Mineral composition and organizational structure of refractory materials

Mineral composition of refractory materials

Refractory products are mineral components. The properties of a product are a comprehensive reflection of its constituent minerals and microstructure. The mineral composition of refractory products depends on their chemical composition and process conditions. Products with the same chemical composition may have significant differences in performance due to differences in the types, quantities, grain sizes, and binding conditions of the mineral phases formed due to different process conditions. For example, siliceous products with the same SiO2 content may form two types of minerals with different structures and properties - phosphoquartz and cristobalite - under different process conditions, resulting in differences in certain properties of the products. Even if the mineral composition of the product is constant, differences in grain size, shape, and distribution of the mineral phase can have a significant impact on the properties of the product (such as molten products), zirconia ceramics.

Refractory materials are generally composed of multiple components, and the mineral phase can be divided into two categories, namely crystalline phase and glass phase.

The main crystalline phase refers to the crystalline phase that forms the main structure of the product and has a high melting point. The properties, quantity, and bonding state of the main crystalline phase directly determine the properties of the product.

Matrix refers to the substance present in the gaps between large crystals or aggregates in refractory materials. The substrate plays a decisive role in the properties of the product, such as high temperature characteristics and resistance to corrosion. When in use, products often start to damage from the substrate, and adjusting and changing the substrate composition of the product is an effective process measure to improve product performance.

The vast majority of refractory products (except for a few ultra-high refractory products) can be divided into two categories based on their main crystalline phase and matrix composition: one type is multi-component refractory products containing crystalline and glass phases, such as clay bricks, silicon bricks, etc; The other type is multi-component products that only contain crystalline phases, and the matrix is mostly fine crystals, such as alkaline refractory materials such as magnesium bricks and chrome magnesium bricks. When these products are fired at high temperatures, a certain amount of liquid phase is generated, but the liquid phase does not form glass when cooled, but forms a crystalline matrix that binds the main crystalline phase together. The composition of the matrix crystal is different from that of the main crystalline phase.

There are two types of microstructure of refractory products. One type is the structure type of crystal particles cemented by silicate (silicate crystal mineral or glass body) complexes, and the other type is the crystal network directly interwoven by crystal particles, such as high-purity magnesium bricks. The high-temperature performance (high-temperature mechanical strength, slag resistance, or thermal shock stability, etc.) of products directly bonded with this structure type is much superior to the previous one; Therefore, it has broad development prospects

Refractory material organizational structure

Refractory materials are heterogeneous materials composed of two parts: solid phase (including crystalline phase and glass phase) and pores, in which various shapes and sizes of pores are related to the macroscopic structure of the solid phase.

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