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 C) or the less common C isotope. Compared to natural diamonds that are composed of a mixture of C and C isotopes, isotopically pure diamonds possess improved characteristics such as increased thermal conductivity. Thermal conductivity of diamonds is at a minimum when C and C are in a ratio of 1:1 and reaches a maximum when the composition is 100 % C or 100% C. Manufacture. The isotopes of carbon can be separated in the form of carbon dioxide gas by cascaded chemical exchange reactions with amine carbamate. Such CO can be converted to methane and from there to isotopically pure synthetic diamonds. Isotopically enriched diamonds have been synthesized by application of chemical vapor deposition followed by high pressure. Types. Carbon 12. The C 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% C and 1.1% C. This is useful for heat sinks for the semiconductor industry. Carbon 13. Isotopically pure C diamond layers 20 micrometers thick are used as stress sensors due to the advantageous Raman spectroscopy properties of C.