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Graphite has a special place amongst nonmetallic materials because of its unique physicomechanical and chemical properties, of which the main ones are the high resistance to thermal shock, low elastic modulus, high thermal conductivity and specific heat, fairly high strength, low thermal expansion coefficient, small neutron capture cross section, and inertness in corrosive media (acids, and solutions of salts and organic compounds [1-3]). The main disadvantages indicated by the general use of graphite in high-temperature processes are the low heat resistance and the erosion and burning in gas flows [4, 5]. There are various techniques for avoiding such undesirable characteristics.One way of effectively protecting graphite from oxidation is to produce a protective layer on the surface. Coatings of various types have been tested: diffusion ones (deposited from vacuum or from gases), plasma ones, ones formed from the gas phase by the deposition of refractory-metal halides, metal condensation from vacuum, and the deposition of various coatings followed of the National Academy of Sciences of the Ukraine has made a considerable contribution to research on protecting graphite with rate metals, the trends in coating graphite, and the development of suitable technologies [6][7][8][9][10][11][12][13][14][15][16]. At high temperatures, the protection by rare metals is governed by reactions between the metal and the solid surface at the interface [7]. Transition metals (chromium, zirconium, and titanium) form stable chemical bonds with carbon and wet graphite well, while copper, lead, tin, antimony, bismuth, and other nontransition metals do not wet it properly. The most active of the transition metals are those with high defectiveness in the d or f electron shells. A small amount of titanium added to other transition elements such as copper and tin markedly increases the tendency to wetting, on account of reduction in the wetting angle and increase in the work of adhesion. The main shortcomings that reduce the protective power of the coatings made by immersion or deposition from the gas phase are the brittleness and the tendency to peel from the substrate.To overcome these drawbacks, a new method has been proposed [8-13] for making protective coatings on graphite that in,olves two successive operations: depositing the metal layer from the liquid phase under vacuum and diffusion treatment with carbon, boron, nitrogen, and silicon. Metal layer deposition from the liquid involves interaction of the graphite with the metal, which increases the adhesion strength, which rises during the subsequent diffusion saturation. The metal layers have fairly high strength. Good thermal resistance is provided by the transition diffusion layers, which reduce the stress gradients between the coating and substrate. Reliability and good adhesion are provided at high temperatures by the formation of the coating consequent on the interaction with the substrate.Under working conditions (at lower temperatures), the interaction of the coating with t...

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В роботі запропоновано удосконалення моделі Арреніуса, на основі якої проаналізовано залежності пожежобезпечного терміну експлуатації ізоляції кабельних виробів від напруженості електричного поля та температури, при цьому напруженість електричного поля та температуру представлено як випадкові величини.

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The studies reported here have made it possible to determine the optimal ways of fire protection, in which the samples of modified complexite have reduced flammability. The sample with the ions of molybdenum (VI), treated with phosphoric acid, had the highest magnitude of oxygen index among five modified samples of the fiber. This is the most fire-protected sample, which contains three types of flame retardants: nitrogen (amidoxime groups of complexite, phosphorus (treatment with phosphoric acid) and molybdenum (VI). The obtained data indicate the chemical interaction of flame retardant with complexite. The morphology of fibers and the process of their destruction are influenced by the introduction of flame retardants. Scanning electronic microphotographs show the existence of a morphological change of the surface at modification of the complexite samples with flame retardant. The introduction of flame retardant into complexite affects the process of thermal destruction of the samples in the air and argon media. At the same time, the introduction of molybdenum (VI) significantly reduces the thermal stability of fibers. It is likely that processes of thermal destruction can be catalyzed by metals both in the air medium and in the argon medium. The magnitudes of order of reaction of thermal decomposition at the transition from a fiber sample treated only with acids to the samples of complexite containing molybdenum (VI) decreases up to 0.38. At the same time, the values of activation energies E, kcal/mol, and the enthalpy of the process of thermal destruction of complexite DH, kcal/mole also decrease. The mechanical properties of fibers at the introduction of flame retardants into the fiber composition change insignificantly. Depending on the composition of flame retardants, rupture load decreases by 6-11 %, lengthening of the samples decreases by 6-16 %. Thus, there are some grounds to suggest that it is possible to create fibrous materials based on cellulose with predetermined properties of reduced flammability

The object of this study is the process of impregnation of liquid into the bulk material, in particular, into the soil. Determining the impregnation parameters is a relevant task when assessing the consequences of an emergency spill of a hazardous liquid. Infiltration of liquid into the soil leads to pollution of water resources. However, the greatest danger is the ignition of the spill of a combustible liquid. Based on the Green-Ampt model, a mathematical description of the impregnation of liquid into bulk material was built. It is a system of two ordinary differential equations of the first order, one of which describes the reduction of the thickness of the liquid layer on the surface, and the other describes the dynamics of the impregnation of liquid into depth. The solution to the system was derived in the form of time dependence on the depth of impregnation. An experimental study was conducted on the example of impregnation of crude oil in the sand. To this end, sand was poured into a vertical measuring glass cylinder. After that, the liquid was poured and a video recording of the impregnation process was carried out. By processing the video recording, the depth of impregnation and the corresponding time were determined. The results of the study show that the relationship between the thickness of the liquid layer on the surface of the sand and the depth of impregnation is linear in nature: the relative deviation of linear approximation from experimental data does not exceed 3.5. By expanding the logarithmic function contained in the solution to the system of differential equations into the Taylor series, a polynomial dependence of time on the depth of impregnation was established. To determine the coefficients of the polynomial based on the experimental data, the least squares method was used. In this case, the approximation error after the first minute after spilling does not exceed 10 %. The proposed method could be used to account for seepage in the model of liquid spreading on the ground and the burning model of a flammable liquid spill