Synthesis of nanocrystalline boron carbide from boric acid–sucrose gel precursor

A novel method, based on the combustion of boric acid–sucrose xerogel was developed to synthesize nanocrystalline boron carbide powder. This xerogel was pyrolyzed at 1273 K. Boron carbide was obtained by heating this precursor at 1823 K. The yield of boron carbide was improved by the use of a novel graphite crucible designed for this purpose. The xerogel and the precursor were characterized by using Fourier transform infrared spectroscopy. The constituent phases were identified by using X-ray diffraction while their elemental composition was established with the help of chemical assay. The microstructure of the final product was examined with the help of scanning electron microscopy and transmission electron microscopy. This study demonstrates that the yield of boron carbide would be enhanced to about 48% while the free carbon content in the final product could be reduced to about 6 wt%. These are significant improvements over similar studies reported so far on the gel-based preparation of boron carbide.