Том 60, № 3 (2019)

Requirements for special-purpose alumina for the ceramic, electronic and refractory industries are considered. Analysis and comparison of acidic methods for preparing alumina from the point of view of efficiency, adaptability and production safety are provided. The risks of alumina acidic production methods are estimated. The advantage of the sulfuric acid method versions is substantiated.

A chemical and mineral classification of technogenic mineral raw materials is developed suitable for production and ceramics. Secondary mineral resources of the Ural region are considered.

A free SHS-compression method was used to produce large-sized plates measuring 120 × 80 × 8 and 80 × 40 × 8 mm from a titanium boride-based material using 120 kN press equipment. The structural features as well as physical and mechanical properties of the obtained materials were studied. The samples were annealed in an oxidizing atmosphere at 1100°C for 10 hours.

Results are given for development of technology for electrolytic deposition of protective and electrical insulating ceramic coatings. The technology developed consists of combining microarc oxidation with imposition of excess pressure in a closed autoclave with the introduction of nanoparticles into the coating formation probe.

Methods for determining pore volume distribution with respect to size of porous materials are analyzed and it is shown that the most precise methods are those in which capillary effects do not appear. It is shown that mercury porosimetry and the method of liquid displacement by gas have considerable errors in the large pore region, which is due to a percolation effect. It is shown that determination of the pore volume distribution from air flow measurement gives too distorted results, so its use is inadvisable.

The effect of the addition of 2 and 5 mol.% Dy₂O₃ during spark-plasma sintering at a compaction loading of 60 MPa in the range of 1200 – 1600°C on phase composition, microstructure, relative density, open porosity, linear shrinkage, physicomechanical properties, and linear correlation of the elastic modulus and fracture toughness of mullite–sialon–TiC samples is shown. The synthesized powders of sialon and TiC are characterized by corresponding intensive crystallization. The increase in the content of Dy₂O₃ from 2 to 5 mol.% in the sintered composition to produce β-SiAlON/TiC = 70/30 mol.% promotes intensive mullitization, active growth of sialon and less intensive growth of TiC in the range of 1200–1600°CC, and also leads to the formation of less densely sintered crystalline microstructures in the sample, containing round crystalline TiO₂ particles, pores and glassy phase at the boundaries of the regions in mullite–sialon–TiC solid solution composites at 1500°CC. Asample containing 5 mol.% Dy₂O₃ has lower values of relative density, linear shrinkage, physical and mechanical properties in the range of 1200 – 1600°CC, lower crack resistance with the formation of microcracks at 1500°CC and a slightly larger linear correlation of the elastic modulus and impact toughness in the range of 1200 – 1600°C.

The possibility of improving concrete strength properties, primarily mechanical strength, by cement modification with nano-additives and using activated water for mixing concrete mixtures is evaluated.

The effects of iron-containing compounds on Si₂N₂O production during burning in N₂ of an Si + SiO₂ mixture were studied. It was established that the phase composition and morphology of the crystalline combustion products depended on the iron-containing compound. Si₂N₂O powder without impurity phases was obtained in the presence of FeCl₃·6H₂O and formed polycrystalline fibers consisting of ultrafine crystals.

A simulation of radiant heat transfer to a single-layer flow of vermiculite moving along the vibrating hearth plate was performed, and the temperatures and their distribution from the central to peripheral (near-wall) working chambers of the firing modules were determined. An analytical model of thermal energy absorption by vermiculite is provided, which represents the basis for further study of the energy relations in the furnace- medium system during the vermiculite firing process.

The thermodynamic equilibrium conditions of bicarbonate leaching were analyzed and used to develop a mathematical model for determining the parameters giving the highest extraction of MgO from the raw materials. Laboratory experiments on magnesite samples from Satkinsk deposit, Chelyabinsk Region, confirmed that the simulation results were adequate.

A review of environmental protection technologies for the integrated disposal of metallurgical industry waste is given. The results of studies on obtaining and determining the basic physicochemical properties of a new composition of self-curing, chemically resistant refractory mass are presented. The mass is comprised of industrial waste, including slag from electrothermal reduction of niobium pentoxide — crushed and purified fused Al₂O₃ (electrocorundum), and scrap of periclase-chromite articles. The mass has high chemical resistance, fire resistance, mechanical strength, hardness, wear resistance.