MECHANOCHEMICAL DEHYDRATION AND AMORPHIZATION OF HYDROXIDES OF CA, MG AND AL ON GRINDING WITH AND WITHOUT SIO2

Mechanochemical dehydration and amorphization of Ca(OH)2, Mg(OH)2 and Al(OH)3 (gibbsite) were substantially enhanced by grinding with SiO2. The rates of those mechanochemical reactions were in the order of Al(OH)3 > Ca(OH)2 > Mg(OH)2. These phenomena are explained by such a model that the decomposition of hydroxide and the incipient formation of metal silicates are stimulated by each other. Apart from Mg(OH)2 and Ca(OH)2, gibbsite was amorphized and dehydrated easily by grinding without SiO2, as well, because of intrinsic structural vacancy.