Yaoming Xie

X-Ray Photoelectron-Spectroscopic Studies of Carbon Fiber Surfaces. Part IX: The Effect of Microwave Plasma Treatment on Carbon Fiber Surfaces

X-ray photoelectron spectroscopy has been used to monitor the surface chemical changes occurring on type II carbon fibers exposed to air, oxygen, and nitrogen plasmas. In all cases the plasmas caused changes in surface functionality, in terms of both C-O and C-N functionality. Prolonged exposure to the plasmas caused loss of surface functionality for air and oxygen plasmas, and extended treatment caused fiber damage. Plasma treatment of fibers promises to be an effective method of fiber treatment.

X-Ray Photoelectron-Spectroscopic Studies of Carbon Fiber Surfaces. Part XII: The Effect of Microwave Plasma Treatment on Pitch-Based Carbon Fiber Surfaces

X-ray photoelectron spectroscopy has been used to monitor the surface chemical changes on DuPont high-modulus pitch-based carbon fiber surfaces brought about by microwave air-plasma treatments for different periods of time. The air-plasma treatment increased the fiber surface functionalities, but extended treatment caused fiber damage. X-ray diffraction studies showed that the bulk structure was not affected by the air-plasma treatment. XPS valence band spectra proved a more sensitive probe of the surface chemistry of the carbon fibers than XPS core studies. Air-plasma treatment of fibers promises to be an effective method of fiber treatment.

X-Ray Photoelectron Spectroscopic Studies of Carbon Fibers. Part XIV: Electrochemical Treatment of Pitch-Based Fibers and the Surface and Bulk Structure Changes Monitored by XPS, XRD, and SEM

Core and valence band X-ray Photoelectron Spectroscopy, as well as X-ray Diffraction and Scanning Electron Microscopy, has been used to monitor the surface chemistry and bulk structure changes when DuPont E-120 high-modulus pitch-based carbon fibers are anodically oxidized in 1 M HNO3 solution at different anodic potentials. Electrochemical treatments changed both the surface and bulk chemistry of the fiber, while plasma treatment only affected the surface structure. Electrochemically treated fibers showed significant surface functional group decomposition after exposure to the x-ray radiation during the x-ray photoelectron spectroscopy experiment, but the decomposition occurred only on the top surface layer.

X-ray Photoelectron Spectroscopic Studies of Carbon Fibers. Part XV: Electrochemical Treatment on Pitch-based Fibers by Potentiostatic and Galvanostatic Methods

DuPont E-120 high-modulus pitch-based carbon fibers were treated on both an electrochemical standard cell system and a pilot plant system under potentiostatic and galvanostatic operation modes. X-ray photoelectron spectroscopy (XPS) and x-ray diffraction (XRD) techniques were used to monitor the fiber surface chemistry and bulk structure changes brought about by the electrochemical treatments. On both the standard cell and pilot plant systems, galvanostatic treatments gave more reproducible changes to the surface and bulk chemistry of the carbon fibers than did potentiostatic treatments. The difference was more obvious when the fibers were treated for a short period of time (less than one minute). The pilot plant system allows the fibers to be treated continuously to obtain a large amount of surface-modified fibers, enabling composite samples to be prepared. The work shows that operating the pilot plant system under a galvanostatic mode allows us to obtain a much more evenly treated fiber surface along the length of the fiber tow.

Ultrahigh Purity Graphite Electrode by Core Level and Valence Band XPS

Both core level and valence band XPS spectra were obtained from an ultrahigh purity (UHP) graphite electrode surface. This UHP graphite had a very low oxygen content and an extremely low nitrogen content on its surface. It had a very graphitic structure in both the surface and the bulk as evidenced by XPS and XRD studies. [See Y. Xie and P. M. A. Sherwood, Appl. Spectrosc. 43, 1153 (1989); Chem. Mater. 1, 427 (1989); 2, 293 (1990); Appl. Spectrosc. 44, 797 (1990); Chem. Mater. 3, 164 (1991); Appl. Spectrosc. 44, 1621 (1990); 45, 1158 (1991); Y. Xie, T. Wang, O. Franklin, and P. M. A. Sherwood, ibid. 46, 645 (1992).] Our previously reported work [Y. Xie and P. M. A. Sherwood, Chem. Mater. 1, 427 (1989); 2, 293 (1990); Appl. Spectrosc. 44, 797 (1990); Chem. Mater. 3, 164 (1991); Appl. Spectrosc. 44, 1621 (1990); 45, 1158 (1991); Y. Xie, T. Wang, O. Franklin, and P. M. A. Sherwood, 46, 645 (1992)] showed that XPS valence band spectra were more sensitive to the surface chemical environment than core level spe...

