Abstract:
Aluminum is a widely used material in the industries of electronics, automobiles, and aviation due to its excellent properties. However, the synthetic temperature of commercial
α-Al
2O
3 powder is high, and the obtained powder has coarse particles, low activity, serious agglomeration, and it is not easy to disperse, which affects its subsequent applications. Therefore, the synthesis of
α-Al
2O
3 powder at a low temperature is challenging. In this paper,
α-Al
2O
3 powder was synthesized by calcining NH
4Al(SO
4)
2·12H
2O with different added glucose contents. The effects of glucose content and sample pre-pressing on the synthetic temperature of
α-Al
2O
3 powder were investigated. The results showed that the presence of glucose changed the phase transition process and significantly decreased the synthetic temperature. With 30% (mass fraction) glucose added,
α-Al
2O
3 powder could be synthesized at 950 ℃, which was about 200 ℃ lower than that of the glucose-free control. With 75% glucose added, the synthetic temperature of
α-Al
2O
3 further decreased to 900 ℃. The presence of glucose is believed to accelerate the thermal decomposition of NH
4Al(SO
4)
2·12H
2O, and make NH
4Al(SO
4)
2·12H
2O be dispersed evenly and amorphous. The results also showed that pre-pressing further decreased the synthetic temperature of
α-Al
2O
3 by 25—50 ℃, which might be a result of the attenuation of agglomeration and the further homogenization of powder dispersion. Moreover, single-phase
α-Al
2O
3 with a uniform distribution of particle size (average particle size 110 nm) were obtained at 850 °C by using 25 MPa pre-pressing and 75% (mass fraction) glucose process.