Tellurium(VI) Compounds
Tellurium is a chemical element; it has symbol Te and atomic number 52. It is a brittle, mildly toxic, rare, silver-white metalloid. Tellurium is chemically related to selenium and sulfur, all three of which are chalcogens. It is occasionally found in its native form as elemental crystals. Tellurium is far more common in the Universe as a whole than on Earth. Its extreme rarity in the Earth's crust, comparable to that of platinum, is due partly to its formation of a volatile hydride that caused tellurium to be lost to space as a gas during the hot nebular formation of Earth. Tellurium-bearing compounds were first discovered in 1782 in a gold mine in Kleinschlatten, Transylvania (now Zlatna, Romania) by Austrian mineralogist Franz-Joseph Müller von Reichenstein, although it was Martin Heinrich Klaproth who named the new element in 1798 after the Latin 'earth'. Gold telluride minerals are the most notable natural gold compounds. However, they are not a commercially significa ... [...More Info...]       [...Related Items...]     OR:     [Wikipedia]   [Google]   [Baidu]   |
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Chemical Element
A chemical element is a chemical substance whose atoms all have the same number of protons. The number of protons is called the atomic number of that element. For example, oxygen has an atomic number of 8: each oxygen atom has 8 protons in its atomic nucleus, nucleus. Atoms of the same element can have different numbers of neutrons in their nuclei, known as isotopes of the element. Two or more atoms can combine to form molecules. Some elements form Homonuclear molecule, molecules of atoms of said element only: e.g. atoms of hydrogen (H) form Diatomic molecule, diatomic molecules (H). Chemical compounds are substances made of atoms of different elements; they can have molecular or non-molecular structure. Mixtures are materials containing different chemical substances; that means (in case of molecular substances) that they contain different types of molecules. Atoms of one element can be transformed into atoms of a different element in nuclear reactions, which change an atom's at ... [...More Info...]       [...Related Items...]     OR:     [Wikipedia]   [Google]   [Baidu]   |
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Martin Heinrich Klaproth
Martin Heinrich Klaproth (1 December 1743 – 1 January 1817) was a German chemist. He trained and worked for much of his life as an apothecary, moving in later life to the university. His shop became the second-largest apothecary in Berlin, and the most productive artisanal chemical research center in Europe. Klaproth was a major systematizer of analytical chemistry, and an independent inventor of gravimetric analysis. His attention to detail and refusal to ignore discrepancies in results led to improvements in the use of apparatus. He was a major figure in understanding the composition of minerals and characterizing the elements. Klaproth discovered uranium (1789) and zirconium (1789). He was also involved in the discovery or co-discovery of titanium (1795), strontium (1793), cerium (1803), and chromium (1797) and confirmed the previous discoveries of tellurium (1798) and beryllium (1798). Klaproth was a member and director of the Berlin Academy of Scienc ... [...More Info...]       [...Related Items...]     OR:     [Wikipedia]   [Google]   [Baidu]   |
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Crystal
A crystal or crystalline solid is a solid material whose constituents (such as atoms, molecules, or ions) are arranged in a highly ordered microscopic structure, forming a crystal lattice that extends in all directions. In addition, macroscopic single crystals are usually identifiable by their geometrical shape, consisting of flat faces with specific, characteristic orientations. The scientific study of crystals and crystal formation is known as crystallography. The process of crystal formation via mechanisms of crystal growth is called crystallization or solidification. The word ''crystal'' derives from the Ancient Greek word (), meaning both "ice" and " rock crystal", from (), "icy cold, frost". Examples of large crystals include snowflakes, diamonds, and table salt. Most inorganic solids are not crystals but polycrystals, i.e. many microscopic crystals fused together into a single solid. Polycrystals include most metals, rocks, ceramics, and ice. A third cat ... [...More Info...]       [...Related Items...]     OR:     [Wikipedia]   [Google]   [Baidu]   |
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Allotrope
