EFFECT OF NH₄Cl ADDITIVES ON THE PHASE TRANSFORMATION AND MORPHOLOGY OF α-Al₂O₃

Abstract

To investigate the effects of NH₄Cl doping and the calcination temperature on the phase transformation and microscopic morphology of Al₂O₃, Al₂O₃ powders were obtained by introducing different mass fractions of NH₄Cl into the Al(OH)₃ powders and were then calcined at different tem-peratures. X-ray diffractometry and scanning electron microscopy were used for the phase analysis and particle morphology observation, respectively. The results showed that the addition of NH₄Cl could reduce the phase transition temperature of α-Al₂O₃. With an increase in the NH₄Cl addition, the α-Al₂O₃ phase transition temperature significantly decreased. The transition phase was completely converted to α-Al₂O₃ at 1100°C with the addition of NH₄Cl at 20% at 1100 °C, which reduced both the phase tran-sition temperature and the complete phase transition temperature of α-Al₂O₃ by 100 °C. Meanwhile, the introduction of NH₄Cl had no effect on the microscopic morphology of α-Al₂O₃. The α-Al₂O₃ phases were worm-like with or without NH₄Cl, and the doping of NH₄Cl did not lead to the transitional growth of the complete phase-changed α-Al₂O₃ grains.

Keywords

• α-al₂o₃
• nh₄cl additive
• phase transition
• micromor-phology