| Effect of Water Used During Gelation on the Phase
Transformation of Al20 3-Si02 Gel |
M. H. DAFADAR, s. DAS AND A. K. CHAKRA VORTY
Pages : 121-126
DOI : 10.1080/0371750X.1998.10804849 |
| Abstract |
| Two kinds of AI20 3-Si02 gels have been synthesized out of
aluminium nitrate and tetraethyl orthosilicate. First kind of
gel, prepared in excess of hydrolysis agent, e.g. water, does
not exhibit 980°C exotherm due to formation of a spinel
phase at an earlier temperature. Contrary to the first kind,
the second kind of gel prepared in absolute alcohol only and
in the absence of moisture develops considerable quantity of
mullite directly at 980°C with an exotherm in DT A.
Comparative phase transformation sequences by X-ray
technique reveal corundum prior to mullitization in first kind
of gel. This explains the development of diphasic character of
the gel because of the presence of large quantity of water
during gelation process. |
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