Confined H2O molecules as local probes of pressure-induced amorphisation in faujasite

Abstract

Confined H2O molecules act as local probes for depressurization phenomena during the pressure induced amorphisation of faujasite NaX at which the OH stretching frequency first decreases and then increases almost to its room pressure value upon further compression. Pair distribution function (PDF) analysis provides evidence that amorphisation corresponds to a collapse of the structure around hydrated sodium cations with strong distortion of the secondary building units (double six-membered rings, sodalite cages). Both the use of guest molecules as local probes in far- and mid-infrared spectroscopy, where we correlate intermolecular water H bonding vibrations and internal mode behaviour under confinement, and PDF analysis could be of great use to study the mechanical behaviour of other hydrated materials.

High pressure induced phase transition and superdiffusion in anomalous fluid confined in flexible nanopores

“…In this technique, the nanopore walls had translational freedom in the z-direction, acting like a piston in the fluid, and a constant force controls the pressure applied in the confined direction. This scenario is similar to some recent experiments on water confined inside nanopores at externally applied high pressures 53,54 . Considering the nanopore flexible walls, the resulting force in a fluid particle is then…”

Different Water Networks Confined in Unidirectional Hydrophilic Nanopores and Transitions with Temperature

“…8. The vertical line is a guide to the eye for the vHB2 sub-band position at T = 300 K. In agreement with the OH band deductions, we expect two water networks with (i) H bonding established between confined water molecules and (ii) between proximal water and the AlPO4-54•xH2O framework [45] . Based on the gH (E), calculations, Fig.…”

“…The INS, mid-and far-IR spectral profiles of the vibrational modes of water confined in the AlPO4-54•xH2O nanopores (connectivity, librational and stretching) can be described by several overlapping Gaussian components after removing the slowly rising linear background [21,45,52,53] . This technique was recently applied successfully to other AlPO4 molecular sieves and zeolites to evidence the correlation between structural and vibrational properties [21,45,53] . A complete description can be found in previous work [21,45,53] .…”

“…8, and by previous studies on AlPO4-54 [21] . Water molecules can establish bonds between confined water molecules (such as innerinner and/ or proximal-proximal water) and between proximal water and the AlPO4-54•xH2O framework [45] . In analogy with the measurements by Zanotti et al [56] , presented in the insert of Fig.…”

Structural evolution of water and hydroxyl groups during thermal, mechanical and chemical treatment of high purity natural quartz

“…42 while pressure, and consequently stress, present in minerals shi OH stretching modes typically to lower wavenumbers. 27,43 On the other hand, connement of water in pores Table 1 Components of OH stretching modes of surface OH groups and in bulk minerals, including assignment to different species according to selected literature, at or around room temperature. The top part of the table contains modes from OH groups and the bottom part those from bulk minerals.…”