Combined use of high resolution TGA with the isoconversion method: Kinetic analysis of the thermal dehydration of KNbWO6·H2O |
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Authors: | G. Rodrí guez-Gattorno,E. Torres-Garcí a |
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Affiliation: | a Instituto Mexicano del Petróleo, Eje Lázaro Cárdenas 152, San Bartolo Atepehuacan, 07730 México D.F., Mexico b Instiuto de Investigaciones en Materiales, UNAM, AP 70-360, México D.F., Mexico |
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Abstract: | In the present study was combined the use of high resolution TGA with the isoconversion method, giving us a suitable methodology for determining the stages that occur during a reaction, and providing further insights about the kinetics of the processes involved. As a model reaction was used the thermal dehydration of KNbWO6·H2O. The results shown that the dehydration process is controlled by internal water diffusion (intra-crystallite); with activation energy values between 43 and 36 kJ/mol. This value is consistent with a diffusion mechanism dominated by van der Waals attractions. The estimated kinetic parameters are supported with a structural analysis, that suggest lower dimensionality character for water diffusion due to the specific orientations of 〈1 1 0〉 open channels in the pyrochlore framework. This would explain why the two-dimensional (D2) mechanism appears to be the most probable. |
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Keywords: | Isoconversion method Dehydration kinetics Hi-Res TGA Kinetics in solids Thermal analysis |
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