Non-isothermal crystallization kinetics of mineral wool fibers

The crystallization behavior of mineral wool was investigated by means of differential thermal analysis(DTA) and X-ray diffraction(XRD).DTA curves reveal the presence of two overlap exothermic peaks and XRD results shows that two crystalline phases are separated out:one is akermanite-gehlenite(AlCa₂Mg_0.5O₇Si_1.5),which was crystallized between 850℃ and 920℃;the other is anorthite(CaAl₂Si₂O₈),which was crystallized between 880℃ and 1010℃.The Ozawa method and the modified Kissinger method were used to analyze the crystallization mechanism and the activation energy of crystallization.For the crystalline of akermanite-gehlenite,the activation energy of crystallization and the Avrami exponent are 248kJ·mol^-1 and 0.682 respectively,indicating surface crystallization;whereas for anorthite,the activation energy of crystallization is 347kJ·mol^-1,revealing three-dimensionality of crystal growth according to the results of scanning electron microscopy(SEM).