XPS STUDIES ON RADIATION-INDUCED STRUCTURAL-CHANGES IN THE COPOLYMER OF TETRAFLUOROETHYLENE AND ETHYLENE

In this work, the radiation-induced structural changes in the copolymer of tetrafluoroethylene and ethylene (F-40) were studied by X-ray photoelectron spectroscopy (XPS). During irradiation, some CF2 groups in the polymer were found to have been converted into carbon structures that bonded indirectly with fluorine atoms.

HIGH-TEMPERATURE SUPERCONDUCTOR, YBA2CU3O7-X AS ALL-SOLID-STATE LITHIUM CELL

The utility of the high-temperature superconductor, YBa2Cu3O7-x as the cathode material for an all-solid-state lithium cell has been examined. The capacity of YBa2Cu3O7-x is 223 mA h g-1 and the discharge efficiency is > 92%. Measurements of a.c. impedance show that the charge-transfer resistance at the interface of the electrolyte/cathode is very low and increases with the depth-of-discharge of the battery. Studies using X-ray photoelectron spectroscopy (XPS) reveal that the cathode becomes doped with Li+ ions as the cell discharges.

ELECTROCHEMICAL STABILITY AND ELECTROCATALYSIS BEHAVIORS OF POLY(3-METHYLTHIOPHENE) THIN-FILM MODIFIED ELECTRODES

The Electrochemical stability of poly(3-methylthiophene) (PMT) thin film modified glassy carbon electrodes was investigated experimentally with successive cyclic voltammetry(CV) The effects of electrolyte solutions on the stability were studied. In the presence of small hydrated anions (less-than-or-equal-to 3.5nm) in the solution, the electroactivity of PMT films decreased with the characteristics of second order kinetics. In a solution with large hydrated anions (greater-than-or-equal-to 4 nm), PMT films have good stability. PMT/GO electrode can electrocatalyse the oxidation of Br- and Cl- anions, and loses its electroactivity rapidly. X-ray photoelectron spectra (XPS) have demonstrated that chlorine has bonded covalently onto the PMT structure after OV cycles in NaCl solutions.

RADIATION-INDUCED CROSS-LINKING OF AROMATIC POLYMERS WITH A CARDO GROUP

The effects of irradiation on some members of the family of aromatic polymers with a cardo group, such as polyetherketone with a cardo group (PEK-C) and polyethersulfone with a cardo group (PES-C), were studied. It was found that PEK-C and PES-C can be crosslinked by irradiation under vacuum. Moreover, it was also found that the intensity of the shake-up peak of x-ray photoelectron spectroscopy (XPS) for PEK-C and PES-C varies with irradiation dose. Gelation doses (Rg) of PEK-C and PES-C were estimated from the XPS shake-up peak.

CHARACTERIZATION OF A POTASSIUM-PROMOTED COBALT MOLYBDENUM ALUMINA WATER-GAS SHIFT CATALYST

A series of potassium-promoted CoMo/Al2O3 has been investigated by means of X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and temperature-programmed reduction (TPR). CoMoO4 was found in the CoMo/Al2O3 catalyst by XRD and is destroyed by the presence of potassium. The reducibility of molybdenum is enhanced by potassium in the CoMoK/Al2O3 catalyst and is easier to reduce to Mo(IV) during sulfidation. In the oxidic state catalyst cobalt is increased on the surface by the addition of potassium. After sulfidation this phenomena disappeared, the distribution of cobalt remains at a constant level and is unaffected by the potassium content. The addition of potassium leads to a monotonical decrease of the molybdenum dispersion with the impregnating amount of potassium in the oxidic state catalyst but is more complicated after sulfidation. Potassium is well dispersed on the surface in both the oxidic and sulfided state. The activity in the water-gas shift reaction was correlated with the potassium content of CoMoK/Al2O3.

ROLE OF H2S IN THE REDUCTION OF MOO3/AL2O3

MoO3/Al2O3 is reduced at least partly by sulfur which is formed from H2S in sulfidation with H2S/N2 mixture. SO2 formation during TPD of MoO3/Al2O3 with presorbed H2S provides evidence for the explanation.

