[ExI] Aerographite

[spike]

>...If you made a sphere of aerographite, covered with a gas non-permeable
membrane, for example a few layers of graphene, and partially evacuated the
inside, would it float in the air without being crushed by its pressure?

>...See here, aerographite weighs about 0.3 g per liter, and is pretty
stiff:

>...http://nextbigfuture.com/2012/07/aerographite-is-lightest-material.html#
more

>...Rafal


I can think of uses for it, but not this one.  You would be better off
filling your coated aerographite sphere with methane, which is cheap and
about half the density of air.  Helium is better but more expensive, and
hydrogen is better still, but more expensive than methane.  Heated air is
another possibility.  I would consider a large pressure differential as a
hopeless engineering path, even if we get a really good new material.

In the article, that graph of various materials' specific strength is a
little misleading.  Note the vertical axis is E/(rho)^2, which makes you
think it is better than everything.  I would argue it is about the same as
balsa wood in the parameter that really counts, but it isn't nearly as
strong as balsa wood by volume, so you need a lot more volume, which brings
it to a similar weight to a comparable balsa structure.  Of course, if we
have a new material which can be formed in any shape, and still have
balsa-ish mechanical properties, that would be cool.

If we can make this stuff in a 3D printer, that would be a huge
breakthrough.

They need to have Styrofoam somewhere on this chart.

Note that this chart shows aerographite a couple orders of magnitude less
dense than graphene aerogel, so if it had similar mechanical properties to
aerogel, it would be four orders of magnitude higher on this graph.  It is
showing about 2.5 orders, so I would expect it to be far more delicate than
aerogel.  Aerogel can be scratched with the corner of a piece of paper.

spike