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Hafnium Carbonitride
Hafnium carbonitride (HfCN) is a mixed anion chemical compound of hafnium, carbon and nitrogen. With a melting point of above 4,000 °C, it is the most refractory compound known. No other substance has a higher melting point at atmospheric pressure. In 2015, atomistic simulations predicted that a Hf-C-N material could have a melting point exceeding Ta4Hf1C5 and hafnium carbide Hafnium carbide ( Hf C) is a chemical compound of hafnium and carbon. Previously the material was estimated to have a melting point of about 3,900 °C. More recent tests have been able to conclusively prove that the substance has an even hig ... by 200 °C. This would later be proven in experimental testing conducted in 2020 by the National University of Science and Technology (NUST) in Moscow. Samples of both hafnium carbide and hafnium carbonitride were tested in the same environment in which hafnium carbonitride was shown to have a melting point exceeding 4,000 °C and higher than that of ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cubic Crystal System
In crystallography, the cubic (or isometric) crystal system is a crystal system where the Crystal_structure#Unit_cell, unit cell is in the shape of a cube. This is one of the most common and simplest shapes found in crystals and minerals. There are three main varieties of these crystals: *Primitive cubic (abbreviated ''cP'' and alternatively called simple cubic) *Body-centered cubic (abbreviated ''cI'' or bcc) *Face-centered cubic (abbreviated ''cF'' or fcc, and alternatively called Close-packing_of_equal_spheres, ''cubic close-packed'' or ccp) Each is subdivided into other variants listed below. Although the ''unit cells'' in these crystals are conventionally taken to be cubes, the primitive_cell, primitive unit cells often are not. Bravais lattices The three Bravais lattices in the cubic crystal system are: The primitive cubic lattice (cP) consists of one Lattice_(group), lattice point on each corner of the cube; this means each simple cubic unit cell has in total one latt ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pearson Symbol
The Pearson symbol, or Pearson notation, is used in crystallography as a means of describing a crystal structure, and was originated by W. B. Pearson. The symbol is made up of two letters followed by a number. For example: * Diamond structure, ''cF''8 * Rutile structure, ''tP''6 The two (italicised) letters specify the Bravais lattice. The lower-case letter specifies the crystal family, and the upper-case letter the centering type. The number at the end of the Pearson symbol gives the number of the atoms in the conventional unit cell.Nomenclature of Inorganic Chemistry IUPAC Recommendations 2005 IR-3.4.4, pp. 49–51; IR-11.5, pp. 241–242. |
Mixed Anion Compound
Mixed anion compounds, heteroanionic materials or mixed anion materials are chemical compounds containing cations and more than one kind of anion. The compounds contain a single phase, rather than just a mixture. Use in materials science By having more than one anion, many more compounds can be made, and properties tuned to desirable values. In terms of optics, properties include laser damage threshold, refractive index, birefringence, absorption particularly in the ultraviolet or near infrared, non-linearity. Mechanical properties can include ability to grow a large crystal, ability to form a thin layer, strength, or brittleness. Thermal properties can include melting point, thermal stability, phase transition temperatures, Thermal expansion coefficient. For electrical properties, electric conductivity, band gap, superconducting transition temperature piezoelectricity, pyroelectricity, ferromagnetism, dielectric constant, charge-density wave transition can be adjusted. Pro ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hafnium
Hafnium is a chemical element with the symbol Hf and atomic number 72. A lustrous, silvery gray, tetravalent transition metal, hafnium chemically resembles zirconium and is found in many zirconium minerals. Its existence was predicted by Dmitri Mendeleev in 1869, though it was not identified until 1923, by Dirk Coster and George de Hevesy, making it the penultimate stable element to be discovered (the last being rhenium in 1925). Hafnium is named after , the Latin name for Copenhagen, where it was discovered. Hafnium is used in filaments and electrodes. Some semiconductor fabrication processes use its oxide for integrated circuits at 45 nanometers and smaller feature lengths. Some superalloys used for special applications contain hafnium in combination with niobium, titanium, or tungsten. Hafnium's large neutron capture cross section makes it a good material for neutron absorption in control rods in nuclear power plants, but at the same time requires that it be removed from th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Carbide
In chemistry, a carbide usually describes a compound composed of carbon and a metal. In metallurgy, carbiding or carburizing is the process for producing carbide coatings on a metal piece. Interstitial / Metallic carbides The carbides of the group 4, 5 and 6 transition metals (with the exception of chromium) are often described as interstitial compounds. These carbides have metallic properties and are refractory. Some exhibit a range of stoichiometries, being a non-stoichiometric mixture of various carbides arising due to crystal defects. Some of them, including titanium carbide and tungsten carbide, are important industrially and are used to coat metals in cutting tools. The long-held view is that the carbon atoms fit into octahedral interstices in a close-packed metal lattice when the metal atom radius is greater than approximately 135 pm: *When the metal atoms are cubic close-packed, (ccp), then filling all of the octahedral interstices with carbon achieves 1:1 stoich ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nitride
