent dosage is 2 g/L and it takes about 2 hours to attain equilibrium. It was found that the pseudo-second order most closely describes the kinetics. The initial concentration and the addition order of fluoride and phosphate influence the adsorption of fluoride to a certain extent, but they have relatively small influence to the adsorption of phosphate on MgAl-CO3 LDHs.

Abstract: Double compound modification was carried out for hypereutectic Al-24Si alloy. The experiment showed that double modification with phosphorus and rare earth can fine the structure of alloy. The complex modifications of phosphorus and rare earth make the coarse block primary silicon obviously refined and the large needle eutectic silicon modified to the fine fibrous or lamella ones. Phosphorus mainly refines the primary silicon. Rare earth can well refine the primary and eutectic silicon, but its modification effect on the eutectic silicon is more obvious. The alloys with the additions of 0.10% phosphorus and 0.9% rare earth have the optimal microstructure. Compared with the unmodified alloy, the primary silicon of alloys can be refined from 93.5 μm to 24.1 μm and the eutectic silicon can be refined from 8.5 μm to 5.3 μm. Mechanism of double compound modification with phosphorus and rare earth is discussed as well.

Abstract: ZnO thin films were deposited on polyimide foil substrates using cathodic vacuum arc deposition technique. X-ray diffraction was used to investigate the influence of bias voltage on the structure of ZnO thin films. The results show that all the samples have (002) preferred orientation. The internal stress of the films is compressive stress which increases with the bias voltage. Fragmentation test shows that the intrinsic interfacial shear strength of ZnO thin film without bias voltage is slightly lower than the shear yield strength of polyimide substrate; the intrinsic interfacial shear strength of ZnO thin film increases with the bias voltage from -50V to -200V, which indicates that bias voltage is beneficial to the enhancement of the adhesion between ZnO films and polyimide substrates. Further increase of the bias voltage to -300V leads to surface damage of the polyimide substrates.

Abstract: In order to solve technological key problem of metallic rubber in the respect of engineering application, based on porous materials theory, this paper explored the method of nonlinear constitutive relationship constructed, thus in view of the effect of heat treatment technology on nonlinear constitutive relationship of metallic rubber, static experiments are made for seven kinds of tempered metallic rubber and seven kinds of untempered metallic rubber, it was found that each coefficient of nonlinear constitutive relationship of tempered metallic rubber was bigger than that of untempered metallic rubber, and the deformation of tempered metallic rubber was smaller than that of untempered metallic rubber. Lastly it concluded that appropriate heat treatment technology could improve mechanical properties of metallic rubber.

Abstract: Through generalizing the method of a decay analysis technique determining the interior solution developed by Gregory and Wan, a set of necessary conditions on the end-data of axisymmetric circular cylinder in cubic quasicrystal for the existence of a rapidly decaying solution is established. By accurate solutions for auxiliary regular state, using the reciprocal theorem, these necessary conditions for the end-data to induce only a decaying elastostatic state (boundary layer solution) will be translated into appropriate boundary conditions for the circular cylinder with axisymmetric deformations in cubic quasicrystal. The results of the present paper enable us to establish a set of correct boundary conditions, and mix boundary conditions of which are obtained for the first time.

Abstract: Thermal fatigue tests are carried out to the notch specimens made of particle-reinforced composites entitled SiCp/A356 between 20°C and 300°C. The thermal elastic-plastic finite element method is used to simulate the stress and strain response at the notch root of the thermal fatigue test specimen, and thus the formation mechanism of residual stress is revealed. Then according to the finite element simulation of the stress-strain, the thermal fatigue strain life curves of SiCp/A356 material are given considering the residual stress. This can give the basis for the thermal fatigue properties study of the particle reinforced composite SiCp/A356 used in high-speed train brake disc.

Abstract: High-voltage insulation space-components are critical to the reliability of traveling wave tube amplifiers on satellite. Unlike in atmosphere, high-voltage components working in space can easily discharge due to insulation molding defects, which will lead to failure of amplifiers. We can solve these problems through adopting epoxy resin matrix composites as filler and applying vacuum-pressure injection molding technology for insulated molding process.

Abstract: In this article the application possibilities of welding simulation for vice-frame components are discussed. A three dimensional finite element model has been developed to dynamically simulate the welding process. The investigations focus on the simulation of the model construction and the welding effect on distortions and its stress. Comparisons of experimental and numerical results show good agreement and that the simulation method is reasonable. The vice-frame is a casting component that comes from a goods wagon bogie. So the procedure of the vice-frame simulation can be used for more complex structures like the side-wall, front-wall, roof, floor plate, and so on. It can help that optimize the welding process and improve the welding quality.