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Corrosion studies on ancient metallic objects are performed with the aim of evaluating their stability for a very long term. They have crossed centuries and should be transmitted in good shape to future generations. They are generally protected from aggressive conditions by a layer formed by corrosion products and this layer stability has to be checked. This work intends to show that coupling an in situ technique like Raman spectroscopy to electrochemical measurements allows a mechanism of corrosion layer formation and stability to be proposed. For bronze the beneficial presence of tin IV oxide to slow down copper corrosion is evidenced. For steel, the hypothesis of lepidocrocite reduction to be coupled with iron corrosion is infirmed.

The catalytic activity in complete benzene oxidation (CBO) over gold catalysts supported on titania and ceria was studied. As promoters either vanadia or molybdena were applied, it was established that gold catalysts supported on ceria exhibit higher activity than those supported on titania. In the case of ceria as a support the catalytic activity of molybdena promoted gold catalyst was higher in comparison to the vanadia promoted one. When titania was used as a support the molybdena promoted sample exhibits much less activity than that promoted by vanadia. The catalytic activity results were in accordance with the data obtained by the TPR and Raman spectroscopy measurements. A good correlation between CBO and reduction activities of the catalysts was found.

An unknown corrosion process producing dendrites was recently found to take place at copper patterns immersed in oxalic acid aqueous solutions in the course of the post-chemical–mechanical polishing of integrated microcircuits (ICs). We report here investigations of this corrosion phenomenon in ICs using atomic force microscopy (AFM), cyclic voltammetry and Raman spectroscopy. AFM first allowed an accurate morphological characterisation of the copper patterns and their surroundings while cyclic voltammetry was used to identify their electrochemical reactivity in oxalic acid aqueous solutions. In situ AFM experiments carried out in this same aqueous media in open circuit conditions unambiguously showed a progressive and partial dissolution of copper patterns as well as the formation of a ring type structure. Raman spectroscopy was used on gold supported electrogenerated copper films to identify the precipitation or adsorption products resulting from the electrochemistry of the copper/oxalic acid system as a function of the applied potential and the pH of the oxalic acid aqueous solutions. The collected results rather suggest a two-step galvanic corrosion phenomenon involving the tantalum barrier, copper seed layer and electrodeposited copper.

The purpose of this study is to examine the risks of atmospheric corrosion of steel waste canisters following their deep geological disposal in the temperature range from 303 to 363 K. The work was performed using iron samples deposited as thin films on a quartz crystal microbalance (QCM) and disposed in a climatic chamber. The experiments showed that, in the temperature under study (298–363 K), the mass increase due to the formation of oxide/hydroxide rose sharply above 70% R H , as is commonly observed at room temperatures, indicating that the phenomenon remains electrochemical in nature. Ex situ Raman spectrometric analyses indicate the formation of magnetite, maghemite and oxyhydroxides species in the 298–363 K temperature range, and for oxygen contents above 1 vol.%, whereas only Fe 3 O 4 and γ-Fe 2 O 3 are detected at 363 K. In this work, the kinetics of the rust growth is discussed, on the bases of the rate of mass increase and of the composition of the rust, as a function of the climatic parameters and the oxygen content of the atmosphere.

The electropolymerization of o-anisidine leads to the formation of a polymer which is in the same time strongly oxidized and charged in a large potential range: the poly-o-methoxyaniline (POMA). The POMA Raman features are strongly different from the polyaniline (PANI) ones; in particular a new band, absent from the PANI spectrum, prevails in a large potential range. The nature of the polymer structures obtained in function of the polarization potential is discussed from their Raman spectra. A new polymeric configuration of the oxidized/charged rings is therefore described.

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A bronze coin datable of the post-Roman empire and discovered in Morocco was studied. The in-depth structure and the composition of both patina and substrate alloy were determined by SEM observations, EDS (elemental dispersion analysis using X-ray) cartographies and Raman spectroscopy on a cross-section. The composition of the patina and that of the substrate alloy were found to be highly heterogeneous. Some patina particles were also scraped off from coin surface. Their electrochemical properties were characterized by cyclic voltammetry and electrochemical impedance spectroscopy with a cavity microelectrode. Cyclic voltammetry revealed the presence of three cathodic current peaks. In situ Raman microspectroscopy on the microelectrode allowed the attribution of two of them to Cu(0)|Cu(I) and Cu(I)|Cu(II). The third one was ascribed to the presence of lead oxide. Moreover, it was observed that tin dioxide initially present in the patina gradually disappeared independently of the potential cycling. This phenomenon was explained by the dissolution of this species through a chemical process. The impedance spectra collected with the cavity microelectrode were simulated suitably with an oxidation–reduction reaction coupled with a hemispherical diffusion model of dissolved oxygen.

