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Material Tougher Than Diamond Developed
Posted by
Zonk
on Sat Feb 03, 2007 11:37 PM
from the diamond-is-so-20th-century dept.
from the diamond-is-so-20th-century dept.
sporkme has handed us a link to a New Scientist article. The piece outlines the development of a new substance reported to be stiffer than diamond. A team of scientists from Washington, Wisconsin, and Germany combined the ceramic barium titanate and white-hot molten tin with an ultrasonic probe. The new material was, in some tests, almost 10x more resistant to bending than diamond. Composite materials researcher Mark Spearing of Southampton University comments on the result: "The material's stiffness results from the properties of the barium titanate pieces, Spearing says. As the material cools, its crystal structure changes, causing its volume to expand. 'Because they are held inside the tin matrix, strain builds up inside the barium titanate,' Spearing explains, 'at a particular temperature that energy is released to oppose a bending force.'"
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That's impossible! (Score:4, Funny)
Re:That's impossible! (Score:5, Funny)
Parent
Re:That's impossible! (Score:5, Funny)
News for ______. Fill in the blank, and welcome.
Parent
Re:That's impossible! (Score:4, Funny)
Parent
Re:That's impossible! (Score:5, Informative)
A common way to measure the Young's modulus is to support a sample of the material on two struts, and then apply pressure from above to the center of the sample. The less it bends, the higher the Young's modulus. The apparatus looks like this [doitpoms.ac.uk].
Strength is a different quantity. Strength is the amount of force needed, per unit cross-sectional area, to cause the material to fail. For tensile strength, this means pulling apart. For compressive strength, it means collapsing. A material with great tensile strength can have a great weight hung from it without snapping, and a material with great compressive strength can act as a pillar to support a great deal of weight.
The article claims nothing about the strength of this material.
Parent
Space flight (Score:5, Interesting)
Not really. Here's how it works (sort of) (Score:5, Informative)
Barium titanate is a structure called a spinel. It has oxygen ions packed in a face-centred cubic structure, with the barium and Titanium ions stuck on the holes between. Above a certain temperature, spinels are cubic. however, at lower temperatures, the structure can reduce its energy by breaking symmetry and squashing a bit down one of the cubic axes, becoming orthorhombic. This compression is not huge, but it is a lot bigger than the typical stretchings you get due to thermal expansion or mechanical stress.
Stick the spinel structure into a tin matrix and cool it. If you are ingenious about your choice of tin matrix, then the stress on the tin can actually get the spinel to change its shape in a way that opposes the bending, rather than going with it as you might expect. Tin is funny stuff - it also has a change in crystal structure on cooling from cubic to hexagonal (though at a much lower temperature) so I guess it is somehow squeezing the spinel in some anisotropic fashion and triggering the phase change.
This is ingenious stuff but it isn't really a high stiffness in the normal sense, any more then the compound pendulums you can somtimes find in grandfather clocks have a very low thermal expansion coefficient. Those have brass and steel rods which all have expansion coefficients, but they are put together in a way that makes the stotal expansion zero. Supposing you had a piezo crystal, with attached electronics that applied a voltage causing it to resist any force put upon it. You could make this infinitely stiff depending on your level of control, or even have it push pack on what is pressing on it.
So, back to your original question. It is heavy, and it only demonstrates the stiffness over a limited range. Bulk material stiffness is not usually important - you can make stiff structures like a cage of tubes by design. However, if you wanted to make some structure appear perfectly stiff, then some active control like the hypothetical piezo stuff I described earlier would probably be lighter and better. I would love to know what this ingenious stuff is for, but I don't think it is for space.
Parent
Ah misleading Slashdot article titles... (Score:5, Informative)
Not to knock the experiment though, it seems interesting, and I'm sure there are all sorts of new exotic materials on the horizon.
Bah (Score:5, Informative)
http://en.wikipedia.org/wiki/Toughness [wikipedia.org] : Toughness
http://en.wikipedia.org/wiki/Stiffness [wikipedia.org] : Stiffness
Re:Bah (Score:4, Informative)
The most typical test of hardness is attempting to scratch a material. (To measure a material's hardness on the Mohs scale, essentially a series of scratch tests are performed, and a material's place on the Mohs scale was determined by what it could scratch vs. what would scratch it.)
I don't know about stiffness, but diamonds are definately not *tough*. As your links above show, "toughness" is resistance to fracturing under stress, and one of the ways diamonds are cut and shaped is by fracturing them along their crystal lattice planes. There are plenty of materials (Including, I believe, many plastics) that are *tougher* than diamond, but not necessarily harder. (For example, I believe ABS plastic and polycarbonate plastic are extremely tough, but neither are hard - i.e. they are VERY difficult to break via stress and impact, but scratch easily.)
