Different Types of Silicon Carbide

Silicon carbide ceramics are some of the hardest and toughest in existence, often utilized as hard abrasives in combination with hardwearing applications like pipe liners and flow control chokes to withstand wear-and-tear, wear resistance parts as well as bearings or mechanical seals. Its hardness also lends it to use in wear resistant pipe coating applications as well. Silicon carbide also serves well in bearing applications as mechanical seals.

Scientists have long attempted to make two-dimensional (2D) silicon carbide, but this process has proven challenging, due to bulk SiC not being van der Waals layered material.

Nitride bonded

Nitride-bonded silicon carbide (NBSiC) is an advanced ceramic composite material with unique properties such as thermal shock resistance, high-temperature strength, and wear resistance. NBSiC is made by bonding silicon carbide grains to a nitride ceramic phase to form a dense and durable material which can be easily formed into complex shapes. NBSiC has become an increasingly popular choice for applications requiring exceptional performance under harsh conditions; examples of its use include cyclone liners for mineral processing plants; chemical plant equipment such as pumps valves nozzles; as well as cast refractory materials.

NBSiC is a refractory material comprised of highly covalent silicon carbide-to-nitride ceramic bonds that resist oxidation at higher temperatures. Due to its superior abrasion resistance and thermal shock resistance, NBSiC makes an excellent choice for applications operating above 1375degC as it can withstand both pressures as well as being made into nearly net shapes without needing further grinding/machining after firing. NBSiC can often serve as an economical replacement for sintered pure silicon carbides due to these traits.

Nitriding of granular silicon carbide requires applying a nitrogen-containing compound in a furnace with controlled temperature and pressure levels, followed by heating at around 1375degC to initiate the reaction quickly resulting in compact, dense refractory materials with very strong bonds. Once complete, this process yields compact dense materials with extremely strong bonds for reuse as refractories or wear resistant components.

Attempts at producing bonds for silicon carbide particles that would achieve both an extremely high hot strength and resistance to temperature fluctuations have met with only partial success. Clays and other ingredients used to form porcelain type bonds produced bodies with excellent abrasion resistance but not sufficient refractory strength at higher temperatures; while glassy bonds were created which offered good spalling resistance but not sufficient resistance against oxidation for extended useful life.

This invention provides a novel method of producing silicon carbide bodies with characteristics mentioned above. Silicon carbide is embedded into a mixture of coke and sand and fired at 1375degC, whereupon substantial all of it will be converted to silicon nitride by means of nitrogen from its embedding mixture; this action occurs prior to any free oxygen from air reaching embedded articles and likely continues long after removal from firing furnace.

Oxide bonded

Silicon carbide (SiC) is an extremely hard synthetic material composed of silicon and carbon. While SiC occurs naturally as the extremely rare mineral moissanite, it has been mass produced as powder and crystal since 1893 for use as an abrasive. SiC can also be bonded together into extremely hard ceramics; additionally it acts as support material for heterogeneous catalysts. Two polymorphs exist: alpha SiC features hexagonal crystal structure similar to Wurtzite while beta SiC features zinc blende structure.

Reaction bonded SiC (RB SiC) is a composite material consisting of silicon carbide particles held together by a ceramic matrix, typically costing less than sintered SiC and offering excellent corrosion and wear resistance at temperatures up to 1500deg C. Furthermore, it can also be pressed into shapes for use as refractories; hence the moniker refractory grade SiC or Calsic RB.

Reacting coarse and medium grained SiC powders with 5-15% aluminosilicate binder in air produces lightweight SiC materials with superior melting points, thermal conductivities and porosities compared to sintered versions. The resultant material has a lower melting point than sintered versions but still features excellent thermal conductivity, high melting point temperatures, low porosity rates and very strong load-carrying capacities at elevated temperatures that exceed those seen with oxide-bonded SiC products as well as resistance against metals and acids.

Oxide-bonded SiC is an ideal material choice for high temperature applications like kilns and furnaces, due to its superior mechanical strength, thermal shock resistance and wide variety of sizes and shapes to meet your application requirements. It boasts excellent flexural strength which withstands impact forces as well as its high flexural strength for abrasion stress tolerance while its thermal shock resistance ensures rapid temperature shifts are handled without issue. Available in various shapes sizes profiles – Oxide-bonded SiC can meet all these criteria in style!

Self-bonded

Reaction Bonded Silicon Carbide (RBSC) is an impregnated sintered silica material with excellent corrosion and wear resistance, manufactured into various shapes, sizes and tolerances by Calix Ceramics under its trade name Calsic RB. Production of this material involves infiltrating liquid silicon into porous carbon materials packed in any desired shape to create open or dense structures for various uses, such as pumps, mechanical seals and bearings; or larger wear components like pipe liners and flow control chokes.

Sintering process for RBSCs is similar to that used with nitride-bonded types, but requires higher temperatures. Care must be taken in selecting carbon grades and components of Si melt in order to reduce excessive porosity.

Another issue associated with RBSC is its high content of free silicon, which decreases mechanical properties and may lower bending strength. To address this, adding boron powder may help increase density while simultaneously improving bending strength.

As part of sintering RBSC refractories, it is vital that they are not exposed to an oxidising atmosphere; otherwise, any free silicon present will interact with oxygen and form a thick oxide layer, detracting from its mechanical properties and creating mechanical problems for users. There have been various methods employed to decrease free silicon content such as infiltration or incineration of the material.

At different temperatures, scientists studied infiltration of Si melt into RBSC green bodies at different temperatures. Their investigations demonstrated that its penetration is dependent upon temperature and contact angle between carbon and Si melt – at lower temperatures it doesn’t penetrate, while at higher ones it does so only partially.

Due to the large particle sizes present in an RBSC green body and less dense b-SiC than its a-SiC counterparts, carbon black should be used instead of graphite to increase relative density of its relative composition.

Purebide®

Purebide(r), produced by Saint-Gobain, is a series of silicon carbide ceramics used in various industrial applications due to their unique thermomechanical and chemical properties. Available in an assortment of shapes and sizes, these ceramics have the capacity to withstand high temperatures as well as voltage spikes – making them suitable for semiconductor electronics such as light-emitting diodes and detectors as well as producing highly polished parts like grinding wheels and abrasive materials.

Reaction-bonded SiC is considerably stronger and more flexible than its nitride bonded counterpart, thanks to the addition of carbon and plasticizer. Reaction-bonded silicon carbide can be produced by mixing finely divided silicon carbide powder with carbon and plasticizer, then shaping this mixture into desired shapes before burning off plasticizer, before infusing with liquid or gaseous silicon at high temperature and reacting with carbon to form additional silicon carbide particles which bind securely with existing particles of SiC.

Reaction-bonded silicon carbide boasts superior impact resistance, wear resistance and abrasion resistance as well as the ability to withstand temperatures up to 2500 deg F without oxidizing, making it an invaluable material in many acidic, caustic, corrosive, abrasive environments – including pump seals and bearings, gas turbine components and mixing nozzles; it has even been found in bulletproof vests among other high-performance applications.

SiC is hard, yet not as brittle as diamond or boron nitride. This strength stems from its unique tetrahedral structure with covalent bonding between adjacent atoms that is much stronger than van der Waals-bonded layers structures; making sintering difficult but manageable by using aids such as alumina or boron as well as altering conditions during sintering.

Silicon carbide is currently the third hardest material, behind diamond and boron nitride, making it highly suitable for high performance applications. BepiColombo uses blocking silicon carbide diodes from Alter Technology which are capable of withstanding harsh space environments, making this material an excellent candidate for use on other space missions that demand lightweight yet robust equipment.