Man Made Diamond Types by James Chartwell

Man Made Diamond Types by James Chartwell
Long craved for their brilliance and luster, diamonds are also desirable for use in science and technology. Their expense and rarity, however, have limited their availability. As a result, scientists have spent the last hundred years trying to mass produce man made diamonds in the laboratory. Dr. Moissan kicked off the trend back in 1893, when he discovered tiny diamonds in a crater in Arizona and attempted to replicate them. Those "diamonds" were actually silicon carbide (SiC) and are now classified as Moissanite, diamond simulants. Others attempted to synthesize diamonds, and only recently succeeded in growing a colorless, pure gemstone quality crystal. These diamond imitations are available in several different forms, classified according to their structure and method of growth.
The definition of a man made diamond is straightforward. It's a stone with the same characteristics as a naturally occurring diamond, right down to the atom. As mentioned above, diamond simulants like Moissanite are actually made from other material and look like diamonds. One of the most popular and widely known man made diamonds is the simulant commonly known as cubic zirconia. Composed of zirconium oxide (ZrO2), cubic zirconia has been around since the 1970s.
The classification of man made diamonds types is only done to those crystals that are everything diamond-like. Four categories of man made or synthetic diamonds exist: HPHT grit; HPHT large single crystal diamond; CVD polycrystalline diamond and CVD single crystal diamond.
Only two processes produce these four man made diamond types. Each of the processes results in two different types of crystalline structures. Developed by General Electric in 1955, HPHT (high pressure, high temperature) replicates the conditions that nature uses to create a natural diamond. Pressures of up to 5 GPa (giga pascals) along with temperatures of 1,500 degrees Celsius bombard the raw ingredients inside large presses. The results are small, one micrometer to one millimeter, chips and dust known as HPHT grit. Yellow in color due to nitrogen use during production, HPHT grit's application suitability relies on shape and metal content, but is most often used for abrasives.
HPHT also produces another type of man made diamond, the large single crystal. Measuring up to 10 millimeters in length, these crystals are much larger, and can reach quality and purity levels worthy of gemstones. For HPHT to produce such a large diamond, though, takes a lot of time, sometimes as long as seven days. This creates a product that is more expensive and more technically difficult to create, so HPHT large single crystal diamonds are only used in demanding situations. The HPHT "type 11a", as of 2007, was nearing the high quality and molecular structure for use in X-raytomographic imaging--replacing silicon.
CVD polycrystalline diamond is number three on the man made diamond types chart. A lower pressure process of growing diamonds, CVD, chemical vapor deposition, heats the ingredients and forms a vapor that, one atom at a time, deposits on a seed crystal. CVD polycrystalline diamond is grown flat, instead of in the cubic and single crystal form of natural diamonds, in a wafer of up to 5 millimeters thick. Depending on the production process, wafers can be grown as large as 30 centimeters (12 inches) across. Medical, optical, environmental and abrasives are just a few of the applications.
CVD single crystal diamond is the fourth man made diamond type. Usually synthesized on a single crystal diamond substrate, the CVD process can also utilize other substrates such as sapphires. The size of the resulting single crystal diamond is small, a few millimeters and meant for sensor and electronic applications. Recently, however, that all changed. In 2005, a former Bell Labs scientist discovered a way to grow CVD single crystal diamonds pure and colorless, just like a natural diamond. With applications in science, this new development also skyrocketed this fourth man made diamond type into gemstone quality.
As technology improves, so will the impact man made diamond types have on science and gemology. Military uses and applications in business are already being researched as are additional uses in technology and the world of jewelry. Economical mass production of man made diamonds may still be dozens of years in the future, but based on present breakthroughs, success is only a matter of time.
About the Author
James Chartwell writes on a variety of topics, including travel and science. Visit his informative resource all about man made diamonds at http://www.manmadediamondinfo.com/