Temperature Dependence of Structure and Density for D2O Confined in MCM-41-S

Published

February 15, 2012

Author(s)

William A. Kamitakahara, Antonio Faraone, Kao-Hsiang Liu, Chung-Yuan Mou

Abstract

Using neutron diffraction, we have tracked the temperature dependence of structural properties for heavy water confined in the nanoporous silica matrix MCM-41-S. By observing the correlation peak corresponding to the pore-pore distance, which is determined by the scattering contrast between the silica and the water, we monitored the density of the confined water. Concurrently, we studied the prominent first diffraction peak of D₂O at ≅1.8 Å-1, which furnishes information on the microscopic arrangement of the water molecules. The data show the presence of a density maximum at ≅275 K (±10 K), a property similar to bulk water, and the occurrence of a density minimum at ≅180 K (±10 K). The prominent diffraction peak of D₂O is found to shift and sharpen over a wide T range from 200 K to 270 K, reflecting structural changes that are strongly correlated with the changes in density. We also observe the continuous formation of external ice, arising from water expelled from the pores while expansion takes place within the pores. An efficient method for monitoring the density of the confined D₂O using a triple-axis spectrometer is demonstrated.

Citation

Journal of Physics Condensed Matter

Volume

24

Pub Type

Journals

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Citation

Kamitakahara, W. , Faraone, A. , Liu, K. and Mou, C. (2012), Temperature Dependence of Structure and Density for D₂O Confined in MCM-41-S, Journal of Physics Condensed Matter, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=908297 (Accessed April 26, 2024)