

How Corning Created the Ultrathin, Ultrastrong Material of the Future - pooma
http://www.wired.com/wiredscience/2012/09/ff-corning-gorilla-glass/all/

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drostie
This article didn't mention it, so I thought I would: Glass is about as strong
as steel. Okay, okay, so glass is really a _class_ of materials with widely
varying strengths and some glasses like soda-lime are not very strong -- but
steel is also a class of materials and there is a considerable overlap with
how strong you can make glasses and how strong you can make steels. Plastics
are typically much weaker than glass, as is wood.

So why is it that we have this everyday experience that dropping a cup made of
glass is a likely disaster, while dropping a plastic or steel or wooden cup is
not? It's actually much more subtle: it's not about _strength_ , it's about
_cracks_ and _scratches_.

I am not entirely sure why, but what's happening is that in most ceramics, a
scratch creates a place where the stresses inside the material get amplified
in a way that doesn't exist with metals. So in metals those cracks also don't
like to propagate much; it's really in glass where you see cracks propagate
through the whole material. It's more obvious to see why wood doesn't behave
this way -- it's made of lots of long strands glued together, so when you
crack some of those strands, the crack "runs into" the glue and doesn't
propagate. We've actually already stolen this idea from wood -- as fiberglass.
Plastics have these really long molecules which also line up like the wood
fibers and create a very irregular environment for cracks to propagate, so
that may be why plastics resist fracture.

I've often wondered if there is a sort of "miracle glass" which exchanges the
hydrogen bonds of plastics for the stronger silicon-oxygen bonding you see in
glass, but is also built from "long molecules" the way plastic is. The idea
would be essentially to steal the strength of glass and the fracture
resistance of plastics while maintaining transparency. But if it were easy
presumably someone would have developed it by now, and I'm no materials
scientist.

~~~
pmahoney
Crack kills.

Metals are able to deform plastically. A metallic bond is not so directional,
and you typically thing of all the molecules in a metal as a big blob with a
cloud of electrons that can freely move about (also the reason for good
electrical conductivity).

There are "elastic" and "plastic" deformations. Think about bending a
paperclip. Use it gently, and you can open it up and get it to squeeze a few
papers together. Pull it off and it returns to its original shape. That's
elastic. Now open it wider or bend it into another shape, and it will no
longer return to the original shape. That's a plastic deformation.

Metals can deform plastically which means layers of atoms are sliding past one
another in waves. Sometimes these waves are stopped by various irregularities
in the crystal lattice. The waves start to pile up, preventing further plastic
deformation. Keep bending that paperclip back and forth; it will eventually
snap. But in the meantime, it absorbed a fair amount of energy. That's
"toughness".

In a ceramic, the electrons are not free to move about. If a crack develops,
it doesn't take much for there to be terrific stress at the tip of the crack
(much like a lever and fulcrum). The crack propagates through the material,
and you have catastrophic failure.

There are various ways to increase the toughness of ceramics. I'm not all that
familiar with them, but a common one is Yttria-stabilized zirconia. That's
zirconium oxide with added yttrium. Under stress from a crack, the material
can undergo a phase transformation (from one crystal structure to another; not
solid to liquid or anything like that). A phase transformation absorbs energy
(just like boiling water into steam does) which may be enough to stop the
crack from propagating. My ceramics professor had a YSZ hammer that was gifted
to him by Coors ceramics (same family as the beer company). YSZ is not
transparent however.

<http://en.wikipedia.org/wiki/Yttria-stabilized_zirconia>

~~~
Florin_Andrei
> _Metals are able to deform plastically. A metallic bond is not so
> directional, and you typically thing of all the molecules in a metal as a
> big blob with a cloud of electrons that can freely move about (also the
> reason for good electrical conductivity)._

Also the reason why metals absorb electromagnetic radiation on a very broad
spectrum.

Which means it's very difficult, if not impossible, to make materials that
behave mechanically like metals (hard, yet not fragile) but are transparent.

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binarymax
If you have the chance - visit the Corning Glass museum. Its awesome. I
haven't been there in 25 years and I still have an impression of all the cool
things I saw there.

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vilhelm_s
> From above, Corning’s headquarters in upstate New York looks like a Space
> Invaders alien: Designed by architect Kevin Roche in the early ’90s, the
> structure fans out in staggered blocks. From the ground, though, the tinted
> windows and extended eaves make the building look more like a glossy,
> futuristic Japanese palace.

In case anyone else was also curious, here is how it looks from above:
[https://maps.google.com/maps?hl=en&ll=42.145201,-77.0548...](https://maps.google.com/maps?hl=en&ll=42.145201,-77.054812&spn=0.004427,0.003154&t=h&z=18)
and from the ground: <http://www.city-data.com/picfilesc/picc5158.php>

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samwillis
@ntgx, you appear to have just been hell-band although I cant see why. Your
last 4 comments a dead.

Commenting on the top level as cant reply to you directly.

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DanielBMarkham
This article is from last year and is a dupe.

Dupes are fine, but please add dates to your titles to let us know the
information has been out there for a while.

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triplesec
I'm still waiting for someone to make a glass gorilla. Perhaps this is my next
Playa project.

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ebbv
pooma submitting this old article because the GLW portion of your portfolio
could use a boost? ;)

