1. Zirconia ceramic manufacturing
When preparing stable ZrO2 powder, electrofusion synthesis (about 1000 ℃) and high temperature synthesis (1600 ~ 1650 ℃ for 4h) can be used. The reaction of ZrO2 synthesized by electrofusion is complete, and some or all of it is cubic solid solution. There is a certain amount of monoclinic ZrO2 in ZrO2 synthesized at high temperature.
The stabilization process can be summarized as follows: mix and grind the raw materials with purity > 96% and stabilizer in ball milling tank for 8 ~ 24h, add a small amount of binder, and press them into green blocks under the pressure of 60 ~ 100MPa. The purpose of blank pressing is to make close contact between ZrO2 powder and stabilizer particles, which is conducive to solid solution reaction. After that, the compact is heated at 1450 ~ 1800 ℃ for 4 ~ 6h for solid solution stabilization, and finally the stabilized sintered block is crushed to various particle sizes. The sintered compact stabilized above 1800 ℃ is not easy to grind.
ZrO2 Ceramics can be formed by grouting method or dry pressing method. During grouting molding, a small amount of Arabic gum (concentration of 10%) and distilled water of about 20% can be added to ZrO2 fine material to form a slurry with good grouting performance. Transparent ceramics can be prepared by hot pressing. If there are many coarse particles in the powder, the volume shrinkage is small, and if there are many fine particles, the density of the product is high. The firing temperature is 1650 ~ 1800 ℃, and the heat preservation is 2 ~ 4H.
2. Properties and application of Zr02 ceramics
(1) High hardness. Mohs hard 6.5, so it can be made into cold forming tools, shaping dies, wire drawing dies, cutting tools, etc.
ceramic cutter tool
(2) High strength and good toughness. The flexural strength can reach 2100mpa at room temperature and 1190mpa at 1000 ℃. The bending strength of the best toughened ceramics at room temperature can reach 2000mPa and KIC can reach more than 9 ~ 12MPa · M1 / 2. Therefore, it can be used to manufacture engine components, such as push rod, connecting rod, bearing, cylinder liner, piston cap, etc.
(3) Semiconductor. ZrO2 has semi conductivity at high temperature. Pure ZrO2 is a good insulator with a specific resistance of 1013 Ω ▪ Cm after adding the stabilizer, because the valence of the stabilizer is different from that of Zr4, oxygen vacancies are generated in ZrO2 after replacement to maintain the electrical neutrality of the crystal. As a charged defect, oxygen ion vacancy increases the conductivity of ZrO2 at high temperature. Because ZrO2 has this characteristic, it is often used to manufacture high-temperature heating elements. ZrO2 heating element can be used in air with the maximum temperature of 2100 ~ 2200 ℃.
(4) Corrosion resistance. ZrO2 is very stable in oxidizing atmosphere and in reducing atmosphere. Zirconia is a weakly acidic oxide, which can resist the erosion of acidic or neutral slag (but will be eroded by alkaline slag). Therefore, it can be used as special refractory, casting port and crucible for smelting platinum, palladium, rhodium and other metals. Zirconia is not wetted with molten iron or steel, so it can be used as the lining of steel bucket and flow steel tank, and as nozzle brick in continuous cast steel.
(5) Sensitive characteristics. After stabilization, there is an oxygen vacancy, so it can be used as a gas sensor. Zirconia solid electrolyte has the characteristics of transmitting oxygen ions under certain conditions. It can be made into solid electrolyte diaphragm of high temperature fuel cell, probe for measuring oxygen in liquid steel, etc.