Investigation of Sintering Temperature on Attrition Resistance of Highly Porous Diatomite Based Material

Highly porous diatomite based granulates with a diameter of 500 mu m have been produced by an extrusion method. In order to investigate the relation between microstructure, phase composition and attrition resistance of the final product, the granulates were sintered between 800 and 1300 degree C. Mean pore size of the granulates was evaluated by Hg-porosimetry. An increase of the pore size is observed in the range of 3.6 nm to 40 um with increasing sintering temperature. Higher mean pore radii of 1.6 mu m and 5.7 um obtained by sintering at 800 and 1300 degree Crespectively. X-ray diffraction shows that mullite phase appears at 1100 degree C due to the presence of clay. At 1100 degree C diatomite (amorphous silicate) started to transform into a-cristobalite. Attrition resistance was determined by evaluating the amount of ground material passed through a sieve with a predefined mesh size. It was observed that a material sintered at high temperature leads to an increase of attrition resistance due to the decrease of total porosities and phase transformation. Due to the reason that attrition resistance significantly increased by sintering the granulates at higher temperature, a so called attrition resistance index was determined in order to compare all the different attrition resistance values. This attrition resistance index was determined by using the exponential component of the equation obtained from attrition resistance curves. It permits comparison of the attrition behaviour without a time influence.