Effects of wet vibro-milling on the polymorphic conversion of aragonite into calcite

Abstract

Pure synthetic aragonite and calcite, the latter obtained by heating the former, were vibro-milled in cyclohexane. Aragonite was partially converted into calcite on wet vibro-milling, whereas calcite was not transformed into aragonite. The rate of conversion of aragonite into calcite on heating at 420 °C in air was markedly increased by preliminary vibro-milling. In contrast to the situation for γ-Fe₂O₃, the increase in the rate of transformation on vibro-milling is mainly attributed to the increase in the number of nucleation sites.