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championsacademy · 2 years

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#Aluminium or #Aluminum is a #ChemicalElement with the symbol Al and #AtomicNumber 13. Aluminium has a #Density lower than those of other common #Metals, at approximately one third that of #Steel.

It has a great affinity towards #Oxygen, and forms a protective layer of #Oxide on the surface when exposed to air.

Aluminium visually resembles silver, both in its color and in its great ability to reflect light. It is soft, non-magnetic and #Ductile. It has one stable #Isotope, 27Al; this isotope is very common, making aluminium the twelfth most common element in the Universe. The radioactivity of 26Al is used in radiodating.

Chemically, aluminium is a #PostTransition #Metal in the #BoronGroup; as is common for the group, aluminium forms compounds primarily in the +3 oxidation state.

The aluminium cation Al3+ is small and highly charged; as such, it is polarizing, and bonds aluminium forms tend towards covalency. The strong affinity towards oxygen leads to aluminium's common association with oxygen in nature in the form of oxides; for this reason, aluminium is found on Earth primarily in rocks in the crust, where it is the third most abundant element after oxygen and silicon, rather than in the mantle, and virtually never as the free metal.

The discovery of aluminium was announced in 1825 by Danish #Physicist #HansChristianØrsted.

The first #Industrial production of aluminium was initiated by French chemist Henri Étienne Sainte-Claire Deville in 1856. Aluminium became much more available to the public with the Hall–Héroult process developed independently by French engineer Paul Héroult and American engineer Charles Martin Hall in 1886, and the mass production of aluminium led to its extensive use in industry and everyday life.

In World Wars I and II, aluminium was a crucial strategic resource for #Aviation. In 1954, aluminium became the most produced #NonFerrous metal, surpassing copper.

In the 21st century, most aluminium was consumed in #Transportation, #Engineering, #Construction, and #Packaging in the #UnitedStates, Western #Europe, and #Japan.

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adto-office-booth · 4 years

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How Aluminum is Made

In many ways, aluminum is the perfect metal. It is strong, light, resistant to heat and corrosion and a good conductor of electricity. On top of that, it is plentiful and inexpensive.

Aluminum is also the most abundant metal in the Earth’s crust and the third most abundant element after oxygen and silicon. However, it was not until 1809 that English chemist Sir Humphry Davy formally identified and named it.

Aluminum is made in the following stages:

#1 Finding Aluminum Ore

#2 Mining Aluminum

#3 Refining the Bauxite

#4 Aluminum Smelting

#1 Finding Aluminum Ore

Aluminum tends to combine with other elements and rarely exists in nature in its pure metallic form. Aluminum compounds are found in most common rock types including clay, slate, shale, granite, and anorthosite.

The most important aluminum ore is bauxite, a rock containing about 52% aluminum oxide with impurities of iron oxide, silica, and titania. Bauxite is commonly found in deposits on or close to the Earth’s surface throughout many parts of the world, including Europe, Asia, Australia, and South America.

#2 Mining Aluminum

Geologists locate bauxite deposits by taking samples and conducting investigatory drilling. When deposits are found, they are mined in open pits. The earth is blasted loose and the bauxite is extracted using power shovels or draglines.

90% of all mined bauxite is made into alumina to be smelted into aluminum. The remaining 10% is used for other purposes including the manufacture of abrasives, furnace linings, and proppants for the oil industry. It takes 4 tons of high-quality bauxite to produce 2 tons of alumina, from which 1 ton of aluminum can be made.

#3 Refining the Bauxite

The bauxite is refined using the Bayer process which was first developed by Karl Joseph Bayer in 1888. The Bayer process has four steps: digestion, clarification, precipitation, and calcination.

1) Digestion

The bauxite is ground, mixed with caustic soda and pumped into pressure tanks where steam heat and pressure is applied. This causes the caustic soda to react with the aluminum compounds in the bauxite to form a solution of sodium aluminate. The unwanted impurities are left behind in what is known as red mud.

2) Clarification

Next, the sodium aluminate solution is passed through blow-off tanks where the pressure is reduced to atmospheric pressure. The red mud is removed with the use of clarifying agents and cloth filters. The clarified solution is then cooled in heat exchangers and pumped into tall silos.

3) Precipitation

Aluminum hydroxide seed crystals are added to the sodium aluminate solution to cause precipitation. During this process, the aluminum becomes solid. This results in large aluminum crystals which are filtered and washed to remove water and other impurities.

4) Calcination

Now the aluminum hydroxide crystals are subjected to calcination, a thermal treatment process where the supply of air is controlled. Rotary kilns are used to heat the crystals to temperatures over 960° C which removes any remaining impurities, leaving a fine white powder known as alumina, or aluminum oxide.

#4 Aluminum Smelting

Smelting is the process during which aluminum is extracted from the alumina. This is carried out by the Hall-Héroult process, which was invented in 1886 by Charles Martin Hall and Paul Héroult.

The smelting takes place in steel reduction pots filled with molten electrolyte, where carbon anodes are used to pass an electric current through the electrolyte. Alumina is then added to the molten surface. The electric current deposits molten aluminum which can be collected and siphoned off.

#aluminum

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