Transparent ceramics made with aluminum • Hacker News Board

Re: Transparent ceramics made with aluminum

#41

Post by saiya-jin » Wed, Apr 04, 2018, 2:41 PM UTC

jacquesm wrote: post #35

dvh wrote: post #3

Metal will never be transparent. Metal means metal bonds which means free electrons. Free electrons are opaque to visible light.

If the film is thin enough metal is transparent. See for instance 50/50 mirrors and gold plated windows. Of course you can now argue that if the photons hit the metal they will not pass through, but that's not how it works: the photons will excite an electron to a higher orbit and it may drop back to a lower orbit on the other side of the film making the metal appear transparent or it may reflect. edit: saiya-jin I c…

that doesn't make sense - if that would be the case, the back-emitted photon would have a random vector, not pertaining the same one as original one (thus preserving the picture beyond the sheet of metal).

you are stating somehow the direction of photon is preserved when absorbed by electron - absurd idea even for layman physics (not claiming I know how this works, but this can't be the way)

Re: Transparent ceramics made with aluminum

#42

Post by mohaine » Wed, Apr 04, 2018, 2:42 PM UTC

jboy55 wrote: post #37

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) wo…

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.

Re: Transparent ceramics made with aluminum

#43

Post by kaennar » Wed, Apr 04, 2018, 2:44 PM UTC

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)

Re: Transparent ceramics made with aluminum

#44

Post by friedegg » Wed, Apr 04, 2018, 2:44 PM UTC

jboy55 wrote: post #37

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) wo…

It's been a while since I've watched the movie, but I don't think they specifically needed transparent aluminum, but it's how Scotty paid for them getting what they needed. They didn't have money to pay for it, so this was a barter, the knowledge of how to make it for making them some.

Re: Transparent ceramics made with aluminum

#45

Post by jackhack » Wed, Apr 04, 2018, 3:15 PM UTC

a_t wrote: post #31

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

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.

Re: Transparent ceramics made with aluminum

#46

Post by beeforpork » Wed, Apr 04, 2018, 3:15 PM UTC

At last, the whales can be saved!

Re: Transparent ceramics made with aluminum

#47

Post by melling » Wed, Apr 04, 2018, 3:23 PM UTC

jboy55 wrote: post #37

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) wo…

https://www.reddit.com/r/startrek/comments/3luo7c/in_star_tr...

Re: Transparent ceramics made with aluminum

#48

Post by ASalazarMX » Wed, Apr 04, 2018, 3:39 PM UTC

mohaine wrote: post #42

jboy55 wrote: post #37

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) wo…

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.

This. They didn't have money, so they bartered with information.

Re: Transparent ceramics made with aluminum

#49

Post by dbsvsv » Wed, Apr 04, 2018, 3:42 PM UTC

Steuard wrote: post #34

dbsvsv wrote: post #10

Earlier quoted context omitted.

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?

On a quantum level, when a photon encounters a material you have to ask whether the material is able to absorb a photon with that wavelength. When electrons are bound to a specific atom (or are in specific molecular bonds) then there are only certain energy levels possible: that's one of the core features of quantum systems, and it's the reason that each material has its own characteristic "absorption spectrum" (or e…

Thank you. That's very helpful. I studied the quantized transfer but never bothered to ask what happens if electron is hit by the energy isn't exactly what's required for an orbital transition.

Re: Transparent ceramics made with aluminum

#50

Post by castle-bravo » Wed, Apr 04, 2018, 3:45 PM UTC

Confusion wrote: post #40

castle-bravo wrote: post #33

Earlier quoted context omitted.

You don't need bandgaps to understand why conductors (other than thin films of ITO) don't transmit light. You derive it from Maxwell's equations and the fact that in a conductor, current density = conductivity * electric field. Griffiths' Introduction to Electrodynamics is the standard undergraduate textbook on electromagnetism, and explains this reasonably well. For bandgaps, Ashcroft and Mermin's Introduction to So…

Ashcroft and Mermin is only an 'introduction' in the graduate student sense of 'introduction'. I don't think you can make sense of it without previous grounding in both quantum mechanics and solid state physics.

Well, he did ask about band gaps. Is there a way to understand band gaps without quantum mechanics? I think you only need a little Fourier analysis to get the basics of band gaps.

Anyway, that text and along with Kittel's are the references for an undergraduate solid state course that I'm taking. No prior exposure to solid state physics for me and only introductory quantum mechanics (first half of Griffiths' QM); I find the text totally approachable.