Man Made Diamonds
Ever wonder how Man Made Diamonds are created?
Currently, there are two main technologies whose function is to create diamonds.
The high pressure, high temperature process simulates conditions found deep within the earth, where diamonds appear naturally. A belt press was the very first successful design. This design has two anvils that press together which enable it to grow many diamonds in 1 cycle. These presses are mostly used for industrial diamonds and powder. A cubic press uses six different anvils pressing onto a cube. These presses are most commonly used to produce industrial diamond powder. The BARS press was created by Russian scientists. It uses 6 inner anvils and eight spherical outer anvils to apply hydraulic pressure to the growth cell. One cycle of the BARS machine makes one diamond crystal. These BARS presses are to-date, the best process for growing comparatively large gem-quality diamonds.
At the core of the HPHT machines you will find a growth cell. This cell contains all the elements and materials necessary to grow the diamond. This includes a small diamond seed, highly refined and purified graphite (carbon) along with a catalyst of mixed metals and powders that facilitates the diamond growth. The growth cell is placed in the center of the machine and is heated to over 1,300 degrees Celsius and over 50,000 atmospheres of pressure is applied. As the temperature and pressure increases, the catalyst turns into a molten metal solution. Once the best conditions are reached, the graphite dissolves into this solution. Through a controlled cooling process over the course of many days, the carbon atoms slowly build upon the crystal structure of the diamond seed. The diamond normally grows in a truncated octahedron or a hexa-cubic shape, depending on parameters of the growth process. Once the machine runs its full cycle, the growth cell is removed. The new diamond is cleaned and ready to be cut and polished, exactly like every other rough diamond. Throughout the growth, the temperature and pressure need to be maintained within an extremely strict set of parameters. If there is any fluctuation, the diamond can either stop growing, or become so heavily included, the usable gem-quality size can be quite limited.
Different colored diamonds grow at different rates, which can be why the size availability varies based on the color.
Chemical vapor deposition is a very different process from high pressure, high temperature, though they both ultimately grow diamonds. The environment inside a CVD machine is a tiny fraction of 1 atmosphere of pressure. Carbon-based gasses, commonly methane, are added to the environment and are heated to many 100's of degrees Celsius which will cause the gasses to break apart and release their carbon atoms. The carbon then "rains" down onto a diamond substrate, which is where it slowly grows in layers (a couple of micrometers per hour) as a crystal. This technology is best suited for applications utilizing thin layers of diamonds, such as optics and semiconductors. CVD is capable of producing gem-quality diamonds, though the dimensions of the polished diamond is limited by the thickness of the diamond wafer.
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