High-thermal-conductivity, mesophase-pitch-derived carbon foams: effect of precursor on structure and properties

Pitch-based carbon foams are not new, but the development of high thermal conductivity foams for thermal management applications has yet to be explored. The research reported here focused on a novel foaming technique and the evaluation of the foaming characteristics of two mesophase pitches (Mitsubishi ARA24 and Conoco Dry Mesophase). After graphitization to 2800 degrees C, densities of the graphite foams ranged from 0.2 to 0.6 g/cm(3), with average pore diameters ranging from 275 to 350 mu m for the ARA24-derived foams, and from 60 to 90 mu m for the Conoco-derived foams. Scanning electron microscopy and polarized light optical microscopy were performed to characterize the cell walls, revealing highly aligned graphitic-like structures along the axis of the ligaments. Analysis of X-ray diffraction results determined that the foams exhibited average interlayer (d(002)) spacings as low as 0.3355 nm, stack heights (L-c) up to 80 nm and crystallite sizes (L-c) UP to 20 nm. Finally, thermal diffusivity measurements were pet-formed revealing that the bulk thermal conductivity varied with density from 40 to 150 W/m K. The specific thermal conductivities of the graphitized foams were more than six times greater than solid copper. (C) 2000 Elsevier Science Ltd. All rights reserved.