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


Bob wrote:
On Thu, 20 Sep 2007 00:01:46 -0000, "Perry E. Metzger"
<perry@xxxxxxxxxxxx> 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.

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.

generally agree with all that.

Wouldn't the "theory" -- such as it is -- be equally applicable to
graphite, say a powder or foam?

An experiment would help? Easy enough with graphite. Maybe even with
CNT if you insist; after all, it would be a non-destructive test.

bob


Bob,

I have read a number of places that multi-walled carbon nanotubes are
excellent conductors of heat and electricity. My understanding is the
excellent heat conduction is a result of ballistic conduction of the
electrons (http://en.wikipedia.org/wiki/Ballistic_conduction) down the
carbon nanotube.

We currently use a fiber-based material to provide some cabin sound
attenuation for the aircraft, but the sound insulation material really
just disperses the sound without really absorbing much of the energy
from the sound wave. The molecular collision between the gaseous
molecules and a solid material are going to be elastic collisions with
very little net exchange of energy if both are at the same temperature.

My "Thought" experiment was to look for a solid material where the
molecular collisions between the gas and the solid would transfer a
substantial amount of the kinetic energy from the gas molecule collision
to a ballistic conduction wave in the solid sound absorption material.
I thought perhaps a multi-walled carbon nanotube would be an appropriate
material. The graphite does not appear to have this same ballistic
conduction property as a multi-walled carbon nanotube so I still think
the carbon nanotube has some possibilities.

I certainly appreciate your reply to my question, and you certainly do
not need to reply to this post since I will no longer be reading or
posting on the sci.nanotech news group.







.

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