Reaction sintering method of silicon carbide ceramics

What is silicon carbide ceramic?
Silicon carbide ceramics are one of the most widely used materials in structural ceramics. Due to its relatively low thermal expansion, large specific strength, high thermal conductivity and hardness, wear resistance and corrosion resistance, and most importantly, it can still maintain good performance at high temperatures up to 1650°C. Performance, these properties make silicon carbide ceramics widely used in various fields.

Silicon carbide ceramic properties
Silicon carbide ceramics ranks first among many structural ceramics due to its excellent thermal conductivity and thermal diffusivity, far exceeding similar materials. However, its high elastic modulus and large thermal expansion coefficient lead to poor performance in thermal shock resistance. This performance is significantly weaker than silicon nitride and only slightly better than zirconia ceramics. The thermal shock performance of materials actually depends on the specific application scenario. Silicon nitride will be a better choice in environments facing drastic temperature fluctuations; and when temperature changes are relatively gentle, silicon carbide’s high thermal conductivity will allow it to exhibit better performance.
Compared with other structural ceramics, silicon carbide’s fracture resistance is slightly inferior. This characteristic has raised concerns in the industry about its reliability in applications such as internal combustion engine components, such as turbine rotors, because these components may be subjected to external forces during operation. of fracture. However, silicon carbide is an excellent abrasive, exhibiting excellent damage resistance to particles and mixtures in wear tests. It is worth noting that despite its many advantages, reaction sintered silicon carbide (RSSC) is not as good as single-phase sintered materials in terms of resistance to attack by acids, alkalis, and high-temperature combustion products.

Application scenarios of silicon carbide ceramics
Carbon silicide-carbon composite ceramics are used to create high-performance “ceramic” brake discs due to their ability to withstand extreme temperatures. However, due to their high price, these brake discs are currently only used on some super sports cars and other high-performance cars. It is also used as an additive in oils to reduce friction, emissions and noise.
Silicon carbide ceramic material is a commonly used abrasive in modern gemstone processing due to its durability and relatively low cost. In production, it is used in abrasive processing processes such as grinding, honing, water jet cutting and sand blasting. Additionally, silicon carbide particles are laminated to a substrate, creating commonly used sandpaper.
Silicon carbide components are widely used in the melting of glass and non-ferrous metals, heat treatment of metals, float glass production, production of ceramics and electronic components, igniters in pilot lights of gas heaters, etc.

Silicon carbide ceramic manufacturing technology
Common sintering methods for silicon carbide ceramics: atmospheric pressure sintering, reaction sintering, etc.
In the preparation process of reaction sintered silicon carbide (RSSC), α-SiC powder is first mixed with specific additives and pressed to form a preform (green body). Subsequently, the green body is in contact with liquid silicon in a high temperature environment of 1500°C. The carbon inside the green body reacts with silicon to generate β-SiC phase while retaining the original α-SiC phase. During this process, unreacted silicon fills the pores in the material, achieving high density of the material, and ultimately forms silicon carbide ceramics with excellent structural stability. Remarkably, the material maintains its stable structure up to 1370°C, at which point silicon begins to melt.
Using this method, the preform can be prepared by traditional ceramic processing technology, and the relatively low reaction temperature of 1500°C, as well as the loose requirements on the particle size and purity of the raw material powder, enable the production cost of RSSC to be effectively controlled, enabling it to be produced at a relatively low cost. Manufacturing of high-quality products at economical prices.

Silicon carbide reaction sintering furnace