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Re: stainless conductivities



At 18:19 6/11/99 -0500, Tim Sullivan wrote:
...
The typical "resistance wire" we use in wire-wound resistors and in
heaters is nichrome wire. ... Nichrome is an alloy with
the approximate composition of 60% Ni, 25% Fe, and 15% Cr.
...
Michael D. Edmiston...

...
If we are saying that SS has an anomalously low conductivity, then we need to
say what the standard is. A deviation from the [Wiedemann-Franz] relation
might
be taken as evidence of anomalous transport. Here is some data taken from the
CRC:
.../abbreviated/

Substance: thermal electrical product
conductivity resistivity

(J/s-cm-K) (microohm-cm) [[uW.ohm/K]]

Titanium 0.17 80 14
...
SS 304 0.17 72 12
...
Copper 3.89 1.7 6.6
...
Solder 50-50 0.30 15 4.5
...
So stainless does seem to be on the extremes both of resistivity and the
[Wiedemann-Franz] ratio, though it isn't exactly alone. Interesting that it
shares the extreme with (commercial) titanium, since one usually thinks of
alloys as having the higher resistance.

Tim Sullivan
sullivan@kenyon.edu


I enjoyed this exchange.
Spooked by talk of the complexity of the phonon/electron
mechanisms for conductivity, I took a look at a sample of recent
science reportage of work in this general area,
from IOP London. Here's the URL:

http://www.ioppublishing.com/PEL/article/cm08003l1/full/

I concluded it was a product not totally out of reach
of the well-disposed.

brian whatcott <inet@intellisys.net>
Altus OK