Isothermal nanocrystallization kinetics during polymorphic transformation |
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Authors: | I Sinha RK Mandal |
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Institution: | a Department of Applied Chemistry, Institute of Technology, Banaras Hindu University, Varanasi, Uttar Pradesh 221 005, India b Centre of Advanced Study, Department of Metallurgical Engineering, Institute of Technology, Banaras Hindu University, Varanasi, Uttar Pradesh 221 005, India |
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Abstract: | The experimental value of Avrami exponent during polymorphic nanocrystallization deviates from the theoretical prediction of the Kolmogorov-Johnson-Mehl-Avrami (KJMA) isothermal kinetics. The assumption of negligible nuclei volume, implicit in KJMA, is violated for all such transformations involving nano-sized grains. A discrete adaptation of the KJMA model is used to study the effect of the non-zero nuclei volume on nanocrystallization kinetics. Transformations initiated by homogeneous and heterogeneous nucleation are analyzed under constant nucleation and growth rate conditions. For homogeneous nucleation, a universal scaling relation with respect to finite nuclei size is found. In contrast to this, for the heterogeneous case a series of linear scaling relations are observed with respect to the nucleation conditions. |
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Keywords: | 64 70 K&minus 81 30 Fb 81 30 Hd |
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