6 ms·

Porous, 3D forms of graphene can be 10 times as strong as steel but much lighter

78 points by mattiemass 10y ago

knicholes 10y ago
So this is just saying that the shape of a material determines its strength? From what I gathered from the video, they didn't actually use graphene in these objects. I was reading a introductory book on metallurgy over the holidays and realized that I had no idea what "stretching" was. I still hardly have any idea, but from what I was able to gather from the book, in steel at least, when stretched, there are these molecular "fault-lines" that can shift and still stay stable without actually breaking. Apparently, steel can be put under stress to fall to this final state to avoid further shifting during use in machines and whatnot. Maybe I'm completely missing the point and the plastic is somehow stronger than steel, but the quote >"You can replace the material itself with anything," MIT's head of Civil and Environmental Engineering said. "The geometry is the dominant factor." makes me think that this is the case?
- biot 10y ago
  Ironically, they could replace the graphene with steel and end up with steel being ten times stronger than steel.
- gene-h 10y ago
  What they are likely referring to here is strength to weight ratio. By more intelligently distributing material in space, one can get a higher strength to weight ratio than using solid material. Of course geometry does in fact influence material strength. One way geometry can influence material strength is by making crack propagation more difficult. In a simple plane sheet, a small crack at one end can easily propagate to the other end of the sheet resulting in failure. However, if we put a number of holes in our sheet, it becomes more difficult for the crack to propagate. A new crack has to be made each time the crack crosses one of the holes. Now this result of an additively gyroid structure having a high strength is a bit comical. One of the first 3d printing artists produced a sculpture of the gyroid a while back[0] and in fact the files for said sculpture are well known[1] and have been used to test 3d printers. It's sort of funny no one thought to crush one till now! [0]https://www.bathsheba.com/math/gyroid/ https://www.bathsheba.com/math/gyroid/ [1]https://www.bathsheba.com/downloads/ https://www.bathsheba.com/downloads/
- Chris2048 10y ago
  But the article says: > In its two-dimensional form, graphene is thought to be the strongest of all known materials Doesn't this imply it is stronger than steel in 2 dimensions?
  - knicholes 10y ago
    I think this implies that GRAPHENE is stronger than steel, but this 3d printed thermoplastic is definitely not stronger than steel given the same shape.
    - Chris2048 10y ago
      What I mean is "in 2 dimensions" may be relevant, since the shape seems to be a 2D sheet folded into 3D space.
varenc 10y ago
I don't know if the writer really understood what's going on there. Those models are just plastic. Understanding how to make strong shapes is useful for eventually building real structures with graphene in the future, but nothing about that research used graphene. I think they're saying that if that plastic model was graphene then it would be 5% as dense and 10x as strong as steel...but no such thing was actually created. The title here is pretty click baity.
- Breefield 10y ago
  Title is very click-bait. The MIT News article it links to is much more informative: http://news.mit.edu/2017/3-d-graphene-strongest-lightest-materials-0106 http://news.mit.edu/2017/3-d-graphene-strongest-lightest-mat...
  - gene-h 10y ago
    So they show that a graphene gyroid structure could be quite strong compressively. Now, the challenge is actually make such a structure. Making a template for graphene to grow on like this is bound to be quite challenging, minimizing the amount of defects in such structure even more so!
    - rsfern 10y ago
      They have a pretty plausible-sounding (I am not an aerogels expert) synthesis route based on cyclic annealing of graphene flakes, and they have molecular dynamics calculations to back it up. In the open access research paper [0] there's some discussion of the defects that form in the MD simulations, so that's baked into the mechanical property calculations to some extent... I agree that actually synthesizing this stuff still remains a big challenge, but at this point I think it's just engineering. [0] http://advances.sciencemag.org/content/3/1/e1601536.full http://advances.sciencemag.org/content/3/1/e1601536.full
    - ChuckMcM 10y ago
      Yes that was what I got out of it, and at the same time I am totally updating the Slicer infill pattern on my 3D printer to make stronger structures :-)
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zwieback 10y ago
Is it just me or are prestigious institutions such as MIT frittering away their respectability with press briefs such as this?
- B1FF_PSUVM 10y ago
  As long as the PR departments meet their assigned goals and earn their bonus, what's a bit of tarnish on the escutcheon?
- forgotpwagain 10y ago
  You should compare the actual university press release [0] to the article written by an external organization above. [0] http://news.mit.edu/2017/3-d-graphene-strongest-lightest-materials-0106 http://news.mit.edu/2017/3-d-graphene-strongest-lightest-mat...
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rsfern 10y ago
The original journal article is open access [0], and I think it's pretty well-written and accessible. This is a really great example of theory-driven materials design. [0]: http://advances.sciencemag.org/content/3/1/e1601536.full http://advances.sciencemag.org/content/3/1/e1601536.full
imaginenore 10y ago
Yes, yes, graphene is awesome, we know. Can you make cheap sheets of it?
hardwaresofton 10y ago
> MIT says that this is because the thinner walls allow the structure to deform gradually while the thicker one stores the deformation energy, which releases all at once I'm not sure that's the failure mode I want load-bearing things to have...
- dTal 10y ago
  It's a perfectly fine failure mode in applications where failure of any type is automatically catastrophic anyway - for instance, a submarine's pressure hull.
  - hardwaresofton 10y ago
    I don't know much about submarines, but I assume that you mean once the pressure hull is penetrated, the resulting pressure difference will quickly make short work of the hull. My point was that, if I could choose the failure mode, I wouldn't pick fail-all-at-once, if I could avoid it (for most things that bear load). If I could design/create a pressure hull that somehow didn't fail all at once, I think everyone would be happy?
    - Retric 10y ago
      If it was torpedoed a moderate diffence in hole size is not going to matter. A larger issue would be how flammable this stuff is.
tlb 10y ago
(ten times stronger than mild steel, at 2.7 GPa tensile yield.) Nobody is deciding between mild steel and graphene. Comparing to PAN carbon fiber (which can achieve 7.0 GPa yield with careful manufacture) would be more useful.
Pica_soO 10y ago
Imagine the burj al arab ten times higher.

