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What are the synthetic methods of refractory materials?

After the natural materials are processed through the above processes, their quality and variety still cannot meet the needs of refractory materials, so artificial refractory materials need to be synthesized. Synthetic raw materials can artificially control their chemical composition and phase composition according to the purpose of use. Kind of performance.
Controlling the chemical composition and phase composition of synthetic raw materials is achieved by controlling the raw materials used and the synthesis process. Refractory materials that exist in nature but are not valuable for mining can also be obtained through artificial synthesis. The classification of synthetic raw materials includes chemical methods, sintering methods, and electric fusion methods.
(1) Sintering synthesis of refractory raw materials is natural or industrial raw materials, which are finely ground, homogenized and calcined at high temperature to form the expected mineral phase.
① Homogenization. Homogenization is particularly important for the synthesis of refractory raw materials by sintering. In order to obtain synthetic raw materials with uniform phases, the natural raw materials, industrial raw materials and additives used should be strictly measured and thoroughly mixed and finely milled to make their components highly uniformly dispersed. The wet blending process can ensure the uniformity of synthetic raw materials to the greatest extent.
② Forming. The molding method depends on the method of homogenization. The homogenization is a dry method. There are three methods for forming the ball: pressing the ball with a ball press, forming a ball into a ball, and pressing a blank with a brick press. The homogenization is a wet method, and the molding method is to squeeze the mud into a strip shape or a billet shape.
③ firing. After the carcass is dried, it is fired in a kiln. The sintering synthetic raw material is actually sintering of batch materials at high temperature. Commonly used sintering equipment includes shaft kiln, rotary kiln and tunnel kiln. Small batches of synthetic materials can be used in inverted flame kiln, shuttle kiln.
(2) Melt (electric fusion) synthesis method. This method uses a high temperature melting method to obtain a raw material with a desired mineral composition. The melting method is simpler than the sintering method, the melting temperature is higher, the synthesized raw materials are higher in purity, and the crystals are well developed. Therefore, some properties are better than the sintering method. It is a promising method for the synthesis of refractory raw materials in the future.
Unlike the sintering method, this method also has the effect of partially removing impurities, such as fused mullite using alumina as the main raw material, which can remove most of the iron oxide and part of the titanium oxide.
(3) Chemical synthesis method. Chemical purification is an important method for preparing high-purity raw shake. It uses a series of chemical and physical chemical reactions to achieve the purpose of separating minerals. For example, the bauxite mine uses the Bayer method to prepare industrial alumina, and uses seawater or brine to prepare high-purity magnesium oxide. However, the disadvantage of this method is that the reaction process is complicated and the cost is high.
(4) Other methods. In addition to the above methods, there are other unique methods. For example, the manufacture of silicon carbide is silica, coke, heating in a resistance furnace at 200,500C, and reaction formation: synthetic silicon nitride is formed by direct nitriding reaction of metal silicon powder, and the synthesis temperature is generally 1200 ~ 1450 "C.