Influence of Origin and Calcination Treatments on the Physical Properties of Magnesia Powders

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Abstract
An attempt was made to study the influence of origin and calcination treatments on the development of crystallinity, surface area and the morphology of magnesia powders. Magnesia powders were prepared by thermal decomposition/calcination of different parent compounds namely, magnesium hydroxide, oxalate, carbonate, salicylate and succinate. Calcination temperatures upto 900°C in either air or vacuum and soaking time from half to 16 hrs were used. The development of crystallinity in the resultant magnesia powders was studied at room temperatures by X-ray line broadening techniques. The surface areas of the magnesia powders were determined by the BET method. A limited study was made on the morphology of the powders using electron microscope. It was found that at the decomposition temperature of the parent compound, the crystallinity of the resultant magnesium oxide was very poor, and the surface area extremely high. With an increase in calcination temperature, the crystallinity of the oxide powders improved and the surface areas decreased. Prolonged soaking at any calcination temperature, also resulted in a lower surface area; the lowering being more significant at higher temperatures. The influence of the origin on the physical properties namely—crystallinity, surface area and morphology were discernible even after calcination at 700°C for periods upto 16 hrs.