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Introduction
Aluminium (Al)
is the
13th element of the periodic table and is cat-
egorized as a poor metal because it is softer and has a reduced melting
point as compared to iron or titanium.[7] Being the most abundant metal
in the Earth’s crust, Al is estimated to comprise roughly 8% by weight
of
the planets solid surface and is typically refined from bauxite ore.[7]
More
importantly though is its natural resistance to corrosion; under normal
conditions Al is insoluble in water, and when exposed to the atmosphere
the surface undergoes an oxidation reaction to form a hard thin layer of
aluminum oxide, also called alumina, which effectively seals the metal
sur-
face from further corrosion.[7] This unique property, along with its
high
strength to weight ratio, makes Al critically important to the
aero-space
industry, and it is used extensively in modern transportation and
engineer-
ing applications.
However the thin layer of alumina is on the order of
2-3 nanometers
(nm) thick and rubs off easily with normal handling.[7] Thus it is
desirable
to artificially thicken the oxidation layer not only for a more durable
finish,
but also to increase the hardness of the object and make it more
receptive
to dyes, clear coats and lubricating agents. This can be achieved
through
a process known as electrochemical anodization, which forms an alumina
layer on the order of 75-150nm thick comprised of uniformly distributed
nanopores or tiny holes.
If the anodized surface is not sealed it will
continue to oxidize in-order
to fill the nanopores; many common devices are made from anodized Al
which is dyed and then sealed, resulting in a bright durable finish
that will
not crack or peel like powder-coated metals or painted
plastics.[7] How-
ever the nanopores resulting from the anodization process are themselves
useful as templates for the growth and formation of nano-structured de-
vices such as carbon nanotubes, quantum wells, nanowires and quantum
dots.[7] It is the aim of this website to explore the anodization
process in
the context of varying reaction conditions for the formation of
nanoporous
alumina templates.
P. D. Wallace
UAF Spring 09'
Steve's Templates
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