Results in research and development of structural ceramics (high-temperature ceramic monolithic and composite materials based on high-melting nitrides, carbides, and oxides (Si 3 N 4 , BN, SiC, Al 2 O 3 , ZrO 2 ) and wollastonite) are reported from the Tekhnologiya Research and Production Enterprise. Superior properties of the materials are emphasized.The Research and Development (R&D) Center "Structural ceramic materials, constructions, fabrication technology, and operational reliability management of thermally stressed ceramic components" set up at the Tekhnologiya Research and Production Enterprise and currently headed by Academician A. G. Romashin has gained general acceptance within the relevant scientific communities both at home and abroad [1 -3].Researchers and engineers at the R&D Center have made a significant contribution to the theoretical and experimental study of new ceramic materials intended for structural engineering applications. Scientific foundations for the design of thermally stressed components made up from brittle materials have been laid. New standard engineering solutions and design principles have been formulated, and programs for thermal strength analysis and integrated operational reliability management have been developed within the conceptual scheme material -properties -numerical analysis -structure -technology -trial tests (Fig. 1).A unique research and production base in Russia and, perhaps, over the world has been set up equipped with advanced facilities (high-temperature furnaces operating at 1700 -2200°C under vacuum and 1750°C in air, vacuumcompression furnace, hot-pressing units, a hydrodynamic pressing machine, gas and tunnel furnaces, mechanical testing machines operating at 1600°C in air and 2000°C under vacuum and in an inert medium).A total of 30 structural ceramic materials based on silicon carbide and nitride, alumina and zirconia, and boron nitride and aluminum titanate with controlled microstructure and tailored properties for operation in the temperature range of 1500 -1800°C, in conformance with international standards on mechanical, thermophysical, and tribological characteristics and resistance to aggressive media, have been developed. The materials and technologies for their preparation have been supported by patents and have found applica-

As required by the purpose and operating conditions of the articles, Si3N4-based ceramic materials must have a combination of properties ensuring their serviceability, while their manufacturing process must afford the manufacture of complex-shaped products. The paper deals with the technology of making complex-shaped articles from reaction-bonded, densified silicon nitride in the system Si3N4, Si3N4-BN, Si3N4-Al2TiO5, Si3N4–Si by thermoplastic slip casting of a fine high-purity silicon powder comprising additives or sintering aids with subsequent nitridation at temperatures up to 1500°C or additional sintering up to 1750-1800°C. In the process of making reaction-bonded silicon nitride, consideration is given to the exothermal effect of reaction, to the influence of additives on the properties of ceramics and the manufacturing process. Methods of oxidation protection of porous Si3N4-based ceramics and adaptation of these methods to protection of porous SiC- or SiC-C – based ceramics are discussed. Upon densification of reaction-bonded silicon nitride at temperatures up to 1750- 1800°C, consideration is also given to the effects of diffusion processes of the additives, used as sintering aids, on ceramics microstructure. The mechanisms of dissolution – recrystallization of α- and β-Si3N4 in the course of forming the self-reinforced ceramic structure are discussed. The peculiarities of making Si3N4-Si – based material having unusual properties including the mechanism of forming, oxidation resistance, electrical conductivity and high impact resistance are covered. The paper presents the results of testing of the ceramic components and units of gasturbine engines, bearings and attachments of the spacecraft Buran, and it also gives test data with reference to the ceramic parts tested at temperatures above 2000°C.

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A new technology has been developed for making refractory products based on the naturally occurring wollastonite (calcium metasilicate) intended for the aluminum industry. The application of natural wollastonite requires no hydrothermal treatment in an autoclave, which considerably simplifies the manufacturing process and reduces its cost. A qualitative comparative analysis of natural wollastonite from different mineral deposits was made to choose an optimal modification with consideration for its availability. The articles were made by using steel-mold pressing, slip casting and vacuum forming methods. For the development of technology for manufacturing large-sized complex-shaped products the slip casting method was used and the slip basic composition was determined comprising 80% of wollastonite as a basic solid phase and 20% of plasticizers. The improvement in the thermal resistance of wollastonite-based ceramics is assured by applying special techniques, namely by addition of course-grained fillers. Thus, addition of about 15% of a course-grained fraction into the fine wollastonite-based slip improves the thermal resistance of ceramics and affords 2-3 times increase in their service life. The efficient way to increase the wollastonite-based ceramics thermal resistance is addition of inorganic fibers. With the use of an inorganic fiber, the materials have been produced with an apparent density ranging from 0.5 to 1.5 g/cm3 and an ultimate compressive strength of 0.5 to 10 MPa. The study has been made into ceramics structure comprising inorganic fibers. The developed materials are chemically inert to aluminum melt. They show no sticking, no mechanical erosion and they are thermal-resistant. With the above methods, the following products are being made on the basis of the naturally occurring wollastonite: spouts, lining plates, heat nozzles, stopper-rod devices, pipes and other articles that have been operating successfully in the aluminum industry of Russia.