Abstract
Peculiarities of water–adsorption processes in nanostructured humidity-sensitive MgAl2O4 ceramics studied by positron annihilation lifetime spectroscopy at three- and four-component fitting procedures were generalized. It is established that the shortest component with positron lifetime τ1 reflects mainly microstructure specificity of the spinel structure of ceramics, the second component with positron lifetime τ2 corresponds to extended defects near grain boundaries, the third component with lifetime τ3 is due to “pick-off” annihilation of oftho-positronium in the nanopores filled by adsorbed water, and the fourth component with lifetime τ4 is based on oftho-positronium interaction with physisorbed water molecules at the walls of the pores. It is shown that adsorption of water leads to transformation of positron annihilation spectra in the MgAl2O4 ceramics and reflects increasing of positron trapping near grain boundaries of ceramics and ortho-positronium decaying in nanopores. The fixation of water-dependent positron trapping inputs allows to refine the most significant changes in positron trapping rate of extended defects near grain boundaries.
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