Synthesis of High Purity Boron Carbide Powders via Sol-Gel Method

In the present study, highly crystalline boron carbide (B₄C) powders without excess carbon were fabricated by using a modified sol-gel method. Condensed boric acid (H₃BO₃)-glycerin-tartaric acid products were prepared using different synthesis times ranging from 30 min. to 3h. The condensed gels were calcined at atmospheric conditions followed by a heat treatment at 1500°C for 5 h. in the Ar atmosphere. The effects of starting composition and processing conditions on the phase composition, particle size, size distribution, and morphology of boron carbide powders were investigated. The results showed that (B-O-C) bonds were formed with condensation reaction which confirms the cross-linking of glycerin and boric acid. B₄C particles with varied morphologies (rod, plate, polyhedral equiaxed, and cubic) have a wide-ranged particle size distribution in between 100nm to 30µm. Tartaric acid addition as a gel modifier leads to faster gelation and promotes the formation of road and plate-like B₄C particles. Furthermore, B₄C powders without free carbon was achieved by optimization of processing conditions and starting composition.