Алюминий

Описание

Although aluminum was one of the last metals to be commercialized, it has been recognized for centuries. Aluminum was first recognized by the Romans as an astringent substance, and they called it ‘alum.’ By the middle ages it was manufactured as ‘alum stone,’ a subsulfate of alumina and potash. In 1825, Hans C. ?ersted was able to isolate a few drops of the raw material, and by 1886 it had patents from both Charles Martin Hall of the United States and Paul-Louis-Toussaint Heroult of France. Aluminum was commercialized in industry by the end of the nineteenth century.

Химические свойства

Aluminum metallic powder is a light, silvery-white to gray, odorless powder. Aluminum metallic powder is reactive and flammable. Aluminum is normally coated with a layer of aluminum oxide unless the particles are freshly formed. There are two main types of aluminum powder: the “fl ake” type made by stamping the cold metal and the “granulated” type made from molten aluminum. Pyro powder is an especially fi ne type of “fl ake” powder. Aluminum powders are used in paints, pigments, protective coatings, printing inks, rocket fuel, explosives, abrasives, and ceramics; the production of inorganic and organic aluminum chemicals; and as catalysts. Pyro powder is mixed with carbon and used in the manufacture of fi reworks. The coarse powder is used in aluminothermics.

Физические свойства

Pure metallic aluminum is not found in nature. It is found as a part of compounds,especially compounded with oxygen as in aluminum oxide (Al₂O₃). In its purified form, aluminumis a bluish-white metal that has excellent qualities of malleability and ductility. Purealuminum is much too soft for construction or other purposes. However, adding as little as1% each of silicon and iron will make aluminum harder and give it strength.
Its melting point is 660.323°C, its boiling point is 2,519°C, and its density is 2.699 g/cm³.

Физические свойства

Emissivity of Al
Clean polished foil: 0.04 (300 K), 0.02 (78 K), 0.011 (2 K, λ: 14 mm)
Electrolytic polished Al after annealing: 0.07 (1000 K), 0.04 (500 K), 0.03 (300 K)
Commercial products: 0.09 (373 K)

Изотопы

There are 23 isotopes of aluminum, and only one of these is stable. The singlestable isotope, Al-27, accounts for 100% of the element’s abundance in the Earth’scrust. All the other isotopes are radioactive with half-lives ranging from a few nanosecondsto 7.17×10⁺¹⁵ years.

Происхождение имени

From the Latin word alumen, or aluminis, meaning “alum,” which is a bitter tasting form of aluminum sulfate or aluminum potassium sulfate.

Вхождение

Aluminum is the third most abundant element found in the Earth’s crust. It is found inconcentrations of 83,200 ppm (parts-per-million) in the crust. Only the nonmetals oxygenand silicon are found in greater abundance. Aluminum oxide (Al₂O₃) is the fourth mostabundant compound found on Earth, with a weight of 69,900 ppm. Another alum-typecompound is potassium aluminum sulfate [KAl(SO₄)₂?12H₂O]. Although aluminum is notfound in its free metallic state, it is the most widely distributed metal (in compound form) onEarth. Aluminum is also the most abundant element found on the moon.
Almost all rocks contain some aluminum in the form of aluminum silicate minerals foundin clays, feldspars, and micas. Today, bauxite is the major ore for the source of aluminummetal. Bauxite was formed eons ago by the natural chemical reaction of water, which thenformed aluminum hydroxides. In addition to the United States, Jamaica and other Caribbeanislands are the major sources of bauxite. Bauxite deposits are found in many countries, butnot all are of high concentration.

Характеристики

Alloys of aluminum are light and strong and can easily be formed into many shapes—thatis, it can be extruded, rolled, pounded, cast, and welded. It is a good conductor of electricityand heat. Aluminum wires are only about 65% as efficient in conducting electricity as arecopper wires, but aluminum wires are significantly lighter in weight and less expensive thancopper wires. Even so, aluminum wiring is not used in homes because of its high electricalresistance, which can build up heat and may cause fires.
Aluminum reacts with acids and strong alkali solutions. Once aluminum is cut, the freshsurface begins to oxidize and form a thin outer coating of aluminum oxide that protects themetal from further corrosion. This is one reason aluminum cans should not be discarded inthe environment. Aluminum cans last for many centuries (though not forever) because atmosphericgases and soil acids and alkalis react slowly with it. This is also the reason aluminumis not found as a metal in its natural state.

