硅氮烷环体的催化聚合及热解制备Si_3N_4材料

Catalyzed Polymerization of the Cyclic Silazane and Its Thermal Decomposition to Si_3N_4

采用甲基氢二氯硅烷的氨解产物硅氮烷环体(MHSZ)为原料,以四丁基氟化铵为催化剂,制备了高分子量的硅氮烷聚合物(PHSZ),结合红外、核磁、凝胶色谱仪和热重分析了反应时间对合成的PHSZ结构、组成、分子量和陶瓷产率的影响。考察了低温氨气,高温N2气氛处理工艺对热解产物结构和组成的影响。结果表明,随着反应时间的延长,PHSZ高聚物的分子量提高,热失重降低;采用该热解方式PHSZ可转化为含碳量仅为0.5wt%的Si3N4材料,热解样品在1 600℃时完全结晶,晶相主要是α-Si3N4。

A polysilazane PHSZ with high molecular weight was prepared via the polymerization of cyclic si- lazane MHSZ in the presence of tetrabutylammonium fluoride as catalyst. MHSZ was synthesized by the ammonolysis of methylhydrodichlorosilane. Combined with apparatus of IR, NMR, GPC and TGA, the effect of polymerization time on the composition, structure, molecular weight and ceramic yield of PHSZ was studied. The structure and composi- tion of the pyrolyzed products in the atmosphere of ammonia combined with nitrogen were investigated. It is suggested that the molecular weight of the polymer PHSZ improved with the extension of the reaction time and TGA decreased ; PHSZ converts into Si3N4 ceramic matrix composites with a carbon content of 0.5wt%, the product of pyrolysis at 1 600℃ is completely crystallized , the crystal phase is mainly α-Si3N4.