Low‐temperature synthesis of α‐Al2O3 powder aided by ball milling and a trace amount of sodium chloride

Abstract It is crucial to synthesize α‐Al 2 O 3 , which is a multifunctional material, at high temperatures due to the nature of the material. However, this high‐temperature preparation process is not energy efficient, which goes against the global aim of carbon neutrality. In this study, we explored the effect of adding 1 wt.% (NaCl) as an additive and a suitable amount of Al(OH) 3 in a ball mill to form a precursor. The impact of NaCl and ball milling duration on the phase transition from Al(OH) 3 to α‐Al 2 O 3 at low temperatures was investigated. After the conversion from Al(OH) 3 to γ‐Al 2 O 3 , the NaCl particles on the surface of γ‐Al 2 O 3 act as diffusion channels, helping to accelerate the substance diffusion during the transition from γ‐Al 2 O 3 to α‐Al 2 O 3 , resulting in a lower formation temperature of α‐Al 2 O 3 , which is 700°C. Additionally, the presence of NaCl results in α‐Al 2 O 3 particles growing into hexagonal plates. The α‐Al 2 O 3 plates produced from calcining the mixture of Al(OH) 3 and NaCl at 700°C have an average diameter of 3 µm, an average diameter/thickness ratio of 10 and a specific surface area of 12.0085 m 2 /g. These results indicate that low‐temperature synthesis of α‐Al 2 O 3 powder is possible by using NaCl as an additive instead of molten salt in the ball milling process.