Element History - Brief Review
Element History - Brief Review
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Publicado por : pinkllll
Publicado en : 04-11-21
Ubicación : London
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Element History - Brief Review
Element History - Brief Review
Tungsten is a heavy metallic element, a member of the third series of transition metals. It has the symbol W, its atomic number is 74, and its atomic weight is 183.85. The name is derived from the Swedish tung sten, meaning “heavy stone.” Tungsten is also known as wolfram, from WOLFRAMITE, the mineral from which the element was first recognized by the English chemist Peter Woulfe in 1779. The metal was first isolated in 1783 by Spanish scientists Jose and Fausto d’Elhuyar through the reduction, by means of charcoal, of the tungstic acid found in wolframite.
Tungsten occurs principally in the minerals scheelite, wolframite, huebnerite, and ferberite. In the United States these minerals occur most notably in California and Colorado. Elsewhere they are found in China, the Buryat republic of Russia, Kazakhstan, South Korea, Bolivia, and Portugal. The metal is obtained commercially by the reduction of tungstic oxide with hydrogen or carbon. The pure metal is steel gray to tin white in color. Its physical properties include the highest melting point of all metals, 3,410 deg C (6,170 deg F), a boiling point of 5,660 deg C (10,220 deg F), and a density of 19.3 g/cu cm.
Pure tungsten metal is easily forged, spun, drawn, and extruded, whereas in an impure state it is brittle and can be fabricated only with difficulty. Tungsten oxidizes in air, especially at higher temperatures, but it is resistant to corrosion and is only slightly attacked by most mineral acids. In keeping with the other Transition Elements, it displays a range of oxidation states: 0, +1, +2, +3, +4, +5, and +6. This accounts for the many complex ions and coordination complexes in which tungsten can be found. Tungsten is not known to have any biological significance.
Tungsten plate sheet is isostatically pressed and sintered from our high purity tungsten powders to compact ingots by powder metallurgy. Following the powder metallurgy is a series of further deformations and heat treatments until the required products are finished. We are now capable of machining tungsten plate and sheet with a range of thickness from 3.15 inches (80 mm) to less than 0.004 inches (0.1 mm).
CHEMETAL USA is a recognized manufacturer and supplier of high quality tungsten plate and tungsten sheet. Every tungsten plate we supply is under stringent quality control at every stage of production, including the rolling, annealing, surface treatment and a series of tests. Thanks to our experience and capacity in the field of milling tungsten product, we can always guarantee that our customers receive high-performance tungsten plate products with exceptional purity, roughness, dimension, flatness and surface condition.
Zirconium is abundant in S-type stars in which heavier elements are formed by neutron capture. Traces of the element are also present in the Sun, and rock brought back from the moon was found to have a surprisingly high zirconium content.
Down here on Earth scientists have recently discovered that zircons from the Jack Hill region of Western Australia were around 4.4 billion years old and this together with their oxygen isotope ratio of O16/O18 suggested that they could only have been formed when there was liquid water on the surface of the Earth, which is nearly 500 million years earlier than previously assumed.
Today the element is widely used, as zircon (zirconium silicate), zirconium oxide and as the metal itself.
Zircon sand is use for foundry equipment - in the heat-resistant linings for furnaces and to make foundry moulds and giant ladles. Mixed with vanadium or praseodymium, zircon makes blue and yellow pigments for glazing pottery and tiles.
Zirconium oxide, with a melting point of 2715oC, is used to make heat-resistant crucibles, ceramics and abrasives. A red-hot crucible made from ZrO2 can be plunged into cold water without cracking. Zirconium oxide is stronger than toughened steel and is also used for knives, scissors and golf irons. The production of pure zirconium oxide is ca 25,000 tonnes per year, some of which goes into other products, including cosmetics, antiperspirants, food packaging, and even fake gems. The paper and packaging industry finds that zirconium oxide makes good surface coatings because it has excellent water resistance and strength, and is non-toxic.
