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Transparent Aluminium
Lynx writes "As the german magazine Spiegel reports, scientists at the Fraunhofer Institute for Ceramic Technologies have developed a transparent tile made from aluminium oxide pellets baked at 1200C. The material is very hard, and could be used as bulletproof windows." Use the fish.
Yeah. Star Trek IV: The Voyage Home. "How do we know he didn't invent the bloody thing." Looks like it only took the guy 18 years to figure out the "dynamics" of it. Now all we need is dilithium crystals, isolinear chips, and fusion reactors.
Sorry. I should have read the blurb more carefully.
This isn't transparent aluminum; this is a transparent aluminum oxide. That is just not the same thing as aluminum anymore then water is Hydrogen gas, or table salt is the same thing as Sodium metal or Chlorine gas (both very harmful chemicals, sodium can explode when it comes in contact with water, and Chlorine can kill you in a few breaths, yet we eat salt all the time)
And secondly we have known about aluminum based compounds for a long time, in fact, longer then we have known about Aluminum or even about elements in general. Alum, the compound from which aluminum gets it's name (and which we extract aluminum from) has been known to man for ages and is, in fact, transparent.
autopr0n is like, down and stuff.
Btw, The artical indicates that this material is 3 times as strong as steal, making it far stronger then pure, regular, opaque, Aluminum metal.
autopr0n is like, down and stuff.
> this material is 3 times as strong as steal,
No, it says it is three times as _hard_ as hardened steel, which isn't the same thing (though they are related). Considering that corundum (i.e. ruby, sapphire) is made of aluminium oxide, that isn't that surprising.
Forming that hard material into tiles of unspecified but obviously reasonable toughness and strenth while keeping it transparent is the impressive bit.
rant
let out a giant yawn.
Alumina being transparent or strong is hardly new. Although the bullet proof glass thing is pretty funny. Alumina is not tough, it may be strong, and even greatly stronger than steel should we be talking about specific strength, but it is not tough at all. And I don't know about you, but the last thing I was between me and a bullet is a sheet of something that will shatter with countless sharp edges to cut me to ribbons.
I'm sure there are a great many chemical concerns that would be thrilled to tell you all about their alumina powders should you care to ask. But trust me, until we can do with alumina what clams can do with chalk the most interesting thing one is likely to do with alumina is make a crucible.
--Jimmy has fancy plans; and pants to match.
as Babelfish & Co are not really up to it yet, here's my human-made translation of the German article. I'm a German native speaker, but I can't guarantee the English spelling, so take with a grain of salt ;-).
Things in [brackets] are my remarks.
- - - -
Der Spiegel [leading German magazine, a la Times or Newsweek]
February 19, 2002
TRANSPARENT
Armour-like tile protects from projectiles
Researchers in Dresden [German city] have developed transparent and extremely hard tiles. The Pentagon, among others, is fascinated by this material, which can be used to produce e.g. bullet-proof visors.
[PICTURE] picture caption: "transparent Aluminium tile"
America's weapon technicians show interest for an armour-like tile from Dresden. At the "Fraunhofer-Institut für Keramische Technologien" [Fraunhofer institute for ceramics technologies] there, fine-grained aluminium oxide was successfully baked in an oven at 1200 C to produce an extremely hard, transparent material.
A plate sized 10x10 cm (thickness: 1 cm) only weighs about 400 g, but is three times as hard as hardened [tempered?] steel. During shooting trials on behalf of the "Bundeswehrbeschaffungsamt" [federal procurement office] in Koblenz, "outstanding results" were achieved, according to the researcher Andreas Krell.
The tiles are also being examined in the US state of Idaho: The Pentagon is fascinated by the transparency of the material, which can be used to build bullet-proof visors or big windows for armoured personnel carriers [Panzerspähwagen?].
This is very cool... however it's no more exciting than micrograin metals or some of the amazing things they can now do with micrograin titania.
Micrograin copper for instance conducts like gold, and is nearly as hard as steel (while being much lighter... this is wonderful stuff.)
Micrograin titania, another ceramic, is transparent, significantly harder than steel, as flexible as plastic, lighter than aluminum, and can smile at temperatures that would turn most metals into soup. Some folks who are working diligently on electrolytic extraction for titanium (the process that brought the price of aluminum down, from more precious than gold), believe that micrograin titania could one day make the perfect engine (since it can be cast and sintered directly into useable parts.)
Face it kidlings, the steady march of material science is giving us an incredible boon of new and amazing new stuff to play with... pretty much like the rest of technology knocking on our collective doors. I want to be the first on my block with a Moller Skycar with the transparent titania upgrades.
Moller Skycar; http://www.moller.com/skycar/
Genda B -- I detest Osama bin Laden, a man who is the bigoted, violent, religiously fanatical, spoiled son of a rich oil magnate, who believes he can control the world with the threat of war and destruction. Hey, wait that sounds like somebody else...
"It would be more like a ban on covalent bonds between carbon and chlorine, which rarely if ever occur in nature and are stable enough to persist for centuries."
Not really true -- halocarbons are actually more common in nature than you think. A number of organisms such as certain fungi and marine algae produce halocarbons containing chlorine, bromine, and iodine. These compounds can range from simple Methyl-type compounds to polycyclic aromatics.
They can also be formed when wood decays in the presence of halogen salts. The lignin portion of wood is basically a polymer of aromatic alcohols, and under the right conditions halogen ions can react to form aromatic halocarbons.
Hardness increases with toughness not necessarily vis versa.
Think of it roughly in these terms:
A hardness contest between two materials consists of trying to scratch one with the other. The one scratched is harder.
A toughness contest between two materials consists of trying to break one material with the other. The one broken wins.
Seastead this.
Metals made transparent by photonic layer structure:
http://eetimes.com/story/OEG19991108S0095
This is much more useful than transparent armor,
IMHO, if it can indeed be applied to photonic
band-gap filtering...
Strength - A property of materials under elastic deformation, meaning the degree to which the material bends under load, and then springs back to its original shape. At sufficiently high loading, the material deforms plastically, meaning it stays bent. Strong materials deflect very little under load (low strain per unit stress), and can take high loads before plastic deformation occurs.
Toughness - A property of materials that contain microcracks or other fracture-inducing characteristics. Such flaws cause localized increases in stress levels and thereby cause fractures to expand until the material fails catastrophically. This is the mechanism underlying stress-corrosion cracking and fretting fatigue. Tough materials do not have high localizes stress at crack tips, and can tolerate microcracks without catastrophic propagation and failure.
Hardness - The strength of a material at its surface. Measured empircally by poking it with sharp objects. Hard materials resist scratches and dents. But whether they deform (elastically or plastically) has nothing to do with their hardness. It has to do we their bulk strength.
This research facility focuses on ceramic-related activity. Given that I am by profession very familiar with the process involved in the manufacture of such materials, I can venture an interesting guess.
Porcelain and ceramic tiles get their strength from 2 processes: exposure to pressure from a vertical hydraulic press, and subsequent firing (baking) of the tile.
1200 degrees is not very far off the temperatures at which the firing curves for commercial mass produced porcelain lie.
I thus assume that the difference lies in the pressure at which the pellets are pressed. It's got to be a LOT higher than the pressures used in the commercial porcelain/ceramic manufacture environ.
And anything will become harder when you compact it. Look at how diamonds are formed.
So essentially, what we are saying here is " Hey, we took some transparent stuff, compacted it really tight then fired it, and whee, we got ourselves a slab of very hard transparent stuff"...
Where's the innovation?
Blearf. Blearf, I say.
"harder" should, of course, have been "less hard".
Seastead this.