Kinetics models describing degradation-relaxation effects in nanoinhomogeneous substances

Abstract

Abstract. The mathematical models of degradation-relaxation kinetics are considered for jammed systems composed of screen-printed spinel Cu 0.1 Ni 0.1 Co 1.6 Mn 1.2 O 4 and conductive Ag or Ag-Pd alloys. Structurally-intrinsic nanoinhomogeneities due to Ag and Ag-Pd diffusants embedded in spinel phase environment are shown to define governing kinetics of thermally-induced degradation obeying an obvious non-exponential behaviour in the resistance drift. The stretched-to-compressed exponential crossover is detected for degradation-relaxation kinetics in these systems with conductive contacts made of Ag-Pd and Ag alloys. Under essential migration of conductive phase, the resulting kinetics is though to be considerable twostep diffusing process originated from Ag penetration deep into spinel ceramics. IntroductionThe jammed systems prepared from high-temperature state by so-called fluid-to-solid transition compose an important class of substances for practical using [1]. Being quenched in far-fromequilibrium configuration, these materials demonstrate response on different degradation-relaxation inputs, tending towards equilibrium in the controlled parameter N(t) through compressed-exponential relaxation (CER) kinetics (super-exponential, i.e. faster than simple exponential decay):

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

“…To identify the underlying free-volume nanostructurization processes occurring in the pelletized g-As 2 Se 3 /PVP nanocomposite, the PAL spectrum of pelletized dry-milled g-As 2 Se 3 is considered in respect to wet milled one using the x3-x2-CDA [18][19][20][21], the results of this PAL-spectra treatment procedure being gathered in Table 3.…”

“…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.…”

“…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. This approach allows resolving additional input with defect-specific τ int lifetime and I int intensity in the second component of the reconstructed x2-term PAL spectrum of nanostructurized matrix, provided compensating (τ n ,I n ) input in the first component obeys complete equilibrium [18][19][20][21].…”

“…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. This approach allows resolving additional input with defect-specific τ int lifetime and I int intensity in the second component of the reconstructed x2-term PAL spectrum of nanostructurized matrix, provided compensating (τ n ,I n ) input in the first component obeys complete equilibrium [18][19][20][21]. Parameterization of Ps-to-positron trapping conversion in the nanostructurized matrix (conversion direction is defined by I n and I int signs) is achieved accepting (τ n ,I n ) and (τ int ,I int ) as the first and the second components of x2-term PAL spectrum employing two-state STM [16,[23][24][25].…”

“…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].…”