Wetting behavior of metakaolinite on the basal surfaces - Molecular dynamics study

RP Chen and XY Liu and W Yang and Z Xia and X Kang and A Lushnikova, COMPUTERS AND GEOTECHNICS, 129, 103863 (2021).

DOI: 10.1016/j.compgeo.2020.103863

The wetting behavior of aluminum (001) and silicon (0 0 (1) over bar )basal surfaces of metakaolinite was investigated by means of force- field molecular dynamics simulations. The rationality of existing controversial metakaolinite models was verified and the Brindley and Nakahira model was confirmed. Kaolinite has mainly hydrogen bonding between the layers, which is sufficiently strong to prevent cleavage under normal conditions. While under calcination, the dehydroxylation on kaolinite led to the weakening of interlayer attraction from hydrogen bonding to Van der Waals forces, caused the subsequent breakup of particle and the increase of specific surface area. It has been found that the calculated contact angle of metakaolinite aluminum surface was 17 degrees, which is different to zero contact angle of kaolinite aluminum surface. The loss of inner-surface protons and hydroxyl ions resulted in unsaturated coordinated aluminum sheet, which was ready to react with dropping water to form new Al-O-w and hydroxyl bonds. Apparently, these water-clay interactions mechanisms played a major role in the different wettability of metakaolinite. For comparison purpose, contact angles for kaolinite and metakaolinite were measured by experiments, the measured values were and 20 degrees and 41 degrees respectively, the increase of contact angel had the benefit of the decreased hydrophilicity on aluminum surfaces of metakaolinite.

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