From: "Gerald L. Hurst" <glhurst@onr.com>
Newsgroups: alt.engr.explosives
Subject: Re: Shock wave method for making diamonds
Date: Tue, 08 Jun 1999 15:25:24 -0500

Cast iron is a metal matrix containing up to about 10% occluded graphite.

If a cast iron sample is subjected to a sufficiently intense shock pulse, the
graphite collapses into carbonado diamond (black diamond).

Direct application of an explosive charge does not produce sufficient
pressure for the transformation.  What does work is the impact of an
explosively propelled steel plate.

The plate is accelerated by a charge initiated by a plane wave generator.  It
is allowed to accelerate from contact  with the explosive across a space of
about 1.5 inches.  The plate receives an initial jump from the impact of the
detonation head and then is further accelerated by the push of the expanding
gases.

The net result of the explosive forces is a plate velocity of about 5
km/sec.  When the free-flying plate strikes the cast iron, the resultant
pressure pulse reaches some 30,000,000 psi, more than enough to compress the
carbon into diamond.

The function of the iron is to quench the newly-formed diamond bits before
they can revert to graphite.  This quenching only works for small particles,
so the process is used only to make diamond dust.

The dust is freed from the iron by dissolving the latter in acid.

The carbonado dust yields an X-ray pattern which is somewhat different from
normal diamond as a result of the random orientation of the crystal structure
as opposed to the more ordered form of diamond from slower natural or
synthetic processes.

In essence, the process mimics the formation of diamond from meteorite
impacts such as that which occurred at Canyon Diabolo in Arizona.

Jerry (Ico)

Newsgroups: sci.chem
From: ahahma@polaris.utu.fi (Arno Hahma)
Subject: Re: Making Diamonds
Message-ID: <C4n714.3L3@polaris.utu.fi>
Date: Mon, 29 Mar 1993 08:46:14 GMT

In article <1993Mar28.162130.8753@kth.se> tomas_e@LINK.Physchem.KTH.SE writes:

>The method used on an industrial scale to produce diamonds involves very
>high temperatures (somewhere 1000-2000 deg. C, I think), and extremly
>high pressures. The equipment used to produce these reaction conditions
>wouldn't fit into a high school chemistry lab, I'm afraid... The
>starting material is graphite mixed with small amounts of various other
>things, including some metal compounds which act as catalysts. I'm
>afraid I don't see any way you could do this in your chemistry lab.

Then there is still one way of making diamonds in large scale, without
the need for any high tech equipment - using aromatic explosives.
Russians do it this way, they produce industrial diamonds with
explosives, several tons annually.

The procedure is simple: mix carbon black into TNT, explode the charge
and collect the resulting soot. It will contain 20..50 % by its weight
of diamonds, depending on how lucky you are ;-). There is just one
problem: how to effectively collect the soot... Strong pressure
vessels are useful.

>Tomas Eriksson (tomas_e@physchem.kth.se)
>Dept. Physical Chemistry, Royal Institute of Technology, Stockholm, Sweden

ArNO
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