We examine the transmission of quantum particles (phonons, electrons, and photons) across interfaces, identifying universal patterns in diverse physical scenarios. Starting with classical wave equations, we quantize them and derive kinetic equations. Those are matching conditions for the distribution functions of particles at the interface. We note the time irreversibility of the derived kinetic equations -- an essential feature for accurately describing irreversible processes like heat transport. We identify the juncture in our derivation where the time symmetry of wave equations is disrupted, it is the assumption of the non-coherence of incident waves. Consequently, we infer that non-coherent transmission through the interface exhibits time irreversibility. We propose an experiment to validate this hypothesis.

We calculate the Kapitza conductance, which is the proportionality coefficient between heat flux and temperature jump at the interface, for the case of two conducting solids separated by the interface. We show that for conducting solids in a non-equilibrium state, there should also arise the electrochemical potential jump at the interface. Hence to describe linear transport at the interface we need three kinetic coefficients: interfacial analogs of electric and heat conductances and interfacial analog of the Seebeck coefficient. We calculate these coefficients for the case of an interface between n-type semiconductors. We perform calculations in the framework of Boltzmann transport theory. We have found out that the interfacial analog of the Seebeck coefficient for some range of parameters of the considered semiconductors, has a high value of about $10^{-3}$ V/K. Thus this effect has the potential to be used for the synthesis of effective thermoelectric materials.

A new method for the calculation of interfacial thermal resistance in the case of heat transport through the interface by phonons is introduced herein. The novelty of the suggested approach consists of the consideration of all the consequences of a nonequilibrium character of phonon‐distribution functions during heat transfer. The well‐described diffuse mismatch model is used to introduce a model set of transmission and reflection amplitudes of phonons at the interface. An exact analytical solution for the proposed model is derived. Finally, the problem is solved for a set of transmission and reflection amplitudes characterized by a free parameter.

A new mechanism of heat transfer in nanofluids is proposed on the basis of two physical principles: Brownian motion of particles in a fluid and thermal resistance of a particle—fluid interface. Owing to the thermal resistance of interfaces, the temperature of particles may differ from the temperature of the surrounding fluid; i.e., the particles may be superheated or supercooled. The diffusion of superheated or supercooled particles makes an additional contribution to the heat flux. It turns out that this contribution is negligible for the fluid with the inclusion of nanoparticles. At the same time, the contribution to the heat transfer by this mechanism is large and may be dominant for a gas with the inclusion of nanoparticles.

Possibility of growth of diamond single crystals from nanodiamond particles by oriented attachment mechanism under influence of organic substances has been suggested and experimentally confirmed.It has been found that diamond single crystals ranging up to 1.5 mu m are formed from the 4-5 nm nanodiamond particles at high pressures and high temperatures treatment (HPHT: P similar to 7 GPa, T similar to 1300 degrees C). It has been experimentally shown that the necessary condition for the formation of the diamond single crystals is an addition of substances containing C-H groups into HPHT chamber.The formation of the diamond single crystals has been confirmed by several experimental methods, including Raman scattering, scanning electron microscopy (SEM) and electron energy loss spectroscopy (EELS). Analysis of experimental results has shown that mechanism of oriented-attachment growth is responsible for formation of diamond single crystals. A model explained details of the mechanism has been suggested. (C) 2017 Elsevier B.V. All rights reserved.

In this letter, we propose a new model that explains the Raman peak downshift observed in nanoparticles with respect to bulk materials. The proposed model takes into account discreteness of the vibrational spectra of nanoparticles. For crystals with a cubic lattice (Diamond, Silicon, Germanium) we give a relation between the displacement of Raman peak position and the size of nanoparticles. The proposed model does not include any uncertain parameters, unlike the conventionally used phonon confinement model (PCM), and can be employed for unambiguous nanoparticles size estimation.

A model of a thermoelectric generator is proposed, in which composite materials obtained by sintering diamond nanoparticles are used as the main component. To increase the useful conversion of heat into electric current, it is proposed to use the effect of electron drag by ballistic phonons. To reduce the ineffective heat spread, it is proposed to use the effect of thermal resistance of the boundaries between the graphite-like and diamond-like phases of the composite. An experimental confirmation of the existence of an optimal volume ratio between graphite-like and diamond-like phases of the composite is predicted and obtained. The highest achieved value of thermoelectric coefficient in the actual structure is 80 mu V K-1 ( which means 20 times increase compared to that of composites not of the optimal structure), with a thermal conductivity of 50 W m(-1) K-1. These results were obtained with constant electrical conductivity. The combined influence of these two effects in case of the ideal composite structure should result in an increase of the thermoelectric efficiency parameter by three orders of magnitude.

On the basis of experimental data on thermal conduction and sound velocity in composites obtained by sintering detonation nanodiamonds with the crystallite size of 4–5 nm and diamond micropowders with a grain size of about 10 μm at a high pressure (5–7 GPa) and high temperature (1200–1800°C), mechanisms of heat transfer in such structures are suggested. These mechanisms are shown to be different in composites of micro- and nanoparticles. In composites of micrometer particles, the conventional macroscopic mechanism of phonon propagation is active. In composites with a grain size of a few nanometers, the main contribution comes from thermal resistance on grain boundaries.

The new model of phonon transmission across the interface between two crystals is proposed featured by taking into account the mismatch of crystal lattices. It has been found that the mismatch of lattices results in phonon scattering at the interface even in the absence of defects. As it has been shown, at the normal incidence, longitudinally polarized phonons have much larger transmission coefficient than that of transversely polarized phonons, excluding the special resonance cases. For the quasi one-dimensional case the exact solution has been obtained.

The subject of this study is the thermoelectric efficiency (Z) and the thermoelectric parameter (ZT) of carbon nanocomposites, namely, the structures consisting of graphite-like (gr) and diamond-like (d) regions made of sp(2) and sp(3) hybridized carbon atoms, respectively. The impact of heat transfer across the boundary between sp(2) and sp(3) areas is analyzed for the first time. It is shown that the interfacial thermal resistance (Kapitza resistance) is not lower than the thermal resistance in the macroscopic gr region. The influence of various factors on the Kapitza resistance is analyzed. The value of ZT approximate to 3.5 at room temperature, taking into account the interfacial thermal resistance, is significantly higher than it would be in gr films (ZT approximate to 0.75).

A nonequilibrium distribution function in the presence of a heat flux at the interface between two crystals has been investigated in the model of a one-dimensional harmonic chain. Matching conditions of distribution functions for different sides from the interface have been derived. A method for the calculation of the boundary thermal resistance using the generalized Enskog-Chapman method has been proposed. The exact formula has been derived with simplifying assumptions.

It has been shown that the temperatures of electrons and phonons are different at a heat flow through a metal-insulator interface. This effect leads to an additional contribution to the Kapitza thermal resistance because electrons transferring heat in the metal do not transfer it through the interface, but are rather involved in heat transfer only at a certain distance from it. Consequently, heat transfer near the interface is less efficient. The effect is independent of the insulator adjacent to the metal. An exact solution has been obtained in a linear approximation. The results explain the qualitative difference of predictions of previously accepted models from experimental data in the case of large transmission coefficients of phonons through the interface.

A model of heat transport from an insulator (diamond) to a metal (copper) has been proposed taking into account energy transport to the oscillations inherent in the insulator but having frequencies much higher than the frequencies inherent in the fundamental oscillations of the metal. This problem is solved exactly in the one-dimensional case and in the one-constant approximation of bonding at the interface. It has been established that energy transport occurs in a thin layer near the metal boundary.