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Sodium Tungsten Bronze
Sodium tungsten bronze is a form of insertion compound with the formula Na''x''WO3, where ''x'' is equal to or less than 1. So named because of its metallic lustre, its electrical properties range from semiconducting to metallic depending on the concentration of sodium ions present; it can also exhibit superconductivity. History Prepared in 1823 by the chemist Friedrich Wöhler, sodium tungsten bronze was the first alkali metal bronze to be discovered. Tungsten bronzes owe some of their properties to the relative stability of the tungsten(V) cation that is formed. A similar family of molybdenum bronzes may have been discovered in 1885 by Alfred Stavenhagen and E. Engels, but they are formed in a very narrow range of temperatures and were not reported again until the 1960s. Properties Sodium tungsten bronze, like other tungsten bronzes, is resistant to chemical reaction under both acidic and basic conditions. Colour is dependent upon the proportion of sodium in the compound, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sodium Tungsten Bronze
Sodium tungsten bronze is a form of insertion compound with the formula Na''x''WO3, where ''x'' is equal to or less than 1. So named because of its metallic lustre, its electrical properties range from semiconducting to metallic depending on the concentration of sodium ions present; it can also exhibit superconductivity. History Prepared in 1823 by the chemist Friedrich Wöhler, sodium tungsten bronze was the first alkali metal bronze to be discovered. Tungsten bronzes owe some of their properties to the relative stability of the tungsten(V) cation that is formed. A similar family of molybdenum bronzes may have been discovered in 1885 by Alfred Stavenhagen and E. Engels, but they are formed in a very narrow range of temperatures and were not reported again until the 1960s. Properties Sodium tungsten bronze, like other tungsten bronzes, is resistant to chemical reaction under both acidic and basic conditions. Colour is dependent upon the proportion of sodium in the compound, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Kelvin
The kelvin, symbol K, is the primary unit of temperature in the International System of Units (SI), used alongside its prefixed forms and the degree Celsius. It is named after the Belfast-born and University of Glasgow-based engineer and physicist William Thomson, 1st Baron Kelvin (1824–1907). The Kelvin scale is an absolute thermodynamic temperature scale, meaning it uses absolute zero as its null (zero) point. Historically, the Kelvin scale was developed by shifting the starting point of the much-older Celsius scale down from the melting point of water to absolute zero, and its increments still closely approximate the historic definition of a degree Celsius, but since 2019 the scale has been defined by fixing the Boltzmann constant to be exactly . Hence, one kelvin is equal to a change in the thermodynamic temperature that results in a change of thermal energy by . The temperature in degree Celsius is now defined as the temperature in kelvins minus 273.15, meaning t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sodium Compounds
Sodium atoms have 11 electrons, one more than the stable configuration of the noble gas neon. As a result, sodium usually forms ionic compounds involving the Na+ cation. Sodium is a reactive alkali metal and is much more stable in ionic compounds. It can also form intermetallic compounds and organosodium compounds. Sodium compounds are often soluble in water. Metallic sodium Metallic sodium is generally less reactive than potassium and more reactive than lithium. Sodium metal is highly reducing, with the standard reduction potential for the Na+/Na couple being −2.71 volts, though potassium and lithium have even more negative potentials. The thermal, fluidic, chemical, and nuclear properties of molten sodium metal have caused it to be one of the main coolants of choice for the fast breeder reactor. Such nuclear reactors are seen as a crucial step for the production of clean energy. Salts and oxides Sodium compounds are of immense commercial importance, being particularly centra ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Non-stoichiometric Compounds
In chemistry, non-stoichiometric compounds are chemical compounds, almost always solid inorganic compounds, having elemental composition whose proportions cannot be represented by a ratio of small natural numbers (i.e. an empirical formula); most often, in such materials, some small percentage of atoms are missing or too many atoms are packed into an otherwise perfect lattice work. Contrary to earlier definitions, modern understanding of non-stoichiometric compounds view them as homogeneous, and not mixtures of stoichiometric chemical compounds. Since the solids are overall electrically neutral, the defect is compensated by a change in the charge of other atoms in the solid, either by changing their oxidation state, or by replacing them with atoms of different elements with a different charge. Many metal oxides and sulfides have non-stoichiometric examples; for example, stoichiometric iron(II) oxide, which is rare, has the formula , whereas the more common material is nonstoichi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Alkali Metals
The alkali metals consist of the chemical elements lithium (Li), sodium (Na), potassium (K),The symbols Na and K for sodium and potassium are derived from their Latin names, ''natrium'' and ''kalium''; these are still the origins of the names for the elements in some languages, such as German and Russian. rubidium (Rb), caesium (Cs), and francium (Fr). Together with hydrogen they constitute group 1, which lies in the s-block of the periodic table. All alkali metals have their outermost electron in an s-orbital: this shared electron configuration results in their having very similar characteristic properties. Indeed, the alkali metals provide the best example of group trends in properties in the periodic table, with elements exhibiting well-characterised homologous behaviour. This family of elements is also known as the lithium family after its leading element. The alkali metals are all shiny, soft, highly reactive metals at standard temperature and pressure and readily lose ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Melt
