Zirconia ceramic tubes are made from pure zirconia powder by high-temperature sintering. Zirconia (ZrO₂) is usually a white, odorless and tasteless crystal with a relative density of 5.85, a melting point of 2680°C, a boiling point of 4300°C and a hardness second only to diamond. It is chemically stable and has a high melting point, high resistivity, high refractive index and low coefficient of thermal expansion. Because of these characteristics, zirconia ceramic tubes play an important role in many fields.
The main component of boron nitride tubes is boron nitride (BN). Boron nitride has a variety of crystal types, and the common hexagonal boron nitride ceramic structure is similar to graphite, known as ‘white graphite’.
With their unique crystal structure, boron nitride tubes exhibit a range of excellent properties and are widely used in specific fields.
Mechanical Properties
Strength and hardness: Zirconia ceramic tubes have excellent mechanical strength and compression resistance and are able to withstand high pressure without deformation or fracture. Its high hardness performs well in some scenarios that require wear resistance.
Boron nitride tubes have relatively low hardness, especially hexagonal boron nitride tubes, and have self-lubricating properties, which gives them an advantage in some applications where a coefficient of friction is required, although they are not as good as zirconia ceramic tubes at withstanding high pressures and high wear.
Toughness: Zirconia ceramics have high toughness through a martensitic phase transition toughening mechanism, which enables them to absorb energy through phase transitions when subjected to impact, reducing crack expansion and thus increasing the material’s resistance to damage. In contrast, boron nitride tubes have average toughness and are more susceptible to damage when subjected to larger impacts.
Thermal Properties
Coefficient of Thermal Expansion: In high-temperature environments, where differences in thermal expansion caused by temperature changes result in deformation and damage to metal components, zirconia ceramic tubes can effectively mitigate this problem with their low coefficient of expansion, increasing the service life of the equipment.
Boron nitride tubes have a low coefficient of thermal expansion; for example, hexagonal boron nitride has a relatively low coefficient of thermal expansion among all types of ceramics, which makes it dimensionally stable and produces less thermal stress in environments with rapid temperature changes.
Thermal conductivity: zirconia ceramic tubes have a relatively low thermal conductivity and a certain degree of thermal insulation, which can be used in some high-temperature equipment components that have requirements for thermal insulation. Boron nitride tubes, especially hexagonal boron nitride tubes, have good thermal conductivity, and in application scenarios that require rapid heat dissipation or heat homogenization, such as heat dissipation components for electronic equipment, they can quickly transfer heat out and maintain stable equipment operation.
Chemical properties
Corrosion resistance: zirconia ceramic tube has good corrosion resistance, can withstand a variety of chemical media, such as in the chemical industry, can be used in pipelines, valves, pumps and other components, and can effectively resist chemical erosion. Boron nitride tube also has good chemical stability and, in some corrosive environments, can maintain stable performance.
Chemical activity: zirconium oxide is relatively stable chemically, and it is not easy to have chemical reactions with other substances under general conditions. Boron nitride may react chemically with some substances under extreme conditions such as high temperature and high pressure, but its chemical activity is low in regular-use environments and can meet the needs of most applications.