Effects of co-reduction of Cr2O3 and V2O5 on combustion synthesis of (Cr1−xVx)2AlC/Al2O3 solid solution composites

Solid solution composites of (Cr,V)2AlC/Al2O3 with different substitutional proportions were fabricated by self-sustaining combustion involving aluminothermic reduction of oxide precursors. Two reaction systems with powder combinations of Cr2O3-V2O5-Al-Al4C3 and Cr-V2O5-Al-Al4C3 were studied. The degree of atom replacement on the (Cr,V)2AlC phase ranging from 10 to 70 at.% of vanadium in the substitution site was explored. Experimental evidence showed that reaction exothermicity was enhanced by increasing V2O5 and Al. Combustion of the samples involving co-reduction of Cr2O3 and V2O5 was achievable over the full span of stoichiometries and Al2O3-added (Cr1−xVx)2AlC composites with x = 0.1-0.7 were produced. However, the combustibility, flame propagation rate, and product composition of Cr-containing samples were greatly affected by the contents of V2O5 and Al. As a result, the MAX solid solution phase was formed only at the stoichiometry of (Cr1−yVy)2AlC with y = 0.4. For Cr-containing samples of y ⩽ 0.3, combustion failed to be initiated because of low exothermicity. Additionally, the high combustion velocity causing lack of sufficient reaction time was responsible for no yield of (Cr1−yVy)2AlC with y ⩾ 0.5.