Rare earth doped Lu2SiO5 thin films have been prepared by combining sol-gel process and spin coating. Annealing treatment results in the crystallization of the film and efficient incorporation of rare earth doping ions. XPS and RBS spectrocopies showed that the composition of the films is close to the nominal one. Adventitious carbon has been observed and attributed to incomplete pyrolysis of metal-organic precursors. XPS concentrations profiles show a good homogeneity for the films. RBS demonstrated some inter-diffusion between amorphous carbon substrate and silicate films resulting in a gradient of carbon at the interface between the substrate and the film itself.

Rare earth doped LuBO3 thin films have been prepared by combining sol-gel process and coating techniques such as spin coating and spray pyrolysis. Annealing treatment results in the crystallization of the film as vaterite phase and incorporation of the doping ions in solid solution. XPS and RBS spectroscopies showed that the composition of the films is close to the nominal one. Adventitious carbon has been observed and attributed to incomplete pyrolysis of metal-organic precursors. XPS concentration profiles show a good homogeneity for the films. RBS demonstrated some inter-diffusion between amorphous carbon substrate and borate films resulting in a gradient of carbon at the interface between the substrate and the film itself. Finally scintillation spectra have been recorded and demonstrate the potentiality of these films to be used as X-ray intensifying screens.

Plasma sprayed coatings have been investigated as field emission cathodes. The tested materials were Al2O3+13%TiO2, Al2O3+40%TiO2, TiO2. Some of these coatings were laser engraved. The samples used were initially prepared for purposes other than field emission and their components and structures were not optimised for electron emission. The emission properties were evaluated from current-voltage characteristics taken in a diode configuration in a vacuum chamber under a pressure of 1x10(-6) Pa. Preliminary results indicate that some layers are good field emitters (threshold field 1x10(7) V/m for Al2O3+13%TiO2). The emission stability was generally good and the emission curves were similar on repetition. No significant hysteresis in I-V plots for "up-and-down" measurements was noticed. A model of possible mechanism of low microscopic field emission is presented and microstructural investigations using techniques of XRD, Raman spectroscopy and SEM techniques of plasma sprayed and laser engraved layers enabled understanding of increase of field enhancement factor.

While boria-alumina mixed oxides have been widely used for various catalytic reactions, their structure has never been satisfactory elucidated and is still a matter of debates. The present paper deals with the elucidation of the structure of boria-alumina prepared by a sol-gel method with B/Al atomic ratio varying from 0.013 to 1.643. The powders were prepared by hydrolysis of aluminum tri-sec-butoxide in the presence of (NH4)(2)B4O7 center dot 4H(2)O. Then, the solid-state magic angle spinning (MAS) NMR spectroscopy was used to characterize the obtained solids in the dried state (xerogels), the calcined state being the object of a next paper. Both Al-27 and B-11 MAS NMR spectra were recorded with subsequent simulation of these last ones. This allowed to build a consistent structural model of these xerogels, taking into account the evolutions of calculated parameters such as the quadrupolar interaction, the real chemical shift, and the relative quantity of, respectively, BO3, BO4, tetrahedral, pentahedral, and octahedral aluminum species as a function of the B/Al atomic ratio. As a result, it was found that, for B/Al < 0.06, presence of boron induces the creation of bulk and surface tetrahedral aluminum species. Then, for B/Al > 0.06, BO3 chains attached to these tetrahedral aluminum species are formed and start to grow through the matrix. Further, for B/Al > 0.15, when the boron loading increases, the B 03 chains progressively emerge outside of the matrix, crossing it over. Furthermore, for B/Al > 0.26, some pentahedral aluminum species are formed supposedly due to the considerable steric strains afforded by some particular aluminum atoms. In brief, the presented model elucidates the structure of the dried alumina-based xerogels and is the key starting point to explain the structure of the oxides obtained after calcination and presented in the following paper.

