|The long quest for diamond synthesis
For about 150 years scientists strived to create glittering gems; in the 1950s, they succeeded.
At a press conference in Schenectady, NY, on February 15, 1955, General Electric announcedwith considerable fanfarethat a team of its scientists had created, for the first time, genuine diamonds in a laboratory. All GE had to show reporters was a tiny handful of dull, blackish grains. And the company admitted that production of gem-quality crystals was decades awayif possible at all. Its process, on the other hand, showed promise for making industrial-grade stones, a $60 million market in the United States.
The news rated the front page in The New York Times, The Wall Street Journal, and other leading newspapers. And it created turmoil in the tightly controlled world diamond business, at least temporarily.
The quest for synthetic diamonds had been under way for about 150 years. In 1797, the English chemist Smithson Tennant, building on earlier experiments by Antoine-Laurent Lavoisier, burned a diamond in an atmosphere of oxygen and produced only carbon dioxide. Hence diamonds must be composed solely of carbon. Scientists soon attempted to convert common forms of carbon into the dense, hard, brilliant gems. They were stymied, however, because nobody knew how diamonds formed in natureor even where.
In the 1870s, after rich deposits of diamonds were uncovered near Kimberley in South Africa, geologists began studying the rock, kimberlite, in which the valuable crystals were embedded. They discovered that it originated more than 100 miles below the earths surface and was extruded upward during volcanic activity. Thus, diamonds must crystallize from carbon under the extreme pressures and temperatures deep within the earth. Several researchers quickly began efforts to duplicate those conditions in their laboratories.
One was the largely self-taught Scottish chemist James B. Hannay. He filled thick-walled iron tubes with carbon-rich oil and lithium, tightly sealed each end, and heated them red hot in a furnace. The tubes had an unnerving tendency to explode, shattering the furnace and spewing shrapnel across the laboratory. From three tubes that remained intact, Hannay managed to extract in 1880 traces of crystals that he claimed were diamonds. Years later, some of the crystals, preserved in the British Museum, underwent careful analysis and were shown to be natural diamonds. Hannay apparently perpetrated a hoax. Or, perhaps, his workers, fearing for their safety, seeded the tubes with real diamonds in the hope that Hannay, satisfied with his success, would turn his attention to less hazardous experiments.
About 1890, the French chemist Henri Moisson designed an electric arc furnace capable of reaching heats up to 3000 °C. Moisson, who in 1906 would win the Nobel Prize in chemistry for his earlier work on isolating and studying fluorine, used his furnace for experiments on making diamonds from graphite dissolved in molten iron. He managed to produce a few microscopic particles that he thought were diamonds. But no one was able to reproduce his results, and the consensus now is that Moisson only formed silicon carbide crystals.
Sir Charles Parsons was a British scientist who became interested inin fact, obsessed bymaking diamonds. Starting in the mid-1880s, he tried to form diamonds by passing extremely high electrical currents up to 100,000 amperesthrough charcoal or coke under pressures as high as 12 kilobars. After thousands of attempts over a span of 30 years, he finally admitted failure.
The leading researcher in high-pressure studies in the United States was Percy W. Bridgman. While a graduate student studying physics at Harvard University in 1905, Bridgman stumbled onto a new design for a high-pressure apparatus that enabled him to sustain high pressures, eventually 20 kilobars and higher. Graphite was one of the materials he experimented with. But even when he heated samples to 600 °C and put them under pressures approaching 100 kilobars, synthetic diamonds eluded him.
During World War II, demand for industrial diamonds to shape the machine tools needed for producing military hardware increased substantially. The world was almost entirely dependent on South Africa for diamonds, a source on which the powerful De Beers Consolidated Mines cartel had a hammerlock. After the war, Norton Co., a leading producer of industrial abrasives and other high-performance materials, launched a research program to study the effect of extremely high pressures on materials, headed by chemist Loring Coes. Its ultimate goal was synthesizing diamond. Coes designed an improved high-pressure device that could be heated electrically to more than 1000 °C. In it he was able to form a wide array of tiny precious and semiprecious stones, such as garnet, topaz, and zircon, as well as several crystals unknown in nature, at pressures up to 35 kilobars. Diamond, however, was beyond his grasp.
Looking for additional help, in 1950 Norton approached GE to form a joint venture. The two firms had collaborated with Carborundum Co. in 1941 in funding a diamond-making project by Bridgman, but that effort had ended when U.S. entry into World War II shifted research priorities elsewhere. Although GE showed interest in the Norton proposal, it decided instead to go it alone. It set up Project Superpressure at its renowned research laboratory in Schenectady in 1951, with a team of two physicists, two chemists, and two engineers under project manager Anthony J. Nerad, an engineer.
