
Transparent ceramics made with aluminum - peter_d_sherman
https://hackaday.com/2018/04/03/whats-the-deal-with-transparent-aluminum/
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dvh
Metal will never be transparent. Metal means metal bonds which means free
electrons. Free electrons are opaque to visible light.

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dbsvsv
I don't think in quite understand. You mean they don't let photons to pass
through? In which case do electrons in orbit? Or nuclei for example? Or does
this need advanced physics knowledge?

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tim333
Roughly light is electromagnetic radiation and puts force on electrons it
comes in contact with. If the electrons are fixed in a non conductor they
don't move much and so don't absorb the energy. If they can move as in most
metals the force accelerates them and they absorb energy from the radiation,
stoping of reducing it.

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agumonkey
What about partial ? or only to some wavelengths ?

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mannykannot
X-rays penetrate metal to some extent, though they also scatter off the atoms.
Radiography of high value/risk metal components (such as the stressed parts of
gas turbine engines) is a mainstream non-destructive testing technique.

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Lramseyer
This definitely looks like something that has the potential to be really
useful, and gives the example of replacing gorilla glass. While I get that
this is a very tough glass, I did not see anything about it's hardness in
relation to gorilla glass, as hardness is the property that provides the
scratch resistance that is so highly sought after in smartphone screens.

Toughness is how much energy a material can absorb, whereas hardness is the
resistance to deformation. Think a rubber band vs. glass.

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masklinn
According to wikipedia's AlON page it has a knoop hardness of ~1800 which from
my understanding of things (I may have misread sources or be mistaken, I'm not
a material scientist or even amateur) looks to be about equivalent to sapphire
glass and much higher than gorilla glass (~600).

edit: in fact while I skipped the intro it states specifically that AlON has
~85% the hardness of sapphire, which more or less checks out. Suffice to say
it has excellent hardness, way beyond gorilla glass.

I could find no data on relative permittivity though, and I assume that would
be a factor for touchscreens.

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kdumont
I believe hardness is actually a bad thing in terms of replacing gorilla glass
in phones. It increases the likelihood of shattering when dropped, and is the
main reason for sapphire not being adopted.

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masklinn
> It increases the likelihood of shattering when dropped

AlON seems significantly tougher than glass as well as being way harder. So it
looks to be both more scratch-resistant _and_ more shatter-resistant.

> is the main reason for sapphire not being adopted.

Do you have sources (actual sources, not Corning fearing for their business)
for that?

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kdumont
I'm no materials scientist. I just recall some articles I read when I was
curious why I hadn't seen sapphire showing up in phone screens. Here is the
first article Google pulls up.

[http://time.com/3377972/why-apple-didnt-use-sapphire-
iphone-...](http://time.com/3377972/why-apple-didnt-use-sapphire-iphone-
screens/)

I agree with you that AlON appears to be harder than glass. I just question if
that is necessarily a good thing for consumer electronics. I expect we want
something that is very tough but relatively flexible/soft.

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talltimtom
The deal is that it isn’t aluminium. Seriusly, what’s with the clickbate
headline? If you consider everything that contains aluminium atoms in the
structure to be actual aluminium, then Saffire is also transparent aluminium.

The authors are diliberatly misleading their readers in order to cincrease
interest. That’s a shitty thing to do in science even if do have a cool
materiale on It’s own merits.

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dboreham
The headline relates to a line in an old movie (which is mentioned in TFA At
the bottom of the page).

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a_t
The mental imagery of denting, bending and crushing a transparent glass-like
material and having it react the same way aluminium would is immensely
satisfying for some reason

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jackhack
Am I the only one to recoil at the thought of someone chewing transparent
aluminum foil?

The potential is tremendous in aviation. Imagine transparent aircraft skins --
the superstructure and internals (fuel tanks, hydraulics, etc.) could be
inspected without disassembly (which itself adds stress to the structure).
Though I'm not sure passengers would take kindly to aircraft with transparent
skins. Sometimes it's best that things are hidden under a bonnet.

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lainga
You could wrap the cabin interior with OLED panels that are normally active
and opaque during flight.

Then, when you're on a longhaul and it's time to wake the passengers up - turn
them off in midair. Good morning!

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jackhack
Brilliant. If the sudden increase in luminosity didn't wake you, the screams
of fellow passengers looking through the invisible floor at the ground/Ocean
30,000 feet below would surely do the trick!

