Under the situation of rapid development of science and technology, to prepare high-temperature, high-performance, new-type materials, the first thing to do is to solve the refractory materials needed in the preparation process. The characteristics of refractory materials are as follows:

1. Mechanical properties

The elastic modulus of special refractory materials is large. Most have higher mechanical strength, but compared with metal materials, due to brittleness, impact resistance is very low. Most special refractory materials have high hardness, so they have better resistance to wear, airflow or dust erosion. Most special refractory materials have relatively small high-temperature creep is molybdenum disilicide. The size of the creep value is related to the crystal size, grain boundary material, porosity, etc.

2. Thermal properties

(1) Thermal expansion: Thermal expansion refers to the reversible increase and decrease of the linearity and volume temperature of the material. It is often expressed in terms of linear expansion number or volume expansion coefficient. Most special refractory materials have relatively large linear expansion coefficients, only fused silica, boron oxide, and silicon oxide have relatively small linear expansion coefficients.

3. Nature of Use

(1) Fire resistance: The melting points of special refractory materials are almost all above 2000°C, and hafnium carbide (HfC) and tantalum carbide (TaC) are 3887°C and 3877°C. The refractoriness is also very high. In an oxidizing atmosphere, the operating temperature of the oxide is even close to the melting point. Nitrides, borides, and carbides have higher operating temperatures than oxides in neutral or reducing atmospheres. For example, TaC can be used up to 3000°C in N2 atmosphere, and BN can be used up to 2800°C in Ar atmosphere. The high temperature resistance is in order: carbide>boride>nitride>oxide. And their high temperature oxidation resistance is: oxide>boride>nitride>carbide.

(2) Thermal shock resistance: In special refractory materials, due to the low thermal conductivity of beryllium oxide, the thermal conductivity of most borides is not high, and the linear expansion coefficient of fused silica is particularly small, so thermal shock resistance is very high. good. Certain fiber products and fiber-reinforced composite products have higher porosity and tensile strength, and these materials have better thermal shock resistance. Silicon carbide, silicon nitride, boron nitride, molybdenum disilicide, etc. also have good thermal shock resistance.

However, there are not many oxide materials with high melting point, good chemical stability, and excellent high temperature performance. Zirconia (high temperature (2300℃~2400℃)) has good chemical stability, is not easy to decompose, and has strong corrosion resistance to acid and alkali slag. Good special oxide refractory material.

Nano zirconia is a white powder, which can be divided into monoclinic phase, tetragonal phase and cubic phase due to the sintering temperature and the content of stabilizers such as added yttrium oxide. It is soluble in sulfuric acid and hydrofluoric acid. Nano zirconia has good dispersibility, good thermochemical stability, high temperature conductivity, high strength and toughness, good mechanical, thermal, electrical, and optical properties. Nano zirconia has small particle size, strong stability, acid resistance, Alkali resistance, corrosion resistance, and high temperature resistance.

Zirconia refractories refer to products with zirconia as the main component. At present, the domestic requirements of this kind of refractory materials for zirconia are concentrated in three series: ZrO2-CaO, ZrO2-MgO, ZrO2-Y203, of which Z-CaO is used in large quantities. The quality level of zirconia refractory products largely depends on the raw materials. The chemical composition of the zirconia raw materials determines the possible crystal structure of the material and the chemical stability of the product. The particle size control of the raw materials basically determines the performance of the product. The preparation process determines the crystal structure and impurity content of the raw materials.

The role of zirconia in refractories
(1) Good chemical stability, prolong the corrosion of Fe and other metal ions to refractory products.
(2) Improve the performance of materials and improve the thermal stability of refractory products.
(3) According to the different properties of the compound item, the production process can be optimized to improve the performance of the refractory product and reduce the production cost.

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