OBTAINING OF GARNET CERAMIC MATERIALS BY UTILIZATION OF RICE HUSK ASH AS SILICA SOURCE

Abstract

The current research aims at the obtaining of new type pigments from the garnet mineral group by utilization
of rice husk ash as silica source (RHA). At the beginning, the mixtures prepared from the starting raw materials are
ground in a ball mill and then subjected to high temperature treatment. Green pigments were synthesized at two
temperatures: 1000°C and 1100°C. Using the tintometer RT 100 Lovibond the colour characteristics were measured
spectrophotometrically. The rice husk ash was investigated using scanning electron microscopy. The conducted hot-
stage microscopic studies show that the pigments remain thermally stable when heated. The highest fire resistance - up
to temperatures of 1380°C - 1400°C show the uvarovite pigments with main phase 3CaO.Cr₂O₃.3SiO₂ or by a general
formula Ca₃Cr₂[SiO₄ ]₃. They are suitable for inserting into ceramic glazes without danger of decomposition or reaction.
Keywords: ceramic pigments, SEM, colour determination, Hot-stage microscopy.