Inelastic neutron scattering analysis of the thermal decomposition of kaolinite to metakaolin

•Kaolinite dehydroxylation studied using inelastic neutron scattering analysis.•Integrated intensities in 200-1200 cm−1 range used for semi-quantitative analysis.•Preferential loss of inner surface hydrogen atoms during reaction.•INS is an ideal tool for studying different hydrogen environments in clays.

Understanding the formation of metakaolin via kaolinite dehydroxylation is extremely important for the optimization of various industrial processes. Recent investigations have reported that the different types of hydrogen atoms in kaolinite are removed concurrently during the dehydroxylation process. Here, inelastic neutron scattering (INS) is used to analyze the location and dynamics of hydrogen atoms in kaolinite, together with the changes induced during dehydroxylation. This is achieved by using prior knowledge of how the inner and inner surface hydrogen atoms contribute to the kaolinite INS spectrum in the 200-1200 cm−1 range, in combination with a semi-quantitative analysis of the experimental INS spectra. Overall, it is seen that there is a distinct preferential loss of inner surface hydrogen-atom types during the dehydroxylation process, as determined from analysis of the Al-O-H vibrational modes (consisting of deformation and torsion) in the INS spectrum.

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