STUDIES ON PLASMA DISSOCIATION OF INDIAN ZIRCON IN A SPECIALLY DEVELOPED PLASMA REACTOR

Abstract

Studies on the preparative and microstructural aspects of plasma-dissociated Indian zircon prepared in a specially designed plasma reactor (20 kW) are reported. The vital parameters involved in the process have been optimized for a high degree of dissociation with maximum feed rate. A near total phase separation (ZrO2 and SiO2) has been achieved in the plasma-dissociated zircon spheroids which constitute over 90% of the product. Microstructural studies have revealed that the spheroids are of two types with a distinct difference in the morphology of zirconia crystallites. Most of the spheroids have been found to have well-developed polygonal grains with spherulitic growth of ZrO2 in SiO2 glass. The rest of the spheroids consist of intergrown tabular crystals of monoclinic zirconia set in a matrix of silica. The silica present in the plasma-dissociated zircon has been amorphous and highly reactive, and is leached out using hot NaOH solution to recover fine grain zirconia.