In situ Angstrom-to-Micrometer Characterization of the Structural and Microstructural Changes in Kaolinite on Heating using Ultra-Small-Angle, Small-Angle, and Wide-Angle X-ray Scattering (USAXS/SAXS/WAXS)

Published: September 26, 2017


Fan Zhang, Andrew J. Allen, Greeshma Gadikota


In this study, synchrotron-based in-operando multi-scale X-ray scattering analyses are used to connect the microstructural changes to the phase changes in kaolinite on heating from 30 °C to 1150 °C. Combined ultra-small-angle and small-angle X-ray scattering (USAXS and SAXS) data are modeled to determine the hierarchical morphology of kaolinite comprising nano-scale interlayer pores, meso-scale pores, and larger interparticle voids, while wide-angle X-ray scattering (WAXS) data reveal the simultaneous evolution of atomic structures in kaolinite. We found that the transformation of kaolinite to metakaolin corresponds to the disappearance of nano-scale porosity, and the onset of sintered phases such as mullite is consistent with the overall reduction in the porosity of kaolinite. The emergence of nano-scale particulate features in the reciprocal-vector, q, range of 0.04 Å-1 to 0.4 Å-1 on heating in excess of 900 °C corresponds to the onset of the sintered phases such as spinel and mullite. This study illustrates the application of multi-scale X-ray scattering measurements which encompass USAXS, SAXS and WAXS to connect the thermally induced phase changes with changes in pore structure and fine morphology evolution.
Citation: Industrial & Engineering Chemistry Research
Volume: 56
Issue: 41
Pub Type: Journals

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kaolinite, mall angle X-ray scattering (SAXS), wide angle X-ray scattering (WAXS), microstructure characterization, phase composition
Created September 26, 2017, Updated January 31, 2018