Effect of the mechanical activation on the thermal decomposition of kyanite
Abstract
The effect of the mechanical activation of kyanite powders (Al2O3•SiO2) on the thermal transformation into mullite (3Al2O3•2SiO2) and free silica (SiO2, in form of cristobalite) was studied. The kyanite powders were ground for 6 h and characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The powders were cold uniaxially compacted in cylindrical samples (compacts) and sintered in a temperature range of 1150-1500 °C. These compacts are characterized by XRD, SEM, thermodilatometry analysis (TD) and differential thermal analysis (DTA). The resulting microstructure consists of equiaxial mullite grains immersed in a glassy phase. It was observed that kyanite milled begins to transform into mullite plus silica at 1150ºC. From 1300 °C only the mullite peaks and cristobalite are observed. The objective is to verify that mechanical activation activates nucleation sites where the mullite begins to form, decreasing the decomposition temperature of kyanite.
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References
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