Isotopically pure diamond

An isotopical pure diamond is a type of diamond that is composed entirely of one isotope of carbon. Isotopically pure diamonds have been manufactured from either the more common carbon isotope with mass number 12 (abbreviated as 12C) or the less common 13C isotope. Compared to natural diamonds that are composed of a mixture of 12C and 13C isotopes, isotopically pure diamonds possess improved characteristics such as increased thermal conductivity.[1] Thermal conductivity of diamonds is at a minimum when 12C and 13C are in a ratio of 1:1 and reaches a maximum when the composition is 100% 12C or 100% 13C.[1]

Manufacture

The isotopes of carbon can be separated in the form of carbon dioxide gas by cascaded chemical exchange reactions with amine carbamate.[2] Such CO2 can be converted to methane and from there to isotopically pure synthetic diamonds.[3] Isotopically enriched diamonds have been synthesized by application of chemical vapor deposition followed by high pressure.[1]

Types

Carbon 12

The 12C isotopically pure, (or in practice 15-fold enrichment of isotopic number, 12 over 13 for carbon) diamond gives a 50% higher thermal conductivity than the already high value of 900-2000 W/(m·K) for a normal diamond, which contains the natural isotopic mixture of 98.9% 12C and 1.1% 13C. This is useful for heat sinks for the semiconductor industry.[4]

Carbon 13

Isotopically pure 13C diamond layers 20 micrometers thick are used as stress sensors due to the advantageous Raman spectroscopy properties of 13C.[5]

References
  1. Anthony TR, Banholzer; Banholzer, W (April 1992). "Properties of diamond with varying isotopic composition". Diamond and Related Materials. 1 (5–6): 717–726. Bibcode:1992DRM.....1..717A. doi:10.1016/0925-9635(92)90197-V.
  2. Takeshita K, Ishidaa M (December 2006). "Optimum design of multi-stage isotope separation process by exergy analysis". ECOS 2004 - 17th International Conference on Efficiency, Costs, Optimization, Simulation, and Environmental Impact of Energy on Process Systems. 31 (15): 3097–3107. doi:10.1016/j.energy.2006.04.002.
  3. Anthony TR, Bradley JC, Horoyski PJ, Thewal ML (November 1996). "Graphite rod precursors for isotopically pure fullerenes and diamond". Carbon. 34 (11): 1323–1328. doi:10.1016/S0008-6223(96)00060-7.
  4. Bray JW, Anthony TR (February 1991). "On the thermal conductivity of diamond under changes to its isotopic character". Z. Phys. B. 84 (1): 51–57. Bibcode:1991ZPhyB..84...51B. doi:10.1007/BF01453758. S2CID 120365422.
  5. Qiu W, Velisavljevic N, Baker PA, Vohra YK, Weir ST (June 2004). "Isotopically pure 13C layer as a stress sensor in a diamond anvil cell". Appl. Phys. Lett. 84 (26): 5308–5310. Bibcode:2004ApPhL..84.5308Q. doi:10.1063/1.1766077.
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