The preparation of silicon carbide ceramics requires a series of delicate operations, and each link has an important impact on the quality of the final product. The pretreatment of raw materials is the beginning of the entire process, and the silicon carbide powder needs to be carefully screened and formulated. First of all, it is necessary to ensure that the purity of the selected powder is high enough, and on this basis, the coarseness and fineness of the powder particles are reasonably matched to facilitate the subsequent green body to form a higher density. At the same time, according to the different requirements for the performance of silicon carbide ceramics, some auxiliary materials may be added to enhance its specific properties, and these materials are fully mixed in a suitable way to ensure that all particles are evenly distributed.
The choice of molding process depends on the shape and specifications of the product. For those products with relatively simple structures, a more direct pressing method is usually used. The mixed powder is placed in a specific mold and a certain pressure is applied to form a green body with a preliminary shape and a certain strength. For products with complex structures, another molding method is used. The powder and the bonding material are mixed in proportion to form particles, which are then injected into a precision mold and taken out after cooling. This can better ensure the molding accuracy of the complex structure.
Degreasing is an important step to remove organic components from the green body. The green blank after forming contains certain organic binding substances. It needs to be placed in a special equipment and slowly increase the temperature under a specific gas environment so that these organic substances can gradually decompose and volatilize. In this process, the temperature increase rate must be strictly controlled to prevent the green body from cracking due to the rapid change of internal substances, and ensure that the green body can maintain a stable structure.
The sintering process is the core link that determines the density and mechanical properties of silicon carbide ceramics. The green blank after preliminary treatment needs to be sintered in a high temperature environment. Different sintering methods will bring different effects. Some are under normal pressure, by adding some auxiliary materials to promote the diffusion between particles and the elimination of pores; some will apply a certain pressure at high temperature to further increase the density of the green body. The entire sintering process requires precise control of the environment and temperature to ensure that silicon carbide ceramics can form a stable structure and good performance.
After sintering, silicon carbide ceramics also need to be processed to meet the requirements of size and precision for actual use. Because silicon carbide ceramics are very hard, ordinary processing tools are difficult to process them, so special processing methods are required. For different surface accuracy requirements, appropriate processing tools and methods will be selected. For some complex curved surfaces, there are also special processing methods to ensure the accuracy of their shapes.
Surface treatment can further improve the performance of silicon carbide ceramics. Different surface treatment methods will be used according to the different use environments of silicon carbide ceramics. If it is used in a high temperature environment, a special coating may be formed on the surface to enhance its anti-oxidation ability; if it is used in a corrosive environment, a protective film will be formed on the surface through treatment to improve its ability to resist acid and alkali corrosion.
Quality inspection is the last link in the preparation process to ensure that the product meets the use requirements. The mechanical properties of silicon carbide ceramics will be tested by special testing methods to see if they meet the specified strength standards; at the same time, the internal defects of silicon carbide ceramics will be checked to ensure the integrity of their structure. In addition, some physical properties of silicon carbide ceramics will be measured to verify their stability in different environments. Only products with qualified indicators can be put into use.
