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This is a question that naggers me sometimes.  It's about diamonds.  Ever since I heard about Neil Stephenson's book "The diamond age" (Haven't read it yet, though), I keep wondering why we are not capable of making diamonds in a industrial way.

Some methods for making diamonds exist already.  Check out wikipedia if you don't know about them.

So why is the biggest known diamond on earth still a natural one??  What's so hard?

Also:  what about using a brute force method?   I mean, a diamond is made from carbon with pressures around 6GPa.  Fine, can't this be done without using explosives or stuff like that?  I mean, with a purely mechanical device?

6 GPa.  That's 6 GigaNewton per square meter.  That's about 600e6 kg weighting on the same surface.  That's 600 Kt  (Kilo metric ton).   One ton is a cubic meter of water.    So 6 GPa is the pressure at the bottom of a 600 kilometers deep ocean.  That's deep.

But I don't need a 1 meter-sized diamond.  I'd be happy with a 10cm one or so.  That's one hundred times smaller a surface than a square meter.  So I just need a 6 Km deep ocean, providing that I can manage to have a one square meter water column weight on a square decimeter one.

Hell I can reduce the height of the thing by an hundred factor if I use a wilder column.  So, a ten-meter per ten-meter section column need to be 6 Km / 100 = 60m height.

So here is my question:  isn't it possible to build a 10m x 10m x 60m pool (or a 11.27m radius spherical water tank) and have it weight on a 10cm x 10cm area?

I don't think anyone tried. There are no industrial applications to use big diamonds for that I'm aware of.

Synthetic diamonds can be manufactured using the HPHT  (High Pressure High Temperature process):
http://en.wikipedia.org/wiki/HPHT_diamond#High_pressure.2C_high_temperature

Because of the surface to volume ratio the HPHT presses don't scale well with size. Eventually the cost of the press will be more then the cost of the diamond produced.

The "Diamonds" in The Diamond Age are more in the realm of carbon quasi-crystals. The way to go there is research into grapheme and nano-tubes, a much more interesting concept. ;)
From what I can tell, the difficulty is heat or the right amount of heat and pressure to enable the self-assimilation process of molecular structures.

Anyway I think we are far away from ever building a matter compiler, at least if the current scientific consensus in physics remains the way it is.

If you just wanna produce diamonds, there is no real limit to it's size except building a sufficiently large pressure chamber which is expensive to make (failure rate goes up the larger you make it)

Solved!: https://bitcointalk.org/index.php?topic=124443.0

And it is kind of like the question about why doesn't someone do a 51% attack to double spend bitcoins?   Because once you do that, the coins you got from double spending are no longer worth anything because you just destroyed the entire reason they had value.

Diamonds don't have value just because they are scarce.

Imagine you actually could make some as big as you want, and at will.  Would you refrain yourself from doing it?  I bet you wouldn't.  You'd make some because diamonds are cool and pretty.

Humans love to make things, regardless of whether it has value or not (http://www.youtube.com/watch?v=Z86V_ICUCD4).  It just has to be fun, cool, or beautiful.  And because sometimes the value is not in the product, it's in the act of making it.

If someone could figure out a way of making a car-sized diamond, I'm pretty sure someone would actually do it.

This is not quite how pressure works. No matter how thin/thick your column is, the pressure at its bottom is still just a function of the height.

The whole large column rests on a single very tight rod, with a 10cm x 10cm section.


Like this:
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|                                |
|________    ________|
               |  |              
               |_|

But of course with a better shape (this one can't obviously support the weight)

That's still not how pressure works. The water underneath the plate supports the plate as well. Your diamond would have the same pressure as if it were just sitting under 60m of water. Now, if you made a 10mx10mx60m container of water like you described on the surface, you could get those kinds of pressures.

Question: What material will you use for your anvil that will allow you to compress carbon to those pressures without deforming?

There is no water under the plate.  What I drew on the lower part is the steal rod.  But I guess I should have drawn this:

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|                                |
|__________________|
               |  |              
               |_|

Notice the separation.

