Transactions of the INDIAN CERAMIC SOCIETY Vol. 57 1998
Effect of Heat on Al20 3-Si02 Gel
Co-precipitated at Different pH
M. H. DAFADAR, S. DAS AND A. K. CHAKRAVORTY
Pages : 100-102
DOI : 10.1080/0371750X.1998.10804843
Abstract
In the present studies Al20 3-Si02 mullite gels have been
synthesized in close range of pH between 6 and 9 by coprecipitating
technique using dilute NH40H solution. Both
qualitative and semi-quantitative mullite formation studies
have been done. Results show that a spinel to mi.dlite formation
occurs during heating the co-precipitated gels in the
temperature range between 1100° and 1200°C with 2 hours
soaking in each case. The quantity of mullite in all the cases
increases with the continued increase in temperature. With the
increase in pH, during co-precipitation, the approximate yield
of mullite decreases from pH 6 to 9. It is concluded that coprecipitated
Al20rSi02 gel becomes inhomogeneous with
increase in pH during precipitation. The appearance of
boehmite at higher pH range is responsible for low
mullitization growth during heat treatment.
