Zirconia hollow sphere products and hollow sphere bricks are made of zirconia hollow spheres by electrofusion method. Binder is added to the zirconia hollow spheres, and zirconia hollow sphere products are made by molding and firing.

　　Zirconia hollow sphere product is a kind of ultra-high temperature energy-saving lightweight special refractory material that can be used at 1800 ~ 2400 ℃. Because the thermal conductivity of this product is as low as 0.3~0.4W/ (m.Kr, it can not only be used as a heat insulating furnace lining material on various ultra-high temperature electric furnaces, molybdenum wire furnaces and tungsten rod furnaces, but also can be directly used as furnace lining materials for the working layer. .

　　(一) Raw materials and their preparation

　　Use chemically pure zirconia and calcium oxide (can be replaced by calcite, light calcium carbonate, calcium hydroxide) as raw materials. Zirconia:Calcium oxide=%:4. Mix and finely grind for 6h in an iron-free ball mill.

　　(二) Blowing and properties of zirconia hollow spheres

　　The mixed and finely ground raw materials are blown into zirconia hollow spheres in a three-phase electric arc furnace, and the operation method is the same as that of alumina hollow spheres. Due to the high melting point of zirconia and the high viscosity of the solution, graphite blocks less than 10mm should be added in each smelting. This can increase the solution temperature, thereby improving the quality and yield of hollow spheres. Physical and chemical properties of zirconia hollow spheres: chemical composition: ZrO2 96.1%, CaO 3.78%, Fe2O3 0• 04%, MgO 0.07%, Al2O3 0.17%. Phase composition: cubic crystal 70% ~ 80% monoclinic crystal 20% ~ 30%.

　　(三)Zirconia hollow sphere products

　　(1)ingredients. The general ingredients of zirconia hollow spheres are the use of particle size mixed balls (less than 5mm), and particle size classification balls can also be used. The binding agent uses phosphoric acid (60%) or sodium tetraborate aqueous solution (density is 1.25g/cm3). Fused zirconia powder, less than 320 mesh.

　　(2) Mixing, molding. After mixing, the wood mold is used to form, and the model does not add a ruler. Formed on a vibratory press.

　　(3) Dried and fired. The green body is fired at 1800° C. for 10 h after drying, and the total firing time is about 45 to 55 h.

　　(四) Production and Application of Zirconia Hollow Ball Insulation Cover

　　(1)Granular composition. The particle size composition of zirconia hollow spheres: 2～1mm30%, 1～0.5mm20%, less than 0.5mm10%.

　　(2) Ingredients, molding. Add 40% of fused zirconia powder (300 mesh), add an appropriate amount of binder and mix, pressurize 50MPa in a steel mold to form.

　　(3) Dried and fired. After drying, it is fired at 1800℃ for 4~6h.

　　(4) Physical and chemical properties. The physical and chemical properties of the zirconia hollow sphere insulation cover and their comparison are shown in Table 6-44. On TDK single crystal furnace, the operating temperature is 1900℃.