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
This hydrometallurgical method consists of oxidation leaching, sulfide impurities removing, and sulfur dioxide reduction. The crude tellurium powder was treated by H2Oa oxidation for 2.0 h at pH 2.5 when adding 50 ml ...This hydrometallurgical method consists of oxidation leaching, sulfide impurities removing, and sulfur dioxide reduction. The crude tellurium powder was treated by H2Oa oxidation for 2.0 h at pH 2.5 when adding 50 ml H2O2 （30 %） per 100 g raw material, a tellurium recover rate around 91% is achieved. The tellurium leaching ratio can reach 98.9 % under 3.75 mol.L-1 NaOH concentration in liquid-solid ratio of 5：1 at 80 ℃ for 1.5 h. The overall separation of tellurium and other heavy metals is optimum at sulfide dosages of about 1.1 times of the theoretical values. The removal rates of Ag, Ni, Pb, and Cu from the solution are greater than 99.8 %, and As and Se removal rates are 98.6 % and 97.2 %, respectively. Over 99.5 % tellurium can be recovered by SOu reaction when the operation is conducted at 85 ℃ in 6 mol.L-1 HC1 solution. The tellurium powder with size of 〈5 μm and purity of 〉99.999 % is obtained.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financially supported by the Science and Technology Department of Guangdong Province(No.2011B0508000033)
文摘This hydrometallurgical method consists of oxidation leaching, sulfide impurities removing, and sulfur dioxide reduction. The crude tellurium powder was treated by H2Oa oxidation for 2.0 h at pH 2.5 when adding 50 ml H2O2 （30 %） per 100 g raw material, a tellurium recover rate around 91% is achieved. The tellurium leaching ratio can reach 98.9 % under 3.75 mol.L-1 NaOH concentration in liquid-solid ratio of 5：1 at 80 ℃ for 1.5 h. The overall separation of tellurium and other heavy metals is optimum at sulfide dosages of about 1.1 times of the theoretical values. The removal rates of Ag, Ni, Pb, and Cu from the solution are greater than 99.8 %, and As and Se removal rates are 98.6 % and 97.2 %, respectively. Over 99.5 % tellurium can be recovered by SOu reaction when the operation is conducted at 85 ℃ in 6 mol.L-1 HC1 solution. The tellurium powder with size of 〈5 μm and purity of 〉99.999 % is obtained.
基金Project(2020YFC1909800) supported by the National Key R&D program of ChinaProject(1053320210076) supported by the Fundamental Research Funds for the Central Universities,ChinaProject supported by the State Key Laboratory of Powder Metallurgy,China。
文摘在本研究中,以铁品位为68.38%、硅含量为2.33%的优质磁铁精矿为原料通过反浮选获得了铁品位为72.12%、硅含量为0.09%的超纯磁铁精矿。以超纯磁铁精矿为原料,在1075℃下煤基还原18 h、850℃下氢气还原50 min制备了铁品位为99.06%的高纯还原铁粉。高纯还原铁粉的松装密度、流动性和压缩性分别为2.34 g/cm^(3),9.01 s/(50 g)和6.55 g/cm^(3),达到了粉末冶金用铁粉企业标准(MHF/QB-2016)中MHF80·235(优等)级。用高纯还原铁粉通过共沉淀法制备磷酸铁锂,其首次充电比容量达168.20 m A·h/g。铁鳞经过1075℃煤基还原36 h、14 m T磁选、850℃氢气还原60 min得到铁品位为98.47%的二次还原铁粉,其松装密度、流动性和压缩性分别为2.30 g/cm^(3),10.39 s/(50 g)和6.41 g/cm^(3)。与铁鳞相比,超纯磁铁精矿不仅可省去赫格纳斯工艺中的磁选环节,而且其煤基还原和氢气还原环节所需的时间更短,得到的还原铁粉铁品位更高、工艺性能更佳。本文提出了还原铁粉工艺性能的改善机理:还原铁粉的粗颗粒占比和铁品位的提高可以明显改善其松装密度和压缩性,粗颗粒占比的增加也会改善还原铁粉的流动性。
