Figure 1: Microstructures of graphite/hexadecane suspensions.
(a) Optical microscope image of the microstructure of a 0.2% (volume fraction) graphite/hexadecane suspension; scale bar, 200 μm. The inset shows an optical photograph of a 50-ml, 0.2% graphite/hexadecane suspension after 3 months on the shelf. (b) A scanning electron micrograph of graphite flakes obtained by the H2SO4 intercalation, microwave expansion and ultrasonic exfoliation of natural graphite; scale bar, 1 μm. (c) A typical transmission electron microscopy image of a graphite flake. The inset shows a high-resolution transmission electron microscopy image of the selected area (denoted by A). Scale bar in c and inset correspond to 1 μm and 5 nm, respectively. (d) C1s X-ray photoelectron spectra of graphite flakes; the spectra have a main peak at 284.5 eV. The peak can be fit to peaks at 284.5, 285.6, 287.0 and 289.6 eV and thus assigned to the C=C, C−OH, C=O and O=C−OH species, respectively. (e) An optical microscope image of 0.05% graphite/hexadecane suspension. (f) An image of a frozen graphite/hexadecane composite. The black area represents graphite clusters, whereas the needle-like structure represents hexadecane grains. (g) The microstructure of a remelted graphite suspension showing the graphite percolation network. Scale bars in e, f and g are all corresponding to 200 μm.
