Mechanical, electrical, thermal performances and structure characteristics of flexible graphite sheets

The mechanical, electrical, and thermal performances of flexible graphite sheets (FGS) derived from HClO4-graphite intercalation compounds were characterized by measuring their tensile strength, electrical resistivity, and thermal conductivity. Results show that these performances are closely related to the density of sheets and exfoliated volume (EV) of exfoliated graphite. Enhancing density of sheets tends to improve their in-plane tensile strength, electrical, or thermal performance while using the exfoliated graphite of low EV to prepare sheets is prone to resulting in low in-plane tensile strength but high electrical or thermal performance. The structure characteristics of FGS were characterized by using X-ray diffraction, Raman spectroscopy, and scanning electron microscopy. The X-ray diffraction results show that the average interlayer spacing of graphite microcrystals for sheets, d 002, is 3.357 A which is the same as that of natural graphite flake, but the stacking height of sheets, Lc, is lower than that of natural graphite. The Raman spectra indicate that sheets has both disorder peak and graphite one and the intensity ratio of them is ca. 0.06, which is almost the same as that of natural graphite, but higher than that of exfoliated graphite.