Pogorelov A. Transport processes in solids under nonequilibrium conditions of excitation by a thermal pulse

The transport processes in a solid are investigated. These processes manifest themselves as directed transfer of mass, structurally dependent heat transfer and electric potential appear-ance in metals in nonequilibrium conditions caused by heat pulse from different sources of physical origin (laser, electric and glow discharges). The criteria under which these processes occur in the solid phase are established. One of them is a criterion of nonstationarity, which is inversely proportional to the thermal diffusivity of a substance, locally excited by thermal impulse. It enables us to determine the time during which the energy introduced into the solid is not relaxed by mechanisms of thermal conductivity. This approach made it possible to clearly separate the regimes of pulsed thermal action on a substance to create in it a nonequilibrium state and a quasi-equilibrium state used to determine a number of characteristics of a solid. It is shown that the nonequilibrium state in a solid is caused by thermal deformational processes that promote generation and directed movement of structural defects as a result of their interaction with the stress field. The determining role of moving dislocations in all experimentally established transport processes is indicated. In particular, mass transfer is caused by the entrainment of an interstitial atom by the core of an edge dislocation and transporting it to macroscopic depths within the limits determined by the energy of their interaction and the presence of drains. The proposed dislocation-interstitial model of mass transfer has been subjected to careful analysis with the use of the modified Frenkel-Kontorova equation and the molecular dynamics method. The model is proven to be consistent with the experimental data. The modification consisted of introducing into the equation terms that took into account the presence of an interstitial atom bound to the nucleus of the kink (dislocation) and the imaginary neighbouring atomic series, as well as the external force acting on the kink with the interstitial atom moving together, and the drains in the path of their motion. Heat transfer turned out to be strongly de-pendent on the degree of nonequilibrium and is manifested in the scattering of phonons by dislocations, depending on the degree of their mobility and the direction of propagation of the heat flow and dislocations. The presence of such a connection was confirmed experimentally in the original study using thermal probing of samples by the Parker method: in a nonstationary excitation regime, a higher velocity of temperature propagation in the direction of the motion of structural defects was recorded. The appearance of the electric potential in a pulse excited metal is due to the mechanisms of electron-phonon interaction with the formation of quasiparticles (polarons) - electrons localized by the elastic field of dislocation. The determining role of dis-locations in this process was confirmed experimentally in foils with different structural states - polycrystalline (Mo) and amorphous (Fe74,5Si13,5B8Cu1Nb3). A generalized scheme of transport processes occurring in a solid excited by a thermal pulse is offered. It gives a clear idea of the course of the observed phenomena. On the basis of the obtained fundamental achievements, new methods of influencing solids, which were atomic and molecular crystals, were developed. These solids were subjected to structural modification under the influence of laser irradiation, electric discharge and ion bombardment in a glow discharge. A number of original developments on laser solid-phase alloying of Ti with ruthenium and Al with chromium (outside their mutual solubility) have been demonstrated. The possibility of applying a photon-ion interaction using multiphoton ionization is demonstrated by the use of chemical heat treatment in laser-activated glow discharge plasma. The possibility of creating Me@Cn-type compounds like Ni@C60 and Cd@C60 by thermal annealing and ion bombardment in a glow discharge is shown. Special attention is paid to the use of pulsed thermal excitation in a quasi-stationary mode for rapid measurements of the thermo-physical characteristics of solids and evaluation of the adhesion properties of coatings and multilayer film structures. A significant part of the presented developments is protected by copyright certificates and patents of Ukraine.