Carbon steel (C75) is exposed to highly reactive species such as hydroxyl radicals OH created by a gliding arc discharge (GAD) in humid air at atmospheric pressure. The protective properties of carbon steel treated by GAD are studied versus different treatment times (t) and for an immersion in corroding 0.5 M sodium chloride solution during 24 h. Evolutions of corrosion rate are studied using weight loss measurements and electrochemical methods, e.g., electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization. The results obtained by GAD treatment show that the corrosion rate of steel decreases with the ennoblement of the corrosion potential and the decrease of the corrosion current density. This indicates that the plasma treatment acts as an anodic type inhibitor and suggests the formation of a protective layer. EIS measurements confirm the presence of this film: the charge transfer resistance (Rct) increases with GAD treatment time, leading to a corrosion inhibition efficiency around 73% for a treatment time equal to 60 min. This confirms the importance of the plasma effect. The gliding arc discharge is a clean and efficient technology for the surface treatment of carbon steel; it improves the anticorrosion properties of steel in aggressive environments, forming a resistant and insulating barrier.

In this work low bandgap thienylenevinylene and phenylene vinylene copolymers, which possess either 3,4-ethylenedioxylthiophene (EDOT) groups (Polymer 1) or long alkyl side chains (Polymer 2) were investigated and compared in photoinduced electron transfer properties and photovoltaic performance. The results show that the interaction of the photoexcited polymers with an electron acceptor ([6,6]-phenyl C61 – butyric acid methyl ester (PCBM)) leads to charge generation and transfer for both polymers. We found that the long alkyl side chain in Polymer 2 instead of the EDOT group in Polymer 1 enhances the open circuit voltage ( $V_{\it OC})$ but lowers the short circuit current ( $I_{\it SC})$ . On the other hand the long alkyl side chain in Polymer 2 significantly improves the solubility and enhances processability for solar cells fabrication. Optimization of the chemical structure of these low bandgap polymers could lead to a spectral improvement of photocurrent generation in organic solar cells.

Among the existing non-destructive testing techniques, the flying spot photothermal technique [CITE] appears to be a good alternative to penetrant testing for open-cracks detection in metallic structures. The technique basically consists in the local heating of a structure under test and the measurement of the temperature elevation which depends on the inspected medium properties. During the scanning of the structure, thermal and optical effects contribute to the elaboration of the photothermal signals. The thermal effect is relative to the presence of a thermal barrier in the inspected medium (e.g. crack) and the optical effects are due to the variations of the absorptivity and diffusivity factors of the inspected surface (surface conditions). Both effects are competitive and can lead to hardly interpretable signals.In this paper, the authors present a method allowing to separately identify thermal and optical effects, in order to enhance the characterization of the structure under test. The method was applied on a mockup featuring open-cracks and rough surface conditions, and allows to construct separate optical and thermal images. The resulting so-called thermal image allows to significantly highlight the presence of the cracks. Besides, the optical image enriches the characterization of the structure, since it supplements the diagnosis of the cracks and also enables to characterize other defects such as surface topology and features.

An experimental study is presented involving the modelling of a concept which enables exterior dehydration of contaminating or fragile products. This concept is based upon the use of a ground-breaking film which is permeable exclusively to water vapour and semi-transparent to the sun's rays. The experimental results presented (derived from a campaign conducted with the help of a drying cell designed for this purpose) lead to the setting up of a simple model enabling the design and sizing of systems based on the use of this film to be considered.

Superparamagnetic nanoparticles are very interesting objects having many applications among which MRI contrast agents are one of the more important. In this work the longitudinal relaxation times of Endorem and Lumirem, two colloidal solutions of iron oxide nanoparticles used as contrast agents for magnetic resonance imaging were measured at magnetic field intensities similar to the ones used in MRI. T 1 was seen to depend on nanoparticle concentrations as expected but, for the Lumirem, also on the time spend by the sample under the influence of the static magnetic field. The T 1 evolution was measured for colloidal solutions both different concentrations and different viscosities. The strange T 1 dependence is presented and discussed relating to the nanoparticles superparamagnetic properties. It is shown that one of the possible reasons for the fact is the formation of local field enhanced linear arrays of SPIO.