WATER-SOLUBLE AND AMPHIPHILIC POLYMERS .6. A STUDY ON THE SURFACE-COMPOSITION OF CAST FILMS OF PST/PMAA AND PEO-PST-PEO BLOCK POLYMERS BY XPS

Thin films of PSt/PMAA and PEO-PSt-PEO block polymers were deposited on a polystyrene substrate by solution adsorption (with or without solvent treatment), and the film surfaces were characterized by means of XPS. Direct solvent - casting of PEO-PSt-PEO from benzene solutions resulted in PSt-rich surfaces, whereas PMAA richer surfaces were obtained for PSt/PMAA films cast from DMF solutions. Moreover, solvent treatment after casting had profound effect on the film surface composition. Treatment with water markedly increased the surface concentration of polar PEO segments. In the case of PSt-PMAA block polymers, the PSt content on the surface increased in the order of water < ethanol < cyclohexane < petroleum ether, the last-named giving films with almost pure PSt surface. It is well worth noticing that the bulk composition had little to do with the surface composition for both PSt/PMAA and PEO-PSt-PEO block polymers within the composition range investigated when subsequent solvent treatment was applied.

STUDIES ON RADIATION EFFECTS OF PTFE .2. RADIATION-INDUCED STRUCTURAL-CHANGES AND THE TEMPERATURE EFFECT

In this work PTFE sheets irradiated with gamma-rays at 150-degrees-C and 200-degrees-C were studied using x-ray photoelectron spectroscopy (XPS). The main structural changes in PTFE due to radiation are the formation of CF3 and CF groups. An irradiation temperature dependence of the relative content of the three kinds of groups in irradiated PTFE was observed. The CF3 groups, especially when irradiation is carried out a lower temperatures, can defluorinate in the same manner as previosly reported for CF2 groups. The CF groups, on the other hand, are observed to increase with increasing irradiation dose and irradiation temperature; the latter was explained as due to an increase in branching structures.

XPS STUDY OF CORROSION BEHAVIOUR OF TITANIUM IN H2C2O4 SOLUTION

The corrosion behaviour of titanium substance and the XPS characterization of Ti surface in the H2C2O4 solution have been first studied by X-ray photoelectron spectroscopy, The experimental results show that there am mile Ti-2 and Ti2+ on sample surface in 10% H2C2O4 solution for two boars corrosion at 80 degrees C, but if corrosion is extended to 4 hones, the surface composition is mainly TiO2 with a small amount of Ti2+. This result corresponds to the structure of TiH1.642 composion in sample surface found by XRD analysis. Since bath TiO2 and the surface coating RuO2 are of Gald-Redstone structure, therefore electrode materials of Ti-Ru are stable in chemical industry.

Inhibition Effect of 2,3,5-Triphenyl-2H-tetrazolium Chloride and 2,4,6-Tri(2-pyridyl)-s-triazine on the Corrosion of Mild Steel in 1 mol/L HCl and Mechanism Study (II)

The inhibitory effect of 2,3,5-triphenyl-2H-tetrazolium chloride (TTC) and 2,4,6-tri(2-pyridyl)-s-triazine (TPT) molecules on the corrosion of mild steel in 1 mol/L HCl and microcosmic inhibitory mechanism were investigated by X-ray photoelectron spectroscopy and ellipsometry. XPS results showed that C Is and N Is peaks of TTC, C Is and N Is peaks of TPT and their integral areas were obtained, which suggested the layer of the inhibitors (TTC or TPT) should have effectively protected the mild steel surface from the corrosion; and the depression from the inhibitors for the corrosion of mild steel surface was studied using ellipsometry combined with potentiodynamic polarization and the phasic difference was gained, which displayed the inhibitory coverage of the inhibitors formed.

Characteristics of sulfide corrosion products on 316L stainless steel surfaces in the presence of sulfate-reducing bacteria

It has been found that microbial communities play a significant role in the corrosion process of steels exposed in aquatic and soil environments. Biomineralization influenced by microorganisms is believed to be responsible for the formation of corrosion products via complicated pathways of electron transfer between microbial cells and the metal. In this study, sulfide corrosion products were investigated for 316L stainless steel exposed to media with sulfate-reducing bacteria media for 7 weeks. The species of inorganic and organic sulfides in the passive film on the stainless steel were observed by epifluorescence microscope, environmental scanning electron microscope combined with energy dispersive spectroscopy and X-ray photoelectron spectroscopy. The transformation from metal oxides to metal sulfides influenced by sulfate-reducing bacteria is emphasized in this paper. (c) 2005 Elsevier B.V. All rights reserved.

