Grain-boundary heat conductance in nanodiamond composites

Sintering of detonation nanodiamonds (DND) has been studied at a pressure of ∼ 7 GPa in the 700–2000 °C temperature range. The X-ray coherent-scattering regions in DND have been found to grow with increasing sintering temperature. It is shown that diamond crystallites grow by the oriented attachment mechanism. It is demonstrated that the increase of thermal conductivity of the composites thus obtained is initiated by variation of the heat conductance of the boundaries separating DND crystallites.