Super-hard metal 'four times tougher than titanium'
bbc.com
bbc.com
The actual paper (http://advances.sciencemag.org/content/2/7/e1600319.full) is much better and is free.
Hardness is a characteristic of a solid material expressing its resistance to permanent deformation. The Rockwell or Vickers hardness scales are most commonly used in the industrial blade industry.
Toughness on the other hand is the maximum amount of energy a material can absorb before fracturing, which is different than the amount of force that can be applied. Toughness tends to be small for brittle materials, because it is elastic and plastic deformations that allow materials to absorb large amounts of energy.
Elasticity is how much you can deform (stretch) an object, before the deformation is no longer reversible. Think of a rubber band, you can stretch it a little, and it returns to its original shape. Stretch it a lot, and it breaks down and does not return to its original shape.
Plasticity is how much you can deform an object before it breaks. This is the snapping point in the rubber band, where it completely breaks.
These two properties are different, and have to do with how the material is deforming on an atomic level. During elastic deformation, the individual bonds stretch. During plastic deformation, regions, layers, or fibers of the material slip. The relationship is best described by the stress-strain curve [1]. This plots deformation versus the pressure required.
Hardness and Toughness are the compression version of Elasticity and Plasticity.
These properties are often found experimentally, because they are a summation of many different atomic level interactions. Infact most materials are anisotropic, meaning if I measured the toughness of a material along two axises, I would get two different values.
[1] https://en.wikipedia.org/wiki/Stress%E2%80%93strain_curve
These both are completely false.
Elasticity is the idealistic property of a solid material to get back to it's original shape after a deformation force is retracted. (property of most solid metals where stress is much below the yield point)
Plasticity is the idealistic property of a solid material to stay in the deformed shape after a deformation force is retracted. (Plasticine)
"Plastic limit" is not a real term, but if it were, it might be a synonym for "ultimate tensile strength". There's also compressive strength and shear strength.
Edit: Sorry, not plastic. I meant rubber.
Since plastic can stretch a large amount before breaking it absorbs more energy than a (inverse of tough) object, so it is tough.
Since it is easy to stretch inelastically, it is not hard.
Usually anyway. IIRC, Acrylic is a plastic that shatters instead of deforming. But most plastics (ABS (aka Legos), polypropylene (PP, #5 Plastic), Pete (most bottles), HDPE (aka cutting boards)) all are "plastic", as in having high plasticity.
IIRC, metals are actually more "plastic" (deform more before breaking) than erm... plastics. See iPhone aluminum bending issue for details.
"Plastics" are mostly petrochemical derived organic polymers. Properties of some, like acrylic glazing are relatively hard and brittle, others quite elastic and soft, e.g., foam rubber. Obviously modern life is utterly dependent on these materials which are employed in virtually everything we use from food to space probes.
There are good reasons to believe that production of "plastics" is among the highest and best use of petroleum resources, it's a shame we continue burning it up at a prodigious rate. Trends to find alternative energy sources would have benefit in this respect too.
The first were based on coal tar, starting around 1870-1880 IIRC. Then came bakelite, still used in cookware handles -- it has exceptionally good thermal resistance properties.
Discovery accelerated through the 1900s, 1910s, and 1920s, and exploded in the 1930s, with the number of materials about doubling IIRC.
Names started changing too -- from chemical (polypropelene, polyester, polystyrene) to brand (nylon, teflon, orlon).
I've also noted that with both coal and oil, there seems to have been an adoption and technological development cycle in which the first use was to burn the materials, and only later, by some decades, did the chemistry develop for materials based on the substrates. There's probably a lesson here.
Check this out for a quick comparaison about toughness: elongation of polymers is pretty easy. http://images.slideplayer.com/32/9819762/slides/slide_7.jpg
For more info: https://en.wikipedia.org/wiki/List_of_materials_properties#M...
I misspoke earlier when I said force. I was inadvertently sloppy in my writing.
Link to PDF of paper http://advances.sciencemag.org/content/advances/2/7/e1600319...
this is really amazing to me! you put metallic, designed-to-last object inside an organic blend of tissue and bone and human activity and in 10 years its worn out. So much opportunity in the area!
Along the same lines, interesting how delicate our bodies are in the short term but rather durable in the long term.
unreliable narrator
I think there was a darpa paper about surrounding bones with carbon nano tube meshes that would renforce them, prevent or reduce shattering and could be used as an internal cast with minimal fixture but I hope we never get to that point.
