Papers by Author: Quan Gui Guo

Abstract: Isotropic pitch fluorides were prepared via the reaction of isotropic pitch with gas mixture containing F2 and N2 in a rotation nickel reactor. Isotropic pitch fluorides were characterized using X-ray diffraction, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, scanning electron microscopy, and elemental analysis. The results showed that the interlayer spacing of the resultant materials dramatically increase from 0.345 nm of the isotropic pitch to the range 0.643 nm to 0.798 nm. Further studies on the diversity of the functional groups indicated that the whole reaction process was composed of two steps, namely, diffusion of F2 inside the voids among isotropic pitch molecules on the surface of the particles and fluorination. The two processes interacted with each other and jointly determined the apparent speed of the reaction. The scanning electron microscopic micrographs showed that the larger bulk of isotropic pitch was gradually desquamated and became small particles, which can be attributed to the crack resulting from the volume expansion of the surface molecules of the isotropic pitch fluorides during the reaction. The final isotropic pitch fluorides were fine particles with diameters of less than 1 µm.

Abstract: High surface area activated carbon (AC) obtained by KOH activation of petroleum coke was leached by HCl aqueous solution and the effects of the ash contents of AC on performance of electric double layer capacitors (ECs) in 3M KOH aqueous electrolyte and 1 M (C2H5)4NBF4/propylene carbonate electrolyte were investigated by cyclic chronopotentiograms and electrochemical impedance spectrometry (EIS). An equivalent circuit model based on a mixed kinetic and charge transfer control was proposed to fit EIS spectra. The model parameters were extracted by Marquardt best fitting. The series solution resistances, polarization resistance and diffusion coefficient related to Warburg impedances were obtained. It is found that the series solution resistances remained constant, polarization resistances decreased and the diffusion coefficients increased after acid leaching for each electrolyte, indicating that acid leaching can remove the electronic inert ash, which decreases contact resistance among particles of activated carbon and opens or widens the blocked pores by ash components. Moreover, the specific capacitances of AC were increased by the acid leaching.