Metallic, oxide and hydroxide environments of magnesium are clearly identified by X-ray photoelectron spectroscopy from chemical shift of Mg 1s and Mg 2p photopeaks. Unfortunately, Mg3N2 cannot be distinguished from MgO through these two peaks. In this work, we give evidence that it is possible to unambiguously identify magnesium nitride from magnesium oxide thanks to a Mg Auger parameter defined as the difference between the kinetic energy (KE) of the Mg K L L Auger peak and the KE of the Mg 1s peak. The value obtained for Mg3N2 (1000.0 eV) is quite different from the one observed for MgO (998.6 eV). Values obtained for metallic Mg and for Mg(OH)2 are, respectively, equal to 1004.2 and 997.5 eV. This parameter is then used in order to characterize the modification of the Mg chemical environment in the Al-5083 aluminum alloy (containing 4.5 at.% Mg) nitrided by a distributed electron cyclotron resonance nitrogen plasma.

The paper deals with the investigation of microstructure of plasma sprayed and laser engraved coatings of TiO2 and Al2O3–TiO2 of two compositions (13 and 40 wt.% TiO2). The samples preparation technology includes also grinding and polishing prior to laser treatment. Transformations of crystal phases, present in initial powders, at all technological steps were investigated using X-ray diffraction (XRD) and Raman spectroscopy. Quantitative chemical analysis was carried out using X-ray photoelectron spectroscopy (XPS). Finally, morphology of powders and coatings surfaces and sections were investigated using scanning electron (SEM) and optical microscope (OM).

A Far Cold Remote Nitrogen Plasma is used both to fluidize and to treat a polyethylene powder in order to increase its hydrophilic character. The evolution of the wettability of the powder as well as the one of its physical (density, particles size distribution, average diameter, shape factor, and BET surface area) and flow properties (angle of repose, angle of slide, and Hausner index) are determined versus various experimental conditions. It is shown that the plasma treatment efficiency is strongly dependant on the oxygen content of the nitrogen flow and on the velocity of fluidizing gas. Best wettability is obtained by the addition of 0.75% of O2 in the nitrogen plasma gas and with a high gas velocity. It is also evidenced that the flowability of the powder is slightly altered by the plasma treatment.

Surface modifications of bulk and supported palladium catalysts have been investigated between 25 and 300 °C under controlled atmospheres in the presence of 5×10−3atm NO and/or 5×10−3atm CO by means of in situ Raman spectroscopy. The evolution of the Raman spectra of bulk and alumina supported palladium under NO reflects the ability of Pd to dissociate adsorbed NO molecules. The subsequent accumulation of oxygen atoms leads to the ultimate formation of subsurface oxygen species and/or PdO islands. Successive NO and CO adsorptions on 1wt% Pd/Al2O3 lead to an oxidised or reduced palladium surface, respectively. On the other hand when CO and NO are simultaneously introduced, the competitive adsorptions between these two reactants, more in favour of NO, lead to an irreversible formation of PdO. These observations have been discussed in the light of mechanistic aspects obtained from previous kinetic investigations.

In the past few years, vapour phase Beckmann rearrangement of cyclohexanone-oxime to caprolactam has been investigated in depth and a wide variety of catalysts has been studied. To date a large number of experiments concerning non-zeolitic supported boron oxides have been carried out. In the present work, we report on boria-alumina catalysts where the boron is part of the catalyst lattice, these catalysts being tested for the cyclohexanone-oxime vapour phase rearrangement to caprolactam. These catalysts are obtained by the sol–gel route using (NH4)2B4O7 as the source of boron, which has never been used before in B/Al sol–gel synthesis. The local environment of catalysts was characterised by solid state 27Al- and 11B-MAS-NMR and their structure by X-ray powder diffraction; the acidity was determined by TPD of ammonia. The effect of B/Al ratio and the role of different polar agents in the feed were also investigated by catalytic tests.

Correlations between in situ Raman spectroscopic and catalytic measurements on palladium based three-way catalysts during the reduction of NO by CO have been tentatively established. Particular attention to the selectivity towards the transformation of NO into N2O has been paid in order to explain why N2O is the main N-containing product during the engine cold start. A comparative study of the selectivity from temperature-programmed and steady-state experiments on bulk and supported palladium catalysts shows that bulk Pd is significantly more selective towards the production of N-2 than Pd/ Al2O3 at low conversion and low temperature. In addition, the subsequent reduction of N2O by CO occurs more readily on bulk palladium. In parallel to this catalytic information, Raman spectra recorded in comparable experimental conditions reveal different spectral features relative to the nature of chemisorbed species, and to the development of surface PdO islands mainly on Pd/ Al2O3. Both differences have been compared and discussed in the light of a previous mechanism proposed earlier in the literature.