Effect of nano-TiO(2)on MP-25 resin

MP-25 resin is a chlorine-containing polymer widely used in coatings. The effects of two types of nano-TiO2 (P-25 and RM301 LP) on MP-25 were studied with saline immersion, UV irradiation, and electrochemical impedance spectroscopy. UV irradiation was evaluated in terms of gloss change and X-ray photoelectron spectroscopy (XPS). The results indicate that, compared to pigment R-930 TiO2, P-25 reduced the immersion resistance and accelerated UV aging of the MP-25 coating, whereas RM301 LP showed the opposite effects. XPS analysis showed that MP-25 resin degraded under UV irradiation via dechlorination and C-C bond breakage, similarly to poly(vinyl chloride), but RM301 LP could inhibit the aging of MP-25 to a certain extent. A skin effect of oxygen and chlorine was identified in MP-25 resin by XPS. RM301 LP could improve the impedance of the MP-25 coating because of its excellent fill capacity. Hence, rutile nano-TiO2 RM301 LP represents an excellent additive for MP-25 resin. (c) 2007 Wiley Periodicals, Inc.

太阳耀斑和日食期间电离层行为的统计和模拟研究

The ionosphere is the ionized component of the Earth's upper atmosphere. Solar EUV radiation is the source of ionospheric ionization. Thus the ionosphere is affected strongly by the variations in solar radiation. Solar flares and solar eclipses can induce remarkable short time changes in solar radiation: the solar radiation would increase suddenly during solar flares and decrease significantly during solar eclipses. Solar flare and eclipse events not only affect directly the photochemical processes, but also affect the dynamic processes, and even affect the neutral atmosphere, which is strongly coupled with the ionosphere. The study on the ionospheric response to solar flares and eclipses can advance our knowledge on the ionosphere and its photochemical and dynamic processes and help us to evaluate the ionospheric parameters (such as ion loss coefficients). In addition, the study on the ionospheric responses to solar flares and eclipses is an important part of the ionospheric space weather, which can provide guides for space weather monitoring. This thesis devotes to the study on the ionospheric responses to solar flares and solar eclipses. I have developed two models to simulate the variations of solar EUV radiation during solar flares and solar eclipses, and involved in developing a 2D mid- and low-latitude ionospheric model. On the basis of some observed data and the ionospheric model, I study the temporal and spatial variations of the ionosphere during solar flares and eclipses, and investigate the influences of solar activity, solar zenith angle, neutral gas density, and magnetic dip angle on the ionospheric responses to solar flares and solar eclipses. The main points of my works and results are summarized as follows. 1. The ionospheric response to the X17.2 solar flare on October 28, 2003 was modeled via using a one-dimension theoretical ionospheric model. The simulated variation of TEC is in accordance with the observations, though there are some differences in the amplitude of the variation. Then I carried out a series of simulations to explore the local time and seasonal dependences of the ionospheric responses to solar flares. These calculations show that the ionospheric responses are largely related with the solar zenith angle (SZA). During the daytime (small SZA), most of the increases in electron density occur at altitudes below 300 km with a peak at around 115 km; whereas around sunrise and sunset (SZA>90°), the strongest ionospheric responses occur at much higher altitudes. The TEC increases slower at sunrise than at sunset, which is caused by the difference in the evolution of SZA at sunrise and sunset: SZA decreases with time at sunrise and increase with time at sunset. The ionospheric response is largest in summer and smallest in winter, which is also related to the seasonal difference of SZA. 2. Based on the observations from the ionosondes in Europe and the ionospheric model, I investigated the differences of the ionosphere responses to solar eclipses between the E-layer and F1-layer. Both the observation and simulation show that the decrease in foF1 due to the solar eclipses is larger than that in foE. This effect is due to that the F1 region locates at the transition height between the atomic ion layer and the molecular ion layer. With the revised model of solar radiation during solar flares, our model calculates the radiations from both the inside and outside of photosphere. Large discrepancy can be found between the observations and the calculations with an unrevised model, while the calculations with the revised model consist with the observations. 3. I also explore the effects of the F2-layer height, local time, solar cycle, and magnetic dip angle on the ionospheric responses to solar eclipses via using an ionospheric model and study on the solar zenith angle and the dip dependences by analyzing the data derived from 23 ionosonde stations during seven eclipse events. Both the measured and simulated results show that these factors have significant effect on the ionospheric response. The larger F2-layer height causes the smaller decrease in foF2, which is because that the electron density response decreases with height. The larger dip results in the smaller eclipse effect on the F2 layer, because the larger dip would cause the more diffusion from the top ionosphere which can make up for the plasma loss. The foF2 response is largest at midday and decreases with the increasing SZA. The foF2 response is larger at high solar activity than at low solar activity. The simulated results show that the local time and solar activity discrepancy of the eclipse effect mainly attribute to the difference of the background neutral gas density. 4. I carried out a statistical study on the latitudinal dependence of the ionospheric response to solar eclipses and modeled this latitudinal dependence by the ionospheric model. Both the observations and simulations show that the foF2 and TEC responses have the same latitudinal dependence: the eclipse effects on foF2 and TEC are smaller at low latitudes than at middle latitudes; at the middle latitudes (>40°), the eclipse effect decreases with increasing latitude. In addition, the simulated results show the change in electron temperature at the heights of above 300 km of low latitudes is much smaller than that at the same heights of middle latitudes. This is due to the smaller decrease in photoelectron production rate at its conjugate low heights. 5. By analyzing the observed data during the October 3, 2005 solar eclipse, I find some significant disturbances in the conjugate region of the eclipse region, including a decrease in Te, an increase in foF2 and TEC, and an uprising in hmF2. I also simulated the ionosphere behavior during this eclipse using a mid-low latitude ionospheric model. The simulations reproduce the measured ionospheric disturbances mentioned above in the conjugated hemisphere. The simulations show that the great loss of arriving photoelectron heat from the eclipse region is the principal driving source for the disturbances in the conjugate hemisphere.

