Zirconia bricks are refractory products produced with zirconia as the main raw material. The manufacturing method mainly includes two kinds of firing method and fusion casting method. There are three crystal forms of zirconia: monoclinic, tetragonal and cubic. When zirconium oxide is heated to about 1100°C, the crystal form changes from monoclinic to tetragonal, accompanied by a 7% volume shrinkage, and vice versa. The tetragonal zirconia will appear cubic crystal form above 2300℃. The densities of the three crystal forms were 5.68g/cm3 (monoclinic), 6.10g/cm3 (tetragonal), and 6.27g/cm3 (cubic). Zirconia is resistant to high temperature, chemical corrosion, and has a large coefficient of thermal expansion. Stable zirconia has become an important material that cannot be ignored in the refractory industry and the field of special ceramics.
Mainly divided into dense zirconia bricks and standard zirconia bricks.
Dense zirconia bricks are formed by isostatic pressing. The technical indicators are ZrO2>65%, apparent porosity<2.0%, bulk density about 4.25g/cm3, and corrosion in E glass when the temperature exceeds 1370℃. It is used in the bottom of the melting part of the E glass unit kiln where the temperature of the molten glass is slightly lower, the transition channel, the bottom of the forming channel, the forming channel flow trough and the slat bracket, etc. In addition, dense zirconia bricks are also used as backing bricks for dense chrome bricks.
The standard zirconium brick has a ZrO2 content of about 66% and a bulk density of 3.7g/cm3, which has good thermal stability and peel resistance. It is used in the breast wall and back wall of the feeding port area where powder erosion is more serious, the breast wall of the furnace observation hole brick and the passage flame space, the roof brick and the burner brick.
The production process of zirconia bricks includes: raw material pretreatment, powder milling, molding, sintering and other processes. Zirconium oxide in the oxide product system has many excellent characteristics, such as high melting point (2700℃), high structural strength at high temperature (200kPa at 2000℃, and can be maintained for 0.5~1h before deformation), good chemical stability, regardless of acid and alkali Or glass melt has high chemical inertness, is not easy to be wetted by liquid metal, high temperature vapor pressure and decomposition pressure are low, and has lower volatility than Al2O3 and MgO.
Industry application:
Zirconia bricks are used for high-temperature furnace linings above 2000°C. Zirconia rods can be used as heating elements for high-temperature furnaces at 2000-2200°C in an oxidizing atmosphere. The zirconia solid electrolyte can be used as an oxygen probe for the rapid determination of oxygen content in molten steel, molten copper, and furnace gas, and as a diaphragm for high-temperature fuel cells. Using the martensitic phase transformation of zirconia, zirconia is introduced into oxide and non-oxide ceramics, which can be used as toughening agents to improve the brittleness of ceramics, such as zirconia toughened alumina and silicon nitride.
With the development of modern science and technology and testing technology, mankind’s understanding of high-temperature refractory zirconia products will surely be further deepened, and zirconia products will surely appear with a new look. In recent years, some domestic companies have been able to produce high-quality products. Ultra-fine zirconia powder, and most of the products are exported, but the powder preparation is still at a relatively backward level. The future development should be in the direction of ultra-fine and high-purity, and the manufacturing of products should be towards new functions and new The direction of the application field is developing, and the application field of zirconia products is continuously expanded.
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