Improvement of stacking order in graphite by molten fluoride salt infiltration

The structure of molten fluoride salt infiltrated graphite has been studied by X-ray diffraction and Raman spectroscopy. The full width at half maximum and asymmetry degree of the (0 0 2) diffraction peak decrease with the increase of salt weight gain in the infiltration indicates the improvement of the stacking order of the graphite by the molten salt infiltration. The shape of G′ resonance of Raman spectra further indicated the enhancement of the stacking order of graphite by molten salt infiltration. The shift of the (0 0 2) diffraction peak position to the higher 2θ angle and the increase of the coefficient of thermal expansion reveal that the improvement of the stacking order is resulted from the compression of the graphite matrix by the infiltrated salt network. The compressive stress induced by the salt network in the graphite matrix could reduce the d-spacing fluctuation between graphite basal planes and close the Mrozowski crack generated by the anisotropy of graphite crystal, thus increase the crystallite size along c-axis.