以透射电镜的先进分析方法为主要手段, 对前驱体制备Si-B-C-N陶瓷(T2-1)材料纳米尺度的微结构及其晶化过程进行了研究. 结果表明, 在直接经过1400℃热解后, 所得到的T2-1样品出现了非均匀的SiC和Si3N4的结晶以及石墨化或BCN的团簇. 为了有效保持材料强度并抑制高温易分解Si3N4相的析出, 对T2-1在1000℃热解以进行对比实验. 显微结构的观察表明, 经过低温热解的基体出现了均匀成分分相; 即使再经过1400℃下的退火, 仍能有效抑制Si3N4纳米晶的析出, 从而增进了材料的高温稳定性.
Advanced TEM techniques were applied for studying precursor derived Si-B-C-N (T2-1) ceramics, which provided a direct view of nano-scaled microstructure evolution and nucleation. The results showed that after directly pyrolysis at 1400℃, SiC and Si3N4 nano-crystals, graphitic and BCN clusters nucleated from T2-1 amorphous matrix. In order to avoid the high temperature decomposition caused by the reaction between carbon and Si3N4, as well as to keep the strength of material and also improve its high temperature stability, T2-1 was also produced at relatively lower pyrolysis temperature (1000℃) for study and comparison. Different from T2-1 pyrolyzed at 1400℃, the results of microstructure show that lower pyrolysis temperature efficiently retards the crystallization of Si3N4, which is approved by the samples further annealed at 1400℃. Such phenomenon is believed being caused by early stage phase separation, which only provides SiC an advantage of nucleation. Thus, pyrolysis process is approved becoming one of the effective methods not only to control microstructure development, but also to improve the high-temperature stability of this material.
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