New glass almost as tough as steel

November 4, 2015 by Bob Yirka report
Transmittance spectrum of the 54Al2O3-46Ta2O5 glass in the UV/vis region. The inset picture shows the glass sample used for the transmittance experiment. Credit: (c) 2015 Scientific Reports (2015). DOI: 10.1038/srep15233

(—A team of researchers with The University of Tokyo and Japan Synchrotron Radiation Research Institute has created a type of glass that is stronger than many metals. In their paper published in the journal Scientific Reports, the researchers describe how they overcame one of the major hurdles in creating glass imbued with extra amounts of an oxide of aluminum, by using what they call aerodynamic levitation.

Glass that does not break when dropped or when struck by another object would be useful in a wide variety of applications, from automobile windows, to skyscrapers to smartphones and tablets. For that reason, scientists have been searching for ways to make traditional stronger. One of those ways has been to add larger amounts of an oxide of aluminum to the mix, specifically, alumina, because it has one of the highest dissociation energies among oxides. Prior research has shown that glass made with such an addition would be much stronger than traditional glass. Researchers have been prevented from creating such a glass, however, because of a problem in the production process—when more alumina is added to the mix while the glass is being made, silicon dioxide crystals develop where the mix meets the surface that is holding it, making the end product worthless as a glass. In this new effort, the researchers found a way around this problem—by removing the container from the process.

The new process involves causing the mix to be held in the air while it is forming, by pushing it from below with oxygen gas and then using a laser as a spatula to mix the materials together. The end result is a glass with more alumina in it than any other produced to date—a glass that the team reports is transparent, colorless and extremely hard. Testing showed it to be stronger than most metals, and almost as strong as steel.

The only thing holding up the production of shatter-proof smartphone screens using the new glass is that the team still needs to find a way to convert their method to a mass production process—they appear confident that such a way will be found, as they promise to find a way shortly.

Explore further: Researchers find out why high-performance glass flows, and how fast

More information: Gustavo A. Rosales-Sosa et al. High Elastic Moduli of a 54Al2O3-46Ta2O5 Glass Fabricated via Containerless Processing, Scientific Reports (2015). DOI: 10.1038/srep15233

Glasses with high elastic moduli have been in demand for many years because the thickness of such glasses can be reduced while maintaining its strength. Moreover, thinner and lighter glasses are desired for the fabrication of windows in buildings and cars, cover glasses for smart-phones and substrates in Thin-Film Transistor (TFT) displays. In this work, we report a 54Al2O3-46Ta2O5 glass fabricated by aerodynamic levitation which possesses one of the highest elastic moduli and hardness for oxide glasses also displaying excellent optical properties. The glass was colorless and transparent in the visible region, and its refractive index nd was as high as 1.94. The measured Young's modulus and Vickers hardness were 158.3 GPa and 9.1 GPa, respectively, which are comparable to the previously reported highest values for oxide glasses. Analysis made using 27Al Magic Angle Spinning Nuclear Magnetic Resonance (MAS NMR) spectroscopy revealed the presence of a significantly large fraction of high-coordinated Al in addition to four-coordinated Al in the glass. The high elastic modulus and hardness are attributed to both the large cationic field strength of Ta5+ ions and the large dissociation energies per unit volume of Al2O3 and Ta2O5.

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5 / 5 (6) Nov 04, 2015
So Star Trek comes true again even though Scotty called it transparent Aluminum.
3 / 5 (1) Nov 04, 2015
Close, but not quite, as Scotty's Transparent Aluminum was a complex plastic compound derivative of plexiglass, not silica and aluminum oxide. Remember that he was using the computer at Plexicorp to demonstrate the compound's structure to Dr. Nichols there.
5 / 5 (1) Nov 04, 2015
It doesn't matter how strong it is - how brittle is it?
4 / 5 (1) Nov 04, 2015
So Star Trek comes true again even though Scotty called it transparent Aluminum.

