Silicon carbide ceramics are among the hardest and most chemically resistant fine ceramics, boasting superior resistance against corrosion, abrasion and friction wear while remaining strong under high temperatures with very little creep.
Edward G. Acheson was searching for ways to produce diamonds out of clay when he discovered hard green crystals now known as carborundum or SiC. After making this discovery commercially viable in large quantities.
Hardness
Silicon carbide is one of the strongest, hardest advanced ceramic materials on earth. With properties including thermal stability, chemical inertness and mechanical strength under pressure – hallmarks of its unrivaled properties – Silicon carbide plays an integral role in technology and industrial applications across multiple sectors.
Extremely hard synthetic material used for various applications including grinding wheels and sandpaper in the abrasives industry, cutting tools for heavy industries and refractory linings in industrial furnaces. Furthermore, wear-resistant parts used on pumps, rocket engines and light emitting diodes also employ this material.
Due to its strength, silicon carbide has long been used in military applications, such as bullet-resistant ceramic armor. A number of studies have compared the ballistic performance of SiC ceramics against materials like aluminum oxide and alumina using both experimental and computational approaches.
Hardness of silicon carbide is an integral property for evaluating its suitability as an armour material, yet different hardness measurement techniques and loads have an enormous effect on its values. Therefore, to ensure consistent test results it is vital to use universal testing machines which use consistent loads in each test; more basic approaches involve measuring surface scratches with known harness values while more sophisticated ones analyse deeper scratch patterns to provide insight into mechanical properties of silicon carbide materials.
Thermal Conductivity
SiC is well known for its excellent refractory properties; however, its thermal conductivity stands out as one of the highest thermal conductivities among non-oxide engineering ceramics and even surpassing some metallic materials in thermal conductivity.
SiC can be made into ceramic by firing it in air or vacuum at high temperatures. This produces sintered silicon carbide, an exceptional material with outstanding chemical and mechanical properties which remain strong under high temperatures. Due to its highly porous nature, sintered SiC is easy to process and shape into ceramic forms.
SiC is typically known for its hexagonal crystal structure that resembles that of Wurtzite, although through heat treatment this structure can be altered into a cubic polytype with zincblende structure known as b-SiC with a higher surface area that serves as an excellent support for heterogeneous catalysts.
Pure b-SiC is colorless; however, industrial products often exhibit brown to black hues due to iron impurities. Doped with nitrogen or phosphorus creates an n-type semiconductor; beryllium, boron or aluminum can also be added for p-type properties; these capabilities make b-SiC an integral component in many solar power systems today.
Resistance to Chemical Reactions
Silicon carbide has proven itself resilient against even the harshest chemical environments, including acid and alkali environments, for an extended period of time. Furthermore, its corrosion-resistance and high abrasion resistance make it an excellent material choice.
Noncombustible and resistant to fast reactions with air, water or molten metals, it works reliably in high temperature furnaces as well as for petrochemical production.
Silicon carbide’s purity is essential to many applications, particularly those related to refractories and advanced ceramics. Elkem provides a selection of grades and qualities suitable for industrial use.
Pure silicon carbide possesses a covalent network structure with vertex sharing of silicon and carbon atoms, leading to slow grain boundary diffusion at lower temperatures and making sintering difficult. To increase mechanical strength, silicon carbide may be doped with boron [60], which reduces diffusion coefficient by three orders of magnitude for quicker sintering processes at lower temperatures.
Silicon Carbide is an excellent material for modern abrasive processes such as grinding, machining and sandblasting. Lapidary has long used silicon carbide due to its durability. When bonded with yttria it becomes a very hard ceramic; in addition it forms the basis for various industrial refractory products including ceramic plates found on bulletproof vests.
Electrical Conductivity
Silicon Carbide is an outstanding conductor of electricity. Its high resistance (s) results from its large bandgap, which allows electrons to more readily move between its valence and conduction bands of an atom. Due to this higher s than silicon, electronics made out of it can operate at higher temperatures, voltages, and frequencies.
Silicon is one of the most widely used semiconductor materials, boasting an energy bandgap of 1.12eV. In comparison, silicon carbide boasts nearly three times greater bandgap at 3.26eV allowing it to accommodate higher voltages – one reason it has gained so much prominence as an option in electric vehicle batteries.
SiC’s ability to withstand high voltages allows its components to be made smaller and lighter, increasing a car’s fuel efficiency and battery range while simultaneously decreasing active cooling systems that add size and weight to its design.
Silicon carbide’s hardness and other properties make it attractive in industrial manufacturing, but also automotive applications. Silicon carbide could extend driving range for electric vehicles by being utilized within higher voltage applications like an inverter system that converts AC current to DC current; using higher s in an inverter increases energy conversion efficiency which may translate to better battery range without over dependence on components like battery management systems.