Ni supported on activated carbon as catalyst for flue gas desulfurization

A series of Ni supported on activated carbon are prepared by excessive impregnation and the desulfurization activity is investigated. It has been shown that the activated carbon-supported Ni is an efficient solid catalyst for flue gas desulfurization. The activated carbon treated by HNO3 exhibits high desulfurization activity, and different amounts of loaded-Ni on activated carbon significantly influence the desulfurization activity. The catalysts are studied by X-ray diffraction (XRD) and X-ray photoelectr...     

Oxygen removal from raw silicon powder by the HF‐ethanol solution etching

Silicon powder is vulnerable to oxidation due to its high surface activity. The as‐prepared Si powder is characterized by X‐ray photoelectron spectroscopy spectra coupled with an oxygen nitrogen analyzer, revealing that oxygen impurities mainly consist of Si oxides but with a small amount of free oxygen. The stable oxide films can deteriorate the properties of sintered materials since they cannot be removed during sintering process. The cleaning of these oxides by a single‐HF solution is not straightforward and efficient due to the large surface tension. To remove the oxygen, a more efficient way with the addition of ethanol to a HF solution has been proposed. The addition of a moderate percent of ethanol can decrease the water contact angle and then improve the cleaning efficiency. Importantly, the resulting Si powder possesses good dispersity, uniformity and fluidity. However, excess hydrofluoric acid suppresses oxide removal. Copyright © 2012 John Wiley & Sons, Ltd.     

Effect of surface hydroxyl concentration on the bonding and morphology of aminopropylsilane thin films on austenitic stainless steel

The adsorption of 3‐aminopropyltrimethoxysilane thin films on Fe? 18Cr? 7Mn? 3Ni (austenitic stainless steel) was investigated by X‐ray photoelectron spectroscopy (XPS) and inelastic electron background analysis. The bonding and morphology of the films were strongly dependent on the surface hydroxyl concentration, which was controlled by the oxidation pretreatment of the substrate. In particular, an aminopropylsilane (APS) monolayer with high degree of bonding to the substrate was obtained on an electrochemically passivated surface with very high hydroxyl concentration. On the other hand, the deposition of weakly bound APS clusters was observed on substrates having relatively low hydroxyl concentrations. The adsorption occurred initially via hydrogen bonding, whereas heating to 373 K resulted in the formation of covalent Si? O? M bonds at the silane/metal oxide interface. The results of this study provide insight into the interaction between silanes and stainless steels surfaces, and can be applied for functionalization of stainless steel materials in an extensive range of applications. Copyright © 2010 John Wiley & Sons, Ltd.     

Kinetics of radiation-induced carbonization of poly(vinylidene fluoride) film surface

The kinetics of radiation-induced carbonization of PVDF surfaces aiming at carbyne (one-dimensional carbon allotrope) synthesis have been studied. A sample of poly(vinylidene fluoride) film was exposed to Mg Kα radiation (?ω = 1253.6 eV) in an ESCALAB Mk II spectrometer for 14 h with the aim of surface carbonization. Some 221 spectra of C 1s electrons were measured and expanded using 7 Gaussian curves to reveal and identify species being created on the film surface during its carbonization. A decrease in the content of CF₂ groups, the emergence of CF species in two different states, and growth of a number of fluorine-free carbon atoms have been detected. Simultaneous variations of CH/CH₂, CF and CF₂ peaks suggest elimination of H and F atoms as HF. A proposed model shows three probabilistic factors affecting the rate of degradation, one of which remains uncertain.     

Surface chemical composition of human maxillary first premolar as assessed by X-ray photoelectron spectroscopy (XPS)

The surface chemical composition of dental enamel has been postulated as a contributing factor in the variation of bond strength of brackets bonded to teeth, and hence, the probability of bracket failure during orthodontic treatment. This study systematically investigated the chemical composition of 98 bonding surfaces of human maxillary premolars using X-ray photoelectron spectroscopy (XPS) to ascertain compositional differences between right and left first premolars. The major elements detected in all samples were calcium, phosphorus, oxygen, nitrogen and carbon. Surface compositions were highly variable between samples and several elements were found to be highly correlated. No statistical significant difference in the chemical composition of the maxillary right and left first premolars was found (p > 0.05). Knowledge of the chemical composition of enamel surfaces will facilitate future studies that relate this information to the variations in dental enamel bond strength.     