X-Ray Photoelectron Spectroscopic Studies of Carbon Fiber Surfaces. Part XVI: Core-Level and Valence-Band Studies of Pitch-Based Fibers Electrochemically Treated in Ammonium Carbonate Solution:

DuPont E-120 high-modulus pitch-based carbon fibers were treated electrochemically in 0.5 M (NH4)2CO3 solution under both potentiostatic and galvanostatic modes. X-ray photoelectron spectroscopy (XPS) was used to monitor the chemical changes on the carbon fiber surfaces. Both core-level and valence-band spectra showed that the treatment introduced both oxygen-containing and nitrogen-containing functional groups onto the fiber surfaces, and the mainly oxygen-containing functional groups produced were carbonyl (C=O) type functional groups after longer treatment time. For short treatment time, hydroxide (C-OH) type groups were the dominant functionality, and ether (C-O-C) or epoxide type groups were also formed. The O 2s peaks from oxygen atoms in the hydroxide functionality and the ether or epoxide groups are well separated in the valence-band spectra; the corresponding O 1s peaks, however, are not separated in the O 1s core-region spectra.

Highly Oriented Pyrolytic Graphite by Core Level and Valence Band XPS

Both core level and valence band XPS spectra were obtained from a Union Carbide highly oriented pyrolytic graphite (HOPG) monochromator sample. Compared to Du Pont and Amoco pitch‐based carbon fibers with different modulus and some PAN‐based carbon fibers, the HOPG had much less oxygen components on the surface than the carbon fibers, except Du Pont E‐120 high modulus pitch‐based carbon fiber. [See Y. Xie and P. M. A. Sherwood, Appl. Spectrosc. 43, 1153 (1989); Chem. Mater. 1, 427 (1989); 2, 293 (1990); Appl. Spectrosc. 44, 797 (1990); Chem. Mater. 3, 164 (1991); Appl. Spectrosc. 44, 1621 (1990); 45, 1158 (1991); Y. Xie, T. Wang, O. Franklin, and P. M. A. Sherwood, ibid. 46, 645 (1992).] No nitrogen was found on the HOPG surface, nor on any of the pitch‐based carbon fibers measured in our laboratory, but nitrogen was shown in all the PAN‐based carbon fibers. Our previously reported work [Y. Xie and P. M. A. Sherwood, Chem. Mater. 1, 427 (1989); 2, 293 (1990); Appl. Spectrosc. 44, 797 (1990); Chem. Mater. ...

AS4 PAN‐based Carbon Fiber by Core Level and Valence Band XPS

Hercules AS4‐6k PAN‐based carbon fiber surface was analyzed with both core level and valence band XPS. Compared to Du Pont and Amoco’s pitch‐based carbon fibers with different modulus and Hercules’ AU4‐12k PAN‐based fiber, the AS4 fiber had much more oxidized components on the surface [Y. Xie and P. M. Sherwood, Appl. Spectrosc. 43, 1153 (1989); Chem. Mater. 1, 427 (1989); 2, 293 (1990); Appl. Spectrosc. 44, 797 (1990); Chem. Mater. 3, 164 (1991); Appl. Spectrosc. 44, 1621 (1990); 45, 1158 (1991); Y. Xie, T. Wang, O. Franklin, and P. M. Sherwood, ibid. 46, 645 (1992)]. The AS4 PAN‐based fiber had a much less graphitic structure in both the surface and the bulk than the pitch‐based fibers as evidenced by both XPS and XRD. It also had a higher nitrogen content on its surface than the AU4‐12k PAN‐based fiber, but no nitrogen was found on any of the pitch‐based carbon fibers measured in our laboratory. Our previously reported work [Y. Xie and P. M. Sherwood, Chem. Mater. 1, 427 (1989); 2, 293 (1990); Appl. Sp...

Type II PAN‐based Carbon Fiber by Core Level and Valence Band XPS

Courtauds type II PAN‐based carbon fiber surface was analyzed with both core level and valence band XPS. Compared to Du Pont and Amoco pitch‐based carbon fibers with different moduli, the Courtauds type II PAN‐based fiber had much more oxidized components on the surface [See Y. Xie and P. M. A. Sherwood, Appl. Spectrosc. 43, 1153 (1989); Chem. Mater. 1, 427 (1989); 2, 293 (1990); Appl. Spectrosc. 44, 797 (1990); Chem. Mater. 3, 164 (1991); Appl. Spectrosc. 44, 1621 (1990); 45, 1158 (1991); Y. Xie, T. Wang, O. Franklin, and P. M. A. Sherwood, ibid. 46, 645 (1992).] The type II fiber had a much less graphitic structure in both the surface and the bulk than the pitch‐based fibers as evidenced by both the XPS and XRD. It also had a notable nitrogen content on its surface but less than the Hercules AU4‐12k and AS4‐6k PAN‐based fibers. However, no nitrogen was found on any of the pitch‐based carbon fibers measured in our laboratory. Our previously reported work [Y. Xie and P. M. A. Sherwood, Chem. Mater. 1, 427...