Aluminum
- The chemical element of atomic number 13, a light silvery-gray metal. Aluminum
is the most abundant metal in the earth's crust
- Obtained from the ore "Bauxite"
Al2O3 + SiO2 + TiO2 + Fe2O3
Properties of Aluminum
Lightweight - Aluminum is about one-third the weight of an equal volume of
copper, steel or brass.
Strength - Aluminum can withstand heavy loads and pressure; when alloyed
appropriately, its strength approaches that of steel.
High strength-to-weight ratio - The ratio of the tensile strength of aluminum,
divided by
density, is higher than any other metal.
Ductility - Aluminum is easy to cold work and fabricate.
Malleability - The vulnerability of aluminum to heat and pressure make it ideal for
extruding into formed, intricate shapes with ledges, grooves, hinges, screwholes
and interlocking parts.
Finishing - Aluminum can be finished with a variety of coatings and finishes such
as paint, lacquer, porcelain or organic coatings, which can be anodized to bond to
the metal.
Corrosion resistance - The formation of a microscopic film of aluminium oxide on
the surface of the metal protects it against the corrosive influences of water, salt
and other influences.
Resilient/Flexible
Electrical conductivity - Aluminum has twice the conductivity of an equal weight
of copper.
Thermal conductivity - Aluminum spreads heat or cooling energy evenly and
quickly.
Non-toxicity - Aluminum is ideal for packaging and cooking material finishes
because it is non-toxic.
Reflectivity - Aluminum reflects light and other forms of radiant energy.
Finishing - Aluminum can be finished with a variety of coatings and finishes such
as paint,
lacquer, porcelain or organic coatings, which can be anodized to bond to the metal.
Recyclability - Aluminum can be easily reclaimed and recycled into new, final
aluminum products.
Availability - Alumina is the most abundant metallic element in the earth's crust.
Cost-efficiency - Aluminum processing is inexpensive.
Extraction of Aluminum from its Ore
Hall-Heroult Process:
- The purified aluminum oxide is mixed with cryolite.
a mixture of sodium fluoride and aluminum fluoride
- and heated to about 980 degrees Celsius to melt the solids.
- The mixture melts at a much lower temperature than aluminum oxide would by
itself.
- The hot molten mixture is electrolyzed
- Aluminum ions are reduced to aluminum metal at the cathode
- At the anode, oxygen is produced from the oxide ions. The anode material is
carbon in the form of graphite, which also is oxidized
Bauxite Ore Processing:
- First the ore is mixed with a hot concentrated solution of sodium hydroxide.
- The NaOH will dissolve the oxides of aluminum and silicon but not other impurities
such as iron oxides, which remains insoluble.
- The insoluble materials are removed by filtration.
- process of passing a liquid or gas, such as air, through a filter in order to remove
solid particles.
- The solution which now contains the oxides of aluminum and silicon are next
treated by bubbling carbon dioxide gas through the solution.
- Carbon dioxide forms a weak acid solution of carbonic acid which neutralizes the
sodium hydroxide from the first treatment.
- This neutralization selectively precipitates the aluminum oxide, but leaves the
silicates in solution.
- Again filtration is used for the separation. After this stage the purified aluminum
oxide is heated to evaporate the water.
USES OF ALUMINUM
BUILDING AND CONSTRUCTION
Approximately one-fifth of the world's total consumption of aluminum is used
by the construction industry. Bridges, domes, and roofs of several big structures,
like markets, sports complexes, and stadiums make use of aluminum.
Its malleable nature and stylish, shiny appearance makes it suitable for home
dcor items, like window frames, door knobs, railings, grills, curtain bars, as well as
artifacts, indoor and outdoor furniture, doors, and interior panels. Aluminum can be
cut, welded, bonded, tapered, and joined with other material.
PACKAGING
Around one-fifth of the extracted aluminum is used in the packaging of foods,
beverages, pharmaceuticals, etc. Cans, trays, foils, bottles, thermos, utensils,
kettles, refrigerators, toasters, and saucepans are made of this element
aluminum helps protect the food items stored in it from other harmful
elements,
due to its corrosion Resistance, repels water, and is non-toxic, which reduces
spoilage of food items.
Transportation
aluminum is used in transportation. Aircraft carriers, trains, ships, boats,
buses, and other motor vehicles make use of aluminum because of its strength and
weightlessness. Frames, exteriors, wiring, and electrical systems in airplanes make
use of aluminum.
Electricity
Electrical equipment, power lines, and electricity make use of about 10%
aluminum. Its low density and high ductility is what makes it suitable for the
transmission of high voltage electricity over long distances.
