Re: Questions for Uncle Al

From: Uncle Al (UncleAl0_at_hate.spam.net)
Date: 11/09/04 

Date: Tue, 09 Nov 2004 12:15:27 -0800

Dirk Bruere at Neopax wrote:
>
> Uncle Al wrote:
>
> > Ragnarok wrote:
> >
> >>My plan was: sealed electrical oven, argon atmosphere, graphite
> >>(electro-carbon, actually) crucible with lots of amps going through
> >>it, making it both the crucible and the heating element. We have a
> >>research institute here doing that kind of stuff. I thought of
> >>tungsten crucibles in inert atm, but it's too hard to get my hands on
> >>one of those.
> >> Anyway, from what I've heard, the charcoal/tar mixture pressed in
> >>the desired shape and heated for several hrs in an inert atm will do
> >>the job.
> >
> >
> > You can buy densified graphite esily enough. Most of it fabricated is
> > heinously overpriced, so shop around. We know it is compatible with
> > alumina given the Hall process and dies for edge-defined growth.
> > Growing ruby is slow work. You must allow for flux loss by
> > vaporization to progressively bring it out of solution. If you are
> > hoping for directional solidification of molten alumina, you'd better
> > look up the necessary temps and techniques.
> >
> > Czochralski Cr-doped alumina grows laser rod raw material. Ruby laser
> > rod is very pale pink - definitely not gemstone. However, give it a
> > megrad of Co-60 gamma sterilization and you get the most remarkable
> > padparadsha color. It's a stunner! (Plain alumina gives you yellow.)
> > It's also thermally unstable over 100 C. Facet then sterilize.
>
> Is it used as a gemstone in that form?

I did it as a lark while at Optical Radiation Corp. We were
gamma-sterilizing stuff anyway. Whether it is commercially viable
depends on whether it is sufficiently stable to ambient temperature
and light. It was an eye-popping color. 

-- 
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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