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Zirconium(IV) Fluoride
Zirconium(IV) fluoride describes members of a family inorganic compounds with the formula Zr F4(H2O)x. All are colorless, diamagnetic solids. Anhydrous Zirconium(IV) fluoride is a component of ZBLAN fluoride glass. Structure Three crystalline phases of ZrF4 have been reported, α (monoclinic), β (tetragonal, Pearson symbol tP40, space group P42/m, No 84) and γ (unknown structure). β and γ phases are unstable and irreversibly transform into the α phase at 400 °C. Zirconium(IV) fluoride forms several hydrates. The trihydrate has the structure . Preparation and reactions Zirconium fluoride can be produced by several methods. Zirconium dioxide reacts with hydrogen fluoride and hydrofluoric acid to afford the anhydrous and monohydrates: : The reaction of Zr metal reacts at high temperatures with HF as well: : Zirconium dioxide reacts at 200 °C with solid ammonium bifluoride to give the heptafluorozirconate salt, which can be converted to the tetrafluoride at 500 °C: ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Monoclinic
In crystallography, the monoclinic crystal system is one of the seven crystal systems. A crystal system is described by three Vector (geometric), vectors. In the monoclinic system, the crystal is described by vectors of unequal lengths, as in the orthorhombic system. They form a parallelogram prism (geometry), prism. Hence two pairs of vectors are perpendicular (meet at right angles), while the third pair makes an angle other than 90°. Bravais lattices Two monoclinic Bravais lattices exist: the primitive monoclinic and the base-centered monoclinic. For the base-centered monoclinic lattice, the primitive cell has the shape of an oblique rhombic prism;See , row mC, column Primitive, where the cell parameters are given as a1 = a2, α = β it can be constructed because the two-dimensional centered rectangular base layer can also be described with primitive rhombic axes. The length a of the primitive cell below equals \frac \sqrt of the conventional cell above. Crystal class ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ammonium Bifluoride
Ammonium bifluoride is an inorganic compound with the formula or . It is produced from ammonia and hydrogen fluoride. This colourless salt is a glass-industrial etching, etchant and an intermediate in a once-contemplated route to hydrofluoric acid. Structure Ammonium bifluoride, as its name indicates, contains an ammonium cation (), and a bifluoride (or hydrogen difluoride) anion (). The triatomic bifluoride anion features a strong three-center four-electron bond (specifically, a symmetrical hydrogen bond) with a bond energy greater than 155 kJ/mol, and an H-F length of 114 pm. In solid form (), ammonium biflouride is similar to other fluoride salts. Its crystal system is considered orthorhombic, with each cation coordinated with four anions in a tetrahedron (and vice versa). Hydrogen atoms in the ammonium ion form hydrogen bonds with the fluorine atoms, and in the resulting structure, N-H-F are roughly colinear. As a result of these hydrogen bonds, this crystal structure varie ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Advanced High-Temperature Reactor
A high-temperature gas-cooled reactor (HTGR) is a type of gas-cooled reactor, gas-cooled nuclear reactor which uses uranium fuel and graphite-moderated reactor, graphite moderation to produce very high nuclear reactor core, reactor core output temperatures. All existing HTGR reactors use helium coolant. The reactor core can be either a "prismatic block" (reminiscent of a conventional reactor core) or a "Pebble-bed reactor, pebble-bed" core. China Huaneng Group currently operates HTR-PM, a 250 MW HTGR power plant in Shandong province, China. The high operating temperatures of HTGR reactors potentially enable applications such as process heat or hydrogen production via the thermochemical sulfur–iodine cycle. A proposed development of the HTGR is the Generation IV reactor, Generation IV very-high-temperature reactor (VHTR) which would initially work with temperatures of 750 to 950 °C. History The use of a high-temperature, gas-cooled reactor for power production was pro ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Thorium Fuel Cycle
