Описан простой способ прогнозной оценки выхода детонационных наноалмазов, учитывающий массовое содержание элементов в углеродсодержащем взрывчатом веществе общей формулы CaHbNcOd. Установлена эмпирическая зависимость содержания детонационных наноалмазов в полупродукте синтеза наноалмазов — алмазной шихте в зависимости от содержания углерода в молекулах взрывчатых веществ. Приведены зависимости выхода детонационных наноалмазов от содержания химических элементов в исходной системе, позволяющие давать количественные прогнозные оценки выхода детонационных наноалмазов. A simple method of predictive estimation of the yield of detonation nanodiamonds is described, which takes into account the mass fractions of elements in the carbon-containing explosive with a general formula CaHbNcOd. An empirical dependence of the content of detonation nanodiamonds in the semi-product of nanodiamond synthesis (diamond charge mixture) on the fraction of carbon in molecules of explosives is derived. The yield of detonation nanodiamonds is presented as a function of the fractions of chemical elements in the initial system, which makes it possible to give quantitative predictions of the yield of detonation nanodiamonds.

The paper proposes a modified Maxwell formula applied to the calculation of the thermal conductivity of nanofluids. It is shown that the use of elongated particles or chains of nanoparticles leads to a significant increase in thermal conductivity. Theoretical estimates based on the proposed model are in good agreement with experimental data.

A calculation method of size distribution of heavily postcritical nucleation centers in the presence of a flow in melt or vapour for first-order phase transition, i.e., crystallization or condensation, is proposed. The considered method has been confirmed by an experimental investigation of the centrifugal casting of Al.

A model describing the features of field emission from carbon nanomaterials is considered. The model is based on taking into account the effect of electron drag by ballistic phonons in the region of the temperature gradient inside the emission center. The model does not require any additional assumptions about the special energy structure of the emission center. Quantitative estimates of the thermopower coefficient, made on the basis of the emission model, are in good agreement with the experimental results.

AbstractWe demonstrate that it is technologically possible to obtain graphite-like films which can be used for the creation of a thermoelectric generator. The proposed technology ensures uniformity and rather small thickness of these films and allows them to be formed on a diamond-like film substrate with deposited contacts at acceptable interface. Measurements show that the electron-phonon drag effect in this system ensures thermo-emf values about 100 times as large as those provided by the diffusion process. Arrangement of the graphite-like material on a diamond-like film substrate also favors increase in the thermo-emf, which is a manifestation of the electron–ballistic phonon drag. It is established that conditions necessary for the creation of a thermoelectric generator can be achieved based on the proposed carbon nanostructures.

AbstractThe structural, electrical, and optical properties of thin graphite-like films produced by magnetron- assisted sputtering onto crystalline silicon and quartz at substrate temperatures in the range from 320 to 620°C are studied. From analysis of the Raman spectra, it is established that, as the substrate temperature is elevated, the crystallite size increases and the concentration of structural defects and the content of amorphous carbon in the phase composition of the films decrease. It is found that, as the substrate temperature is elevated, the maximum of the absorption intensity in the ultraviolet spectral region of the optical absorption spectra shifts to longer wavelengths and the absorption intensity in the visible and near-infrared spectral regions increases. As the deposition temperature is elevated, the conductivity of the films increases from 0.2 Ω^–1 cm^–1 at 320°C to 30 Ω^–1 cm^–1 at 620°C.

Дизайн градиентных композитных материалов на основе алюминия и графита методом центробежного литья© Е

AbstractThe effect of rotation flow emerging under centrifugal casting on the first-order phase transition, i.e., crystallization, has been studied using the example of producing a gradient composite material of AK12 aluminum alloy in a mixture with basalt fibers. It has been shown that a material with a hardened surface can be created. Distribution of admixtures in the main material when there is macroscopic motion has been found.

A method of centrifugal casting of aluminum composites in a mixture with Al2O3 and C is proposed and proved by experiments. It is shown that there is a possibility of constructing gradients of admixtures, that is, of hardening the surface layer. It is specified how the concentration gradients are formed: the first technique is use of buoyance force and the second technique is redistribution of nuclei by size when they are exposed to rotation.

Новая идея состоит в использовании для повышения коэффициента термоэдс эффекта увлечения электронов потоком тепла, а для уменьшения коэффициента теплопроводности --- рассеяния тепла на границах, разделяющих графитоподобные и алмазоподобные области в композите, созданном из углеродных наноструктур. Предлагаемая структура термоэлектрического преобразователя содержит в качестве основного элемента тонкий (20-50 нм) слой графитоподобной области, находящейся на рекордно малом расстоянии от алмазоподобной области. Оценки показывают, что термоэдс может быть в 103 раз больше, чем при диффузионных процессах. В идеальных условиях это позволяет достичь величины термоэлектрической эффективности 150 при комнатной температуре. Представлены обоснования работ по гранту N 16-19-00075 Российского научного фонда. DOI: 10.21883/FTP.2017.07.44649.35

It is shown that an analog of Thomson waves, existing in an ideal fluid, is possible in metals and semiconductors. Possibility of observation of such waves is discussed.

A theory is developed for a new type of transition — a change in the ratio of the longitudinal and transverse dimensions of a convection cell as the thickness of a liquid layer is varied. A sudden change in the ratio of the cell dimensions takes place because of a change in the predominant mechanism for excitation of convection. The governing influence of buoyancy forces gives way to one of thermocapillary forces, and they in turn give way to the influence of thermoelectric forces for yet thinner layers. As the layer thickness is reduced gradually at a fixed external heating, the ratio of the dimensions will take on the values 0.7, 0.65, and 1, respectively.

In the process of melting of a semiconductor (semimetal) by, for example, laser radiation, heating also occurs along the surface of the melt. We consider a model in which the heat flux is strictly parallel to the layer and take into account the thermoelectric effect. It is shown that the usual longitudinal motion under such conditions can be converted into cellular motion. The possibility of observing this effect is discussed. O 1996 American Institute of Physics. [S 1063-776 1 (96)00909-21