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Press Release 04-023
Large Diamonds Made From Gas Are Hardest Yet
February 25, 2004
Arlington, Va.—Producing a material that is harder than natural
diamond has been a goal of materials science for decades. Now a
group headed by scientists at the Carnegie Institution's
Geophysical Laboratory in Washington, D.C., has produced gem-sized
diamonds that are harder than any other crystals and at a
rate up to 100 times faster than other methods used to
date. The process opens up an entirely new way of producing
diamond crystals for electronics, cutting tools and other
industrial applications.
"This is a great example of fundamental research that will not
only give us a better tool to duplicate conditions in the core of
the Earth, but will stimulate many other scientific, technical
and economic advances," said geologist James Whitcomb of the
National Science Foundation (NSF)'s division of earth sciences,
which funded the research.
"We believe these results are major breakthroughs in our field,"
said Chih-shiue Yan, lead author of the study published in the
Feb. 20, online Physica Status Solidi. "Not only were the
diamonds so hard they broke the measuring equipment, we were able
to grow gem-sized crystals in about a day."
The researchers developed a special high-growth rate chemical
vapor deposition (CVD) process to grow crystals. They then
subjected the crystals to high-pressure, high-temperature
treatment to further harden the material. In the CVD process,
hydrogen gases and methane gases are bombarded with charged
particles, or plasma, in a chamber. The plasma prompts a complex
chemical reaction that results in a "carbon rain" that falls on a
seed crystal in the chamber. Once on the seed, the carbon atoms
arrange themselves in the same crystalline structure as the seed.
This method has been used to grow diamond crystals up to 10
millimeters across and up to 4.5 millimeters thick.
CVD-produced crystals are very tough. "We noticed this when
we tried to polish them into brilliant cuts," said Yan. "They
were much harder to polish than conventional diamond crystals
produced at high pressure and high temperature." The researchers
then subjected the tough CVD crystals to high-temperature and
high-pressure conditions. The diamonds were heated to 2000° C and
put under pressures of 50,000 to 70,000 times atmospheric
pressure for 10 minutes. This final process resulted in the ultra
-hard material, which was at least 50 percent harder than
conventional diamonds.
The research was also supported by the U.S. Department of Energy,
the National Nuclear Security Agency, through the Carnegie/ DOE
Alliances Center, and the W. M. Keck Foundation. It was conducted
in collaboration with researchers at the Phoenix Crystal
Corporation and Los Alamos National Laboratory.
-NSF-
Media Contacts
Cheryl Dybas, NSF (703) 292-7734 cdybas@nsf.gov
Tina McDowell, Carnegie Institution (202) 939-1120 tmcdowell@pst.ciw.edu
The National Science Foundation (NSF) is an independent federal agency that
supports fundamental research and education across all fields of science and
engineering, with an annual budget of $6.06 billion. NSF funds reach all 50
states through grants to over 1,900 universities and institutions. Each year,
NSF receives about 45,000 competitive requests for funding, and makes over
11,500 new funding awards. NSF also awards over $400 million in
professional and service contracts yearly.
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