Effect of particle size of tabular talc powders on crystal orientation and sintering of cordierite ceramics

概要

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Cordierite ceramics were prepared from several types of kaolin powders and talc powders having various median particle size with nanometer-sized alumina sol. Powder mixtures were uniaxially pressed, followed by cold isostatic pressing to make thin compacts. Crystal orientation of talc particle and resultant cordierite were evaluated using the X-ray diffraction profile measured on the uniaxially pressed surface of calcined compacts and sintered compacts, respectively. Coarser talc powders above 3 µm aligned their c-axis in vertical to the uniaxially pressed surface of the calcined compact during uniaxially pressing, owing to highly anisotropic tabular shape. The crystal orientation of resultant cordierite increased with an increase in the crystal orientation of talc powders on the pressed surface. This result indicated that the c-axis of cordierite crystal preferably oriented vertically to the c-axis of talc particle oriented. Using the combination of kaolin powders below 5 µm and talc powders having median particle size between 3 and 5 µm, densely sintered cordierite, having a relative density of 95% and high crystal orientation of approximately 85% [I110/(I110+I002)], could be obtained.
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