The kinetics of tarnishing formation was examined on a polished silver dipped in a 10 mM Na2S. The recovery of an initial bright surface was then obtained by cathodic reduction of the tarnish layer in a 5% sesqui-carbonate solution. Two protection methods to prevent a further formation of a dark deposit were tested: an electrodeposited poly(amino-triazole) film and the surface treatment in hexadecane-thiol. The protection by poly(amino-triazole) is not reliable for all nuances of silver. In contrast, the film formed with hexadecane-thiol showed satisfactory properties. The formations of tarnish and protective films were examined by electrochemical methods, the reflectance measurements, and the quartz crystal microbalance.

The structural and electronic characteristics of substituted polyanilines (PANI) were studied in order to understand why substituents on the aniline ring enhance, or not, the protection of iron against corrosion with respect to the protection given by an unsubstituted polyaniline layer. The substituent can modify the polaronic nature (localized or delocalized polaron, bipolaron) of polyaniline. “Electron donor” or “electron acceptor” substituents were therefore compared without leading to a definitive conclusion.

In situ Raman spectroscopy was used to study the redox modifications of electropolymerized polypyrrole (Ppy) films used as protective coatings on iron. A preliminary study of the redox behavior of Ppy on platinum was carried out for highlighting the most sensitive bands to potential variations: the 1560–1620 cm −1 as well as the 930 and 980 cm −1 peaks show a strong dependence on the applied potential. In situ Raman spectra of Ppy on iron were recorded at different times after immersion in a 3% NaCl solution. They formally display the same peaks as those found for platinum, allowing to characterize the redox state of the Ppy film at the solution/film interface. Additional ex situ Raman spectra allowed to identify the corrosion products at the Ppy/metal interface. These results complement kinetics analysis early developed to understand the protection mechanism and its loss.

Electrochromic TiO 2 anatase thin films on ITO were prepared by the sol–gel dipping method using a solution of titanium tetraisopropoxide, diethanolamine and ethanol. The films were transparent in the visible range and can be colored in a solution of LiClO 4 in propylene carbonate. The transmittances of the colored films were found to be strongly dependent on the Li + inserted charge. Combining the experimental data obtained from in situ Raman and in situ transmittance spectra with the data from chronoamperometic measurements, it was demonstrated that the fully colorated state of the TiO 2 anatase films is Li 0.5 TiO 2 with a crystalline structure of Imma space group symmetry. In the Raman spectra this coloration state exhibits five characteristic bands at 176, 224, 316, 531 and 629 cm −1 .

Novel, composite silver/titania immobilized on glass substrates were prepared, characterized and their photocatalytic activity was evaluated. The undoped original material consists of rough, high surface area nanocrystalline titanium dioxide (TiO2) thin films. To increase their efficiency, the TiO2films were modified by silver cations deposition and subsequent UV-C irradiation. SEM pictures confirmed the existence of an open porous network of interconnected titania particles on the semiconductor surface. AFM analysis proved the presence of spherical silver particles on the catalyst surface and provided quantitative surface parameters as fractal dimension, surface roughness and mean particle diameter. Spectroreflectometry showed the presence of an increase in optical absorbance attributed to plasmon resonance absorption of the silver clusters. The photocatalytic properties of the surface modified materials were investigated through photodegradation of Methyl Orange. The silver deposition conditions were optimized for maximum photocatalytic efficiency and crucial parameters such as dipping period, UV irradiation time, and concentration of the dipping solution were determined. The optimum silver nitrate concentration of the dipping solution was found to be10-3M. This silver doped photocatalyst decomposes the azo-dye pollutant 3-times faster than the un-doped Degussa P25TiO2film. A concentration increase results in a decrease of the films photocatalytic performance. Strength and reproducibility tests proved that the photocatalytic activity of the silver doped titania was perfectly reproducible.