Hafnium is dispersed in Earth’s crust to the extent of three parts per million and is invariably found in zirconium minerals up to a few percent compared with zirconium. For example, the minerals zircon, ZrSiO4 (zirconium orthosilicate), and baddeleyite, which is essentially pure zirconium dioxide, ZrO2, generally have a hafnium content that varies from a few tenths of 1 percent to several percent. Altered zircons, like some alvites and cyrtolites, products of residual crystallization, show greater percentages of hafnium (up to 17 percent hafnium oxide in cyrtolite from Rockport, Mass., U.S.). Commercial sources of hafnium-bearing zirconium minerals are found in beach sands and river gravel in the United States (principally Florida), Australia, Brazil, western Africa, and India. Hafnium vapour has been identified in the Sun’s atmosphere.
Why Can Molybdenum Wire Cut Metal?
Many people have heard of wire cutting, and the molybdenum wire cutting is also a kind of wire cutting. Then why can molybdenum wire cut metal? Many people may think that molybdenum wire cutting is to cut metal with a molybdenum wire, just like sawing wood with a saw. In fact, this is not the case. So in this article, we’ll try to find out the reason why molybdenum wire can cut metal. But first of all, let’s figure out what are molybdenum and molybdenum wire.
What Are Molybdenum & Molybdenum Wire?
Molybdenum is a silver-white refractory metal. In appearance, metal molybdenum is very similar to tungsten, but it is still easy to distinguish them by their density. The density of molybdenum is only half that of tungsten.
Molybdenum is a rare metal on the earth, closely related to our lives, and enjoys a wide range of applications. For example, molybdenum is a strategic metal used in the defense industry, an important component of steel alloys, and an important nutrient element required by animals and plants. Because of its extremely strong inter-atomic binding force, it has high strength at room temperature and high temperature.
Molybdenum wire is a kind of metal wire made of molybdenum as the main component (above 99%) with a diameter between 0.02 mm and 0.2 mm. It has a tough texture and high tensile strength, mainly used for cutting workpieces in the industry. Molybdenum wires have high precision, low wire breaking rate, and fast processing speed, which can realize stable long time continuous processing. Molybdenum wires can not only process various metals, but also are widely used for lead wire, heating element, and so on.
NITINOL WIRE DESCRIPTION
Nitinol wire is a nickel-titanium alloy with super elasticity and shape memory properties. Shape memory refers to the ability of Nitinol to undergo deformation at one temperature, then recover its original, under formed shape upon heating above its transformation temperature. Super elasticity occurs at a narrow temperature range just above its transformation temperature; in this case, no heating is necessary to cause the under formed shape to recover, and the material exhibits enormous elasticity, some 10-30 times that of ordinary metal.
Note should be made of the fact that in the United States this element was originally called columbium (symbol Cb). The Nomenclature Committee of the International Union of Pure and Applied Chemistry in 1951 adopted a recommendation to name this element niobium (symbol Nb). American chemists use this name, but the metallurgists and metals industry still use the name columbium. Most niobium is used in special stainless steels, high-temperature alloys, and superconducting alloys such as Nb3Sn. The low cross-section capture of niobium for thermal neutrons of only 1.1 barn makes it suitable for use in nuclear piles.
Niobium is a tough, shiny, silver-gray, soft, ductile metal that somewhat resembles stainless steel in appearance. Niobium is relatively low in density, yet can maintain its strength at high temperatures. It has excellent corrosion resistance to liquid metals, and can be easily fabricated into wrought products.
Over 95% of all niobium is used as additions to steel and nickel alloys for increasing strength. Only 1 to 2% of niobium is in the form of niobium-base alloys or pure niobium metal. Superconducting niobium-titanium alloys account for over half of that, and high-temperature and corrosion applications account for the remainder.
The density of niobium at 8.57 g/cm3 is moderate compared with most other high melting point metals. It is less than molybdenum at 10.2 g/cm3 and half that of tantalum at 16.6 g/cm3.
Commercial niobium alloy is relatively low in strength and extremely ductile, and can be cold-worked over 70% before annealing becomes necessary. The resulting ease of fabrication into complex parts combined with relatively low density frequently favors the selection of niobium alloys over other refractory metals such as molybdenum, tantalum, or tungsten.
High-temperature niobium alloys were developed in the 1960s for nuclear and aerospace applications and today serve in communications satellites, human body imaging equipment, and a variety of high-temperature components. Although niobium alloys have useful strength at temperatures hundreds of degrees above nickel-base superalloys, applications have been limited by their susceptibility to oxidation and to long-term creep.