Springer Science and Business Media LLC

A study was made of the effect of certain additives on the linear shrinkage of heat-insulating glass-fiber refractories at 1100–1300°C. It is shown that an addition of a mixture of alumina and magnesia, and also finally milled fused quartz, reduces the linear shrinkage of the goods after firing at temperatures up to 1300°C, and in this case the thermal conductivity of the goods is hardly impaired. We developed optimum compositions for these refractories, enabling us to reduce the linear shrinkage to 1% in the 1100–1300°C range. It is shown that a reduction in the linear shrinkage of the tiles with the addition of alumina and magnesia occurs on account of the overall increase in the volume during the synthesis of magnesia spinel, mullite in the bond, and α-cristobalite. The linear shrinkage of fibrous specimens with fused quartz is reduced on account of the increase in the volume during the cristobalitization of the fused quartz. The Bogdanovich factory made a trial batch of fibrous articles with a low shrinkage during heating which were established in the working layer of a soaking pit at the Hammer and Sickle Steel Plant.

Information is provided about the thermal conductivity of highly porous refractory specimens prepared using kaolin, clay, combustible, sintering additives, and also foam. Data for the properties of samples of lightweight refractories prepared by different methods are analyzed. The emphasis is on combination of specimen heat insulation and strength properties The thermal conductivity achieved for foam samples is 0.37 W/(m·K) at 650°C in combination with satisfactory compressive strength of 3.8 MPa.

The physical chemistry of multistep hardening of phosphate bonding materials is considered. The function of hydrogen bonds in the phosphate hardening mechanism and their effect on the adhesive properties of phosphate bonding materials are discussed. Techniques for enhancing the adhesive properties of phosphate binders using powdered oxides, hydroxides, and salts and their involvement in acid-base reactions are considered. Bonding materials for nonfired refractories, corrosion-resistance coatings and mortars, and areas for their potential applications are proposed.

Calculation of the temperature fields and stressed and strained conditions of samples in thermal loading made it possible to establish three characteristic zones of failure and the moments of the stresses (deformations) reaching the maximum values in these zones. Visual and instrument observations of the occurrence and development of cracks confirmed the established failure mechanism. The dynamics of thermal failure of refractories recorded by the acoustic-emission method agrees with the results of calculation of the temperature fields and the stressed and deformed condition and with the data of microstructural analysis. The outlook for continuation of investigations on evaluation of the crack resistance of refractories of various compositions by the acoustic-emission method was shown.

Properties of electrodes graphitized by the traditional Acheson method and the innovative method of Castner are compared. The higher heating rate in the Castner graphitization technique causes formation of microcracks in the electrode body, which results in a decrease of density and mechanical strength of the graphitized electrodes in comparison to those in the Acheson method. The results of industrial tests attest to a higher thermal strength of Castner-graphitized electrodes.

Six variants of direct and reverse coprecipitation of a mixture of salts by an aqueous solution of ammonia or an ammonia buffer solution with pH 9.5 are considered to optimize the technological scheme for the synthesis of zirconium dioxide nanopowders stabilized with 2.5 mol.% yttrium oxide. The influence of the storage time of the mixture of salt solutions before precipitation on the phase and chemical composition, apparent density, and open porosity of sintered specimens was investigated. The best results were obtained using reverse precipitation with an ammonia buffer as precipitant.