Fizika Nizkikh Temperatur: Volume 46, Number 11 (November 2020), p. 1318-1322    ( to contents , go back )

On thermal stability of cryovacuum deposited CH4+H2O films

A. Aldiyarov, D. Sokolov, A. Akylbayeva, and А. Nurmukan

Institute of Experimental and Theoretical Physics, al-Farabi Kazakh National University Almaty, 050040, Kazakhstan
E-mail: Abdurakhman.Aldiyarov@kaznu.kz

N. Tokmoldin

Satbayev University, Institute of Physics and Technology, Almaty, 050032, Kazakhstan
pos Анотація:

Received June 20, 2020, published online September 21, 2020

Abstract

Whereas stable homogenous states of aqueous hydrocarbon solutions are typically observed at high temperatures and pressures far beyond the critical values corresponding to individual components, the stability of such system may be preserved upon transition into the region of metastable states at low temperatures and low pressures. This work is dedicated to the study of the thermal stability of a water–methane mixture formed by cryogenic vapor phase deposition. The obtained thin films were studied using vibrational spectroscopy in the temperature range of 16–180 K. During thermal annealing of the samples, characteristic vibrational C–H modes of methane were monitored alongside the chamber pressure to register both structural changes and desorption of the film material. The obtained results reveal that upon the codeposition of methane and water, methane molecules appear both in non-bound and trapped states. The observed broadening of the characteristic C–H stretching mode at 3010 cm–1 upon an increase in temperature of the sample from 16 to 90 K, followed by narrowing of the peak as the temperature is reduced back to 16 K, indicates localization of methane molecules within the water matrix at lower temperatures.

Key words: molecular crystals, water-methane films, vibrational spectroscopy, low temperature, methane localization.

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