Formation of self-supporting porous graphite structures by Spark Plasma Sintering of nickel–amorphous carbon mixtures

Abstract

Graphitization of amorphous carbon in the presence of nickel has been reported for various configurations of the metal–carbon interface; however, no study has been performed to evaluate a possibility of forming self-supporting networks by sintering of the in situ formed graphite. In this work, we have shown that Spark Plasma Sintering (SPS) of nickel–amorphous carbon mixtures containing 50vol% of Ni at 1000°C results in the formation of networks formed by sintered graphite platelets 50–200nm thick and 0.3–2μm in diameter. Upon selective dissolution of nickel, a self-supporting porous 3D skeleton was revealed in 20mm-diameter compacts. Starting from the mechanically milled Ni–C mixture, porous graphite of uniform microstructure and containing submicron pores was obtained. A model study has been performed, in which a thin amorphous carbon film graphitized during annealing and formed a continuous graphite film with micron-sized grains covering an area of 2cm×2cm of the surface of a Ni foil. We discuss the role of the in situ formation of graphite by nickel-assisted graphitization in the formation of networks consisting of well sintered platelets during the SPS and the design possibilities of porous carbon materials produced by phase separation in nickel–graphite composites.