ABSTRACT
Besides Okada et al., progressive changes in lattice parameters particularly of mullite in the heating process of mullite gels was also noted by several researchers. Okada and Ousuka of course showed mullite formation over a range of temperature in their pioneering mullitization studies. However, the poorly crystalline alumina rich mullite phase shows broad Si resonance peak at -90 ppm. The growth of mullite continues in the range 1200 C-1400 C. Growth process of SHI, SHII, and SHIV show two paths of mullite formations. The mullite growth process of mullite gel SHI made by the author consists of two portions, one is very rapid, second one is rather slow and gradual. Solid solubility of mullite has been established and estimated by Rooksby and Partridge to be from the 3:2 to the 2:1 ratio. Monophasic gel synthesized by different researchers shows variation of intensity of first exotherm. It’s enthalpy of crystallization shows a great variation in experimental value by different studies.
