Effect of glycerine addition on the synthesis of boron carbide from condensed boric acid–polyvinyl alcohol precursor

Abstract

Boron carbide (B₄C) powder was synthesized by heating a gel precursor with pyrolysis and carbothermal processes. The gel precursor was prepared by the condensation reaction of boric acid (H₃BO₃) and polyvinyl alcohol (PVA) at a weight ratio of 1/2 with the addition of various amounts of glycerine. The effects of glycerine addition on the synthesis of B₄C powder were studied. It was observed that glycerine could promote the condensation reaction and resulted in a pyrolyzed precursor with a much finer distribution of B₂O₃ in the carbon matrix. This led to a significant reduction of residual free carbon in the B₄C powder. Moreover, the morphology of the B₄C powder was also found to be closely related to the glycerine addition.