Low-Temperature Molten Salt Synthesis and the Characterisation of Submicron-Sized Al₈B₄C₇ Powder

Submicron-sized (~200 nm) aluminium boron carbide (Al₈B₄C₇) particles were synthesised from Al, B₄C and carbon black raw materials in a molten NaCl-based salt at a relatively low temperature. The effects of the salt type/assembly and the firing temperature on the synthesis process were examined, and the relevant reaction mechanisms discussed. The molten salt played an important role in the Al₈B₄C₇ formation process. By using a combined salt of 95%NaCl + 5%NaF, an effective liquid reaction medium was formed, greatly facilitating the Al₈B₄C₇ formation. As a result, essentially phase-pure Al₈B₄C₇ was obtained after 6 h of firing at 1250 °C. This temperature was 350-550 °C lower than that required by the conventional direct reaction and thermal reduction methods.