The hardest possible substance known to man?

[Gardamorg]

What could possible be the hardest strongest most durable substance?

[CraigD]

Gardamorg, you have edited your post to completely remove all of its original contents, which asked about the potential of osmium, the densest naturally occurring element, as a structural material, compared to carbon! Because changing posts in such a way can be confusing, please don’t do it in the future.

The following is my answer to your original post.

As best I can tell, unalloyed osmium is slightly less hard than typical metal alloys, such as steel, and much less hard and practically less strong than regular crystal materials, such as sapphire and diamond.

Before discussing this thread’s question, it’s important to understand the difference between hardness and strength. Hardness is, basically, a measure of what materials can scratch and cut others. Strength can be measured in many ways, such as shear strength, how difficult a material is to bend, tensile strength, how hard it is to pull a material apart, and compression strength, a measure of how hard a material is to compress.

Osmium hardness is 7.0 on the Mohs scale, a bit softer than most steel tools and machine parts, which have typical Mohs scale hardness of 7-8. The wikipedia article’s summary history of the use of osmium notes that it was at one time used for phonograph needles, before being replaced with much harder sapphire and diamond needles as techniques to make such needles became available.

Osmium has high shear strength, a shear modulus or 222 GPa, compared to 79 for steel and 478 for diamond.

Osmium has a very high compression strength, a bulk modulus likely between 395 and 462 GPa, possibly higher than diamond’s 442, (eg: Phys. Rev. B 70 (2004): Takemura Kenichi - Bulk modulus of osmium:...).

As far as making nanotubes or similar structures of osmium, I suspect there’d be a big problem, because it’s very chemically reactive, oxidizing very readily. I suspect that, like steel wool, fine osmium wire would burn. Oxidized into its most common form, Osmium tetroxide, it sublimates into a deadly poison gas (it’s name is literally latin for ). This reaction can be avoided is osmium is alloyed with other metals, or, of course, kept out of contact with oxygen.

Another drawback with large-scale use of osmium is that it’s fairly rare, and expensive, about US$100/g, or roughly 4 times as expensive as platinum.

In short, I think osmium is mostly good for what it’s currently used for, an ingredient in metal alloys, and a chemical used in synthesizing certain unusual compounds.

Originally Posted by Gardamorg

What could possible be the hardest strongest most durable substance?

Because strength and durability are not absolute qualities of materials, and, as noted above, are not synonyms, I don’t think this question can meaningfully be answered. Some materials are stronger and more durable in one application than ones that are stronger and more durable in another application. Some very strong materials are fragile, while some very durable materials are not very strong.

[Gardamorg]

Thank you.

But about diamond, the hardest substance on earth is inferior to high-strength steel alloys due to the fact diamond has shatterpoints all over it's structure. Diamond has weakspots that allow it to fracture easily despite it's strength. What I'm asking is if its posible to remove every single fracturepoint through some sort of molecular rearrangement? If so would this 'fractureless' diamond be superior to even high-strength alloys?

[Mercedes Benzene]

Originally Posted by Gardamorg

What I'm asking is if its posible to remove every single fracturepoint through some sort of molecular rearrangement? If so would this 'fractureless' diamond be superior to even high-strength alloys?

It's certainly possible to alter the molecular arrangement of carbon allotropes (just look at fullerenes!), however, it is diamond's structure that gives it its strength. If you altered its structure, it would no longer be diamond. It would be some other form of carbon.

Try googling "allotropes of carbon" or see Fullerene - Wikipedia, the free encyclopedia

[Gardamorg]

Originally Posted by Mercedes Benzene

It's certainly possible to alter the molecular arrangement of carbon allotropes (just look at fullerenes!), however, it is diamond's structure that gives it its strength. If you altered its structure, it would no longer be diamond. It would be some other form of carbon.

Try googling "allotropes of carbon" or see Fullerene - Wikipedia, the free encyclopedia

I don't understand, advanced calculus is easier than this.

[Mercedes Benzene]

Originally Posted by Gardamorg

I don't understand, advanced calculus is easier than this.

Which part don't you understand?

An allotrope exists when an element's atoms bond together differently. Carbon has many allotropes: diamond, amorphous (coal, soot, etc), graphite, and fullerenes.

Diamond is very strong, because the carbon atoms are locked together in a tetrahedral lattice.
Graphite is composed of hexagonal lattices which are layered on top of each other. That's why graphite is used in pencils. The latticed layers slide off very easily.
Fullerenes are highly variable, and can be specifically engineered by chemists.

In short, you can alter the way the carbon atoms are bonded together, but if the carbon atoms are not bonded to one another in a tetrahedral lattice, then it's not diamond.

Hope that helps!
Merc

[Gardamorg]

First thing I'd love to know is what the name of a material composed of carbon nanotubes is called.

All I hear is that carbon nanotubes are stronger than titanium and harder than diamond, but that's a comparison between the structure of a material and the material itself. I don't understand it at ALL!

[Gardamorg]

Originally Posted by Mercedes Benzene

Which part don't you understand?

An allotrope exists when an element's atoms bond together differently. Carbon has many allotropes: diamond, amorphous (coal, soot, etc), graphite, and fullerenes.

Diamond is very strong, because the carbon atoms are locked together in a tetrahedral lattice.
Graphite is composed of hexagonal lattices which are layered on top of each other. That's why graphite is used in pencils. The latticed layers slide off very easily.
Fullerenes are highly variable, and can be specifically engineered by chemists.

In short, you can alter the way the carbon atoms are bonded together, but if the carbon atoms are not bonded to one another in a tetrahedral lattice, then it's not diamond.

Hope that helps!
Merc

So are nanotubes superior to tehtrahedral lattices in all measurements of strength and hardness?

[Mercedes Benzene]

Originally Posted by Gardamorg

So are nanotubes superior to tehtrahedral lattices in all measurements of strength and hardness?

You can't really make a comparison like that. Carbon nanotubes are the "strongest" materials as far as tensile strength and elastic modulus go, but they're presently only used on a nano-scale. I would not call them "hard" like you would diamonds.

Do some investigation! You'll find a lot of information by googling or checking out a book from the library. Hell, go ahead and use wikipedia for some fast information. I'm sure there's a lot of information out there about the "strength" of fullerenes.

[Gardamorg]

Originally Posted by Mercedes Benzene

You can't really make a comparison like that. Carbon nanotubes are the "strongest" materials as far as tensile strength and elastic modulus go, but they're presently only used on a nano-scale. I would not call them "hard" like you would diamonds.

Do some investigation! You'll find a lot of information by googling or checking out a book from the library. Hell, go ahead and use wikipedia for some fast information. I'm sure there's a lot of information out there about the "strength" of fullerenes.

Thanks.