Investigating defect evolution during thermal treatment in Ni–Cr alloy using positron annihilation spectroscopy

Maheshwari, P.; Keskar, N.; Sudarshan, K.; Manikrishna, K.V.; Krishnan, Madangopal; Pujari, P. K.

doi:10.1007/s10853-020-05455-z

Cited by 5 publications

(1 citation statement)

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“…Positron annihilation lifetime spectroscopy (PALS) technique is considered as one of the promising alternative methods to analyze free volume and defects in functional and other materials [1][2][3][4][5], including ceramics [6][7][8], glasses [9][10][11], polymers [12][13][14], nanocomposites [15][16][17], etc. There are already several attempts to develop a phenomenological model describing the processes of positron annihilation in metal powders that contain Cu-, W-, Ni- [18], some types of BaTiO 3 [19][20][21] and SrTiO 3 perovskites [22,23], nanocrystallite ferrites [24,25], Ni-Cr alloy [26], In 2 O 3 nanocrystals [27], irradiated W and Fe [28], water diffusivity transition in composites [29,30] and others. Different approaches to the analysis of annihilation spectra as well as decompositions with a different number of components were introduced.…”

Section: Introductionmentioning

confidence: 99%

Positron Annihilation Lifetime Spectroscopy Insight on Free Volume Conversion of Nanostructured MgAl2O4 Ceramics

et al. 2021

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Herein we demonstrate the specifics of using the positron annihilation lifetime spectroscopy (PALS) method for the study of free volume changes in functional ceramic materials. Choosing technological modification of nanostructured MgAl2O4 spinel as an example, we show that for ceramics with well-developed porosity positron annihilation is revealed through two channels: positron trapping channel and ortho-positronium decay. Positron trapping in free-volume defects is described by the second component of spectra and ortho-positronium decay process by single or multiple components, depending on how well porosity is developed and on the experimental configuration. When using proposed positron annihilation lifetime spectroscopy approaches, three components are the most suitable fit in the case of MgAl2O4 ceramics. In the analysis of the second component, it is shown that technological modification (increasing sintering temperature) leads to volume shrinking and decreases the number of defect-related voids. This process is also accompanied by the decrease of the size of nanopores (described by the third component), while the overall number of nanopores is not affected. The approach to the analysis of positron annihilation lifetime spectra presented here can be applied to a wide range of functional nanomaterials with pronounced porosity.

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