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The article provides a general overview of the production methods and applications of carbon materials with a large specific surface area. The following materials were taken as objects for the study: SK-AG-3 granular activated carbon produced by OJSC «Sorbents of Kuzbass», Kemerovo, activated cellulose fiber produced by the Krasnoyarsk Chemical Fiber Plant after carbonation, graphitization, and gas-phase activation at 900 °C in carbon dioxide current, Busofit-T carbon fabric produced by OJSC «SvetlogorskKhimvolokno», thermally expanded fluorinated graphite produced by OJSC «Siberian Chemical Combine». The porous structure of these materials was investigated by low-temperature volumetric nitrogen adsorption at the ASAP 2020 unit. Nitrogen adsorption-desorption isotherms were recorded in a relative pressure range of p/p0 = 0.05÷1.0 at 77 K. The specific surface area was estimated by the BET method based on the adsorption isotherm at p/p0 = 0.05÷0.30. The specific surface area was 485, 1241, 1156 and 290.5 m2/g for activated carbon, activated carbon fibers, Busofit-T fabric and thermally expanded graphite, respectively. The volume of mesopores and their size distribution were calculated by the Barrett-Joyner-Нalenda (BJH) method in a pressure range of p/p0 = 0.35÷0.95. The volume of micropores and their size distribution were calculated by the Horvath-Kawazoe method using the nitrogen adsorption-desorption isotherm in a relative pressure range of p/p0 = 0.00÷0.01. These methods were also used to determine the average diameter of mesopores and micropores. A comparative analysis of the results obtained was carried out. A relationship between the internal structure of the investigated materials and the porous structure properties was traced. It was shown that activated carbon, fibers, and carbon fabrics are microporous materials, and thermally expanded graphite has a mesoporous structure.

An analytical scheme for the analysis of silicified graphite SG-P, a four-phase composite material consisting of silicon, carbon, silicon carbide and silicon dioxide, has been developed. The procedure can be successfully used in the quality control of raw materials and in the study of the phase composition of finished products The porosity and density of the graphite base, as well as the impurities contained in the base and silicon change the course of silicification and the properties of the finished product as well. The impurities are the main reason for the formation of delamination, swelling, cracking and light spots on the treated surfaces. It should be noted that the iron content 0.023 – 0.17 wt.% in the carbon material intended for silicification, leads to catalytic graphitization of the artificial graphite and dispersion in the silicon melt. Methods of rapid assessment of the quality of raw materials are to be used to provide quick understanding of their suitability for manufacturing final products on their base. Quality control of the silicified graphite produced at the JSC «Research Institute Graphite» is carried out by determination of the phase composition of the finished product by chemical and X-ray diffraction methods of analysis. The content of silicon carbide (not less than 45%), unbound silicon and carbon (not more than 20 and 35%, respectively) affects the corrosion resistance and thermal expansion of silicified graphite.

Two-dimensional and four-dimensional reinforced carbon–carbon composite materials based on carbon structural filament are prepared via the isostatic carbonization of a coal tar pitch. The difference between the crystalline state of a reinforcing fiber and a coke matrix is assessed with X-ray diffraction analysis. A change in the level of the surface resistivity depending on the density of the samples and the degree of graphitization of a matrix is studied with eddy-current testing. We show that the degree of completion of formation of the internal structure influences the mechanical strength and the level of specific electrical resistance of the material. Measurement of the electrical resistivity with eddy-current testing appears to be a non-destructive method to assess changes in the structure of the material.

The application of the agricultural waste of cashew nut shells (CNSs) from the Ivory Coast is proposed for the production of activated carbon (AC) used in water treatment by the physical activation. Washed and crushed CNSs are carbonized at 800°C. The crushed CNS carbonizate is activated by the physical method in a temperature range from 400 to 700°C. The specific surface (SBET) and porous structure of the AC samples are investigated by low-temperature nitrogen desorption and X-ray structural (X-ray phase) analysis. The results show that an increase in the activation temperature at a fixed time leads to an increase in the material specific surface, the development of a microporous structure, and an increase in the summary volume of mesopores and micropores of AC. The X-ray phase analysis data shows that the degree of graphitization, interplanar spacing, and crystallite sizes vary insignificantly. The possibility of using CNSs to fabricate AC no worse in sorption properties than its analogs currently in use to purify water is proven.

Thermophysical properties are studied: thermal conductivity, heat capacity and thermal diffusivity of spatially reinforced carbon-carbon composite materials. A structural model is proposed for thermal conductivity levels at 300 and 2500 K. Results of calculations are confirmed in manufacturing practice and studies of material properties. It is shown that anisotropy of thermal conductivity levels leads to a nonuniform thermal state of refractory carbon composite working surface fragments. It is established that structure formation for the surface of a carbon-carbon refractory wall is connected with composite components structural state inhomogeneity. Approaches are proposed for increasing the working surface life for refractory carbon materials.

Carbon material thermal conductivity is an important factor for providing thermal shock resistance. The effect of production factors on the reproducibility of thermal conductivity values during manufacture of three-dimensional reinforced high-density carbon-carbon composite is considered. An average level of thermal conductivity applies to more than 82% of workpieces. From 4.6 to 12.5% of workpieces have thermal conductivity not less than 44 and not more than 70 W/(m·K). It is established that a change in carbon fiber treatment temperature from 1600 to 2400°C may lead to an increase in materials thermal conductivity by 0.21 W/(m·K) for each 100°C. Adifference in framework structure may change average thermal conductivity within the limits of 3 W/(m·K). Variation of material apparent density from 1.89 to 1.98 g/cm3 gives a change in thermal conductivity by 1.1 W/(m·K) for each +0.1 g/cm3. A connection is established for a carbon-carbon composite of electrical conductivity ρ and thermal conductivity λ, corresponding in form to the Weidemann-Franz rule λρ = const.