Allotropy or allotropism () is the property of some chemical elements to exist in two or more different forms, in the same physical state, known as allotropes of the elements. Allotropes are different structural modifications of an element: the atoms of the element are bonded together in different manners. For example, the allotropes of carbon include diamond (the carbon atoms are bonded together to form a cubic lattice of tetrahedra), graphite (the carbon atoms are bonded together in sheets of a hexagonal lattice), graphene (single sheets of graphite), and fullerenes (the carbon atoms are bonded together in spherical, tubular, or ellipsoidal formations). The term ''allotropy'' is used for elements only, not for compounds. The more general term, used for any compound, is polymorphism, although its use is usually restricted to solid materials such as crystals. Allotropy refers only to different forms of an element within the same physical phase (the state of matter, such as ... [...More Info...]       [...Related Items...]     OR:     [Wikipedia]   [Google]   [Baidu]   |
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Dimethyl Telluride
Dimethyl telluride is an organotelluride compound, formula ( CH3)2 Te, also known by the abbreviation DMTe. This was the first material used to grow epitaxial cadmium telluride and mercury cadmium telluride using metalorganic vapour phase epitaxy. Dimethyl telluride as a product of microbial metabolism was first discovered in 1939. It is produced by some fungi and bacteria ('' Penicillium brevicaule'', ''P. chrysogenum'', and '' P. notatum'' and the bacterium ''Pseudomonas fluorescens''). The toxicity of DMTe is unclear. It is produced by the body when tellurium or one of its compounds are ingested. It is noticeable by the garlic smelling breath it gives those exposed, similar to the effect of DMSO. Tellurium is known to be toxic Toxicity is the degree to which a chemical substance or a particular mixture of substances can damage an organism. Toxicity can refer to the effect on a whole organism, such as an animal, bacterium, or plant, as well as the effect on a subst ... [...More Info...]       [...Related Items...]     OR:     [Wikipedia]   [Google]   [Baidu]   |
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Tellurocysteine
Tellurocysteine (in some publications referred to as Te-Cys) is an amino acid with the formula . It is the heavy analogue of serine, cysteine, and selenocysteine. Tellurol (RTeH) is a rare and fragile functional group, especially alkyl derivatives. The C-Te bond (200 kJ/mol) is weak compared to 234 kJ/mol for the C-Se bond. These factors combine to make tellurocysteine very labile. Even selenocysteine occurs only rarely in nature. Instead of tellurocysteine, tellurocystine is generally isolated instead. Tellurocystine has the formula , with a central Te-Te bond. : Properties The fungus ''Aspergillus fumigatus'' is capable of incorporating tellurocysteine (and telluromethionine) into proteins when grown in appropriate media. When incorporated into glutathione transferase, tellurocysteine efficiently inhibits aminoacylation and increases the efficiency of glutathione peroxidase. Synthesis L-Tellurocystine has been prepared in low yield from a protected form of 3-iodoalanine ... [...More Info...]       [...Related Items...]     OR:     [Wikipedia]   [Google]   [Baidu]   |
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Amino Acid
Amino acids are organic compounds that contain both amino and carboxylic acid functional groups. Although over 500 amino acids exist in nature, by far the most important are the 22 α-amino acids incorporated into proteins. Only these 22 appear in the genetic code of life. Amino acids can be classified according to the locations of the core structural functional groups ( alpha- , beta- , gamma- amino acids, etc.); other categories relate to polarity, ionization, and side-chain group type ( aliphatic, acyclic, aromatic, polar, etc.). In the form of proteins, amino-acid '' residues'' form the second-largest component (water being the largest) of human muscles and other tissues. Beyond their role as residues in proteins, amino acids participate in a number of processes such as neurotransmitter transport and biosynthesis. It is thought that they played a key role in enabling life on Earth and its emergence. Amino acids are formally named by the IUPAC- IUBMB Joint Commi ... [...More Info...]       [...Related Items...]     OR:     [Wikipedia]   [Google]   [Baidu]   |
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Machinability
Machinability is the ease with which a metal can be cut ( machined) permitting the removal of the material with a satisfactory finish at low cost.Degarmo, p. 542. Materials with good machinability (free-machining materials) require little power to cut, can be cut quickly, easily obtain a good finish, and do not cause significant wear on the tooling. Factors that typically improve a material's performance often degrade its machinability, presenting a significant engineering challenge. Machinability can be difficult to predict due to the large number of variables involved in the machining process. Two sets of factors are the condition and physical properties of the work materials. The condition of the work material includes at least eight factors: microstructure, grain size, heat treatment, chemical composition, fabrication, hardness, yield strength, and tensile strength.Schneider, "Machinability." Physical properties are those of the individual material groups, such as the modu ... [...More Info...]       [...Related Items...]     OR:     [Wikipedia]   [Google]   [Baidu]   |
