What's zirconium oxide?

The chemical formula of zirconium dioxide is ZrO2, which is the main oxide of zirconium. It is usually a white, odorless and tasteless crystal, which is difficult to bathe in water, hydrochloric acid and dilute sulfuric acid. The chemical properties are inactive, and it has the properties of high melting point, high resistivity, high refractive index and low thermal expansion coefficient, making it an important high temperature resistant material, ceramic insulating material and ceramic opacifying agent, and also the main raw material of artificial diamonds. 

Properties of Zirconia

1. High melting point

The melting point of zirconia is 2715°C. The high melting point and chemical inertness make zirconia a good refractory material.

2. High hardness and good wear resistance

Zirconia ceramics have greater hardness and better wear resistance. From the specific data, the Mohs hardness of zirconia ceramics is about 8.5, which is very close to the Mohs hardness of sapphire 9, while the Mohs hardness of polycarbonate is only 3.0, the Mohs hardness of tempered glass is 5.5, and the Mohs hardness of aluminum-magnesium alloy The Mohs hardness of Corning glass is 6.0, and the Mohs hardness of Corning glass is 7.

3. Low thermal conductivity, low expansion coefficient

The thermal conductivity of zirconia is low among common ceramic materials (1.6-2.03W/(m·k)), and its thermal expansion coefficient is close to that of metal. Therefore, zirconia ceramics are suitable for structural ceramic materials, such as zirconia ceramic mobile phone appearance structural parts.

Zirconia Properties

1. The zirconia obtained by burning zirconia hydrate or volatile oxyacid zirconium salt is white powder, insoluble in water, chemical formula:ZrO2 xH2OZrO2+xH2O;

2. The zirconia obtained by mild burning is relatively easy to be dissolved by inorganic acid, the zirconia obtained by strong heat burning is only soluble in concentrated sulfuric acid and hydrofluoric acid, and the zirconia obtained by melting and recrystallization is only soluble in hydrofluoric acid Function, chemical formula:ZrO2+4H+=Zr4++2H2O.

3. Zirconia is an amphoteric oxide, which can form zirconate by eutectic with alkali, but zirconate is easily hydrolyzed into ZrO2 xH2O and precipitated when it meets water. Chemical formula:ZrO2+2NaOH=Na2ZrO3+H2O, Na.ZrO3+H2O=ZrO2+NaOH;

4. Zirconia reacts with carbon and chlorine at high temperature, or reacts with carbon tetrachloride to generate zirconium tetrachloride and zirconium oxide, and then hydrolyzes to obtain zirconium oxide. Chemical formula: 3ZrO2+2C+4Cl2=ZrCl4+2CO2+2ZrOCl2.

5. Zirconia reacts with carbon in the arc to form zirconium carbide, chemical formula:ZrO2+2C=CO2+ZrC;

Applications of Zirconia

1. Raw materials for metal zirconium and its compounds

Used to make metal zirconium and zirconium compounds, refractory bricks and crucibles, high-frequency ceramics, abrasive materials, ceramic pigments and zirconates, etc. Mainly used for piezoelectric ceramic products, daily ceramics, refractory materials and precious metal smelting Zirconium bricks, zirconium tubes, crucibles, etc. It is also used in the production of steel and non-ferrous metals, optical glass and zirconia fibers. It is also used in ceramic pigments, electrostatic paints and baking varnishes. It can be used in epoxy resin to add heat-resistant salt water corrosion.

2. Refractory materials

Zirconia fiber is a polycrystalline refractory fiber material. Zirconia fiber is the only ceramic fiber refractory material that can be used for a long time in an ultra-high temperature environment above 1600°C. Higher service temperature and better heat insulation performance such as acid aluminum fiber, and high temperature chemical stability, corrosion resistance, oxidation resistance, non-volatile, non-polluting.

3. Gas turbine

The application of plasma sprayed zirconia thermal barrier coatings on aviation and industrial gas turbines has made great progress, and to a certain extent has been used in the turbocharger part of gas turbines. Because this type of coating can reduce the temperature of air-cooled high-temperature components by 50~200°C, it can significantly improve the performance of high-temperature components, or allow the temperature of natural gas to be increased or the amount of refrigeration gas to be used, while maintaining the burden on high-temperature components. The temperature does not change, thereby increasing the high efficiency of the diesel engine.

4. Ceramic materials

Due to its high refractive index, high melting point and strong corrosion resistance, zirconia is used as raw material for kiln industry. Piezoelectric ceramic sheet products include filters, speakers, ultrasonic water sound detectors, etc. There are also daily-use ceramics, zircon bricks and zircon tubes for precious metal smelting. Nano-sized zirconia can also be used as a matrix material for polishing agents, abrasive particles, piezoelectric ceramic sheets, precision ceramics, porcelain enamel and high-temperature pigments.

5. Other applications

In addition, zirconia can be used in the manufacture of incandescent gas lampshades, enamel, white glass, refractory crucibles, etc. X-ray photography. Abrasive material. Together with yttrium, it is used to make light source lamps in infrared spectrometers, thick film circuit capacitor materials, and piezoelectric crystal transducer formulas.