Boron-modified poly(propenylsilazane)-derived Si–B–C–N ceramics: preparation and high temperature properties

Boron-modified poly(propenylsilazanes) [B{C3H6Si(CH3)NH}3]n are synthesized via both ammonolysis of B(C3H6Si(CH3)Cl2)3 (monomer route) and hydroboration of [(H2CCHCH2)Si(CH3)NH]n (n=3, 4) (polymer route) and subsequently transformed into ceramic materials by pyrolysis up to 1400 °C. Thermogravimetric analysis of the as-obtained materials as well as X-ray diffraction of annealed samples were performed to investigate high temperature properties, revealing the stability of the materials toward thermal degradation up to 1800 °C and the presence of silicon nitride at 1800/2000 °C. The crystallization is additionally investigated by transmission electron microscopy. SiC crystallization is observed first, followed by the evolution of a composite material which is composed of a turbostratic BNC matrix embedding SiC and Si3N4 nanocrystals.