Scientists are busy looking for a compound which they say is going to replace diamond as the hardest substance
CARBON is a remarkable element; not
only is it the basis of life as we know it, it
also has an amazing diversity in its inorganic form. From coal to graphite to
diamond and carbon-60, the variety in
its structure and properties is
unmatched. Diamond is the hardest
substance known to us and finds many
uses in industry because of this unique
property. Scientists have been searching
for another carbon compound which
they believe will be even harder than
diamond.
In the late '70s and early '80s, several
theoretical studies indicated that there
could exist a compound of carbon and
nitrogen, carbon nitride, which would
be harder than diamond. Since then,
many experimental groups have tried to
search for this compound without any
success. Nevertheless, the search for this
family of compounds still continues.
Last year, a team of Chinese scientists reported success in creating the
compound by graphite ablation in
atomic nitrogen. Ablation is a process of
removal of material from the surface
by decomposition or vaporisation.
Another group in Australia has also
reported making a film using sputtering
(in which carbon and nitrogen atoms
are vaporised from solid targets using
ions). The structure of these films does
not indicate that they have the desired
hardness.
Recently, Charles Lieber and his
group have reported some success in
pr paring the desired family of compounds. Using the ablation method
where a pulsed laser beam vaporises the
cafbon from a rotating graphite target
and a radio frequency gun breaks down
nitrogen molecules to an atomic nitrogen beam, they claim to have made a
-thin film which has properties like those
addicted. Lieber and co-workers used
annealing to get the desired purity.
The annealed films have electrical
properties like diamond films, but
their hardness is much less. (Nature,
March 14, 1996).
We are a voice to you; you have been a support to us. Together we build journalism that is independent, credible and fearless. You can further help us by making a donation. This will mean a lot for our ability to bring you news, perspectives and analysis from the ground so that we can make change together.
Comments are moderated and will be published only after the site moderator’s approval. Please use a genuine email ID and provide your name. Selected comments may also be used in the ‘Letters’ section of the Down To Earth print edition.