So this structure is suspended in air?

No.  It rests on the rod.


Possibly inside a fixed structure that limits its motion to a vertical movement, though.

It rests on the rod, but is this basically a huge cup filled with water on the surface, all surrounded by air, or is the entire thing underwater?

Do you realize that pressure depends only on the height of the water column right? Making it wider doesn't change anything

Yes I do.  Please stop now.  I just use water to have a cheap large amount of mass.   Replace it in your mind by sand or stone bricks if you want.

Then why use

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|__________________|
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               |_|

if


is the same?

Because it is not the same.  In the first example all the water mass rests on the rod, and there is much more water mass.

We're just not talking about the same mechanical structure.  I'm talking about a rigid tank resting on a narrow rod.  You seem to be willing to talk about pressure on the bottom of a deep pool.

It's just a water tank.

Yes, then that should work. Out of curiosity, what materials will you build your 4"x4" rod out of that will support having 600,000,000kg on top of it?

Oh understood  :)

Well, I know pretty much nothing about resistance of materials.  But I have many difficulties to imagine that a steel rod would be the first thing to break.  After all, isn't steel stronger than graphite?  So in my mind the graphite would turn into diamond first and then shit would happen.

Or maybe we could use tungsten.  I don't know.  I really would like to simulate it, but I'm no mechanical engineer.

Yes well, now you're starting to grasp the problem. Neither tungsten nor steel have a durity of 10. This means they don't work in this application.

Realistically this is what would happen:

|                                    |
|                 _                 |
|              /| | \              |
|________/ |_|  \________|             
               

The huge steel block you put on the carbon would simply deform under the 600,000,000kg pressure.
What you will get is carbon pressed into your steel block. Which actually is a really interesting material, but not diamond.

If you would make the top of the press a water tank and fill it with water the rod below it will simply puncture the tank and the water will flow out.

It's not worth it to make artificial diamonds (in any quantity). As soon as you do, the perceived value disappears.

Diamonds are basically cheap rocks that have had their value inflated using artificial scarcity and by clever marketing. Last I heard, there is more than a three year supply on hand. Industrially, only tiny diamonds are typically needed and there's more than enough of those to go around (and at that size, they're reasonably easy to make artificially in any case).

With that said, large artificial diamonds are very much around the corner and the dug-from-dirt suppliers are about crapping themselves. They are already starting talk of the natural ones being more attractive due to natural inclusions (something which has detracted from value in the past but artificial diamonds tend to be "perfect") and plans are afoot (if not in place already) to start tagging natural diamonds with serial numbers using lasers to preserve the "exclusiveness".

Diamonds are a terrible buy. Take one to a jeweler and they'll typically offer less than half what you paid. I've told my wife that she can never expect one from me. There are more attractive jewels anyway.

Yeah I mentioned already that the tank (or a structure below that supports it) would need a better shape than just a flat surface. Like a V-shape or something:

http://www.icecreamnmore.com/choco_ice_cream_cone[1].jpg

It all boils down to opportunity cost. MAYBE someone could make a car sized diamond with a total of X hours of extended work effort and the cost of Y resources.
The question is this: Are X hours of effort and Y resources really the best spent on making a car sized diamond?
Or should we rather spend the X hours and Y resources on curing cancer? Or making a super weapon to rule the world? Or make cars that run without fossil fuels?

Just because it can be done does not mean it will be done. It will be done when someone in control of the required effort, skills and resources thinks its the best way to spend the effort necessary to do so.

You're too squared.   People don't think like that.   The notions of "Fun" and "Cool" don't fit in your economics views.

I've shown you a useless machine already.  Here is the world record for falling dominos:

http://www.youtube.com/watch?v=9E7Ep3U06Nc

Why did all these people spend so much time preparing those dominoes instead of searching a cure to cancer?  I don't know, but they did anyway.

I have very little doubt that if it was possible to make a car-sized diamond, someone would make one, regardless on whether it would cost more or less than the market price of the actual thing.

