Preparing Highly Fluorinated Multiwall Carbon Nanotube by Direct Heating-Fluorination during the Elimination of Oxygen-Related Groups

Abstract

Pristine and oxidized multiwalled carbon nanotubes (MWCNTs) were separately prepared and directly fluorinated with F2 through two different routes: heating-fluorination and isothermal-fluorination. The amount of fluorine atoms (hereinafter referred to as “F-content”) bonding to the fluorinated samples was largely dependent on the modifing route and chemical bonding of MWCNTs. The F-content of heating-fluorinated pristine and oxidized MWCNTs was 3.2% and 9.2% respectively, which were about 8 times and 18 times that of the corresponding isothermal-fluorinated MWCNTs. According to structural analysis of samples before and after fluorination, it was found that thermal elimination of oxygen-related groups bonding to MWCNTs contributed to the formation of strongly covalent C–F bonds during heating-fluorination. It was considered that the oxygen-related groups provided reactive sites for the fluorination. The fluorination reaction took place at an sp3 carbon linking with the oxygen-related groups and did not increase the density of defect on MWCNTs. A radical-mediated mechanism is accepted for this reaction. Thus, MWCNTs could be first oxidized to increase the number of oxygen-related groups and then heating-fluorinated by F2 directly to get highly fluorinated MWCNTs with stable C–F bonds.

Insights on the reactivity of ordered porous carbons exposed to different fluorinating agents and conditions

“…For the ZTC-XeF 2 , as the fluorine content increases, the C1s (sp 2 ) component decreases (11.3%) and a part of the C-F bond type I shifts to pure type II with intermediate type I/type II contributions as well. The ZTC-FS with increased fluorine amount become insulating (with no C1s (sp 2 ) detected), with only pure type II fluorinated groups being formed, in agreement with other reports [65][66][67][68][69].…”

“…This is a result of the washing procedure (with HF) used to eliminate the zeolite template. Two fluorine-containing contributions are seen, the most intense peak (688.9 eV) corresponding to CF 2 /CF 3 groups present on the graphene edges or local defect sites [65]. A much smaller peak (686.9 eV) is assigned to the covalent C-F bond.…”

Improving Compressive Strength of Aramid Fiber by Introducing Carbon Nanotube Derivates Grafted with Oligomers of Different Conformations and Controlling Its Alignment

“…Based on previous research of our group, controlled fluorination of MWCNTs shell by two‐stage direct heating fluorination process can be realized, and FCNT with high fluorine content can be prepared . Element composition and structure of FCNT were characterized by XPS and TEM, as shown in Figure .…”

Plasma fluorination of vertically aligned carbon nanotubes: functionalization and thermal stability

“…Four components are used for the fitting of both spectra. In particular, at room temperature we can distinguish adsorbed fluorine (684.3 eV), “semi-ionic” C–F bonds (685.8 eV), covalent C–F bonds (687.4 eV) and a contribution from fluorine atoms bound to multiple fluorinated carbon (as CF 2 ) mainly located at the edges and local defect sites (688.7 eV) [ 16 , 27 , 30 , 34 – 35 ]. For oxygen, however, the following contribution are found: O=C–OH (529.8 eV), C=O (531.0 eV), C–O (532.5 eV), and oxygen bound to fluorinated carbon or to C atoms located near fluorinated carbon atoms (533.8 eV) [ 30 , 34 , 36 ].…”