Aluminum

History

In 1807, Davy Humphry, after having discovered that the Sodium and the Potassium entered the composition of the Alun, supposes that it is there as another Métal, as it baptizes “aluminum” (in Latin, “alum” says “alumen”). Pierre Berthier discovers in a mine close to the Beam-of-Provence in 1821 an ore containing more 50 % of aluminum oxide. This ore will be called Bauxite.

One generally allots the discovery and the insulation of aluminum to Friedrich Wöhler in 1827. However, two years earlier, the Danish chemist and physicist Hans Christian Ørsted had succeeded in producing the impure shape of metal. Wöhler was the first to highlight the chemical and physical properties of the aluminum, of which most notable is lightness.

The French chemist Henri Holy-Claire Deville improves in 1846 the method of Wöhler by reducing the ore by the Sodium. He publishes his research in a book in 1856. This method is used through all Europe for manufacture of aluminum, but it remains extremely expensive. Metal is used besides to manufacture jewels, whose value obviously will be reduced to nothing a few decades later.

1855 : New metal is exposed to the World Fair of Paris.
the First producing aluminum industrial site in the world settles with Salindres in the Gard.
1876 : William Frishmuth carries out first cast aluminum. In 1884, it carries out the cap of the Washington Monument in this metal.
1886 : in an independent way, Paul Héroult and Charles Martin Hall discover a new method of production of aluminum by noticing that it is possible to dissolve the Alumine and to break up the mixture by electrolysis (proceeded Héroult-Hall) to give rough metal in fusion. For this discovery, Hall obtains a patent (400655) the same year. This process makes it possible to obtain relatively economic aluminum of manner. The method developped at the point by Héroult and Hall is always used today.
1887 : Karl Josef Bayer describes a known method under the name of proceeded Bayer to obtain alumina starting from bauxite. This discovery makes it possible to insert aluminum in the era of the mass production.
1888 : the first aluminum production companies are founded in Suisse, France and with the the United States.

Properties

Physical properties

Aluminum is a metal soft, light, but resistant with an aspect money-gray chechmate, due to a thin layer of oxidation of 5 with 10 Nm which is formed quickly when one exposes it to the air and which prevents corrosion from progressing under conditions chemical normal of exposure. This film is formed spontaneously very quickly when aluminum is put in contact with a medium oxidizing like the oxygen of the air. With the difference of the majority of metals, it is usable even if it is oxidized on the surface. One can even say that without this oxide coating, it would be unsuitable with the majority of its applications. It is possible artificially to increase the thickness of this layer of oxidation by Anodisation, which makes it possible to increase protection and to decorate the parts by coloring the oxide coating. Contrary to the aluminum which is a very good conducting, the aluminum oxide is excellent a Isolant.

Aluminum has a Densité (2,7) approximately three times lower than that of the Acier or Cuivre; it is malleable, ductile and easily machined and moulded. It has an excellent corrosion resistance and a great longevity. It is also nonmagnetic and does not cause sparks. It is the second most malleable metal and the most ductile sixth.

Chemical properties

In solution, aluminum is most generally in the form of Ion S Al 3+ . It oxidizes slowly cold and quickly hot to form the Alumine Al2O3. The action of the acids on aluminum produces the ion referred to above.

Al reaction with produced NaOH of aluminate NaAlO2 sodium and the gas dihydrogene H2, according to the equation: 2 Al + 2 NaOH + 2:2 O --> 2 NaAlO2 + 3 H2.

The aluminum hydroxides are obtained in general by precipitating a solution containing of cations Al 3+ using a base. This method makes it possible to form according to the conditions of precipitation various phases crystallographic such as the bayerite, boehmite, the gibbsite.

Toxicology

Aluminum is recognized for its harmful effects with high amount on the Nervous system (it is however an essential trace element, its deficiency involving a intellectual delay). People exposed to aluminum high rates (following one or more Vaccination S , or a treatment of Dialyze) can develop complications with the level of the central nervous system, like the Encéphalopathie, the epilepsy and of the disorders of memory. The accumulation of aluminum in the organization can also play a part in other evils like the Psoriasis, the hepatorenal insufficiencies chronic, the Anémie, the Ostéomalacie (breakable or soft bones), intolerance with the Glucose and the cardiac arrests at the human ones. The cells of the brain of the patients reached of Alzheimer contain from 10 to 30 times more aluminum than the normal.

One can find aluminum in the Aliment S, the Eau, the deodorants, the vaccines and the Médicament S. the kitchen utensils and the aluminum paper can also release some (in generally negligible quantity) in food. This is why its use in manufacture of water pipelines is prohibited in several countries.

Remarkable alloys and uses

In tonnage and value, aluminum is the metal more used after the Fer, thanks to its lightness and its good electric and thermal conductivity. Pure aluminum is soft and fragile, but with minor amounts of Cuivre, Magnésium, Manganèse, Silicium and other elements, it can form Alliage S with the varied properties.