Использование

As pure metal or alloys (magnalium, aluminum bronze, etc.) for structural material in construction, automotive, electrical and aircraft industries. In cooking utensils, highway signs, fencing, containers and packaging, foil, machinery, corrosion resistant chemical equipment, dental alloys. The coarse powder in aluminothermics (thermite process); the fine powder as flashlight in photography; in explosives, fireworks, paints; for absorbing occluded gases in manufacture of steel. In testing for Au, As, Hg; coagulating colloidal solutions of As or Sb; pptg Cu; reducer for determining nitrates and nitrites; instead of Zn for generating hydrogen in testing for As. Forms complex hydrides with lithium and boron, such as LiAlH4, which are used in preparative organic chemistry.

Методы производства

Aluminum production involves four main steps: bauxite mining,refining of bauxite to yield alumina; electrolytic reduction of alumina to yield aluminum; and aluminum casting into ingots.

Определение

aluminium: Symbol Al. A silverywhitelustrous metallic element belongingto group 3 (formerly IIIB) ofthe periodic table; a.n. 13; r.a.m.26.98; r.d. 2.7; m.p. 660°C; b.p.2467°C. The metal itself is highly reactivebut is protected by a thintransparent layer of the oxide, whichforms quickly in air. Aluminium andits oxide are amphoteric. The metalis extracted from purified bauxite(Al₂O₃) by electrolysis; the mainprocess uses a Hall–Heroult cell butother electrolytic methods are underdevelopment, including conversionof bauxite with chlorine and electrolysisof the molten chloride. Pure aluminiumis soft and ductile but itsstrength can be increased by workhardening.A large number of alloysare manufactured; alloying elementsinclude copper, manganese, silicon,zinc, and magnesium. Its lightness,strength (when alloyed), corrosion resistance,and electrical conductivity(62% of that of copper) make it suitablefor a variety of uses, includingvehicle and aircraft construction,building (window and door frames),and overhead power cables. Althoughit is the third most abundantelement in the earth’s crust (8.1% byweight) it was not isolated until 1825by H. C. Oersted.

Общее описание

Aluminum metal held above melting point of 1220°F (660°C) for ease in handling. Cools and solidifies if released. Contact causes thermal burns. Plastic or rubber may melt or lose strength upon contact. Protective equipment designed for chemical exposure only is not effective against direct contact. Take care walking on the surface of a spill to avoid stepping into a pocket of molten aluminum below the crust. Do not attempt to remove aluminum impregnated clothing because of the danger of tearing flesh if there has been a burn.

Реакции воздуха и воды

Violent reaction with water; contact may cause an explosion or may produce a flammable gas (hydrogen). Moist air produces hydrogen gas. Does not burn on exposure to air.

Опасность

Aluminum dust and fine powder are highly explosive and can spontaneously burst intoflames in air. When treated with acids, aluminum chips and coarse powder release hydrogen.The heat from the chemical reaction can then cause the hydrogen to burn or explode. Purealuminum foil or sheet metal can burn in air when exposed to a hot enough flame. Fumesfrom aluminum welding are toxic if inhaled.

Угроза здоровью

Exposures to aluminum metallic powder have been known to cause health effects with symptoms such as irritation, redness, and pain to the eyes, coughing, shortness of breath, irritation to the respiratory tract, nausea, and vomiting in extreme cases. In prolonged periods of inhalation exposures, as in occupational situations, aluminum metallic powder is known to cause pulmonary fi brosis, numbness in fi ngers, and (in limited cases) brain effects. Workers with pre-existing skin disorders, eye problems, or impaired respiratory function are known to be more susceptible to the effects of aluminum metallic powder.

Пожароопасность

Substance is transported in molten form at a temperature above 705°C (1300°F). Violent reaction with water; contact may cause an explosion or may produce a flammable gas. Will ignite combustible materials (wood, paper, oil, debris, etc.). Contact with nitrates or other oxidizers may cause an explosion. Contact with containers or other materials, including cold, wet or dirty tools, may cause an explosion. Contact with concrete will cause spalling and small pops.

Промышленное использование

Alloying aluminum with various elementsmarkedly improves mechanical properties,strength primarily, at only a slight sacrifice indensity, thus increasing specific strength, orstrength-to-weight ratio. Traditionally, wroughtalloys have been produced by thermomechanicallyprocessing cast ingot into mill productssuch as billet, bar, plate, sheet, extrusions, andwire. For some alloys, however, such mill productsare now made by similarly processing“ingot” consolidated from powder. Such alloysare called PM (powder metal) wrought alloysor simply PM alloys. To distinguish the traditionaltype from these, they are now sometimesreferred to as ingot-metallurgy (IM) alloys oringot-cast alloys. Another class of PM alloysare those used to make PM parts by pressingand sintering the powder to near-net shape.There are also many cast alloys. All told, thereare about 100 commercial aluminum alloys.

