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This article presents the results of the binder jetting technology application for the silicon nitride ceramics production. A modified version of the Plan-B 3D printer with an epoxy-based binder was used for silicon green bodies preforming. Silicon powder was pre-coated with epoxy resin, and the curing agent was added during 3-D printing of green bodies using a standard cartridge. Curing and removal of organics was carried out during the high-temperature vacuum drying of the printed preforms. Reaction-bonded silicon nitride was obtained by using pressureless sintering. An additional compaction of green bodies is proposed to reduce the porosity of green bodies and sintered ceramics. It is shown that the proposed methods allows to improve the mechanical properties of sintered specimens.

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The low-temperature oxidation process of carbon-carbon composite materials (CCCM) with a pyrocarbon matrix has been examined. Oxidation at temperatures of 450 to 700 °C is characterized by internal burnout of the carbon phase without a noticeable change in the experimental samples external volume. Oxidation resistance analysis of CCCM structural components was performed. CCCM and carbon fibers specific surface area were estimated by the low-temperature adsorption of nitrogen and krypton using the Brunauer-Emmett-Teller model and the theory of density functional model. Pore size distribution was calculated by the semi-empirical Horvath-Kawazoe method. A significant increase (about 10-15 times) in specific surface area of the composite material, together with a rise in free volume ~5%, was accompanied by total weight loss of about 5%. Specific surface area changes occur as a result of anisotropic etching of carbon fibers surface with the formation of micropores with 0.5–2.0 nm diameter range. Although macropores are formed mainly due to the oxidation of thermosetting binder pyrolysis residue, they do not contribute to the specific surface increase but solely provide access to micropores. Microporosity evolution leads to an increase of structural discontinuity degree and, ultimately, to the loss of matrix-filler contact boundary. As a result, an overall weakening of material mechanical characteristics is to be noted. Thus, oxidative degradation is closely related to the increase in void space. A follow-up study is on-going. In fact, an open question remains, namely whether the oxidative process occurs differently in the micropores of diameter less than 2 nm and how it may contribute to the oxidative stress resistance behavior of CCCM.

This study discusses the creation of heat-resistant dielectric composite material based on organosilicon polymers for the manufacture of gas discharge chamber (GDC) for the electric rocket engine (ERE). A binder has been proposed that meets the high requirements for vibration resistance and electromagnetic permeability of GDC in the megahertz range of electromagnetic waves. Based on this binder filled with silicon nitride powder, GRС was designed; this product was fully tested as part of laboratory 200 kW ERE. The research of structural transformations that occur during heating of materials was carried out by synchronous thermal analysis. The material obtained in the result of the experiment, the basis of which was SiSiB®PVMQ filled with Si3N4 60% by mass, is characterized by a number of properties that are structured and described in this study. As a result of the study, it was demonstrated that the studied material is characterized by heat resistance up to 400 ºС. On the basis of these materials, the authors produced a GDC, which was tested as part of a laboratory model. It was established that the increase in mass loss over 400 °C is due to the initiation of the process of thermal degradation of the main polymer chain.

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