Free-volume characterization of nanostructurized substances by positron annihilation lifetime spectroscopy

Mechanochemically driven amorphization of nanostructurized arsenicals, the case of β-As4S4

“…For inhomogeneous solids, where annihilation is expected through positron-Ps channels so that only o-Ps traps are transformed in positron-trapping centers, the formalism of Ps-to-positron trapping conversion [10,[22][23][24][25][26] can be applied to identify free-volume structure. Within this approach referred to as x3-x2-CDA (coupling decomposition algorithm) [22], we deal with x3-term PAL spectrum transformed to generalized x2-term form for reference and NP-modified (nanostructurized) solids, second component involving contributions from all other channels (positron trapping, o-Ps decaying, and p-Ps self-annihilation).…”

“…This allows assuming that at MM with increased rotational speed n, only Ps traps are transformed into positron traps and vice versa. Hence, we can try to parameterize this trappingconversion process employing the x3-x2-CDA [22][23][24][25][26] for tested MM probes in respect of non-milled (coarse-grained) REHE-0 one, the results being gathered in Table 4. These data clarify that at n = 200-500 min -1 , the free-volume changes in MM Figure 3 Comparison of raw PAL spectra of b-As 4 S 4 -based REHE-0, REHE-200, REHE-500, and REHE-600 arsenicals (the insert shows depressed and right-shifted peak due to amorphization).…”

“…In REHE-200 pellet, the spherical Ps traps with R 3 = 0.286 nm disappear (see Table 3), being replaced by positron traps with defect-specific lifetime s int = 0.335 ns (see Table 4). These sites can be identified as interfacial free-volume holes between neighboring crystallite grains forming so-called triple junctions (TJs) [10,[22][23][24][25][26]40]. With known semiempirical correlations for As-S compounds [41][42][43], these positron traps can be ascribed to bi-/tri-atomic vacancies characterized by (s int -s b NP ) = 0.09 ns and s int /s b NP = 1.37 (Table 4).…”

Free‐volume structure of polyvinylpyrrolidone‐capped glassy As2Se3 nanocomposites prepared by mechanical milling

“…This approach allows reliable determination of positron trapping modes (such as defect-specific τ d = τ d and defect-free bulk τ b positron lifetimes, trapping rate in defects κ d ,) only under condition of slight contribution from Ps-decaying modes (radius of spherical holes R and fractional free volume f v ). For inhomogeneous solids, where annihilation is expected through mixed positron-Ps channels so that only Ps-traps are transformed in positron-trapping centers (and vice versa), the formalism of Ps-topositron trapping conversion [5,6,12,[18][19][20][21] can be applied to identify free-volume defects appeared under such nanostructurization. Within this approach referred to as x3-x2-CDA (coupling decomposition algorithm) [18][19][20][21], we deal with x3-term PAL spectrum transformed to generalized x2-term form for both reference (unmodified) and nanostructurized solids (caused, in part, by incorporation of guest NPs in host matrix), the second component involving all possible positrontrapping and Ps-decaying contributions.…”

“…In this work, free-volume structural arrangement in the PVP-capped glassy g-As 2 Se 3 prepared by high-energy wet MM is studied comprehensively employing the method of positron annihilation lifetime (PAL) spectroscopy, which is known to be an efficient nondestructive experimental probe for nanostructurization in nanocomposite materials [16][17][18][19][20][21].…”