碳热还原法结合冰模板法制备氮化硼-碳化硼复合多孔陶瓷  

Preparation of Porous BN–B_4C Composite Ceramic by Ice-template and Carbothermic Reduction Method

作　　者：石存兰[1] 薛文东[1] 刘晓光[1] 李妍[1] 李勇[1] 孙加林[1] 

机构地区：[1]北京科技大学材料科学与工程学院,北京100083

出　　处：《硅酸盐学报》2017年第12期1796-1802,共7页Journal of The Chinese Ceramic Society

基　　金：国家自然科学基金(51602018);北京市自然科学基金(2154052)资助

摘　　要：以六方氮化硼(h-BN)、氧化硼(B_2O_3)和石墨(C)为原料,去离子水为分散介质、甲基纤维素(MC)为分散剂、聚乙烯醇(PVA)为结合剂,通过冰模板法以及碳热还原过程制备了BN–B4C复合多孔陶瓷。结合碳热还原反应过程的热力学变化对产物进行分析。结果表明:当烧结温度为1 350℃时,热力学计算得到反应体系达到平衡时的CO分压为1.45×10~6,此时产物的XRD结果中出现B4C新相,说明在1 350~1 550℃的烧结温度和氮气气氛条件下,石墨可将B_2O_3还原成B4C,得到产物的体积密度和气孔率分别为0.22、0.26、0.28 g·cm^(–3)和94.65%、92.24%、92.10%。产物的微观结构由直通孔结构和部分树枝状孔结构组成,这些多孔结构为碳热还原反应产生的CO气体逸出提供了快速通道。Porous BN-B4C composite ceramic was fabricated by an ice-template route and a carbothermic reduction process with h-BN、B2O3 and graphite as raw materials, deionized water as a suspension, MC as a dispersant, and PVA as a bonder. The carbothermic reduction reactions, and the characterizations of porous composite ceramics at different sintering temperatures were analyzed by X-ray diffraction, transmission electron microscopy, scanning electron microscopy and Fourier transform infrared spectroscopy, respectively. The results show that CO partial pressure is 1.45×10~6 when the reaction system reaches equilibrium at 1 350 ℃, and then B4C appears in the product. It is indicated that B2O3 can be reduced by graphite at 1 350–1 550 ℃ in a flowing nitrogen atmosphere. In this case, the densities and porosities of the samples are 0.22、0.26、0.28 g·cm–3 and 94.65 %、92.24 %、92.10 %. The microstructure of the as-prepared sample is composed of aligned channel structures and several dendritic pores. The porous channels provide rapid pathways for CO gas evolution.

关 键 词：碳热还原法 冰模板法 氮化硼–碳化硼复合多孔陶瓷 合成机理 

分 类 号：TQ321[化学工程—合成树脂塑料工业]