Parent
Stiffer than diamond? (Score:4, Funny)
Hardness != toughness, get it right (Score:5, Informative)
Nope (Score:5, Funny)
resistant to bending .... (Score:5, Interesting)
This, "resistant to bending" terminology seems like a real stretch of imagination to me. When do we, as average people ever consider the force involved in -bending- a diamond? It really doesn't sound like a practical thought experiment, and therefore doesn't sound even mildly interesting.
Spider's Silk is 'stronger' than steel - we've all heard. But there's about 1000 reasons you can't build a ship, or a building or even a walking-cane out of spider's silk.
This just sounds like bad hype to me ; what I want to know, and what I think everybody wants to know is - will you be able to CUT THE DIAMOND with this material. Diamonds have been the upper-limit of our prowess with cutting-wheels ; do you have a better material for grinding and cutting? Don't confuse the issue.
Unfortunately I couldn't read the article (slashdotted? what the hell) so I'm going based on the write-up available. don't hate me if the article answers my question.
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hate me? nahhh [douginadress.com]
Re:resistant to bending .... (Score:5, Interesting)
No, you will not. The material is only stiffer than diamond in a narrow temperature range. If you tried to cut with it, it would heat up and lose this stiffness.
The article does a lousy job of explaining this temperature-dependent stiffness to non-experts. From what I understand, this is how it works: one of the two components is like a framework of tinkertoys, and the other is like a bunch of water balloons filling up the gaps in the tinkertoy structure. Both the tinkertoys and the water expand as the material's temperature is increased, possibly at varying rates. In that small range at 58 degrees F, the water baloons fit very tightly in the structure. They strain the tinkertoys, but don't break them. The tinkertoys flex as they usually would because the water balloons are holding them in place, so the entire assembly is very stiff.
Parent
Re:resistant to bending .... (Score:5, Interesting)
The hardest known material, at present, would be aggregated diamond nanorods. (These are apparently produced by crushing buckyballs at extreme pressures. What "Get Fuzzy" makes of this is currently unknown.)
Parent
Re:Wait a minute (Score:5, Informative)
Parent
Re:Wait a minute (Score:4, Informative)
steel, hardest iron (early); anything hard, adamant; white sapphire; diamond;
Parent
Re:Wait a minute (Score:5, Informative)
Your car isn't made of steel any more but foldable, collapsable sections so the car takes damage instead of the people inside. Literally the materials are designed to bend at certain deceleration speeds. This goes back to the passenger compartment, where those sections suddenly become stronger. Ever notice how in a car wreck the only thing in one piece is the passenger compartment? The entire engine will go missing first.
Parent
Re:Wait a minute (Score:5, Informative)
Parent
And even that... (Score:5, Informative)
strength: maximum load before failure
stiffness: resistance to deformation
toughness: tendency to avoid reduction in strength over time in the face of repeated deformation
also:
hardness: ability to resist permanent deformation, particularly vs. small surface insults like scratches and indentations.
Diamond is very strong, very stiff, and very hard but it is definitely not tough: large blocks of the stuff are fairly brittle and tend to crack and chip. In fact extremely stiff materials are often not tough because they are brittle. OP has a very screwed-up title.
From TFA, we have no idea whether or not this new material is either strong or tough or hard: only that it is extremely stiff. (cue tasteless jokes)
Parent
Re:Wait a minute (Score:5, Informative)
Note however that we don't need a stonger abrasive material. Grinding works on the basis of extreme velocity on the part of the particles in the abrasive wheel or band to do the cutting work. Aluminum oxide would work for the purposes of grinding this material into print. Given that it's a ceramic within a tin matrix; ALO2 would do beautifully.
As for heavy cutting work, Tungsten Carbide would do just as well. I don't see anything to indicate that the material is HARDER than carbide.
And speak of the applications..........to tell you the truth there really aren't that many widespread uses for a material like this. For now, with the expense of this material that's going to stay as it is for quite a while, there are FEW cases that would warrant using this material.
Parent
Re:Better than... (Score:4, Funny)
Unobtainium?
Parent
Re:Obligatory... (Score:5, Funny)
Parent
Re:Got to wonder about other properties? (Score:4, Funny)
Sol: No, it's a moissanite.
Lincoln: A what?
Sol: A moissanite is an artificial diamond, Lincoln.
Sol: It's Mickey Mouse.
Spurious.
Not genuine.
And it's worth...
from "Snatch"
--
BMO
Parent