Changes in the structure and functional groups produced during the fluorination of mesophase microbeads

The mesocarbon microbead (MCMB) fluorides with different fluorine contents were obtained in the temperature range of 100–110 °C in the presence of the mixed gas containing fluorine and nitrogen. The MCMB fluorides were characterized by X-ray diffraction, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, scanning electron microscopy and elemental analysis. The results showed that the carbon lamination of the MCMBs was severely destroyed, which was indicated by a dramatic increase in the interlayer spacing of the resultant materials from 0.345 nm of the MCMBs to the range of 0.656 to 0.722 nm. Further studies on diversity of functional groups indicated that the whole fluorination reaction process comprises two steps: include a first diffusion of fluorine gas molecules inside the voids formed due to loose packing of MCMB molecules, and then fluorination. The two steps interacted with each other and jointly determined the apparent speed of the reaction. The original lamination structure of the MCMBs was completely destroyed for volume expansion of the resultant materials and diffusion of fluorine/nitrogen mixed gases. The final MCMB fluorides are themselves a conglomeration of particles with diameters ranging from 1 to 3 μm.