Synergistic effect of α-Al2O3 and (NH4)3AlF6 co-doped seed on phase transformation, microstructure, and mechanical properties of nanocrystalline alumina abrasive

The effect of the single doped seeds (α-Al2O3, γ-Al2O3 and (NH4)3AlF6) and co-doped seeds (γ-Al2O3 + (NH4)3AlF6 and α-Al2O3 + (NH4)3AlF6) on the phase transformation, microstructure and mechanical properties of alumina abrasive prepared with sol–gel process were investigated. The results showed that fine crystal of α-Al2O3 and (NH4)3AlF6 co-doped seed had potential synergistic effects for reducing the temperature of phase transformation from θ-Al2O3 to α-Al2O3, increasing density of samples and improving the mechanical properties of alumina abrasive particle. With the same doped amounts, the phase transformation of gel with α-Al2O3 + (NH4)3AlF6 co-doped seed took place at lower temperature than with the other seeds, and the sample sintered at 1300 °C reached about 99.5% of theoretical density with the average crystal size of 60 nm, which accounted for its higher single particle compressive strength of 41.2 N, and as well as it is a better abrasive wear-resistance than those of the samples with the others seeds.