In chemistry, a nitride is an inorganic compound of nitrogen. The "nitride" anion, N3- ion, is very elusive but compounds of nitride are numerous, although rarely naturally occuring. Some nitrides have a find applications, such as wear-resistant coatings (e.g., titanium nitride, TiN), hard ceramic materials (e.g., silicon nitride, Si3N4), and semiconductors (e.g., gallium nitride, GaN). The development of GaN-based light emitting diodes was recognized by the 2014 Nobel Prize in Physics. Metal nitrido complexes are also common. Synthesis of inorganic metal nitrides is challenging because nitrogen gas (N2) is not very reactive at low temperatures, but it becomes more reactive at higher temperatures. Therefore, a balance must be achieved between the low reactivity of nitrogen gas at low temperatures and the entropy driven formation of N2 at high temperatures. However, synthetic methods for nitrides are growing more sophisticated and the materials are of increasing technological re ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tantalum Hafnium Carbide
Tantalum hafnium carbide is a refractory chemical compound with a general formula , which can be considered as a solid solution of tantalum carbide and hafnium carbide. Properties Individually, tantalum and hafnium carbide have the highest melting points among the binary compounds, and , respectively, and their "alloy" with a composition Ta4HfC5 has an melting point of . Very few measurements of melting point in tantalum hafnium carbide have been reported, because of the obvious experimental difficulties at extreme temperatures. A 1965 study of the TaC-HfC solid solutions at temperatures 2,225–2,275 °C found a minimum in the vaporization rate and thus maximum in the thermal stability for Ta4HfC5. This rate was comparable to that of tungsten and was weakly dependent on the initial density of the samples, which were sintered from TaC-HfC powder mixtures, also at 2,225–2,275 °C. In a separate study, Ta4HfC5 was found to have the minimum oxidation rate among the Ta ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hafnium Carbide
Hafnium carbide ( Hf C) is a chemical compound of hafnium and carbon. Previously the material was estimated to have a melting point of about 3,900 °C. More recent tests have been able to conclusively prove that the substance has an even higher melting point of 3,958 °C exceeding those of tantalum carbide and tantalum hafnium carbide which were both previously estimated to be higher. However, it has a low oxidation resistance, with the oxidation starting at temperatures as low as 430 °C. Experimental testing in 2018 confirmed the higher melting point yielding a result of 3,982 (±30°C) with a small possibility that the melting point may even exceed 4,000°C. Atomistic simulations conducted in 2015 predicted that a Hf-C-N material could have a melting point exceeding even that of hafnium carbide. More recent experimental evidence gathered in 2020 confirmed that hafnium carbonitride did indeed have a higher melting point exceeding 4,000 °C. Hafnium carbide ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Forbes
''Forbes'' () is an American business magazine owned by Integrated Whale Media Investments and the Forbes family. Published eight times a year, it features articles on finance, industry, investing, and marketing topics. ''Forbes'' also reports on related subjects such as technology, communications, science, politics, and law. It is based in Jersey City, New Jersey. Competitors in the national business magazine category include ''Fortune'' and ''Bloomberg Businessweek''. ''Forbes'' has an international edition in Asia as well as editions produced under license in 27 countries and regions worldwide. The magazine is well known for its lists and rankings, including of the richest Americans (the Forbes 400), of the America's Wealthiest Celebrities, of the world's top companies (the Forbes Global 2000), Forbes list of the World's Most Powerful People, and The World's Billionaires. The motto of ''Forbes'' magazine is "Change the World". Its chair and editor-in-chief is Steve Fo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hafnium Compounds
Hafnium compounds are compounds containing the element hafnium (Hf). Due to the lanthanide contraction, the ionic radius of hafnium(IV) (0.78 ångström) is almost the same as that of zirconium(IV) (0.79 angstroms). Consequently, compounds of hafnium(IV) and zirconium(IV) have very similar chemical and physical properties. Hafnium and zirconium tend to occur together in nature and the similarity of their ionic radii makes their chemical separation rather difficult. Hafnium tends to form inorganic compounds in the oxidation state of +4. Halogens react with it to form hafnium tetrahalides. At higher temperatures, hafnium reacts with oxygen, nitrogen, carbon, boron, sulfur, and silicon. Some compounds of hafnium in lower oxidation states are known. Halides Hafnium(IV) fluoride (HfF4) is a white crystalline powder. It has a monoclinic crystal structure, with space group C2/c (No.15), and lattice constants ''a'' = 1.17 nm, ''b'' = 0.986 nm and ''c'' = 0.764 nm. Hafnium(IV) c ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Carbides
In chemistry, a carbide usually describes a compound composed of carbon and a metal. In metallurgy, carbiding or carburizing is the process for producing carbide coatings on a metal piece. Interstitial / Metallic carbides The carbides of the group 4, 5 and 6 transition metals (with the exception of chromium) are often described as interstitial compounds. These carbides have metallic properties and are refractory. Some exhibit a range of stoichiometries, being a non-stoichiometric mixture of various carbides arising due to crystal defects. Some of them, including titanium carbide and tungsten carbide, are important industrially and are used to coat metals in cutting tools. The long-held view is that the carbon atoms fit into octahedral interstices in a close-packed metal lattice when the metal atom radius is greater than approximately 135 pm: *When the metal atoms are cubic close-packed, (ccp), then filling all of the octahedral interstices with carbon achieves 1:1 stoich ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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