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Sharlin
Other examples of "transparent aluminum": ruby and sapphire, both of them
varieties of the mineral corundum, or Al2O3.

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no_identd
Slashdot, 2004:

[https://slashdot.org/story/04/08/23/1141217/transparent-
alum...](https://slashdot.org/story/04/08/23/1141217/transparent-aluminum-is-
here/informative-comments#comments)

tl;dr: Transparent alumin_a_, not transparent alumin_um_.

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jboy55
On a completely separate note, what was the deal with the need for transparent
aluminum in Star Trek IV?

Looking at the footage, they easily could have made the tank bigger if they
just used all of the space available and didn't need to be able to "see" them
from outside their tank. All they would have needed the aluminum for is to
keep water out of where water shouldn't go and regular aluminum (or other
material) would have worked just as well.

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mohaine
I don't think they used transparent aluminum in Star Trek IV.

I thought they paid for whatever they used (plexiglass?) with the recipe for
transparent aluminum.

Although it could just be that I'm forgiving the poor writing.

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emaginniss
Wouldn't that mean that nobody ever invented it?

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delecti
No humans maybe.

And if humans were in fact the source of Starfleet's knowledge of transparent
aluminum then it'd be an instance of a causal loop, of which there are many
examples in fiction.

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Izkata
> of which there are many examples in fiction.

Hell, there's several examples just in Star Trek.

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John_KZ
Saying this is transparent Aluminum is the same as saying Glass is transparent
Silicon. It's not, it's just a ceramic.

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pwg
The title is a reference to a line in the movie "Star Trek IV: The Voyage
Home" where Scotty trades the formula for "transparent aluminum" (from the
future) in a barter transaction for plexiglass sheets (in the present) that
the cast need to achieve their goal in the movie.

[https://en.wikipedia.org/wiki/Star_Trek_IV:_The_Voyage_Home](https://en.wikipedia.org/wiki/Star_Trek_IV:_The_Voyage_Home)

[https://en.wikipedia.org/wiki/Transparent_aluminum#Transpare...](https://en.wikipedia.org/wiki/Transparent_aluminum#Transparent_aluminum)

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kristianp
This isn't new, I've read articles on AlON before. Synthetic Sapphire is more
interesting in that its use is growing quickly due to demand for LED and laser
substrates. Large single crystals are grown and sliced into wafers:
[https://en.wikipedia.org/wiki/Kyropoulos_process](https://en.wikipedia.org/wiki/Kyropoulos_process)

New producers of the High purity Alumina (HPA) needed to produce sapphire are
coming online, perhaps prices will come down enough that phone screens are an
application, but I suspect that this is marketing speculation from the HPA
makers to attract investors. For example this presentation from a HPA company
speculated in 2015 that the iphone 7 would use a sapphire screen, which turned
out to be wrong:
[https://www.altechchemicals.com/sites/altechchemicals.com/fi...](https://www.altechchemicals.com/sites/altechchemicals.com/files/asx-
announcements/6738553.pdf)

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kaennar
Does the fact that there is aluminum inside of the ceramic mean that it has a
higher conductance? I couldn't find a reference online (there seems to be a
few papers over the conductance of two very thin plates of AL203, but no
characterization)

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coldcode
While it isn't a metal its still amazing stuff. Sometimes I wish I had stuck
with my PhD in Chemistry which would have been working for someone who made
equally wild materials.

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beeforpork
At last, the whales can be saved!

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Tomminn
Synthetic sapphire is a trivial example of a transparent ceramic made with
aluminium. Its formula is something very close to Al_2 O_3.

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georgeecollins
I believe the first Apple Newton had transparent aluminium for the screen. I
can't find confirmation of that but I remember going to a sales training
session for it (long story) and they told people to say the screen was
transparent aluminium, like they talked about in one of Star Trek movies.

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equalunique
This is about the same material which transparent circuit boards are
fabricated with: [http://www.dk-ceramics.com/transparent-pcb/](http://www.dk-
ceramics.com/transparent-pcb/)

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antibland
Jerry Seinfeld's new material has become super arcane.

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rpledge
I think transparent aluminum foil would be awesome - I could tell if my
potatoes are cooked on the BBQ without opening the packet.

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tim333
tl;dr the substance is probably a ceramic, aluminum oxynitride. Which seems a
bit of a cop out like calling regular glass transparent sodium because it
contains some. It seems quite cool stuff though.

