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 °C, densities of the graphite foams ranged from 0.2 to 0.6 g/cm³, with average pore diameters ranging from 275 to 350 μm for the ARA24-derived foams, and from 60 to 90 μm 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 (d₀₀₂) spacings as low as 0.3355 nm, stack heights (L_c) up to 80 nm and crystallite sizes (L_a) up to 20 nm. Finally, thermal diffusivity measurements were performed 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.