A set of works on the creation of a technology for the manufacture of various products from materials based on silicon nitride is presented. Technologies make it possible to manufacture products of the widest range of applications - from porous corrosive media permeable for filtration to those close to theoretical density for structural parts.
A description of the installation for determining the ultimate strength of refractory materials in compression at elevated temperatures is considered. The values ??of the ultimate compressive strength of periclase-carbon materials in the temperature range 20 - 500 ° C are given. The analysis of the process of destruction and strength characteristics is carried out.
The indicators of long-term strength (time and deformation to failure) of dense-sintered oxide ceramics in the temperature range 1400 - 1600 ° C at loads up to 60 MPa have been determined. There is a relationship between the characteristics of creep and ductile fracture: regardless of the crystal size in ceramics and the test conditions, the product of the steady-state creep rate and the time to fracture is constant, i.e. deformation to failure is constant. Thus, from the results of measurements of the creep rate, the durability of the materials can be established.
The microstructure of the fracture surface of a filament of aluminum oxide and the inhomogeneity of the structure of a filament of aluminum oxide in the radial direction are investigated. The thickness of the strong shell and the structure of the weaker core of the filament have been determined. Based on the results of tensile tests to rupture of filaments of different diameters, an assumption was made about the effect of the shell thickness on the strength of filaments made of aluminum oxide.
Nanocrystalline powders (Zr 1-x Y x ) O y were synthesized by the combined method of coprecipitation and hydrothermal decomposition. Granulometric composition certification, X-ray phase analysis were carried out, pycnometric density of the synthesized powder was determined.
The synthesis of blue pigment by coprecipitation of nickel and aluminum from nitrate solutions with anionite AB-17-8 in the OH-form with subsequent calcination of the precursor at a temperature of 750 ° C has been proposed. The resulting product was investigated by methods of thermographic and X-ray analysis, as well as spectrophotometry (IR and diffuse reflection). According to the results of electron microscopy, the size of the pigment particles was 0.3 ?m.
An energy-efficient method for creating composite materials based on SiC modified with oxide eutectic additives with high mechanical characteristics has been developed. The effect of the addition of ultrafine powder to industrial silicon carbide on the physical and mechanical properties of ceramics has been investigated. The ratio of silicon carbide and sintering additive was determined, and a dense material with low porosity and high strength was obtained. The resulting ceramics is a new structural material that is promising for use as body armor.
The influence of hydroxyl and other functional groups on mechanochemical interactions in oxide powders is shown. The regularities of non-covalent mechanochemical synthesis have been established. Phenomenological models are discussed and equations of kinetics of mechanochemical synthesis are presented.
By the method of traditional sintering of samples, formed by cold isostatic pressing, from nanosized powder Si 3 N 4 with additions of Al 2 O 3 and Y 2 O 3 ceramics with a dense nanoscale structure were obtained. The microstructure and density of the obtained ceramics are investigated. The technological conditions for the production of silicon nitride ceramics, which provide an optimal combination of a fine-grained submicron structure and high density, have been determined.
The process of phase formation in the system of oxides NiO - CuO - Fe 2 O 3 - Cr 2 O 3 has been studied. It was found that in the presence of a mineralizer, the process of structure formation leads to the formation of two spinel-like phases of nickel ferrite and copper chromite. In the absence of a mineralizer, a solid solution of nickel-copper ferrite-chromite is formed. At a heat treatment temperature of 900 ° C, the presence of the delaphosite phase CuCrO 2 was found in the samples.
