New route for preparing nanosized boron carbide powder via magnesiothermic reduction using mesoporous carbon

Abstract A mesoporous carbon/boric acid composite was reacted using the magnesiothermic reduction route in order to synthesize nanosized crystalline boron carbide with a narrow particle-size distribution at a relatively low temperature. In the present study, properties of samples prepared using carbon black (CB) and mesoporous carbon (CMK-8) as sources of carbon with different synthesis temperatures were investigated. Using CMK-8 to prepare boron carbide (B4C(CMK-8)) at 750 °C was found to increase the surface area of the boron carbide product up to 160%. X-ray diffraction results proved the presence of crystalline boron carbide in the peak positions of B4C (B12C3). Scanning electron microscopy revealed the size and shape uniformity of B4C(CMK-8) particles in the range of 40–80 nm in comparison with B4C(CB), which demonstrated a particle-size distribution in the nanometer to micrometer ranges. Transmission electron microscopy validated the formation of well crystallized particles of B4C of around 40 nm with a near rhombohedral shape. The advantage of the present route for yielding nanosized B4C powder seems to depend on carbide crystalline growth limitations. This restriction is believed to be imposed by a lack of carbon and boron oxide around the pores where B4C crystals are growing.