Thermal properties of diamond/carbon composites

The thermal conductivity, k, of diamond/carbon composites with different ra tios of sp(2)/sp(3)-bonded carbon is measured by the laser flash technique. The thermal conductivity of nanocomposites containing 6 nm diamond particl es falls within the range of k = 0.003-0.017 W/cmK; at room temperature. Th e thermal conductivity increases while nanopores are gradually filled with pyrolytic carbon (pyrocarbon/diamond mass ratio variation of 0.0-0.5). Tran smission electron microscopy data reveal a fairly uniform mixture of two ca rbon phases, the diamond and matrix having similar grain sizes. Estimates s how that the phonon free path is limited by dimensions of carbon matrix lay er. Thermal data for coarse-grain (1-2 mu m) composites are also given for comparison. (C) 2000 Elsevier Science S.A. All rights reserved.