In situ neutron diffraction investigation on the phase transformation sequence of kaolinite and halloysite to mullite

Tezuka, N; Low, IM; Davies, IJ; Prior, MJ; Studer, AJ

In situ neutron diffraction investigation on the phase transformation sequence of kaolinite and halloysite to mullite

Date

2006-11-15

Authors

Publisher

Elsevier B. V.

Abstract

“Kaolin” is a major raw material for the fabrication of conventional ceramics. In this work the authors have investigated the thermal phase transformation of mullite from two different types of kaolin (kaolinite and halloysite), with or without alumina matrix constraint, during heating up to 1500 °C and then cooling using in situ neutron diffraction. Mullitization was initiated upon heating to 1200 °C for all specimens and followed spinel formation at 1100 °C. Above this temperature, however, evolution of the main phases, i.e., mullite, cristobalite and corundum, was influenced by the presence of impurities, initial type of silica, and alumina constraint. The relative amount of mullite was largest for the pure kaolinite specimen, particularly during heating, and this was attributed to the presence of a glassy phase. However, kaolinite with alumina suppressed the crystallization of cristobalite from the glassy phase upon cooling due to a reaction between alumina and amorphous silica, consequently resulting in an amount of mullite as for the pure kaolinite specimen (approximately 65 wt%). Halloysite was less active in terms of mullitization due to the lower level of initial impurities and greater amount of cristobalite, particularly for the alumina-constrained specimen. However, the final amount of mullite derived from the pure halloysite specimen was similar to that as from the kaolinite specimen. Crown Copyright © 2006 Published by Elsevier B.V.

Description

Physical copy held by ANSTO Library at DDC 539.7213/3. Part I

Keywords

Mullite, Neutron diffraction, Kaolinite, Clays, Ceramics, Phase transformations, Temperature range 1000-4000 K, Cooling, Heating, Crystallization, Aluminates, Cristobalite

Citation

Tezuka, N., Low, I.-M., Davies, I. J., Prior, M., & Studer, A. (2006). In situ neutron diffraction investigation on the phase transformation sequence of kaolinite and halloysite to mullite. Paper presented at the Eighth International Conference on Neutron Scattering (ICNS 2005), "Neutrons for structure and dynamics - a new era", Sydney, Australia, 27 November to 2 December 2005. In Campbell, S. J., Cadogan, J. M., Furusaka, M., Hauser, N., & James, M. (Eds), Physica B: Condensed Matter, 385-386(Part 1), 555-557. doi:10.1016/j.physb.2006.05.357