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properties of sintered silicon carbide

SiC is found in meteorites and is almost non-existent in nature; therefore, SiC powders for industrial applications are thermally synthesized. The main method of industrial production of silicon carbide is the direct electrical reduction (in a resistance furnace) of quartz sand (silica) with coke (C), usually at a temperature of 1900°C or more, when the chemical reaction that occurs is :SiO2 + 3C = SiC + 2CO.The main methods for preparing high-temperature silicon carbide ceramic are sintered silicon carbide, hot-pressure sintering, hot isostatic sintering, and reactive sintering. Table 1 shows the various sintering methods and physical properties



sintered silicon carbide Hot pressing


thermal isostasis

Pressed sintering



Bulk density (g/ cm3) 3.12 3.21 3.21 3.05
Fracture toughness ( MPa -m1/ 2 ) 3.2 3.2 3.8 3.0
Flexural strength(MPa)20℃ 1400℃ 410 640 640 380
410 650 610 300
Modulus of elasticity ( GPa ) 410 450 450 350
Coefficient of thermal expansion (10 – 6/ K) 4.7 4.8 4.7 4.5
Thermal conductivity ( W/ m -K) 20℃

1000 °C

110 130 220 140
45 45 50 50

Table 1: Sintering methods and physical properties of SiC ceramics

sintered silicon carbide is considered to be the most promising sintering method for SiC sintering, and large size and complex shape SiC ceramics can be produced by atmospheric pressure sintering process. By adding boron and carbon to high purity β-SiC containing trace oxygen (less than 0.2 % oxygen) and sintering it in an inert atmosphere at 2000 ℃, GE has successfully obtained sintered silicon carbide with a density higher than 98% at 2020 ℃. The SiC ceramics with flexural strength and fracture toughness of 707 and 10.7 were sintered at 1850 ℃ using Y2O3 and Al2O3 as sintering aids and YA G (Y3Al5O12) with lower melting point as the basic formulation element. Liu Baoying of Shandong Silicate Research and Design Institute added appropriate amount of Al2O3 and Y2O3 as sintering additives and used slurry molding process to produce fine SiC composite ceramics with relative density of 97% at 1780 ℃, which can meet the needs of industrial production of mechanical seals and wear-resistant ceramics. However, so far, the research on this kind silicon carbide ceramic is not very thorough and needs to be further developed.