In situ Raman analysis was applied to identify the corrosion products formed on iron coated with epoxy-amine varnish and exposed to sodium chloride solution saturated by hydrogen sulfide or carbon dioxide. The results showed the formation of iron sulfide or iron carbonate layer while electrochemical impedance spectrum predicted the polymer coating exhibiting an almost perfect protecting barrier property. It is concluded therefore, that the corrosion process involves the permeation of water and hydrogen sulfide at molecular state through polymer interstices whereas no ionic conduction is allowed to take place in the coating film. The corrosion process induces the complete delamination of the exposed coating area but as far as its integrity is respected (no macroscopic pores or crevices) the corrosion rate is very low, far from that expected from permeation measurements of H2S.

The electrochemical behaviour of pure aluminium in citric acid solution was investigated with a rotating disk electrode (RDE) at the open circuit potential (OCP), in the presence and in the absence of chloride, using electrochemical impedance spectroscopy and Raman spectroscopy. The impedance diagrams are composed of four frequency domains: at very high frequency (VHF), a Warburg-like behaviour was attributed to the porosity effect of the external part of the oxide layer. A slightly depressed capacitive loop at high frequency (HF) was explained as the combination of two capacitive loops, one corresponding to the same phenomenon as in the VHF domain but insensitive to the porosity (barrier layer resistance in parallel to the oxide film capacity), the other one to the charge transfer resistance in parallel to the double layer capacity. An inductive loop at low frequencies (LF) appeared as due to the relaxation of oxygen species adsorbed at the film ∣ solution interface, while the very low frequencies (VLF) capacitive loop was ascribed to the coverage relaxation of adsorbed citrate species. Possible modulation of the passive layer thickness was also envisaged as a phenomenon at the origin of this latter loop. The diagrams shape is also insensitive to the addition of 104 ppm chloride ions to the solution, even though a diameter decrease of the HF capacitive loop is observed together with an increase of the frequency response. Raman Spectroscopy showed that citrate ions adsorb strongly to the electrode surface and that the time scale of this process is consistent with the frequency domain observed for the VLF capacitive loop. The interaction of citrate with the oxide layer is hindered by the addition of chloride ions to the electrolytic solution.

TiN (4.5 nm)/AlN (3, 6, 22 nm) superlattices deposited by DC magnetron sputtering on MgO(001) at a temperature of 850°C exhibit Raman signals. They indicate N and Ti vacancies (as in thick TiN) in TiN1−x layers (x=3±2%). x is higher for the sample with 3-nm thick AlN layers, which is ascribed to N diffusion from AlN (standing close to the TiN interfaces) to TiN. In comparison to Raman peaks of thick AlN, there are split signals of wurzite AlN phase, and a signal from another phase, which might be defective rocksalt AlN standing close to the TiN interfaces. The Raman signals clearly show interactions between AlN and TiN layers.

Semi-transparent microporous TiO 2 films on SnO 2 -coated conductive glass were prepared by applying a sol–gel process. Surface topography analysis was conducted with atomic force microscopy, which revealed a highly textured and rough surface, possessing a high capacity for adsorption of a diverse variety of compounds. Surface modification of the films with ascorbic acid results in the formation of a stable, coloured surface complex which red shifts the absorption threshold of TiO 2 , enhancing utilisation of the solar spectrum. Upon illumination in a liquid electrochemical cell, ascorbic acid injects electrons into the conduction band of the semiconductor, giving rise to electrical current. The incident-photon-to-current efficiency presents a maximum at 415 nm (5.29%).

An all solid-state electrochromic device (ECD) using polyaniline (PANI) for anodic coloration and tungstic acid WO 3 , 2 H 2 O for cathodic coloration, separated by a polymer electrolyte (PAMPS), presents very good performances. To check the sequences of the protonation /deprotonation and oxidation /reduction reactions arising in fee two optically active materials, Raman spectroscopy was used on the two sides of the ECD. An improvement of fee PANI crystalline order due to fee interfacing with PAMPS, especially using PANI doped wife camphorsulfonic acid (PANI-CSA) is observed, which is one of fee reasons of fee excellent performances of fee device. The free electrons injection in fee device, which is fee key of their good reversibility, is ensured at high potentials by the cathodic tungsten bronze, and at moderate potentials by fee anodic leucoemeraldine salt

Polyaniline has been potentiostatically electrodeposited on iron in acidic medium to protect the electrode from corrosion. Two acids have been tested : oxalic and phosphoric acids to look for the influence of the passive layer on the system behavior. Influence of additives in the deposition have been examined together with temperature. Careful control of temperature deposition is necessary due to the high activation energy of the process. Metanilic and camphorsulfonic acids act as plasticisers for the polymer layer but also have beneficial effects on electrodeposition by lowering the passive potential and active currents.

