The article considers one of the approaches to modeling the process of mixing of polydisperse powders, which includes three main fractions of different sizes, the shape of which is close to spherical. The work is aimed at reducing material costs at the stage of development of mixing processes by reducing the number of experiments. Aiming to obtain the most uniform mixing with the minimum time of the technological process, the model is based on the target function for a certain number of iterations of mixing of the composition to obtain the required (maximum possible) density of the package of mixed solid particles.To develop a model of the mixing process, one of the heuristic algorithms – the “metal annealing method” – was used. As a representative element of the model, an elementary cell in the form of several hexagonal densely. Packed particles around one introduced into the composition of the composite material (in a small amount, from 5 to 15 %) as a modifier was adopted. The mo del is formalized with the condition of averaging the particle sizes within each fraction, as well as the morphology of their surface. The number of particle repackaging iterations is calculated by the probability of obtaining the minimum amount of voids in the representative element and the uniformity of distribution of the modifying element.Comparison of the values obtained during the simulation with the measured values of the mixing results on a specific mixer will form a scale of compliance of the simulation results with the operating modes of the process equipment. This will make it possible to predict the appropriate mixing modes at the stage of development of the technological process with the possible system of fluctuations in the characteristics of the supplied raw materials and, thereby, to create a methodological basis for the formation of quality management of manufacturing heterogeneous composite material. The model can be adapted for polydisperse powders with the content of the main fractions of more than three.
The article describes a possible way of introducing nanoscale powders into energy-saturated heterogeneous composite materials (ECM). By the example of polydispersed nanoscale carbon, the main well-known methods for introducing nanoscale components into dispersed and high-viscosity colloidal systems have been studied, their effectiveness has been evaluated, and limitations have been revealed. The main influencing factors on the uniform distribution of nanoscale components in the volume of the composite material and the ways of leveling their influence have beenfound. A technological scheme has been proposed for increasing the distribution uniformity of nanoscale components due to their preliminary deposition on the surface of the material prevailing in quantity of dispersed component while limiting the growth of its specific surface as a method of further reduction of the viscosity of the energy-saturated heterogeneous composite material at the stage of mixing its liquid and solid phases.The rate of change of the form factor, specific surface and distribution of the nanoscale diamond-containing additive over the particle surface of ammonium salt of perchloric acid has been studied depending on the modes of mixing the components in a gravity mixer. Acceptable technological mixing modes have been found.The main tasks of further study of phenomena arising at the phase boundary when introducing nanoscale additives into the dispersed medium of ECM have been determined.
The use of materials and technologies of powder metallurgy in the components of missile and space engineering is considered. The possibilities of these technologies are shown when producing composite materials, as well as products and coatings thereof through the example of radioabsorbing and radiotransparent materials. The methods for the synthesis of radioabsorbing materials based on ferrimagnetic materials (Ni0 0.58 Zn0 0.36 Mn 0.06 Co 0.028 Fe 2 O 4-nickel-zinc ferrites and hexagonal barium ferrite with W-phase (BaCo 2 Fe 16 O 27), obtained by MAS and MASHS methods were worked out. Methods of producing high-temperature ceramic radioabsorbing materials using alumina as a dielectric matrix, and a resistive material containing the MAX-phases Ti 2 AlC and Ti 3 AlC 2 and heat-resistant FeSiTiAl alloy as an electromagnetic pulse absorber were investigated. The production technique of a ceramic composite radiotransparent material based on high-alumina ceramics in the Al 2 O 3-SiO 2-TiO 2 system is proposed. The specific technological features of the powder metallurgy method, ensuring the production of materials and products (coatings) for missile-space technology with the required properties, are given. The promising directions and main tasks for powder metallurgy in the field of producing energy-saturated heterogeneous composite materials are determined.
One of the approaches to modeling of the structure formation of an energy-saturated heterogeneous composite material (EHCM) by mixing its components represented by liquid and solid phases was considered. To develop a model of the mixing process, one of the heuristic algorithms was used, i.e. the metal annealing method. The model is formalized with the condition of averaging the particle sizes within each of the fractions, as well as the morphology of their surface. As a representative element of the model, an elementary cell is adopted in the form of hexogonally densely packed particles around one introduced into the composition of the composite material (in small amounts, from 5 to 15 %) as a modifier. The voids in the cell are filled with liquid polymer. The developed model is based on the objective function, which assumes obtaining a uniform distribution of components with the required density of their packing and filling the voids with a liquid phase while minimizing the number of mixing iterations. A comparison of the values resulted during modeling with the measured characteristics of mixing on a particular mixer will make it possible to form a matching scale of the modeling results to the operating modes of technological equipment. This will determine the appropriate modes of mixing the components at the stage of development of the technological process of EHCM production.
Carbon fiber reinforced carbons (CFRC) are used to work in extreme environments because of their erosion resistance, ablative ability, and high mechanical characteristics at extremely high temperatures. The production of such materials includes several cycles of gas-phase or liquid-phase densification of initially porous carbon fibers reinforcement. The paper analyzes the main process parameters and densification routes, and their role in the manufacture of CFRC with high performance. A method for calculating changes in the density and porosity of CFRC during a multi-cycle densification has been developed. The results of the experiments confirmed the adequacy of this method.
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