Titanium (BioDeep_00000027733)

描述信息

A metallic element, titanium is recognized for its high strength-to-weight ratio. It is a strong metal with low density that is quite ductile (especially in an oxygen-free environment), lustrous, and metallic-white in color. The relatively high melting point (over 1,649 °C or 3,000 °F) makes it useful as a refractory metal.; A more recently developed method, the FFC Cambridge process, may eventually replace the Kroll process. This method uses titanium dioxide powder (which is a refined form of rutile) as feedstock to make the end product which is either a powder or sponge. If mixed oxide powders are used, the product is an alloy manufactured at a much lower cost than the conventional multi-step melting process. The FFC Cambridge process may render titanium a less rare and expensive material for the aerospace industry and the luxury goods market, and could be seen in many products currently manufactured using aluminium and specialist grades of steel.; Due to their high tensile strength to density ratio, high corrosion resistance, and ability to withstand moderately high temperatures without creeping, titanium alloys are used in aircraft, armor plating, naval ships, spacecraft, and missiles. For these applications titanium alloyed with aluminium, vanadium, and other elements is used for a variety of components including critical structural parts, fire walls, landing gear, exhaust ducts (helicopters), and hydraulic systems. In fact, about two thirds of all titanium metal produced is used in aircraft engines and frames. The SR-71 "Blackbird" was one of the first aircraft to make extensive use of titanium within its structure, paving the way for its use in modern military and commercial aircraft. An estimated 59 metric tons (130,000 pounds) are used in the Boeing 777, 45 in the Boeing 747, 18 in the Boeing 737, 32 in the Airbus A340, 18 in the Airbus A330, and 12 in the Airbus A320. The Airbus A380 may use 146 metric tons, including about 26 tons in the engines. In engine applications, titanium is used for rotors, compressor blades, hydraulic system components, and nacelles. The titanium 6AL-4V alloy accounts for almost 50\\% of all alloys used in aircraft applications.; The metal is a dimorphic allotrope with the hexagonal alpha form changing into the body-centered cubic (lattice) ? form at 882 °C (1,620 °F). The specific heat of the alpha form increases dramatically as it is heated to this transition temperature but then falls and remains fairly constant for the ? form regardless of temperature. Similar to zirconium and hafnium, an additional omega phase exists, which is thermodynamically stable at high pressures, but is metastable at ambient pressures. This phase is usually hexagonal (ideal) or trigonal (distorted) and can be viewed as being due to a soft longitudinal acoustic phonon of the ? phase causing collapse of (111) planes of atoms.; Titanium (pronounced /ta??te?ni?m/, tye-TAY-nee-?m) is a chemical element with the symbol Ti and atomic number 22. Sometimes called the ?space age metal?, it has a low density and is a strong, lustrous, corrosion-resistant (including sea water, aqua regia and chlorine) transition metal with a silver color.; Titanium burns in air when heated to 1,200 °C (2,190 °F) and in pure oxygen when heated to 610 °C (1,130 °F) or higher, forming titanium dioxide. As a result, the metal cannot be melted in open air as it burns before the melting point is reached, so melting is only possible in an inert atmosphere or in a vacuum. It is also one of the few elements that burns in pure nitrogen gas (it burns at 800 °C or 1,472 °F and forms titanium nitride, which causes embrittlement). Titanium is resistant to dilute sulfuric acid and hydrochloric acid, along with chlorine gas, chloride solutions, and most organic acids. It is paramagnetic (weakly attracted to magnets) and has fairly low electrical and thermal conductivity.; Titanium is a light, strong, lustrous, corrosion-resistant (including resistance to sea...
Titanium is a light, strong, lustrous, corrosion-resistant (including resistance to sea water and chlorine) transition metal with a white-silvery-metallic color; in the periodic table it has the symbol Ti and atomic number 22. Titanium and its alloys are used for medical purpose like osteosynthesis, arthroplasty, pacemaker encasing, orthodontical wires, or in daily-use articles like spectacle frames. At a composition of 50\\% nickel and 50\\% titanium, the material nitinol can be folded but returns at given temperatures to its original form without damage. This shape memory effect is used for spectacle frames, flexible tubes, intravascular stents, or orthodontic wires. When exposing the latter to an acidic environment, a substantial nickel and titanium release can be observed. However, even pure titanium materials used for implant alloys may contain nickel as result of the production process. Standard titanium alloys (TiAl6Nb7, TiAl6V4) and pure titanium discs supplied by five different titanium manufactures were shown to contain up to 0.034 wt \\% nickel, with iodide-titanium having the lowest percentage (0.002 wt \\%). Here, the nickel atoms are reported to be in solid solution in the titanium lattice. Suspected delayed-type hypersensitivity reactions to titanium were first reported as pacemaker dermatitis, but their existence is still put in question due to not always complete allergological work up and insufficient patch test preparations. In 1984, Peters et al. described a patient who had repeatedly cardiac pacemakers implanted and removed because pruritus, redness, and swelling of the skin overlying the pacemaker had developed within several weeks after insertion. These reactions were interpreted as contact sensitivity to the pure titanium encasing of the pacemaker, as there was a ++ patch test reaction to a thin square of metallic titanium applied with artificial sweat. Physiologically, it exists as an ion in the body. Humans exposed to titanium can develop pulmonary alveolar proteinosis (PAP, a disease of obscure cause that is characterized by the accumulation of a granular material that contains abundant lipid within the alveoli of lung.) with severe respiratory failure; analysis of particles found in lung tissues obtained by open lung biopsies demonstrated the presence of titanium. Salts of titanium are often considered to be relatively harmless but its chlorine compounds, such as TiCl2, TiCl3 and TiCl4, have unusual hazards. The dichloride takes the form of pyrophoric black crystals, and the tetrachloride is a volatile fuming liquid. All of titaniums chlorides are corrosive. (PMID: 7606971, 14756054, 16958916).

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