ZrB2 powder has been prepared through carbothermal reduction boronization of zirconia/boron carbide/carbon mixtures heating assisted by microwave. The powder characteristics were investigated by X-ray diffraction (XRD), X-ray fluorescence (XRF), nitrogen absorption (BET model) and scanning electron microscope (SEM). The experiments indicated that excessive B4C is necessary and the carbothermic reaction reacts severely at a higher temperature and complete at 1600oC. The crystallite size has ranged from 50-100 nm, according to the calculated surface area. Highest purity of ZrB2 powder, which was synthesized at 1600oC, is 99.67 wt%. The surface area of ZrB2 powder synthesis at 1600oC is 18.33 m2/g. Vibration of temperature should affect the purity of ZrB2, as the sub reaction acted.
SiC-Al3BC3-cBN composites with different contents of cBN were fabricated by high pressure and high temperature sintering (HPHT) at 1450 °C for 3 min under a pressure of 5.0 GPa using SiC, Al, B4C and C as additives. The effect of SiC content on the density and mechanical properties of SiC-Al3BC3-cBN composites was investigated. X-ray diffraction (XRD) and Scanning electron microscope (SEM) were used to analyze phases and micro-structure of the sintered samples. The hardness of SiC-Al3BC3-cBN composites decreased with the increasing of SiC content, However, the fracture strength of SiC-Al3BC3-cBN composites increased with the increasing of SiC content.
This paper proposes a numerical model of cooling analysis of an injection mold that has an embedded insert. The Boundary Element Method (BEM) is employed because of its popular usage in this area. The key problem in model building is how to involve the independent surface between mold and insert into the BEM equations and how to give the natural boundary conditions on it. This problem is solved by using coupling BEM which provides an attractive alternative in that the natural boundary condition is shifted to the surface between part and mold. So, instead of using the finite differentiation method, the boundary condition can be determined analytically. This is useful in improving the accuracy of cooling analysis.
In the present study, the compatibility and degradability of L-tyrosine derived polycarbonate(PC)/Chitosan(CTS)blend were investigated. The PC was synthesized in our laboratory. Blends of the polymers with compositions 4/1, 3/1, 1/1,1/3 and 1/4 w/w were prepared by solution-casting. The blends were characterized by FT-IR,DSC,XRD,SEM. No obvious two phases were observed. DSC and SEM analysis implied that all those components in consideration were compatible well in the blend formulation systems.Tg of the blends decreased with increasing PEG content. With the increase of the CTS content, the water retention ratio increases from 15% to 61%.
In the present study, the compatibility and degradability of L-tyrosine derived polycarbonate(PC)/Poly(ethylene glycol) blend were investigated. The PC was synthesized in our laboratory. Blends of the polymers with compositions 95/5, 85/15, 75/25,50/50 and 25/75 w/w were prepared by solution-casting. The blends were characterized by FT-IR,DSC,XRD,SEM. No obvious two phases were observed. Analysis of water absorption revealed that the combination of PC and PEG improved the hydrophilicity of PC. DSC and SEM analysis implied that all those components in consideration were compatible well in the blend formulation systems.Tg of the blends decreased with increasing PEG content. With the increase of the soft segment PEG content, the water retention ratio increases from 37% to 83%.
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