The electrochemical behaviour of polyaniline (PANI) is particularly complicated, with respect to the other conductive polymers, in respect of the two reactions (protonation-deprotonation and oxidation-reduction) which occur simultaneously, but with different rates; the respective rates of the two reactions vary with the pH of the electrolyte. A further complication arises from the existence of three insulating forms with different oxidation levels. Raman, as well as optical spectroscopies are excellent tools to obtain an in situ identification of the polymer under polarization. However, it was observed that the connections between Raman/optical features and voltammograms are far from being straight. A more thorough analysis can be obtained using 'resonant' Raman with several excitating laser lines, because each of these lines is able to enhance the response of a selected polymer segment. The blue line was expected to lead to the localized polaron excitation, the red line to the exciton excitation and the near-IR line to the intrachain excitation. The use of red and IR lines brought a splitting of the CN and C-N ++ stretching modes, displaying the large variety of different segments existing at every potential. The broadening of the voltammograms obtained in weakly acidic media was easily understood; in very acidic solutions, on the contrary, owing to the sharpness of voltammograms, the complexity of the reactions arising in PANI during its polarization was not at all suspected. In the present work. PANI doped by functionalized sulfonic acids is studied. lsevier Science Ltd. All rights reserved.

The performance of nickel-based alloys as heat resistant materials is strongly dependent on their oxidation resistance. A strong resistance to oxidation of Ni-Cr alloys is expected due to the formation of a protective Cr{sub 2}O{sub 3} layer which blocks the diffusion of nickel ions to the oxide scale/gas interface and prevents from fast growth of a NiO scale. Raman spectroscopy was used here in order to determine the stresses in chromia scales formed at 900 C on Ni-30Cr alloys which develops only Cr{sub 2}O{sub 3}. Chromia has the same structure as corundum, and therefore it should have seven Raman active bands (2A{sub 1g} + 5E{sub g}). The most intense mode is the 552 cm{sup {minus}1} A{sub 1g} vibration and this one was used for monitoring the stress. It has long been known that the addition of so-called reactive elements, such as yttrium, to chromia former alloys improves the protective character of such scales by reducing the scale growth rate and, in particular by spalling during thermal cycling. Thus, Ni-30Cr samples doped with yttrium were tested and the influence of this reactive element on the oxidation kinetics and on the stress level in the oxide scale was determined.

Secondary ion mass spectroscopy was used to study the incorporation of deuterium into Si during the formation of porous silicon in fluoride D 2 O-based solutions. Results show that the deuterium diffuses from the pore tips towards the bulk silicon and remains in the pore walls in a high concentration. Measurements of the thickness of porous silicon suggest that the penetration of H species is a necessary condition for the porous Si layer to form. A simple model illustrates how the initiation of pores occurs by selective dissolution of H-induced structural defects. © 1997 Elsevier Science S.A.

Hollow sea urchin shaped nanostructured polypyrrole powder was successfully synthesized chemically in an acidic medium through a core-shell redox mechanism by using a nanostructured MnO2 powder as oxidizing agent and sacrificial template simultaneously. The morphology and the structure of MnO2 powder based reactant and produced polypyrrole powder were characterized respectively by using FEG-SEM, TEM, EDX and XRD techniques, which led us to demonstrate clearly the formation of hollow and open microparticles of polypyrrole with the presence of nanotubes on their surface. Nanostructured polypyrrole powder was found to be rather amorphous even though the shape of the polypyrrole particles was induced by the crystalline and nanostructured sea urchin shaped MnO2 powder on which they grew. In addition, neither MnO2 nor any manganese based species were found within the produced polypyrrole powder, which ruled out the production of composite materials. Moreover, Raman technique showed that the synthesized PPy powder was produced in the oxidized and thus conducting state. It actually possesses a 0.31 doping level and a 0.05 S cm(-1) conductivity, as shown by XPS and impedance spectroscopy measurements respectively. Cyclic voltammetry and UV-vis spectroscopy studies allowed us to identify the oxidation mechanism of pyrrole by our MnO2 powder through the detection of soluble Mn2+ cations as reaction products isolated after filtration of the reaction medium. (c) 2013 Elsevier B.V. All rights reserved.

