(哈爾濱工業(yè)大學(xué)復(fù)合材料研究所， 哈爾濱 150001)
摘 要: 通過(guò)B2O3-Mg-C體系的自蔓延高溫還原反應(yīng)，成功地制備出了B4C粉。由于Mg 的高揮發(fā)性，Mg與B2O3的反應(yīng)受到環(huán)境氣壓的影響。低壓下燃燒時(shí)，由于Mg的揮發(fā)造成燃燒溫度低于B的熔點(diǎn)，生成的B4C顆粒尺寸約0.4 μm。10 MPa下反應(yīng)物的揮發(fā)受到抑制，使燃燒溫度達(dá)到或超過(guò)硼的熔點(diǎn)，生成的B4C顆粒尺寸約5 μm。在100 MPa下，由于氬氣的熱導(dǎo)率增加，使得熱損失增加，造成燃燒溫度反而較10MPa下有所降低。燃燒溫度曲線在硼熔點(diǎn) 附近出現(xiàn)的等溫線證實(shí)了分步反應(yīng)機(jī)理的存在。
關(guān)鍵字: 燃燒合成 熱還原反應(yīng) 氣壓 B4C
（Center for Composites Materials, Harbin Institute of Technology, Harbin 150001, P. R. China）
Abstract:B4C was fabricated successfully by SHS in B2O3-Mg -C system. The interaction between the reducing agent Mg and B2O3 depends on the surrounding inert gas pressure due to the high volatility of Mg. Under low pressure, the volatility of Mg causes the combustion temperature below the melting point of B and the particle size o f B4C is about 0.4 μm. Under high pressure, the vapourization of Mg is reduced, thus the combustion temperature reaches the melting point of B, and the grains of B4C grow to about 5μm. The higher thermal conductivity of Ar under 100 MPa causes the heat loss increase and the combustion temperature is lower than that under 0.1MPa. The sequential mechanism is supported by an isothermal step observed at the melting point of B in the combustion temperature profile.
Key words: combustion synthesis; thermal reduction reactions; pressure; B4C
