FePt:C films were prepared by filtered vacuum arc deposition. A strong dependence of coercivity and ordering of the face-central tetragonal structure on both C concentration and annealing temperature was observed. With C concentration of 21%, the sample with a coercivity of 5.7 kOe was obtained when annealing temperature was only 350 °C. Transmission electron microscope observations revealed that FePt grains with an average size of 4.1 nm were embedded in C and appeared to be well isolated.

The aim of this paper is to define a linear model of a planar standing wave ultrasonic motor (SWUM). First, the analytical approach using the variational formulation is presented. An identification method is deduced to find the parameters of a vibrating rectangular plate. Non-linearities are also emphasized and verified by the experimental measurements. Secondly, the mechanical energy conversion of the actuator is identified, using an average behavior modelling and a linear approach for the contact interaction. Finally, a complete modelling of the actuator is presented, using the Causal Ordering Graph formalism.

In an earlier paper [P.J. Wellmann, A. Albrecht, U. Künecke, B. Birkmann, G. Mueller, M. Jurisch, Eur. Phys. J. Appl. Phys. 27, 357 (2004)] an optical method based on whole wafer absorption measurements was presented to determine the charge carrier concentration and its lateral distribution in n-type (Si/Te) doped GaAs. The submitted results for Si-doped GaAs gave rise to questions concerning the interpretation of absorption mappings in wafers with high dislocation densities. GaAs substrates for optoelectronic devices are strongly affected by dislocations. Therefore further studies were conducted: absorption and Hall measurements were performed on GaAs:Si wafers with high and low dislocation densities. Absorption in Si-doped GaAs is far more complex than in Te-doped GaAs. It shows a co-dependency on charge carrier concentration and dislocation content which causes complications in the quantitative optical determination of the charge carrier concentration. Qualitatively, absorption mappings depict dislocations and variations of charge carrier concentration very well.

In order to meet absolute metrology of displacement in several axes simultaneously; the induced errors due to the fluctuation of atmospheric parameters and Doppler effect should be investigated. Measurements of phase dispersion and Doppler frequency shift over two different axes using dual-wavelength laser heterodyne interferometer (ZMI-1000A) are reported. The principle of this work is to study the induced parameters influences of an absolute measurement of a displacement over two different axes in a free atmosphere using laser heterodyne interferometer.

The surface modifications produced by treatment of a synthetic sulfur vulcanized styrene-butadiene rubber with oxidizing (oxygen, air, carbon dioxide) and non oxidizing (nitrogen, argon) RF low pressure plasmas, and by treatment with atmospheric plasma torch have been assessed by ATR-IR and XPS spectroscopy, SEM, and contact angle measurements. The effectiveness of the low pressure plasma treatment depended on the gas atmosphere used to generate the plasma. A lack of relationship between surface polarity and wettability, and peel strength values was obtained, likely due to the cohesive failure in the rubber obtained in the adhesive joints. In general, acceptable adhesion values of plasma treated rubber were obtained for all plasmas, except for nitrogen plasma treatment during 15 minutes due to the creation of low molecular weight moieties on the outermost rubber layer. A toluene wiping of the N2 plasma treated rubber surface for 15 min removed those moieties and increased adhesion was obtained. On the other hand, the treatment of the rubber with atmospheric pressure by means of a plasma torch was proposed. The wettability of the rubber was improved by decreasing the rubber-plasma torch distance and by increasing the duration because a partial removal of paraffin wax from the rubber surface was produced. The rubber surface was oxidized by the plasma torch treatment, and the longer the duration of the plasma torch treatment, the higher the degree of surface oxidation (mainly creation of C–O moieties). However, although the rubber surface was effectively modified by the plasma torch treatment, the adhesion was not greatly improved, due to the migration of paraffin wax to the treated rubber-polyurethane adhesive interface once the adhesive joint was produced. On the other hand, the extended treatment with plasma torch facilitated the migration of zinc stearate to the rubber-adhesive interface, also contributing to deteriorate the adhesion in greater extent. Finally, it has been found that cleaning of SBS rubber in an ultrasonic bath prior to plasma torch treatment produced a partial removal of paraffin waxes from the surface, and thus improved adhesion was obtained.

This paper deals with positive and negative corona discharge in atmospheric air using a wire-to-plane system. The Poisson's equation is solved numerically using the finite-element method and the current continuity equation. The space charge density is updated using the simplified method of characteristics, where the ion diffusion is neglected. The numerical model takes into account the avalanche length of the corona discharge and the potential corresponding to the minimum ionisation field is directly introduced in the method on the border of the ionisation region. The end geometry of the linear biased probe without wraparound bias plates has been adapted to a wire-to-plane system for use in DC corona discharge. The current density and the electric field are measured; their spatial distributions are given and compared with the computed values. The agreement between the calculated values and those obtained experimentally is satisfactory. The per unit electric field and current density are also represented by a unique function.