The thorium fuel cycle is a nuclear fuel cycle that uses an isotope of thorium, , as the fertile material. In the reactor, is transmuted into the fissile artificial uranium isotope which is the nuclear fuel. Unlike natural uranium, natural thorium contains only trace amounts of fissile material (such as ), which are insufficient to initiate a nuclear chain reaction. Additional fissile material or another neutron source is necessary to initiate the fuel cycle. In a thorium-fuelled reactor, absorbs neutrons to produce . This parallels the process in uranium breeder reactors whereby fertile absorbs neutrons to form fissile . Depending on the design of the reactor and fuel cycle, the generated either fissions in situ or is chemically separated from the used nuclear fuel and formed into new nuclear fuel. The thorium fuel cycle has several potential advantages over a uranium fuel cycle, including thorium's greater abundance, superior physical and nuclear properties, reduc ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Uranium-233
Uranium-233 ( or U-233) is a fissile isotope of uranium that is bred from thorium-232 as part of the thorium fuel cycle. Uranium-233 was investigated for use in nuclear weapons and as a Nuclear fuel, reactor fuel. It has been used successfully in experimental nuclear reactors and has been proposed for much wider use as a nuclear fuel. It has a half-life of 160,000 years. Uranium-233 is produced by the neutron irradiation of thorium-232. When thorium-232 absorbs a neutron, it becomes thorium-233, which has a half-life of only 22 minutes. Thorium-233 decays into protactinium-233 through beta decay. Protactinium-233 has a half-life of 27 days and beta decays into uranium-233; some proposed molten salt reactor designs attempt to physically isolate the protactinium from further neutron capture before beta decay can occur, to maintain the neutron economy (if it misses the 233U window, the next fissile target is 235U, meaning a total of 4 neutrons needed to trigger fission). ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Molten-Salt Reactor Experiment
The Molten-Salt Reactor Experiment (MSRE) was an experimental molten-salt reactor research reactor at the Oak Ridge National Laboratory (ORNL) in Oak Ridge, Tennessee. This technology was researched through the 1960s, the reactor was constructed by 1964, it went critical in 1965, and was operated until 1969. The costs of a cleanup project were estimated at $130 million. Initially designed for 15 MWth, the MSRE was operated at 7.4 MWth because of imprecise nuclear cross section data. It was a test reactor simulating the neutronic "kernel" of a type of inherently safer epithermal thorium breeder reactor called the liquid fluoride thorium reactor. It primarily used two fuels: first uranium-235 and later uranium-233. The latter 233UF4 was the result of breeding from thorium in other reactors. Since this was an engineering test, the large, expensive breeding blanket of thorium salt was omitted in favor of neutron measurements. In the MSRE, the heat from the reactor core was ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Beryllium Fluoride
Beryllium fluoride is the inorganic compound with the formula Be F2. This white solid is the principal precursor for the manufacture of beryllium metal. Its structure resembles that of quartz, but BeF2 is highly soluble in water. Properties Beryllium fluoride has distinctive optical properties. In the form of fluoroberyllate glass, it has the lowest refractive index In optics, the refractive index (or refraction index) of an optical medium is the ratio of the apparent speed of light in the air or vacuum to the speed in the medium. The refractive index determines how much the path of light is bent, or refrac ... for a solid at room temperature of 1.275. Its dispersive power is the lowest for a solid at 0.0093, and the nonlinear coefficient is also the lowest at 2 × 10−14. Structure and bonding The structure of solid BeF2 resembles that of cristobalite. Be2+ centers are four coordinate and tetrahedral and the fluoride centers are two-coordinate. The Be-F bond lengths a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lithium Fluoride
Lithium fluoride is an inorganic compound with the chemical formula LiF. It is a colorless solid that transitions to white with decreasing crystal size. Its structure is analogous to that of sodium chloride, but it is much less soluble in water. It is mainly used as a component of molten salts. Partly because Li and F are both light elements, and partly because is highly reactive, formation of LiF from the elements releases one of the highest energies per mass of reactants, second only to that of BeO. Manufacturing LiF is prepared from lithium hydroxide or lithium carbonate with hydrogen fluoride. Applications Precursor to lithium hexafluorophosphate for batteries Lithium fluoride is reacted with hydrogen fluoride (HF) and phosphorus pentachloride to make lithium hexafluorophosphate , an ingredient in lithium ion battery electrolyte. The lithium fluoride alone does not absorb hydrogen fluoride to form a bifluoride salt. In molten salts Fluorine is produced by the elec ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Aircraft Reactor Experiment
