"charlie" wrote in message
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"Ed Huntress" wrote in message
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"Larry Jaques" wrote in message
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On Wed, 19 Nov 2008 00:04:47 -0500, the infamous "Ed Huntress"
scrawled the following:


Oh, wait, I remember where you got the diamond thing. You're talking
about
cubic zirconia, which is a form that's clear crystal, used as artificial
gem
diamonds.

It still isn't diamond, man-made or otherwise. But you probably know
that.
The ceramic zirconia usually is white.

Right, and now black. The black ceramic knives are sinister looking.
Very cool.

Are you sure they're zirconia? Black is usually aluminum oxide. In
high-performance engineering applications, black may be silicon nitride.

I'll bet they're aluminum oxide (alumina).

--
Ed Huntress


--
Latin: It's not just for geniuses any more.

my aluminium oxide blasting medium is brown. my silicon carbide blasting
medium is black.

does al2o3 come in black too, and is it harder than brown al2o3?

It comes in black, but I don't know if it's harder. IIRC it's tougher. There
also is white AlOx, and pink.

The black, if my vague and fleabitten memory still works, contains small
amounts of some ferrous compound.

--
Ed Huntress