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.