The Aircraft Reactor Experiment (ARE) was an experimental nuclear reactor designed to test the feasibility of fluid-fuel, high-temperature, high-power-density reactors for the propulsion of supersonic aircraft. It operated from November 8–12, 1954, at the Oak Ridge National Laboratory (ORNL) with a maximum sustained power of 2.5 megawatts (MW) and generated 96 MW-hours of energy. The ARE was the first reactor to use circulating molten salt fuel. The hundreds of engineers and scientists working on ARE provided technical data, facilities, equipment, and experience that enabled the broader development of molten-salt reactors as well as liquid metal cooled reactors. Background The concept of nuclear-powered aircraft was first formally studied in May 1946 by the US Army Air Forces. It was hypothesized that the unique characteristics of nuclear power could be applied to long-range supersonic flight, which was considered highly valuable in terms of military strategy. Challenges in t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Uranium Tetrafluoride
Uranium tetrafluoride is the inorganic compound with the formula UF4. It is a green solid with an insignificant vapor pressure and low solubility in water. Uranium in its tetravalent ( uranous) state is important in various technological processes. In the uranium refining industry it is known as green salt. Production UF4 is prepared from UO2 in a fluidized bed by reaction with Hydrogen fluoride. The UO2 is derived from mining operations. Around 60,000 tonnes are prepared in this way annually. A common impurity is UO2F2. UF4 is susceptible to hydrolysis as well. UF4 is formed by the reaction of UF6 with hydrogen gas in a vertical tube-type reactor. The bulk density of UF4 varies from about 2.0 g/cm3 to about 4.5 g/cm3 depending on the production process and the properties of the starting uranium compounds. A molten salt reactor design, a type of nuclear reactor where the working fluid is a molten salt, would use UF4 as the core material. UF4 is generally chosen over relate ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Potassium Hexafluorozirconate
Potassium hexafluorozirconate is an inorganic compound of potassium, fluorine, and zirconium with the chemical formula . Preparation Potassium hexafluorozirconate can be prepared from precipitation from solutions: : : Also, in industry, it is obtained by sintering zirconium ore concentrates with at 600–700 °C. Physical properties Potassium hexafluorozirconate forms an odorless white crystalline powder. It crystallizes in the monoclinic space group ''C 2/c'' (space group No. 15). Uses Potassium hexafluorozirconate is used as an intermediate product in the electrolytic production of metallic zirconium. It is also used as a flame retardant Flame retardants are a diverse group of chemicals that are added to manufactured materials, such as plastics and textiles, and surface finishes and coatings. Flame retardants are activated by the presence of an combustion, ignition source and pr ... for wool, grain refining agent in magnesium and aluminum alloys, welding flux, and o ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fluoride
Fluoride (). According to this source, is a possible pronunciation in British English. is an Inorganic chemistry, inorganic, Monatomic ion, monatomic Ion#Anions and cations, anion of fluorine, with the chemical formula (also written ), whose salts are typically white or colorless. Fluoride salts typically have distinctive bitter tastes, and are odorless. Its salts and minerals are important Reagent, chemical reagents and industrial chemicals, mainly used in the production of hydrogen fluoride for fluorocarbons. Fluoride is classified as a weak base since it only partially associates in solution, but concentrated fluoride is corrosive and can attack the skin. Fluoride is the simplest fluorine anion. In terms of charge and size, the fluoride ion resembles the hydroxide ion. Fluoride ions occur on Earth in several minerals, particularly fluorite, but are present only in trace quantities in bodies of water in nature. Nomenclature Fluorides include compounds that contain ionic ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
