Preparation and Properties of Preceramic Oligoborosilazanes

• Published in: Inorganic materials 2021-12, Vol.57 (12), p.1292-1299
• Main Authors: Zhukova, S. V., Storozhenko, P. A., Ryzhova, O. G., Drachev, A. I., Kuznetsova, M. G., Timofeev, P. A.
• Format: Article
• Language: English
• Subjects: Ammonia; Boranes; Ceramics; Chemistry; Chemistry and Materials Science; Crosslinking; Hydrogen atoms; Industrial Chemistry/Chemical Engineering; Inorganic Chemistry; Materials Science; Pyrolysis; Thermal stability; Weight loss
• ISSN: 0020-1685; 1608-3172
• DOI: 10.1134/S0020168521120153

— Preceramic oligosilazanes have been prepared and their properties have been investigated before and after modification with ammine borane, BH 3 NH 3 . We have studied the influence of temperature and modification process time on the formation of Si–N–B groups in the oligosilazanes. The results demonstrate that the degree of replacement of hydrogen atoms in ammine borane depends on temperature and that the process is dominated by the replacement of hydrogen atoms in –NH 3 groups in the range 60–65°C and in ‒BH 3 groups in the range 70–140°C. Increasing the percentage of boron in the oligosilazanes is accompanied by an increase in their molecular weight. Ammine borane and its derivatives act as cross-linking agents, leading to an increase in the inorganic residue yield of the oligoborosilazanes during pyrolysis below 850°C. In the case of pyrolysis at temperatures of up to 1500°C, the thermal stability of SiBCN ceramics is better than that of SiCN ceramics, with a decrease in weight loss by a factor of 3.5.