Kinetic studies on leucite precursors

摘要

Kinetic studies were performed on two types of leucite precursors. These precursors were prepared using a hydrothermal method at 150℃; the reaction time was 1.5 hours. In order to obtain precursors having different amounts of seed the molarity of KOH was changed. These intermediate products were subsequently calcinated from 5 minutes to 72 hours at temperatures of 850℃, 900℃, 950℃, 1000℃ and 1050℃. The crystallinities of the powders were calculated by X-ray diffraction analysis. The crystallization curves for the synthesis of leucite exhibited a typical sigmoidal characteristic. Using different kinetic equations it was found that the Avrami-Erofeev model is the most appropriate to describe the experimental data. Using the Avrami-Erofeev model n reaches an average value of 2.9 which is connected with the three-dimensional growth of nuclei. The calculated activation energy of crystallization of leucite was 385 kJ mol~(-1) for non-seeded precursors and 246 kJ mol~(-1) for seeded precursors, respectively.