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I want to make a diamond at home using chemical vapor deposition (CVD).

  1. If I use a metal chamber filled with methane and hydrogen gas and heated with a microwave oven oscillator element, will the gas explode?

  2. What is the ratio of methane and hydrogen for the diamond to be able grow?

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    $\begingroup$ You can't do that at home. Think of something more realistic, like a nuclear reactor. $\endgroup$
    – Ivan Neretin
    Commented May 4, 2019 at 12:55

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The easiest way to grow diamond through chemical vapor deposition (CVD) is on a heated filament, which just takes a few watts.

You'd need a low-pressure chamber (~30 torr, or ~0.04 atm) with gas-tight fittings for electricity, feed-gas of ~1% $\ce{CH4}$ and ~99% $\ce{H2}$ and $\ce{Cu}$, $\ce{Ti}$, $\ce{W}$ or $\ce{Ta}$ filaments. Since this is a flow-though reactor, you'll also need to dispose of the flammable feed-gas without letting it accumulate near the vacuum pump.

N.B. This is not a simple project one could do at home, since you'd need vacuum equipment, pressure regulators, high-pressure bottles* of these highly flammable gases, and a vacuum-vessel which could implode. If you can get a knowledgeable instructor involved who has access to laboratory facilities and a thorough understanding of safety procedures, though, it's not impossible to accomplish.

* One of the greatest dangers would be a gas bottle falling, taking off like a rocket and leaving explosive gas in its wake!

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  • $\begingroup$ Logically for a 2 gram diamond I need the equivalent weight of carboon in the methane gas, theoretically I don't have to feed the gas constantly into the chamber, only to feed it once along with the hydrogen gas and let it react with the graphite seed, is this true? $\endgroup$
    – Oliver
    Commented May 5, 2019 at 16:25
  • $\begingroup$ Probably not true, because, apparently, the process requires a constant ratio of methane to hydrogen. Of course, this could be subject to experiment... $\endgroup$
    – DrMoishe Pippik
    Commented May 5, 2019 at 18:15
  • $\begingroup$ What is the purpose of hydrogen in the reaction, why can't I use only methane, or instead of methane only carbon dioxide witch doesn't explode, as far as I know real diamonds are made of CO2 $\endgroup$
    – Oliver
    Commented May 11, 2019 at 20:52
  • $\begingroup$ There are many allotropes of carbon, e.g. graphite and diamond. See en.wikipedia.org/wiki/Allotropes_of_carbon .Did the reference above give any information why H2 helps diamond form rather than something else? This may have been determined empirically or from some theoretical basis. $\endgroup$
    – DrMoishe Pippik
    Commented May 12, 2019 at 1:53

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