Studies Of Water Films and Carbonation Via Neutron Scattering and Infrared Adsorption: In Situ Studies of Mg(OH)2 and Ca(OH)2

Published

March 24, 2026

Author(s)

Hubert King, Ryan Murphy, Avery Baumann, Robert Dalgliesh, Dirk Honecker, Gregory Smith

Abstract

Small-angle neutron scattering was used to investigate structural evolution during the carbonation of Ca(OH)₂ and Mg(OH)₂ under humidified CO₂, using both H₂O and D₂O vapor. For Ca(OH)₂, carbonation led to a progressive increase in both nano- and meso-scale surface areas and a doubling of meso-scale diameter, indicating the development of a more complex, porous structure. In contrast, Mg(OH)₂ exhibited a reduction in meso-scale surface area and loss of fractal features, consistent with the formation of smoother, denser carbonate phases. When exposed to D₂O, Mg(OH)₂ formed increasingly smooth surfaces and developed D₂O films that grew with time and approached a saturation thickness of ≈1.9 nm. These results highlight distinct carbonation pathways: Ca(OH)₂ evolves toward greater structural complexity, while Mg(OH)₂ forms compact, hydrated carbonate layers, with D₂O enhancing water film stability and surface transformation. Unexpectedly, both SANS data and polarization modulation infrared reflection absorption spectroscopy (PM-IRRAS) show that Mg(OH)₂ exhibits clear evidence of H–D exchange, confirming that surface hydroxyl groups are labile and accessible for interaction with D₂O.

Citation

Journal of Physical Chemistry

Pub Type

Journals

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Keywords

water D2O and H2O, carbonation, alkaline earth hydroxides

Citation

King, H. , Murphy, R. , Baumann, A. , Dalgliesh, R. , Honecker, D. and Smith, G. (2026), Studies Of Water Films and Carbonation Via Neutron Scattering and Infrared Adsorption: In Situ Studies of Mg(OH)2 and Ca(OH)2, Journal of Physical Chemistry, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=960663 (Accessed March 25, 2026)