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Aeroquiz Editor's Note:
On October 19, the NASA Glenn and many other government websites
were temporarily taken offline following the terrorist attacks of 9/11/01
to ensure that dissemination of information regarding NASA is appropriate.
This website was reactivated on 12/5/01.
Week of 12/15/01:
Q:
Aluminum is by far the world's most widely-used aircraft building
material. It is the most abundant metal in the Earth's crust.
It has an excellent strength-to-weight ratio, it is easily machined
and formed, resistant to chemical corrosion, and is relatively
inexpensive. But it was not always inexpensive. In the 19th
century, aluminum was so rare and valuable it was displayed
before the public at Tiffany's jewelers. What happened that
allowed aluminum to become one of the most common building
materials today?
A:
Bauxite ore is mined as a source of aluminum, but in filtering out
all of the many impurities, what you are left with is alumina
(various oxides of aluminum). Stripping these oxidizing agents
away is very difficult (something akin to "unburning" a match),
yet necessary in order to reduce the alumina down to metallic aluminum.
In 1886, two 22-year-old scientists on opposite sides of the Atlantic,
Charles Hall of the USA and Paul L.T. Heroult of France, made the same
discovery -- molten cryolite (a sodium aluminum fluoride mineral)
could be used to dissolve alumina in order to produce metallic aluminum.
The key to the chemical reaction was the running of an electrical
current through the cryolite/alumina mixture.
The Hall-Heroult process remains in use today, and is what makes
large scale production of aluminum economically feasible.
Congratulations to Eric Foy.
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