Sintering of a clay from Burkina Faso by dilatometry Influence of the applied load and the pre-sintering heating rate

The sintering of a pottery clay from Burkina Faso was studied as a function of the heating rate, at 3 or 10 degreesC/min. The experimental method used was loading dilatometry in isothermal conditions at 1120 degreesC. In thes e conditions, we found that the densification rate of the material is low, but tend to a limiting value after 2 h at 1120 degreesC, depending on the p re-sintering heating rate and the load used. The relationship between the p re-sintering heating rate and the densification rate indicated the existenc e of a weakly organised material at higher heating rates. Nevertheless, hig her values of shrinkage were observed when the temperature increased contin uously. It is, therefore, proposed that the material is subject to a prefer ential solid state diffusion mechanism at face to face of the remaining kao linite layers at high temperatures. This mechanism is favoured by higher he ating rates, mainly in the temperature range corresponding to the structura l reorganisation of the metakaolin phase. (C) 2001 Elsevier Science Ltd and Techna S.r.l. All rights reserved.