Epoxidation of propylene on NaCl-modified silver catalysts with air as the oxidant

Propylene epoxidation by air was carried out on NaCl-modified silver (NaCl/Ag) catalysts, and the catalysts were characterized by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The effects of NaCl loadings, propylene to oxygen ratio, and the reaction time on the catalytic performance were investigated. It was found that the addition of NaCl to silver significantly increases the propylene oxide (PO) selectivity. The PO yield has a maximum when the NaCl loading is about 10 wt.%. Also 12.4% conversion of propylene and 31.6% selectivity to PO are obtained on the NaCl/Ag (10 wt.%) catalyst at 350 degreesC, space velocity 1.8 x 10(4) h(-1) and C3H6:O-2 = 1:2. XPS and XRD characterizations show that AgCl formed on the silver catalyst was favorable to propylene epoxidation. A compound with highly oxidized Ag ion was also found, which may be effective for the reaction. (C) 2002 Elsevier Science B.V. All rights reserved.

Coadsorption of nitric oxide and oxygen on the Ag(110) surface

The coadsorption of NO and O-2 on Ag(110) surface has been studied by X-ray photoelectron spectroscopy (XPS), ultraviolet photoelectron spectroscopy (UPS) and in situ Raman spectroscopy. The existence of oxygen enhances the adsorption of NO by forming the NOx species, that is, NO2 and NO3, and the NO in turn as a promotor facilitates the cleavage of the dioxygen bond, forming the surface atomic oxygen species having the same spectral characteristics as those produced using oxygen at high pressure. The oxygen species generated by the interaction is composed of two parts. One is produced directly by the decomposition of surface NO-O-2 complex at ca 625 K, which raised an O 1s feature at 530.5 eV and is absent at ca 800 K, while the another with an O 1s binding energy of 529.2 eV emerges at higher temperatures and shows similar properties as the reported gamma-state oxygen which bound tightly on restructured silver surface. The exposure to NO and O-2 causes noticeable changes in the morphology of the Ag(110) surface and the flat terraces superseded by small (ca 0.1 mu m) pits, and particles with typical diameters of a few micrometres were formed at elevated temperatures. (C) 1999 Elsevier Science B.V. All rights reserved.