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Prior to the rise of carbon nanotubes, one of the most prominent topics in materials was the development of synthetic diamonds. These actual diamond-structure carbon crystals are formed in a lab, and are not to be confused with artificial gemstones such as cubic zirconia. They are also different from natural diamonds, which (as their name suggests) occur in nature.
The development of synthetic diamonds offered the promise of a usable substance with the highest room-temperature thermal conductivity and the lowest electrical conductivity of any known material, along with incredible strength and hardness. At the time, it was anticipated that synthetic diamonds would find uses in everything from semiconductors to cutting tools to actual mechanical components. Several years later, however, synthetic diamonds have still managed to find little use outside of simple tool coatings for drill bits and saw blades.
Producing Synthetic Diamonds
In terms of production, diamond synthesis involves the relatively simple process of chemical vapor deposition (CVD). With CVD, the carbon atoms of a hydrocarbon gas align themselves into a crystal atop a substrate material. In modern labs, this can be accomplished at growth speeds up to 100 micrometers/hour.
Chemical vapor deposition has been used to grow single-crystal diamonds up to 10 carats in size, or roughly a half inch in diameter. While this may not sound large enough to produce anything incredibly useful, these numbers are only for single-crystal diamonds, a special variety that is useful for making incredibly hard objects or semiconductors. Multi-grained crystals, which are similar to diamonds found in nature, have been grown at similar rates, but into the shapes of wafers several inches in diameter.
Planing, Slicing, and Possible Applications
Once produced, both diamond types can be planed down or sliced into wafers (using lasers) to make machine components, suitable substrates for semiconductors, and even high-performance windows for use in extreme environments. What's more is that early versions of all of these components have been successfully made and tested in the past few years. To date, however, none have found widespread commercial or even academic use.
Despite proven methods of production and possible applications, academic and scientific interest in synthetic diamonds has declined dramatically in the wake of nanotubes, and the possible profits nanotubes could bring if they ever manage to become commercially or scientifically viable.
Will synthetic diamonds (and all of their remarkable properties) ever get the chance to live up to their anticipated uses; or, like many great potential technologies before them, have they been left in the past after a shift in public interest?
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