The aim of this work is to identify the main process responsible for sterilization of Geobacillus Stearothermophilus spores in O2:N2 RF inductively coupled plasma. In order to meet this objective the sterilization efficiencies of discharges in mixtures differing in the initial O2/N2 ratios are compared with plasma properties and with scanning electron microscopy images of treated spores. According to the obtained results it can be concluded that under our experimental conditions the time needed to reach complete sterilization is more related to O atom density than UV radiation intensity, i.e. complete sterilization is not related only to DNA damage as in UV sterilization but more likely to the etching of the spore.

A new method for direct evaluation of the electron energy distribution function in plasmas is suggested, which involves the use of audio frequencies distortion factor meters. The amount of distortion suffered by a Langmuir probe AC current produced by superimposing a clean AC voltage on the DC probe voltage is measured. Although such distortions are proportional to the second derivative of the probe characteristic at any point when its neighborhood can be approximated by a second-degree polynomial, the instrument function is always sharper than that of harmonic differentiation. The method is analyzed theoretically, and tested experimentally. It is also shown that distortion additionally provides a direct measure of the electron temperature.

We present the optimization of a sterilization process with a N2 flowing afterglow post-discharge. First we study the inactivation of bacteria (E. coli) submitted to the post-discharge, and discuss the mechanisms of bacteria inactivation. Then we evaluate the volume repartition of the active species (N atoms produced by plasma discharge) in the chamber of treatment.

The main goal of this work was the development of methodologies for determining the energetic structure of welding arcs in Gas Metal Arc Welding (GMAW), i.e., with metal transfer. The present article focuses on a methodology applied to short-circuiting transfer. This methodology is based on equations which operate with discrete instantaneous values from measurements of welding current, arc voltage, arc length and electrode + droplet length. Metal transfer images were obtained through the use of laser shadowgraphy aided by high-speed camera. Dedicate computational programs were developed for electrical and geometrical values quantifications. Synchronization between the electrical signals and the metal transfer images made possible to associate total arc voltage measured at any point of oscillograms to the arc and electrode + droplet geometrical parameters. The proposed methodology was validated by using stainless steel GMAW shielded with Ar based blends and N2 contents ranging from 1 to 5%. The results showed that the methodology is sensitive enough for perceiving small variations in the voltage drops that compose the total arc voltage as a consequence of using different shielding blends.

In this work is presented a detailed physicochemical, structural and optical characterization of SiOxNy thin films. The films deposited using PECVD in SiH4-N2O-He discharges were thermally annealed at 1273 K for 1 hour in ambient nitrogen. The film stochiometry was measured by Rutherford Backscattering Spectroscopy. The chemical composition was dominated by silicon suboxide containing some Si-N and Si-H bonds. Raman scattering measurements suggest the formation of nanocrystallite silicon in the annealed films. The Raman observation is strongly supported by Transmission Electron Microscopy analysis which shows a high density of silicon nanocrystals, having a mean radius ranging between 3 and 6 nm. Using Spectroscopic Ellipsometry, we discussed the dielectric function evolution as a function of the deposition parameters.

Gate drive circuits for power MOSFET's and IGBT's often require electrical insulation. Different methods of electrical insulation can be used: bootstrap circuits, transformers and optic couplers. It has been proved that Piezoelectric transformer (PT) exhibit suitable characteristics, good integration capability and can be used for both power and signal transfer in low power applications. However, coreless planar electromagnetic transformer (CT) technology is an alternative solution that can also give satisfactory results. This paper compares the performances and the capabilities of integration of these two kinds of transformers (i.e. PT vs. CT). The study and comparisons are carried out in a two-gate driver, functioning in a half-bridge inverter. The two devices have the same structure, similar electric characteristics (operating at resonance frequency in both cases), identical electric values and the dimensions of the two transformers are quite the same. Additionally, some EMI aspects regarding the use of these transformers will be considered.

Two inverses methods are developed to calculate the surface heat flux and temperature of a body during heat treatment. Knowing temperature of an inner point of the solid and taking into account the phase transformation non-linearity, the surface heat flux evolution is estimated by an inverse algorithm. The experimental validation of both methods is performed in XC42 and XC80 steels case.

In this review, we report on the use of low pressure plasmas for elaborating materials at the heart of solid polymer fuel cells (SPFC), especially electrodes and the membrane electrolyte. Electrodes are formed using plasma sputtering techniques while the ion conducting membranes are built up using plasma polymerization. Fuel cell performance will be improved by these approaches. The electrode catalyst profile is optimized while membrane working temperature is increased and methanol crossover is lowered compared to conventional PEM fuel cells.

This paper presents a novel dual plasma enhanced chemical vapor deposition (PECVD) process developed to grow carbon nitride nanofibres (CN-NFs) at room temperature (RT) and its basic version used to grow multi-walled carbon nanotubes (MWCNTs) at temperatures as low as 550 °C. The dual process alternates two low pressure-high density plasmas, one inductively coupled (ICP) and the other one excited by distributed electron cyclotron resonance (DECR). MWCNTs can be synthesized using only the DECR plasma source. The paper focuses on the comparison between CN-NFs and MWCNTs detailing their structure as revealed by transmission electron microscopy (TEM), X-ray photo electron spectroscopy (XPS) and Raman spectroscopy.