Growing Diamonds

Diamond was discovered to be carbon in 1796, and it took more than 150 years from that time until a method of diamond synthesis was invented. The secret was pursued by many scientists but not unlocked until the 1950s, when diamond was synthesized almost simultaneously by Swedish and American researchers. Pressures of over 55,000 atmospheres and 1400C, plus molten iron to facilitate the change from graphite to diamond, were necessary. Now some 80 tons of synthetic diamonds are produced annually by General Electric, De Beers, and many others for industrial firms.

From the time Smithson Tennant showed that diamond was carbon, experimenters tried to synthesize diamond from graphite or lamp black. Attempts over the next 150 years were all fruitless, although the trend toward experiments at high pressure and temperature were in the right direction. The invention of tungsten carbide in the 1930s provided a material that could achieve the pressure containment necessary for growing diamond. Experiments in the 1940s by Harvard professor Percy Bridgman were unsuccessful, but finally in the early 1950s two teams succeeded. The first was led by Baltazar von Platen, at the Allmanna Svenska Elektriska Aktiebolaget (ASEA) Laboratory in Stockholm, Sweden, in 1953, but this initial success was not publicized or published. Thus, on February 15, 1955, the General Electric team of Francis Bundy, Tracy Hall, Herbert Strong, and Robert Wentorf claimed credit for the first reproducible transformation of graphite to diamond. GE went on to become the largest producer of synthetic diamond; De Beers follows, with many other manufacturers also contributing to the annual output of synthesized diamonds.

The schematic diagram at left shows the geometry of the growth capsule for growing large diamonds. Small diamo

nds are placed at the bottom of the active part of the capsule as seeds for the growth of large diamonds. Graphite dissolves into molten metal, usually iron or cobalt, and precipitates as diamond on the seeds at the colder bottom. It takes a few days to grow diamonds a few mm. across. Micro-diamond growth i

s much faster, taking a few tens of minutes.

Into the Future

As methods for growing diamond, both at high pressure and by chemical vapor deposition, improve, and as science finds ways to take advantage of diamond’s properties, the potential applications of diamond’s superlative properties appear boundless. From super electronics, to indomitable optical windows, to unscratchable surfaces – maybe the next watch bezel – diamond is an obvious choice.

Managing heat, particularly in electronics, with large layers of CVD diamond is a rapidly expanding field. One of the most imaginative of these is the three-dimensional multi-chip module, which holds out the promise of an extremely powerful supercomputer. To gain speed, electronics need to be as compact as possible, concentrating waste heat as well. By stacking sandwiches of electronics and CVD diamond, a supercomputer could be made small and cool enough to function. Diamond windows for infrared devices are under development and should find their way into the tough environment of laser-guided smart bombs and more constructive uses in industry as well. The use of diamonds as radiation detectors, light emitters in electronic displays, and coatings to make surfaces indomitable or unwettable are being researched now. Beyond their imprint as a tool, diamonds will be showing up in more and more products in the future, probably in your home electronics, appliances, and automobiles.

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