• Korean Chemical Engineering Research
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• v.48 no.5
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• pp.627-631
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• 2010

$\alpha$-Alumna particles were prepared by a precipitation method with metal fluoride additive. Aluminum nitrate and ammonia solution were used as starting materials. $AlF_3$, $CaF_2$, and $MnF_2$ were utilized as additives. The effects of precipitation solvent and metal fluoride on the phase transformation temperature, size and morphology of $\alpha$-alumna particles were investigated. The solvent for precipitation did not affect the phase transformation temperature, while it influenced the size of $\alpha$-alumna particles. The phase transformation temperature to $\alpha$-alumna was reduced by addition of metal fluoride and was different with metal cation in metal fluoride ($AlF_3(800^{\circ}C)$ < $MnF_2(900^{\circ}C)$ < $CaF_2(950^{\circ}C)$). The addition of each of three metal fluorides led to the formation of platelike particles and, among the three additives, $MnF_2$ additive resulted in the formation of relatively small particle.