Melt may refer to: Science and technology * Melting, in physics, the process of heating a solid substance to a liquid * Melt (manufacturing), the semi-liquid material used in steelmaking and glassblowing * Melt (geology), magma ** Melt inclusions, a feature of igneous rock * Meltwater, water released from the thawing of snow and ice * MLT framework, a software test tool for the Media Lovin' Toolkit * Melt, one of the former names for the American social media app Gas. Music * Melt! Festival, an annual music festival at Ferropolis in Germany Albums * ''Melt'' (Straitjacket Fits album), a 1990 album by Straitjacket Fits * ''Melt'' (Rascal Flatts album), a 2002 album by Rascal Flatts * ''Melt'', a 2018 extended play by Shaed, featuring the song "Trampoline" * ''Melt'' (Peter Gabriel album), an alternative name of the third self-titled Peter Gabriel album, from 1980 Songs * "Melt!" (Siouxsie and the Banshees song), a 1982 song by Siouxsie and the Banshees * "Melt" (Melanie C son ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hydrogen Gas
Hydrogen is the chemical element with the symbol H and atomic number 1. Hydrogen is the lightest element. At standard conditions hydrogen is a gas of diatomic molecules having the formula . It is colorless, odorless, tasteless, non-toxic, and highly combustible. Hydrogen is the most abundant chemical substance in the universe, constituting roughly 75% of all normal matter.However, most of the universe's mass is not in the form of baryons or chemical elements. See dark matter and dark energy. Stars such as the Sun are mainly composed of hydrogen in the plasma state. Most of the hydrogen on Earth exists in molecular forms such as water and organic compounds. For the most common isotope of hydrogen (symbol 1H) each atom has one proton, one electron, and no neutrons. In the early universe, the formation of protons, the nuclei of hydrogen, occurred during the first second after the Big Bang. The emergence of neutral hydrogen atoms throughout the universe occurred about 370,000 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tungsten Trioxide
Tungsten(VI) oxide, also known as tungsten trioxide is a chemical compound of oxygen and the transition metal tungsten, with formula WO3. The compound is also called tungstic anhydride, reflecting its relation to tungstic acid . It is a light yellow crystalline solid. Tungsten(VI) oxide occurs naturally in the form of hydrates, which include minerals: tungstite WO3·H2O, meymacite WO3·2H2O and hydrotungstite (of the same composition as meymacite, however sometimes written as H2WO4). These minerals are rare to very rare secondary tungsten minerals. History In 1841, a chemist named Robert Oxland gave the first procedures for preparing tungsten trioxide and sodium tungstate. He was granted patents for his work soon after, and is considered to be the founder of systematic tungsten chemistry. Structure and properties The crystal structure of tungsten trioxide is temperature dependent. It is tetragonal at temperatures above 740 °C, orthorhombic from 330 to 740 °C, monoclini ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sodium Tungstate
Sodium tungstate is the inorganic compound with the formula Na2WO4. This white, water-soluble solid is the sodium salt of tungstic acid. It is useful as a source of tungsten for chemical synthesis. It is an intermediate in the conversion of tungsten ores to the metal. Preparation and structure Sodium tungstate is obtained by digestion of tungsten ores, the economically important representatives of which are tungstates, in base. Illustrative is the extraction of sodium tungstate from wolframite: :Fe/MnWO4 + 2 NaOH + 2 H2O → Na2WO4·2H2O + Fe/Mn(OH)2 Scheelite is treated similarly using sodium carbonate. Sodium tungstate can also be produced by treating tungsten carbide with a mixture of sodium nitrate and sodium hydroxide in a fusion process which overcomes the high exothermicity of the reaction involved. Several polymorphs of sodium tungstate are known, three at only one atmosphere pressure. They feature tetrahedral orthotungstate dianions but differ in the packi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Perovskite (structure)
A perovskite is any material with a crystal structure following the formula ABX3, which was first discovered as the mineral called perovskite, which consists of calcium titanium oxide (CaTiO3). The mineral was first discovered in the Ural mountains of Russia by Gustav Rose in 1839 and named after Russian mineralogist L. A. Perovski (1792–1856). 'A' and 'B' are two positively charged ions (i.e. cations), often of very different sizes, and X is a negatively charged ion (an anion, frequently oxide) that bonds to both cations. The 'A' atoms are generally larger than the 'B' atoms. The ideal cubic structure has the B cation in 6-fold coordination, surrounded by an octahedron of anions, and the A cation in 12-fold cuboctahedral coordination. Additional perovskite forms may exist where either/both the A and B sites have a configuration of A1x-1A2x and/or B1y-1B2y and the X may deviate from the ideal coordination configuration as ions within the A and B sites undergo changes in thei ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Perovskite
Perovskite (pronunciation: ) is a calcium titanium oxide mineral composed of calcium titanate (chemical formula ). Its name is also applied to the class of compounds which have the same type of crystal structure as (XIIA2+VIB4+X2−3), known as the perovskite structure. Many different cations can be embedded in this structure, allowing the development of diverse engineered materials. History The mineral was discovered in the Ural Mountains of Russia by Gustav Rose in 1839 and is named after Russian mineralogist Lev Perovski (1792–1856). Perovskite's notable crystal structure was first described by Victor Goldschmidt in 1926 in his work on tolerance factors. The crystal structure was later published in 1945 from X-ray diffraction data on barium titanate by Helen Dick Megaw. Occurrence Found in the Earth's mantle, perovskite's occurrence at Khibina Massif is restricted to the silica under-saturated ultramafic rocks and foidolites, due to the instability in a paragenesis ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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