Search

Assesses the carbon dioxide molecule penning ionization by metastable rare atom gases. Role of vibrational progression in the electron energy spectrum; Attribution of low-energy broad hump to a non-van der Waals interaction between colliding particles; Significance of an ion-pair state channel action during collision in the production of carbon dioxide molecule.

A new method for atmospheric corrosion monitoring based on the variation of radiofrequency (RF) wave propagation in a resonator during its corrosion is presented. The ability of the proposed sensor to differentiate between uniform and localized corrosion mechanisms is demonstrated by considering two identical open stub microstrip resonators produced in zinc and aluminum materials, respectively. For that purpose, experimental characterization of electromagnetic wave propagation in the resonators and simulations are compared. The proposed sensitive resonator should therefore be considered as the key element of new corrosion mimetic sensors. [ABSTRACT FROM AUTHOR]

A battery-free wireless sensor dedicated to water diffusion monitoring in dielectric materials is presented. It is applied here to the monitoring of water diffusion in organic coatings. The method is based on the variation of the radiofrequency (RF) wave propagation in an open microstrip structure covered by the coating under consideration when water diffusion occurs. Simulations and experimental characterization of electromagnetic wave propagation in a microstip line and a planar stub resonator are described. The results achieved on the resonator prove unambiguously the feasibility of the method. As a consequence, the proposed sensor should be considered as a promising and reliable tool for civil engineering applications. [ABSTRACT FROM AUTHOR]

A new method for corrosion monitoring based on the change of the radiofrequency (RF) wave propagation in a microstrip line during its corrosion is presented. For that purpose, the microstrip line is produced in the same metal as the mechanical structure under monitoring. Zinc material is considered in the study since it allows an investigation of uniform as well as localized corrosion when chloride is used. Experimental data and simulations results provide fundamental basis on the sensing mechanisms of the method and evidence the possibility to detect the created corrosion species and to distinguish between localized and uniform corrosion processes. As the consequence, the proposed method should be considered as promising and reliable tool for corrosion monitoring of several materials exposed to various environments. [ABSTRACT FROM AUTHOR]

Zn 0.9 Mg 0.1 O nanogranular thin films with a thickness of 250 nm were deposited by sol–gel spin coating process on ITO and glass substrates. Their morphology and microstructure were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray Photoelectron Spectroscopy (XPS) and atomic force microscopy (AFM). The surface was dominated by zinc oxide and magnesium carbonates. The electrical properties were governed by capillary condensation. This study demonstrates the sensitivity of these films to humidity and UV light and the interplay between both effects, already observed for individual ZnO nanowires. This highlights the ability of the Zn 0.9 Mg 0.1 O thin films to be integrated in humidity and UV sensing devices but with some cautious to allows a separations of the two environmental parameters. [ABSTRACT FROM AUTHOR]

Highlights: [•] Atmospheric corrosion under humid air of zinc and zinc–magnesium pure phases were investigated. [•] The corrosion products were characterized in depth using X-ray photoelectron spectroscopy. [•] Migration of Mg atoms toward the surface was observed during ZnMg corrosion. [•] The chemical reactions were different for Zn and MgZn2 corrosion leading to different corrosion products. [Copyright &y& Elsevier]

Abstract: X-ray photoelectron spectroscopy (XPS) and work-function measurements were used in combination to investigate the initial steps of Permalloy (Ni80Fe20) oxidation at room temperature. They showed that, after oxygen saturation, the surface is covered by nickel oxide (NiO), nickel hydroxide (Ni(OH)2) and iron oxides (Fe x O y ), and there is no preferential oxidation. Iron oxidation proceeds through the formation of FeO (Fe2+) followed with Fe2O3 growth (Fe3+). The oxidation is governed by a dissociative Langmuir-type oxidation: the sticking coefficient is decreasing over oxygen exposure. Oxidation continues by oxygen dissolution into the first layers to form a nano-oxide of about 8Å in thickness. [Copyright &y& Elsevier]

Abstract: Metastable induced electron spectroscopy (MIES) was combined to ultraviolet photoelectron spectroscopy (UPS) to study the initial steps of manganese oxidation. Oxygen exposure directly led to the formation of MnO with no intermediate states. The MnO feature saturation observed by MIES and UPS techniques showed noticeable differences and proved the formation of several oxide layers. The oxidation kinetics was studied by measuring MnO features by UPS, which depend on the surface coverage by oxygen. We observe a decrease of oxygen adsorption probability with oxygen exposure. Oxidation proceeds by oxygen dissolution into the first layers to form a three-dimension MnO. This hypothesis was confirmed by our work function measurements. [Copyright &y& Elsevier]

