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Water-Vapor Sorption Processes in Nanoporous MgO-Al(2)O(3) Ceramics: the PAL Spectroscopy Study
The water-vapor sorption processes in nanoporous MgO-Al(2)O(3) ceramics are studied with positron annihilation lifetime (PAL) spectroscopy employing positron trapping and positronium (Ps)-decaying modes. It is demonstrated that the longest-lived components in the four-term reconstructed PAL spectra...
Autores principales: | , , , , |
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Formato: | Online Artículo Texto |
Lenguaje: | English |
Publicado: |
Springer US
2016
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Materias: | |
Acceso en línea: | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4783312/ https://www.ncbi.nlm.nih.gov/pubmed/26956602 http://dx.doi.org/10.1186/s11671-016-1352-6 |
Sumario: | The water-vapor sorption processes in nanoporous MgO-Al(2)O(3) ceramics are studied with positron annihilation lifetime (PAL) spectroscopy employing positron trapping and positronium (Ps)-decaying modes. It is demonstrated that the longest-lived components in the four-term reconstructed PAL spectra with characteristic lifetimes near 2 and 60–70 ns can be, respectively, attributed to ortho-positronium (o-Ps) traps in nanopores with 0.3- and 1.5–1.8-nm radii. The first o-Ps decaying process includes “pick-off” annihilation in the “bubbles” of liquid water, while the second is based on o-Ps interaction with physisorbed water molecules at the walls of the pores. In addition, the water vapor modifies structural defects located at the grain boundaries in a vicinity of pores, this process being accompanied by void fragmentation during water adsorption and agglomeration during water desorption after drying. |
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