Re: [Sci.nanotech] Sound absorption properties of nanotube.


Yes sir:

The electrons are indeed sp2, my mistake.

I am very aware that air is a mixture of many gases.

I had always assumed the electrical conduction of graphite (and hence
carbon nanotubes) was the delocalize sp2 electrons that are free to
migrate in the presence of an electric field. I will certainly try to
better understand the electrical properties of graphite and nanotubes.

The cheapest aircraft we sell goes for 38 million, and a considerable
amount of that money goes for active and passive noise suppression. I
also believe the price on carbon nanotubes will greatly decrease when
the market demand goes up.

This was a simple question from a mechanical engineer working for an
aircraft manufacturer. I felt your answer was way too condescending for
my taste. Is it any wonder that the number of posts have fallen to
nearly zero on the sci.nanotech news group.

Thank you and good luck.



Perry E. Metzger wrote:
Steve Werner <steve.werner@xxxxxxx> writes:
Has anybody in this group considered using fluffy nanotubes (like
fiberglass insulation material) for a sound absorption material.

Presumably you mean carbon nanotubes, based on the rest of your
post.

It seems to me that the delocalized sp3 orbital electrons of the
nanotube would be capable of absorbing acoustic energy via an
inelastic collision with air molecules.

The carbon atoms in graphene or carbon nanotubes have sp2
hybridization, not sp3. I would have imagined that sp3 was a typo, but
you repeat it. On the other hand, neither electrons in sp2 nor sp3
orbitals are widely delocalized -- it would be the electrons in the pi
system (based on the p orbitals -- the sp2 hybrids form the sigma
orbital framework) that would be widely delocalized.

Presumably when you say "air molecules" you mean gas molecules in air
(air is not itself a pure substance).

Generally speaking, it is not a reasonable description of the
collision between an O2 or N2 molecule and a carbon nanotube as an
"inelastic collision" with "sp3 orbital electrons". I'm not even sure
what you would mean by this.

Much of the rest of your posting similarly isn't terribly clear and
contains malapropisms.

My particular interest is looking at a better sound insulation
material for business aircraft.

CNTs are currently dramatically more expensive than virtually any
other material one could consider using as sound insulation --
something like $20/gram I believe.

I would guess offhand that a quarter inch layer of the things outside
of the passenger compartment of an airplane would probably cost more
than the rest of the airplane. (That is only a guess -- I haven't done
the back of the envelope.)

Any thoughts about this?

I'd say that the sound absorption idea doesn't make much sense a priori.
I am not an expert on the sort of QM calculations one would need to do
to evaluate the idea, but I haven't seen anything in the literature
about this, and I suspect (based on the context of your message) that
you have done no new theoretical calculations or experiments to lead
you to this novel conclusion.


Perry


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