Speaking about that mentality > the right to repair : https://news.ycombinator.com/item?id=12088631
...raises the question about who can service and repair medical implants. I imagine pace makers would be an interesting case study.
http://mobile.nytimes.com/2016/03/21/us/artificial-hearts-ti...
Maybe it was just a trial I saw to see if it worked or maybe it can only be used for small patches not entire sections of bone like a femur or hip joint.
I was astounded to learn about the composite materials being developed for cheap 3d printers - see http://colorfabb.com/ and https://ninjatek.com/products/filaments/ninjaflex/
It isn't that you might be a different physical person after 7 years, but a different person based on the current context!
There was a great invisibilia podcast on the subject : http://www.npr.org/programs/invisibilia/482836315/the-person...
See also (referenced in podcast) : http://www.columbia.edu/cu/psychology/indiv_pages/mischel/Wa...
I've done a little work in prosthetic materials. It's amazingly complicated. There are metals, plastics, and ceramics as basic options. There is every combination of one of those running against the other in hip implants. There's at least a half-dozen variants within each of the three materials classes. Typical materials are CoCr (metal), Al2O3 or ZrO2 (ceramics) and radiation cross-linked ultra high molecular weight polyethylene (UHMWPE plastic).
Prosthetic lifetime gets more and more important as the population of recipients gets younger. They're more athletic, put more load on their implants and they're going to use them longer than the earlier, older recipient population.
Yes, serious opportunity here. I hope implants are a once in a lifetime procedure if I ever need them.
How good are we at concentration gradients in alloys? For a replacement joint, say, could the part that the bone bonds to be mostly titanium, and then the bearing portion be this new alloy?
Still have to think about other measures of strength and the processes required to make parts out of it.
More: The paper mentions bonding the material to the surface of ceramic materials to save weight.
Mayo clinic has a good overview and timeline regarding the discovery process for cobalt-chromium, which was previously thought to be a good all-around implant material:
This has just raised what you can afford when you're paying with an arm and a leg.
No doubt there would be metallurgical issues with this.
Funnily I had a pre-student job in a coatings company using detonation guns to fire tungsten carbide into metals in order to make them tougher. Could a similar treatment be used for Titanium hip replacements?
Seriously, science journalism is almost uniformly horrible (as is just about every other type of journalism -- google "Gell-Mann Amnesia Effect").
I feel like most of the issue comes when journalists comment or repurpose journal articles. What seems to get dropped is the background, the context, and the limitations that are often expressed in a nuanced language. In the end, as a scientist, I blame scientists...you created the knowledge, try and take some ownership of it (having been in the situation myself).
I have no idea how toxic tungsten is, buy hey, it's Wolverine, right?
The phase diagram posted in another comment shows that the region in which this particular phase exist is fairly small. Additionally the paper mentions that they had to add a few trace alloying components to stabilize it in that phase. I.e. it takes some effort to get to the point.
And even if you can spot a trend by lining up properties of various alloys on the right diagram, investigating that trend may be out of scope for the research you're currently doing.
(...and jewelry)
This is why you're being downvoted. Check Wikipedia before commenting next time.
Cupellation plus touchstones are adequate both to refine electrum and to destructively measure the quantity of gold in the electrum. By Roman times, we were smelting electrum with salt to separate out the gold by chloriding the silver, and the Lydians may have been doing that already by the fifth century BCE, when they started debasing their electrum coins with extra silver.
This sounds kind of stupid, since at this point we're used to being able to purify and quantify all kinds of materials, but in fact these attributes made gold and silver unique among rare elements for centuries.
If you want something tough that can absorb surprising amounts of energy without breaking there are exotic nickel steels that require exotic heat treatment, or maybe some of the military armor plates from the old days (before HEAT rounds forced other criteria as a figure of merit). Maybe a chunk of battleship armor plate or maybe the crankshaft from an old diesel ship engine.
If you want something hard there are some oxidized titanium coatings that are somewhat hard and industrially useful but nothing unusual or worth writing home about. Besides that's cheating because its a titanium containing compound, kinda like saying coal cures scurvy because vit C is merely a peculiar arrangement of carbon atoms much like coal. Industrial diamonds are not going to be replaced by titanium rod anytime soon...