78 points by mattiemass 10y ago

So this is just saying that the shape of a material determines its strength? From what I gathered from the video, they didn't actually use graphene in these objects. I was reading a introductory book on metallurgy over the holidays and realized that I had no idea what "stretching" was. I still hardly have any idea, but from what I was able to gather from the book, in steel at least, when stretched, there are these molecular "fault-lines" that can shift and still stay stable without actually breaking. Apparently, steel can be put under stress to fall to this final state to avoid further shifting during use in machines and whatnot. Maybe I'm completely missing the point and the plastic is somehow stronger than steel, but the quote >"You can replace the material itself with anything," MIT's head of Civil and Environmental Engineering said. "The geometry is the dominant factor." makes me think that this is the case?

biot 10y ago
Ironically, they could replace the graphene with steel and end up with steel being ten times stronger than steel.
gene-h 10y ago
What they are likely referring to here is strength to weight ratio. By more intelligently distributing material in space, one can get a higher strength to weight ratio than using solid material. Of course geometry does in fact influence material strength. One way geometry can influence material strength is by making crack propagation more difficult. In a simple plane sheet, a small crack at one end can easily propagate to the other end of the sheet resulting in failure. However, if we put a number of holes in our sheet, it becomes more difficult for the crack to propagate. A new crack has to be made each time the crack crosses one of the holes. Now this result of an additively gyroid structure having a high strength is a bit comical. One of the first 3d printing artists produced a sculpture of the gyroid a while back[0] and in fact the files for said sculpture are well known[1] and have been used to test 3d printers. It's sort of funny no one thought to crush one till now! [0]https://www.bathsheba.com/math/gyroid/ https://www.bathsheba.com/math/gyroid/ [1]https://www.bathsheba.com/downloads/ https://www.bathsheba.com/downloads/
Chris2048 10y ago
But the article says: > In its two-dimensional form, graphene is thought to be the strongest of all known materials Doesn't this imply it is stronger than steel in 2 dimensions?
- knicholes 10y ago
  I think this implies that GRAPHENE is stronger than steel, but this 3d printed thermoplastic is definitely not stronger than steel given the same shape.
  - Chris2048 10y ago
    What I mean is "in 2 dimensions" may be relevant, since the shape seems to be a 2D sheet folded into 3D space.

