先驱体转化法制备SiBNC陶瓷

Preparation of SiBNC Ceramics by Polymer Pyrolysis

以三氯化硼、甲基氢二氯硅烷、六甲基二硅氮烷为起始原料,通过共缩合路径合成了SiBNC陶瓷先驱体-聚硼硅氮烷(PBSZ),将PBSZ直接在氮气气氛中高温热解可得SiBNC陶瓷。通过元素分析、XPS、NMR、FTIR和XRD等对所得先驱体及相应陶瓷的组成、结构和高温结晶性能进行了表征。结果表明,先驱体的骨架结构为—Si—N—B—,其中,B、N以硼氮六环形式存在,而C则以Si—CH_3形式存在;该先驱体在1000℃下的陶瓷产率为63%,所得SiBNC陶瓷主要由Si_3N_4、BN、SiC等相组成,具有很好的热稳定性能,在1700℃时能够保持非晶态,在1850℃时部分结晶,且其在1500～1850℃间失重仅为3.8%左右。

Polyborosilazane （PBSZ）, a precursor to SiBNC ceramic, was synthesized via cocondensation of methyldichlorosilane （MeHSiCl2）, boron triehloride （BCl3） and hexamethydisilazane （HMDZ）. SiBNC ceramics were obtained by pyrolysing the as-synthesized PBSZ in N2. The chemical composition, structure and high temperature properties of the polymer and ceramics were investigated using EA, XPS, FTIR, NMR, and XRD. The results indicate that the backbone of PBSZ had the -Si-N-B- linkage in the form of borazine and C was in the form of Si-CH3. The ceramic yield of the PBSZ at 1000 ℃ in N2 atmosphere was 63 wt%. The products showed excellent high temperature stability and were fully amorphous up to 1700 ℃. Heating the pyrolyzed products to 1850 ℃ resulted in partially crystallized Si3N4, BN, and SiC phases. The weight loss of SiBNC ceramics from 1 500℃to 1 850 ℃ was about 3.8 wt%.