Abstract: Metastable induced electron spectroscopy (MIES) in combination with ultraviolet photoelectron spectroscopy (UPS) was applied to study the oxygen-pretreated Ni(111) reduction by ammonia at 600 K. Experimental data showed the perfect reduction of the surface, achieved by water desorption. However, no intermediate species like OH or NHx were observed in our spectra. Thus, ammonia dissociation reaction should be considered as rate limiting. The reduction process kinetics was investigated by measurement of the 3d band intensity. Due to the relatively large escape depth of the emitted electrons UPS provides spectroscopic information about several layers contrarily to MIES, which is only sensitive to the outermost layer. This allowed us to discriminate the surface and the subsurface processes. MIES and UPS data presented two different behaviours. Our experimental data indicated a less numerous oxygen atoms in the innerlayers whereas the surface remained unchanged. The substitution of the surface-desorbed oxygen atoms by subsurface-embedded ones is very likely. These experiment results were interpreted by using Monte Carlo simulation, which fitted well our data under the following local condition: during the upward diffusion process to the surface, the subsurface oxygen atoms slightly move laterally. [Copyright &y& Elsevier]

The reduction of oxygen pre-treated Ni(1 1 1) under hydrogen has been followed by metastable induced electron spectroscopy (MIES) and ultraviolet photoelectron spectroscopy (UPS) for a substrate temperature of 600 K. Both techniques have allowed us to report on the evolution of the electronic structure of the valence band over hydrogen exposure. These investigations showed the fast formation and desorption of water molecules, but no hydroxyl groups. The oxygen coverage of the surface depends on the Ni 3d band intensity during hydrogen exposure. By using the MIES technique, we observed that the reduction reaction is preceded with a induction period. These periods are not seen with UPS data. This difference can be attributed to the fact that MIES gives information about the outermost layer of the surface, whereas UPS probes the first innerlayers. So it indicates that oxygen atoms are desorbed from the surface, and then subsurface oxygen atoms diffuse to the oxygen-depleted surface. To interpret these experimental results, we carried out simple Monte Carlo simulations based on the fact that the reduction takes place on the surface along the NiO island perimeters. This simulation fits well the experimental data when a lateral mobility of subsurface oxygen atoms is taken into account, i.e. the reaction leads to the reduction of the three-dimension NiO before the outermost layer oxygen desorption. [Copyright &y& Elsevier]

• Description of a new method for environmental corrosiveness monitoring based on the RFID technology. • Sensitivity of the sensor ensured by the EM coupling between an RFID antenna and a sensitive metallic layer exposed to the environment. • Monitoring thickness variation of metals in the range of tens of nanometers. The environmental corrosiveness is governed for indoor applications by the presence of gaseous pollutants in air and levels of temperature and relative humidity. Its determination is a challenging task and requires the monitoring of thickness reduction of selected metals in the range of few tens of nanometers. The present work aims at developing an UHF RFID (Ultra High Frequency Radio Frequency Identification) sensor dedicated to such measurements. The sensor is based on the coupling between the antenna of a commercial RFID tag and a thin layer of copper exposed to the environment. The ability of the proposed sensor to be sensitive to a variation of the metal thickness in the range of tens of nanometers is demonstrated experimentally through exposure tests in a climatic chamber. The results are supported by electromagnetic simulations performed in the case of a coupling between a dipolar antenna and a thin metallic layer. [ABSTRACT FROM AUTHOR]

Zinc substrates were electrochemically oxidized in NaCl solution to produce corrosion patinas. XRD, XPS and Raman analyses enabled the identification of simonkolleite and zinc oxide as the patina constituents. FIB-SEM imaging shows that the upper part of the patinas is a network of simonkolleite nanosheets with an open microstructure that is unlikely to act as a significant barrier for corrosion processes. STEM investigations and Raman mapping measurements reveal the presence of a ca. 20–400 nm thin nanoporous ZnO-rich film below the simonkolleite and covering the zinc substrate. Under potentiostatic conditions, the reduced cathodic activity of the patina-covered zinc electrodes is assigned to this nanoporous ZnO layer. [ABSTRACT FROM AUTHOR]

Zinc oxide (ZnO) layers were electrodeposited from an aqueous nitrate bath at 62 °C on copper substrates. At −0.9 V (vs. saturated calomel reference electrode), the growth rate is 600 nm min −1 . In the early stages of the deposition, the layers are porous. At longer deposition times, the surface becomes dense and rough. The wurtzite crystalline structure is confirmed by XRD measurements and the chemical composition of the ZnO surface was assessed by EDX and XPS. The oxygen reduction reaction (ORR) was investigated at room temperature in a 10 −3 M KOH solution with KCl as supporting electrolyte. The ORR onset potential is found to be much larger than that of platinum taken as reference electrocatalyst. Rotating ring-disk electrode experiments evidence a negligible production of hydrogen peroxide as intermediate product of the reaction. The latter follows thus a direct four-electron pathway at pH ∼11. [ABSTRACT FROM AUTHOR]

