| 单词 | vanadium | |||
| 释义 | vanadiumva·na·di·umV0018700 (və-nā′dē-əm)vanadium(vəˈneɪdɪəm)va•na•di•um(vəˈneɪ di əm)n. va·na·di·um(və-nā′dē-əm)
vanadiumvanadium(vənā`dēəm), metallic chemical element; symbol V; at. no. 23; at. wt. 50.9415; m.p. about 1,890°C;; b.p. 3,380°C;; sp. gr. about 6 at 20°C;; valence +2, +3, +4, or +5. Vanadium is a soft, ductile, silver-grey metal. It is the element above niobium in Group 5 of the periodic tableperiodic table,chart of the elements arranged according to the periodic law discovered by Dmitri I. Mendeleev and revised by Henry G. J. Moseley. In the periodic table the elements are arranged in columns and rows according to increasing atomic number (see the table entitled ..... Click the link for more information. . In its properties it resembles chromium. It is corrosion resistant at normal temperatures, but oxidizes above 660°C;. It resists attack by hydrochloric and sulfuric acids, saltwater, or alkalies. Vanadium forms numerous compounds, including vanadates and complex organic compounds. Vanadium pentoxide, V2O5, is commercially important. Vanadium is not found uncombined in nature but occurs widely distributed in minerals. Important ores include carnotite, patronite, roscoelite, and vanadinite. In the United States vanadium ores are mined in Arizona, Colorado, and Utah; other sources are Peru and Africa. Vanadium is recovered from these ores largely as the pentoxide; the pentoxide is also recovered during phosphorus production in Idaho and from certain crude oils and petroleum ashes. The principal use of vanadium is in alloys, especially with steelsteel, alloy of iron, carbon, and small proportions of other elements. Iron contains impurities in the form of silicon, phosphorus, sulfur, and manganese; steelmaking involves the removal of these impurities, known as slag, and the addition of desirable alloying elements. ..... Click the link for more information. . In tool and spring steels it is a powerful alloying agent; a small amount (less than 1%) adds strength, toughness, and heat resistance. It is usually added in the form of ferrovanadium, a vanadium-iron alloy. Vanadium compounds, especially the pentoxide, are used in the ceramics, glass, and dye industries, and are important as catalysts in the chemical industry. Although high-purity vanadium metal can be produced by chemical reduction of the trichloride, most commercial production of the metal is by calcium reduction of the pentoxide. Vanadium was discovered in 1801 by A. M. del Rio, who called it erythronium; however, it was mistaken for impure chromium. The element was rediscovered and named in 1830 by N. G. Sefström, a Swedish chemist. It was first isolated in 1867 by H. E. Roscoe. VanadiumV, a chemical element in Group V of Mendeleev’s periodic system. Atomic number, 23; atomic weight, 50.942. It is a steel-gray metal. Natural vanadium consists of two isotopes, 51V (99.75 percent) and 50V (0.25 percent); the latter is weakly radioactive (half-life T½ = 1014 years). Vanadium was discovered in 1801 in Mexican brown lead ore by the Mexican mineralogist A. M. del Rio. Because of the beautiful red color of its heated salts he called it erythronium (from the Greek erythros, red). In 1830 the Swedish chemist N. G. Sefström found a new element in iron ore from Taberg (Sweden) and called it vanadium in honor of Vanadis, the ancient Scandinavian goddess of beauty. In 1869 the British chemist H. Roscoe produced powdered metallic vanadium by reducing VCl2 with hydrogen. Vanadium has been manufactured on an industrial scale since the early 20th century. The vanadium content of the earth’s crust is 1.5 × 10-2 percent by mass; vanadium is rather widespread but is scattered in rocks and minerals. Patronite, roscoelite, descloizite, carnotite, and vanadinite are among the large number of vanadium minerals that have industrial significance. Important sources of vanadium are titanomagnetite and sedimentary (phosphoric) iron ores, as well as oxidized copper-lead-zinc ores. Vanadium is extracted as a by-product in the processing