The National Geo TV station presented a program about 'super
diamonds' last night.
The part I found especially interesting was how much more durable
they are compared to natural mined diamonds. The reason was that for
the vapor deposition type, where they’re growing those big, but thin,
films, the starting point is a dusting of tiny seed crystals on which
the resulting film grows as the growth on the seed crystals (perhaps
a very fine grade diamond grit?) intergrows to form not a single
crystal, but a structure that sounded like it would compare to
natural diamond, the same way chalcedony compares to single crystal
quartz. The intergrown random orientation means there are no longer
cleavage planes, for one thing, to worry about. It sounded like it
actually results in an increase in hardness too, and perhaps a
substantial one. Interesting, if true. One always has to account for
the fact that between what the narrator says on such shows, there’s a
filter of copywriters and producers and others between that final
narrative and the original expert source of the info, so sometimes
things get emphasized or mistated. Still, interesting.
And then there was the bit about how they grew super strong diamond
anvil crystals for the high pressure equipment. That was puzzling
too. They said they also used chemical vapor depostion to grow a seed
crystal larger, then used high temp/high pressure treatment to make
it further more durable, dense, hard, or whatever. The image on the
screen showed what looked like a transparent crystal. It would need
to be, actually, in order to observe what is happening between the
diamond anvils in the experimental work done. But it leads me to
wonder whether that crystal is still a polycrystaline structure, or
if it differs from natural diamond crystals in some other way.
Definately interesting stuff.