Zirconia production method and preparation process

Zirconia production method

1. Zirconium oxychloride pyrolysis method: zircon and caustic soda are melted at 650℃, hot water is leached out of the melt, and silicon is separated from sodium zirconate in the form of sodium silicate. After treatment with sulfuric acid, a zirconium sulfate solution is obtained. After further removing impurities, ammonia water is added to precipitate zirconium hydroxide. Add hydrochloric acid to dissolve zirconium hydroxide to obtain zirconium oxychloride. After evaporation, concentration, cooling, crystallization, pulverization, and roasting, zirconium dioxide is obtained as a finished product; in addition, zirconium compounds that are easy to be purified can be thermally decomposed or oxidized to prepare high purity Zirconia.

2. Colloidal method: In the zirconia solution, silica sol is added to form a colloidal solution, which is shaped by spraying and drawing methods, and sintered into fibers after drying.

3. Extrusion method: The zirconia sol or zirconia particles and thickener are made into blanks, and the blanks are extruded from the model port and into filaments by hydraulic pressure or the propelling action of the screw reamer, and then sintered and solidified. Fibrous. The fiber produced by this method is thicker and the strength of the fiber is also low.

4. Dipping method: first soak the viscose filament or the entire fabric in the zirconium hydroxide solution for a long time to swell the viscose fiber, and then obtain the zirconia fiber with a certain tensile strength after pyrolysis and calcining.

5. Hydrolysis method: use zirconium oxychloride as raw material to hydrolyze to prepare high-purity ultra-fine zirconium dioxide, hydrolyze the 0.2-0.3 mol/L high-purity zirconium oxychloride solution with deionized water, and boil the zirconium oxychloride solution for a long time , The hydrogen chloride generated by the hydrolysis is continuously evaporated and removed, and the hydrolysis reaction is carried out at boiling for more than 50 h, and then filtered, washed with deionized water, dried, calcined and crushed to obtain the product.

6. High-temperature hydrolysis: spray 1 mol/L of high-purity zirconium oxychloride solution into a decomposition furnace at a temperature of 1000 ℃, and the tiny droplets of zirconium oxychloride will first evaporate water and then hydrolyze to produce zirconium dioxide. The decomposed zirconium dioxide is collected by a cyclone separator, and then pickled, washed with water, and dried to obtain the product.

7. Sol-gel method: add alcohol and water to zirconium alcohol [ZrO(C3H7)4], then add catalyst, after thorough mixing, start to decompose, place it to gel and become a viscous liquid, choose appropriate viscosity, Dry and then heat to 500~1000 ℃, high temperature fiberization and firing to obtain the product.

8. Alkoxide hydrolysis: using zirconium tetrachloride, ammonia and propanol as raw materials to prepare high-purity ultra-fine zirconium dioxide, and reacting high-purity zirconium tetrachloride with propanol and ammonia at 5 ℃ to obtain zirconium alcohol in the presence of benzene solvent The salt is separated by filtration to remove ammonium chloride, and then hydrolyzed by adding water to precipitate and filter. The product is dried, calcined and crushed at no less than 100 ℃. The hydrolysis conditions directly affect the particle size, shape and aggregation status of the product. This method can produce ZrO2 with uniform particle size and shape and a single structure.

9. The zirconium oxychloride (ZrCl2O·8H2O) is recrystallized with hydrochloric acid or methanol and calcined at a high temperature to obtain a finished product.

10. Distill and purify the zirconium tetraalkoxide, and the vapor is decomposed at 350~500 ℃ to obtain the finished product.

11. Distill and purify zirconium tetrachloride, and react its vapor with excess oxygen at 1200°C to obtain zirconium dioxide.

Zirconia preparation process

Most of the stabilized zirconia used in industrial refractories are prepared by electrofusion. In the zircon fusion process, carbon and stabilizer calcium oxide are added. While removing silicon, the zirconia and calcium oxide react to form a solid solution, which is then crushed and sized to obtain stable zirconia. The stable and partially stabilized zirconia used in fine ceramics is generally prepared by wet methods. At present, the most mature and commonly used method is the neutralization precipitation method, and its preparation process is shown in the figure. Dissolve the purified zirconium oxychloride with pure water, filter to remove insolubles, adjust the zirconium concentration in the solution, and add the required amount of yttrium chloride solution (or chloride solution of other rare earth metals or alkaline earth metals), and then add ammonia Neutralize precipitation. After washing the precipitate with hot water, it is filtered, dried and calcined. The calcined product can be crushed to obtain ultra-fine stable zirconia powder.