Who knew that Scotty's sapphire included Tantalum? And was made using aerodynamic levitation? Getting back to reality, how much silica is in that glass?
5 / 5 (3) Nov 04, 2015
Scotty's probably didn't use aerodynamic levitation. With orbital manufacturing freefall would do the same thing for free. This could be worth enough to make at least small scale space industry profitable.
3 / 5 (2) Nov 04, 2015
iPhone 10 will be wrapped in this.
5 / 5 (4) Nov 04, 2015
It doesn't matter how strong it is - how brittle is it?

from the actual article,
The indentation cracking resistance (CR) was estimated to be 2.50 ± 0.13 N, which is comparable to a commercial Vycor glass
5 / 5 (3) Nov 04, 2015
Computer? Hello, computer.
not rated yet Nov 04, 2015
Why don't they just polish off the crystal-laden part?
not rated yet Nov 04, 2015
I'm curious as to how it compares to Aluminium OxyNitride, which has been in production for years under the name ALON, and is bullet proof and used in many armour applications. Also, Scotty mentioned that Plexicorp was STILL working with polymers, so his 'transparent aluminum' was not a plastic derivitive, but a ceramic like ALON, which has been called transparent aluminum by a lot of groups.
5 / 5 (2) Nov 04, 2015
Computer? Hello, computer.

Just use the keyboard...
Steve 200mph Cruiz
4 / 5 (1) Nov 04, 2015
All those elements are found on the moon in reasonable quantities, even tantalum was found by the old Soviet programs.
Maybe this would be useful on moon bases so they can have larger windows able to fight the vacuum of space
Lex Talonis
not rated yet Nov 05, 2015

Shatter Resistant?

Notch (scratch) sensitivity?

Fracture mode under cyclic stress?

Ability to deform, bend, flex, twist etc?

A most basic scientific production method for Prince Ruperts Balls - heat soda glass bar, draw into thin wire, break in two, melt ends into small balls and then drop balls into water, while bright red hot....

Super HARD glass, shatters like a bomb.

4.3 / 5 (6) Nov 05, 2015
so they can have larger windows able to fight the vacuum of space

There is remarkably little to see in space. Windows are just an additional place where stuff can break.
Better to keep everything bunkered in (or even better: underground. Certainly preferrable with respect to micrometeorite and radiation protection)

If you really want a window, project the outside view on a wall.
5 / 5 (1) Nov 05, 2015
The windows will be required in bases on moons or planets. Everyone likes a view of the landscape.
1 / 5 (1) Nov 05, 2015
And yesterday's UC Stabbings. Don't let such guys get this kind of stuff.
Flying in a Transparent Plane will be NICE; Just shield the Toilets.
4 / 5 (4) Nov 05, 2015
Everyone likes a view of the landscape.

If that view can kill you? I'd pass.
Better to create green interior spaces and have a view to that. Such spaces'd be needed anyhow for food production and increase of air quality (not to mention any kind of recreation. The human psyche is particularly susceptible to the green of growing vegetation).

I think the kinds of starships represented in models (or on TV or in video games) are unrealistic. They all have windows/cockpits (with the notable exception of Star Trek). That seems like an anachronism taken over from Earthbound planes/ships (where it makes sense). In space? Not so much.
5 / 5 (4) Nov 05, 2015
antialias_physorg: I agree, for two reasons. Not only are windows a waste of space, and a leak risk, but putting the control room in the middle of the ship protects it from impacts.

An HD viewscreen is much more flexible than a window, and one couldn't fly a spaceship visually anyway. By the time a small obstacle, such as another ship, was visible, there wouldn't be time to dodge it. A tactical navigation display would be a lot clearer than trying to look at even magnified direct views, and a viewscreen could also show visual information based on nonvisual detectors, using false-color pictures.

5 / 5 (1) Nov 05, 2015
aa_p: Nominally I'd agree on the windows in space thing.... but the truth is that humans are fundamentally not rational, when it comes down to it. Would my eyes notice a difference between a (sufficiently high quality) image projection and the "real" thing? Probably not. But as a non-rational human person, knowing that what I'm seeing is light reflecting off of/emitted from an object without being electrically/chemically encoded and then represented by other photons... it makes a psychological difference.
5 / 5 (1) Nov 05, 2015
Well, after seeing stuff like this (artificial skylight)
I'm not so sure, anymore. I'd love to have this at home if it weren't so darn expensive.
Projection mechanisms are pretty good (and there's really no reason why you can't project a view from the outside).
If you want to see the landscape direct you can always don a suit and go outside.