Abstract: We present a corrosion behaviour study of pure phases of zinc and zinc–magnesium contaminated with NaCl and exposed to humid air for 30days: Zn, Mg2Zn11 and MgZn2. The composition of corrosion products is analysed using infrared spectroscopy (FTIR), X-ray diffraction (XRD), ion chromatography (IC), and X-ray photoelectron spectroscopy (XPS). The improved corrosion stability of MgZn2 is found to be connected to changes in the surface pH and to the nature of the formed corrosion products. The presence of magnesium modifies the proportion of the OH and CO3 bonds in the corroded products. This explains the improvement in corrosion resistance. [Copyright &y& Elsevier]

Abstract: Zinc oxide (ZnO) is a chemical compound of great interest used, for example, as photocatalyst in the purification of wastewater or polluted air. However, neither dissolution, nor photo-dissolution of ZnO is negligible: indeed, both processes reduce significantly the efficiency of photocatalysis and then lead to a secondary pollution by free Zn2+. In the present study, the stability of ZnMgO thin films in weak alkaline solution is investigated. We demonstrate that the replacement of Zn2+ ion with Mg2+ ion results in the production of a Zn0.84Mg0.16O solid solution, whose stability is higher than that of the ZnO sample. This alloy, thus, constitutes an alternative to the use of ZnO in photocatalysis applications. To gain more insights into the higher resistance of such alloys to the dissolution process, X-Ray photoelectron spectroscopy measurements were performed. They highlighted the role of OH group adsorption in the experimentally observed enhancement of ZnMgO stability. [Copyright &y& Elsevier]

Abstract: Hematite (α-Fe2O3) nanowires were observed through directly annealing Ni81Fe19 foils at 600°C for 120min in atmosphere. X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and scanning electron microscopy (SEM) techniques were used to characterise the nanowires. The results indicate that the growing mechanism includes iron segregation to the surface combined with an internal stress induced by the oxidation process. [Copyright &y& Elsevier]

In this study, a sensor based on the development of a planar antenna immersed in sediments dedicated to water content monitoring in this type of material is proposed and experimentally validated. It is produced by a conventional Printed Circuit Board (PCB) manufacturing process on a double-sided metalized FR4 substrate. The sensitivity of the sensor is ensured by the variation of the real part of the complex dielectric permittivity of sediments with water content at around 1 GHz. As shown, in this frequency range, electrode polarization and Maxwell–Wagner polarization effects become negligible, leading to only a bulk water polarization sensitivity. The sensor operates in the reflection mode by monitoring the variation of the resonant frequency as a function of the sediment density through the S11 reflection measurements. An experimental sensitivity of 820   MHz. g − 1. cm 3 was achieved. Despite the simplification of data interpretation at the considered frequency, the influence of ionic species such as NaCl in sediments on the real part of the relative complex dielectric permittivity is highlighted. This demonstrates the importance of considering a second parameter such as the S11 level at low frequency or the electrical conductivity to extract the density from the frequency measurements. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Elaboration of alginate hydrogels with different copper/zinc and calcium concentrations. • High inhibition of marine microalgae adhesion by calcium, copper or zinc alginates. • Low toxicity of mixed calcium/zinc alginate against microalgae. Abstract Microorganisms have the ability to settle on nearly all man-made surfaces in contact with seawater and subsequently to form biofilm. Biofilms control and removal is necessary in the sectors of maritime transport, energy... In this work, we present the development of new pure calcium, zinc or copper alginate, but also mixed Ca/Cu and Ca/Zn alginate hydrogels. These materials have been evaluated for their potential inhibition of adhesion of two key biofilm-forming microalgae (Halamphora coffeaeformis and Cylindrotheca closterium). All the tested materials have presented high adhesion inhibition (about 80%). Copper-base materials present a high toxicity against H. coffeaeformis. Pure zinc alginate is also toxic for this strain. However, the addition of calcium in zinc alginate leads to the toxicity reduction. The toxicity of these materials differs according to the strains. Consequently, mixed zinc/calcium alginate are efficient at inhibiting microalgal adhesion with a low level of cells toxicity. These alginate hydrogels are promising materials because they are efficient, cheap, easy to develop and eco-friendly. [ABSTRACT FROM AUTHOR]

