The high-pressure behavior of ulexite [ideally NaCaB5O6(OH)6x5(H2O)], a B-bearing raw material (with B2O3 ca. 43 wt%) and a potential B-rich aggregate, has been studied by in-situ single-crystal synchrotron X-ray diffraction up to 9.5 GPa, in order to explore its stability field at high pressure, the anisotropy of its compressional behavior and the deformation mechanisms at the atomic scale. Ulexite undergoes a first-order iso-symmetric phase transition, reconstructive in character, between 6.44 and 7.13 GPa (to the ulexite-II polymorph); the crystal structure of ulexite-II was successfully solved and refined. For the low-P polymorph of ulexite (stable in all the working conditions as aggregate in concretes), the isothermal bulk modulus here obtained is KV0 = 36.9(5) GPa, with a strongly anisotropic compressional pattern (finite-Eulerian principal components of the unit-strain ellipsoid: e1:e2:e3 =7:3:1). Ulexite-II also shows a marked anisotropic compressional pattern and with a resulting bulk softening (KV0 = 26(4) GPa).

Phase transition and high-pressure behavior of ulexite, a potential aggregate in radiation-shielding concretes / D. Comboni, F. Pagliaro, G.D. Gatta, P. Lotti, T. Battiston, M. Merlini, M. Hanfland. - In: CONSTRUCTION AND BUILDING MATERIALS. - ISSN 0950-0618. - 291(2021 Jul), pp. 123188.1-123188.12.

Phase transition and high-pressure behavior of ulexite, a potential aggregate in radiation-shielding concretes

F. Pagliaro
Secondo
Writing – Review & Editing
;
G.D. Gatta
Supervision
;
P. Lotti;T. Battiston;M. Merlini
Penultimo
;
2021

Abstract

The high-pressure behavior of ulexite [ideally NaCaB5O6(OH)6x5(H2O)], a B-bearing raw material (with B2O3 ca. 43 wt%) and a potential B-rich aggregate, has been studied by in-situ single-crystal synchrotron X-ray diffraction up to 9.5 GPa, in order to explore its stability field at high pressure, the anisotropy of its compressional behavior and the deformation mechanisms at the atomic scale. Ulexite undergoes a first-order iso-symmetric phase transition, reconstructive in character, between 6.44 and 7.13 GPa (to the ulexite-II polymorph); the crystal structure of ulexite-II was successfully solved and refined. For the low-P polymorph of ulexite (stable in all the working conditions as aggregate in concretes), the isothermal bulk modulus here obtained is KV0 = 36.9(5) GPa, with a strongly anisotropic compressional pattern (finite-Eulerian principal components of the unit-strain ellipsoid: e1:e2:e3 =7:3:1). Ulexite-II also shows a marked anisotropic compressional pattern and with a resulting bulk softening (KV0 = 26(4) GPa).
Ulexite; Crystal structure; Elastic moduli; Stability; Phase transition
Settore GEO/09 - Georisorse Miner.Appl.Mineral.-Petrogr.per l'amb.e i Beni Cul
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/2434/841791
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