Mullitisation behaviour of calcined clay-alumina mixtures

Sintering of kaolinite in the presence of certain carbonate mineralizers, viz., CaCO 3 , Na 2 CO 3 , and K 2 CO 3 , has been conducted at 950°-1350°C. The influence of these mineralizers at the above temperatures is evaluated using XRD and SEM techniques. A comparative study of phase formation of the above compositions shows that the sodium- and calcium-fluxed samples give rise to multiphase systems, while K 2 CO 3 -incorporated samples give phase-pure mullite. The observation that kaolinite in the presence of K 2 CO 3 can act as a precursor material for phase-pure mullite is of great industrial significance.

Phase‐Pure Mullite from Kaolinite

A Mineralogy-Based Anthropogenic Combustion-Iron Emission Inventory

The manufacture of high performance grinding wheels is heavily dependent upon the selecting the correct abrasive grain in terms of cutting ability, fracturing ability and the shape of the grain that controls metal removal rate, dressing interval, coolant delivery to the wheel-workpiece interface and chip evacuation. This chapter explains the recent developments in abrasive grains and bonding systems and should allow the reader to better select the correct abrasive grain and bonding system to economically machine materials.

Abrasive Tools and Bonding Systems

Effect of Bi2O3 on phase formation and microstructure evolution of mullite ceramics from mechanochemically activated oxide mixtures

The transformation of kaolinite to mullite is reviewed. The thermal effects observed during the transformation and the phases which accompany these effects are discussed in the light of the existing concepts. The chemical, thermal, X-ray, electron-optical, infrared, orientational and crystallographic evidences are advanced to reveal the nature of the intermediate phases and to establish the course of the transformation reaction. Strong evidences exist in favour of Al-Si spinel and γ-Al2O3 as the precursor of mullite formation. The formation of γ-Al2O3 phase finds support in the recent ir, r.e.d. and X-ray fluorescence studies whereas the formation of Al-Si spinel phase is necessary to maintain the structural continuity of the phases from kaolinite to mullite as shown by the single crystal X-ray studies. The transformation follows the sequence:

S. P. Chaudhuri

Papers

A Review on the Kaolinite-Mullite Transformation