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

Boron carbide (B 4 C) 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 (H 3 BO 3 ) 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 B 4 C 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 B 2 O 3 in the carbon matrix. This led to a significant reduction of residual free carbon in the B 4 C powder. Moreover, the morphology of the B 4 C powder was also found to be closely related to the glycerine addition. Boron carbide (B 4 C) powder was synthesized by heating a gel precursor with pyrolysis and carbothermal processes.