Papers by Keyword: β-SiC

Abstract: In this research, the effects of main parameters such as speed of agitator, concentration and redium change ratio on the grinding effect were studied by the method of wet-grinding. The powder was characterized and analyzed by means of particle size analysis and scanning electron microscope. The results show that the mechanical grinding method can effectively prepare micro-nanosilicon carbide powder with particle size of about 130nm, the optimum parameter is the rotational speed 1000r/min, the concentration is 30%, the medium change ratio is 75%.

Abstract: The fabrication and thermal physical properties contain thermal conductivity (TC) and coefficient of thermal expansion (CTE) using 40%、50%、60% vol% β-SiC particle reinforced Al composite for electronic packaging respectively have been analyzed. The composites were produced by ball milling and pressing method. The composite which fabricated by tri-sized β-SiC particle with a weight ratio of 17:7:1,vol% of 50% and 60%.The dense and morphology were investigated. The relationship between volume fraction of β-SiC particle and thermal physical properties was discussed. Changed the volume fraction of β-SiC particle will led to a decreasing or increasing of TC and CTE. It found that values of TC and CTE were achieved their maximum balance when using tri-sized β-SiC particle of 160μm ,125μm as well as 38μm with a weight ratio of 17:7:1 and 50%vol of β-SiC particle reinforcing.

Abstract: In this paper, the production of high-performance β/α SiC composite ceramics technology as the goal, by measuring density, we can optimize and determine the best technical ceramic formulations. Because a small amount of β-SiC in α-SiC,the sintered ceramic appeared long axis-like crystals, indicating fracture mode changes from the original transgranular fracture to transgranular fracture mainly and intergranular fracture supplement. The results show that, when added in an amount of 10% β-SiC, SiC ceramics having the best performance.

Abstract: Using high quality carbon raw material,high quality silica raw material , the β-SiC powder are prepared by high-temperature vacuum smelting method. The effects of different materials and electrical power to the product of β-SiC quality has been studied. The microstructure and phase analysis of β-SiC powder samples were observed by Scanning Electron Microscopy and X-ray diffraction. The result shows that the raw materials are better, the product quality are better. In addition, the result also indicates that the β-SiC powder have better quality when the power are 3000W.

Abstract: Zirconium diboride (ZrB₂) is a material of particular interest because of the excellent and unique property combination of high melting point, high electrical and thermal conductivity. In this work, the effect of addition of beta-silicon carbide (β-SiC) on hot pressing sintering of ZrB₂ was investigated. Four compositions were studied with 0, 10, 20 e 30 vol% of SiC. ZrB₂ powder and mixtures were prepared by planetary milling with SiC spheres during 4 h. Samples were sintered at 1850 °C/1h with a pressure of 20 MPa in argon atmosphere. β-SiC has undergone phase transformation to α-SiC during sintering. The addition of SiC increased densification with increasing of SiC content. The total densification of sample was 96.8 % of theoretical density for sample with 30 vol% of SiC and Vickers hardness was 19.9 ± 0.3 GPa.

Abstract: Zirconium diboride (ZrB₂) is a covalent compound that leads the category of ultra high temperature ceramics materials owing to its unique properties. In this work, the effect of addition of beta-silicon carbide (β-SiC) in pressureless sintering of ZrB₂ was investigated. Four compositions were prepared with 0, 10, 20 e 30 vol% of SiC. ZrB₂ powder and mixtures were prepared in by planetary milling with SiC spheres at 4 h. Two sintering temperatures were used, one at 2050 oC/1h and other at 2150 °C/1h. The addition of SiC has promoted an increasing in densification with the increasing of SiC content. The total densification of sample sintered at 2050 oC was 90% of theoretical density for sample with 30 vol% of SiC, while the maximum densification for temperature of 2150 oC was 91,0 %TD.

Abstract: The distributed processing of β-SiC submicron powders were carried out by tetramethyl ammonium hydroxide (TMAH). The effects of dispersant on the dispersion stability of the β-SiC powders were investigated by the particle size, flow characteristics, morphology and other physical properties of the powder before and after dispersed treatment. The results show that the best dispersing state of SiC is obtained by using the ultrasonic 7mins. In these conditions, the suspension solid content of β-SiC is 8%, and the dosage of TMAH is 8wt.%. An optimum amount of TMAH is proved as 8wt.% when the solid content is kept as 8wt.%. The powder particle size has been reduced from 0.73μm to 0.45μm, and its flowability has improved significantly after low temperature drying. The dispersed powder has small particle size, uniform distribution and excellent dispersion stability.

Abstract: Polycrystalline ڂ˽SiC thick film with mm-scaled thickness was deposited on a graphite substrate using a gaseous mixture of SiCl₄ + CH₄ and H₂ at temperatures ranging from 1573 to 1823 K by chemical vapor deposition. Effect of deposition temperature (T_dep) on deposition rate, surface morphology and preferred orientation has been studied. The preferred orientation changed from <111> to <110> with increasing T_dep. The maximum deposition rate (R_dep) of 1125 ڌ̽˰̸⁻¹ has been obtained. The surface morphology has changed from six-fold pyramid to five-fold facet with increasing T_dep.

Abstract: Thick (over 1 mm) β-SiC films were deposited at a deposition temperature of 1823 K and a total pressure of 4 kPa by halide CVD using SiCl₄ and CH₄ as precursors, and H₂ as carrier gas. The maximum deposition rate was 1125 μm h⁻¹. The SiC films showed strong (220) preferred orientation. The grain size increased from 20 to 100 μm with increasing C/Si ratio.

Abstract: Based on the first-principles pseudopotentials and the plane wave energy band method, the adsorption behaviors of CO molecules on β-SiC (001) surfaces have been investigated in this paper. The calculations for stable adsorption site demonstrate that CO molecule is adsorbed at the lattice site of β-SiC. The absorbing energy of CO on SiC (001) surface is 2.984eV while the exclusion energy between CO reaches 2.965eV. The densities of State of CO became wider and it extends to lower energy when they adsorbent atβ-SiC (001) surfaces.