Возможный контакт

Most hazardous exposures to aluminum occur in smelting and refining processes. Aluminum is mostly produced by electrolysis of Al2O3 dissolved in molten cryolite (Na3AlF6). Aluminum is alloyed with copper, zinc, silicon, magnesium, manganese, and nickel; special additives may include chromium, lead, bismuth, titanium, zirconium, and vanadium. Aluminum and its alloys can be extruded or processed in rolling mills, wire works, forges, or foundries; and are used in the shipbuilding, electrical, building, aircraft, automobile, light engineering, and jewelry industries. Aluminum foil is widely used in packaging. Powdered aluminum is used in the paints and pyrotechnic industries. Alumina, emery, and corundum has been used for abrasives, refractories, and catalysts; and in the past in the first firing of china and pottery.

Канцерогенность

Most animal studies have failed to demonstrate carcinogenicity attributable to aluminum administered by various routes in rats, rabbits, mice, and guinea pigs. Some of these studies even suggested some antitumor activity. However, aluminum was found to cause cancer in a few experimental studies such as sarcomas in rats when implanted subcutaneously. This observation was attributed to the dimensions of the implants rather than the chemical composition.
Significantly increased incidence of gross tumors was reported in male Long Evans rats and lymphoma leukemia in female Swiss mice given aluminum potassium sulfate in drinking water respectively for 2–2.5 years. A dose–response relationship could not be determined for either species because only one dose of aluminum was used and the type of tumors and organs in which they were found were not specified.

Экологическая судьба

Aluminum binds diatomic phosphates and possibly depletes phosphate, which can lead to osteomalacia. High aluminum serum values and high aluminum concentration in the bone interfere with the function of vitamin D. The incorporation of aluminum in the bone may interfere with deposition of calcium; the subsequent increase of calcium in the blood may inhibit release of parathyroid hormones by the parathyroid gland. The mechanism by which aluminum concentrates in the brain is not known; it may interfere with the blood brain barrier.

хранилище

Aluminum metallic powder should be kept stored in a tightly closed container, in a cool, dry, ventilated area, protected against physical damage and isolated from sources of heat, ignition, smoking areas, and moisture. Aluminum metallic powder should be kept away from acidic, alkaline, combustible, and oxidizing materials and separate from halogenated compounds.

Перевозки

UN1309 Aluminum powder, coated, Hazard Class: 4.1; Labels: 4.1-Flammable solid. UN1383 Pyrophoric metals, n.o.s. or Pyrophoric alloys, n.o.s., Hazard Class: 4.2; Labels: 4.2-Spontaneously combustible material, Technical Name Required. UN1396 Aluminum powder, uncoated, Hazard Class: 4.3; Labels: 4.3-Dangerous when wet material. NA9260 (North America) Aluminum, molten, Hazard class: 9; Labels: 9-Miscellaneous hazardous material.

Структура и конформация

The space lattice of Al belongs to the cubic system, and its face centered cubic lattice has a lattice constant of a=0.404145 nm (25 ℃).

Несовместимости

Aluminum powder forms an explosive mixture with air and is a strong reducing agent that reacts violently with oxidizers, strong bases; strong acids; somehalogenated hydrocarbons; nitrates, sulfates, metal oxides and many other substances. Keep away from combustible materials.

Утилизация отходов

Consult with environmental regulatory agencies for guidance on acceptable disposalpractices. Generators of waste containing this contaminant (≥100 kg/mo) must conform with EPA regulations governing storage, transportation, treatment, and waste disposal of Aluminum Oxide-Disposal in a sanitary landfill. Mixing of industrial process wastes and municipal wastes at such sites is not encouraged however. Aluminum powder may be recovered and sold as scrap. Recycling and recovery is a viable option to disposal for aluminum metal and aluminum fluoride (A-57).

Меры предосторожности

The dry powder is stable but the damp or moist bulk dust may heat spontaneously and form flammable hydrogen gas. Moist aluminum powder may ignite in air, with the formation of flammable hydrogen gas and a combustible dust. Powdered material may form explosive dust-air mixtures. Contact with water, strong acids, strong bases, or alcohols releases flammable hydrogen gas. The dry powder can react violently or explosively with many inorganic and organic chemicals