Follow Slashdot blog updates by subscribing to our blog RSS feed


Forgot your password?
Science Technology

Transparent Aluminium 368

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.
This discussion has been archived. No new comments can be posted.

Transparent Aluminium

Comments Filter:
  • by ender81b ( 520454 ) <billd@inebra s k a .com> on Wednesday February 20, 2002 @04:03AM (#3036877) Homepage Journal
    Ha! That guy finally figured out those equations Scotty gave to him back in Star Trek IV! Another technological breakthough thanks to good 'ol Scotty.
  • by ARColeslaw ( 66892 ) on Wednesday February 20, 2002 @04:05AM (#3036881)
    ...with some transparent concrete [] to build a transparent house! Now people who want to live in a "glass" house don't have to worry about throwing things at each other! Oh, but they still have to worry about being naked...
    • Oh, but they still have to worry about being naked...

      hehe, who cares... Clothes have not been invented to hide the body, but to keep warm.

      The concept of hiding the body comes from the moral ineptness of some idiotic religious nuts during the dark ages

      • The concept of hiding the body comes from the moral ineptness of some idiotic religious nuts during the dark ages

        Genesis 4:6-7

        "And when the woman saw that the tree was good for food, and that it was pleasant to the eyes, and a tree to be desired to make one wise, she took of the fruit thereof, and did eat, and gave also unto her husband with her; and he did eat.
        And the eyes of them both were opened, and they knew that they were naked; and they sewed fig leaves and made themselves aprons"

        You don't have to accept this account as history to realize that at the very least, semitic societies had some sort of concept of hiding the body thousands of years back. Copies of Genesis predate the idiotic religious nuts of the dark ages by at least 2 millenia. There have probably been societies that felt it was good to hide the body from view for as long.

        Not to mention covering the body for purposes other than warmth OR morality: protection from sun or sand or other dangerous substances, check against physical blows, adornment and status, disguise. Or for that matter, enticement -- if nakedness were the ultimate turn-on, Victoria's Secret wouldn't do such good business. I'm sure Victoria wasn't the first one to catch on.

        Anyway, I'm overesponding, but the point is, there are lots of reasons for cloths, and most all of them are probably older than western society.

        • Nonsense! Everybody knows that the nudity taboo was invented by Gapchaneloren IX in 1000 BC in order to help out the garmet industry!
        • Your argument is to quote from Genesis. Amazing! You may have shown the date was wrong but you've done nothing to show that shame from nakedness wasn't invented by religious nuts.
          • Your argument is to quote from Genesis. Amazing! You may have shown the date was wrong but you've done nothing to show that shame from nakedness wasn't invented by religious nuts.

            You know, I've actually been WAITING for someone to make a stupid comment like this.

            MY comment was meant to refute two ideas contained in the parent post:

            1) clothing was adopted solely because of "moral" concerns
            2) this was done in the middle ages

            I'd say my comment did both conclusively. #2 first and foremost -- unhealth attitudes about the human body may have been reperpetrated and reinforced then, but the use of clothing as a "moral shield" most certainly didn't first come about then.

            #1 wasn't demonstrated conclusively -- how do I KNOW people came up with clothes for reasons like protection and ceremony and adornment and disguise? I don't. I just know people use it for that today, across nearly every society. It stands to reason that people adopted clothing for a variety of reasons a long time ago.

            So my post did exactly what it claimed to do. Yours is a Red Herring.

            Now if you WANT to address issues about whether all shame from nakedness is due to religious influences, and whether religious people are nuts, specifically, those who wrote Genesis, that'd be a whole 'nother post....
  • Wait.... (Score:5, Informative)

    by autopr0n ( 534291 ) on Wednesday February 20, 2002 @04:06AM (#3036882) Homepage Journal
    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.
    • The first sentance of the second paragraph should read: "And secondly we have known about aluminum based transparent compounds for a long time"
    • Followup (Score:4, Informative)

      by autopr0n ( 534291 ) on Wednesday February 20, 2002 @04:22AM (#3036931) Homepage Journal
      Btw, The artical [] indicates that this material is 3 times as strong as steal, making it far stronger then pure, regular, opaque, Aluminum metal.
      • by armb ( 5151 ) on Wednesday February 20, 2002 @04:50AM (#3036998) Homepage
        > 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.
        • This would be useful for windows of buses and trains in areas where they tend to get vandalized.
        • by armb ( 5151 ) on Wednesday February 20, 2002 @05:08AM (#3037029) Homepage
          P.S. Considering the number of people who are confused about the difference between silicon and silicone, it's not surprising some can't tell the difference between aluminium and alumina (aluminium oxide).