varenc 10y ago

I don't know if the writer really understood what's going on there. Those models are just plastic. Understanding how to make strong shapes is useful for eventually building real structures with graphene in the future, but nothing about that research used graphene. I think they're saying that if that plastic model was graphene then it would be 5% as dense and 10x as strong as steel...but no such thing was actually created. The title here is pretty click baity.

Breefield 10y ago
Title is very click-bait. The MIT News article it links to is much more informative: http://news.mit.edu/2017/3-d-graphene-strongest-lightest-materials-0106 http://news.mit.edu/2017/3-d-graphene-strongest-lightest-mat...
- gene-h 10y ago
  So they show that a graphene gyroid structure could be quite strong compressively. Now, the challenge is actually make such a structure. Making a template for graphene to grow on like this is bound to be quite challenging, minimizing the amount of defects in such structure even more so!
  - rsfern 10y ago
    They have a pretty plausible-sounding (I am not an aerogels expert) synthesis route based on cyclic annealing of graphene flakes, and they have molecular dynamics calculations to back it up. In the open access research paper [0] there's some discussion of the defects that form in the MD simulations, so that's baked into the mechanical property calculations to some extent... I agree that actually synthesizing this stuff still remains a big challenge, but at this point I think it's just engineering. [0] http://advances.sciencemag.org/content/3/1/e1601536.full http://advances.sciencemag.org/content/3/1/e1601536.full
  - ChuckMcM 10y ago
    Yes that was what I got out of it, and at the same time I am totally updating the Slicer infill pattern on my 3D printer to make stronger structures :-)

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deleted 10y ago

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zwieback 10y ago

Is it just me or are prestigious institutions such as MIT frittering away their respectability with press briefs such as this?

B1FF_PSUVM 10y ago
As long as the PR departments meet their assigned goals and earn their bonus, what's a bit of tarnish on the escutcheon?
forgotpwagain 10y ago
You should compare the actual university press release [0] to the article written by an external organization above. [0] http://news.mit.edu/2017/3-d-graphene-strongest-lightest-materials-0106 http://news.mit.edu/2017/3-d-graphene-strongest-lightest-mat...

deleted 10y ago

[deleted]

rsfern 10y ago

The original journal article is open access [0], and I think it's pretty well-written and accessible. This is a really great example of theory-driven materials design. [0]: http://advances.sciencemag.org/content/3/1/e1601536.full http://advances.sciencemag.org/content/3/1/e1601536.full

imaginenore 10y ago

Yes, yes, graphene is awesome, we know. Can you make cheap sheets of it?

hardwaresofton 10y ago

> MIT says that this is because the thinner walls allow the structure to deform gradually while the thicker one stores the deformation energy, which releases all at once I'm not sure that's the failure mode I want load-bearing things to have...

dTal 10y ago
It's a perfectly fine failure mode in applications where failure of any type is automatically catastrophic anyway - for instance, a submarine's pressure hull.
- hardwaresofton 10y ago
  I don't know much about submarines, but I assume that you mean once the pressure hull is penetrated, the resulting pressure difference will quickly make short work of the hull. My point was that, if I could choose the failure mode, I wouldn't pick fail-all-at-once, if I could avoid it (for most things that bear load). If I could design/create a pressure hull that somehow didn't fail all at once, I think everyone would be happy?
  - Retric 10y ago
    If it was torpedoed a moderate diffence in hole size is not going to matter. A larger issue would be how flammable this stuff is.

tlb 10y ago

(ten times stronger than mild steel, at 2.7 GPa tensile yield.) Nobody is deciding between mild steel and graphene. Comparing to PAN carbon fiber (which can achieve 7.0 GPa yield with careful manufacture) would be more useful.

Pica_soO 10y ago

Imagine the burj al arab ten times higher.