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Thread: Let's talk about ceramic.

  1. #31
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    Quote Originally Posted by Inclusa View Post
    There are loads of cheap watches that made to look like ceramic.
    One advantage of plastic is its relative softness, but it gets brittle with age.
    That statement is like something from the 1950s and comes into the category of not even wrong. You cannot generalise about plastic today! And the same goes for ceramic you are talking about broad categories and no physical properties can be assumed for the group.

  2. #32
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    Sorry, I don't know the diversity of ceramics before; as for metal, would you try to make a knife with pure zinc?

  3. #33
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    Quote Originally Posted by swampyankee View Post
    For at least 40 years, there have been active efforts to get ceramics to work for turbine blades. I think they've been used in some turbine nozzles, which don't have to deal with the inertial loads due to high rotational velocities (gas turbines tend to run at between 250 and 500 m/s tip speeds). I also believe there was a small (passenger car engine) turbocharger with a ceramic turbine.
    the 1987 Buick GNX used a turbocharger with a ceramic impeller for faster spool up. i believe they were built by Garrett. if you run across one of those turbochargers, they are worth a pretty good chunk of change since there were only 547 of those cars built and that particular turbo was never sold separately.

  4. #34
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    Quote Originally Posted by Inclusa View Post
    Sorry, I don't know the diversity of ceramics before; as for metal, would you try to make a knife with pure zinc?
    No, but I might try with a zinc-aluminum alloy.
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  5. #35
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    There is an alloy we used to call ZAM (zinc aluminium metal) that exhibits superplasticity, great fun and many impact back extrusion applications. I don't know why Inclusa would want a zinc knife unless also quetioning the rather vast question of engineering properties of metals. super stainless knives today stay sharp and for everyday use are stainless, very clever alloy. Is this thread going to vaguely question all materials, it is a big subject and needs a specific question.??

  6. #36
    A lot of cheap stuff has been made from cast zinc, and a zinc knife would be as good as your typical plastic disposable stuff or something carved from wood. These cast items are usually an alloy with something else, but the alloy was often just "whatever melts in the pot", so pure zinc isn't impossible. Why ask, though? There's other metals that would be totally unsuitable for knives (good luck with a knife made from NaK eutectic alloy, which would explosively react with water and be liquid at room temperature).

    My point was that the word "metal" covers an enormously wide variety of materials, and ceramics are at least as varied (as are plastics, for that matter).

  7. #37
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    ^^

    Similarly, gallium, indium, or mercury would be poor choices for knives.
    Information about American English usage here and here. Floating point issues? Please read this before posting.

  8. #38
    Quote Originally Posted by Swift View Post
    Well, the American Ceramics Society (of which I am a member) has talks and sessions about glass at their conferences, so it must be a ceramic!
    Not only that, but if you replace the GL in glass with CER, and then replace the SS with MIC, you get ceramic!
    As above, so below

  9. #39
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    Nice pdf (57 pages) on space uses
    http://www.uhtc.cira.it/presentazion...ridge_NASA.pdf

  10. #40
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    I have two crowns. One is ceramic, the other gold. The doctor said the ceramic crown would last longer, provided I stopped chewing ice.

    I wonder how he knew I liked chewing ice?

  11. #41
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    I have a friend who bought one of those ceramic bladed knives with the molecular edge that cost 80 dolars an inch.

    The blade was so sharp it parted skin before the pressure sensing nerves in your fingertip could register you were touching something. You could only tell after the noxi-receptors in your flesh went off.

    My brother and I decided to hide it after my friend started a drinking game wherein one tries to touch the edge without cutting yourself. If you drew blood, you took a shot. This got progressively stupider, rapidly.

  12. #42
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    Yikes...I wonder if there are arrow heads like this--not of obsidian I mean.

    "I wonder how he knew I liked chewing ice?" A lot of folks have pica--is it? My parents eye doctor asked them if they had raised chickens. He could tell from the particles in their eyes, or something.

  13. #43
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    Quote Originally Posted by publiusr View Post
    Yikes...I wonder if there are arrow heads like this--not of obsidian I mean.

    "I wonder how he knew I liked chewing ice?" A lot of folks have pica--is it? My parents eye doctor asked them if they had raised chickens. He could tell from the particles in their eyes, or something.
    Technically pica is the eating of non-food objects. I've seen people with absolutely horrible cases of it. (This will make your skin crawl.) I knew a man who couldn't pass up a cigarette butt, anywhere, without eating it. He would empty butt kits outside of bars until the bouncers ran him off for freaking out the clientele. He wasn't what you call very employable. He had other OCD issues as well.

    Properly knapped, glass makes excellent arrow heads.

  14. #44
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    Oh, public health took him away after he developed TB somehow...

  15. #45
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    Yep, glass is great. I've knapped some things from old toilet tanks - very hard and grainy.

  16. #46
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    Aren't toilet tanks normally porcelain or some other sintered ceramic? I.e. not glass.
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  17. #47
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    There is also cofired ceramics, which allows you to do tricks that are not really possible with other materials: http://www.chem.ucalgary.ca/research...cc%20paper.pdf

  18. #48
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    Not sure what the correct definition of toilet tank material is, but ceramic (as long as the fracture is conchoidal) can be knapped - the glaze on the outside makes it a little tricky

  19. #49
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    You can also make satellite thrusters using ceramics: http://news.boisestate.edu/update/fi...wningPaper.pdf

  20. #50
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    Ok, sorry for my relative ignorance on materials.
    We need to be specific whenever we talk about materials, though.

  21. #51
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    Quote Originally Posted by Inclusa View Post
    Ok, sorry for my relative ignorance on materials.
    We need to be specific whenever we talk about materials, though.
    Don't worry Inclusa, you have to learn how to talk to these people.

    You wouldn't believe the education I got discussing something I thought was as simple as how many gee's in a 60 mile per hour right angle turn. (Infinate gee's in a *true* instantanous right angle turn. Don't ask.)

  22. #52
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    Quote Originally Posted by cjameshuff
    Indeed, it makes about as much sense as, say, talking about "metal" being good or bad for knives...try making a knife out of lead or sodium. Ceramics are at least as varied as metal alloys. Piezoelectrics that perform their basic function by flexing, materials designed to a specific dielectric constant or for low losses at high frequencies, magnetically soft ferrites, rare earth magnets, high temperature (as in liquid nitrogen) superconductors, high temperature (as in arc furnace) furnaces and crucibles, dinnerware, tank armor, abrasives and cutting tools...
    Thank you for informing me!
    May be a little off topic, but guess what I found amongst stainless steel scissors? A moustache scissor, or the common paper scissor, is way softer than something that cuts wires; I used to consider such "soft" scissors as garbage, but they serve different purposes.
    The point is to use everything for their proper purposes.

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