We present results on the room temperature mechanical quality factor of single crystal calcium fluoride (CaF2) grown by the Bridgman-Stockbarger method. Resonant mode Q-factors are measured in the frequency range 20 to 76 kHz using tungsten wire loop suspensions. In spite of indications of only moderate crystal purity, we observed 6 modes with Q-factor > 107, and one with $Q = 4.5 \times10^{7}$ , more than an order of magnitude higher than previously reported results.

The final properties of cast materials depend greatly on the solidification process undergone by the material. In this paper, we study gold alloys dedicated to the watch industry and jewellery in the framework of a research collaboration with the Metalor Company. The aim is to improve the concentration homogeneity of the ingots by controlling the solidification step. It can be achieved by reducing segregations by a decrease in the grain size.For this purpose, we set up a multiphase electromagnetic stirring of the melt to favour the growth of finer grains and improve the homogeneity of the composition. We first design an electromagnetic stirrer by numerical simulation. The stirrer is then implemented on a model experiment. Eventually, the alloys are characterised by metallography and etching to evidence the grain structure. As expected, we obtain a substantial reduction of the grain size although, some work remains to be done to attain the final goal of even finer grains.

The effect of thermal annealing on the structural properties of electron beam evaporated polycrystalline Si/Ge multilayer structures has been studied using Grazing incidence X-ray diffraction (GIXRD), reflectivity (GIXRR) and Raman spectroscopy techniques. The chemical nature of layers at surface and interfaces has been obtained from X-ray photoelectron spectroscopy (XPS) technique, which revealed the presence of impurities only at the top surface in the form of carbides and oxides in the Si layer and in elemental form in the Ge layer. Reflectivity measurements show that the Si/Ge MLS is stable upto 200 °C and roughness of Si on Ge interface is higher as compared to that of Ge on Si interface. Similarly, GIXRD results show that upto 200 °C, MLS is of microcrystalline nature and further annealing at 300 °C and 400 °C, well-defined crystalline peaks of pure Si and Ge are observed, which is in contrast to earlier reported experimental findings. Observed results are interpreted in terms of diffusion induced crystallization and corresponding increase in grain size.

The physico-chemical environment around the aluminum impurity atoms in commercial Herasil silica is studied by electron-induced X-ray emission spectroscopy. Despite the low concentration of aluminum and the charging effect occurring upon electron irradiation, we have been able to characterize the environment of the Al atoms. We show that the Al atoms are in an octahedral environment, i.e. surrounded by 6 oxygen atoms. The presence of Al clusters, whose metallic character would make them candidates to be ultraviolet absorption centers, is ruled out.

We present a novel multilayered architecture for memristive devices which provides an alternative to conventional conductive filament switching. In conventional resistive switching, conductive filaments form and extend stochastically under applied electrical bias, with longer filaments being subjected to magnified electric fields that amplify their growth rate, producing a spatially localized and highly non-uniform conduction front of filaments. This produces devices with large variations in resistive and capacitive properties that are difficult to tune. Here, we simulate a multilayered device structure with alternating ionic mobility that predicts the development of a quasi-uniform conduction front which amplifies memcapacitive properties of the device and reduces device-to-device variability. Furthermore, this novel structure is predicted to enable fine-tuned control of switching events, an important property for analog (multibit) memory and neuromorphic computing applications.

Polypropylene metallized capacitors are of general use in power electronics because of their reliability, their self-healing capabilities, and their low price. Though the behavior of metallized coiled capacitors has been discussed, no work has been carried out on stacked and flattened metallized capacitors. The purpose of this article is to suggest an analytical model of resonance frequency, stray inductance and impedance of stacked capacitors. We first solve the equation of propagation of the magnetic potential vector (A) in the dielectric of an homogeneous material. Then, we suggest an original method of resolution, like the one used for resonant cavities, in order to present an analytical solution of the problem. Finally, we give some experimental results proving that the physical knowledge of the parameters of the capacitor (dimension of the component, and material constants), enables us to calculate an analytical model of resonance frequency, stray inductance and impedance of stacked capacitors.

