Re: Optimum particle size

"Dr. Mike" wrote:
>
> The particles are hard and inert such as SiC or diamond. I've already
> successfully rolled 1 mil foils with 2-3 micron particles but I want to
> put in larger particles. I know what you mean about theory and
> practice. There is a formula (rule of 7) for achieving maximum packing
> density of particles. It didn't work for me (but I reached well over 80
> vol.% without it) and I don't need it here fortunately.
>
> You especially should know that I will get better thermal conductivity
> with large diamonds than with smaller ones. I am also aware of the less
> than optimum bonding between aluminum and diamond. I hope to take care
> of that too.

Maximum packing for monodisperse identical particles is achieved for
M&Ms. Ultimate packing of a lattice of spheres requires two or three
sizes - the lattice itself, then filling its octahedral and/or
tetrahedral holes.

Wetting diamond with aluminum is an interesting problem, including
moisture-sensitive Al4C3 from graphite. Aluminum likes hard Lewis
bases. Perhaps a diamond dust surface treatment by oxygen corona
discharge or plasma ashing. The diamond surface is normally paved
with C-H. A little oxidation could be the needed tie-layer.

Metallization of diamond is SOP for heatsinks. Getting micronized
dust metallized without having more metallizaiton than diamond sounds
nasty.

--
Uncle Al
http://www.mazepath.com/uncleal/
(Toxic URL! Unsafe for children and most mammals)
http://www.mazepath.com/uncleal/qz.pdf
.

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