Several ways using surface modification are commonly used to enhance thermal stability of polymer matrices. In this study, Continuous-Wave carbon dioxide (CW CO2) laser irradiation and atmospheric pressure non-thermal He plasma treatment on microporous poly(vinyl chlo-ride)/Silica composite have been investigated and compared. On one hand the alternative was based on the efficiency of the thermal energy afforded by CW CO2 laser irradiation and induced photodegradation processes to release HCl and form polyene sequences under well-controlled condition. On the other hand atmospheric plasma treatment involved surface modification by formation of unstable radicals, inducing crosslinking and dehydrochlorination. In both cases a global thermal stabilization of the composite was noticed by partial dehydrochlorination of PVC, even for short exposure time. The main effects observed after laser irradiation were related to the formation of a very dense structure on surface with very low chlorine content and an important chlorine atoms in-depth gradient on the cross section up to 150 μm in thickness; whereas atmospheric He plasma treatment led to a homogeneous decrease of the chlorine in-depth content due to the plasma interpenetration in the porous microstructure. Structural and chemical modifications both on extreme surface and in the thickness have been investigated respectively by Environmental Scanning Electron Microscope (ESEM) coupled with an Energy Dispersive X-ray analysis (EDX) and X-ray Photoelectron Spectroscopy (XPS). Composites thermal stability and investigation on chlorine release have been evaluated by Thermo Gravimetric Analysis (TGA) coupled with Mass Spectrometry (MS).

In this paper, we present a numerical modelling of a NPN SiGe heterojunction bipolar transistor (HBT) realized in an industrial 0.35 µm BiCMOS process, using our own software simulator “SIBIDIF”, taking into account some electrically active defects in the HBT device. The electric performances of this device can be penalized by the presence of defects inherent to the complex structure shrinking. For our devices, most of these relevant defects are located at the vertical interface between the spacers and the polysilicon emitter, due to the Reactive Ion Etching (RIE) process step. Nevertheless, their localization, as well as theirs effective density or their capture section, have an influence on the electric characteristics of the HBT's. As a check, we find some good agreement between our simulated results and some experimental ones. Our work is focused on the identification of defects responsible for the current fluctuations at the origin of low frequency noise or Random Telegraphic Signals in industrial submicronic BiCMOS technologies. Gummel characteristics are simulated in order to identify generation-recombination or trap assisted tunnelling process in the base current. We have shown that devices having an excess base current present random discrete fluctuations on the base current.

Hexagonal AlN thin films have been deposited by DC reactive magnetron sputtering at room temperature. For a first set of samples, sputtered AlN films were deposited on silicon Si (100) substrates. For a second set, AlN films were deposited on 200 nm (002) oriented AlN epitaxial layer obtained by Molecular Beam Epitaxy (MBE) on Si (111). X-ray Diffraction (XRD) and High Resolution Transmission Electron Microscopy (HRTEM) analysis of the synthesized films on Si (100) substrate have shown an amorphous phase close to the interface followed by a nano-crystalline layer exhibiting (100) and (002) orientations of the hexagonal AlN crystalline phase. Finally a relatively well crystallised layer with a single (002) orientation has been observed for the thickest films. This improvement of crystalline quality with film thickness has been consistent with a drastic decrease of the films stress from –1.2 GPa at 300 nm to no stress around 800 nm and even 0.3 GPa tensile stress for 1.5 μm thick film. This behaviour was different when epitaxial AlN was used as substrate. In fact, we have observed thanks to HRTEM images and Selected Area Electron Diffraction (SAED) patterns, that the AlN film deposited on such a substrate exhibits the same crystalline quality and have the same orientation as the AlN epitaxial layer during the first 500 nm of thickness. A further increase of film thickness has caused a decrease on the crystalline quality. The films became polycrystalline while preserving a (002) preferential orientation.

Efficient numerical models have been already developedin 2D to take into account the movement of electromagnetic deviceswith rotating parts in the framework of the Finite Element Method(FEM). When the movement becomes complex it leads to large meshdistortions. A remeshing step is then required which increases thecomputational complexity and can also lead, in some cases, tonumerical ripples on forces and torques due to the fieldprojections between old and new meshes. Moreover, remeshingprocedures in 3D remain an open topic. Meshless methods seem anappealing choice for alleviating the mesh constraints. The NaturalElement Method (NEM) which, has known a growing interest in thedomain of mechanics, allows to proceed in the meshless framework,avoiding one of the main drawbacks related to the vast majority ofmeshless techniques, as is the imposition of essential boundaryconditions. In this paper, a variant of the NEM, known asconstrained natural element method (C-NEM) is applied forsimulating electromagnetic machines involving rotating parts. Anew mixed strategy combining the finite element and theconstrained natural element methods is proposed and then tested byusing an appropriate error estimator.

