Thermal conductivity of CVD diamond fibres and diamond fibre-reinforced epoxy composites

• Published in: Diamond and related materials 2005-03, Vol.14 (3), p.598-603
• Main Authors: May, P.W., Portman, R., Rosser, K.N.
• Format: Article
• Language: English
• Subjects: Chemical vapor deposition (including plasma-enhanced cvd, mocvd, etc.); Composites; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Conductivity of specific materials; Cross-disciplinary physics: materials science; rheology; Diamond fibres; Electronic transport in condensed matter; Elemental semiconductors; Exact sciences and technology; Materials science; Methods of deposition of films and coatings; film growth and epitaxy; Physics; Thermal conductivity
• ISSN: 0925-9635; 1879-0062
• DOI: 10.1016/j.diamond.2004.10.039

Diamond fibres were fabricated using hot filament chemical vapour deposition (CVD) with tungsten wire of varying diameters as the cores. A steady-state technique was used to measure the thermal conductivity along the length of the individual fibres over a distance of 6 cm. The room temperature thermal conductivity of the fibres ranged between 750 and 1088 W m −1 K −1. This is lower than values measured for CVD diamond thin films by other groups, due to the fact that the measurements were made perpendicular to the growth direction, and hence involved traversing a large number of grain boundaries. Epoxy composites containing the fibres were produced. The thermal conductivity of these composites was compared to metal bars of the same dimensions for both heating and cooling cycles. It was found that diamond composites are more efficient heat conductors than metal rods and can combine good lengthwise heat transfer with low heat transfer to the surroundings, as well as high electrical insulation. This makes them suitable for applications such as ‘heat pipes’ in electrical circuits.