          (Aluminum/aluminium is just US/international spelling. Looking at the original German article it uses "Aluminiumoxid" where the fish translation has alumina.)
          • There was a comment posted awhile ago on another article that stated that the original name of the element was 'Aluminum', but in England they felt it should follow most of the other elements and end in ium, so they changed it to allow a 2nd spelling, 'Aluminium'.

            So, that would make those of us in the US at least spelling it the original way =]

            • > the original name of the element was 'Aluminum', but in England they felt it should follow most of the other elements and end in ium, so they changed it to allow a 2nd spelling

              In English "aluminium" isn't just an allowable second spelling, it is the standard spelling. It's also the internationally agreed IUPAC spelling. (And yes "aluminum" was used before "aluminium". Full history at ments/aluminium/history.html).
      • Re:Followup (Score:5, Informative)

        by Hal-9001 ( 43188 ) on Wednesday February 20, 2002 @04:55AM (#3037009) Homepage Journal
        This material is nothing new: I covered the distinction between alumina and aluminum in this comment [] attached to the transparent concrete [] article that speculated about transparent aluminum. Bottom line is that alumina (Al2O3) and aluminum (Al) are totally different materials, so naturally they have different properties such as hardness, stiffness, transparency, etc. Alumina is what sapphires and rubies are made of. Pure alumina is clear, but the addition of color centers like chromium ions results in the color of gemstone rubies and sapphires. A search for sapphire conformal optics [] will show you that making windows out of sapphire for military applications is nothing new. Just about the only thing that might be new is how they make the sapphire, but the article does not provide any details about that. Yes, sapphire is cool stuff, but it's not some magical new material.
      • by Kibo ( 256105 ) <naw#gmail,com> on Wednesday February 20, 2002 @06:36AM (#3037141) Homepage
        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.
        • 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. It's fabricated from a powder, and isn't likely to be completely solid. There are going to be a large number of gaps between what used to be the powder particles. Any crack that starts in this material is going to go from gap to gap - following the path of least resistance. The most likely thing that will happen if this material is hit by a bullet is that a small chip will break off. A crack won't be able to make it to the far side of a thick piece of material - it will hit an air gap instead, and a new crack will have to start on the far side of that gap. Hit it hard enough and that will happen, but it will be more difficult to crack through completely than a completely solid piece of alumina. You end up with a material that isn't particularly tough, but it breaks the way you want it to.

          If the material is close to 100% of solid density, then you can put a polymer between a couple of layers of it, just like safety glass. One reason this is big news is that alumina is cheap and available by the tonne. Then again, so is silica.

          • For a ceramic, Alumina is pretty tough, but that's like saying for a 5th grader Todd Peterman is pretty tough. It takes very little to propigate cracks through ceramics. There some stuff that can be done, but ceramics aren't metal. And alumina has always been transparent.

            Now this MIGHT be news if they some how got their alumina powders on a nano scale where the alumina crystal grains are smaller than the wavelengths of light, then you'll actually get a relatively tough, and see through material. Not be cause something magical happens on that scale, but because the crack length will be huge, and actually require the formation of a large surface which would take a lot of energy despite the low toughness of the alumina. That would be news. BIG news. At least to me. But that's not what they said.

            They said they made a 10cm alumina tile. Big whoop.

            They might be able to enhance it by making it like corning wear, but that summery of a press release was clearly too light to provide that kind of detail. Which might have been interesting, although not news.

            I would bet that it being transparent means they either used a spectacularly fine powder, or it is basically fully dense as there doesn't appear to be many internal surfaces to scatter light (ie it's not opaque).

            Further more, I would bet that the flaw(s) introduced by the bullet would not be what caused it to fail, I would bet that pre-existing flaws near the bullets point of impact would be vastly expanded. Worse yet, the alumina tile might even bounce the bullet off instead of just stop it.

            Maybe the news is the simplicity and low cost? Too bad that didn't make it into the news then.

            Either way it sounds like it's nothing but a press release for a non-large company that's really happy that they might picked up as a contractor for the Department of Defence.

