Zirconium boride is a common material in borides, and there are three kinds of zirconium boride in the boron zirconium system,

They are zirconium diboride (ZrB), zirconium diboride (ZrB2) and zirconium dodecaborate (zrb12),

However, zirconium diboride has good stability in a wide temperature range, so it is produced in industrial production

Zirconium borate is mainly composed of zirconium diboride.

Chinese Name: zirconium diboride

CAS No:12045-64-6

EINECS No.: 234-963-5

Molecular formula: ZrB2

Molecular weight 112.84

Density 4.52g/cm3

Melting point (3040 ℃)

1： Application field

1. Aerospace Military Industry

ZrB2 series composites are very suitable for ultra-high temperature zero ablation materials used in supersonic aerospace vehicles and missile shells because of their high melting point, high hardness, good conductivity and good neutron control ability. Especially with the rapid development of rocket and missile technology, the demand for high temperature structural materials of zirconium borate based ceramics is more urgent. With the deepening of research and development and the continuous improvement of production technology, it is certain that the

Research, production and application will leap forward at a new pace. Zirconium diboride (ZrB2) has the comprehensive characteristics of high melting point, high modulus, high hardness, high thermal conductivity, good thermal shock resistance, etc. because of its strong chemical bond characteristics, it has become a potential candidate material for ultra-high temperature ceramic Z. ZrB2 ceramic products have been widely used as various high-temperature structural and functional materials, such as turbine blades and MHD power generation electrodes in the aviation industry. In addition, compared with many ceramic materials, it has better conductivity, and can produce parts with complex shapes by wire cutting technology. However, ZrB2 material has high melting point, difficult sintering, and relatively low strength and toughness, which limits its application in harsh working environment. Therefore, scholars at home and abroad have done a lot of research work on ZrB2 composites with other components by using various advanced sintering processes to improve the comprehensive properties of the materials. The author mainly summarized the research work on ZrB2 composite system and densification.

2. Refractory

ZrB2 ceramic is an excellent special refractory, which can be used as high-temperature thermocouple protection sleeve, mold, crucible of metallurgical metal, etc. when used as thermocouple protection sleeve, it has poor air tightness and conductivity. Therefore, it is necessary to cooperate with aluminum oxide inner sleeve to carry out effective temperature measurement. The thermowell made of this material can be used continuously for a long time in molten iron and brass melt. ZrB2 ceramics can also be used as an antioxidant for refractories. Lvchunyan and others reported that adding ZrB2 to MgO-C refractories or directly using ZrB2 as aggregate or fine powder to make refractory bricks and castables has very good oxidation resistance and fire resistance. Its oxidation resistance mechanism can be analyzed as that B2O3 formed by oxidation of zirconium borate at medium temperature forms MgO · B2O3 molten phase in MgO-C, thus protecting the bricks.

3. Electrode material

ZrB2 is suitable for contact materials and electrode materials due to its low resistivity and electronic conduction mechanism. It can be used in the electrodes of metal thermocouples and high-temperature heating elements. In 1994, fengdagan developed a kind of sleeve thermocouple material with ZrB2 and graphite. It is proved by experiments that it can work in an oxidizing atmosphere at 1200~1600 ℃, and the thermoelectric potential value is large. At 1600 ℃, it can reach about 70 MV, and the thermoelectric potential rate is high, about 55 μ V/℃。 The thermoelectric potential changes as a single value function with good linearity. After many tests in oxidizing atmosphere, its repeatability is 1%~1.5% of the measured temperature, and its z obviously changes to 0.5%~1% of the measured temperature after a short continuous test for more than 3 hours. It can play a role in continuous temperature measurement in some special occasions where metal thermocouples and radiation thermometers are not applicable. It is a good thermocouple material.

2： Preparation of zirconium diboride ceramics

① Preparation of ZrB2 powder

ZrB2 powder is mainly prepared by boronizing zirconium or high oxide. The traditional synthesis method is to realize the carbon thermal reduction process of oxides in a high-temperature induction furnace or resistance furnace. This method is simple, but the general temperature is high (about 1800 ℃), the purity of synthetic powder is low, the average particle size is large, and the sintering activity is poor. At present, carbothermal reduction method, high temperature self propagating method

Mechanical alloying method, ceramic precursor pyrolysis method, liquid phase method, etc.

② Forming method of ZrB2 ceramics

There are many forming methods for ZrB2, such as isostatic pressing, dry pressing, grouting and solidification. People can choose different forming methods according to their own needs and actual conditions. In order to improve the density of products and reduce the sintering temperature, people mostly adopt hot pressing sintering, which is a process of forming and sintering at the same time, but only ZrB2 ceramic products with simple shape can be obtained.

③ Sintering method of ZrB2 ceramics

The traditional sintering methods of ZrB2 materials include pressureless sintering and hot pressing sintering. The new sintering methods include in-situ reaction hot pressing, high temperature self propagating sintering and spark plasma sintering.

3、 Application examples of zirconium diboride ceramic materials

Zirconium diboride ceramics have been widely used in the fields of high temperature structural ceramics, composites, refractories, electrode materials and nuclear control materials because of their high melting point and hardness, good conductivity and thermal conductivity, and strong neutron control ability. For example, turbine blades and MHD power generation electrodes in the aviation industry. In addition, compared with many ceramic materials, it has better conductivity, and can produce parts with complex shapes by wire cutting technology.

① Refractory

ZrB2 ceramic is an excellent special refractory, which can be used as high-temperature thermocouple protection sleeve, mold, crucible of metallurgical metal, etc. when used as thermocouple protection sleeve, it has poor air tightness and conductivity. Therefore, it is necessary to cooperate with aluminum oxide inner sleeve to carry out effective temperature measurement. The thermowell made of this material can be used continuously for a long time in molten iron and brass melt. ZrB2 ceramics can also be used as an antioxidant for refractories.

② Electrode material

ZrB2 is suitable for electric shock materials and electrode materials due to its low resistivity and electronic conduction mechanism. It can be applied to the electrodes of metal thermocouples and high-temperature heating elements. In 1994, some researchers developed a kind of sleeve thermocouple material with ZrB2 and graphite. It is proved by experiments that it can work in an oxidizing atmosphere at 1200~1600 ℃. The thermocouple value is large, reaching about 70mV at 1600 ℃, and the thermoelectric potential rate is high. It can play a role in continuous temperature measurement in some special occasions where metal thermocouples and radiation thermometers are not applicable. It is a good thermocouple material.

③ Other materials

Because of its extremely high hardness, ZrB2 is a very good wear-resistant material, which has a good application in cutting tools and cutting tools. Because ZrB2 has good corrosion resistance, the corrosion resistance and oxidation resistance films of ZrB2 have been studied deeply abroad.