During the next three years, the team devoted its efforts to designing improved high-pressure equipment and running experiments to get a better handle on the thermodynamics and chemistry of carbon. Two devices built during 1953 were particularly promising. One, developed by physicist Herbert M. Strong, was capable of pressures of 40 kilobars at temperatures up to 2000 °C. The second, conceived by chemist H. Tracy Hall, involved two opposed conical carbide pistons surrounded by a doughnut-shaped structure that Hall called a belt. In time, it was able to sustain pressures of 70 kilobars at temperatures up to 2000 °C. Still no diamonds.
As 1954 drew to a close, top managers of GEs research lab were losing patience. Project Superpressure had more than used up all the funds originally budgeted for it with little to show other than some sophisticated apparatus. They threatened to pull the plug on the diamond team.
On the afternoon of December 8, 1954, Strong loaded his device with a carbon powder sample seeded with two small, natural diamonds surrounded by iron foila hoped-for catalyst. He let the apparatus run overnight at 40 kilobars and 1250 °C. When he examined the results the next morning, the two seed crystals fell free, unchanged. He sent the remaining glob of congealed iron to the metallography lab. A week later it reported that two tiny hard crystals were found in the mass of metal. They had all the characteristics of diamonds. Seemingly, the century-and-a-half quest to make diamonds had at last reached its goal.
The next day, Hall ran a similar experiment in his belt apparatus at about 75 kilobars and 1200 °C for 38 minutes. When he broke open his samples, he reported, my hands began to tremble . . . My eyes caught the flashing light from dozens of triangular faces of octahedral crystals. Hall, too, had made diamonds. Soon he was repeating his synthesis over and over20 times in the next 2 weeksmaking up to a quarter of a carat with each run.
Strong, on the other hand, could not reproduce his results. Most likely, Strong had accidentally seeded his sample with four, rather than two, real diamonds. So credit for making diamonds for the first time rightfully goes to Hall.
Or does it?
During World War II, the giant Swedish electrical equipment company Allmänna Svenska Elektriska Aktiebolaget (ASEA) became interested in making gem-quality diamonds. It hooked up with an eccentric Swedish inventor, Balthazar von Platen. Von Platen had worked out a novel, complex, high-pressure press that consisted of six wedge-shaped pistons, each of which pressed against one face of a cubic sample. Heat was supplied by igniting thermite that surrounded the sample.
Needing support for his experiments, von Platen turned to ASEA in the early 1940s. His cumbersome device was very difficult to assemble and operate. Several years of experimenting in the machine with graphite at pressures as high as 80 kilobars and temperatures to 4000 °C brought only failure. But ASEA persisted into the 1950s. Finally, in early 1953, using iron carbide as a carbon source, the ASEA scientists obtained 4050 crystals the size of grains of sand from their experiment. Close examination proved them to be, indeed, diamonds. The experiment was repeated twice more that year.
Strangely, though, ASEA kept its discovery a tight secret. Whatever the reason, no full account of its results was published until 1960. By then, ASEA had long been scooped by GEs 1955 publicity.
GE considered that its Project Superpressure was an organized team effort, with each of its seven scientists equally deserving of credit for diamond synthesis. Hall, however, was basically a loner who never had a close relationship with his colleagues. He believed that it was his experiments with his belt high-pressure apparatus that led to success. Disgruntled that he did not receive greater recognition for this achievement, he left GE in September 1955 to become a professor of chemistry and director of research at Brigham Young University in Utah.
GE, meanwhile, moved quickly to turn its discovery into a marketable product. It applied for patents. The diamond team successfully turned a wide array of carbon-rich materials, including even roofing tar, mothballs, and chunky peanut butter, into diamonds. It found that it could use many metals, including nickel, chromium, and cobalt, to grow diamonds in addition to iron. It learned how to grow single crystals to sizes as large as five carats (1 gram), although the process was too slow for the gems to be competitive with natural diamonds for use in jewelry. The belt apparatus was improved until it could reach pressures of 150 kilobars and temperatures to 5000 °C.
By 1959, the company was selling about 750,000 carats of synthetic stones a year, accounting for about 10% of the U.S. market for industrial diamonds.
Today, about 90% of all industrial diamonds are synthetic. High-pressure research, much of it in Russia as well as by De Beers, and improved equipment have made it possible to create gem-size diamond crystals that are nearly indistinguishable from the stones mined from the earth.
David M. Kiefer, former assistant managing editor of Chemical & Engineering News until his retirement in 1991, is a consulting editor for Todays Chemist at Work. Send your comments or questions regarding this article to firstname.lastname@example.org or the Editorial Office 1155 16th St N.W., Washington, DC 20036.