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Author: Subject: in which way could diamond powder/dust be turned solid
Melgar
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[*] posted on 17-8-2017 at 22:58


Quote: Originally posted by j_sum1  
If you are going to sinter diamond particles then you have an alignment problem. You might get a cohesive mass (if you are clever) but you won't get a single crystal unless you are above recrystallisation temperature for long enough time. IOW, diamond dust is going to be a poor starting material if you want large diamonds.

Actually... if growing diamonds via CVD, you do need diamond seed crystals, and dust can be used for this purpose. CVD takes place at low pressures, and moderate temperatures, at least for the solid diamond.




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[*] posted on 17-8-2017 at 23:23


Wait, i just realized that the process that the carnegie institute uses is just the CVD process.
So then the CVD grown diamonds are in fact genuine diamonds, in that the bonds have been formed.

I guess this means diamonds in the near future are gonna begin to be almost worthless (hyperbolically talking).
Possibly worth less than platinum group metals and also gold.
Rightfully so if you ask me. :D
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MrHomeScientist
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[*] posted on 18-8-2017 at 06:36


They already are worthless; the diamond cartels create artificial scarcity to drive up prices. There's vaults full of diamonds, and they release small amounts at a time to keep up demand. Buy moissanite instead!
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Melgar
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[*] posted on 18-8-2017 at 12:56


Quote: Originally posted by MrHomeScientist  
They already are worthless; the diamond cartels create artificial scarcity to drive up prices. There's vaults full of diamonds, and they release small amounts at a time to keep up demand. Buy moissanite instead!

If you think diamonds are a scam, "moissanite" ie, "optical-grade silicon carbide cut into gemstone shapes" is even worse. Typical markup on a diamond is 10-25%. Typical markup on "moissanite" is something like 500%.

The artificial scarcity thing was true for a while in the 1990s, but isn't true anymore. What happened was that De Beers inadvertently created huge incentives for "blood diamond" mining, then had to reverse course due to extremely bad PR. They went from controlling about 90% of the world's diamond supplies to about a third. De Beers is actually the good guy now, believe it or not, and pays for medicine and education and such in countries like Namibia and Botswana.
Quote: Originally posted by Assured Fish  
Wait, i just realized that the process that the carnegie institute uses is just the CVD process.
So then the CVD grown diamonds are in fact genuine diamonds, in that the bonds have been formed.

I guess this means diamonds in the near future are gonna begin to be almost worthless (hyperbolically talking).
Possibly worth less than platinum group metals and also gold.
Rightfully so if you ask me. :D

Eh, CVD is only more economical than mining diamonds for diamonds under 1 carat or so. As the surface area to volume ratio decreases, the process becomes slower and slower, and it's already really slow and energy intensive.

They also have a certification process for diamonds that can detect CVD and "enhanced" diamonds (where they take yellowish-brown diamonds and treat them to make them a nicer color) and anyone who buys diamonds makes sure the certificates are in order already. I don't foresee the market for natural diamonds ever going away, especially considering the demand in Asia, but consider how many cool new technologies are becoming available for sale lately, and diamonds hardly seem worth their steep price.




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clearly_not_atara
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[*] posted on 18-8-2017 at 14:24


I think the real "killer app" for CVD diamond is using diamond as a coating for other less durable gemstones. Opal is much prettier than diamond, but if you wear them every day they'll get dull and scratched. But diamond-coated opal could really last a lifetime.

As for ultrahard clear stones to be worn as status symbols, go for the meteoric minerals like stishovite. That's a cool story IMO. "Hey I got you this space crystal".
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[*] posted on 20-8-2017 at 05:52


The trouble with applying diamond as a coating is that its crystal structure is totally different from most minerals, which are oxides. It's actually a crystal held together with covalent bonds, which AFAIK is something that only occurs in carbon and silicon, and possibly germanium (which is practically a metal, in any case). Alumina / corundum / ruby / sapphire is hard enough for all practical purposes, much easier to synthesize, is an oxide like virtually every other gemstone, and is the reason that we can build things out of aluminum without them undergoing magnesium-like reactions when they catch on fire.

Most stishovite isn't actually from asteroids or meteors, it's obtained from ordinary quartz, by dissolving the quartz away with hydrofluoric acid. It actually forms under similar conditions as diamonds do, and is found in kimberlite pipes like diamonds are.

Meteoric iron fragments are pretty cheap though. There was this huge iron meteor that exploded over China hundreds of years ago. I guess there aren't too many employment opportunities in that part of the country because people use metal detectors to find the fragments, and they turn up on eBay all the time for really cheap.




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