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According to this paper if diamonds are doped with some boron and nitrogen it will gain enormous toughness while retaining the superhardness characteristic of diamonds.

This diamonds reach toughness of 34 MPa√m !! This value is about 10 times tougher than most ceramics and approaching the realm of aluminum alloys.

Assuming we are able to produce such diamonds in the bulk with low cost , how would these diamonds perform as an armor ?

How would this material be in comparison to armor steels like AR500 & AR600 agains armor-piercing bullets ?

Note: this not duplicate , old questions did not mentioned super tough diamonds.

Johnny
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    What sort of Ceramics and Aluminium alloys are you talking about? A quick google suggest AR500 has a yield strength of 1300MPa which is way higher than your little diamonds. Please also note that hardness (indentation and scratch resistance) isn't as important as how brittle the material is (how easily it shatters). – Shadowzee Mar 20 '19 at 05:14
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    you didn’t even know the difference between fracture toughness and tensile strength . – Johnny Mar 20 '19 at 05:57
  • some grades of tungsten carbide have a tensile strength of 2500 MPa yet they are they are more brittle compared to steel.

    natural diamonds have a values up to 7500 MPa , 5 times that of AR500 steel .

    diamond micro-needles have a tensile strength up to 100,000 MPa with 9% elastic strain , while diamond micropillars have a compressive strength up to 250,000 MPa with up to 18% strain !! that is two orders of magnitude higher than your tiny steel .

     – Johnny Mar 20 '19 at 06:06
  • Not an answer hence a comment but I'd just apply diamond dust to the surface of a metal armor. Less diamond needed and smaller crystals are cheaper. And looks pretty which matters. Should also be more resistant to shattering but the main thing is that when they shatter they absorb energy but the area of armor that loses its diamond coating should be minimal. You can also make a real composite by putting small diamonds inside the steel. Some modern armor include "nanoceramics" which would presumably be close enough to be replaced with diamonds of the same size. – Ville Niemi Mar 20 '19 at 06:33
  • Given that the toughness ranges from 22Mpa to 34Mpa, it is still less than that of Steel 50Mpa which makes steel better at absorbing energy. If you are really adamant on using diamond then you can still do it. After all you removed the biggest restriction which is bulk production and cost. Also apologize for mixing up toughness and tensile strength. – Shadowzee Mar 20 '19 at 06:39
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    Why compare ceramic armor to steel? Steel can stop bullets indefinietly, ceramics get weaker with each shot. – Mephistopheles Mar 20 '19 at 06:54
  • A key feature of body armor is that the top layer has a high hardness. This usually decreases toughness and increases shattering possibility but that is pretty much what you want for bodyarmor as this spreads the force more. I'm not sure if higher toughness with the same hardness would be beneficial for the top layer... But for the bottom layer of bodyarmor it would be perfect. The bottom layer needs to be tough so it can catch the shrapnel from a shattered top. The only thing we need to know now: How much does this Diamond alloy weigh? If it weighs more than a few slabs of ceramic... – Demigan Mar 20 '19 at 09:19
  • This seems to be a real world Engineering question and probably ought to be asked on the Engineering SE forum or somewhere similar (perhaps a military tech forum somewhere). Note that even with the science-based tag answers on WB SE don't have to be more than plausible and from your comments I think you're looking for something more rigorous than WB SE would normally do. – StephenG - Help Ukraine Mar 20 '19 at 15:23
  • A big caveat in this study is "single-crystal diamond". Thin diamond cover won't help that much because the inner layer of the armor would still receive the most of the impact force. – Alexander Mar 20 '19 at 17:02
  • Are you inquiring about body armor, which needs flexibility but does not have a solid structural back, or armor plating for shields, vehicles, buildings, and such, which can have structural rigidity and shock absorption behind it? – Justin Thyme Mar 20 '19 at 18:07
  • Some tank armor is deliberately brittle, so the energy is absorbed and released in the structural breaking of the bonds. They have to be replaced after every use, but they are very effective against single-occurrence explosions (IED and such). – Justin Thyme Mar 20 '19 at 18:10

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There is a big difference between hardness and toughness, diamond is really hard(scratch resistant) and not that tough (blunt impact resistant), if you take an ordinary hammer and hit a diamond it will shatter. Also hardness means it's brittle so would break very easily, in things like sword and armors we need something that will vibrate and dissipate the impact, that would be true both in armors and in weapons. If you make it super duper tough it's not a "diamond" anymore, than yes it would work wonders as an armor.

GaboSampaio
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