Micro structural and densification study of natural Indian magnesite in presence of zirconia additive

摘要

The sintering and microstructural evaluation of Indian magnesite was carried out in presence of zirconia. Zirconia in monoclinic form was added in the range 3-6 wt% with respect to raw magnesite and the sintering temperature selected were 1500-1600°C for 2 h. The main impurities present in the magnesite were Fe_2O_3, CaO, SiO_2. The natural crystalline magnesite could be sintered with bulk density of 3.38 g/cc (A.P. 1.54%) at 1550°C/2 h. But the higher bulk density (3.50 g/cc) and minimum apparent porosity (A.P. 0.25%) was attained at 1550°C/2 h with the 3 wt% zirconia additive. On firing magnesite with zirconia as additive, a crystalline phase, magnesio-zirconate, was identified at the triple point regions of the direct bonded periclase grains. The morphology of the periclase grains were changed from subrounded/rounded to angular shaped in presence of zirconia as additive.