01/20/08 The Future of Carbon
Carbon is undoubtedly the most important chemical element on Earth. It is the element
of life and the source of most of the world's energy in the form of fossil fuels.
Carbon has properties that make it the ideal chemical for life, the ultimate source
for fossil fuels, but its role extends far beyond its importance as as a biochemical.
As we aim for a decrease in carbon dependency for energy, this versatile chemical
element will have many diverse and greener roles for the future.
The utility of the carbon atom comes because it has four electrons that can bond
with other atoms, including other carbon atoms. This is what makes it possible for
the long chains in the molecules of life.
Diamond and graphite are both crystalline forms of carbon to carbon bonds, the only
difference being the arrangement of carbon atoms in the crystal lattice.
Diamond is hard because the interlocking lattice of bonded carbon atoms makes a strong
structure.
Graphite is slippery because it consists of thin sheets of bonded carbon atoms. The
bonds between carbon atoms are strong as in the diamond lattice, but the bonds between
the sheets are weak allowing the layers to slide over one another.
The strength of graphite sheets has led to the development of a new generation of
composite materials made from carbon fiber impregnated with resin similar to the
way fiberglass cloth and resin are used.
The difference is that the carbon fibers are one hundred times stronger than steel
but weigh only one-sixth as much.
Most carbon fibers are made from a rayon-like material, polyacrylonitrile (PAN).
Others are made from rayon, nylon, or petroleum pitch. The exact composition of precursor
materials varies among companies and is generally proprietary.
Processing includes low temperature oxidation to drive out hydrogen and nitrogen
molecules followed by high temperature baking in an oxygen-free environment.
Each fiber consists of narrow sheets of graphite that roll up and join together at
the end to form interlocking hollow strands that are one-tenth the thickness of a
human hair.
An electrochemical bath roughens the surface of the fiber to make it more bondable
to composites before fibers are woven into fabric to give multidirectional strength.
The list of consumer products made from carbon fiber composites is long and growing
longer.
Carbon fiber composites are used to make aircraft and spacecraft parts, racing car
bodies, golf club shafts, tennis rackets, bicycle frames, fishing rods, automobile
springs, sailboat masts, musical instruments, and blades for huge industrial wind
generators, o name a few.
The most dramatic and revolutionary use of carbon fiber technology is in the Boeing
787 "Dreamliner", which is now scheduled for delivery in early 2009.
The fuselage and wings of the Dreamliner are made from carbon fiber composite, making
the airframe much lighter than if it were made of aluminum or titanium.
With lighter weight and fuel-efficient engines the innovations of the 787 will save
millions of dollars over the life of the aircraft.
It will also provide greater comfort for passengers. The stronger airframe will allow
the cabin pressure to be maintained at a higher level and the noncorrosive composite
will allow for higher humidity in the cabin.
The Dreamliner is only one of many innovations that the twenty-first century will
see from the use of carbon fibers.
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Richard Brill, Professor of Science at Honolulu Community College (honolulu.hawaii.edu/~rickb),
teaches earth and physical science and investigates life and the universe. His column
is published on the first and third Sunday of every month. E-mail questions and comments
to rickb@hcc.hawaii.edu
"The Future of Carbon" ©2008 by RCBrill. All rights reserved.