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Alloy
An alloy is a mixture of chemical elements of which in most cases at least one is a metal, metallic element, although it is also sometimes used for mixtures of elements; herein only metallic alloys are described. Metallic alloys often have properties that differ from those of the pure elements from which they are made. The vast majority of metals used for commercial purposes are alloyed to improve their properties or behavior, such as increased strength, hardness or corrosion resistance. Metals may also be alloyed to reduce their overall cost, for instance alloys of gold and Copper(II) sulfate, copper. A typical example of an alloy is SAE 304 stainless steel, 304 grade stainless steel which is commonly used for kitchen utensils, pans, knives and forks. Sometime also known as 18/8, it as an alloy consisting broadly of 74% iron, 18% chromium and 8% nickel. The chromium and nickel alloying elements add strength and hardness to the majority iron element, but their main function is ... [...More Info...]       [...Related Items...]     OR:     [Wikipedia]   [Google]   [Baidu]   |
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Tellurium Copper
Tellurium copper is an alloy of copper and tellurium. Tellurium improves the machinability of copper. Overview Tellurium is usually added to copper to improve machinability ("free cutting"). ASTM specification B301 has 0.5% tellurium; at concentrations of up to 0.75% machinability is improved while electrical conductivity and hot working behavior is maintained. Mechanical properties are similar to ''tough pitch copper'', while machinability is similar to brass - the hardness of the alloy is increased by precipitation of the copper telluride: weissite. Tellurium copper is not suited to welding, but it can be welded with gas shielded arc welding or resistance welding. It can be readily soft soldered, silver soldered, or brazed. Tellurium copper can be used as the electrode in electrical discharge machining (EDM) - the alloy is used to replace copper when grinding wheel Grinding wheels are wheels that contain abrasive compounds for grinding and abrasive machining oper ... [...More Info...]       [...Related Items...]     OR:     [Wikipedia]   [Google]   [Baidu]   |
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Thermoelectric
The thermoelectric effect is the direct conversion of temperature differences to electric voltage and vice versa via a thermocouple. A thermoelectric device creates a voltage when there is a different temperature on each side. Conversely, when a voltage is applied to it, heat is transferred from one side to the other, creating a temperature difference. This effect can be used to generate electricity, measure temperature or change the temperature of objects. Because the direction of heating and cooling is affected by the applied voltage, thermoelectric devices can be used as temperature controllers. The term "thermoelectric effect" encompasses three separately identified effects: the Seebeck effect (temperature differences cause electromotive forces), the Peltier effect (thermocouples create temperature differences), and the Thomson effect (the Seebeck coefficient varies with temperature). The Seebeck and Peltier effects are different manifestations of the same physical proces ... [...More Info...]       [...Related Items...]     OR:     [Wikipedia]   [Google]   [Baidu]   |
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CdTe Solar Panel
Cadmium telluride (CdTe) photovoltaics is a photovoltaic (PV) technology based on the use of cadmium telluride in a thin semiconductor layer designed to absorb and convert sunlight into electricity. Cadmium telluride PV is the only thin film technology with lower costs than conventional solar cells made of crystalline silicon in multi-kilowatt systems.K. Zweibel, J. Mason, V. Fthenakis,A Solar Grand Plan, ''Scientific American'', Jan 2008. CdTe PV is the cheapest example of PV technologies and prices are about 16¢/kWh with US Southwest sunlight. On a lifecycle basis, CdTe PV has the smallest carbon footprint, lowest water use and shortest energy payback time of any current photovoltaic technology. CdTe's energy payback time of less than a year allows for faster carbon reductions without short-term energy deficits. The toxicity of cadmium is an environmental concern during production and when the panels are disposed of. Some of this might be mitigated by recycling of CdTe ... [...More Info...]       [...Related Items...]     OR:     [Wikipedia]   [Google]   [Baidu]   |