Estimation of parameters of vapor diffusion during dehydroxylation in a cylindrical ceramic sample

J. Ondruska1, A. Trnik1,2, I. Medved1,2 and L. Vozar1

1Constantine the Philosopher University in Nitra, Slovakia
2Czech Technical University, Czech republic

Keywords: inverse problem, dehydroxilation
property: vapor diffusion
material: ceramics, kaoline

We present a numerical method to estimate the mass diffusion coefficient and mass generation density of a kaolin-based ceramic material. Transient thermal response at several radial positions of a cylindrical sample of diameter 8 cm is measured during an isothermal heating at the temperatures 450 C, 500 C, 550 C, 600 C, and 650 C. In this temperature region dehydroxylation (i.e., the transformation of kaolinite into metakaolinite) occurs, accompanied by the diffusion of water vapor through the sample. We solve the inverse problem by an iterative procedure based on the Levenberg-Marquardt method. The temperature dependence of the obtained values of the diffusion coefficient are fitted by the Arrhenius relation, yielding an estimate of the activation energy of the mass transfer process.

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