Le principal objectif de cet article est de présenter le fonctionnement destubes à gaz pulsé (TGP) par une analogie électrique [1] où la tension et lecourant représentent les paramètres hydrodynamiques pression P et débit massique m du système. Toute impédance peut être traitée comme un assemblage d'élémentsélectriques : résistance, capacitance ou inductance. À la source chaude du TGP,différents déphaseurs sont modélisés de la même manière et ainsi peuvent êtrecomparés, comme l'orifice pulse tube refrigerator (OPTR) ou tube pulsé à simpleorifice, le double inlet pulse tube refrigerator (DIPTR), le modified pulse tube refrigerator (MPTR) dont le déphaseur est un piston à la source chaude, le hybridpulse tube refrigerator (HPTR) à ouverture séquentielles d'orifices, l'inertancein OPTR (IOPTR). En combinant cette analogie électrique avec l'étude thermique ilest possible de prédire un bilan d'énergie à la source froide : puissance extraite,pertes du régénérateur, pertes du tube et influence des volumes morts. Différentessolutions peuvent être apportées au traitement de cette modélisation. Si les paramètres ne sont pas sinusoïdaux, le système peut être traité à un ordre supérieur à1. Cette modélisation a été utilisée pour la conception du tube à gaz pulsé miniaturequi travaille à des fréquences élevées 20-50 Hz et à des pressions supérieures à 20MPa, construit en collaboration avec la société “Air Liquide”. Le compresseur(rotatif ou linéaire) de demi volume balayé ≈ 1 cm3 est du type utilisésur les “Stirling”, il délivre une onde de pression quasi sinusoïdale. Sous 3 MPa depression moyenne et une fréquence de 27,5 Hz, la température limite en mode doubleinlet est de 49 K avec une puissance disponible de 1 W à 84 K.

Within Silicon Carbide Junction Field Effect Transistor (SiC-JFET) model, body diode is not extensively studied and almost under-researched. Body diode remains a complex device to study particularly during switching transients. In this paper, the JFET body diode is experimentally demonstrated to be a power PiN diode. Finite element method model based on the device geometry and SiC material is used to accurately simulate this diode. Accurate simulations are necessary for analysis and verification purposes. Simulation relies on component models and associated parameters. The paper focuses on a step-by-step extraction procedure for design parameters of the SiC-JFET body diode. A comparative study between experimental data and simulation results is given to validate the device model and associate parameters.

The substitution sites of Pb and Dy dopants in the cuprate-type high temperature superconductor Bi2Sr2Ca1Cu2O $_{8+\delta}$ are determined by a direct comparison of the angle-scanned X-ray photoelectron diffraction (XPD) patterns. We demonstrate the power of XPD as a fingerprinting tool and conclude that Pb occupies Bi sites and Dy the Ca sites. The presence of the incommensurate lattice modulation is not visible in XPD, probably due to a Pb-induced, reduced modulation amplitude.

We have developed a model for the calculation of the induced current due to an electron beam with an extended generation profile. The analytical expression of the electron beam induced current (EBIC) is obtained by solving the steady-state continuity equation using the Green function method. In the case of a sulphur doped (Ga0.7Al0.3As:N+/Ga0.7Al0.3As:P) sample prepared by metalorganic vapour phase epitaxy (MOVPE) method, the experimental current profile, measured by SEM enabled us to calculate the diffusion length of the minority carriers (Lp = 1 μm in the N region and Ln = 1.80 μm in the P region of the ternary sample). Far from the depletion layer, the experimental current profile measured provided us the optical self absorption coefficient of this sample: ap = 1.483 μm−1 in the N region and an = 0.167 μm−1 in the P region. According to our EBIC model, the width of the depletion layer of this sample is about 0.8 μm, while at elaboration of the sample, 10 years ago, the width of the depletion layer deduced from the characteristic curve I(V) was about 300−400 Å. This widening of the depletion layer is due to the ageing of the diode.

The bulk micromachining on (010), (110) and (111)A GaAs substrates in the 1 H2SO4:1 H2O2:8 H2O system is investigated. Focus is placed on anisotropy of 3D etching shapes with a special emphasis on convex and concave undercuts which are of prime importance in the wet micromachining of mechanical structures. Etched structures exhibit curved contours and more and less rounded sidewalls showing that the anisotropy is of type 2. This anisotropy can be conveniently described by a kinematic and tensorial model. Hence, a database composed of dissolution constants is further determined from experiments. A self-elaborated simulator which works with the proposed database is used to derive theoretical 3D shapes. Simulated shapes agree well with observed shapes of microstructures. The successful simulations open up two important applications for MEMS: CAD of mask patterns and meshing of simulated shapes for FEM simulation tools.

