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

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.