High purity silicon carbide （SIC） powder was synthesized in-situ by chemical reaction between silicon and carbon powder. In order to ensure that the impurity concentration of the resulting SiC powder is suitable for...High purity silicon carbide （SIC） powder was synthesized in-situ by chemical reaction between silicon and carbon powder. In order to ensure that the impurity concentration of the resulting SiC powder is suitable for high-resistivity SiC single crystal growth, the preparation technology of SiC powder is different from that of SiC ceramic. The influence of the shape and size of carbon particles on the morphology and phase composition of the obtained SiC powder were discussed. The phase composition and morphology of the products were investigated by X-ray diffraction, Raman microspectroscopy and scanning electron microscopy. The results show that the composition of resulting SiC by in-situ synthesis from Si/C mixture strongly depends on the nature of the carbon source, which corresponds to the particle size and shape, as well as the preparation temperature. In the experimental conditions, flake graphite is more suitable for the synthesis of SiC powder than activated carbon because of its relatively smaller particle size and flake shape, which make the conversion more complete. The major phase composition of the full conversion products is β-SiC, with traces of α-SiC. Glow discharge mass spectroscopy measurements indicated that SiC powder synthesized with this chemical reaction method can meet the purity demand for the growth of high-resistivity SiC single crystals.展开更多
Soft magnetic metallic materials have been widely used for absorbing electromagnetic wave.Flaky Fe 86 t Si t Al 14（t=9,11,14 and 16） alloys powders were prepared from melt-quenched ribbons by annealing and milling.I...Soft magnetic metallic materials have been widely used for absorbing electromagnetic wave.Flaky Fe 86 t Si t Al 14（t=9,11,14 and 16） alloys powders were prepared from melt-quenched ribbons by annealing and milling.In a previous report we discussed the order-disordered structure of this alloys.In this article,we studied their electron structure.Covalence electron numbers of（111） and（100） plane increase with increasing Si content but Bohr magneton decreases.Complex permittivity and complex permeability are both decreased with increasing Si content t.The lowest value of reflectivity among the four alloys is originated from Fe 70 Si 14 Al 14.The peak values of reflectivity are all lower than 10 dB,and the absorbing frequency range（R 10 dB） increases from 1 to 2 GHz when t reaches 16.展开更多
文摘High purity silicon carbide （SIC） powder was synthesized in-situ by chemical reaction between silicon and carbon powder. In order to ensure that the impurity concentration of the resulting SiC powder is suitable for high-resistivity SiC single crystal growth, the preparation technology of SiC powder is different from that of SiC ceramic. The influence of the shape and size of carbon particles on the morphology and phase composition of the obtained SiC powder were discussed. The phase composition and morphology of the products were investigated by X-ray diffraction, Raman microspectroscopy and scanning electron microscopy. The results show that the composition of resulting SiC by in-situ synthesis from Si/C mixture strongly depends on the nature of the carbon source, which corresponds to the particle size and shape, as well as the preparation temperature. In the experimental conditions, flake graphite is more suitable for the synthesis of SiC powder than activated carbon because of its relatively smaller particle size and flake shape, which make the conversion more complete. The major phase composition of the full conversion products is β-SiC, with traces of α-SiC. Glow discharge mass spectroscopy measurements indicated that SiC powder synthesized with this chemical reaction method can meet the purity demand for the growth of high-resistivity SiC single crystals.
基金State Key Laboratory of Electronic Thin Films and Integrated Devices for support of this work (KFJJ200815)supported by the Scientific Research Fund of Sichuan Provincial Education Department,China (08ZA026)Talents Project of Xihua University,China (R1020106)
文摘Soft magnetic metallic materials have been widely used for absorbing electromagnetic wave.Flaky Fe 86 t Si t Al 14（t=9,11,14 and 16） alloys powders were prepared from melt-quenched ribbons by annealing and milling.In a previous report we discussed the order-disordered structure of this alloys.In this article,we studied their electron structure.Covalence electron numbers of（111） and（100） plane increase with increasing Si content but Bohr magneton decreases.Complex permittivity and complex permeability are both decreased with increasing Si content t.The lowest value of reflectivity among the four alloys is originated from Fe 70 Si 14 Al 14.The peak values of reflectivity are all lower than 10 dB,and the absorbing frequency range（R 10 dB） increases from 1 to 2 GHz when t reaches 16.
