Silicon Carbide (SiC) is one of the world’s most adaptable refractory ceramics, boasting impressive physical and chemical properties that make it suitable for an array of industrial uses.
SiC is an excellent material for ballistic protection as it safely stops projectiles without absorbing their energy, all with significantly lower product weight than armour metals.
Chemical Resistance
Silicon carbide (SiC) is a key material used in modern technological applications. Due to its unique set of characteristics that enable it to perform at temperatures well beyond 1000 degC, SiC finds widespread use across numerous industry fields.
This material stands out for its remarkable strength, durability and corrosion resistance. It boasts an outstanding fracture toughness of 6.8 MPa m0.5 that highlights its resilience against stress cracking while its Young’s modulus of 440 GPa indicates its stiffness under load and ability to retain its shape under loads. Furthermore, its flexural strength of 490 MPa ranks it amongst one of the strongest materials ever known to man.
Silicon carbide ceramics have an ideal combination of abrasion-resistance and heat-resistance that make it well suited for harsh environments, which explains their widespread usage across industries such as steel and metallurgy, as stationary hot sections in petrochemical plants, bearings, mechanical seals and cutting tools in automobile manufacturing, as well as stationary hot sections for stationary hot sections in petrochemical plants.
SiC can owe its chemical resistance to an oxide layer composed of silicon dioxide that covers its surface and protects the material from aggressive chemicals, while having poor resistance against alkalis; this means it should not be exposed for extended periods to strong acids, nor be used in environments with limited water or steam lubrication as lubrication sources.
High Temperature Resistance
Silicon carbide ceramic materials boast the highest temperature resistance among known ceramic materials. It can maintain strength up to 1600 deg C while still being ductile and having low friction and wear rates, making it ideal for applications where ceramic components will need to be exposed to high temperatures or chemically aggressive media.
Chemical industry applications as well as process engineering applications find suitable uses for these materials. Nitride-bonded silicon carbide beams are often utilized in ceramic sintering kilns due to their excellent temperature resistance and thermal conductivity properties, along with resistance against acids as well as applications like shot blast nozzles or cyclone components.
Silicon carbide’s ability to withstand neutron radiation and corrosion makes it an attractive material for nuclear and space applications, and also makes it useful in lining furnaces refractorily.
Hot pressing and direct sintered are among the many sintering methods that allow it to be molded, providing for a variety of fabrications such as thermal insulation sheets, electrical components and even semiconductor processing. Furthermore, its properties provide good flexural strength, fracture toughness and Vickers hardness; further complemented with its excellent oxidation resistance and wear resistance, it makes an excellent material choice for bulletproof plates, nozzles and other high-temperature corrosion-resistant equipment production.
Resistance to Corrosion
Silicon carbide is one of the hardest materials known, only surpassed by diamond and cubic boron nitride in terms of hardness. It makes an ideal material to use where physical wear is a major concern and provides exceptional chemical resistance and low thermal expansion rates.
Corrosion of SiC ceramics is an intricate phenomenon influenced by both chemical and physical effects in their environment, and on their material. Although much effort has been expended in understanding corrosion of SiC and SiC-based composites in harsh environments, many fundamental questions still exist.
As an example, the rate of oxidation on SiC depends on both its environment and microstructure; impurities, sintering aids, grain boundary phases and porosity all play an essential part. Furthermore, its corrosion rate also depends on its pH environment.
Due to their outstanding resistances against corrosion and oxidation, high temperature strength, low creep, and heat shock resistance, SiC ceramics have long been recognized for their exceptional static hot sections on rockets, airplanes, car engines and gas turbines. Furthermore, their excellent resistance properties also make SiC ceramics valuable components of refractories including burner nozzles, jet and flame tubes, combustion chambers, furnace components as well as furnace components. In the metallurgical and chemical industry applications these ceramics make essential high temperature refractory electrodes and thermistors.
Toughness
Silicon carbide is one of the hardest non-oxide ceramics. It maintains its strength even at extremely high temperatures, making it suitable for many refractory applications such as furnace lining, metal casting and petrochemical metallurgical processes. Furthermore, sinterd silicon carbide boasts excellent sliding abrasion resistance; in fact, only diamond, cubic boron nitride and tungsten carbide surpass it in hardness.
Low fracture toughness of conventional ceramics prevents them from being used in more mechanically demanding applications, but SiC-based ceramics may be enhanced in terms of toughness by applying an effective deformation mechanism – in part because directional bonds within ceramics can be overcome using dislocations. Therefore, developing tough SiC ceramics could open up new applications and improve overall ceramic material performance.
Reaction bonded SiC ceramics exhibit superior toughness due to the formation of laminated reinforcements formed through reactive sintering by the aggregation of graphene platelets into laminated reinforcements, crack bridging, reinforcement pullout and delamination as toughening mechanisms. Annealing further increases fracture toughness by inducing grain growth.