Study of ammonium fluoride passivation time on CdZnTe bulk crystal wafers

The chemical etching and the passivation processes of CdZnTe wafers were studied. The treatment effects were tested through an X‐Ray Photoelectron Spectroscopy (XPS) analysis and I–V measurement. The chemical etching in 2%Br–MeOH solution may effectively remove the damaged layer and improve the ohmic contact between CdZnTe wafer and Au electrodes making rich the surface with Te. After different etching times, the CdZnTe wafers were passivated with NH₄F/H₂O₂.CdZnTe wafer passivated immediately after etching showed the best passivation efficiency because the enriched Te on the surface was fully oxidized to TeO₂, which results in the thickest oxide layer, and the most stoichiometric surface. Also the surface leakage current was reduced in comparison with the sample passivated 24 h after etching. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Sodium Ion-Selective Chalcogenide Glass Electrodes

Abstract

Analytical characteristics and sensing mechanism of sodium ion-selective electrodes based on NaCl-Ga₂S₃-GeS₂ glasses have been investigated. Chalcogenide glass electrodes containing 10 mol.% NaCl in the membrane showed near-Nernstian response in the concentration range from 10-³ to 1 M sodium nitrate solution. These sensors were superior to the conventional pNa oxide glass electrodes in selectivity in the presence of hydrogen ions and in Na⁺ ion sensitivity in fluoride media. Prolonged solution treatment for several days reduces, however, the detection limit of the sensors and the slope of the electrode response. Ionic processes at the membrane surface have been investigated using XPS technique and ²²Na tracer measurements. It was shown that sodium ion-exchange governed Na⁺ ion response of chalcogenide     

Decomposition of poly(amidoamine) (PAMAM) dendrimers under O2 plasma conditions

Results of FTIR and XPS measurements of bulk and γ-Al₂O₃-supported fourth generation hydroxyl-terminated (G4OH) poly(amidoamine) (PAMAM) dendrimers during O₂ plasma treatment at room temperature indicate that such treatment can effectively decompose the structure of the dendrimer. No new functionalities appear in the dendrimer structure during such treatment, but instead fragmentation of this structure is taking place. The dendrimer backbone likely disintegrates into small molecules (i.e., NO_x, CO, CO₂) which in the case of the supported dendrimers interact with the γ-Al₂O₃ support and form surface nitrate and carboxy species. Subsequent treatment in H₂ at 300 °C leads to the complete removal of the nitrogen-containing species from the surface of γ-Al₂O₃. However, carbon-containing species still remain on the surface in relatively small amounts. Finally, XRD measurements further show that the crystallinity of the support is not affected substantially by the O₂ plasma treatment.     

Optimization of cryo‐XPS analyses for the study of thin films of a block copolymer (PS‐PEO)

The water‐induced surface reorganization of a thin film of a block copolymer [polystyrene‐b‐poly(ethylene oxide), PS‐PEO], was studied by cryogenic X‐ray photoelectron spectroscopy (cryo‐XPS). Experimental parameters were examined with a view to optimize the analysis. The absence of artifacts due to the low temperature of analysis was checked, and the influence of the procedure used for sample hydration before analysis was investigated. Adequate timing of the different steps of the analysis and temperature program was also established. With this optimized protocol, an important reorganization of the block copolymer was detected, showing more pronounced exposure of the PEO block at the outermost surface in hydrated compared to dry environment. As this type of polymer surface is prone to be used for biomedical applications, an accurate knowledge of the chemical composition of the outermost surface in aqueous environments is crucial. The development of this technique is therefore promising for related systems. Copyright © 2011 John Wiley & Sons, Ltd.     

Influence of air plasma treatment at atmospheric pressure on wood extractives

The influence of an atmospheric pressure plasma treatment on wood extractives has been investigated by means of surface energy determination and XPS. Polar and disperse component of the surface energy show only marginal influence of plasma treatment, whereas XPS indicates plasma induced oxidation and degradation of the extractives.