Nondestructive evaluation of carbon fiber by mirage-FTIR spectroscopy

Abstract

Carbon fiber, being black (high absorptivity) material, is difficult to analyze by the conventional infrared (IR) techniques. Probably due to this fact, most of the studies reported in literature have been restricted to the thermal degradation of polyacrylonitrile-based fibers only. In the present work, we have used a recently developed mirage-FTIR technique for recording the IR spectra of carbon fibre at different stages of production, right from the precursor to final product. A study of microstructural/ chemical changes occuring not only provides the information on structure but also demonstrates an unusual and highly technical industrial application.

Templated Synthesis of Carbon Nanofibers from Polyacrylonitrile Using Sepiolite

“…2B) This last band disappears progressively during heating treatment in air at 220 C, with the concomitant development of a new intense broad band centered at 1596 cm ±1 . This last band is attributed to m C=C and m C=N vibrations due to the AN cyclization and conjugation processes, [13] as indicated in Scheme 1. The 13 C cross-polarization magic-angle spinning (CP-MAS) NMR spectra of solids heated at the same temperature (220 C) show signals at 154, 139, 116, and 31 ppm (Fig.…”

“…This is polymerized to give polyacrylonitrile (PAN), which is further thermally treated to form carbon nanofibers inside the pores. We have clearly shown the mechanisms and the role of the structural tunnels of sepiolite in the adsorption, polymerization, and graphitization of AN by applying spectroscopic techniques as FTIR spectroscopy, 13 C NMR spectroscopy, in-situ EIS (electrochemical impedance spectroscopy), and other structural, textural, and analytical tools (powder X-ray diffraction (PXRD), scanning transmission electron microscopy±energy-dispersive X-ray analysis (STEM±EDX), differential thermal analysis (DTA), thermogravimetric analysis (TG), N 2 isotherms, etc.). The resulting solids constitute a new class of conductive carbon±clay nanocomposites, useful for applications in diverse electrochemical devices such as lithium batteries, sensors, or electrocatalysts.…”

Detailed examination of nitrile stretching vibrations relevant for understanding the behavior of thermally treated polyacrylonitrile

“…Suggestion B is connected with a β‐enamino nitrile moiety; this has been suggested in particular in studies in which the second peak was found at wave numbers decisively lower than 2200 cm −1 . Suggestion C addresses the most defined motif, namely, the product of a potential Ziegler–Thorpe‐type cyclization within the polymeric chain . Suggestions D (Fermi resonance) and E (originated by cyanide anions) have each only been proposed in one single article.…”

“…Fourier transform infrared (FTIR) spectroscopy is one of the most powerful characterization methods for solving this problem, and it has already been used extensively in several studies. [21][22][23][24][25][26][27] In particular, a focus was set on the development of the nitrile m(CBN) stretching vibrations during thermal treatment because of their appearance in the range between 2170 and 2270 cm 21 (the nitrile region), which is unperturbed by other vibrations. For the PAN starting material in general, only one peak in the nitrile region was observed at about 2240 cm 21 .…”

“…22 Suggestion C addresses the most defined motif, namely, the product of a potential Ziegler-Thorpe-type cyclization within the polymeric chain. [23][24][25] Suggestions D (Fermi resonance) 26 and E (originated by cyanide anions) 27 have each only been proposed in one single article.…”