Electrochemical reactivities and structural properties of several nickel hydroxide powders were analysed by X-ray diffraction, Raman spectroscopy and extended X-ray absorption fine structure (EXAFS). It is shown that the electrochemical efficiency of β-Ni(OH) 2 is associated with the amount of proton vacancies included in the crystal lattice. The number of those proton vacancies increases when the crystallite size decreases or when the ratio of co-precipitated cobalt increases. Proton vacancies shift the oxidation potential of β-Ni(OH) 2 towards less anodic values and, therefore, improve the chargeability and the electrochemical efficiency of nickel hydroxide. It is shown that both Raman spectroscopy and X-ray diffraction techniques can be used to predict effectively the electrochemical efficiency of β-Ni(OH) 2 hydroxide. EXAFS results indicate also that the oxidation level of nickel atoms inside the hydroxide is not modified by the existence of proton vacancies. It means probably that to maintain the electroneutrality in the whole crystal induces others singularities. Finally, the influence of co-precipitated additives such as cadmium and cobalt on the rate of defects has been investigated.

It has been shown that Raman spectroscopy is a powerful technique for studying the charge and discharge processes, and the open‐circuit behavior of nickel hydroxide used in the foam technology of alkaline rechargeable batteries. It is observed, in particular, that nickel hydroxide initially activated by potential cycling returns to its initial state when the electrode is left at the open‐circuit potential for a long period. Remanent cations formed by the activation procedure, which give a high conductance to the nickel hydroxide and are not reduced during the discharge process, will be completely reduced if the electrode is held at open‐circuit potential for a long period. Therefore, the electrode will need to be reactivated before subsequent use.

The different corrosion products formed on zinc specimens (pure or industrially electrodeposited) during exposure to solutions containing two concentrations of chloride were identified by Raman spectroscopy ; the crystallographic nature of these products was checked by x-ray diffraction and their morphology was described by scanning electron microscopy. The conditions of formation of hydroxycarbonates and hydroxychlorides were described, as well as the influence of pH on the growth of the different modifications of Zn(OH) 2 . The cathodic or anodic nature of the mechanisms leading to the stabilization of the different products was particularly emphasized.

The underpaint corrosion of zinc-coated steel exposed to chloride containing solutions was studied by Raman spectroscopy; the selection of an appropriate resin (without fluorescence) alloys one to perform the analysis directly through the paint. The influence of a conversion layer (chromatation or phosphatation) was investigated. On chromated zinc-coated steel as well as on the specimens without a conversion layer, two kinds of blisters were found: the ones containing ZnO, identified as cathodic blisters, and the others containing hydroxychloride, identified as anodic blisters. On the phosphated specimens, the growth of the cathodic corrosion products seems hindered. The role of the local pH variation related to the confinement is particularly emphasized.

International audience; Recently introduced as a new technique in electrochemistry, the Raman-impedance dynamic coupling allows one characterizing transfer functions so far not accessible to experiment such as instantaneous concentrations of adsorbed species in response to potential modulations. These were assessed from the measurement of the time-dependent Raman band intensities of different moieties of reduced and oxidized polyaniline. The local concentrations were assumed to be proportional to these instantaneous band intensities. This technique was used to analyze the kinetics of thin polyaniline films at high pH in the limit of electronic conductivity of the film (pH

Five Ni-Cr industrial dental alloys, containing or not containing beryllium, have been studied by cyclic voltammetry and in situ Raman spectroscopy, in electrolytic solutions with or without chloride. In the absence of chloride, the five samples behave similarly, but in KCl solution, localized corrosion appearing as “black dots” is particularly evident in the case of the Be-containing alloys. Raman spectroscopy allows the identification of these local corrosion products as different forms of molybdates and chromates, together with some other unidentified compounds.

The corrosion of zinc-coated steel sheets was studied by Raman spectroscopy. In aerated 0.03 M NaCl solutions, a large variety of corrosion products were identified in situ on unpainted sheets after 7 days of immersion. Zinc oxide, zinc hydroxychloride and zinc hydroxide were observed. For painted specimens, two main products, zinc oxide and zinc hydroxychloride, have been identified under paint blisters. It appeared that a different type of corrosion process is occurring under a paint film. It is hypothesized that the barrier properties of the paint are capable of modifying the mechanisms and thus the nature of the corrosion products. However, for both unpainted and painted specimens the nature of the corrosion products seems to depend on the local pH values in relation to chloride concentrations.

