Properties of refractories with ZrO2 and SIO2 added in different concentrations and by different means

Conclusions It has been established that the addition to corundum of 15–20% of a stoichiometric mixture of baddeleyite and quartz sand in both an unmilled and milled form increases by almost 1.5-fold (in relation to number of heat changes) the thermal-shock resistance of the refractory by comparison with a refractory containing 7.5–20% zircon.The addition of Novoselitsk kaolin is not effective. It has a bad effect on the characteristics of the corundum-zircon refractories.Translated from Ogneupory, No. 5, pp. 40–43, May, 1981.     

Manufacture and properties of Hafnium dioxide products

Refractories and Industrial Ceramics - The technology was developed for the manufacture of products from hafnium dioxide stabilized with 10 and 50 mole % Y2O3 in the form of slipcastings in gypsum...     

Effect of additives on the thermal-shock resistance of corundum-zircon refractories

Conclusions It is established that the addition of 0.1–1.0% of Bi₂O₃ increases 2–7 and 1.5-fold, respectively, the resistance of a material to the nucleation and spread of destructive cracks; CoO₂ in amounts up to 0.1% has virtually no effect on the total thermal-shock resistance but increases threefold the resistance to the nucleation of destructive cracks.The addition of SnO₂ produces a slight decrease in both the number of heat cycles withstood before the appearance of the first visible crack and in the total thermal-shock resistance of the specimens before total destruction.It is established that the favorable effect of the Bi₂O₃ additive can be reduced to the fact that it melts, forming a thin film of melt on the surface of the corundum and zircon grains; this facilitates the formation of denser structures and, after evaporation, the formation of fine discontinuous microcracks.Translated from Ogneupory, No. 6, pp. 39–42, June, 1981.     

Thermophysical and elastomechanical properties of grainy corundum-zircon refractories and the effect of these properties on the thermal-shock resistance

Conclusions The thermophysical properties (l/l ₀ and ) and the elastomechanlcal properties (E, G, _bend) of corundum-zircon specimens in the 20–1200°C interval with various concentrations and grain sizes of zircon and different grain sizes and types of the corundum and zircon components in the grain and bondings have been investigated. It is established that in particular temperature regions there is a connection between the criteria R and R calculated from the values of the properties and the number of heat changes before the onset of primary cracking and total destruction of the specimens.Translated from Ogneupory, No. 1, pp. 56–60, January, 1980.     

Some properties of fine-grained mixtures of ZrSiO4-ZrO2

Conclusions The effect of additions of ZrO₂ in monoclinic and cubic modifications and also of Zr(OH)₄ on the swelling, thermal-shock resistance, and glass-resistance of high-density, zircon refractories has been studied.It is shown that the most effective addition for lowering the additional growth of the refractory almost fivefold was a mixture consisting of 9.5% monoclinic ZrO₂ and 0.5% Zr(OH)₄. This additive also increases significantly the thermal-shock resistance of the zircon refractories and the glass resistance as a result of the lower decomposition of ZrSiO₄, and the higher concentration of ZrO₂ in the contact zone. The density and electrical resistivity of the refractory is maintained at a high level.Translated from Ogneupory, No. 8, pp. 48–53, August, 1982.