Transparent Aluminum?

I'll go further and say, like just about everything we use in our lives. Despite the chorus of "War, what is it good for?" from all the blathering "peaceniks", human conflict (or conflict avoidance through superior military strength) has driven virtually every significant technological advance since the dawn of civilization through today. Mind you, I'm not advocating warmongering for the sake of driving innovation. I'm just reporting the facts (before the social revisionists rewrite human history).

Also known as corundum. This is the stuff sapphires and rubies are made of (with different impurities creating the different colors). In fact, there are watch makers that use corundum crystals for their watches (usually marketed as "synthetic sapphire" crystals).

Isn't Aluminum oxide Sapphire? Don't know what percentage of nitrogen they are talking about, but if I remember right pure Sapphire (straight aluminum and oxygen) are transparent- color is due to various impurities. I know sapphire is used for infrared lenses and windows. I see no reason similar materials cannot be used for lenses, but one must check the dispersion charactoristics to see if result would give too much chromatic aberration.

I can remember many technologies where the lag has been in the other direction. Sometimes getting a new material or new electronic technology through the mil spec certification means that military applications lag civil ones. Transistor is a good example.

Same with ICs. While I did not work directly on the VHSIC program, others in my group did, and it was funny to see commercial ICs come out that were better, more transistors, and fast before the results of the VHSIC program ever made it to production.

There were, and still are, commercial values for high tech electronics. I also remember seeing carbon fiber make it to commercial uses before it was used in production military aircraft.

On Wed, 19 Oct 2005 12:55:36 -0700, BillP wrote: Snip

Would an ultrasonic cleaning bath be any good ? I use mine for cleaning crap off models and will have to try it on reading glasses as I now have to use them since my cararact operation. Alan in beautiful Golden Bay, Western Oz, South 32.25.42, East 115.45.44 GMT+8 VK6 YAB ICQ 6581610 to reply, change oz to au in address

Corundum is natural crystalline aluminum oxide, Carborundum is a tradename for manmade silicon carbide.

Ned Simmons

Alan! Yes, the ultrasonic cleaning does a goog job at home in the wife's jewelry cleaner, I haven't the luxury in the field.... several times per day!.... Thx!! Bill

snipped-for-privacy@i> Snip

It depends a lot on how big the civilian market is and actual production cost. I think transistors were being used in consumer portable radios while the Army still was using tubes in walkie talkies. Kevlar was used in tires long before NASA would use it. No mil spec.

Dan

D> >

there's a very lightweight metal that mine are made of that are bendable. some sort of titanium alloy i think they told me. they're the lightest i've ever had, stay in adjustment (as i have NEVER had to have them realigned, unlike my previous sets of glasses), and i can twist them into a knot and they bend, but spring back to shape. costs more, of course, but after a few head plants skiing, they pay for themselves.

regards, charlie

And we of course cannot leave out the spin offs in medical. Not just the toys, but the basic treatments.

Gunner

"Pax Americana is a philosophy. Hardly an empire. Making sure other people play nice and dont kill each other (and us) off in job lots is hardly empire building, particularly when you give them self determination under "play nice" rules.

Think of it as having your older brother knock the shit out of you for torturing the cat." Gunner

SHAME ON YOU!!!

And just WHERE do you think THIS guy got the idea?

Ahhh... OK. There lies my confusion. I knew with certainty that both are used for abrasives, at least :)

Corundum -- Al2O3 Hematite Group - Sapphire is a color type gem that isn't red

- ruby is red. Other colors are sapphire - blue( star), black (star), yellow, .... also known as corundum, magnetite, hematite, and spinel.

That is first year Mineralogy class. Useful when trading stones...

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>

Scottie is the chief engineer. Scottie has nuclear and other 'fancy' stuff with windows in it. But he was on a Klingon ship - and knew what he needed, just no shop to make it for him. After all - the Star class Cruzer - has most everything or can make it.

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

Tom Gardner wrote:

I'll buy that one, as I already know it's correct.

But not these two, which I know in both cases to be forms of iron, not aluminum. Magnetite, in particular, is definitely ferrous - Under the name of Lodestone, in association with a piece of string to hang it from, or a cork and a bowl of water to float it with/on, it was humanity's first compass needle. Except when used as a coil winding, I've never heard of any form of aluminum exhibiting magnetic properties... As for Hematite, I've heard it described, by several different persons in positions to know, as "crystalized rust" because it's essentially a lump of iron oxides with a handful of impurities.

Eh... Might be, but not sure, and not interested enough to find out.

Perhaps being classed in the "Hematite group" indicates they all have similar crystal structures? They definitely don't have the same molecular structures!

Mayhap someone needs to attend it... :)

Nitinol -- nickel titanium alloy, the so-called shape memory alloy. I've got some in my mouth (orthodontics), as a matter of fact.

Through interesting bits of phase change (that I suppose I should read up on), it defies ordinary elastic theory! As an added bonus, I bet you can put your glasses either in the freezer or under dry ice and, for a few moments, bend the hell out of them. Then as they warm up, they spring right back into place! ;-)

Tim

-- Deep Fryer: a very philosophical monk. Website:

These things were listed rather ambiguously, but I know what was meant: Hematite, corundum, chromium oxide and I think a number of rare earth oxides, all take the same crystal structure, and have similar atomic dimensions so are somewhat replacable by each other.

...

The other interesting aspect of the above-mentioned trio is they form a nice stable crystal structure with divalent metals, known as the spinel structure. The divalent metals include (let's see if I can get them all from memory): magnesium, manganese, iron, nickel, zinc, and in a related vein, lead. (Note that iron appears in both lists because it is di- and tri-valent!) Thus, what you get are 15 combinations of these elements, known as spinels, of the form XO.Y2O3 = XY2O4. For example, the namesake mineral spinel is magnesium aluminate, MgAl2O4. Chromite, the chromium ore, is ferrous chromite (not chromate), FeCr2O4.

A consequence of the dual behavior of iron is magnetite, FeO.Fe2O3 = FeFe2O4 = Fe3O4. Magnetite is very stable: at high temperatures, it can be reduced to ferrous oxide (FeO), but between 300 and 560°C, FeO disproportionates to iron (metal) and magnetite! Likewise, it can be oxidized (most easily by weathering at low temperature), but Fe2O3 actually decomposes into Fe3O4 with a release of oxygen at 1451°C. Magnetite also has a higher melting point than FeO, slightly higher than the melting point of steel (though you can't observe this directly because any oxide attached to that melting piece of steel will be reduced by the metal, causing the slag to literally drip off the iron, which looks very interesting).

Industrially, chromite refractories such as MgCr2O4, FeCr2O4 and MgAl2O4 are often used to buffer between cheap, acidic, silica-rich firebricks and more expensive, basic dolomite and magnesia bricks. The basic bricks are used because, in addition to being highly refractory (MP > 2400°C), they absorb sulfur and phosphorous from the steel contained within. These basic refractories gave rise to the terms "basic oxygen process" and "basic open hearth process", neither of which are mechanically "basic". ;)

That's because they aren't in molecules, they're in crystals. ;o)

Tim

-- Deep Fryer: a very philosophical monk. Website: