Abstract
The paper aims in correlating isothermal DSC signals to the actual nucleation and crystallization processes in a lithium disilicate glass as determined by optical microscopy. The results show that the DSC signal reflects the change from an initial surface nucleation to a site saturation regime (constant number of crystals) leading to a coast-island microstructure in monolithic samples. An isothermal JMAK analysis revealed a maximum of the instantaneous Avrami coefficient at the onset time of saturation (impingement time). Impingement times were used to approximate heterogeneous surface nucleation rates, which were found to be up to 14 orders of magnitude higher than those of homogeneous volume nucleation and correlate positively with temperature in the range 0.64–0.68 Tm.
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