Among the sectors using aluminum, one can quote:

transport (Automobile S, Plane S, Truck S, Train S, Boat X, etc);
the Packing (cans, aluminum foil, quills, small boats, Aerosol S, etc) and in particular packing food;
construction (windows, doors, etc);
consumer goods (apparatuses, kitchen utensils etc);
the electric wires (the conductivity of aluminum represents only 60 % of that of the Copper, but aluminum is lighter and less expensive);
of very pure aluminum (99,980 with 99,999 %) is employed in electronic and for the CD.

In Geomorphology and Paléosismologie, the isotope 26 Al, created by the cosmic rays, is used for the Datation by cosmogenic isotopes of surfaces or the determination of rate of erosion.

Layers

Aluminum is an abundant element in the Earth's crust but it is seldom in its pure form. It is the third most abundant element in the Earth's crust (8% of the mass) after the Oxygène and the Silicium. Aluminum is very difficult to extract from the rocks which contain it and was thus a long time very rare and invaluable.

The principal aluminum ore is the Bauxite.

Production

See also: Extraction of alumina, Production of aluminum by electrolysis, List of aluminum producers

The Bauxite contains Alumine (Hello), that it is initially necessary to extract. For that the bauxite must be treated by a solution of Soude.

One obtains an Al precipitate (OH) which gives alumina by heating. Aluminum is extracted by electrolysis: alumina is introduced into tanks of electrolysis with additives like the Cryolithe (NaAlF) and aluminum fluoride (AlF) in order to lower the melting point of: 2040°C with 960°C.

The production of a ton of aluminum requires of 4 with 5 tons of bauxite. It requires between: 13000 and: 17000 kWh (between 47 and 61 GJ). During electrolysis, is emitted polluting gas such as Carbon dioxide (CO), Carbon monoxide (CO), aromatic hydrocarbons polycyclic (HAP), gas Sulfur dioxide (SO) and fluorides.

Statistics of production

The secondary worldwide production of aluminum starting from recycling rose with 7,6 MT in 2005, is 20 % of the total production of this metal.

Recycling

Aluminum has an excellent recyclability. To recycle aluminum, one simply makes it melt. In addition to the environmental benefit, the Recyclage of aluminum is much less expensive than the extraction starting from the ore of Bauxite. It requires 95 % of energy in less and one ton of recycled aluminum makes it possible to save four tons of bauxite. While jumping the stage of the electrolysis, which claims much energy, one avoids the pollutant emissions which are associated for him. Aluminum is quasi which can be recycled ad infinitum without losing its qualities, with the proviso of not melting in the same bath of alloys of different composition.

The recycling of aluminum is practiced since the years 1900 and does not cease progressing: in the aluminum consumption in Europe, the share of origin recycling passed from 50 % in 1980 with more 70 % in 2000. There exist various industrial dies of recovery of aluminum. In France, domestic aluminum is recovered with the Emballage S within the framework of the Recycling. In the sorting offices, aluminum is sorted manually or more usually thanks to Eddy current machines of sorting by . It is then crushed before being remelted by aluminum refiners to give again metal usable, called aluminum of the second fusion. The aluminum of the second fusion is used primarily for the manufacture of castings for car (blocks engine, cylinder heads, pistons, etc)

After the Second world war the shortage resulted in remelting alloys of aluminum to make of them parts not requiring precise mechanical characteristics, and in particular of the kitchen utensils. The composition of alloys obtained was not appreciated founders who qualified them “ cochonium ”. The pans thus built were pricked (pitting), under the effect of the acidity of food. The consequences of a polluted food were already evoked.

In certain countries in the process of development, the matter recycling not controlled containing aluminum still nowadays results in carrying out food ustensils with contents of harmful elements (nickel, copper, etc).

Nevertheless, the recycling of aluminum alloys, carried out seriously, with an accurate check of the composition, gives excellent results.

Pollution

Two types of pollution are generated by the production of aluminum:

a fluorinated pollution at the time of the transformation of alumina into aluminum.
Of the gas rejections above the tanks of electrolysis must be collected.

See too

Internal bonds

Institute of history of aluminum
List of aluminum producers

Extractive metallurgy of aluminum

Aluminum alloy

Alloys of aluminum for welding
Alloys of aluminum for foundry

Transformation of aluminum

Works aluminum smelting
Manufacture of the sheets and aluminum bands

External bonds

Aluminum-Scout - the interactive platform D `information and of exchange of the field of L `aluminum
Micrographies comparing brilliant surface and the matt surface of the aluminum foil
aluMATTER - a Web site freely accessible which aims at providing innovating tools for formation on line and interactive relating to science and technologies from aluminum
Site of the Institute of history of aluminum (IHA).

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