Science

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Thermal conductivity

Unlike most electrical insulators, diamond is a good conductor of heat because of the strong covalent bonding and low phonon scattering. Thermal conductivity of natural diamond was measured to be about 2,200 W/(m·K), which is five times more than silver, the most thermally conductive metal. Monocrystalline synthetic diamond enriched to 99.9% the isotope 12C had the highest thermal conductivity of any known solid at room temperature: 3,320 W/(m·K), though reports exist of superior thermal conductivity in both carbon nanotubes and graphene.[44][45] Because diamond has such high thermal conductance it is already used in semiconductor manufacture to prevent silicon and other semiconducting materials from overheating. At lower temperatures conductivity becomes even better, and reaches 41,000 W/(m·K) at 104 K (−169 °C; −272 °F) (12C-enriched diamond).[45]

Diamond's high thermal conductivity is used by jewelers and gemologists who may employ an electronic thermal probe to distinguish diamonds from their imitations. These probes consist of a pair of battery-powered thermistors mounted in a fine copper tip. One thermistor functions as a heating device while the other measures the temperature of the copper tip: if the stone being tested is a diamond, it will conduct the tip's thermal energy rapidly enough to produce a measurable temperature drop. This test takes about 2–3 seconds. However, older probes will be fooled by moissanite, a crystalline mineral form of silicon carbide introduced in 1998 as an alternative to diamonds, which has a similar thermal conductivity.[8][31]

Technologically, the high thermal conductivity of diamond is used for the efficient heat removal in high-end power electronics. Diamond is especially appealing in situations where electrical conductivity of the heat sinking material cannot be tolerated e.g. for the thermal management of high-power radio-frequency (RF) microcoils that are used to produce strong and local RF fields.[46]

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