Synthesis and characterization of graphite-like B–C–N materials of composition CNx(BN)y (x ≪ 1, y ≦ 1)

Abstract

Various graphite-like B–C–N materials were synthesized in the precursor pyrolysis system of boron trichloride and nitrogen-containing materials such as heptaazaphenalene derivatives, carbodiimides, amines, nitriles and cyanamides. The materials obtained were described with a formula of CN_x(BN)_y and CB_x(BN)_y consisting of CN_x and (BN)_y segments. A combination of chemical decomposition and structural analysis elucidated that the segment structure of CN_x(BN)_y contains local bonds of (–CC–)_n–N, B–N–C and B–N pairs but no C–B bonds. A miscible blend structure model was expected by analogy with hybrid materials. Compositions and yields of the materials were closely related to the properties of chemical reaction, nitrogen evolution and graphitization of the starting materials. In particular, B–C–N materials with high BN content were prepared in small quantities from the heptaazaphenalene polymers, and the materials with low BN content were produced from teteracyanoethylene in nearly 100% yield. The materials were oxidized to boron oxide from 500 °C to 950 °C, however, under an inert atmosphere they were stable to at least 1200 °C.