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Gadolinium(III) Oxide
Gadolinium(III) oxide (archaically gadolinia) is an inorganic compound with the formula Gd2O3. It is one of the most commonly available forms of the rare-earth element gadolinium, derivatives, of which are potential contrast agents for magnetic resonance imaging. Structure Gadolinium oxide adopts two structures. The cubic ( cI80, Ia), No. 206) structure is similar to that of manganese(III) oxide and heavy trivalent lanthanide sesquioxides. The cubic structure features two types of gadolinium sites, each with a coordination number of 6 but with different coordination geometries. The second polymorph is monoclinic ( Pearson symbol mS30, space group C2/m, No. 12). At room temperature, the cubic structure is more stable. The phase change to the monoclinic structure takes place at 1200 °C. Above 2100 °C to the melting point at 2420 °C, a hexagonal phase dominates. Preparation and chemistry Gadolinium oxide can be formed by thermal decomposition of the hydro ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Acid
An acid is a molecule or ion capable of either donating a proton (i.e. Hydron, hydrogen cation, H+), known as a Brønsted–Lowry acid–base theory, Brønsted–Lowry acid, or forming a covalent bond with an electron pair, known as a Lewis acid. The first category of acids are the proton donors, or Brønsted–Lowry acid–base theory, Brønsted–Lowry acids. In the special case of aqueous solutions, proton donors form the hydronium ion H3O+ and are known as Acid–base reaction#Arrhenius theory, Arrhenius acids. Johannes Nicolaus Brønsted, Brønsted and Martin Lowry, Lowry generalized the Arrhenius theory to include non-aqueous solvents. A Brønsted–Lowry or Arrhenius acid usually contains a hydrogen atom bonded to a chemical structure that is still energetically favorable after loss of H+. Aqueous Arrhenius acids have characteristic properties that provide a practical description of an acid. Acids form aqueous solutions with a sour taste, can turn blue litmus red, and ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
List Of Space Groups
There are 230 space groups in three dimensions, given by a number index, and a full name in Hermann–Mauguin notation, and a short name (international short symbol). The long names are given with spaces for readability. The groups each have a point group of the unit cell. Symbols In Hermann–Mauguin notation, space groups are named by a symbol combining the point group identifier with the uppercase letters describing the lattice type. Translations within the lattice in the form of screw axes and glide planes are also noted, giving a complete crystallographic space group. These are the Bravais lattices in three dimensions: *P primitive *I body centered (from the German ''Innenzentriert'') *F face centered (from the German ''Flächenzentriert'') *A centered on A faces only *B centered on B faces only *C centered on C faces only *R rhombohedral A reflection plane m within the point groups can be replaced by a glide plane, labeled as a, b, or c depending on which axis the glide i ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sesquioxides
A sesquioxide is an oxide of an element (or radical), where the ratio between the number of atoms of that element and the number of atoms of oxygen is 2:3. For example, aluminium oxide and phosphorus(III) oxide are sesquioxides. Many sesquioxides contain a metal in the +3 oxidation state and the oxide ion , e.g., aluminium oxide , lanthanum(III) oxide and iron(III) oxide . Sesquioxides of iron and aluminium are found in soil. The alkali metal sesquioxides are exceptions because they contain both peroxide and superoxide ions, e.g., rubidium sesquioxide is formulated . Sesquioxides of metalloids and nonmetals are better formulated as covalent, e.g. boron trioxide , dinitrogen trioxide and phosphorus(III) oxide ; chlorine trioxide and bromine trioxide do not have oxidation state +3 on the halogen. Many transition metal oxides crystallize in the corundum structure type, with space group Rc. Sesquioxides of rare earth elements crystalize into one or more of three crystal ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gadolinium Compounds
Gadolinium is a chemical element; it has symbol Gd and atomic number 64. It is a silvery-white metal when oxidation is removed. Gadolinium is a malleable and ductile rare-earth element. It reacts with atmospheric oxygen or moisture slowly to form a black coating. Gadolinium below its Curie point of is ferromagnetic, with an attraction to a magnetic field higher than that of nickel. Above this temperature it is the most paramagnetic element. It is found in nature only in an oxidized form. When separated, it usually has impurities of the other rare earths because of their similar chemical properties. Gadolinium was discovered in 1880 by Jean Charles de Marignac, who detected its oxide by using spectroscopy. It is named after the mineral gadolinite, one of the minerals in which gadolinium is found, itself named for the Finnish chemist Johan Gadolin. Pure gadolinium was first isolated by the chemist Félix Trombe in 1935. Gadolinium possesses unusual metallurgical properties, to t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Solid Oxide Fuel Cell
A solid oxide fuel cell (or SOFC) is an electrochemical conversion device that produces electricity directly from oxidizing a fuel. Fuel cells are characterized by their electrolyte material; the SOFC has a solid oxide or ceramic electrolyte. Advantages of this class of fuel cells include high combined heat and power efficiency, long-term stability, fuel flexibility, low emissions, and relatively low cost. The largest disadvantage is the high operating temperature which results in longer start-up times and mechanical and chemical compatibility issues. Introduction Solid oxide fuel cells are a class of fuel cells characterized by the use of a solid oxide material as the electrolyte. SOFCs use a solid oxide electrolyte to conduct negative oxygen ions from the cathode to the anode. The electrochemical oxidation of the hydrogen, carbon monoxide or other organic intermediates by oxygen ions thus occurs on the anode side. More recently, proton-conducting SOFCs (PC-SOFC) are being dev ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Erbium
