Zircon powder can significantly improve the thermal shock resistance of refractories, mainly through the following mechanisms:

I. Reducing the coefficient of thermal expansion

Zircon powder has a low coefficient of thermal expansion, which can maintain the stability of materials in high temperature environment. When added to refractory, it can effectively reduce the overall thermal expansion coefficient of the material and reduce the thermal stress caused by temperature change, thus improving the thermal shock resistance of the material.

II. Formation of refractory mineral phase

In refractories, zirconia (ZrO₂) and silica (SiO₂) in zircon powder can react with other components to form mineral phases with high melting point, such as forsterite (Mg₂SiO₄). These mineral phases can enhance the structural stability of materials at high temperature and reduce the crack propagation caused by thermal shock.

III. Improving the microstructure

Zircon powder has fine particles, which can be evenly distributed in refractories to form a compact microstructure. This dense structure can effectively reduce the porosity inside the material and improve the thermal shock resistance of the material.

IV. Absorbing thermal stress

Zirconia (ZrO₂) in zircon powder has good thermal shock resistance, which can absorb thermal stress at high temperature and reduce the hot cracking tendency of materials. In addition, the porous structure and hollow bead form of zirconia can further improve the thermal shock resistance of the material.

V. Promoting sintering and bonding

Zircon powder can promote the sintering process of refractories and improve their bonding properties. For example, adding appropriate amount of zircon powder to andalusite-based refractories can significantly improve the sintering effect, thus improving the thermal shock resistance of the materials.

VI. Experimental verification

The results show that when 4% (mass fraction) of zircon powder is added to the magnesia composite refractory, the thermal shock resistance of the material is the best, and the compressive strength retention rate of the sample at room temperature after thermal shock is the highest, reaching 91.6%. This shows that the addition of zircon powder can significantly improve the strength retention rate of refractories under thermal shock conditions.

VII. Summary

Zircon powder significantly improved the thermal shock resistance of refractories by reducing thermal expansion coefficient, forming high melting point mineral phase, improving microstructure, absorbing thermal stress and promoting sintering. Its application effect in various refractories has been widely verified.