of uranium raw material, phosphorites, bauxites, and various organic deposits (asphaltites and combustible shales). Physical and chemical propertiesb Vanadium has a body-centered cubic lattice; lattice constant a = 3.0282 angstroms. Pure vanadium is ductile and easily shaped by pressure. Density, 6.11 g/cm3; melting point, 1900° ± 25° C; boiling point, 3400° C; specific heat (at 20°-100° C), 0.120 cal/g ·deg; thermal coefficient of linear expansion (at 20°-1000° C), 10.6 × 10-6 deg-1; specific electric resistance (at 20° C), 24.8 × 10-8 ohms m (24.8 x 10"6 ohms cm). Below 4.5° K, vanadium becomes a superconductor. After annealing, the mechanical properties of vanadium are elastic modulus, 135.25 newtons per sq m (N/m2), or 13,520 kilograms-force per sq mm (kgf/mm2); ultimate strength, 120 millinewtons per sq m (mN/m2), or 12 kgf/mm2; relative elongation, 17 percent; Brinell hardness 700 mN/m2 (70 kgf/mm2). Gaseous impurities markedly lower the plasticity of vanadium and increase its hardness and brittleness. At room temperature vanadium is not affected by air, seawater, or solutions of alkalies, and it is resistant to nonoxidizing acids, with the exception of hydrofluoric acid. Its resistance to corrosion by hydrochloric and sulfuric acids is much greater than that of titanium or stainless steel. When heated above 300° C in air, vanadium absorbs oxygen and becomes brittle. At 600°-700° C it oxidizes vigorously, with the formation of vanadium pentoxide, V205, as well as lower oxides. The nitride VN (melting point Tm = 2050° C, which is resistant to water and acids, is formed when vanadium is heated to over 700° C in a flow of nitrogen. At high temperatures vanadium reacts with carbon to give the refractory carbide VC (Tm = 2800° C), which is extremely hard. Vanadium yields compounds for valences of 2, 3, 4, and 5; the known oxides for these valences are VO and V2O3 (basic), VO2 (amphoteric), and V2O5 (acidic), respectively. Divalent and trivalent vanadium compounds are unstable and are powerful reducing agents. The high-valence compounds are of practical importance. The tendency of vanadium to form compounds of various valences is used in analytical chemistry and is also responsible for the catalytic properties of V205. Vanadium pentoxide dissolves in alkalies to give vanadates. Preparation and use Among the processes used to extract vanadium are direct leaching of ore or an ore concentrate with solutions of acids or alkalies and sintering of the original raw material (NaCl is often added), followed by leaching of the sintering product with water or dilute acids. Hydrated vanadium pentoxide is obtained from the solutions by hydrolysis (at pH = 1-3). When iron ores containing vanadium are smelted in a blast furnace, the vanadium passes into the cast iron, and the conversion of the cast iron to steel yields slags containing 10-16 percent V2O5. The vanadium slags are roasted with common salt and leached, first with water and then with dilute sulfuric acid, and V2O5 is separated from the solutions. It can be used to prepare ferrovanadium (iron alloys containing 35-70 percent vanadium), as well as metallic vanadium and its compounds. Ductile metallic vanadium is obtained by thermal reduction of pure V2O5 or V2O3 with calcium, by reduction of V2O5 with aluminum, by vacuum thermal reduction of V2O3 with carbon, by thermal reduction of VCl3 with magnesium, or by thermal dissociation of vanadium iodide. Vanadium is melted in vacuum arc furnaces, with consumable electrodes and in electron-beam furnaces. Vanadium is mainly used in ferrous metallurgy (up to 95 percent of the metal produced). It is a component of high-speed steel and its substitutes, low-alloyed instrument steels, and some construction steels. The addition of 0.15-0.25 percent vanadium markedly increases the strength, ductility, fatigue resistance, and wear resistance of steel. The vanadium in steel acts simultaneously as an oxygen scavenger and carbide-forming element. The vanadium carbides, which occur in the form of disperse inclusions, prevent grain