X-Ray Absorption Study of Highly Oriented Poly(tetrafluoroethylene) Thin Films

Ziegler, Christiane; Schedel‐Niedrig, Th.; Beamson, G.; Clark, D. T.; Salaneck, W. R.; Sotobayashi, Hideto; Bradshaw, A. M.

doi:10.1021/la00024a001

Cited by 48 publications

(26 citation statements)

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“…8e). The C 1s and F 1s spectra of the PFSA ionomer are similar to that of poly(tetrafluoroethylene) (PTFE) [51,52], as expected since PFSA consists of a PTFE backbone. The shape and relative intensity of the 689 and 694 eV peaks are different in the F 1s spectrum of the FIB section as compared to the F 1s spectrum of the microtome section, indicating a different C-F bonding environment.…”

Section: Stxm Analysissupporting

confidence: 73%

Evaluating focused ion beam and ultramicrotome sample preparation for analytical microscopies of the cathode layer of a polymer electrolyte membrane fuel cell

Melo

Hitchcock

Berejnov

et al. 2016

Journal of Power Sources

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Optimizing the structure of the porous electrodes of polymer electrolyte membrane fuel cells (PEM-FC) can improve device power and durability. Analytical microscopy techniques are important tools for measuring the electrode structure, thereby providing guidance for structural optimization. Transmission Electron Microscopy (TEM), with either Energy Dispersive X-Ray (EDX) or Electron Energy Loss Spectroscopy (EELS) analysis, and Scanning Transmission X-Ray Microscopy (STXM) are complementary methods which, together, provide a powerful approach for PEM-FC electrode analysis. Both TEM and STXM require thin (50-200 nm) samples, which can be prepared either by Focused Ion Beam (FIB) milling or by embedding and ultramicrotomy. Here we compare TEM and STXM spectromicroscopy analysis of FIB and ultramicrotomy sample preparations of the same PEM-FC sample, with focus on how sample preparation affects the derived chemical composition and spatial distributions of carbon support and ionomer. The FIB lamella method, while avoiding pore-filling by embedding media, had significant problems. In particular, in the FIB sample the carbon support was extensively

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Section: Stxm Analysissupporting

confidence: 73%

Evaluating focused ion beam and ultramicrotome sample preparation for analytical microscopies of the cathode layer of a polymer electrolyte membrane fuel cell

Melo

Hitchcock

Berejnov

et al. 2016

Journal of Power Sources

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“…Pioneering studies of the tribological properties of PTFE were done by Tabor long ago 1,2. The wear behavior of PTFE has drawn considerable interest during the past years,3 however, how to enhance the wear resistance of PTFE is still a problem, which has been puzzling the scientists all these years. Most of the work has been carried out on the effect of fillers on the tribological properties of PTFE 4–8.…”

Section: Introductionmentioning

confidence: 99%

Study on Tribological Properties of Polytetrafluoroethylene Drawn Uniaxially at Different Temperature

Liu

et al. 2005

Macro Materials & Eng

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Summary: Wear behavior correlations with morphology have been established from polytetrafluoroethylene (PTFE) drawn at 200, 327, and 375 °C with draw ratio about 4. The friction coefficient and wear rate for PTFE drawn at 327 °C are lower and the wear rate is lower than that of undrawn PTFE by about 30%. The structures of samples were characterized by scanning electron microscope (SEM), DSC, and wide angle X‐ray diffraction (WAXD). Results indicate that the debris morphologies of samples are different. The differences in the tribological behavior of undrawn and drawn samples were attributed to the improvement of the degree of the crystalline, fibrillation, and orderliness by drawing, especially, for PTFE drawn at 327 °C. The orderliness of molecular arrangement along the drawn direction is also higher for PTFE drawn at 327 °C than those of PTFE drawn at 200 and 375 °C, respectively. Therefore, the intensity of covalent bond along drawn direction is higher. The shear resistance and the deformability of the material are greatly improved and the size of the wear breakage unit decreases, which results in a good tribological property for PTFE drawn at 327 °C.SEM morphology of fractured surface perpendicular to the draw direction for PTFE drawn at 327 °C.magnified imageSEM morphology of fractured surface perpendicular to the draw direction for PTFE drawn at 327 °C.

