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Titanium Compounds
The +4 oxidation state dominates titanium chemistry, but compounds in the +3 oxidation state are also numerous. Commonly, titanium adopts an octahedral coordination geometry in its complexes, but tetrahedral TiCl4 is a notable exception. Because of its high oxidation state, titanium(IV) compounds exhibit a high degree of covalent bonding. Oxides, sulfides, and alkoxides The most important oxide is TiO2, which exists in three important polymorphs; anatase, brookite, and rutile. All three are white diamagnetic solids, although mineral samples can appear dark (see rutile). They adopt polymeric structures in which Ti is surrounded by six oxide ligands that link to other Ti centers. The term ''titanates'' usually refers to titanium(IV) compounds, as represented by barium titanate (BaTiO3). With a perovskite structure, this material exhibits piezoelectric properties and is used as a transducer in the interconversion of sound and electricity. Many minerals are titanates, such as ilme ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Titanium Nitride Coating
Titanium is a chemical element with the symbol Ti and atomic number 22. Found in nature only as an oxide, it can be reduced to produce a lustrous transition metal with a silver color, low density, and high strength, resistant to corrosion in sea water, aqua regia, and chlorine. Titanium was discovered in Cornwall, Great Britain, by William Gregor in 1791 and was named by Martin Heinrich Klaproth after the Titans of Greek mythology. The element occurs within a number of minerals, principally rutile and ilmenite, which are widely distributed in the Earth's crust and lithosphere; it is found in almost all living things, as well as bodies of water, rocks, and soils. The metal is extracted from its principal mineral ores by the Kroll and Hunter processes. The most common compound, titanium dioxide, is a popular photocatalyst and is used in the manufacture of white pigments. Other compounds include titanium tetrachloride (TiCl4), a component of smoke screens and catalysts; and titan ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Asterism (gemmology)
An asterism () is a star-shaped concentration of reflected or refracted light from a gemstone. Asterisms can appear when a suitable stone is cut ''en cabochon'' i.e. shaped and polished (not faceted). A gemstone that exhibits this effect is referred to as a star stone or asteria. The best known is star sapphire, but many other minerals can also be asteria, usually due to impurities in the crystal structure. Archetype The archetypal asteria is the star sapphire, generally corundum with near uniform impurities which is bluish-grey and milky or opalescent, which when lit has a star of six rays. In the red instance stellate reflection is rarer; the star- ruby occasionally found with the star-sapphire in Sri Lanka is among the most valued of "fancy stones". Other examples are star- topaz and certain prized chatoyant (, ) chrysoberyl stones, particularly of the cymophane (yellow) variety. Description Asterism is generated by reflections of light from twin-lamellae or from ext ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lithium Batteries
Lithium battery may refer to: * Lithium metal battery, a non-rechargeable battery with lithium as an anode ** Rechargeable lithium metal battery, a rechargeable counterpart to the lithium metal battery * Lithium-ion battery, a rechargeable battery in which lithium ions move from the negative electrode to the positive electrode during discharge and back when charging ** Thin-film lithium-ion battery, a solid-state lithium-ion battery constructed as a thin-film ** Aqueous lithium-ion battery ** Lithium-ion flow battery ** Lithium ion manganese oxide battery * Lithium polymer battery * Lithium–sulfur battery * Lithium-titanate battery * Lithium–air battery * Lithium iron phosphate battery * Nickel–lithium battery * Lithium–silicon battery * Lithium vanadium phosphate battery * Lithium hybrid organic battery See also *List of battery types *Lithium batteries in China *High capacity oceanographic lithium battery pack *Glass battery, which may use a lithium metal electrode *Sub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Titanium Disulfide
Titanium disulfide is an inorganic compound with the formula Ti S2. A golden yellow solid with high electrical conductivity, it belongs to a group of compounds called transition metal dichalcogenides, which consist of the stoichiometry M E2. TiS2 has been employed as a cathode material in rechargeable batteries. Structure With a layered structure, TiS2 adopts a hexagonal close packed (hcp) structure, analogous to cadmium iodide (CdI2). In this motif, half of the octahedral holes are filled with a "cation", in this case Ti4+. Each Ti centre is surrounded by six sulfide ligands in an octahedral structure. Each sulfide is connected to three Ti centres, the geometry at S being pyramidal. Several metal dichalcogenides adopt similar structures, but some, notably MoS2, do not. The layers of TiS2 consist of covalent Ti-S bonds. The individual layers of TiS2 are bound together by van der Waals forces, which are relatively weak intermolecular forces. It crystallises in the space ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sharpless Epoxidation
The Sharpless epoxidation reaction is an enantioselective chemical reaction to prepare 2,3-epoxyalcohols from primary and secondary allylic alcohols. The oxidizing agent is ''tert''-butyl hydroperoxide. The method relies on a catalyst formed from titanium tetra(isopropoxide) and diethyl tartrate. 2,3-Epoxyalcohols can be converted into diols, aminoalcohols, and ethers. The reactants for the Sharpless epoxidation are commercially available and relatively inexpensive. K. Barry Sharpless was awarded the 2001 Nobel Prize in Chemistry for this and related work on asymmetric oxidations. The prize was shared with William S. Knowles and Ryōji Noyori. Catalyst 5–10 mol% of the catalyst is typical. The presence of 3Å molecular sieves (3Å MS) is necessary. The structure of the catalyst is uncertain although it is thought to be a dimer of []. Selectivity The epoxidation of allylic alcohols is a well-utilized conversion in fine chemical synthesis. The chirality of the produ ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Titanium Isopropoxide
