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METALLURGY OF ALUMINUM PowerPoint Presentation
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METALLURGY OF ALUMINUM

METALLURGY OF ALUMINUM

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METALLURGY OF ALUMINUM

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  1. METALLURGY OF ALUMINUM

  2. PROPERTIES • the lightest of the common metals (except with Mg) with density = 2.7 g/cc (1/3 the density of Cu). • soft and malleable at ordinary temperature (becomes brittle when heated to above 150oC). • silvery white in color • an amphoteric metal • good conductor of heat and electricity • an active metal but it does not corrode

  3. OCCURENCE Aluminum is the most abundant and the 3rd plentiful element on the earth’s crust. The elemental form does not occur in nature, its principal ore is bauxite. The major sources of aluminum are: • bauxite, Al2O3.H2O • cryolite, Na3AlF6 • corundum, Al2O3 • orthoclase, KalSi3O8 • beryl, Be3Al2Si6O18

  4. USES • its chief use is in automobile and aircraft construction. • kitchen utensils, aluminum foil and beverage cans • high voltage transmission line • used as solid propellant for rockets • in the welding of iron and steel.

  5. PREPARATION • Aluminum is usually prepared from bauxite. • Hall Process reduces bauxite to aluminum. • The cell contains a series of carbon (graphite) anodes. • The cathode is also made of carbon and constitutes the lining inside the cell.

  6. HALL PROCESS

  7. The aluminum oxide from bauxite is melted with cryolite to form 5% solution. The oxide dissociates as follows: Al2O3 2Al+3 + 3O-2 • The mixture is electrolyzed to produce aluminum and oxygen gas: Anode : 3 [2O-2 - 4e- O2] Cathode : 4 [Al+3 + 3e- Al] •  The overall reaction is: 2Al2O3 4Al + 3O2 • Oxygen gas reacts with the carbon anodes to form monoxide, which escapes as a gas. The liquid aluminum metal (m.p. 660.2oC) sinks to the bottom of the vessel from which it can be drawn from time to time.