• The accurate monitoring of biofilm formation is possible using OCP monitoring. • The verification of OCP results by EIS provides convincing results. • The formation process of biofilm is split into 3 steps. • An insulating layer is naturally formed in TSB culture media on GC electrode. Understanding and sensing microbial biofilm formation onto surfaces remains highly challenging for preventing corrosion and biofouling processes. For that purpose, we have thoroughly investigated biofilm formation onto glassy carbon electrode surfaces by using electrochemical technics. Pseudomonas aeruginosa was studied because of its remarkable ability to form biofilms in many environments. The modification of the electrode-solution interface during biofilm growth was monitored by in-situ measurement of the open-circuit potential and correlated with results obtained by electrochemical impedance spectroscopy, cyclic voltammetry, scanning electron microscopy and bioassays. The sensing of the biofilm formation hence suggests a multi-steps mechanism, which may include pre-formation of an insulating layer onto the surface prior to the bacteria adhesion and biofilm formation. [ABSTRACT FROM AUTHOR]

High aspect ratio nanowires were electrodeposited in nanoporous anodic alumina template by a potentiostatic method. The angular dependence of the coercive field and remanence magnetization extracted from magnetometry measurements are compared with micromagnetic simulations. Inclusion of magnetostatic interactions between Ni nanowires in simulations is required to explain some of the properties of the magnetization reversal. However, it is not sufficient to reproduce fully the angular dependence of the coercive field. Due to the polycrystalline nature of nanowires and thus to the presence of grain boundaries, defects are included in simulations. A good agreement between theory and experiment is then clearly highlighted, in particular in the nanowire easy axis direction. The achieved results allow a description of several experimental data published in the literature and consequently to get a better understanding of reversal mechanisms that operate in such nanowire arrays. A complementary study of composite nanowire array is successfully performed to prove the adequacy of the simulations method to describe the magnetic properties of nanowire array. [ABSTRACT FROM AUTHOR]

The effect of two concentrations of H 2 S (0.5 and 2.5 ppm), in controlled laboratory conditions (20 °C, 75%RH), on the atmospheric corrosion of pure Ag, Cu and Ni was investigated in this study. The corrosion product morphology and composition were analysed through a multi-technique approach including SEM/EDX, Raman spectroscopy, XPS and XRD. Different corrosion products were identified depending on the type of characterisations providing a better overview of the effect of H 2 S on the atmospheric corrosion of pure Ag, Cu and Ni. Possible mechanisms involved in the formation of these corrosion products are also discussed in this work. • Investigations on the effect of H 2 S on the atmospheric corrosion of Ag, Cu and Ni. • Characterisation of corrosion products using a multi-analytical investigation approach. • Identification of possible mechanisms involved in the atmospheric corrosion of Ag, Cu and Ni. [ABSTRACT FROM AUTHOR]

The corrosion behaviour of pure zinc and zinc-magnesium-aluminium alloy (ZMA) has been studied during 6 months of exposure in marine environment (Brest, France). The composition of corrosion products is analysed using infrared spectroscopy (FTIR), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). An improved corrosion resistance of ZMA is observed. This improvement is found to be connected to Mg2+ and Al3+ induced quenching of corrosion activity and to the enhancement of NaZn4Cl(OH)6SO4·6H2O in the formed corrosion product. [ABSTRACT FROM AUTHOR]

For the on-line monitoring of high fast neutron fluxes in the presence of a strong thermal neutron component, SCK•CEN and CEA are jointly developing a Fast Neutron Detector System, based on ^242\ Pu fission chambers as sensors and including dedicated electronics and data processing systems. Irradiation tests in the BR2 reactor of ^242\ Pu fission chambers operating in current mode showed that in typical MTR conditions the fission chamber currents are dominated by the gamma contribution. In order to reduce the gamma contribution to the signal, it was proposed to use the fission chambers in Campbelling mode. An irradiation experiment in the BR2 reactor with a ^242\ Pu and a ^235\ U fission chamber, both equipped with a suitable cable for measurements in Campbelling mode, proved the effectiveness of the suppression of the gamma-induced signal component by the Campbelling mode: gamma contribution reduction factors of 26 for the ^235\ U fission chamber and more than 80 for the ^242\ Pu fission chamber were obtained. The experimental data also prove that photofission contributions are negligibly small. Consequently, in typical MTR conditions the gamma contribution to the fission chamber Campbelling signal can be neglected. [ABSTRACT FROM AUTHOR]

A crossed beam experiment is carried out to measure the energy of electrons emitted in Penning ionization processes by Ne*(3P2,0)–Kr collisions. The electron energy spectra have been measured at four different collision energies: 0.050, 0.140, 0.190, 0.460 eV. The analysis of the results allows the separation of spin orbit contributions both in the entrance and in the exit channels providing the related cross-section ratios. Some theoretical considerations have been made to clarify nature and role of interatomic potentials driving the collisions and some general features about the role of atomic fine structure in the Penning ionization processes. [ABSTRACT FROM AUTHOR]