碳化硼微粉的低温合成

摘要

以聚乙烯醇和硼酸为原料,首先合成聚乙烯醇硼酸酯前驱物凝胶,然后将前驱物热解及碳热还原制备碳化硼粉末.考察了聚乙烯醇与硼酸的物质的量比,前驱物热解温度,碳热还原温度以及还原时间等因素对碳化硼合成的影响.采用IR、化学分析、XRD、离心粒度分析、SEM等方法对中间物及产物进行了表征,确定了中间物及产物的组成、物相、粒度分布及形貌.研究结果表明:前驱物合成的适宜原料配比是n(聚乙烯醇)∶n(硼酸)=4∶1；前驱物在600℃下热解2h,在1 300℃下碳热还原2h,得到粒径为10 μm左右的碳化硼微粉.%Polyvinyl borate gel was prepared with polyvinyl alcohol (PVA) and boron acid as raw materials, which was employed as precursor for preparing boron carbide and then it was pyrolyzed and reduced to form boron carbide powder by carbonthermal process. Effects of amount-of-substance ratio of polyvinyl alcohol to boron acid, pyrolyzed temperature of the precursor, carbonthermal reduction temperature,and reduction time of pyrolyzed precursor on boron carbide synthesis were respectively investigated. Intermediate and product were respectively characterized by FT-IR,chemical composition,XRD, SEM, and particle size analysis etc.. Results indicated that the optimum raw material mix ratio for precursor polyvinyl borate was n[ PVA) : n( boron acid) =4: 1 ;B4C powder with a primary particle size of 10 ftm could be obtained when the precursor was pyrolyzed at 600 °C for 2 h,and then treated at 1300 ℃ for 2 h.