Synthesis of boron suboxide (B_6O) with ball milled boron oxide (B_2O_3) under lower pressure and temperature

摘要

Boron reacted with ball milled boron oxide under pressures between 1 and 5 GPa and at temperatures between 1300 and 1700 °C to afford boron suboxide (B_6O). Icosahedral B_6O grains with diameters ranging from 100 nm to 1.3 μm were prepared. The factors that affect the synthesis of B_6O are investigated. The best sample with crystal size up to 1.3 μm is obtained at 2 GPa and 1400 °C for 6 h. The indentation experiment gave an average Vickers hardness of 32.3 GPa for bulk B_6O sample, which is consistent with previous reports. Bulk B_6O sample exhibits oxidation resistance in air up to 1000 °C and mild oxidation in the temperatures of 1000-1200 °C, which is more oxidation resistant than diamond. It is possible that B_6O could be used as a substitute for diamond in industry because of its relatively mild synthesis conditions, high thermal stability and high hardness.