Study On Preparation Of High Purity Magnesium Aluminum Spinel Powders

Magnesium aluminate spinel is widely used in medicine and military fields for its high melting point and good mechanical properties. It is a potential material of transparent polycrystalline ceramics for the propagation of light in it is isotropic. Magnesium aluminate spinel prepared by traditional solid phase method is always with poor purity, which influence its application in the field of high-tech.High purity magnesium aluminum spinel powders were prepared by sol-gel in this study, by controlling the parameters in precursor preparation, including water content, types and volume of dispersant and addition of mineralizer, as well as the join order of mineralizer in hydrolysis process, to reduce the particle size of powder. Adjust the volume of mineralizer and cooling rate in roasting process then observe the morphology changes. Magnesium aluminate spinel with the alumina-rich was studied at the last. After characterized By XRD, SEM and particle size analysis, the following conclusions are finally got.The best ratio of water added in hydrolysis process is1:10which can get a minimum particle size. The particle size increases with water content increasing. When the ratio of water is1:26.5, the particle size of powder is relatively small, and hydrolysis is more fully, so1:26.5of water was added to study the effect of dispersant. PAM、PVA and Hacac were added as dispersant. Analyzed by SEM the dispersion effect of PAM and PVA is better then Hacac and none dispersant, and there has been regular morphology appeared. Different amount of PAM have little affect on particle size. With5%mineralizer added, the powder convert into spinel phase with octahedron morphology at1000℃, while powder without mineralizer have no obvious sintering phenomenon at1000℃. Nearly pure phase magnesium aluminate spinel with the alumina-rich can be prepared by both solid phase method and alkoxide method. Different ways of mineralizer added can influence the dispersion of powder. Powder with mineralizer added in hydrolysis process performs better uniform and dispersal than added in grinding process. The sample with4%mineralizer added shows better morphology after sintered. Then sample with4%mineralizer added was hold at different temperature in cooling process. Magnesium alumina spinel nucleate at1100℃and grow up at900℃. Magnesium aluminate spinel grows according to the mechanism of anion coordination polyhedron structure. By comparing the stable energy of different growth units we learned that octahedron is the most stable one.