TechZones >> History of Man Made Diamond >> How To Make Synthetic Diamond

There are two main methods - "high pressure, high temperature" (HPHT and also called BARS method), or you can go "ultra low pressure, high temperature (also known as CVD).

The HPHT method is the one used by almost all synthetic diamond producers today (both for gem use and industrial use). This process tries to mimic how diamonds are grown under the earth, and uses a diamond seed which serves as the growth template, and then a carbon source and catalysts are added to help it grow.

Once you have a finished crystal, you cut off the original 'seed' diamond, and you are left with a nice lab grown diamond.

CVD is currently mostly used for coating things with diamond, as there are still a lot of challenges to actually grow a larger single diamond with this method. It also uses a diamond seed, but the carbon is supplied by gas that is then molecularly shredded, and the carbon then 'rains' down onto the diamond seed below and grows.

Note that most synthetic diamonds currently being made are also yellow, blue or pink, not white diamonds. There are some fundamental difficulties in growing whites, which I won't detail at this point.

Graphite convert to diamond under high pressure and temperature.

 

PRINCIPLES OF SYNTHESIS

                     

Diamond synthesis using the belt between jaws of a hydraulic press.

Workshop of diamond synthesis

                                   Phase diagram of carbon.

Diamond synthesis can be achieved by following methods.

  1. High pressure:
    • Static pressure
    • Dynamic pressure
  2. Low pressure:
    • CVD
    • PVD