IMAGINATION TO INNOVATION
Bright future for diamonds? Andrew C. Lemer, Ph.D., Senior Program Officer, the National Academies of Sciences, Engineering, and Medicine, Washington, D.C.; Member, International Affairs Committee Dennis Gabor, awarded the 1971 Nobel Prize in Physics for his discoveries underpinning the development of holography, once wrote, “The future cannot be predicted, but futures can be invented.” Imagination to Innovation is a periodic look at new technology and scientific discovery we could be using to invent the future of public works. 34
APWA Reporter
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June 2018
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iamonds may be a girl’s best friend, as Marilyn Monroe famously sang in the 1950s, but in more recent decades they have turned out also to be pretty good pals for industry. Just after Monroe scored a hit with her performance, General Electric produced the first commercially viable synthetic diamond with a high pressure and high temperature (HPHT) process that today is employed to make annually billions of carats of diamonds, mostly for use in cutting and machining tools, optics, electronics, and other industrial applications. Another process invented in the 1950s for making diamonds is chemical vapor deposition (CVD). A mixture of methane or another hydrocarbon gas and hydrogen heated in a vacuum chamber at very low pressures and treated to ionize the hydrogen reacts to produce pure carbon in its crystalline
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form that we recognize as diamond. These diamonds are as useful in industrial applications as those produced by the HPHT process, but they have the added attraction that their molecular structure can be grown with nitrogen atoms (or sometimes other impurities) replacing carbon atoms. These replacements, which create an accompanying vacancy in the molecular lattice, can also be produced by blasting the diamond with high-energy electrons, ions, or gamma radiation to knock out carbon atoms. These nitrogen vacancies (NVs) produce strain in the lattice but are immobile at room temperature. Annealing the crystal allows the vacancies to move; they cluster into “NV centers” (or “centres” if you read the British research papers). Researchers have learned how to use variation of the irradiation dose and annealing process to control the spacing and alignment of these NV centers in the crystal.