Production of Si3N4 by carbothermal reduction and nitridation of sepiolite

A study was undertaken to determine the optimum parameters for production of Si3N4 powders by carbothermal reduction and nitridation (CTRN) of Turkish sepiolite. Test samples were prepared by mixing 99% purity -325 mesh carbon black and -100 mesh leached brown sepiolite with C/SiO2 molar ratios of 1.5; 3; 4; 5, and 7.5. Prepared samples were subjected to the CTRN process at temperatures of 1200, 1300, 1400 and 1450 degrees C for 2, 4, 8, and 16 h. The CTRN process was conducted in an atmosphere controlled tube furnace in a nitrogen flow of 4.5 cm(3)/min. All products were examined by XRD and SEM-EDX to determine the transformation, morphology and chemical composition. The results showed that the best Si3N4 transformation occurred at 1400 degrees C for 16 h with C/SiO2 molar ratio of 4. (C) 1999 Kluwer Academic Publishers.