New data on the thermal analysis of diphasic mullite gel

Abstract

A diphasie mullite gel has been synthesized by using Ludox and AI(NO3)y9H~O in ammoniaeal solution. Both DTA and DDTA studies have been performed with a sensitive differential thermal analyzer system. Besides usual cxotherm due to mullite formation, a pronounced exotherm between 800-1300~ has been noted. Considering previous XRD data, it is explained as due to formation of Si-Al spinel phase, which is subsequently transformed cxothermally at ~1320~ to mullite.

Mullite Phase

“…(vi) Corundum formation is absolutely ceases, i.e., its thermal stability vanishes out when silica and alumina components in the ratio (Al/Si = 3/1) are gelified as per the procedures of synthesis through diphasic and lastly by monophasic route. Phase transformations of diphasic according to Chakraborty (1996a) shows two exothermic peaks (Fig. 21.13) due to crystallization of mullite from mullite(A) and Al-Si Spinel, respectively.…”