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Re: Beryllium Oxide



Original poster: David Speck <dave@xxxxxxxxxxxxxxxx>

I would concur with the vacuum feedthrough identification for the insulators.
I have several like these, and when properly identified, they usually go for big bucks on eBay ($150+ each). The advantage of using Be02 is that the high thermal conductivity helps minimize thermal expansion effects.

If you want to keep a high vacuum intact, having your insulators move when they get hot is likely to cause leaks. In many semiconductor processing apps, the vacuum chambers can have big temperature differentials between the inside and outside, and the situation is complicated further if you are running heavy currents for vapor deposition filaments through the centers of the insulators. The better the heat conduction through the insulator, the less thermal expansion you are likely to have to deal with. I would expect that they are pretty much pure BeO2, except for a little binder. They are pretty much inert when intact. It was the best material available around the time of WWII, before modern plastics like Teflon and Delrin came into common use. Interesting correlation -- the best best thermal conductors are usually the best electrical conductors. Exceptions exist -- Al2O3 is used in the typical white computer heatsink grease. Chemically inert, decent heat conductor, but good insulator. Diamond is also a good heat conductor, though a good insulator.
HTH,
Dave

Tesla list wrote:
Original poster: Bert Hickman <bert.hickman@xxxxxxxxxx>

Hi Godfrey,

These sound very much like vacuum feedthrough insulators.