            Yawn. Already, we've given it more consideration that it deserves.
    • Re:Wait.... (Score:5, Informative)

      by jolyonr ( 560227 ) on Wednesday February 20, 2002 @04:25AM (#3036938) Homepage
      Transparent aluminium oxide has been known for a very long time, naturally it's known as Corundum [], and red varieties are called Ruby and other colours (not just blue) are called Sapphires.

      And artificial transparent rubies and sapphires have been made for around 100 years - so apart from maybe a new fabrication process there isn't really anything new in this story!


      ps. Alum isn't used as an ore of aluminium - there isn't enough of it found naturally, the ore of aluminium is Bauxite [], a mixture of aluminium oxides and hydroxides.
      • Since we're on a roll, we also want to break it to everyone that Santa Claus isn't real either.
  • The fish, eh? (Score:2, Informative)

    by Anonymous Coward
    Doing this anonymously as it'll likely be modded as offtopic, but the link provided to "the fish" accidentally labels altavista as .net.

    You would find the fish correctly at:
  • Yes, but... (Score:5, Funny)

    by Edgewize ( 262271 ) on Wednesday February 20, 2002 @04:11AM (#3036901)
    Remember, we are talking about the Fraunhofer research conglomerate. This material may an excellent bullet-proof shield, but you will have to pay license fees every time you stand behind it. And any attempts to duplicate the properties of this material will result in swift legal action.
  • Babelfish on a keyboard? How quaint. We prefer to use the Universal Translator.

    Besides, everybody knows Transparent Aluminum was invented by a Dr. Nichols, plant manager at Plexicorp, sometime in the late 20th Century. Using a Mac Plus [], no less! :)
  • When you can directly supply the link via google [] ?
  • by Kaiwen ( 123401 ) on Wednesday February 20, 2002 @04:14AM (#3036914) Journal

    Since both the Institute and Babelfish seem to be slashdotted, here the Babelfish output for those of you who can't get to it:

    TRANSPARENT Tank page frame protects against projectiles

    Dresdner researchers developed transparent and extremely hard page frames. By the material, from which visors can firing fixed be manufactured, also the pentagon is fascinated.

    DPA transparent aluminum tile America weapon technician show interest in a tank page frame from Dresden. In the there institute for Fraunhofer for ceramic technologies succeeded in baking fine-grained alumina in such a way with 1200 degrees Celsius in the furnace that an extremely hard, transparent material develops. A 10 times 10 centimeters large disk (strength: only about 400 gram weigh, are however three times harder 1.0 cm as hardened steel. With firing tests under contract of the German Federal Armed Forces from the Bundeswehr in Koblenz " outstanding results " were obtained, report the researcher Andreas Krell. Also in the US state Idaho were examined the tiles: The pentagon is fascinated of the transparency of the material, with which firingfixed of visors or large windows of armored reconnaissance vehicles can be built.

  • Geez...slashdot editors and their chronic error-making. The correct link to the fish is here [] .
  • by Anonymous Coward on Wednesday February 20, 2002 @04:44AM (#3036986)
    Fusion of aluminum oxide is not a new development of any type. More commonly known as Ruby or Sapphire (when dopants are present), the production of high purity fused alumimun oxide has been around for over 100 years. The window on my lab furnace is made from this same material. Do you have a highschool class ring with a ruby or sapphire in it? Well guess what, you too have a sample of this material right there on your finger. Even the fact that these guys are doing the fusion at relatively low temps is not new, in fact, their are several manufacturers that have been employing this technique for years.
    • Well, you should definitely write the Fraunhofer guys then, so they can stop wasting their time. Should teach them to do some preliminary research first the next time around.
    • Fusion of aluminum oxide is not a new development of any type. More commonly known as Ruby

      So, despite expecting some boring material science stuff, this news is indeed about computers! w00t!

  • To construct a holding tank for whales while transfering them forward into the future. Now we just need a Klingon warship and we'll be set!

    Life immitates StarTrek IV.

    • Life immitates StarTrek IV.

      I'm going to san francisco and wait for giant "foot prints" to appear in the earth, then jump onto somebody moments before they are "beamed" aboard.
      with my luck, they'll say beam me a board, and I'll be standing there with a 2x4
  • ...a semi-transparent bondi and white iCar? :)

    And how nice it would be if a rock kicked up by a semi would at most dent your windshield.

