Preparation And Characterization Of Ultra-fine MgAl₂O₄Spinel Power

Due to having many desirable properties, MgAl2O4spinel is used in traditionaldomains of ladle lining and transition and buring zones of cement rotary kilns, and it isalso used in high technology as electronic materials, catalysts, and catalystcarriers,etal.So, much attention has been paid on the synthesis of MgAl2O4spinel. Inthis paper, based on the industrial sodium aluminate and hydrated magnesium chlorideas raw materials, studied the effect of four different feeding methods on the synthesisof magnesium aluminate spinel. The results show that:(1) With the increase of reaction time, chemical composition of the precursorpowder, the content of Al2O3was increased. Four ways of feeding had no obviousdifference.(2) The precursor powders were obtained by four different types of feedingmethods, those phases were Mg4Al2(OH)14·3H2O and Al(OH)3. Four ways of feedinghad no obvious difference.(3) The precursor powders were obtained by four different types of feedingmethods, its particle sizes were significantly different.(4) The precursor powders were obtained by four different types of feedingmethods,they were calcined at different temperature.At500℃, the original peaks ofMg4Al2(OH)14·3H2O and Al(OH)3. disappeared and the crystallites of magnesiaalumina spinel were created of all. As the temperatures continue to rise, the diffractionpeak of spinel gradually increased. At1100℃，the reaction essentially completed, inaddition to the feeding method of hydrated magnesium chloride in powder formjoining in the sodium aluminate solution,because at the temperature of1100℃,it alsohad the phases of Al2O3and MgO.(5) The microstructures of precursor powders and products of roasting were allaggregates of irregular shape. (6) The recovery rate had relationship with the raw material ratio and reactiontime. When the raw material ratio was m(Al2O3):m(MgO)=90:10, stirring time isvaried from30min to24h, the recovery rate is from41.8%to64.72%, even the stirringtime had reached at24h, the recovery rate is still low. And when the raw material ratiowas n(Al2O3):n(MgO)=1:1, stirring time is varied from30min to24h, the recovery rateis from80.86%to89.75%. With the ratio of raw material, increasing the magnesiumchloride can raise the recovery rate,because it can consume more sodium aluminate. Asthe reaction time prolonged, the decomposition rate of sodium aluminate increased,making the recovery rate raised.(7) The product after heating treatment, with ethanol as medium, milling differenttime, the average size of products decreasesd with the milling time increasinggradually.