Refractories and Industrial Ceramics最新文献

Barium aluminate ceramics with iron (III) oxide and lithium hydroxide additives was obtained by solid-phase synthesis. It has been established that high-temperature treatment in an oxidizing environment contributes to the production of vacuum-tight samples that meet the “absolutely impermeable” tightness criterion, while having a density of 3.75 g/cm³, compressive strength of 597.1 MPa, and electrical conductivity ranging from 1.50·10 ^{– 7} to 1.05 × 10^–4 S/cm (at 90 – 300°C).

The article considers a method for activating cement hardening processes using nanomaterials due to the magnitude of their surface energy: when injected into concrete, nanoparticles dump it as they tend to transition to a stable state. Such activity leads to a significant gain in strength and hardness, resulting in high-strength concrete. It is shown that such an effect can be achieved by surface impregnation of concrete with sols (colloidal solutions) based on SiO₂ nanoparticles. It is feasible to start impregnation from day three of hardening under normal conditions. At this time, the main heat generated as a result of cement’s intrinsic exothermic hardening reaction has already been released into the ambient, and the introduction of additional energy will not cause a shift in equilibrium towards slowing down the hardening processes in accordance with the Le Chatelier’s principle. The article also presents the results of physicochemical studies of concrete after hardening to clarify this effect.

The results of grinding powdered and solid zirconium and aluminum oxides in various grinding units, i.e., ball, planetary, and bead mills, are presented. The grinding materials were PSZ-5.5Y brand partially yttrium-stabilized zirconium dioxide (USA) and Almatis CT 3000 GS brand alumina with an α-phase content of >99.0 wt.% (Germany). The use of bead mills with ZrO₂ grinding balls of dimensions 0.6 – 0.8 mm with an M:W ratio of 1:4 and a specific grinding energy of 0.6 – 0.8 kW was advisable to obtain high-purity and ultrafine oxide powders. Solid-phase sintering of the oxide powders was activated and the densities of the ceramic materials increased for aluminum oxide from 3.50 – 3.78 g/cm³ and for zirconium oxide from 5.40 – 5.89 g/cm³ if the ultrafine state of the initial oxide powders was achieved.

Increasing the service life and reducing the cost of refractories remains a critical task for metallurgical production. One way to solve it is to use new composite materials in the production of modern refractories. Test results for alloying of PUPK-SH ladle products with boron-containing composite antioxidants obtained by the SHS method are presented. Laboratory tests established that PU-products containing SHS-antioxidants NI-TRO-BORAL NB-1 (BN·Al₂O₃) and BorTiX^® MM (2TiB₂·TiC), instead of or together with the current anti-oxidant additive (APV-P grade aluminum powder), had better characteristics of slag resistance, oxidation, and physical and mechanical properties after firing. PUPK-SH products containing boron-containing SHS antioxidants were recommended for pilot industrial testing based on the laboratory test results.

The influence of temperature-time parameters on linear thermal expansion coefficient (LTEC) of materials based upon MoSi₂-B-Al₂O₃ is established. It is shown that by changing composite composition and heat treatment conditions it is possible to influence the LTEC value significantly.

Premature decommissioning of a steel-teeming ladle lining due to critical localized damage, which significantly reduces lining functional properties, is one of the most acute problems in modern metallurgy. The main type of products used for steel-teeming ladle lining is periclase-carbon. In order to improve corrosion resistance and resistance to thermomechanical loads, additional additives, such as spinel, and high alumina CMA cement, are introduced into periclase-carbon products. In this article the effect of calcium aluminate-based additive on the properties of periclase carbon refractories is investigated. It is assumed that there is a potential for formation of magnesium aluminate spinel (MA) in periclase-carbon products with calcium-aluminate additives during heat treatment. Fused periclase is used as the raw material, the carbon component is represented by natural flaky graphite in an amount of 10 wt.%, and a combined binder. An additive based upon calcium aluminates is introduced, with a fractional size from 0 to 3 mm, while the amount of main fractions of fused periclase is reduced by the corresponding amount of the additive introduced. The compressive strength, apparent porosity, and bending strength values before and after coking firing are analyzed. The thermal coefficient of linear expansion, phase composition and microstructure of the products are also investigated.

The purpose of the work was to obtain a heat-resistant binder with the addition of metakaolin from mineral and man-made raw materials of the Aral Sea region. The results of preparing alumina cement using kaolin, limestone, and alumina-containing waste were presented. Effective compositions of alumina cement in the kaolin-limestone-alumina-containing waste system were developed. The preparation of metakaolin with its subsequent addition during clinker grinding was investigated to improve the physicomechanical properties of a heat-resistant binder. The reliability of the results was confirmed using modern physicochemical methods.

Improvement of plasma deposition wear-resistant coatings technology is demonstrated. At the same time, special attention is paid to one of the most important parameters, i.e., thickness of a functional layer, since when using plasma deposition methods it has a significant impact on coating quality, as well as functionality and productivity of the process. Based upon planning an experiment, mathematical models are developed that make it possible to establish a relationship between coating thickness and plasma spraying process production parameters. Results of analyzing the dependences obtained show that coating thickness is most affected by plasma torch arc current strength.

Information is provided about thermally expanded graphite (TEG) properties and production by oxidation modification, excluding graphite matrix destruction. The possibility of introducing TEG into the structure of periclase concrete as a carbonaceous component is studied. Physicochemical properties of periclase-carbon concrete are determined using TEG, as well as slag resistance of the samples obtained.

High-temperature annealing of a composite material based on the Ti₃SiC₂ MAX-phase dispersion-strengthened with TiC and TiB₂ particles obtained by free SHS compression was carried out. The annealing was carried out in an oxidizing atmosphere at 900, 1100, and 1300°C for 10 h and at 1400°C for 4 h. Experimental dependences of the specific weight gain of the oxidized samples and the oxidation rate on the temperature and annealing time were plotted. The effect of annealing temperature on the phase composition, structure, and mechanical properties of the materials was established based on x-ray phase analysis, scanning electron microscope images, and energy-dispersive analysis. The proportion of the MAX-phase increased from 26 to 63 wt.% as the annealing temperature of the material increased.