    (Yeah, I realize it will probably be quite a while before this filters down to the consumer level, but it's fun to dream.)
  • by upstairs ( 183031 ) on Wednesday February 20, 2002 @05:09AM (#3037037) Homepage
    See below:

    Also available here! [about]
  • Finally! (Score:2, Funny)

    by Big Nothing ( 229456 )
    I can walk around in public with my aluminum foil hat [] and not look stupid anymore!
  • by Anonymous Coward on Wednesday February 20, 2002 @07:26AM (#3037226)

    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


    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?].

  • micrograin materials (Score:3, Informative)

    by Genda ( 560240 ) <> on Wednesday February 20, 2002 @07:41AM (#3037250) Journal
    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;

    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...
    • Micrograin copper for instance conducts like gold, and is nearly as hard as steel (while being much lighter... this is wonderful stuff.)

      Excuse my igorance, but does it tarnish?
      that is why we use Gold in electronics, and not silver, which is more conductive.
    • believe that micrograin titania could one day make the perfect engine
      Some time ago it was determined that using different materials in different parts of an engine produced a better engine. For efficiency, you want the combustion to occur at a high temperature. To minimise weight in anything that moves, you want to have a relatively light cooling system. The ceramic engine prototypes produced to this point have had the limitation that they do not conduct heat very well (titania is also limited this way), so then a better cooling system has been required for those prototypes, which sometimes cancelled out the benifits of lower engine mass and better fuel efficiency.

      What has been done in the last decade (or more) is to have ceramic in the combustion chamber and a metal engine block to conduct away the heat. I think this has been used commercially for a few years. The other big problems with the all ceramic engine concept is that in some situations you want a bit of toughness, and that it is not yet known how to produce large pieces of high strength ceramic without a fairly high chance of significant flaws (which are going to be very small internal cracks or gaps). What this would mean in practice, is that you would make your engines, test them to beyond the conditions they are likely to experience and keep the ones that survive. A ceramic connecting rod could be made (and probably has), but something that isn't brittle would be nice in that situation, and you don't have to worry about heat, so steel is a good choice.

      SiAlON is another material to watch. Turn rice husks into jet turbine blades!

  • by Publicus ( 415536 ) on Wednesday February 20, 2002 @08:38AM (#3037368) Homepage


    Oh, wait, this one isn't about computers.. hehe.

  • by bunyip ( 17018 ) on Wednesday February 20, 2002 @09:10AM (#3037510)
    Unbreakable beer glass.

    As an aficionado of German beer, I'm sure that this will be the first real application. They just want to get the military to pay for some cool toys along the way.
    • Trouble is, hardness does not equal impact resistance. Glass is very hard and pretty strong, until a crack starts -- then it runs clear through the material. Aluminum oxide is harder, but I think it's also brittle.

      I can't really tell from the extremely bad translations, but it sounds like maybe this is a process analogous to tempering glass -- that is, heat treating it to create internal stresses that limit crack propagation. Probably very expensive. If it would make an unbreakable beer mug at a reasonable price, they'd already have tempered glass unbreakable mugs...
    • Hey, just the cool factor of having a saphire beer glass might be worth the extra cost.
  • by Byteme ( 6617 )
    Isn't my Oris [] watch crystal made from this?

  • Soon we can protect our computers from drive by shootings! Why, I just lost my third i386 to one last week.
  • by Baldrson ( 78598 ) on Wednesday February 20, 2002 @11:34AM (#3038314) Homepage Journal
    The material is very hard, and could be used as bulletproof windows

    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.

  • Metals made transparent by photonic layer structure:

    This is much more useful than transparent armor,
    IMHO, if it can indeed be applied to photonic
    band-gap filtering...
  • This would be used to create a whole new generation of Apple paraphenalia.

    The new: iCar!
    The exciting: iBoat!
    The unbelieveable: iRoof!

    The possibilities are endless, with our strong, clear steel!
  • by Bikku ( 531345 ) on Wednesday February 20, 2002 @04:32PM (#3040119) Homepage
    Materials engineering 101

    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?

  • Good read but It really doesn't explain how you could use it to say..... a million gallon tank on a starship to transport two humpback whales 200 years into the future in a desperate attempt to save mankind from a strange monolith emitting beached whale sounds.

    Jesus....what ever happened to investigative journalism these days? Also, wasn't this guy supposed to speek english?


  • Great.

    But we already have bulletproof glass. What's so special?

System restarting, wait...