Synthetic Diamonds

PostBy Avi Paz Group At 07.11.2010

Once diamonds were discovered to be one of two forms of pure carbon in existence (the other being graphite), the idea of manufacturing synthetic diamonds captured the imagination of the scientific community. 

Beginning in the 19th century, a number of researchers claimed to have successfully produced diamonds. James Ballantyne Hannay and Ferdinand Henri Moissan, in 1879 and 1893 respectively, claimed to have manufactured synthetic diamonds through similar methods, both of which involved heating charcoal to 3500°C, with iron inside. The iron was then cooled by immersion, a process that supposedly provided the pressure necessary to produce diamonds. 

Sir Charles Algernon Parsons, who invented the steam turbine, invested 40 years of research in attempts to create diamonds, and in 1928 published an article saying that the endeavor was impossible. 

In 1941, General Electric launched a diamond synthesis project that was interrupted due to World War II. Work resumed in 1951, and in 1954 Tracy Hall of the Schenectady Group of scientists working on the GE project produced the first synthetic diamond using a belt press and published his results in the journal Nature. The largest of Hall's stones measured 0.15 mm in diameter, and his diamonds were too small and too flawed for use as gemstones, but suitable for industrial purposes. 

Independent of the GE project but nearly simultaneously, a top-secret diamond making project called QUINTUS was underway in Sweden, under the auspices of the country's ASEA company.  In 1953 the project successfully produced small synthetic diamonds that were not gem-quality. The work of the QUINTUS project wasn't reported until decades later. 

GE continued to work on synthetic diamonds and had a breakthrough in 1970, when it produced gem-quality diamond crystals. The first gem-quality synthetic diamonds were all yellow to brown in color due to nitrogen exposure. 

The prospect of gem-quality synthetic diamonds originally caused some consternation in the diamond industry, but it not proven cost-effective to produce them on a large scale. While the chemical properties of natural and synthetic diamonds are identical, the two types exhibit slightly different physical properties that can be detected using spectrometers and other equipment. At first, all of GE's synthetic diamonds showed strong yellow fluorescence under X-rays, a property that natural diamonds do not exhibit, with the exception of natural blue stones. 

The De Beers Diamond Research Lab has grown synthetic diamonds of up to 25 carats, but the process is expensive and to keep costs down most of its synthetic diamonds are cut off at 1 carat. 

Synthetic diamonds can have superior hardness, thermal conductivity and electron mobility to that of some natural diamonds, and are used as abrasives; for cutting and polishing tools; and electronic applications for synthetic diamonds are also being developed.