The aim of this work was to characterize the char of agricultural waste cashew nuts shells (CNS) and activated carbons prepared from CNS by physical activation method for the treatment of water. The characteristics studied are functional groups (phenol, carboxyl, and carbonyl), elemental analysis, pH and ash content. CNS from the Republic of Côte d’Ivoire were pre-treated and carbonized at 800°C. With the aid of the char obtained, three activated carbons were prepared corresponding to the following activation temperatures: 400, 600 and 700°C. The activation time was set at 30 minutes. The activating gas used is water vapor. The results showed that: the char contains no phenol (0.00 mg eq/g) and carboxyl (0.00 mg eq/g), but a quantity of carbonyl (0.8 mg eq/g) which gives it basic properties. The char and the activated carbon obtained contain 79.7 - 82.40% C; 1.2 -1.66% N; 1.2 – 1.9% H and 1.10-5 to 3.3.10-2% of the following elements: Al, B, Fe, Si, Mg, Ca, Co, Cr, Mo, Ti, Mn, Cu, Cd , Ni, Pd, V; the pH is 10,5-11,01 and ash is 5.66 - 7.31%. The specific surface area and the total volume of meso- and micropores of char obtained are respectively 3.56 ± 0.18 m2/g and 0,0047 cm3/g. The specific surfaces of activated carbons as a function of the activation temperature (400, 600, 700 °C) and the total volume of meso- and micropores are respectively: 45.3 ± 1.3; 165.7 ± 4.6; 316.6 ± 11.0 m2/g and 0.035; 0.098; 0.183 cm3/g. The adsorption-desorption isotherm of the char obtained is type IV. The adsorption - desorption isotherms of the activated carbons are of type I (Langmuir isotherm)., Ce travail a pour but de caractériser le carbonisât des coques de noix d’anacarde (CNA) et les charbons actifs (CAs) qui en sont obtenus par activation physique pour une application dans le traitement de l’eau. Les caractéristiques analytiques mesurées sont la composition élémentaire, le pH, le taux de cendre et les groupes fonctionnels (phénol, carboxyle, carbonyle). La surface spécifique et le volume total de méso - et micropores ont été également mesurés comme caractéristiques essentielles des propriétés d’adsorption.Des CNA issues de la République de Côte d’Ivoire ont été prétraitées et carbonisées à 800°C. Puis à partir du carbonisât obtenu, trois CAs ont été préparés par activation thermique aux températures de 400, 600 et 700°C respectivement. Le temps d’activation a été fixé à 30 minutes. Le gaz activant utilisé est la vapeur d’eau. Les résultats ont montré que le carbonisât ne contient pas de phénol ni de groupement carboxyles. On trouve en revanche des groupes carbonyle (0,8 mg eq/g) qui confèrent au carbonisât des propriétés basiques. Le carbonisât et les CAs obtenus contiennent 79,7 - 82,4 % de C ; 1,20 -1,66 % de N ; 1,2 - 1,9 % de H et des traces (1.10-5 à 3,3.10-2 %) des éléments suivants : Al, B, Fe, Si, Mg, Ca, Co, Cr, Mo, Ti, Mn, Cu, Cd, Ni, Pd, V. Le pH est 10,5-11,01 et le taux de cendre est 5,66 - 7,31 %. L’activation thermique a permis d’augmenter la surface spécifique des échantillons de 3,56 ± 0,18 m2/g dans le carbonisât à 45,3 ± 1,3 ; 165,7 ± 4,6 et 317 ± 11 m2/g dans les charbons actifs obtenue à 400, 600, 700°C respectivement. Les volumes totaux de méso - et micropores ont également été augmentés dans des proportions similaires.

The specific surface and porous structure of viscose-based carbon fibers produced by the Krasnoyarsk Plant of Chemical Fibers are investigated by low-temperature nitrogen adsorption using an ASAP 2020 device. The dependence of their specific surface and character of the pore-size distribution on gas-phase activation modes in the carbon dioxide stream at a temperature of 900°C is shown. It is established that the adsorption surface of carbon fibers can rise from 0.3 to 1900 m2/g during the activation. It is revealed that the prolongation of the activation time leads to an increase in the specific fiber surface owing to the appearance of numerous new micropores and the development of the microporous structure.

Ways of improving the refractoriness of carbon-carbon composite materials due to increasing their density and reducing oxidation rate, and in turn due to reducing the combustion surface, are studied. Oxidation heterogeneous reaction surface in an Arrhenius equation expression is considered as the sum of object outer surface and the reaction surface within pores. It is shown that with an apparent density of 1.93 g/cm3 or more surface oxidation at normal pressure and ~500 °C almost corresponds to the nominal object surface. Processing measures are suggested for improving carbon material refractoriness due to an increase in density and changing surface structure by special high-temperature treatment regimes.

The effect of a titanium coating on the sorption properties of carbon textile Busofit was studied. The BET specific surface area was about ·103 m2/g before and after metallization of the fiber. The micropore volume in samples accounted for most of the total pore volume.

The results of the study of morphological changes in the carbon fibers surface of "Kulon" based on PAN fiber and of carbon textile Busofit under irradiation with helium ions with energies of the order of hundreds of electron volts are presented. Scanning electron microscopy showed a significant ion-induced change in the morphology from the smooth fiber surface to a developed surface with the corrugations, nanowalls and whiskers of submicron height.