Partially stabilized zirconia is prepared by controlling the amount of stabilizer added to make it insufficient to achieve complete stability. Partially stabilized zirconia has high strength and thermal shock resistance, and has a wide range of uses in structural ceramics. [1] 

flow chart

The picture below shows the process of preparing zirconium dioxide

Overview of Zirconia ZrO2 Powder

Zirconium dioxide (ZrO2) is sometimes called zirconia (not to be confused with zircon), and is the white crystalline oxide of zirconium. Its most naturally occurring form has a monoclinic crystal structure and is the mineral bentonite. Dopant stabilized cubic zirconia, cubic zirconia, synthetic various colors, used as gem and diamond simulants.

Zirconia is not chemically reactive. Slowly corroded by concentrated hydrofluoric acid and sulfuric acid. When heated with carbon, it converts to zirconium carbide. When heated with carbon in chlorine, it is converted to zirconium tetrachloride.

Zirconia is one of the most studied ceramic materials. ZrO2 adopts a monoclinic crystal structure at room temperature and transforms into tetragonal and cubic crystals at higher temperatures. The volume change caused by the structure of the four-direction monoclinic to cubic transformation will generate greater stress, which will cause it to crack when cooled at high temperatures.

Three phases are known: monoclinic phase below 1170°C; tetragonal phase between 1170°C and 2370°C; cubic phase above 2370°C. Generally, the trend is to have higher symmetry at higher temperatures. A small part of calcium or yttrium oxide is stabilized in the cubic phase. Rare mineral Tazheranite (Zr, Ti, Ca) O2 is a cube. Unlike TiO2, which has six-coordinated titanium in all phases, monoclinic zirconia is composed of seven-coordinated zirconium centers. This difference is due to the larger size of zirconium atoms relative to titanium atoms.

The band gap of ZrO2 depends on the phase (cubic, tetragonal, monoclinic or amorphous) and preparation method, and the typical estimate is 5-7 eV. A special case of zirconia is tetragonal zirconia polycrystalline or TZP, which means polycrystalline zirconia consisting of only a metastable tetragonal phase.

Zirconia ZrO2 powder characteristics

The chemical properties of zirconium dioxide are inert, with high melting point, high resistivity, high refractive index, low thermal expansion coefficient and other characteristics. It is an important high temperature resistant material, ceramic insulating material, ceramic sunscreen material, and the main source of artificial diamonds. part. raw material. The band gap is about 5-7eV.

Application of Zirconium Oxide ZrO2 Powder

Zirconia ZrO2 powder is used in metal zirconium and zirconium compounds, refractory bricks and crucibles, high-frequency ceramics, abrasives, ceramic pigments and zirconates. It is mainly used in piezoelectric ceramic products, daily ceramics, refractory materials and precious metal smelting zirconium bricks, Zirconium tube, crucible, etc.

refractory

Zirconia fiber is a polycrystalline refractory fiber material. Due to the high temperature resistance of ZrO2 material such as high melting point and non-oxidation, the use temperature of ZrO2 fiber is higher than other refractory fibers, such as alumina fiber, mullite fiber, aluminum silicate fiber and so on. Zirconia fiber is used for a long time in an ultra-high temperature oxidizing atmosphere above 1500°C, the highest temperature is as high as 2200°C, and even 2500°C can still maintain a complete fiber shape, which is the highest current theme. Fiber material.

gas turbine

Plasma sprayed zirconia thermal barrier coatings have made great progress in the application of air and industrial gas turbines, and have been applied to the turbine part of gas turbines to a certain extent. Since the coating can reduce the temperature of the air-cooled high-temperature component to 50-200°C, the durability of the high-temperature component can significantly improve the durability of the high-temperature component, or the temperature of the gas can be increased. Lower the temperature or lower the temperature required to maintain high-temperature components. Changes to improve the efficiency of the engine.

Ceramic material

Zirconia is used in the kiln industry due to its high refractive index, high melting point and strong corrosion resistance. Piezoelectric ceramic products include filters, speakers and ultrasonic water detectors. There are also daily ceramics (industrial ceramic glazes), zircon bricks and zirconium tubes used for precious metal smelting. Nano-scale zirconia can also be used as a polishing agent, abrasive, piezoelectric ceramics, precision ceramics, ceramic glazes and high-temperature pigment matrix materials.

treatment

In addition, zirconia can also be used to make incandescent gas masks, enamel, white glass and refractory crucibles. X-ray photography. Abrasive. Used to make light source lamps, thick film circuit capacitor materials, and piezoelectric crystal transducer formulas in infrared spectrometers.

Zirconia ZrO2 powder price

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