Zirconium dioxide is the main oxide of zirconium, usually under the conditions of white odorless and odorless crystals, insoluble in water, hydrochloric acid and dilute sulfuric acid. Generally often contain a small amount of hafnium dioxide. Chemical properties are inactive, and has a high melting point, high resistivity, high refractive index and low thermal expansion coefficient of the nature, making it an important high temperature materials, ceramic insulation materials and ceramic opacifier, artificial drilling is the main raw material. The band gap is about 5-7 eV.
1, obtained by burning zirconia hydrate or volatile zirconylate zirconium oxide obtained as a white powder, insoluble in water
ZrO2 xH2O ZrO2 + xH2O;
2, through the mild burning of zirconium dioxide, relatively easy to be dissolved in inorganic acid
ZrO2 + 4H + = Zr4 ++ 2H2
Strong heat burning of the obtained zirconia is only soluble in concentrated sulfuric acid and hydrofluoric acid, after melting and recrystallization of zirconia only with hydrofluoric acid;
3, zirconium dioxide is a kind of amphoteric oxide, and alkali eutectic can form zirconate, but the zirconate water easily hydrolyzed to ZrO2 · xH2O and precipitation.
ZrO2 + 2NaOH = Na2ZrO3 + H2O
Na.ZrO3 + H2O = ZrO2 + NaOH;
4, zirconium and carbon and chlorine gas high temperature reaction, or with carbon tetrachloride reaction, the formation of zirconium tetrachloride and zirconium dichloride, hydrolysis and get zirconium dioxide
3ZrO2 + 2C + 4Cl2 = ZrCl4 + 2CO2 + 2ZrOCl2;
5, it is in the arc with carbon generated zirconium carbide
ZrO2 + 2C = CO2 + ZrC;
6, into the oblique zircon type ZrO2 is yellow or brown monochromatic crystal insoluble in water, hydrochloric acid and dilute sulfuric acid, soluble in hot concentrated hydrofluoric acid, nitric acid and sulfuric acid. Alkalization with the base to produce zirconates. Chemical properties are very stable. For the system of high-grade ceramics, enamel, refractory materials. Can be zirconia and soda ash eutectic, with water leaching sodium zirconate, and hydrochloric acid to zirconium dichloride, and then calcined in the system.
Metal zirconium and its compounds
For the production of zirconium and zirconium compounds, made of refractory bricks and crucible, high-frequency ceramics, grinding materials, ceramic pigments and zirconates are mainly used for piezoelectric ceramic products, ceramics for daily use, refractory and precious metal smelting Zirconium brick, zirconium tube, crucible and so on. Also used in the production of steel and non-ferrous metals, optical glass and zirconia fiber. Also used for ceramic pigments, electrostatic coatings and paint. For epoxy resin can increase the corrosion of heat-resistant brine.
Zirconia fiber is a polycrystalline refractory fiber material. Due to the high melting point, non-oxidation and other high temperature characteristics of the ZrO2 material itself, the ZrO2 fibers have higher temperatures than other refractory fiber varieties such as alumina fibers, mullite fibers, and aluminum silicate fibers. Zirconium oxide fiber in 1500 ℃ above the high temperature oxidation atmosphere long-term use, the maximum temperature of up to 2200 ℃, even to 2500 ℃ can still maintain a complete fiber shape, and high temperature chemical stability, corrosion resistance, oxidation, Non-volatile, non-polluting, is currently the world's top of a refractory fiber material. The acid corrosion resistance of ZrO2 is much stronger than that of SiO2 and Al2O3. Insoluble in water, soluble in sulfuric acid and hydrofluoric acid; slightly soluble in hydrochloric acid and nitric acid. Can be used with the base eutectic zirconium salt
The application of plasma sprayed zirconia thermal barrier coatings in aerospace and industrial gas turbines has made great progress and has been used in turbines of gas turbines to a certain extent. Since this coating can reduce the temperature of the air-cooled high-temperature components by 50 to 200C, it is possible to remarkably improve the durability of the high-temperature parts or to increase the temperature of the gas or to reduce the amount of the cooling gas and to keep the temperature Change, thus improving the efficiency of the engine.
Because zirconia's refractive index, high melting point, corrosion resistance, it is used for kiln raw materials. Piezoelectric ceramic products are filters, loudspeaker ultrasonic underwater acoustic detectors. There are daily ceramics (industrial ceramic glaze), precious metal smelting with zirconium brick and zirconium tube. Nano-sized zirconia can also be used as a matrix material for polishing agents, abrasive grains, piezoelectric ceramics, precision ceramics, ceramic glazes and high temperature pigments.
In addition zirconia can be used for white hot gas shade, enamel, white glass, refractory crucible, etc. manufacturing. X - ray photography. Grinding material. Used together with yttrium to make light source lamps, thick film circuit capacitance materials, piezoelectric crystal transducer recipes in infrared spectrometers