According to modern concepts, the surface layer of compounds is understood as the ultrathin cover, the properties, structure and composition are different from the crystalline substrate with this layer and this layer is in thermodynamic equilibrium. The surface layer consists of two layers - d(I) with thickness h = d, at which the phase transition occurs, and d(II) with the lower limit h≈10d, at which the physical properties of the crystal begin to manifest themselves. The thickness of the surface layer d(I) is determined by one fundamental parameter, the molar (atomic) volume of the element (Ʊ= M/ρ, M is molar mass (g/mol), ρ is density (g/cm3)). The average statistical structural unit of coal corresponds to higher fullerenes with the number of carbon atoms in the cluster >100, which is the unique feature of the coal substance, which is not a crystalline structure, but a complex polymer with a supramolecular structure. The thickness of the surface layer of the coal substance is two orders of magnitude greater than the thickness of pure metals and is close to the thickness of the surface layer of higher fullerenes C96 (135 nm). The increasing of the coal substance's porosity of 90 % is led to increasing the thickness d(I) of the surface layer by the order of magnitude, that is 2 microns. In this regard, the "apparent" change in the radius of a coal particle means a change in its mass, proportional to the release of methane from the solid solution. The dependence of the complete decomposition's time of coal methane is τ0 on the parameter |λ|. The equation which is obtained, includes the ratio of the heat flux introduced into the reservoir volume due to the internal heat release process to the heat flux which is carried away from the volume due to thermal conductivity. If this ratio exceeds a certain critical value of the unity's order, the thermal explosion occurs, leading to the decomposition of coal methane. The size effects in the d(I) layer are determined by the entire group of atoms in the system (collective processes). Such "quasi-classical" size effects are observed only in nanoparticles and nanostructures. The d(I) layer for coal matter extends from 151.5 nm (Anthracite) to 214.2 nm (Brown). The dimensional temperature of the carbon nanoparticle at the initial temperature T0 = 300 K will be at least Tm = 872 K. This corresponds to particles of the order of half a micron. Coal particles with the radius of about one micron (or marked half a micron) in the case of decomposition of coal matter are heated to temperatures at which spontaneous combustion of nanoparticles is possible. Hygroscopic moisture in the genetic line of coal has the certain pattern of change and correlates with the thickness of their surface layer.
In this paper we consider the influence of environmental parameters on the electrons work function and the contact potential difference of metal parts of machines. Experimental studies have been carried out, including measurements of the contact potential difference on samples from Al, Ti and Ni by the Kelvin-Zisman method at different temperatures, pressures and relative humidity, as well as in non-equilibrium and equilibrium environmental conditions. Measurements of the contact potential difference were carried out by the device "Surface-11". Atmospheric parameters were measured by the digital meteorological station HAMA EWS-800. The results of measurements of the contact potential difference of metals were processed by methods of mathematical statistics. The results of experimental studies have shown a direct effect of changes in ambient temperature on the contact potential difference and the electrons work function of metal samples, which has an average correlation. It is found that atmospheric pressure and relative humidity have a weak effect on the contact potential difference and the electrons work function of the metals under study, their influence can be neglected. The effect of equilibrium and non-equilibrium environmental parameters on the contact potential difference and electrons work function of metal samples is studied. The results confirming the reduction of the contact potential difference (increase in the electrons work function) of metals, as well as an increase in the mean square deviation of the measurement results under non-equilibrium environmental conditions are obtained. On the basis of the research it is recommended to measure the contact potential difference of metals in the laboratory.
АннотацияНаноразмерные частицы различных металлов обладают рядом новых физических свойств, обусловленных избыточной поверхностной энергией. В настоящей работе предложена формула и произведен расчет электропроводности металлических нанопленок диаметром 1, 10 и 50 нм.Ключевые слова: электрон, металл, нанопленка, проводимость, энергия. AbstractNanoscale particles of various metals have a number of new physical properties due to excess surface energy. In this paper, a formula is proposed and the electrical conductivity of metallic nanofilms with a diameter of 1, 10, and 50 nm is calculated.Введение В настоящее время в зависимости от структуры пленки принято выделять три основных типа проводимости [1, 2, 3]: 1) «Диэлектрическая» проводимость характерна для пленок, состоящих из отдельных (изолированных) наночастиц. Островковые пленки этого типа имеют очень малую проводимость, которая сильно зависит от расстояния между частицами.2) Перколяционная проводимость -образование непрерывного металлического пути между электродами. Сопротивление перколяционных пленок невелико, но оно больше, чем у объемного металла, из-за сильного рассеяния электронов на неоднородностях поверхности, границах зерен и др.3) Металлическая проводимость характерна для пленок со структурой близкой к сплошным пленкам.В настоящей работе рассмотрена металлическая проводимость для пленок, обусловленных размерным эффектом.Основные соотношения Для размерной зависимости некоторого физического свойства твердого тела A(d) нами получены соотношения [4]:
To describe the surface tension, a model of the surface layer of atomically smooth ferroelectrics was considered, neglecting the surface roughness. It is believed that a necessary condition for the manifestation of nanostructured properties of a condensed medium is the size dependence of its properties. The surface layer of an atomically smooth crystal consists of two layers, d(I) and d(II). The layer with thickness h = d is called layer (I), and the layer at h≈10d is called layer (II) of an atomically smooth crystal. At h≈10d, the size dependence of the physical properties of the material begins to appear. When h = d, a phase transition occurs in the surface layer. It is accompanied by abrupt changes in physical properties, for example, the direct Hall-Petch effect is reversed. It can be concluded that both previous and current results of studies of the surface of condensed media (metals, dielectrics, ferroelectrics, etc.) are due to size effects and the final structures of their existence.
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