Because it is insanely more simple to put dominoes in place rather then cure cancer. With enough fools who have enough time on their hands you can build incredibly large dominoes. A few hundred fools with several months to spare still won't cure cancer, put a man on the moon or make a non-fossil powered automobile.

Notice than you're the one who talked about curing cancer.

Anyway, my point of this thread was that to me, making a big diamond at least looks simple.   Just like falling dominoes:  you just need a lot of dominoes.  It seems to me that to make diamonds, you just need a lot of water and steel.

I know this is an old thread, but I saw this and it reminded me of this thread. 
http://en.wikipedia.org/wiki/File:Carbon_basic_phase_diagram.png

From this you can see that creating diamonds needs a presure of about 70 to 700Gpa. Doesnt sound much does it ?

Let me put that into everyday units for you:

70Gpa is about 700,000 atmospheres, or about  10,152,641 psi. Wow!!
Oh yes, you also need a temperature of at least 4500K.  Kelvin, Celsius, who even cares at these temperatures?

For reference, (rough figures.)

  Melting point of Iron: 1800K.
  Melting point of Tungsten: 3700K
  Melting point of
      Tantalum Carbide, TaC, an
      ultra high melting point
      ceramic, reckoned to have
      highest melting point of anything: 4250K

Even measuring such high temperatures is not simple, remember your common or garden platinum thermometer would melt!!
(Oh, yes Platinum melts at about 2000K)

Oh, and bear in mind that graphite starts to burn at about 1050K in anything similar to air.

Of course many tricks can be used to confine something hot within something that is cooler, look at a microwave, the inside is not as hot as the food in it,
but that in essence is why it is so hard to make diamonds at all.

Big diamonds? Well, thats just a little harder....

See also:
www.electrochem.org/dl/interface/wtr/wtr07/wtr07_p30-36.pdf

Diamonds.  :D

Then don't heat the metal parts.  Only heat the graphite target at its center, somehow.  It would melt if it has to melt.

You don't really have to measure temperature if you really can't.  You can infer the temperature from the physical model and the amount of energy you put into the system.


Duh.  At this point doing everything in an inert gaz is a minor issue.


Yes, microwaves or any concentrated radiation are a possibility.  I don't know, I was thinking about ultrasounds or something.  Anyway I'm pretty sure there are lots of ways to heat a localized point inside a big chunk of graphite.

I'm not saying in this thread that making diamonds should be easy, so please don't be a smart ass.  I'm saying that I'm surprised and kind of disappointed that not much efforts seems to be put into it, when compared to other stuff.   There are also things I don't know about the issues, so I asked in the hope that I could learn stuff.  In particular, I have no idea about how metals behave under very very large pressure.  Assuming they don't heat enough to melt, what can happen?  Do they shatter like glass or something?

Why would anyone put effort into this, when you can just take a bunch of starving people and work them in mines until they're kaput, then discard of them?

Because natural diamonds are small.   I want to see a sky-crapper made of large single crystal diamond parts.

Just use this natural diamond.

http://www.telegraph.co.uk/science/space/8722757/Astronomers-discover-diamond-like-planet-in-the-sky.html

Why do you want a big diamond?  The only reason I can think of is that you're a total fucking idiot. 

Or that you want to sell it to other idiots, which is basically just as bad. 

Large synthetic diamonds are already made.  People using the CVD have made diamonds up to 34 carats and there's no real limit to the size beyond how much patience you have.

Though I'm not sure De Beers et al are hugely concerned about artificial diamonds stealing their thunder in jewelry.  They've been around for so long and have managed to infiltrate so much of their marketing schemes into general culture that unseating them would be exceedingly difficult.

Then you're going the wrong direction. You're thinking big when you should be thinking small. If you want house-sized artificial diamonds, like in Diamond Age, then you'll have to do it the way they did... nanites. The only practical way to manufacture a diamond larger than the head of a pin is to assemble it molecule by molecule.

What about hot glue and velcro?