DECREASE OF THE MGAL2O4 FORMATION TEMPERATURE

Mixtures of Al2O3 and (MgCO3)(4) . Mg(OH)(2) . 5H(2)O, mechanically ac tivated by intense grinding in a laboratory vibrating mill for up to 1 20 min, were additionally heat treated from 800 to 1250 degrees C, It was shown that more intense particle size reduction of the crystallite s of basic MgCO3 from 39 to 13 nm took place during activation, while the Al2O3 crystallites became finer from 32 to 23 nm. The BET specific surface area of ground spinel mixtures increases up to 30 min of acti vation and decreases thereafter. With prolonged activation time the te mperature of reaction termination drops after the same isothermal heat ing time. The beneficial effect of the mechanical activation of spinel mixtures on the development of the chemical reaction is due to both t he particle size reduction of the reactants and the partial decomposit ion of basic MgCO3. The positive influence of intense grinding on the reaction product yield is more pronounced at lower temperatures.