The reason for the confusing name is apparently that the the guy who first synthesized SiC thought at first that he had created a compound of alumina and carbon. He combined the words carbon and corundum to get Carborundum.
I know you are familar with Alnico, an aluminum alloy. It is so different from most aluminum alloys that I usually forget it too.
Dan
D> I've never heard of any form of aluminum exhibiting magnetic
Sorry to say - I'll plagiarize and show you a bit closer to the facts.
In Oxides and Hydroxides Hematite Group Corundum- Al2O3 Name: Probably derived from the Sanskrit, Kuruvinda, "ruby"; korundum. Varieties: A very impure material, known as emery, is an intimate mixture of granular corundum, magnetite, hematite and spinel.
So Emery is a variety of Corundum and happens to be the only entry in the book in this reference.
Spinel is MgAL2o4 it has a touch of Magnesium and another oxygen. Can be man made easily. (and is in another group - the Spinel Group.)
Ruby add chromium for some of the Al. Not all. Sometimes the lesser ruby is Fe or Ti or now FeTio3 all together.
Hematite is Fe2O3 Ilmenite is FeTiO3 Geikielite - MgTiO3 Pyophanite - MnTiO3
So as chemical elements - there are not exacts for this or that. Gemstones are mixtures of alloys... And the names are the confusing issue. Different chemical content for the same name simply due to local use, greed, or custom.....
What I slipped up on is truncating to much stuff and left off the 'emery'.
Martin
Martin Eastburn @ home at Lions' Lair with our computer lionslair at consolidated dot net NRA LOH, NRA Life NRA Second Amendment Task Force Charter Founder
D> >
Yes! You know what else destroys lenses in a hurry? A "helpful" child with a muddy shirt wanting to clean my glasses for me while I'm taking a nap. I might as well just pop my left lens out right now. I'm about a hair from going to the glasses place with a set of chipping goggles and saying, "I want prescription GLASS lenses to fit these!" I'd look like a freak, but I'd be able to see. Straight ahead, anyway. (: BTW: there's a really expensive watch out on the market with a case made of this stuff. In fact googling gets me:
My last (recent ) set of glasses with glass lenses are very abrasion sensitive. The lenses are uncoated. Has the lens glass been getting softer to make the manufacturing easier? It really bugs me that my old glasses were about ten times more scratch resistant than the new ones.
(snip)
I wonder if the 'legend' of transparent aluminum is an outgrowth of the use of an aluminum film for use in astronomical mrrors. The film develops a hard oxide coating that is transparent and durable.
It isn't as reflective as silver but has a much longer lifetime because it doesn't tarnish. It was a very important development in telescope technology.
Soames
Don Bruder wrote On 10/19/05 09:42,:
A PS, I used to demand glass lenses instead of plastic for that reason, glass is much less prone to scratching than plastic. I finally switched because, well, I am slowly going blind and the damm things weighed a ton.
What I discovered, that helped tremendously, is the method I and others used to clean their glasses was the problem. Most folks whip out a soft cloth to clean them, which is exactly what causes the scratches. You are basically grinding the lenses with small dust particles embedded into the cloth.
I switched to always cleaning them by washing them first with soap and water. The soap removes any grease that is holding the dust in place.
Think of it this way. Unless you are grinding with a shower of particles in your face, you're not getting the scratches while you are working. Anything strong enough to scratch even plastic, you would feel if it hit you in the face.
Actually, In the middle 70's Sandia had developed exactly transparent aluminum in sorts. They could flip a switch and you could see through a sheet of material. Flip it in reverse and it would be opaque. They later were able to market it as high tech windows.
Martin - been in there and aided in other projects as a local expert available to them.
Martin Eastburn @ home at Lions' Lair with our computer lionslair at consolidated dot net NRA LOH, NRA Life NRA Second Amendment Task Force Charter Founder
Hemlock Soames wrote:
PolyTech Forum website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.