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To: FatherTorque
Oops. Bad Fish Causes Gurgling.

Bad News: I jumped to some erroneous conclusions, and my mailbox exploded. Transparent Aluminium doesn't exist.

Good News: This indicates many polite, educated people are actually reading the site, as none of the mail called me an idiot and about 80% of it was thoroughly educational.

Point of contention: The article states the substance in question is alumina, which I presumed was simply a German spelling of aluminum (despite being closer to a latin-based spelling)...partially spurred on by the caption to the picture in the original article actually saying "transparent aluminum." My science background not being in chemistry, I completely missed that alumina is shorthand for aluminium oxide... a ceramic, which is why it makes more sense for a company specializing in ceramics to have developed a transparent version of it.

Now, this doesn't make it any less impressive, because they've apparently managed to not only make it transparent, but seriously overcome the hardness (which usually also means brittleness) factor of alumina, if the firing tests are to be assumed to have been the German Federal Armed Forces shooting at them (especially if the US military has expressed an intrest in using it for visors or tank windows), rather than kiln firing tests performed by German Federal Dishwasher Assoc.

One other basic distinction in the field that my love of synonyms burned me on:

Hardness does not equal toughness. Metal is tough, as it will give before it breaks. Hardness, on the other hand, is resistance to deformation. A chicken bone is hard (and brittle). Soak that bone in vinegar, and the hardness goes down, the toughness goes up...it bends.

It was also pointed out that true transparent aluminum...a metal, would be isotropic (strong in every direction, allowing it to bend), whereas this would be anisotropic (only strong in certain directions...in this case, presumably able to react well to bullets, but a toric twist could shatter it).

Lastly, a few readers pointed out that your average dinnerware is fired to 1305 C, so the 1200 C used to fire this material isn't the trick to it, it's gotta be the "in such a way" bit mentioned in the article that is the secret...maybe it's an ancient chinese secret.

Oh, and I was also corrected on the pronunciation of aluminum...it's 'al-you-min-ee-um'. My ironic sense of humour is taking great pride in having been corrected in the pronunciation of something I wrote. ; )

LMAOROTF

55 posted on 05/01/2002 7:15:21 PM PDT by ATOMIC_PUNK
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To: ATOMIC_PUNK
Transparent alumina (corundum, var. sapphire) has been around for years and years -- better quality watch crystals are made from it. I went to the site LarryLied provided in #47 above and am more confused than ever. All I can deduce is that they have developed a means of bonding smaller segments of the material together and have developed better methods of fabricating new shapes and polishing. The hardness vs. toughness aspect has me puzzled and it isn't explained as far as I can tell. As a ceramic, synthetic corundum shatters easily even though its hardness is 9 on Mohs' scale, next to diamond (even though diamond is about 40 times as hard as corundum!) The article doesn't mention what kind of material is used to bond the smaller segments, nor does it explain how it has been changed to have the toughness for the things they plan to use it for. Maybe we missed something in the translation?
66 posted on 05/01/2002 7:52:14 PM PDT by Bernard Marx
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