Synthesis and Ceramic Conversion of a New Organodecaborane Preceramic Polymer with High-Ceramic-Yield

Boron carbide is one of the hardest materials known, with diamond-like mechanical properties and excellent chemical stability. It is wildly used in military defense area, nuclear industry, aerospace technology, etc. Precursor-derived ceramics have made it easier to produce pure boron carbide in processed forms and expand its applications. The challenge of this method is the synthesis of precursor polymer with high-ceramic-yield. The aim of the present work is to develop a new poly(6-norbornenyldecaborane-co-decaborane) [P(ND-co-D)] copolymer, which was successfully synthesized via ring-opening metathesis polymerization of 6-norbornenyldecaborane and tandem hydroboration with decaborane. The obtained light-yellow powder displayed good solubility, and was fully characterized by NMR, FT-IR and GPC analysis. Thermogravimetric analysis demonstrated that the char yield was up to 79%. The polymer-to-ceramic transformation process and pyrolysis mechanism has shown that the rearrangement of carbon chains of P(ND-co-D) mainly occurred in the temperature range of 350 °C~470 °C. Furthermore, the crystallization behavior and microstructures of derived ceramics were studied by XRD and SEM. Nano-sized boron carbide powders were prepared by pyrolysis of P(ND-co-D) under argon at 1400 °C for 2 h, while the structure and morphologies of the obtained rhombohedral B₄C were investigated.