Effect of milling on the oxidation kinetics of Aluminium + Boron mixture and nanocrystalline Aluminium Boride (AlB12)

Highlights: • Oxidation of B was significantly improved by the addition of Al and the conversion (α) increased from 0.67 to 0.82. • Addition of Al to B removed the B₂O₃ layer by forming Al borate and enhanced the oxidation of B. • AlB₁₂ showed a maximum conversion of 0.94 at 1473 K which was a significant improvement when compared to B. -- Abstract: The present work deals with the oxidation behaviour of mechanically alloyed (MA) mixture of Al + B (Al-17.3 wt.% and B-82.7 wt.%) and aluminium boride (AlB₁₂) in the air using thermogravimetric-differential thermal analysis (TG-DTA). An extent of oxidation (conversion, α) of 0.67 was observed for B, and the addition of aluminium to boron increased the conversion to 0.82 and MA of the Al + B mixture for 6 h has led to a further increase in conversion to 0.88. The onset temperature of oxidation and final conversion level showed significant variations between unmilled mixture of Al + B, after MA for 6 h and nanocrystalline AlB₁₂ when heated in air at a constant heating rate of 10 K min⁻¹ till 1473 K. Vyazovkin's method was adopted to evaluate the kinetic parameters and the apparent activation energy was determined for B, Al + B (0 h–6 h MA) and nanocrystalline AlB₁₂. A higher conversion value (α = 0.94) and low average activation energy (96 ± 2 kJ mol^-1) was obtained for nanocrystalline AlB₁₂.