Seriously: when was the last time you actually stood in your apartment/house/workplace and actively looked out the window?
5 / 5 (1) Nov 05, 2015
Computer? Hello, computer.

Just use the keyboard...

the funny part was that Scotty actually remembered how
5 / 5 (1) Nov 06, 2015
Scotty was interested in ancient technology, so it isn't that surprising. Also, I suspect that they're still used in the 23rd century, although they may not look anything like ours. Even today a lot of devices have virtual keyboards on the touchscreens.

For unusually noisy, or crowded, locations a keyboard would be easier to use than voice. After all, his ship is still controlled by buttons and levers, probably for the same reason. The computer should be able to do everything by voice, but for some reason Starfleet doesn't do that, probably to avoid confusion. Just imagine if a captain really got mad and told someone to "go to ....", Wouldn't work too well if the computer thought it was being addressed!

Another reason is for backup. If the voice-response system fails, they need some way of giving commands to the computer. The keyboard may be out of sight, but it's probably there.
5 / 5 (1) Nov 06, 2015
Seriously: when was the last time you actually stood in your apartment/house/workplace and actively looked out the window?

I do it frequently; it's very pleasant and relaxing. Do you live/work opposite a concrete wall, or something?
5 / 5 (3) Nov 06, 2015
Do you live/work opposite a concrete wall, or something?

When I leave for work it's dark and when I get home it's dark (at least this time of year). When it's not then I go outside and go cycling rather than staring out the window (it'd only be a view of the courtyard in any case. It's done up all nice and pretty with trees and whatnot, but it isn't any particularly expansive scenery. A minute ride will get me along either of two rivers where the view is splendid.)

At work it's not concrete but lead walls. I commute a lot between my desk and testing-places (and since these have to do with medical x-ray machines it's a rather good idea to not have windows.)
5 / 5 (1) Nov 06, 2015
@antialias_physorg I understand — I hope you have nice vacations anyway.
Manfred Particleboard
not rated yet Nov 07, 2015
Coefficient of expansion? It isn't given in the paper. With a Tg of 858 you could be forgiven for thinking that it might be possible to join to Borosilicate 7740 (Tg 821). But 7740 has a Young's modulus of 63GPa and this stuff is around 158GPa. Would love to play with glass to metal seals with this stuff.
Steve 200mph Cruiz
5 / 5 (1) Nov 08, 2015
The night sky on the moon is much more vivid than it is on earth.

Plus the sun still shines the moon, properly regulated windows would help cut down on energy costs in managing the internal climate, provide light for plants, and keeping your sanity.

You are going to need lounging and recreational rooms, without much internet or TV, a pool table, some books, instruments, and a spectacular view of the sky might be the only fun to occupy your mind after a few years.
Captain Stumpy
not rated yet Nov 08, 2015
without much internet or TV
why couldn't we have internet on a Moon base?
surely you could set up a satellite system?
a martian base, i could understand some limitations (dial-up with frozen molasses speed) but that doesn't mean a local can't be set up, either
a pool table
that would be SO cool in a low-g environment... puts 3-D chess to shame for sure, right?
we could call it "Dodge pool" or "combat billiards"
provide light for plants
but it would also provide a lot of extra radiation as well, wouldn't it? IMHO - i would surmise that growing locations (for food) would typically be shielded or underground to insure the maximum safety etc.? (artificial lights, hydroponics, more) would be a good idea for this type operation to be in the more protected locations due to the beneficial nature of sustenance, O2, etc

but then again, given we don't have examples ...
Steve 200mph Cruiz
not rated yet Nov 08, 2015
Yeah I don't know about pool on the moon lol

But what radiation are you talking about? Maybe the material is very transparent to UV and X rays, but I think it would block hydrogen ions from the sun. Cosmic radiation is the really bad stuff but there isn't really any sort of material shield that actually helps stop metal ions, they just explode into a ton of other particles.

Maybe my point is moot from that reality
not rated yet Nov 09, 2015
So this glass is 'tough as steel'.

If so, what is the plastic strain at yield for this material.

Can we see a stress-strain curve or fracture toughness figure.

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