Obtaining and investigation of a finely dispersed fraction of granulated blast-furnace slags for use as components of clinker-free binders

A method for obtaining a finely dispersed fraction of ground blast-furnace granulated slag has been developed. The resulting material with the introduction of an alkaline additive can be offered as an alternative to foreign analogous fine-dispersed mineral binders, an example of which can be microcement. A comprehensive study of granular slags of two metallurgical plants was carried out, the physicochemical characteristics of materials were determined. The possibility of obtaining a fraction of ground granular slag with a particle size of no more than 16 microns using vortex electromagnetic homogenization and subsequent air classification is shown.

Composite materials based on Al2O3‒SiC‒TiB2 obtained by SHS extrusion and their hightemperature annealing

As a result of the combination of the processes of selfpropagating high-temperature synthesis (SHS) and shear high-temperature deformation, realized in the method of SHS-extrusion, ceramic rods based on Al2O3‒SiC‒TiB2 were obtained. The influence of technological parameters of the process (delay time, pressing pressure) on the length of the obtained rods has been studied. The obtained materials were annealed in the range 1000‒1300 °C, and the microstructure and phase composition of the materials were studied before and after heat treatment.

The structure and phase composition of the cermet charge in the Al‒Al2O3 system obtained using mechanical processing of aluminum powder in a planetary ball mill

The cermet charge in the Al‒Al2O3 system was obtained by mechanical processing (MP) in a planetary ball mill of aluminum powder of the industrial grade PAP-2 (GOST 5494‒95), consisting of flake particles of submicron thickness with a coating of stearin. Depending on the MP modes used, 4 types of charge were obtained, the bulk density of which varied from 0,33 to 1,1 g/cm3. For all types of charge, the synthesis of the α-Al2O3 phase was observed as a result of the exothermic reaction of the interaction of air oxygen with the surface of aluminum particles during the MP. It is also possible to form boehmite and gibbsite when the activated surface of Al particles interacts with atmospheric water vapor. The local X-ray spectral analysis (EDX) was used to detect X-ray amorphous carbon in the composition of the charge, the appearance of which is associated with the impact- shearing effect of grinding bodies, leading to the nucleation of X-ray amorphous carbon inclusions due to the termal destruction of stearin. The maximum bending strength of the sintered cermet was 550 MPa. This cermet is characterized by a discrete fracture: the formation of dimples as a result of the shear of layered packets under the action of tangential stresses. The revealed mechanisms cermet’s fractures allow us to establish the optimal modes of MP of powder compositions for obtaining various constructional elements from them.

Evaluation of the thermal stability of composite powder materials in a plasma jet

The results of studies of the thermal stability of materials operating in a plasma jet at high temperatures and a sharp change in thermal loads are presented. It has been proven that the use of plasma generators with the introduction of various powder materials makes it possible to simulate the operating conditions of parts in high-temperature gas flows with heated particles. The effect of the introduced powder materials on the thermal stability of samples prepared by plasma spraying from molybdenum, as well as tungsten and tungsten-based compositions is investigated. An installation is proposed for assessing the thermal stability of composite materials and protective hardening coatings operating under high-temperature gas flows, which makes it possible to determine their erosion resistance.

Numerical simulation of the dynamics of dust in a rotary dust collector with an adjustable air flow

A rotary dust collector has been developed that works on the principle of a centrifugal separator. A feature of its design is the presence of a bypass recirculation channel of cleaned air with a flow regulator, two outlet pipes with flow uncoilers in the form of spiral channels. The calculation of the motion of dust particles with a density of 3000 kg/m3 and a diameter of 1 to 100 microns has been performed. Research has been carried out to improve the efficiency of the apparatus using a central compositional plan and to establish rational design and operating parameters of the mixer for recirculating and purified air.

Synthesis and thermal behavior of nanoceramic material based on Bi13Fe5Ti6O39

The process of formation by the chemical coprecipitation method of nanoceramic material based on layered perovskite-like complex oxide Bi13Fe5Ti6O39 with the structure of the Aurivillius phase has been described. The temperatures of the onset of formation, the onset of decomposition, and activation of sintering, as well as the coefficient of linear thermal extension of the material, have been determined. Technological parameters for the synthesis of the material with a high yield of the target product and the ability to vary the crystallite size in the range of 70‒85 nm have been determined.

Composite zircon ceramics based on raw materials activated by ammonium bifluoride

The results of studies of the synthesis processes of baddeleyite-zircon ceramics based on fluorinated plasmadissociated and natural zircon are presented. It was found that to obtain densely sintered ceramics based on fluorinated natural zircon, the introduction of CaO is required to stabilize free ZrO2 in the composition of the ceramics. The introduction of Y2O3 into the composition of ceramics based on plasma-dissociated zircon makes it possible to reduce the sintering temperature from 1600 to 1500 °C. It is difficult to obtain ceramics based on plasmadissociated zircon with a high degree of fluorination due to the formation of an excessive amount of ZrF4.

The use of Karelia’s finelyground mining waste and local clay for production of heatinsulating materials

The results of the study of fine-grained feldspathic and talcchlorite waste from Republic of Karelia’s mining companies as a new mineral product for heat-insulating materials and stationary heat accumulators (fireplaces and furnaces) are reported. The physico-mechanical and thermal-physical properties of the materials, based on finely ground waste and local clay, are appraised. The materials produced from pegmatite waste are highly strong, and can be used for lining furnaces and fireplaces. Heat-insulating materials based on talc-chlorite waste have low thermal expansion at 20‒900 °C, their thermal resistance increases 9 times (at 980 °C, water) and their mechanical strength is 2,6 times higher than that of samples containing talcum powder.

Force analysis of the stress-strain state of the surface layer of Al 2O3‒TiCceramics with AlN and TiN coatings

Regularities of stress-strain state of surface layer of Al2O3‒TiC-ceramics with AlN and TiN coatings under the action of force load are established using the methodology of computer engineering. The features of influence of AlN and TiN coatings on the nature of changes in the stress intensity in the surfaces of structural elements forming the surface layer of Al2O3‒TiC ceramics are determined. The formation of microstructural stress concentrators at the boundary of the AlN and TiN coatings with the initial ceramics is revealed.

Cementless refractory castable. Part 9. HCBS and ceramic concretes in the Al2O3‒SiO2‒SiC system

The priority-chronological aspect of research and technological development in the field of SiC-containing HCBS and ceramic castables in the systems Al2O3‒SiO2‒SiC and Al2O3‒SiO2‒SiC‒C is characterized. The results of studies on the effect of the firing temperature and prolonged (up to 100 h) high-temperature heat treatment on the oxidation kinetics of SiC of different dispersion and content are considered. A noticeable oxidation, accompanied by an increase in the mass and growth of samples, is noted after 1200 °C and significant at 1300‒1400 °C. The effect of the firing temperature in the range of 1000‒1400 °C and long holding in a tunnel furnace (60 h at 1300‒1400 °C) on the dynamics of phase transformations and the structure of samples of the matrix system based on HCBS of composite composition (bauxite + 11 % VFQG), as well as with an additional content of 15% SiC. In contrast to firing in air, during the service of monolithic gutter masses in the Al2O3‒SiO2‒SiC‒C system, the working surface of concrete is largely isolated from the air due to cast iron and slag. This drastically reduces the rate of both SiC oxidation and carbon burnout. The zonal structure of the lining is characterized. The data on the effect of heating and cooling on the modulus of elasticity of ceramic castable are presented.