growth when the steel is heated. Vanadium is introduced into the steel as a master alloy, ferrovanadium; it is also used for alloying cast iron. The fast-growing titanium-alloys industry is a new user of vanadium (some titanium alloys contain up to 13 percent vanadium). Alloys based on niobium, chromium, and tantalum with vanadium as an additive have found applications in aviation, rocketry, and other areas of technology. High-temperature and corrosion-resistant alloys of various composition based on vanadium plus Ti, Nb, W, Zr, and Al are being developed and are expected to find application in aviation, rocketry, and atom technology. Superconductor alloys and compounds of vanadium with Ga, Si, and Ti are also of interest. Pure metallic vanadium is used in nuclear power engineering (jackets for fuel elements; tubes) and in making electronic devices. Vanadium compounds are used in the chemical industry as catalysts, in agriculture and medicine, and in the textile, paint and varnish, rubber, ceramics, glass, photographic, and motion-picture industries. Vanadium compounds are toxic; poisoning is possible if dust containing them is inhaled. They cause irritation of the respiratory passages, pulmonary hemorrhages, dizziness, and dysfunction of the heart, kidney, and other organs. Vanadium in the organism Vanadium is a constant constituent of plant and animal organisms. The source of vanadium is igneous rocks and shales (containing about 0.013 percent vanadium), as well as sandstones and limestones (about 0.002 percent). Soils contain about 0.01 percent (mainly in the humus); fresh water and seawater, 1-2 x 10-7 percent. The vanadium content of terrestrial and water plants is considerably higher (0.16-0.2 percent) than in terrestrial and water animals (1.5 x 10-5 to 2 x 10-4 percent). Among the organisms that concentrate vanadium are the pearlwort Plumatella, the mollusk Pleurobranchus plumula, the holothurian Stichopus mobii, and some ascidians, molds (Aspergillus niger), and fungi (Amanita muscaria). The biological role of vanadium has been studied in the ascidians, whose blood cells contain trivalent and tetravalent vanadium—that is, there is a dynamic equilibrium, VIII=IV. In the ascidians the physiological role of vanadium is associated with oxidation-reduction processes—electron transfer by means of the so-called vanadium system, which is probably of physiological significance in other organisms as well—rather than with oxygen and carbon-dioxide transport. REFERENCESSMeerson, G. A., and A. N. Zelikman. Metallurgiia redkikh metallov. Moscow, 1955.Poliakov, A. Iu. Osnovy metallurgii vanadiia. Moscow, 1959. Rostoker, W. Metallurgiia vanadiia. Moscow, 1959. (Translated from English.) Kieffer, R., and H. Braun. Vanadii, niobii, tantal. Moscow, 1968. (Translated from German.) Spravochnik po redkim metallam. Moscow, 1965. Pages 98-121. (Translated from English.) Tugoplavkie materialy v mashinostroenii: Spravochnik. Moscow, 1967. Pages 47-55, 130-32. Koval’skii, V. V., and L. T. Rezaeva. “Biologicheskaia rol’ vanadiia u astsidii.” Uspekhi sovremennoi biologii, 1965, vol. 60, issue 1(4). Bowen, H. J. M. Trace Elements in Biochemistry. London-New York, 1966. IU. I. ROMAN’KOV and V. V. KOVAL’SKII vanadium[və′nād·ē·əm]vanadiumvanadiumvanadium[vah-na´de-um]va·na·di·um (V),(vă-nā'dē-ŭm),vanadiumA metallic element (atomic number 23; atomic weight 50.94) present in trace amounts in the environment, which has an uncertain role in humans. Some data suggest that vanadium may lower serum glucose; participate in cholesterol, triglyceride and bone metabolism and in hormone production; and possibly protect against cancer. Vanadium is present in fish, liver, nuts, root vegetables, vegetable oils and whole grains; a vanadium deficiency state is not known to exist in humans.va·na·di·um(vă-nā'dē-ŭm)See VA vanadium
Synonyms for vanadium
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vanadium - a soft silvery white toxic metallic element used in steel alloys; it occurs in several complex minerals including carnotite and vanadinite