Transparent counter electrodes were prepared on transparent conductive glass (TCG) substrates from a hexachloroplatinic acid (H 2 PtCl6) solution applying the thermal decomposition method in combination with the spin-coating deposition technique. The effect of the precursor concentration and the number of deposited platinum layers on the surface characteristics of the Pt films was examined, and the relation between those surface characteristics and the electrochemical properties of the corresponding modified Pt/TCG electrodes was defined. Four types of counterelectrodes were prepared, differing in the concentration of the H 2 PtCl 6 solution (0.03M and 0.15M) and in the number of Pt layers (one or two Pt layers); their performance as counterelectrodes was evaluated after their incorporation into dye-sensitized solar cells (DSSCs) employing a solid state redox electrolyte. The obtained results show that solar cells using counterelectrodes prepared from the 0.03M H 2 PtCl 6 solution and consisting of two Pt layers (Pt032 electrode) exhibited the best performance characteristics (diffusion coefficient D * I 3 _ =1.58 X 10 -5 cm 2 s -1 , conversion efficiency η=2.16%, fill factor ff =62.14%, and short circuit photocurrent I sc =4.71mA cm -2 ). The electrochemical behavior of the modified counterelectrodes is consistent with the surface characteristics of the Pt film that formed on the conductive glass substrate, which seems to be significantly affected by the adopted method and the adjusted experimental parameters (Pt concentration and number of Pt layers). Specifically, this type of electrodes beside their low roughness (R q = 11.5 nm), also presents a high complexity (Df =2.3). As a result, for this kind of solid state DSSCs, the less rough but the more complex the Pt/TCG electrode surface, the higher the efficiency of the corresponding solar cells.

Objective:To report the rationale, recruitment, design, dietary intervention and baseline characteristics of participants in the Medi-RIVAGE study (Mediterranean Diet, Cardiovascular Risks and Gene Polymorphisms).Design:A randomised, parallel trial comparing a new nutritional programme with a conventional programme.Setting:Centre for Detection and Prevention of Arteriosclerosis, Timone University Hospital, Marseille, France, and collaborating teams.Subjects:Two hundred and twelve male and female volunteers with at least one cardiovascular risk factor.Intervention:A Mediterranean-type diet characterised mainly by the quality of fatty acids, amount of fish, vegetable foodstuffs and fibre was proposed and compared with a usually prescribed, low-fat/cholesterol diet. Body mass index, fasting lipids and lipoproteins, apolipoproteins, glucose, insulin and homocysteine were the main outcome measures. Gene polymorphisms of interest were determined.Results:Characteristics of men in the two arms were comparable with regard to sociodemographic variables, and clinical and biological cardiovascular risk factors. There were few differences between the groups of women (cholesterol-related parameters,P< 0.05). There was no difference between arms in allelic distribution of the gene polymorphisms studied. Saturated fat and protein intakes were high while carbohydrate and fibre intakes were low, but with no difference between arms. Overall, the nutritional markers were comparable in both arms with few exceptions. Correlations between nutritional intakes and plasma nutrient levels ranged from 0.19 (β-carotene) to 0.47 (folate).Conclusions:The comparability of the two arms is notable and warrants a low risk of biases. Current diet departs from the traditional Mediterranean one. The assessment of nutritional intake is validated by correlations obtained between dietary intake and relevant biomarkers. This will be important to estimate participant compliance and to analyse intervention data.

The interesting optical properties of polyaniline (PANI) allowed its utilization in all solid-state electrochromic devices. Using a sulfonic acid polymer as solid electrolyte gave to PANI an unusual optical behavior leading to electrochromic properties very superior to the properties that it has in any liquid inorganic electrolyte. The improved conductivity of PANI doped with AMP-sulfonate is displayed by the presence of a free-carriers tail even at pH as high as 4.5. The free-carriers tail is studied using UV/vis/near IR spectroscopy, and the kinetics of coloration/bleaching are studied using Optical Multichannel Analysis in the 1.5 - 3 eV range. The modifications of the PANI optical features by solid-state doping are examined. The possibility to still improve the performances of these devices--in particular their rate of color change--by using `secondarily doped' PANI is investigated, which requires a preliminary spectrochemical analysis of PANI films doped with camphorsulfonic acid and treated in m-cresol during their electrochemical polarization.

