Effect of H2O on the Pressure-Induced Amorphization of Hydrated AlPO4-17

Abstract

The incorporation of guest species in zeolites has been found to strongly modify their mechanical behavior and their stability with respect to amorphization at high pressure (HP). Here we report the strong effect of H2O on the pressure-induced amorphization (PIA) in hydrated AlPO4-17. The material was investigated in-situ at HP by synchrotron X-ray powder diffraction in diamond anvil cells by using non- and penetrating pressure transmitting media (PTM), respectively, silicone oil and H2O. Surprisingly, in non-penetrating PTM, its structural response to pressure was similar to its anhydrous phase at lower pressures up to ~1.4 GPa, when the amorphization was observed to start. Compression of the structure of AlPO4-17 is reduced by an order of magnitude when the material is compressed in H2O, in which amorphization begins in a similar pressure range as in non-penetrating PTM. The complete and irreversible amorphization was observed at ~9.0 and ~18.7 GPa, respectively, in non- and penetrating PTM. The present results show that the insertion of guest species can be used to strongly modify the stability of microporous material with respect to PIA, by up to an order of magnitude.

Strongly Modified Mechanical Properties and Phase Transition in AlPO4-17 Due to Insertion of Guest Species at High Pressure

“…A very strong discontinuous decrease in c , along with a marked increase in a , occurs at this pressure, which can be linked to the appearance of nonhydrostatic stress. The effect of nonhydrostratic stress was also observed previously on compressing monoclinic, hydrated AlPO 4 -17 in H 2 O with discontinuities in the pressure dependence of the cell parameters and volume at the solidification pressure of H 2 O at 0.9 GPa. In N 2 in the fluid state, a discontinuous increase in a is observed, giving rise to increases in volume, Figure .…”

Mechanical Characterization of Anhydrous Microporous Aluminophosphate Materials: Tridimensional Incompressibility, Ductility, Isotropy and Negative Linear Compressibility

“…The enormous amount of research devoted to the synthesis and characterization of the microporous aluminophosphate materials by X-ray, neutron and synchrotron diffraction, NMR, and spectroscopic techniques and to the study of their thermal stability, thermodynamic, and general physical and chemical properties is strongly in contrast with the poor current mechanical characterization of these materials [165][166][167][168][169][170][171][172]. As far as we know, only the compressibility and phase transitions induced by the application of isotropic pressures in ALPO-5 [167], VPI-5 [168][169][170] and ALPO-17 [171,172] have been studied. Therefore, the number of ALPO materials whose elasticity has been investigated is very small and the only mechanical property considered is the compressibility.…”

The pressure response of Jahn–Teller-distorted Prussian blue analogues

“…For example, PIA can be used to trap hazardous gases, 70 and may serve as a shock-absorbing mechanism. 71 Many molecular frameworks typically display a relatively low critical pressure for amorphisation (p a ), which can be tuned further by the guest species. [71][72][73] Our results mirror this, as Cu [Co] 0.67 $nH 2 O remains crystalline to higher pressures than Cu [Co] 0.67 (p a < 1 GPa).…”

“…71 Many molecular frameworks typically display a relatively low critical pressure for amorphisation (p a ), which can be tuned further by the guest species. [71][72][73] Our results mirror this, as Cu [Co] 0.67 $nH 2 O remains crystalline to higher pressures than Cu [Co] 0.67 (p a < 1 GPa). Thinking towards design principles, PIA is believed to be linked to the presence of negative thermal expansion (NTE) 74,75 and Cu[Co] 0.67 indeed belongs to the class of NTE materials, with a coefficient of thermal expansion of −20(2) MK −1 .…”