A Little Lab-Grown Diamond History
If you only learned about diamonds in the past decade, you may be interested to know that Henry Moissan first experimented with making diamonds in his laboratory in the 1890s. He theorized that he could create diamonds by crystallizing carbon under high pressure from molten iron.
To test his theory, he designed and made a special use electric-arc furnace that could achieve temperatures of up to 3,500c and he was ultimately able to produce tiny artificial diamonds.
Nearly 40 years later, several groups around the world were engaged in hush-hush development efforts to create diamond material. General Electric (GE) in particular began research in the late 1930s, but paused their efforts during the second world war.
At that time, the interest in growing diamonds in a laboratory was not for gem or jewelry purposes. Because of the hardness of diamond, it had many important potential industrial uses, from cutting tools to protective coatings.
After WWII, a GE chemist named Tracy Hall invented a belt press, which made a repeatable method of diamond production possible. By 1956 GE had managed to grow diamonds in batches using high pressure and temperature (HPHT). These diamonds were extremly small and very dull. But it was a beginning!
HPHT growth immitates the way a diamond is formed in the ground, andbetween the 1950s and the 1980s the race was on to develop increasingly high quality diamond material using this method.
But another method for growing diamonds was also under development. In 1954 a patent was filed to grow diamonds using chemical vapor deposition (CVD). This method was met with skepticism — even derision — by the scientific community, and it wasn't until the late 1980s that diamonds could be reliably reproduced using this method.
Unlike HPHT, which mimics the way diamonds are formed in nature, CVD produces diamonds by mixing hydrocarbon gasses and hydrogen in a vaccuum chamber at very low pressures.
The reason it took so long to produce diamonds using this method is that under typical circumstances, that mix of gasses and hydrogen would produce graphite and other non-diamond forms of carbon. But when microwave energy, electric energy, or high temperature filaments are introduced, some of the hydrogen is converted to atomic hydrogen, and that in turn promotes diamond formation.
Both the HPHT and CVD processes begin with a diamond seed, which is a very small, flat wafer of diamond. These seeds can be from mined diamond, or they can come from a previously grown HPHT or CVD diamond.
In the CVD method, the seed is bathed in the activated carbon-hydrogen envrironment, and the gasses travel across the seed, attaching to available carbon atoms and repeating over and over again, growing the diamond one atom at a time.
In the HPHT method, as the diamond seed is exposed to intense pressure and heat, the carbon melts and begins to form around the seed.
