SYNTHESIS AND SINTERING OF CORDIERITE FROM ULTRAFINE PARTICLES OF MAGNESIUM-HYDROXIDE AND KAOLINITE

Thermal reactions of magnesium compounds and kaolinite were investigat ed to obtain dense cordierite ceramics without additives. Magnesium hy droxide was precipitated from aqueous solution in the form of ultrafin e hexagonal tabular particles of about 0.1 mu m, and heating this mixt ure with kaolinite in a mole ratio of MgO . Al2O3 . 2SiO(2) resulted i n formation of an amorphous state at about 900 degrees C following the rmal decomposition. mu-Cordierite was then crystallized from the amorp hous phase at about 950 degrees C, and gradually transformed into alph a-cordierite. Firing the pressed specimens yielded a dense alpha-cordi erite ceramic with a relative density of 97.7% at 1350 degrees C.