Materials Science Forum Vol. 1003

Abstract: In aluminate alkaline electrolyte the effect of aluminate on the microstructure and properties and the MAO(micro-arc oxidation) behavior of micro-arc oxide film of AZ91 magnesium alloy was studied. Transmission electron microscope(TEM), energy dispersive spectrum (EDS), X-ray diffraction(XRD), salt spray test and scanning electron microscope(SEM)were used to analyze and characterize the structure and properties of the film. The results show that the concentration of aluminate has an important effect on the tank voltage, corrosion resistance, surface morphology and phase structure of micro-arc oxidation film. The corrosion resistance and film quality of the film were increased first and then decreased, but the surface roughness decreased first and then increased with the increase of aluminate concentration from 5g/L to 30g/L. At our work, the concentration of 10g/L aluminate electrolyte is most favorable to the formation of micro-arc oxide film.

Abstract: Over the past few decades, the use of steel-concrete composite sections has increased globally, in order to take advantage of compression strength in concrete and tensile strength in steel, ensuring its fastening through stress transfer elements denominated shear connectors. The main connection systems endorsed by the current design codes are used by applying welding as fastening mechanism to fix connectors. However, this thermal procedure produces concentration of residual stresses during cooling process, and risk of perforation in Cold-Formed Steel sections (CFS), affecting the behavior efficiency of the composite sections. In this research, self-drilling screws are proposed as an alternative mechanical system for connectors fastening. An experimental program was carried out to validate capacity and performance of the system, through Full-Scale Beam Tests. According to results, self-drilling screws are a viable alternative to be used as fastening mechanism in shear connectors for CFS and concrete composite sections. Composite system achieved to develop full capacity, even in inelastic range, without disconnection between materials. Self-drilling screws remained fixed on steel shapes without mechanical damage, allowing greater deformations, than structural service conditions.

Abstract: An analytical study on the component-level mechanical functional properties of the thermal structure connecting end frame was conducted, illustrating by advanced composite materials (ACM) C/C and C/SiC. Different grades of component-level experiments and analyses the weakness of composite connecting end frames were carried out, including the screw hole pull-out test, which mainly reflects the features of materials, the bending test of corner beams, and the corner box test with structural characteristics. The failure of different components and the factors have been obtained from this research.

Abstract: It is convenient for designers to get the buckling loads of sparse stiffened panels quickly by using engineering calculation method to analyze the stability of composite stiffened panels, but it is still unable to meet the accuracy requirements of analysis of dense stiffened panels. The buckling loads of stiffened panels are closely related to the buckling modes. Based on capturing and analyzing the Compressive Buckling waveforms of T-shaped densely stiffened panels, this paper presents a formula for calculating the buckling loads according to the geometric coefficients. The results are very similar to those of finite element simulation, and can be used to calculate the buckling loads of sparse and dense stiffened panels with different stiffeners.

Abstract: Low Density and Low Pressure Sheet Molding Compounds (LD-LPMC) were prepared by using magnesium oxide paste and crystalline polyester as thickening system to reduce molding pressure and Hollow Glass Microspheres (HGM) as fillers to reduce the density. The molding pressure of LD-LPMC was investigated. The effects of HGM content (0%, 3.8%, 7.6%, 11.4%, 15.2%, 19.0%) on the density, flexural strength and thermal conductivity of LD-LPMC were studied. The results showed that 2-4Mpa was the best molding pressure for the composite materials. With the increase of HGM content, the density, flexural strength and thermal conductivity of LD-LPMC decreased. The thermal conductivity increased with the increase of temperature. When the molding pressure was 3Mpa and the content of the HGM was 7.6%, the density decreased by 13.6%, the flexural strength only decreased by 23.3% and the thermal conductivity (40°C) also decreased by 11.5%, which reflected the low density, high strength and good thermal insulation performance of LD-LPMC.

