Formation of Al2O3-SiC powder from andalusite and carbon

Al2O3-SiC powder has been formed by carbothermal reduction of andalusite, a n aluminosilicate mineral (Al2O3 . SiO2). The andalusite precursor was mixe d to carbon black in a molar ratio (C/SiO2)= 5.5. Phase evolution was studi ed in the temperature range 1260-1550 degrees C. SiC grows in-situ mainly i n the form of whiskers. Some whiskers have globules at their tip, indicatin g that impurities present in the mineral precursor are involved in the vapo ur-liquid-solid (VLS) whisker growth mechanism. Pure oxides mixed with carb on black and doped with known concentrations of metallic impurities were he at treated and the transformations occurring in these systems were compared with those of andalusite-carbon system. The present work is aimed at study ing the reaction conditions for obtaining a powder with favourable characte ristics to elaborate Al2O3-SiC-whisker composites by using raw materials of large availability and a simple in-situ synthesis method. (C) 2000 Publish ed by Elsevier Science S.A.