The Raman spectra of polyaniline (PANI) doped by functionalized sulfonic acids present very few differences with the spectra obtained after doping by inorganic anions, in spite of the noticeable differences displayed elsewhere by their optical spectra: the 3 eV (localized polaron) as well as 1.5 eV bands are stronger and sharper in presence of sulfonate. In fact, during the study of the different PANI forms, it was observed that the connections between Raman and optical features are far from being straight; a simple analysis in terms of the resonance in either benzoid or quinoid units is not enough. To arrive to a better understanding of these connections, we have compared the Raman spectra obtained with blue (localized polaron excitation), red (excitonic resonance) and near-IR (intrachain excitations resonance) lines; with the green laser line, PANI is out of resonance. Spectra were also obtained on samples treated to present a `secondary doping', and therefore a strong IR absorption. The use of red and IR lights allows to study the splitting of the C equals N peak, which can clearly be decomposed in two sub-bands, as well as the splitting of the 1330 cm-1 peak (assumed to be due to the stretching of C - N+$CCL).

All solid state electrochromic devices (ECD) using polyaniline (PANI) and WO 3 separated by a polymer electrolyte, PAMPS, were studied by Raman spectroscopy. The use of a blue laser line allows to isolate the spectral features corresponding to reduced PANT and in particular to follow the first steps of the charge mechanisms. On the contrary, the red line allows to investigate the phenomena associated to the oxidized and charged forms of polyaniline, and the formation of bronze in the WO 3 electrode. In such devices with several layers, the use of different laser lines allows therefore to separate the reactions in the different electrooptically active media.

c DPC/SCCME, Centre d'Etudes Nucleaires de Saclay, 91131 Gif-sur-Yvette Cedex, France Cobalt oxide films were deposited onto nickel electrodes from 25 up to 90°C at a constant potential of 0.5 Vvs. SCE from a pH 7.4 nitrate solution containing 0.09 mol L 21 Co~II!. Above 60°C, scanning electron microscopy and X-ray diffraction ~XRD! experiments reveal that the films are constituted of crystallized grains. At 90°C the crystallite size is measured atca. 34 nm. XRD experiments show that the crystallized product is composed of CoOOH, and Raman spectroscopy shows the formation of this compound between 40 and 90°C. Between room temperature and 90°C, the deposition rate is increased by an order of magnitude and the deposit crystallization has a favorable effect on the faradaic deposition efficiency. It may also favor the mechanical stability in temperature of this deposit when used as cobalt oxide-based protective coating of the molten carbonate fuel cell nickel cathode.

Dye-sensitized photoelectrochemical cells (DSSC) are characterized by electrochemical impedance spectroscopy (EIS) and Raman spectroscopy during their polarization. Cells realized with a dye recently synthesized in one of our laboratories, containing two terpyridyl (terpy) ligands, are compared with cells using commercial dyes (Ru535 and Ru620) containing isothiocyanates and either bipyridyl (bpy) or terpy ligands. Here, two points are emphasized, first, the role of the functional group (carboxylate or phosphonate) which ensures the linkage to TiO 2 and, second, the role of the redox couple (I /I - 3 ) present in the electrolyte which can react with the dye D to give unwanted intermediate species. Two species, each of them giving a characteristic Raman band in the low wavenumber range, are characterized by Raman spectroscopy. The first of these species is triiodide; the nature of the second one, which directly implies the oxidized form of dye, D + , is discussed. During the DSSC functioning, EIS allows one to discriminate three potential ranges, the photocurrent plateau, the recombination range, and the direct current range when the voltage decreases from anodic to cathodic. The second intermediate exists only in the photocurrent plateau, while I - 3 exists also in the recombination range. These results do not depend on the nature (bpy or terpy) of the ligand.

This paper presents an analysis of the first passage time problem. A lumped parameter model for a structural system is considered, and the excitation is limited to white noise. The response of this type of system is a Markov process on a multi-dimensional position-velocity space (for a damped harmonic oscillator the position-velocity space is two-dimensional). The Markov property is used to develop an integral equation for the first passage time density function. Numerical results are presented for the damped harmonic oscillator. A one-sided position boundary is considered as the region of safe operation, and a stationary start condition is analyzed. The results are compared to several previous studies of the first passage time problem.

YBaCuO thin films grown using the in situ laser ablation deposition technique, were studied using several complementary analyses : X-ray diffraction, RBS in channeling geometry and micro Raman spectrometry, in order to obtain complementary data on the crystalline quality of the films and on the nature of the intrinsic defects due to the growth process or induced by the RBS analysis.