A New Route to High Yield Mesostructure Boron Carbide Powder from SiC/Si3N4 Whiskers

Boric acid/Mg (magnesiothermic or metal sintering aid)/C (activated carbon)/N₂ or Ar (atmosphere)/additives (mesoporous SiO₂ or mesoporous SiC or SiC/Si₃N₄ whiskers) systems were used in the one‐step synthesis of mesostructured B₄C (221.04 m²/g). In this study, a mixture of the active precursors was allowed to react via a self‐sustaining reaction (high‐energy ball milling process). Also, the properties of the samples prepared using powdered activated carbon (PAC) and SiC/Si₃N₄ whiskers (concentration in the range 5–10 wt%) as sources of carbon were investigated. X‐ray diffraction results proved the presence of crystalline boron carbide in the peak positions of B₄C (B₁₂C₃). The advantage of the present route for yielding mesostructured B₄C powder seems to be limited by the growth of carbide crystals. This restriction is believed to be imposed by a lack of whisker additives around the pores where B₄C crystals grow. The results also show that the best mesoporous additive for the synthesis of nanoscale boron carbide is mesoporous SiC. The effect of the concentration of CO (reduction of α‐Fe₂O₃ to Fe by CO) on the B₄C synthesis suggests that, in addition to the concentration of CO, the pressure of the N₂ atmosphere is an important factor in the synthesis of mesostructured B₄C.