Articles you may be interested inOxygen adsorption on Ag(111): X-ray photoelectron spectroscopy (XPS), angular dependent x-ray photoelectron spectroscopy (ADXPS) and temperature-programmed desorption (TPD) studies A thermal desorption and xray photoelectron spectroscopy study of the surface chemistry of iron pentacarbonylThe interfacial chemistry of Fomblin Z2S, a commercial perfluoropolyether used as lubricant for space applications, with different metallic surfaces-440 C steel, gold, and aluminum-was studied. Thin layers of Fomblin Z2S were evaporated onto the oxide-free substrates and the interfacial chemistry studied using x-ray photoelectron spectroscopy and temperature desorption spectroscopy. The reactions were induced by heating the substrate and by rubbing the substrate with a steel ball. Gold was found to be completely unreactive towards Fomblin at any temperature. Reaction at room temperature was observed only in the case of the aluminum substrate. the most reactive towards Fomblin Z25 of the substrates studied. It was necessary to heat the 440C steel substrate to 190·C to induce decomposition of the fluid. The degradation of the fluid was indicated by the formation of a debris layer at the interface. This debris layer, composed of inorganic and organic reaction products, when completely formed, passivated the surface from further attack to the Fomblin on top. The tribologically induced reactions on 440C steel fonned a debris layer of similar chemical characteristics to the thermally induced layer. In all cases, the degradation reaction resulted in preferential consumption of the difluoroformyl carbon (-OCF P-).

of indole is a reversible reaction, and the number of related electrons is 2. Structure analysis of anodic precipitates suggests that the polymerization of indole is based on the formation of radical cations as intermediates.When the thermogravimetric analysis for the (PI)BF4 powder was conducted, the reaction rates for thermal decomposition were calculated by a computer connected to a thermal analyzer. A comparison between thermal characteristics of the (PI)BF4 and other polyindole-and polyaniline-based polymers, such as PIP, PIPF6, PAP, PAPF6, and (PA)BF4, revealed that the polyindole-based polymers were thermally decomposed at higher temperatures than the polyaniline-based ones. The maximum values of the reaction rate (R,) in the polyindole-based systems were not seriously affected by the kind of dopants. However, the values of the polyaniline-based polymers were affected by the kind of electron acceptors.Electrical conductivity for the pressed pellet of (PI)BF4 was measured in the temperature range from -150 to 25 OC. The value of log C T at 25 O C was -2.43 S/cm, and the activation energy calculated from an Arrhenius plot was 0.4057 eV. The conductivity result suggests that a possible conduction mechanism for (PI)BF4 is hopping conduction and that the charge carriers are polarons. We suggest that the conductivity for (PI)BF4 is induced from doping with BF4-anions as electron acceptors. A single ESR peak for (PI)BF4 powder at 25 OC was obtained. The values of AHpp, g, and spectral ratio were also calculated. Acknowledgment.We are grateful to Doctor H. W. Rhee, Korea Institute of Science and Technology, for cyclic voltammetry measurements.429-07-2; TEAP, 2567-83-1; indole (homopolymer), 120-72-9.The adsorption of carbon dioxide on potassium-dosed Ag(ll1) has been investigated with temperature-programmed desorption (TPD), work function measurements, and Auger electron (AES), X-ray photoelectron (XPS), and high-resolution electron energy loss (HREELS) spectroscopies. Unlike the behavior observed for other K-modified single-crystal metal surfaces, the TPD spectra of near-saturation coverages of C 0 2 on K/Ag( 11 1) for K coverages in the range 0.13 C C 0.47, where the close-packed monolayer corresponds to OK = ]I3, exhibit a sharply defined m/e = 44 peak at 796 f 6 K with no evidence for the desorption of CO at any temperature. Similar TPD experiments involving mixtures of natural and 180-labeled C02 indicate that the oxygen atoms undergo partial scrambling, suggesting that the overall process cannot be represented in terms of a simple adsorption/desorption of C02. The HREELS spectra of C02-saturated K/Ag( 11 1) show, in addition to very minor features, a sharp peak at -1480 cm-l, and XPS spectra of the same interface display a C(1s) peak with a binding energy characteristic of an electron-rich carbon species. This information is consistent with the presence of a carbon-bound CO species on the surface. Evidence against the complete dissociation of C02 was obtained from TPD, which failed to reveal features associa...

Thin films of Fomblin Z25, a perfluoropolyalkylether lubricant, were vapor deposited onto clean, oxidized aluminum, and sapphire surfaces, and their behavior at different temperatures was studied using x-ray photoelectron spectroscopy and temperature desorption spectroscopy (TDS). It was found that the interfacial fluid molecules decompose on the native oxide at room temperature, and continue to decompose at elevated temperatures, as previous studies had shown to occur on the clean metal. TDS indicated that different degradation mechanisms were operative for clean and oxidized aluminum. On sapphire substrates, no reaction was observed at room temperature. Our conclusion is that the native oxide of aluminum is neither passive nor protective towards Fomblin Z25. At higher temperatures (150 °C) degradation of the polymer on sapphire produced a debris layer at the interface with a chemical composition similar to the one formed on aluminum oxide. Rubbing a Fomblin film on a single crystal sapphire also induced the decomposition of the lubricant in contact with the interface and the formation of a debris layer.

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