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“…x D 2 and y D 6-10, are particularly important. Considerable effort has been devoted to understanding the surface structure and behaviour of this type of polymer using techniques such as near-edge x-ray absorption fine structure (NEXAFS), 2,4 -13 x-ray photoelectron spectroscopy 324 G. Beamson and M. R. Alexander self-assembled 24 and mechanically assembled 25 monolayers, poly(tetrafluoroethene) (PTFE) tribological transfer films 26 and plasma-deposited fluoropolymers. 27,28 Angle-resolved XPS (ARXPS) has been used to demonstrate the surface segregation of fluorine-containing groups in several fluorinated and semi-fluorinated side-chain polymers 2,10,14 -18 and to make qualitative deductions about the orientation of surface chains in semi-fluorinated selfassembled monolayers (SAMs), 29 -31 perfluorinated molecular systems 32 and plasma-deposited fluoropolymers.…”

Section: Introductionmentioning

confidence: 99%

Angle‐resolved XPS of fluorinated and semi‐fluorinated side‐chain polymers

Beamson

Alexander

2004

Surface & Interface Analysis

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Angle-resolved XPS data (elemental quantification and high-energy-resolution C 1s) are presented for ten polymers with side-chains of the form -OCO(CF 2 ) y F, -COO(CH 2 ) 2 OCO(CF 2 ) y F (y = 1, 2, 3) and -COO(CH 2 ) x (CF 2 ) y F (x = 1, y = 1, 2, 3; x = 2, y = 8). Particular attention was paid to charge compensation and speed of data acquisition, with co-addition from multiple fresh samples to give spectra with good energy resolution and good signal-to-noise ratio free from the effects of x-ray-induced degradation. Water contact angles for the polymers are also reported. The XPS data demonstrate preferential surface segregation of fluorine-containing groups for all but the shortest side-chain polymer, where the -OCOCF 3 side-chain either does not surface segregate or is too short for surface segregation to be detectable by angle-resolved XPS. In the other polymers studied the relative positions of functional groups in the sidechains correlate with the angle-resolved behaviour of the corresponding C 1s components. This shows that the surface side-chains are oriented towards the polymer surface. For the -COO(CH 2 ) 2 OCO(CF 2 ) y F .y = 1/ side-chain, the angle-resolved C 1s data suggest reduced ordering and linearity compared with y = 2 and 3. For any particular series of polymers, e.g. -COO(CH 2 ) x (CF 2 ) y F, the water contact angles increase with y, consistent with burying of the hydrophilic ester groups as y increases. For any particular value of y the sequence of water contact angles is -COO(CH 2 ) x (CF 2 ) y F > -OCO(CF 2 ) y F ∼ -COO(CH 2 ) 2 OCO(CF 2 ) y F, suggesting greater ordering and density of fluorocarbon species at the surface of the -COO(CH 2 ) x (CF 2 ) y F side-chain polymers compared with the other polymers studied. For the -COO(CH 2 ) 2 (CF 2 ) 8 F polymer a water contact angle of 124• is measured, which is greater than that of poly(tetrafluoroethene). The -COO(CH 2 ) 2 OCO(CF 2 )F polymer is unusual in that it shows a particularly low water contact angle (83 • ), suggesting that the probe fluid is able to sense both ester groups, consistent with the reduced ordering of the side-chain detected by angle-resolved XPS.

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X-Ray Absorption Study of Highly Oriented Poly(tetrafluoroethylene) Thin Films

Cited by 48 publications

References 1 publication

Evaluating focused ion beam and ultramicrotome sample preparation for analytical microscopies of the cathode layer of a polymer electrolyte membrane fuel cell

Evaluating focused ion beam and ultramicrotome sample preparation for analytical microscopies of the cathode layer of a polymer electrolyte membrane fuel cell

Study on Tribological Properties of Polytetrafluoroethylene Drawn Uniaxially at Different Temperature

Angle‐resolved XPS of fluorinated and semi‐fluorinated side‐chain polymers

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