Transition alumina with both high specific surface area (SSA) and quite important pore volumes deserve some interest in the field of heterogeneous catalysis as such alumina can be used as supports for different active phases, namely those used in hydroprocessing reactions. Alumina has been synthesised by a sol-gel method for which a key parameter, examined in this study, is the introduction of chelating agents such as butan-1,3-diol or acetylacetone (Hacac) in the aluminium-tri- sec butylate (ASB, the chosen Al precursor) solution. The study of the complexation chemistry for a complexing agent/Al alkoxide molar ratio ( C ) equal to 1, 2 and 3 was carried out. Some species in initial solutions were identified by IR and 27 Al NMR spectroscopies, and the dried solids were characterised by the combined use of elemental analysis, XRD and IR spectroscopy. After hydrolysis of the precursor, the dried solids exhibited the boehmitestructure, more or less crystallised whatever the C ratio when butan-1,3-diol was used whereas a formulation Al(acac)(OH) 2 was obtained when Hacac was introduced with a ratio C = 1. It has been shown that the increase in the C ratio up to 2 or 3 induces the precipitation of well-defined Al(acac) 3 particles before hydrolysis. This compound was also present in small quantities in the dried gel for C = 1. After calcination at 500°C, more or less well crystallised γ-alumina was obtained. Compared to those of the reference alumina, the textural parameters are strongly modified by the use of a complexing agent. Moreover, Hacac has a stronger effect than butane-1,3-diol on the textural characteristics of the support.

Nitrous oxide (NO) adsorption and the CO + NO reaction have been investigated on bulk and alumina‐supported Pd catalysts by XPS at various temperatures between 25 and 300°C with P NO in the 0.5–5.0 (×10 −2 ) atm range and P CO = 5 × 10 −3 atm. A catalytic reactor settled in the preparation chamber coupled to the spectrometer allows surface changes occurring under catalytic conditions on these catalysts to be characterized. Various nitrogen‐containing species have been detected, which depend on the oxidation state of Pd. The results have been explained tentatively in the light of a mechanism proposed for NO transformation. Copyright © 2002 John Wiley & Sons, Ltd.

A far cold remote nitrogen (FCRN) plasma, eventually doped with oxygen, was used to modify the surface properties of a polyethylene (PE) powder. The process associates both remote plasma and fluidized bed technologies. Two applications are described. The first one, for increasing the hydrophilic character of PE, only requires a single plasma treatment. The second application involves FCRN plasma polymerization of 1,1,3,3-tetramethyldisiloxane mixed with oxygen to obtain a hydrophobic film on the powder surface. The wettability evolution of the PE powder was followed by contact angle measurements (Washburn method) versus different experimental parameters. The surface modifications induced by the treatments were studied by XPS. Copyright (C) 2002 John Wiley Sons, Ltd.

Abstract— We present the results of irradiation experiments aimed at understanding the structural and chemical evolution of silicate grains in the interstellar medium. A series of He+ irradiation experiments have been performed on ultra‐thin olivine, (Mg,Fe)2SiO4, samples having a high surface/volume (S/V) ratio, comparable to the expected S/V ratio of interstellar dust. The energies and fluences of the helium ions used in this study have been chosen to simulate the irradiation of interstellar dust grains in supernovae shock waves. The samples were mainly studied using analytical transmission electron microscopy. Our results show that olivine is amorphized by low‐energy ion irradiation. Changes in composition are also observed. In particular, irradiation leads to a decrease of the atomic ratios O/Si and Mg/Si as determined by x‐ray photoelectron spectroscopy and by x‐ray energy dispersive spectroscopy. This chemical evolution is due to the differential sputtering of atoms near the surfaces. We also observe a reduction process resulting in the formation of metallic iron. The use of very thin samples emphasizes the role of surface/volume ratio and thus the importance of the particle size in the irradiation‐induced effects. These results allow us to account qualitatively for the observed properties of interstellar grains in different environments, that is, at different stages of their evolution: chemical and structural evolution in the interstellar medium, from olivine to pyroxene‐type and from crystalline to amorphous silicates, porosity of cometary grains as well as the formation of metallic inclusions in silicates.

