THE INFLUENCE OF THE TEMPERATURE INCREASE RATE ON THE ACCURACY OF DIFFUSION PARAMETERS ESTIMATED UNDER NONISOTHERMAL CONDITIONS

The accuracy of the diffusion parameters estimated under non-isotherma l conditions was studied using computer-generated pseudo-experimental points. The data sets were obtained from Fick's 2nd law and an Arrheni us-type temperature dependence of the diffusivity. A normally distribu ted error was randomly attributed to the model data. The pseudo-experi mental points thus obtained were then fitted to the model equation, wi th non-linear regression using the Simplex algorithm, yielding the est imates of the pre-exponential factor and activation energy. Several li near temperature profiles were studied, from 0.014 to 16 degrees C min (-1). It was concluded that the accuracy of the parameters estimation depends on the temperature increase rate. The effects of the pre-expon ential factor, the activation energy, the range of temperature and the magnitude of the experimental error on the value of the temperature i ncrease rate that led to maximum accuracy of the parameters estimates were also studied.