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Transparent Concrete
rakerman writes: "The Economist reports in How to see through walls that development is underway on translucent concrete, with hopes of eventually developing transparent concrete. Can transparent aluminium be far behind?"
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Well, it's nice to see innovation within the construction sector isn't dead. Even for something that seems so off the wall as transparent (or currently, translucent) concreat can give birth to innovative new designs and possibilities from architechs.
I mean, I can just see a wall done with a bubble effect (with slighly differnt opacities in the aggitates and clear binding coumpound).
Only thing is, once transparent concreate is perfected... how are the mobsers going to get rid of bodies if they can't throw them in the foundation of a new building anymore...
Can transparent aluminium be far behind?
It's already here, although in the form of an oxide rather than the pure metal.
A little off topic, but germane to the item noted in the summary for this topic.
He refers to transparent aluminum from the Star Trek IV movie. In that film, they risk rewriting history by giving the technology for transparent aluminum to a 20th century factory.
They never answer the basic question of why did the aluminum have to be transparent? Why not regular aluminum or any other such material? Do the whales need a view of the Klingon starship? Do they have no cameras or sensors to let them see the whales?
It made no sense at all but it was a major plot point for the whole film. Sigh. Ok, mod me off topic now.
Has it been over a year since you last donated to the Electronic Frontier Foundation
"Can transparent aluminium be far behind?"
Yes, transparent aluminum can be far behind. Metals like aluminum have free electrons which prevent transmission of light.
Bush's education improvements were
Well, we already know the best use of it is to put windows in our starships. (heh) But even the starship windows are actually an aluminum alloy.
[For those of you missing the whole joke -- the windows on the spaceships in Star Trek are supposed to be "transparent aluminum"]
Pure transparent aluminum might be weak indeed, but perhaps it can be used in an alloy to create a transparent sheet that is as strong and durable as oridnary sheet aluminum. I find it hard that you mention steel (in particular certain varieties) yet you fail to address the usefulness of a transparent aluminum component in such an alloy.
Heck, even laminating something ordinary (ie lucite, glass) with such a material would have immediate benefits. Think diamond-tipped bits, saws, etc.
~GoRK
There is a very big difference between "transparent" and "translucent". The former means that light passes through the material almost completely unchanged (a certain amount of distortion is okay, but the point is that you can make out what's behind it). Translucent means that light is transmitted, but it's diffuse and you can't make out what's behind the material. This concrete is translucent. It's not transparent (read the article).
The reason you will never see transparent aluminum is not because of a lack of crystalline structure--in fact, I think metals generally are crystalline or at least have a crystalline microstructure. The reason that aluminum, and basically all metals, are opaque is the same reason that metals tend to be shiny. Because there are a lot of free electrons in metals (which is why they conduct electricity well), the electric field of light expends energy driving these free electrons (therefore metals are opaque), which in turn reradiate light back in the direction of the incident light (therefore metals are shiny). The amount of light that gets through goes as e^-ax where a is a constant and x is the thickness of the metal, so in a very thin metal film (e.g. mirrored sunglasses) you can still get some light through, but for any measurable thickness of metal (e.g. aluminum foil and anything thicker), the amount of transmitted light is negligible.
I know this is a very hand-wavy explanation, but it's hard to explain without a pretty advanced background in electromagnetics. If you want an explanation of this from a rigorous electromagnetic point of view you can try wading through Chapter 14 of Principles of Optics by Max Born and Emil Wolf, but its mostly math with very little physical intuition or explanation.
"It take 9 months to bear a child, no matter how many women you assign to the job."
Yes you did miss the joke. Go watch Star Trek IV, this will give you the cultural reference to 'get' the joke.
If Mr. Edison had thought smarter he wouldn't sweat as much. --Nikola Tesla
It's a shame that electrochromic windows haven't taken off. I first read about them in Popular Science, probably about 10-15 years ago, and if I recall correctly, they were used in a concept car by Ford (I could be mixing two Popular Science articles together), but they allow you to electrically darken and lighten windows, and they actually reflect light and heat (unlike liquid crystals, which just scatter light and heat but still let them through). I'm not sure, but they might also be wavelength-independent, i.e. reflecting all colors of light equally. The obvious barriers to their widespread adoption are probably cost and the ability to make panes large enough to use as windows.
"It take 9 months to bear a child, no matter how many women you assign to the job."
this april 2001 edition of Metropolis has a pretty informative article on the man and his background.
interesting that i live in houston (concrete captial next to LA) and never have read an article on this guy.
/* Half alive and half dead too, work is for suckers and the sucker is you. - "Half-life" by Local H*/
I think by either Marvin or Pella. I've seen promotional materials, and IIRC it was a kind of transparent LCD panel that could be opaqued or made mostly transparent. The downside is that I believe it took power to keep the window transparent, and it was really expensive.
Either way, modern windows, according to my wife who used to work with Andersen Windows, have a higher R factor than a lot of walls -- triple glazing, low emissivity coatings, and krpton/argon filled voids go a long way.
I hate to dignify this with a response, but an obvious counterexample to this argument is wood. I have never seen shiny untreated wood, no matter how well polished.
:-p
In general, surface roughness does affect reflectivity, especially whether the reflection is diffuse or specular, but intrinsic material properties (e.g. metallic bonding [free electrons], band gaps, etc.) are a strong factor as well. The free-electron model also explains why you can't see through aluminum foil but you can see through mirrored sunglasses. The electromagnetic theory of light also generalizes to the microwave radiation that enables the culinarily-challenged like myself to cook, and to radio waves that enable radio, television, and wireless networks. Try patching your "shiny reflective surface" theory to explain all these phenomena...
