Advancing the manufacturing process of zirconia vessels for installations for nickel evaporation

The effect of activating additives of H₃PO₄ and zirconium oxychloride and a sintering additive of A1₂O₃ on the properties of zirconia concrete mixtures containing colloidal suspensions and vibroshaped articles on their base is described. The optimum amounts of the additives and the principal physicomechanical properties of the articles are determined. The effect of the heat treatment temperature of zirconia vibroshaped specimens and articles is studied and the optimum firing temperature is established to be no lower than 1400°C. A pilot batch of large vessels for installations for nickel evaporation has been manufactured and tested.     

Metal-modified zirconia refractories

The effect of Ti, Mo, and Ni additives on the properties of ceramics based on monoclinic zirconia was studied. The samples were prepared from fused or sintered zirconia, fired at 1450°C in a vacuum furnace. The densest and strongest ceramics were obtained from fused zirconia modified by adding 10 or 15% Ti, Mo, or Ni. The parameters of the refractories were as follows: open porosity, 17.6–19.9%, compressive strength, 195 MPa (10% Ni additive), 270–280 MPa (Mo additive), 326–485 MPa (Ti additive). Translated from Ogneupory i Tekhnicheskaya Keramika, No. 4, pp. 31–33, April, 1997.     

Zirconia-base ceramics for drawing tools

Results of an investigation and fabrication of a ceramic drawing tool based on zirconia partially stabilized by yttrium oxide and the combined stabilizing additives Y₂O₃ + CeO₂ and Y₂O₃ + MgO, which increase the heat resistance of the materials, are presented. The developed ceramics based on ZrO₂ and stabilized by 2% Y₂O₃ by chemical coprecipitation with a CeO₂ additive has the following parameters: an open porosity of 2.1%, an apparent density of 5.60 g/cm³, an ultimate bending strength of 450 MPa. In a ceramic based on ZrO₂ and stabilized by 5% Y₂O₃ by the method of ceramic sintering the corresponding parameters are 3%, 5.62 g/cm³, and 271 MPa. An experimental batch of zirconia drawing matrices has been produced and tested in tube drawing. Mandrel-free drawing of tubes made of stainless steel of grades 08Kh18N10, 12Kh18N10T, and éI702, copper of grade M1, and titanium alloy of grade VT1-0 and long-mandrel drawing of steel of grade 12Kh18N10T occurred stably and without sticking of the metal to the die or any damage to the tubes or dies. Translated from Ogneupory i Tekhnicheskaya Keramika, No. 5, pp. 14–20, May, 1996.     

Parameters of corundum spheres for packing high-temperature air heaters

Conclusions Parameters have been defined that need to be considered in choosing compositions and manufacturing techniques for spheres for packing high-temperature heaters. Tests have been made on the failure load, temperature for the start of deformation under load, creep strain under load, and strength reduction on thermal shock for these corundum spheres.The parameters have been determined for spheres with various compositions and made in various ways; they can be related to the porosity and crystal size.The creep varies from 0.6 to 5.2% at loads of 30 and 50 N in 10 h between 1300 and 1600°C. Shrinkage occurs on heating above the firing temperature, which attains 2.8% at 1950°C. The strength reduction after thermal shock is about 0.1%/°C.Defects also affect the deformability and strength.Translated from Ogneupory, No. 3, pp. 11–15, March, 1989.     

Influence of the properties of refractory powders on their granulation and the properties of the granules

Conclusions A study was made of the properties of aluminosilicate powders of various compositions and their influence on the densification during granulation.We established relationships between the porosity and density of the granules with various concentrations of Al₂O₃ with bulk densities and angles of natural slope. It is shown that to obtain dense and strong green articles and fired aluminosilicate granules with the minimum shrinkage, it is necessary to use bodies with a high bulk density and low internal friction, which is attained for alumina by using batches with the maximum concentration of -Al₂O₃ and grains with a pore-free structure, and for aluminosilicate refractories — an increased content of Al₂O₃ within the limits of each type of article.Translated from Ogneupory, No. 8, pp. 6–10, August, 1985.     

Granulation of particulate oxide materials

Conclusions The improved technology for granulating particulate oxide materials using the grains of inoculator seeds makes it possible to reduce the period of granulation and to increase the yield of the final granules. The waste products obtained during production of flaky (platelike) corundum can be used as the inoculator grains. In order to obtain granules having an ellipticity not exceeding 0.5–0.7 mm, the optimum size of the inoculator grains is 1–2 mm.The inoculator grains obtained from the low-fired (undersintered) material has advantages over the densely sintered materials from the standpoint of improved internal structure of the granules. We established the optimum quantity of the inoculator grains for obtaining granules measuring (20±3) mm in diameter using a granulator having a diameter of 1000 mm with minimum irretrievable waste products during the initial period of granulation.We studied the growth kinetics during seedless granulation and during granulation with an inoculator. It was shown that densification of the granules occurs during granulation. We determined the main physical and mechanical properties of the granules obtained by granulating on the inoculator grains and by seedless granulation and established the optimum composition of the binding solution (binder) incorporating a phosphate-containing component as strengthening agent.Translated from Ogneupory, No. 6, pp. 10–13, June, 1989