Plasma Enhanced Chemical Vapour Deposited (PECVD) tensile nitride liners have been introduced in the 90 nm CMOS technology node to generate mechanical strain within the transistor silicon channel. With strain, because of the silicon piezoresistance effect, the electron mobility is enhanced within the silicon channel, so the nMOS transistor performance. Since that time, significant work has been carried out to develop silicon nitride films with enhanced tensile stress values to increase the gain provided by these process induced stressors along the introduction of the new technologies. For the 45 nm node, an additional UV post treatment has been introduced to achieve highly tensile residual stress. This study determines the relevant as deposited PECVD nitride film properties that modulate the final stress achievable after UV cure. Thanks to a simple stress model, it is demonstrated that as deposited nitride films must present a nitrogen rich composition and an intrinsic low density to become highly tensile after post UV treatment. With these design rules, nitride films with final stress of 1.6 GPa have been synthesized.

Investigations on ion transport mechanism in the new Ag+ ion conducting quaternary solid electrolyte systems: (1 − x)[0.75AgI: 0.25AgCl]: xKI, where 0 < x < 1 in mol. wt.%, are reported. The quaternary systems were prepared by solid solution reaction of an alternate host: `a quenched [0.75AgI: 0.25AgCl] mixed system/solid solution', instead of the traditional host salt AgI, and KI. The compositional dependent conductivity studies on the quaternary systems identified the composition: 0.7[0.75AgI: 0.25AgCl]: 0.3KI, as the Optimum Conducting Composition (OCC) having conductivity σ ~ 5.9 × 10−3 S cm−1 at 27 °C. For direct comparison of the room temperature conductivity behaviour of the quaternary OCC, AgI-based ternary solid solution composition: 0.8AgI: 0.2KI, resulting into the well-known superionic system: KAg4I5, has also been synthesized in the identical manner which exhibited σ ~ 1.12 × 10−2 S cm−1 at 27 °C. The conductivity of newly synthesized quaternary OCC was slightly lower than that of as prepared ternary KAg4I5. However, in the open ambient conditions $\sigma $ of OCC sample remained practically stable for over hundred hours while that of KAg4I5 decreased by more than two orders of magnitude in the same duration. The phase identification and material characterization studies on the quaternary OCC have been carried out using XRD and DTA techniques. The ion transport mechanism has been characterized on the basis of experimental studies on some basic ionic parameters viz. conductivity ( $\sigma $ ), ionic mobility ( $\mu $ ), mobile ion concentration (n), ionic transference number (t ion ) and ionic drift velocity (v d ). Solid state batteries have been fabricated using the newly synthesized quaternary OCC as well as KAg4I5 as electrolytes, sandwiched between Ag/I2 electrode couple and the cell potential discharge performances have been studied under varying load conditions.

This paper reports the characterization of lithium tantalite (LiTaO3) thin films deposited by sol gel process. Thin films were deposited on (001) sapphire substrates by spin coating. In order to study the effect of annealing temperature on the structural and optical properties, the films were annealed at several heating temperatures, ranging from 600 to 750 °C. From X-ray diffraction measurements it is confirmed that LiTaO3 films are highly c-axis oriented, the line width and the intensity of the (006) peak are sensitive to the variation of the annealing temperature and the best results were found at 700 °C. From SEM pictures it is found that the grain size increases from 100 to 200 nm when the annealing temperature is increased to 700 °C. From the optical transmittance and absorbance measurements, the band gap energy was extrapolated at about 4.6 eV which closely agrees with the LiTaO3 bulk value. Fourier transform infrared (FTIR) reflectivity and Raman backscattering were used as two complementary experiments to probe the zone center optical phonons in the lithium tantalite thin films.

This paper deals with reliability of motor drive systems. It focuses on the switching power converter which is the weakest drive part. It investigates a new architecture which provides intrinsic redundancy. The method used in this fault switch detection and diagnosis is based on a sliding mode observer. The original aspect of this new approach is that the observer influences the control algorithm in order to rule out or accept the possibility of the device failure. This leads to the right decision which induces the rebuilding of the converter topology. This fault tolerant control strategy assures continuous operation even though one switch failure occurs.

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.

Based on the dielectric-continuum model, the expression of polarization eigenvector, the dispersion relations, and the electron-phonon interaction Fröhlich-like Hamiltonian for interface optical (IO) phonons in multilayer GaN/AlN spherical heterostructures are obtained. As an application of the theory, the dispersion relations and electron-phonon coupling function strengths of the IO phonons are calculated for four-layer GaN/AlN/GaN/AlN spherical heterostructures. The results show that the lower frequency phonons have a much greater contribution to the coupling function $\Gamma _l^{IO} (r)$ than higher frequency phonons.

A NiTi shape memory alloy was subjected to low energy high current pulsed electron beam (LEHCPEB) irradiation. The samples were treated with the same electron beam parameters and increasing number of pulses. The treatment induces superfast melting, evaporation and rapid solidification at the top surface. As a result of selective evaporation of Ni, the Ti content was increased in the melted layer of the 5 pulse treated sample. However, for the 10 pulsed sample, a part of the vapor condensed on the surface. It is shown also that in the sub-surface, below the melted layer, the martensitic transformation was triggered due to the effects of the thermal stresses and shock waves propagating in the material.

