Effect of saccharides as carbon source on the synthesis and morphology of B4C fine particles from carbothermal synthesis precursors
Crystalline boron carbide powder was synthesized by carbothermal reduction of the condensed product of boric acid and three different carbon sources, i.e., cellulose, glucose, and starch. The effects of structural homogeneity of precursors on the low-temperature synthesis of B4C powder were investigated on the basis of sacchridederiven structural development. The formation of condensed products was confirmed by FTIR and TGA analyses. The conditions suitable for preparation of precursors were optimized. The precursors obtained by thermal decomposition of condensed cellulose products had more homogeneous and fine structure composed of B2O3 and carbon fibers. The dispersion state of B2O3 in carbon matrix of precursors significantly affected the acceleration of synthesis reaction. The formation of B4C in the case of the cellulose precursor started at a temperature of about 1100 °C which is around 150–250 °C lower than that for glucose and starch precursors. The B4C formation completed for cellulose precursor at 1200 °C (one of the lowest temperatures reported for polymeric precursor route) within a short time because the diffusion of reacting species was favored by increasing the contact area of carbon fibers/B2O3. The B4C particles synthesized from glucose and starch precursors were polyhedral. The morphology of B4C particles, synthesized from cellulose precursor, transformed from polyhedral to equiaxed as the synthesis temperature was raised from 1150 °C to 1200 °C. The nitrogen physisorption measurements had revealed that the synthesized B4C powder exhibited the mesopores and the macropores, and the powder synthesized from cellulose precursor had the highest specific surface area among all the tested materials.
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Document Type: Research Article
Publication date: 01 October 2015
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