In2S3 thin films containing different quantities of sodium have been synthesized by co-evaporation of sodium and In2S3 powder from separate sources using vacuum thermal evaporation method. Films were deposited on ordinary glass at 240 °C. The process of incorporation of sodium was studied as function of at.% Na. Films have been characterised by means of X-ray diffraction, SEM, EDAX and spectrophotometry. X-ray diffraction analysis confirmed the initial amorphous nature of deposited layers and revealed the formation of In2S3 as function of annealing layers containing sodium in nitrogen at 300 °C for 2 h. Energy Dispersive X-ray Analysis (EDAX) revealed the composition of the films as a function of the sodium incorporation. Surface Electron Microscopy showed that these films were granular and homogenous. The films have an n-type electrical conductivity and their optical direct band gap can be managed between 2.20 and 2.45 eV by controlling their sodium content. The variation of parameters for as-deposited and annealed films has been studied within $x\le 4$ at.% solid solution composition. Thin layers with homogeneous surfaces, direct band gap energy $(E_g)$ of about 2.45 eV for 4 at.% Na and 0.9 μm-thick have been achieved.

This paper is devoted to atactic polystyrene (aPS) thin films treatment under DC pulsed discharge in nitrogen. The experiments were performed using a symmetrical plane-to-plane of electrodes configuration in order to improve the treatment homogeneity and also to compare the treatment efficiency when the aPS is on the cathode or on the anode. During these experiments, the pressure and the electrical conditions were maintained unchanged. The experimental results were compared for the two positions of samples, when the gap length and the afterglow duration time were varied. It appears that the treatment depends on the sample position and an interpretation is proposed. The physical conditions and the reaction processes in the plasma bulk and on the aPS surface were analysed in order to understand their influence on the surface treatment. The importance of metastables is pointed out and it is deduced that these long-life excited states are firstly produced near the anode and fill the gap following the evolution and distribution of the electron current density.

In this study we will present a simple semi-empirical method to predict the chemical composition and the deposition rate of tungsten oxide coatings deposited by magnetron sputtering with reactive gas pulsing process (RGPP) as a function of two easily measured deposition parameters: target potential and total pressure. The coatings were deposited by DC magnetron sputtering from a pure tungsten target in reactive atmosphere (Ar + O2) using the conventional process (CP) with constant oxygen flow and the RGPP. The oxygen flow was varied from 0 (pure tungsten deposition) to 20 sccm corresponding to tungsten trioxide during the conventional process. When RGPP was used, a 20 sccm oxygen flow was pulsed using a square regulation signal, defined by a pulsing period (T) and an oxygen injection time (t ON ). The conventional and RGPP process parameters (target potential, total pressure and deposition rate) and the corresponding chemical composition were used to build a simple model predicting the deposition rate and the average chemical composition of the coatings deposited by RGPP as a function of the pulsing parameters. It was shown that the measured total pressure could be used to calculate the deposition rate and the chemical composition of the RGPP coatings with reasonable precision.

A series of CuxMg1–xNb2O6 (x = 0, 0.2, 0.4, 0.6, 0.8, 1) columbites were prepared using the sol-gel technique. The samples were sintered at 900 °C for 6 h. The prepared samples were structurally characterized using X-ray diffraction (XRD) method. To study their applicability in low temperature cofired ceramic (LTCC) technology, elastic properties have been characterized for mechanical compatibility. Elastic behavior was investigated at 300K, employing ultrasonic pulse-transmission technique at 1 MHz. The values of elastic moduli and acoustic Debye temperature (µD) were computed from longitudinal and shear velocities. The measured values were corrected to zero porosity using Hasselman and Fulrath's formula. The elastic constants of the samples, estimated using Modi's heterogeneous metal-mixture rule, were also reported. The variation of elastic moduli was interpreted in terms of strength of interatomic bonding. Microstructure of these samples was studied using the FESEM (field emission scanning electron microscopy) technique. Mechanical properties including yield strength, tensile strength and thermal stress resistance were calculated from thermal properties measured through thermal conductivity and thermal expansion coefficient.