"It take 9 months to bear a child, no matter how many women you assign to the job."
I'll try to re-state Hal-9001's post in a little different form:
Electromagnetic waves consist of oscillating electric and magnetic fields in alignment so as to be self-perpetuating. The changing magnetic field creates an electric field a little further on, and the changing electric field creates a magnetic field still further on, etc.
First consider a radar beam approaching a metal surface. The E-field will cause the free electrons in the metal to move. This transfers the energy of the beam into electron motion. And with several pages of math that I went through once and never want to again, it can be shown that the electrons move so as to create a mirror-image field, re-transmitting the beam at the angle of incidence -- in other words, a reflection.
Due to resistance to electron movement, the reflected beam will be somewhat weaker, the missing energy being absorbed as heat. If the metal is extremely thin there might not be enough free electrons to fully absorb the incident beam, so part of it passes through. In an insulating material, electrons are tightly bound to molecules, and so cannot range far enough for strong interactions with the beam, and so most of the beam will pass through (the material is "transparent" to radar). However, electrons can shift around within the molecules, which causes refraction, partial reflections, and absorption.
Things are different for x-rays, because the individual photons are pretty energetic and the wavelength (size of one photon) is close to the size of an atom. So it's more likely to be the inner electrons still bound to the atoms that wind up trying to capture the x-ray, and only rarely does this succeed -- most of the x-rays get through several inches of all but the densest materials.
Visible light photons are in-between in size, large enough to interact well with the free electrons (reflection), but small enough to also be affected by bound electrons. (Selective absorption by the bound electrons gives copper and gold their color.)
Most insulators are not transparent to visible light, except as very thin films. Most insulators (like metals) consist of irregular aggregations of tiny crystals. The interactions with the electrons bound in molecules will reflect some light, absorb some, and refract all the rest. In most insulators, the interaction varies with the polarization of the photon and the angle of the crystal; since each crystal is oriented differently, each interface between crystals refracts and reflects light in different directions, so the light that isn't reflected from the external surface is scattered and (mostly) bounces around inside the material until absorbed rather than passing through.
Most transparent materials are glasses, with no crystal structure, and so no grain boundaries to scatter the light. Single crystals may also be transparent, although it's pretty hard to grow a single crystal as big as a windowpane. Multi-crystalline insulators can be translucent if sufficiently free of the atoms or molecules that absorb light, that is if the light is scattered but not absorbed eventually it will find it's way back out of the material. Concrete could be translucent if both the aggregate and the cement were free of light-absorbing materials, but I think the price would be extremely high.
Possibly a multi-crystal insulator could be transparent if the refractive index did not depend on orientation of the crystal or polarization of the light, and if all the crystals fit together neatly and had the same refractive index. Or use glass beads for aggregate and somehow make the cement match the glass?
Metals by definition have free electrons, which strongly reflect and absorb visible light. If it's transparent, it's not a metal.
You can form Al2O3 into fairly large crystals, and maybe it could be a glass too. It's stronger and much harder than silica-based glass, so it would make a great windshield, if you didn't mind the cost of using diamonds for cutting and polishing.
I've calculated a possible material to use for the binding agent, that's a no brainer: Silicone (as it can be formulated for varying degrees of clarity and density)or fiberglas epoxy resins (the added bonus of this is fairly rapid curing...
However, the ecological impact is a far better thing to consider... For example, recycled bottle glass can be ground down to make both aggregate and filler (you can seperate the colored glass and use that to add a touch of color to the finished product), and ground further down, it can act as filler as well...
Considering that the majority of states in the US only have voluntary glass recycling, it might provide incentive for deposit glass bottles, not to mention finally provide a real incentive to recycle old CRT's...
Or if you're feeling daring, you can use the same optical quality sand they use for reflective road striping to give the concrete an almost luminescent quality... For added strength, use polycarbonate rods or strips in a woven lattice...
The article stated that transparent/translucent concrete can only be prepared offsite, but in theory it can be done the same way as existing concrete, just bring a lot of drums of resin or silicone to the site...
Just because you can mod me down, doesn't mean you're right. Shoes for industry!
Sorry guys. Transparent Aluminum wasn't available in the 20th Century. Scotty traded Plexico the formula for transparent aluminum for the standard six inch plexiglass:
"SCOTTY
Doctor Nichols, I might have
something to offer you.
NICHOLS
... Yes?
SCOTTY
I notice you're still working with
polymers.
NICHOLS
(mystified)
Sill? What else would I be working
with?
SCOTTY
Ah, what else indeed? Let me put it
another way: how thick would a piece
of your plexiglass need to be at 60
feet by 10 feet to withstand the
pressure of 18,000 cubic feet of
water?
NICHOLS
That's easy: 6 inches. We carry
stuff that big in stock.
SCOTTY
Yes, I noticed. Now suppose -- just
suppose -- I could show you a way to
manufacture a wall that would do the
same job but was only an inch thick.
would that be worth something to
you, eh?
NICHOLS
... Are you joking?
BONES
He never jokes... Perhaps the
professor could use your computer.
[...]
NICHOLS
(wide-eyed)
Transparent aluminum?
SCOTTY
That's the ticket, laddie.
NICHOLS
... But it would take years just to
figure out the dynamics of this
matrix...!
BONES
You'll be rich beyond the dreams of
avarice.
SCOTTY
So, is it worth something? Or
should I just punch "clear"...
NICHOLS
No!
(then)
No... What did you have in mind...?"
Live long and prosper.
sarchasm: The gulf between the author of sarcastic wit and the person who doesn't get it.