Erbium is a chemical element; it has Symbol (chemistry), symbol Er and atomic number 68. A silvery-white solid metal when artificially isolated, natural erbium is always found in chemical combination with other elements. It is a lanthanide, a rare-earth element, originally found in the gadolinite mine in Ytterby, Sweden, which is the source of the element's name. Erbium's principal uses involve its pink-colored Er3+ ions, which have optical fluorescent properties particularly useful in certain laser applications. Erbium-doped glasses or crystals can be used as optical amplification media, where Er3+ ions are optically pumped at around 980 or and then radiate light at in stimulated emission. This process results in an unusually mechanically simple laser optical amplifier for signals transmitted by fiber optics. The wavelength is especially important for optical communications because standard single mode optical fibers have minimal loss at this particular wavelength. In addition ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Neodymium
Neodymium is a chemical element; it has Symbol (chemistry), symbol Nd and atomic number 60. It is the fourth member of the lanthanide series and is considered to be one of the rare-earth element, rare-earth metals. It is a hard (physics), hard, slightly malleable, silvery metal that quickly tarnishes in air and moisture. When oxidized, neodymium reacts quickly producing pink, purple/blue and yellow compounds in the +2, +3 and +4 oxidation states. It is generally regarded as having one of the most complex emission spectrum, spectra of the elements. Neodymium was discovered in 1885 by the Austrian chemist Carl Auer von Welsbach, who also discovered praseodymium. Neodymium is present in significant quantities in the minerals monazite and bastnäsite. Neodymium is not found naturally in metallic form or unmixed with other lanthanides, and it is usually refined for general use. Neodymium is fairly common—about as common as cobalt, nickel, or copper—and is Abundance of elements in Eart ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dextran
Dextran is a complex branched glucan (polysaccharide derived from the condensation of glucose), originally derived from wine. IUPAC defines dextrans as "Branched poly-α-d-glucosides of microbial origin having glycosidic bonds predominantly C-1 → C-6". Dextran chains are of varying lengths (from 3 to 2000 kilodaltons). The polymer main chain consists of α-1,6 glycosidic linkages between glucose monomers, with branches from α-1,3 linkages. This characteristic branching distinguishes a dextran from a dextrin, which is a straight chain glucose polymer tethered by α-1,4 or α-1,6 linkages. Occurrence Dextran was discovered by Louis Pasteur as a microbial product in wine, but mass production was only possible after the development by Allene Jeanes of a process using bacteria. Dental plaque is rich in dextrans. Dextran is a complicating contaminant in the refining of sugar because it elevates the viscosity of sucrose solutions and fouls plumbing. Dextran is now produced f ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nanoparticle
A nanoparticle or ultrafine particle is a particle of matter 1 to 100 nanometres (nm) in diameter. The term is sometimes used for larger particles, up to 500 nm, or fibers and tubes that are less than 100 nm in only two directions. At the lowest range, metal particles smaller than 1 nm are usually called atom clusters instead. Nanoparticles are distinguished from microparticles (1-1000 μm), "fine particles" (sized between 100 and 2500 nm), and "coarse particles" (ranging from 2500 to 10,000 nm), because their smaller size drives very different physical or chemical properties, like colloidal properties and ultrafast optical effects or electric properties. Being more subject to the Brownian motion, they usually do not sediment, like colloid, colloidal particles that conversely are usually understood to range from 1 to 1000 nm. Being much smaller than the wavelengths of visible light (400-700 nm), nanoparticles cannot be seen with ordinary ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Oxalate
Oxalate (systematic IUPAC name: ethanedioate) is an anion with the chemical formula . This dianion is colorless. It occurs naturally, including in some foods. It forms a variety of salts, for example sodium oxalate (), and several esters such as dimethyl oxalate (). It is a conjugate base of oxalic acid. At neutral pH in aqueous solution, oxalic acid converts completely to oxalate. Relationship to oxalic acid The dissociation of protons from oxalic acid proceeds in a determined order; as for other polyprotic acids, loss of a single proton results in the monovalent hydrogenoxalate anion . A salt with this anion is sometimes called an acid oxalate, monobasic oxalate, or hydrogen oxalate. The equilibrium constant ( ''K''a) for loss of the first proton is ( p''K''a = 1.27). The loss of the second proton, which yields the oxalate ion, has an equilibrium constant of (p''K''a = 4.28). These values imply, in solutions with neutral pH, no oxalic acid and only t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Space Group
In mathematics, physics and chemistry, a space group is the symmetry group of a repeating pattern in space, usually in three dimensions. The elements of a space group (its symmetry operations) are the rigid transformations of the pattern that leave it unchanged. In three dimensions, space groups are classified into 219 distinct types, or 230 types if chiral copies are considered distinct. Space groups are discrete cocompact groups of isometries of an oriented Euclidean space in any number of dimensions. In dimensions other than 3, they are sometimes called Bieberbach groups. In crystallography, space groups are also called the crystallographic or Fedorov groups, and represent a description of the symmetry of the crystal. A definitive source regarding 3-dimensional space groups is the ''International Tables for Crystallography'' . History Space groups in 2 dimensions are the 17 wallpaper groups which have been known for several centuries, though the proof that the list ... [...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] |
