NONISOTHERMAL KINETIC-EQUATIONS APPLIED TO CRYSTALLIZATION OF GLASSES

Three of the most important equations for evaluating the activation en ergy of a chemical reaction are discussed in the present paper: a modi fication of the Kissinger equation, a graphic method and a derivative method. They are based on thermal analysis measurements under non-isot hermal conditions. These mathematical approaches were applied to the: study of the crystallization of quaternary glassy systems RO-MgO-Al2O3 -SiO2 (where R is Ca, Sr, Pa, Zn), which separate from two to four cry stalline phases. The nucleation mechanism was also determined by equat ions applied to DTA curves. Although the activation energy values obta ined are similar to those given in the literature,