Titanium isopropoxide, also commonly referred to as titanium tetraisopropoxide or TTIP, is a chemical compound with the formula . This alkoxide of titanium(IV) is used in organic synthesis and materials science. It is a diamagnetic tetrahedral molecule. Titanium isopropoxide is a component of the Sharpless epoxidation, a method for the synthesis of chiral epoxides. The structures of the titanium alkoxides are often complex. Crystalline titanium methoxide is tetrameric with the molecular formula . Alkoxides derived from bulkier alcohols such as isopropyl alcohol aggregate less. Titanium isopropoxide is mainly a monomer in nonpolar solvents. Preparation It is prepared by treating titanium tetrachloride with isopropanol. Hydrogen chloride is formed as a coproduct: : TiCl4 + 4 (CH3)2CHOH → Ti4 + 4 HCl Properties Titanium isopropoxide reacts with water to deposit titanium dioxide: :Ti4 + 2 H2O → TiO2 + 4 (CH3)2CHOH This reaction is employed in the sol-gel synthesis of TiO2-bas ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Alkoxide
In chemistry, an alkoxide is the conjugate base of an alcohol and therefore consists of an organic group bonded to a negatively charged oxygen atom. They are written as , where R is the organic substituent. Alkoxides are strong bases and, when R is not bulky, good nucleophiles and good ligands. Alkoxides, although generally not stable in protic solvents such as water, occur widely as intermediates in various reactions, including the Williamson ether synthesis. Transition metal alkoxides are widely used for coatings and as catalysts. Enolates are unsaturated alkoxides derived by deprotonation of a bond adjacent to a ketone or aldehyde. The nucleophilic center for simple alkoxides is located on the oxygen, whereas the nucleophilic site on enolates is delocalized onto both carbon and oxygen sites. Ynolates are also unsaturated alkoxides derived from acetylenic alcohols. Phenoxides are close relatives of the alkoxides, in which the alkyl group is replaced by a derivative of be ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Titanium(II) Oxide
Titanium(II) oxide ( Ti O) is an inorganic chemical compound of titanium and oxygen. It can be prepared from titanium dioxide and titanium metal at 1500 °C. It is non-stoichiometric in a range TiO0.7 to TiO1.3 and this is caused by vacancies of either Ti or O in the defect rock salt structure. In pure TiO 15% of both Ti and O sites are vacant, as the vacancies allow metal-metal bonding between adjacent Ti centres. Careful annealing can cause ordering of the vacancies producing a monoclinic form which has 5 TiO units in the primitive cell that exhibits lower resistivity. A high temperature form with titanium atoms with trigonal prismatic coordination is also known. Acid solutions of TiO are stable for a short time then decompose to give hydrogen: :2 Ti2+(aq) + 2 H+(aq) → 2 Ti3+(aq) + H2(g) Gas-phase TiO shows strong bands in the optical spectra of cool ( M-type) stars. In 2017, TiO was claimed to be detected in an exoplanet An exoplanet or extrasolar planet is a plan ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Corundum
Corundum is a crystalline form of aluminium oxide () typically containing traces of iron, titanium, vanadium and chromium. It is a rock-forming mineral. It is a naturally transparent material, but can have different colors depending on the presence of transition metal impurities in its crystalline structure. Corundum has two primary gem varieties: ruby and sapphire. Rubies are red due to the presence of chromium, and sapphires exhibit a range of colors depending on what transition metal is present. A rare type of sapphire, padparadscha sapphire, is pink-orange. The name "corundum" is derived from the Tamil- Dravidian word ''kurundam'' (ruby-sapphire) (appearing in Sanskrit as ''kuruvinda''). Because of corundum's hardness (pure corundum is defined to have 9.0 on the Mohs scale), it can scratch almost all other minerals. It is commonly used as an abrasive on sandpaper and on large tools used in machining metals, plastics, and wood. Emery, a variety of corundum with no value a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Titanium(III) Oxide
Titanium(III) oxide is the inorganic compound with the formula Titanium, Ti2oxide, O3. A black semiconducting solid, it is prepared by reducing titanium dioxide with Titanium, titanium metal at 1600 °C. Ti2O3 adopts the alumina, Al2O3 (corundum) structure. It is reactive with oxidising agents. At around 200 °C there is a transition from semiconducting to metallic conducting. Titanium(III) oxide occurs naturally as the extremely rare mineral tistarite. Other titanium(III) oxides include LiTi2O4 and LiTiO2. References Titanium(III) compounds Sesquioxides Transition metal oxides Semiconductor materials {{inorganic-compound-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Reduction (chemistry)
Redox (reduction–oxidation, , ) is a type of chemical reaction in which the oxidation states of substrate (chemistry), substrate change. Oxidation is the loss of Electron, electrons or an increase in the oxidation state, while reduction is the gain of electrons or a decrease in the oxidation state. There are two classes of redox reactions: * ''Electron-transfer'' – Only one (usually) electron flows from the reducing agent to the oxidant. This type of redox reaction is often discussed in terms of redox couples and electrode potentials. * ''Atom transfer'' – An atom transfers from one substrate to another. For example, in the rusting of iron, the oxidation state of iron atoms increases as the iron converts to an oxide, and simultaneously the oxidation state of oxygen decreases as it accepts electrons released by the iron. Although oxidation reactions are commonly associated with the formation of oxides, other chemical species can serve the same function. In hydrogen ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
