Siliciumkarbid Diamant

Silicon carbide is extremely hard, yet still less so than diamond. But it still ranks second as an extremely hard material.

Porous carbon-bonded diamond preforms undergo infiltration by infusing silicon through capillary force at temperatures exceeding its melting point, whereupon the carbon binder transforms into graphite.

Termisk ledningsevne

Silicon carbide diamond is an extremely high-temperature material with excellent thermal conductivity, used widely across electrical, electronic, and industrial engineering fields. Applications include cooling and heating semiconductors, transistors, and power LEDs as well as LED display lighting applications. Thermal conductivity for SiC/diamond composites depends upon several factors including their amount and size of diamond, composition of their binder material and structure of their interfaces between components as well as impact of graphitic interlayer on thermal conductivity of this material.

Since last decade, creating highly wear-resistant materials with excellent thermal conductivity has been an ongoing goal of research and development. “Silicon carbide diamond” materials can be produced through infiltration of liquid silicon through capillary forces at temperatures exceeding 1425 degC to form cubic b-SiC structures that could replace traditional steel materials as bearings, seals or inliners in industrial applications.

For optimal thermal conductivity in SiC/diamond composites, bimodal distribution of diamond grains of various sizes and fractions may be used to increase thermal conductivity. Bimodal systems offer significantly greater thermal conductivity compared to monomodal systems due to having graphitic atomic layers between diamond grains and their host matrix of b-SiC matrix material.

Additionally, graphitic atomic layers are aligned perpendicularly to the interface, creating bimodal systems with relatively large surface areas which increase thermal conductivity. Thermal conductivity increases even further if diamond is sintered at higher temperatures or held for shorter holding times during silicon infiltration – increasing it beyond that of pure b-SiC! Furthermore, thermal conductivity of materials also depends on their amount of free silicon and diamond.

Hårdhed

Silicon carbide, composed of silicon and carbon atoms, has an outstanding Mohs hardness of 9.5 and thus ranks second only to diamond in terms of hardness. Due to its strength and durability, silicon carbide finds numerous industrial uses.

Silicon carbide shares many of the same properties with diamond, including its crystal structure which is tetrahedral – four atoms from each element share one face-centered cubic lattice to form strong covalent bonds similar to diamond’s strong tetrahedral bonds – as well as high tensile strength and low coefficient of friction, making both materials great workpiece materials.

Silicon carbide can be produced using several techniques, with synthetic silicon carbide produced through the smelting of quartz sand, petroleum coke (or coal coke), wood chips or other raw materials in high temperature furnaces. Once created, silicon carbide exhibits hardness, has an elevated melting point and resists oxidation even under extreme temperature conditions.

Silicon carbide has many practical uses for industry. One such application is in abrasives. Thanks to its exceptional resistance and strength properties, silicon carbide makes an indispensable part of sandpapers, grinding wheels and cutting tools. Silicon carbide also finds use as an insulation component in industrial furnaces as well as wear resistant parts on pumps and rocket engines and semiconducting substrates used for light emitting diodes (LED).

There are various methods of producing silicon carbide. Traditional techniques involve using a sintering process in which powdered silicon and carbon is combined in a high-pressure melt to form a sintered block of silicon carbide that can then be cut to desired shapes and sizes. Another alternative involves reacting liquid silicon with porous graphite; this creates black synthetic moissanite which has some of the same mechanical properties without being as costly.

Specially produced silicon carbide-bonded diamond materials with graphitic interlayers at their interface have been found to boast exceptionally high strengths, exceeding even that of graphite free diamond/SiC interfaces, though whether this is down to interfacial graphitic layers is unclear.

Kemisk stabilitet

Silicon carbide diamonds are extremely resilient materials with excellent chemical stability, making them suitable for wear applications such as seals, inliners and nozzles. Furthermore, these diamonds make great cutting tools. Due to their strong crystal structure and good hardness properties, machining silicon carbide diamonds is relatively straightforward compared with many other hard materials and they also possess low coefficient of friction, making it suitable for industrial uses.

Silicon carbide diamonds have seen rapid development due to increased wear resistance requirements. Silicon carbide, an inorganic compound consisting of carbon and silicon with hexagonal crystal structure, can be produced in various shapes and sizes. Edward Goodrich Acheson created the first silicon carbide compound in 1891 by heating together clay and powdered coke in an iron bowl until blue crystals formed that were known as carborundum – Acheson believed this material would have higher value than coal as it could be used to make metals.

Silicon carbide differs greatly from pure diamond in that it has greater stability under high temperature conditions and has a low coefficient of friction, while being significantly cheaper. Therefore, silicon carbide has become the go-to material for industrial uses.

When used as bedding powder for diamond-siC preforms, a-Si3N4 bedding powder prevents silicon carbide formation and the formation of corporation layers – thus greatly increasing strength of diamond-siC interface over conventional samples embedded in molten silicon.

However, the exact nature of these interfaces remains largely unexplained. It could be the result of weaker bonds between graphitic planes or different phases at the interface which require further research to fully comprehend.

Energy dispersive X-ray spectrometry (EDX) was employed to assess the atomic density distribution in an amorphous layer made of 3 C-SiC/diamond material. A stepwise reduction was observed in intensity profiles for carbon and silicon atoms near their as-bonded interface, with carbon showing less steep slope. Silicon showed slightly concave density profiles while carbon’s were more gradual.

Microstructure

Diamonds are natural gems formed over millions of years, yet their production can be done synthetically for much less money in a laboratory. Silicon carbide, another synthetic gemstone with similar properties but much lower costs is much more durable and cost-effective. Its high refractive index enables it to reflect light more effectively than other gems while its durability makes it suitable for everyday wear. Furthermore, its low melting point means it can withstand both high temperatures and chemicals without cracking under pressure.

Microstructure of diamond-silicon carbide composites is typically comprised of interpenetrating three-dimensional networks composed of SiC and diamond. Particle size and morphology determines the final structure of triple junction silicon carbides; typically, graphitic interface atomic layers orient perpendicularly toward the diamond/SiC surface to form tight bonds with it – their thickness typically being much less than bond length between silicon carbide atoms and diamond atomic layers.

For optimal thermal conductivity of silicon carbide diamond, it is critical to understand how its atoms interact. A synchrotron X-ray beam can be used to examine diamond-silicon carbide interfaces and their structural parameters and their interaction. Results showed weak interparticle interactions; contact areas between diamond and SiC particles contain glassy carbon layers, graphitic boundary layers and micropores – an indication of poor thermal conductivity of diamond.

SiC and diamond interact closely, yet its strength also depends on its microstructure. This microstructure consists of a three-dimensional network of diamond and silicon carbide particles with only minimal graphitic interlayer coverage across its surface area; furthermore, this microstructure also determines mechanical properties such as fracture resistance.

Strength of a cantilever sample increases as more diamond/SiC interfaces tilt toward its loaded end, as shown by molecular dynamics simulations of parallel interfaces. A specimen with 40 nanometer tilt has proven particularly strong.