Man Made Diamond Types
Diamonds are the hardest substance occurring naturally on Earth. Their luster and brilliance and durability have long been a staple of the jewelry industry, but they also have applications in technology. Scientist and researchers have been attempting to “grow” diamonds for these uses for decades. Lower cost and the capability of mass production are the incentives behind the research.
Synthetic diamonds and diamond substitutes have been around since Dr. Moissan discovered tiny little diamond bits, ”Moissanite,” in a crater in Arizona in 1893. The ability to produce pure, colorless laboratory grown diamonds is a more recent occurrence. The gems are available via several different sources, and can be classified in four man made diamond types.
First, let's clarify the definition of a man made diamond. A true man made diamond has the same molecular structure, hardness, brilliance, conductivity--everything--a naturally occurring mined diamond has. Gems like cubic zirconia (CZ) and moissanite are diamond simulants. That is, they simulate diamonds, but are made from different materials. Cubic zirconia is created from zirconium oxide (ZrO2) and isn’t as hard as diamonds. Moissanite is silicon carbide (SiC), and is almost equal to diamond in hardness, but can not quite compete with its colorless quality.
Man made diamonds types refer to those crystals that are everything diamond-like, except for being manufactured in a laboratory instead of being mined. The four types of man made or synthetic diamonds are: HPHT grit; HPHT large single crystal diamond; CVD polycrystalline diamond; CVD single crystal diamond.
These four types are comprised two different methods of production, and two different crystal structure that result from those methods. First used in 1955 by General Electric, high pressure, high temperature (HPHT) is exactly what it implies; large presses that can produce pressure of 5 GPa (giga pascals) at 1,500 degrees Celsius to reproduce the conditions that create natural diamond inside the Earth.
HPHT grit, small chips and diamond dust are the result, ranging in size from approximately one (1) millimeter to as small as one (1) micrometer. Suitability for applications depends on shape and metal content. Normally used for abrasives, HPHT grit is usually yellow due to nitrogen used in the manufacturing process.
The second man made diamond type is the HPHT large single crystal diamond. These synthetic diamond crystals are much larger, reaching up to 10 millimeters in length. To produce these larger crystals, some of which can be used in the jewelry industry as a yellow artificial diamond, requires maintaining the HPHT process for up to a week. Technically, that’s difficult, and results in higher production costs.
Applications are the same as the HPHT grit, but because it is pricier and performs better, HPHT large single crystal diamonds are used in the more demanding environments. As of 2007, the HPHT “type 11a” diamonds were approaching the high purity and crystalline structure required to replace silicon in X-raytomographic imaging.
Third of the man made diamond types is the CVD polycrystalline diamond. Chemical vapor deposition (CVD), is a lower pressure method of growing diamonds by heating the ingredients until a vapor forms, which then deposits, atom by atom, on a seed crystal. Instead of resulting in a cubic and single crystal structure like naturally occurring diamonds, CVD polycrystalline diamond is grown flat as a wafer up to 5 millimeters thick. The wafer can be grown up to 30 centimeters (12 inches) in diameter, depending on the technology used to manufacture. Applications vary from abrasives, to optical, to medical to environmental.
Lastly, the fourth man made diamond type is the CVD single crystal diamond. The synthesis of single crystal diamond using the CVD process is usually done on a single crystal diamond substrate, but other substrates have been used - for instance, sapphire.
Until recently, available sizes were typically limited to a few millimeters in height and used in electronic, sensor and detector application. In 2005, however, a former Bell Labs scientist discovered a way to grow CVD single crystal diamonds to the specification of a colorless, pure diamond. Still usable in technology, this recent development has created a man made diamond worthy of the jewelry industry.
Man made diamond types have an impact on the world and will continue to do so, especially as technology improves. Research continues regarding the appropriate applications, not only in the jewelry industry, but also for use in military and businesses. Decades may still remain before an economically feasible method can be obtained for mass production of man made diamonds, but the quest goes on.
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