Preparation, microstructure and property of zinc-substituted hydroxyapatite/magnesium biocomposite

Zinc-substituted hydroxyapatite (Zn-HA, Ca10-xZnx(PO4)6(OH)2) is used as the modified material of hydroxyapatite (HA, Ca10 (PO4)6(OH)2). In this work, Zn-HA with Zn contents of 10-30 mol% was used to produce Zn-HA/Mg composites by powder metallurgy. The calculated results showed that the crystallite size and lattice parameters of Zn-HA powders varied with the contents of 0-30 mol% Zn, confirming that the divalent Zn2+ ions can substitute Ca2+ ions in HA. Furthermore, the microstructure, mechanical property and electrochemical corrosion behavior of Zn-HA/Mg composites were investigated by SEM, compression tests, and electrochemical corrosion tests, respectively. The results indicate that the highest density and lowest porosity are obtained and the optimal mechanical property and corrosion resistance are achieved in the Zn-HA/Mg composites with 20 mol% Zn.

Study on Properties and Application of PG/CS Composite PCMs

Tris (hydroxymethyl) ethane (PG) as a phase change material, micro-porous xonotlite (CS) as matrix, PG/CS composite PCMs were prepared by melt-soaking method, and the effect of micro-porous structure of xonotlite on heat absorption capacity, bending strength and insulation performance of composites, and the exudation of PG was studied. Otherwise, for the work environment and characteristics of propulsive device of vehicle, this paper explored the feasibility that phase change materials (PCMs) worked as the insulation material in short-time insulation system of the vehicle. Experimental results show that, when the most probable pore diameters of xonotlite was not less than 63nm, the composites presented better and almost same absorption capacities of matrix (CS) to PCM (PG) in different composites; when up to 85nm, the composite exhibited the lowest leakage rate (less than 5%), the optimal mechanical property and thermal insulation performance. This Study proposed a new idea for the design of the insulation material in the thermal protection system of propulsive device of vehicle.

Effect of Magnetic Field on Microstructure and Properties of Magnesium Alloy Welded Joint with GTAW

In this investigation, in order to research the influence of magnetic field on microstructure and properties of magnesium alloy welded joint, the AZ31 magnesium alloy plates which was 5mm were welded by GTAW under longitudinal magnetic field. The tensile test, hardness test and SEM were taken place to analyze the properties and microstructure of welded joint under different magentic field parameters. The acting mechanism of magentic field on welded joint was studied. The results show that: External magnetic field can improve the properties of magnesium alloy welded joint which is welded by GTAW. The optimal mechanical property will be obtained when Im=2, f=20Hz, which the ultimate tensile strength is 231Mpa and the micro-hardness is 76.2HV.The magnetic field can produce electromagnetic stirring, which can refine crystal grain through breaking the pine-tree crystals with proper magnetic field current and frequency. The properties of welded joint will been improved by these fine crystal grain.

Research on the Molding Parameters for Low Pressure Sheet Molding Compounds

Molding parameters are significant for compression molding. In this paper, the molding process for low pressure sheet molding compounds thickened by crystalline unsaturated polyester was investigated. The optimal molding parameters such as molding temperature, molding pressure and curing time were determined by orthogonal test. And the effect of molding parameters on flexural strength and surface quality of molded parts were also studied. Results showed that when the molding temperature was 115°C, the pressure adding time was beginning at 15s after LPMC was put into the die cavity, the moving time of press column was 15s at the last 25mm and the pressure keeping time was 6min, LPMC gained optimal mechanical property and surface quality.