Refractories and Industrial Ceramics最新文献

Ceramic fibers of refractory oxides used as the main components of heat-resistant refractory materials are discussed. External defects affect the mechanical characteristics of refractory oxide ceramic fibers. Optical and electron microscopy were used to investigate the surface morphology of ceramic fibers, to classify the defects, to establish the causes for their appearance, and to propose methods for eliminating them.

Acid-resistant material is obtained from metallurgy wastes, i.e., the clay part of gravity tails of zircon-ilmenite ores (CZI) used as a clay binder, and ferrochromic aluminothermic slag (FAS), used as a repellent, without using natural traditional materials. Introduction of FAS into the ceramic compositions was found to contribute to the formation of highly refractory minerals (corundum, magnesia spinel, chromium oxide, bonite, and mayenite), which improved the chemical and physicomechanical indices of the acid-resistant materials at a firing temperature of 1300°C.

With combined metal blowing in an oxygen converter, the durability of the purge tuyeres when inert gases are supplied through the converter bottom is less than the durability of the converter lining because of the advanced wear of the tuyeres in relation to the bottom lining and the metallization of the capillaries/channels on the tuyeres with a slag–metal emulsion. To increase the performance of tuyeres, their placement in areas with the least wear of the lining and the avoidance of contact with the slag–metal emulsion are recommended.

Cermet materials based on titanium carbide and nichrome that were prepared by SHS extrusion were annealed in an oxidizing atmosphere at high temperatures of 800, 900, 950, and 1000°C for 10 h. Dependences of weight gain and oxidation rate of the oxidized samples on temperature and annealing time were plotted. It was found using x-ray phase analysis and scanning electron microscopy that the carbide phases did not change stoichiometry, a new CrNi₃ phase was detected, and oxide films (TiO₂ and Cr₂O) formed on the sample surfaces. TiC carbide grains grew from 2.79 to 3.4 μm as the annealing temperature increased.

Results of studying the process of fine milling of α-Al₂O₃ in the presence of polyethylene glycol (PEG) and an antistatic composition are presented. It is shown that the main reason for agglomeration of fine particles is the effect of appearance of an electrostatic surface charge. Introduction of PEG prevents appearance of a “pseudo-viscous milling medium”, removing the excess electrostatic charge at the surface of newly formed ultrafine particles, and also intensifies the wear process of primary alpha-alumina crystals. The antistatic composition successfully neutralizes a surface electrical charge, but does not exhibit a milling intensifier effect.

The influence of added zirconium dioxide micropowder partially stabilized by yttrium on the high-temperature resistance of fired periclase refractories and on some physical and physicomechanical properties was studied. The structures of high-purity synthetic periclase and zirconium dioxide micropowder were examined using microscopy. A possible mechanism of interaction of the additive with impurities contained in the periclase was determined. The zirconium dioxide micropowder had a substantial influence on the high-temperature properties of the refractory.

Results of studies determining the iron-bearing phase of trachybasalt porphyrite from the Karabulak site of the Gavasay deposit of Uzbekistan using Mossbauer spectroscopy and its suitability for obtaining basalt fiber are presented. Continuous basalt fibers for heat-insulating materials could be obtained from this igneous rock without corrective additives.

The possibility of obtaining low-cement low-carbon periclase concretes with various ultrafine carbonaceous components is studied. It is shown that it is possible to obtain periclase-carbon concrete containing up to 1 wt.% ground waste from production of high-modulus graphite fiber. With an increase in carbon waste content from 1 to 5%, the water requirement of the mixture increases (from 6.25 to 10%), which leads to a reduction in concrete indices. It is established that slag resistance of the developed periclase-carbon objects is comparable with that of ordinary periclase-carbon products.

The main aspects of obtaining an artificial ceramic binder (ACB) based on the original (quarry) and heat-treated diatomite are considered. The process of obtaining ACB is studied, and the main rheological properties and physicomechanical characteristics of specimens are analyzed. It is established that ACB based upon quarry diatomite exhibits thixotropic rheological behavior, and ACB based upon preheat-treated diatomite pertains to a thixotropic-dilatant type. Use of this technology for preparing a binder makes it possible to reduce molding moisture content in manufacture of various diatomite products and to improve their quality while reducing production costs compared with similar objects prepared by traditional technology.

The effects of TiB₂ and BN coatings on the thermal and stress–strain state of two systems of Si₃N₄–TiC ceramic surface layers under the action of heat flow are investigated. An analysis of results from numerical experiments showed that the TiB₂ coating has a more favorable effect on the stress state of ceramic surface layer; the BN coating, on the stress state of the boundary with the ceramic.