Aluminum and silicon samples were nitrided by a distributed electron cyclotron resonance nitrogen plasma. The plasma conditions used for the treatment correspond to a maximum N2+ concentration in the sample position, determined by optical emission spectroscopy. The substrates were always polarized by a DC bias voltage at −120 V and were externally heated or not. Nitrided samples were characterized by X-ray photoelectron spectroscopy (XPS) after an exposure to ambient air. A depth profile of the treated substrates was achieved by Ar+ etching sequences in the XPS spectrometer. When the samples are polarized and heated at 500°C during the plasma treatment, the nitride layer (dense AlN or Si3N4 and diffusion layers) obtained on aluminum (∼0.3 μm) is much thicker than on silicon (∼30 Å).

A structural characterization of PbO–PbCl2–CdCl2 oxychloride glasses was achieved using 207Pb and 113Cd nuclear magnetic resonance (NMR) and X-ray photoelectron spectroscopy (XPS). 207Pb static NMR spectra exhibit two broad components, whose intensity change with oxygen–chlorine substitution in the glass composition. 207Pb phase-adjusted spinning sidebands (PASS) NMR shows that the lead first co-ordination sphere in PbO–PbCl2–CdCl2 glasses contains both oxygen and chlorine atoms and that the Pb bonding environment varies from an ionic environment to a more covalent bonding state. From the study of crystalline Pb3O2Cl2, the correlation between 207Pb isotropic and anisotropic chemical shift is extended to oxychloride compounds. Oxygen 1s photoelectron spectra contain two components that are consistent with a glass formation through Pb–O–Pb bonds. 113CdNMR spectra show that Cd is mainly ionically bonded to chlorine and acts as network modifier for all glass compositions.

The reactive pulsed laser deposition technique was used to deposit carbon nitride (CNx) coatings on a silicon substrate. In this process, an infrared transversely excited atmospheric pressure CO2 laser ablation of a graphite target in a remote nitrogen plasma afterglow was used to provide simultaneously both carbon- and nitrogen-containing species. Evidence of different CN bonding configurations has been observed in the deposited coatings. For nitrogen pressures (P-N2) of greater than or equal to 700 Pa there is an increase in the contribution of sp(2) carbon atoms that is associated with graphitization of the CN, coatings. For P-N2 increasing from zero to 100 Pa, the comparison between XPS core-level and valence band spectra of the CN, coatings shows good correlation between the p-derived states (C 2p electrons) of C-C pi bonds in the valence band and the sp(2) carbon atom concentration deduced from the C 1s spectra.The progressive positive contribution of nitrogen lone pair electrons to the valence band is consistent with the increase of the N-C sp(3) contribution with P-N2. The decrease in the sp(2) carbon atom contribution is associated with the increase of the nitrogen concentration in the coatings. Copyright (C) 2001 John Wiley & Sons, Ltd.

Abstract The sections in this article are Introduction Infrared Spectroscopy IR Characterization of Surface Properties of Metal Oxides Information Deriving from the Activated Oxide Spectra Lattice Vibrations Surface Oxide Sites Identification of Main Impurities in Metal Oxides Electronic Transitions Hydroxyl Groups Information Deriving from Probe Adsorption Acidity Basicity Cationic and Redox Sites: Use of Methanol as Probe for Local Arrangement and Oxidation State Determination of Surface Cationic Sites IR Characterization of Oxide and Sulfide Supported Catalysts Information Deriving from the Spectrum of the Activated Catalyst Information Deriving from Probe Molecule Adsorption CUS Characterization of the Sulfided Phase B rønsted Acid Site Characterization of the Sulfided Phase Site Transformation in the Presence of H 2 Surface Characterization and Catalysis Conclusion R aman Spectroscopy General Considerations Bulk Oxide Catalysts Supports Supported Oxides Nature of the Supported Oxide Chemical Processes Involved During Catalyst Synthesis Adsorption of Probe Molecules Surface B rønsted and Lewis Acid Sites Adsorption of Molecules Acting as Reagents Active Phase: Genesis and Characterization Genesis of the Hydrodesulfurization Active Phase Sulfided Catalyst Catalyst Reactivity Conclusion Concluding Remarks and Outlook