Key Properties and Applications of Silicon Carbide in Chemistry
Silicon carbide is also commonly said as Carborundum, which is a compound of both silicon and carbon. Silicon carbide can be described as a semiconductor material as an emerging material for the applications of semiconductor devices. Silicon carbide was discovered in 1891 by Pennsylvanian Edward Acheson. It is one of the essential industrial ceramic materials. It also plays a key role in the industrial revolution and is still used widely as a steel additive, abrasive and structural ceramic.
The IUPAC Name of Silicon Carbide is given as Methanidylidynesilanylium.
Properties of Silicon Carbide
Physical Properties of Silicon Carbide – SiC
Chemical Properties of Silicon Carbide – SiC
Silicon Carbide possesses interesting electrical properties because of its characteristics of semiconductors, the resistance of various compositions differing by as seven orders of magnitude.
Resistant to many organic and inorganic acids, salts, and alkalis in a variety of concentrations except to acid fluorides and hydrofluoric acid.
Silicon Carbide Structure – SiC
(Image to be added soon)
Natural Occurrence
Naturally-occurring moissanites are present only in small numbers in specific forms of meteorites and in kimberlite and corundum deposits. Virtually all the silicon carbide sold in the world is plastic, like moissanite jewellery. In 1893, natural moissanite was first found in Arizona as a small component of the Canyon Diablo meteorite by Dr Ferdinand Henri Moissan, after whom the material was named in 1905. The naturally occurring SiC discovered by Moissan was initially disputed due to his sample may have been contaminated by the silicon carbide saw blades that were already available on the market at that period.
While rare on the Earth, silicon carbide is defined remarkably as common in space. It is also a common form of stardust found around the carbon-rich stars, and the examples of this stardust have been found in pristine condition in unaltered (primitive) meteorites. The silicon carbide can also be found in space and meteorites are beta-polymorph, which is almost exclusively. The SiC grain analysis can be found in the Murchison meteorite, which is a carbonaceous chondrite meteorite and has revealed the anomalous isotopic ratios of silicon and carbon, indicating that these grains have originated outside the solar system.
Production
Because the natural moissanite is an extremely scarcest element, most of the silicon carbide is synthetic. Silicon carbide can be used as an abrasive and as a diamond simulant and semiconductor of gem-quality as well. The simplest process to manufacture the silicon carbide is to combine carbon and silica sand in electric resistance of an Acheson graphite furnace at a high temperature, raging from 1,600 °C (2,910 °F) and 2,500 °C (4,530 °F). The fine particles of SiO2 present in plant material (for example, rice husks) can be converted to SiC by heating the compound in the excess carbon from the organic material. The silica fume, a byproduct of producing ferrosilicon alloys and silicon metal, can also be converted to SiC by heating with graphite at a temperature of 1,500 °C (2,730 °F).
The material, which is formed in the Acheson furnace differs in purity, as per its distance from the graphite resistor heat source. Colourless, green, and pale yellow crystals have the highest purity and can be found closest to the resistor. The colour changes to black and blue at a greater distance from the resistor and these darker crystals are less pure. Aluminium and Nitrogen are the common impurities, and they affect the SiC's electrical conductivity.
Uses of Silicon Carbide
Abrasive and Cutting Tools
Silicon carbide is a popular abrasive in the arts in modern lapidary because of the low cost and durability of the material. Also, in the process of manufacturing, it is used for its hardness in the abrasive machining processes including honing, grinding, sandblasting, and water-jet cutting. Silicon carbide particles are laminated to paper to create grip tape on skateboards and sandpapers.
Automobile Parts
The carbon-carbon composite of Silicon-infiltrated is used for high performance "ceramic" brake disks since they can withstand extreme temperatures. Silicon also reacts with the graphite in the composite of carbon-carbon to form carbon-fibre-reinforced silicon carbide (C/SiC). These brake disks can be used on a few supercars, road-going sports cars, and other performance cars as well, including the Bugatti Veyron, Porsche Carrera GT, the McLaren P1, Ferrari, Bentley, Lamborghini, and a few Audi cars, which have a specific high-performance. Silicon carbide can also be used in a sintered form for diesel particulate filters. It is also used as an oil additive to reduce emissions, harmonics, and friction.
Foundry Crucibles
Silicon Carbide is used in crucibles for holding the melting metal in the applications of both small and large foundry.
FAQs on Silicon Carbide (SiC): Complete Chemistry Guide
1. What is silicon carbide (SiC)?
Silicon carbide, commonly known by its chemical formula SiC, is a synthetically produced crystalline compound of silicon and carbon. It is classified as a covalent network solid, where strong covalent bonds exist throughout the crystal, giving it exceptional hardness and a very high melting point. It is also commercially known as carborundum.
2. Describe the structure of silicon carbide and explain why it is so hard.
Silicon carbide has a crystal structure similar to that of a diamond. Each silicon atom is covalently bonded to four carbon atoms, and each carbon atom is bonded to four silicon atoms in a tetrahedral geometry. This arrangement forms a very strong, rigid, three-dimensional network. This extensive giant covalent structure is the primary reason for its extreme hardness, which is close to 9 on the Mohs scale, and its high melting point of around 2730°C.
3. What are the most important uses of silicon carbide in various industries?
Due to its unique properties, silicon carbide has several important industrial applications:
Abrasives: Its extreme hardness makes it an excellent material for grinding wheels, sandpaper, and high-pressure water jet cutting.
Refractory Materials: Its high melting point and thermal stability allow it to be used in furnace linings, kiln parts, and crucibles.
Semiconductors: SiC is used in high-power and high-frequency electronic devices, such as high-efficiency LEDs and power transistors, because it can operate at very high temperatures and voltages.
Structural Ceramics: It is used in car brakes, clutches, and even bulletproof vests due to its immense strength and durability.
4. How is silicon carbide prepared on a commercial scale?
Silicon carbide is commercially manufactured using the Acheson process. This method involves heating a mixture of high-purity silica (sand, SiO₂) and carbon (in the form of petroleum coke) to extremely high temperatures, typically between 1600–2500°C, in a large electric resistance furnace. The fundamental chemical reaction is: SiO₂(s) + 3C(s) → SiC(s) + 2CO(g).
5. Why is silicon carbide classified as an inorganic compound despite containing carbon?
Silicon carbide (SiC) is classified as an inorganic compound because it lacks the carbon-hydrogen (C-H) bonds that are the defining characteristic of organic compounds. Its properties, such as its rigid crystal structure, extreme hardness, high melting point, and chemical inertness, are typical of inorganic covalent network solids like diamond and silica, not organic molecules.
6. What makes silicon carbide chemically inert and insoluble in water?
Silicon carbide's chemical inertness is due to the immense strength and stability of the silicon-carbon (Si-C) covalent bonds that form its crystal lattice. A very large amount of energy is required to break these strong bonds. As a result, SiC does not react with most acids, alkalis, or other reagents under normal conditions and is completely insoluble in water and other common solvents. It is only attacked by molten alkalis at very high temperatures.
7. How does the structure of silicon carbide compare to that of diamond?
Both silicon carbide and diamond are covalent network solids with tetrahedral bonding. In diamond, every carbon atom is bonded to four other carbon atoms. In silicon carbide, every silicon atom is bonded to four carbon atoms, and vice-versa. While both are extremely hard, diamond is harder because the carbon-carbon (C-C) bond is stronger and shorter than the silicon-carbon (Si-C) bond, resulting in a more compact and rigid lattice.