Abstract: Natural organic matter (NOM) is easily soluble in surface water and difficult to be removed thoroughly. In this paper, polyaluminum chloride-polyacrylamide (PAC-PAM), as a new water treatment material, was proposed to solve this problem by coagulation treatment. The performance, mechanism and kinetic process of NOM removal were investigated systematically. Results showed that the optimum dosage of PAC and PAM was 10 mg/L and 0.5 mg/L for NOM removal of Yellow River water. In this condition, NOM could be removed effectively due to positively charged PAM addition. The size, growth rate and recovery factor of flocs generated by PAC-PAM reached 419 μm, 34.9 μm/min and 0.48, respectively, while only 355 μm, 27.9 μm/min and 0.31 were obtained by PAC. Moreover, the adsorption and bridging effect of PAM assisted the formation of multi-branched flocs, which brought fast settle velocity and low turbidity of supernatant after coagulation.

Abstract: Precious metal Pd are widely used in high-tech industries due to their scarcity and special properties. In this paper, 2-methylimidazole zinc salt (ZIF-8)/PVDF hybrid membrane was successfully synthesized by self-assemble method. The effect of polyarcylic acid sodium (PAAS) and polyethyleneimine (PEI) as complexing agents was investigated. The rejection rate of hybrid membrane under different polyelectrolyte-metal complexing ratios and their extraction performance under different concentration were examined.

Abstract: In this study, the ultrafine copper-based powders were fabricated by a facile two-step chemical reduction method. Glucose (C₆H₁₂O₆) and ascorbic acid (AA) were taken as a pre-reductant and a second reductant, respectively. Polyvinylpyrrolidone (PVP) was applied as the capping agent. Effects of parameters, such as glucose content, PVP content and PH value on the ultimate reduction products were analyzed. Microstructure and composition of the products were characterized by scanning electron microscope (SEM), transmission electron microscope (TEM) and X-ray diffraction (XRD). It was found that when the amount of glucose was increased from half to full and then excessive, the powder gradually changed from flaky to spherical, from pure copper powder to a mixture of copper and cuprous oxide (Cu₂O). With the amount of PVP increasing from 0g to 0.64 g, the shape of the pure copper powder changed from cubic to spherical or HYPERLINK "javascript:void (0);" icosahedron. When the PH value changed from 10-14, the powder changed from spherical to regular octahedron and Irregular polyhedron, from pure copper powder to pure cuprous oxide powder. Therefore, copper-based powders with different morphologies and different compositions can be prepared by changing PH value and the amount of reductant.

Abstract: Fe₃O₄-APTES-CS₂ was prepared by modification of Fe₃O₄ with 3-aminopropyltriethoxysilane (APTES) and carbon disulfide (CS₂). Lipase was covalently bonded to Fe₃O₄-APTES-CS₂ to obtain the immobilized lipase Fe₃O₄-APTES-CS₂-lipase. The textural characteristic of Fe₃O₄-APTES-CS₂-lipase was assessed by scanning electron microscopy. The optimal immobilization conditions were 2.5 mg/mL lipase, pH 7.0, 35 °C, 3 h. The loading amount of lipase was 119.0 mg/g carrier. The immobilization efficiency reached 57%. (R)-(+)-N-acetyl-1-methyl-3-amphetamine was synthesized by Fe₃O₄-APTES-CS₂-Li- pase. The conversion, enantiomeric excess of (R)-(+)-N-acetyl-1-methyl-3-amphet-a- mine and E value reached 36.8%, 98.5% and 132, respectivel.

Abstract: This article proposes the differential BJH equation based on the principles of multilayer adsorption and capillary condensation, which was simplified by theoretical investigation and experiments. This work indicates that the differential function of isotherm and the differential function of pore size to relative pressure determine the pore size distribution of porous media. The differential BJH model can be used to explain the source of the false peak in pore size distribution and to calculate the pore size distribution of different shapes of pores in a porous media with a porous structure. It has an excellent application prospect in the characterization of complex pore structure represented by shale.