Silicon carbide (SiC) ceramics have become the core material in the field of high-temperature structural ceramics due to their low thermal expansion coefficient, high thermal conductivity, high hardness, and excellent thermal and chemical stability. They are widely used in key fields such as aerospace, nuclear energy, military, and semiconductors.
However, the extremely strong covalent bonds and low diffusion coefficient of SiC make its densification difficult. To this end, the industry has developed various sintering technologies, and SiC ceramics prepared by different technologies have significant differences in microstructure, properties, and application scenarios. Here is an analysis of the core characteristics of five mainstream silicon carbide ceramics.
1. Non pressure sintered SiC ceramics (S-SiC)
Core advantages: Suitable for multiple molding processes, low cost, not limited by shape and size, it is the easiest sintering method to achieve mass production. By adding boron and carbon to β – SiC containing trace amounts of oxygen and sintering it under an inert atmosphere at around 2000 ℃, a sintered body with a theoretical density of 98% can be obtained. There are two processes: solid phase and liquid phase. The former has higher density and purity, as well as high thermal conductivity and high-temperature strength.
Typical applications: Mass production of wear-resistant and corrosion-resistant sealing rings and sliding bearings; Due to its high hardness, low specific gravity, and good ballistic performance, it is widely used as bulletproof armor for vehicles and ships, as well as for protecting civilian safes and cash transport vehicles. Its multi hit resistance is superior to ordinary SiC ceramics, and the fracture point of cylindrical lightweight protective armor can reach over 65 tons.
2. Reaction sintered SiC ceramics (RB SiC)
Core advantages: Excellent mechanical performance, high strength, corrosion resistance, and oxidation resistance; Low sintering temperature and cost, capable of forming near net size. The process involves mixing a carbon source with SiC powder to produce a billet. At high temperatures, molten silicon infiltrates the billet and reacts with carbon to form β – SiC, which combines with the original α – SiC and fills the pores. The size change during sintering is small, making it suitable for industrial production of complex shaped products.
Typical applications: High temperature kiln equipment, radiant tubes, heat exchangers, desulfurization nozzles; Due to its low thermal expansion coefficient, high elastic modulus, and near net forming characteristics, it has become an ideal material for space reflectors; It can also replace quartz glass as a supporting fixture for electronic tubes and semiconductor chip manufacturing equipment.
3. Hot pressed sintered SiC ceramics (HP SiC)
Core advantage: Synchronous sintering under high temperature and high pressure, the powder is in a thermoplastic state, which is conducive to mass transfer process. It can produce products with fine grains, high density, and good mechanical properties at lower temperatures and in a shorter time, and can achieve complete density and near pure sintering state.
Typical application: Originally used as bulletproof vests for US helicopter crew members during the Vietnam War, the armor market was replaced by hot pressed boron carbide; At present, it is mostly used in high value-added scenarios, such as fields with extremely high requirements for composition control, purity, and densification, as well as wear-resistant and nuclear industry fields.
4. Recrystallized SiC ceramics (R-SiC)
Core advantage: No need to add sintering aids, it is a common method for preparing ultra-high purity and large SiC devices. The process involves mixing coarse and fine SiC powders in proportion and forming them, sintering them in an inert atmosphere at 2200~2450 ℃. Fine particles evaporate and condense at the contact between coarse particles to form ceramics, with a hardness second only to diamond. SiC retains high high-temperature strength, corrosion resistance, oxidation resistance, and thermal shock resistance.
Typical applications: High temperature kiln furniture, heat exchangers, combustion nozzles; In the aerospace and military fields, it is used to manufacture spacecraft structural components such as engines, tail fins, and fuselage, which can improve equipment performance and service life.
5. Silicon infiltrated SiC ceramics (SiSiC)
Core advantages: Most suitable for industrial production, with short sintering time, low temperature, fully dense and non deformed, composed of SiC matrix and infiltrated Si phase, divided into two processes: liquid infiltration and gas infiltration. The latter has higher cost but better density and uniformity of free silicon.
Typical applications: low porosity, good airtightness, and low resistance are conducive to eliminating static electricity, suitable for producing large, complex or hollow parts, widely used in semiconductor processing equipment; Due to its high elastic modulus, lightweight, high strength, and excellent airtightness, it is the preferred high-performance material in the aerospace field, which can withstand loads in space environments and ensure equipment accuracy and safety.
Post time: Sep-02-2025