To insure interoperability of transeuropean trains, new transmission systems (GSMR, Eurobalise) are developed in order to permit communications between trains and control centres. These systems have to be available and safe from an electromagnetic point of view, but the normalized methods to characterize electromagnetic noise in the railway environment are not convenient for these applications. This paper presents new experimental methods to characterize the electromagnetic noise on board trains which are studied in the framework of the European project “Railcom”. The results of measurements realized both in time and in frequency domains, are analysed and certain conclusions can be used as a first step to define a new standard for the considered systems.

In this paper, the FeSiBNbCu and FeSiBNbCu-Al coatings were synthesized using cold spray technique in order to produce ferromagnetic materials. Ultra-fine grain coatings are obtained using FINEMET nanostructured powders mixed with Aluminum. Various percentages of Aluminum characterized by its low hardness were taken in account. The obtaining coatings were formed of Aluminum matrix and randomly distribution of FINEMET particles. Indeed, magnetic measurements revealed a soft magnetic character for all the powders and the coatings. 25% of Al was considered as ideal to produce a homogenous coating with good soft magnetic properties.

Porous silicon layers (PSL) were fabricated by electrochemical etching and investigated by spectroscopic ellipsometry (SE) in the energy range 0.6−5 eV. Within the effective medium approximation (EMA) and through an optical model consisting of a mixture of void and crystalline silicon (cSi), we were able to determine the porosity (void concentration) and the thicknesses of the PSL. The PSL were divided into several sublayers in order to obtain the best agreement between measured and simulated spectra. Once the etching parameters have been controlled and by choosing the appropriate conditions, it was possible to design a distributed Bragg reflector (DBR) with a high reflectivity band centered at 800 nm. This DBR consists on stacks of alternate PSL having two different refractive indices.

A study on the characterization of small cracks by using eddy current testing (ECT) signal is presented. The significant parameters of the ECT data are selected using principal component analysis according to two approaches. The ECT signal inversion is then achieved using a parametric model trained with synthetic data obtained with a fast numerical simulation tool. The characterization procedure is then tested using experimental data. Results show that information can be obtained concerning the area of the cracks.

A full characterization of amorphous or nanostructured coatings at the microstructural level has some intrinsic difficulties associated with the lack of long range order and reference compounds, which often make difficult their study. Only by the combination of different characterization techniques is possible in many cases to achieve valuable chemical and structural information. In this paper, three different systems were used to illustrate how the combination of characterization techniques, as TEM associated to ED or EELS, EFTEM, SEM, XPS, RBS and XRD was determinant to correlate microstructure with deposition parameters and properties in such complex systems. The coatings were deposited on silicon and AISI M2 steel substrates by magnetron sputtering under different Ar/N2 gas mixtures from Ti and C targets (system 1 and 2) or a Si target (system 3). In each case, the performed characterization allowed to get a deeper understanding of the whole system and explain their mechanical response. The studied systems are:(i) Ti-TiN-CNx multilayered coatings: the chemical and structural analysis shows that a gradual enrichment in nitrogen and nitride phases from the metallic substrate to the CNx top layer is responsible for the improvement of the adhesion properties.(ii) Ti-C-N: the existence of a nanocrystalline TiC phase embedded in an amorphous carbon matrix is demonstrated by the microstructural and chemical analysis for samples prepared under pure Ar. When N2 is introduced in the gas phase, the nanocrystalline structure is not seen and the chemical composition is enriched in amorphous non-stoichiometric CNx .(iii) SiOx Ny : although the coatings present similar composition, small differences in microstructure are observed, which can be responsible for different mechanical properties.

A novel method, based on emission signal from the excitation transfer reaction: Ar*(3P2) + N2(X) $\to $ N2*(C 3 $\Pi_{u}$ ) + Ar, is proposed for the intensity calibration of the spectroscopic optical detection system in absolute scale. It is applied for the measurement of N(2P°) metastable atoms density in the Short Lived Afterglow (SLA) of a 440 Pa nitrogen discharge produced by a 433 MHz resonant cavity. This density is deduced from the absolute intensity of the forbidden N(2P°–4S°) line at 346.65 nm, whose transition probability is only 0.005 s−1. The N(2P°) density variation in the SLA resembles those of N2(A 3 $\Sigma_{u}$ ) metastable molecules and electrons or the emission intensities of first positive (1+), second positive (2+) and first negative (1−) systems of N2. It first decays after the discharge zone up to a minimum and hence increases by almost a factor of thirty to reach a maximum value of 6 × 1017 m−3 at the maximum of the SLA. It is proposed that N(2P°) density results from a local equilibrium between its production: N2(A 3 $\Sigma _{u}^{+}$ ) + N(4S) $\to $ N(2P) + N2(X 1 $\Sigma _{g}^{+}$ , v) and loss: N2(X 1 $\Sigma _{g}^{+}$ , v≥ 10)+ N(2P) $\to $ N2 (A 3 $\Sigma _{u}^{+}$ ) + N(4S) reactions, which strongly couple the atomic and molecular metastable states and hence recycle N2(A 3 $\Sigma _{u}$ ) metastable molecules produced in the SLA. The balance equation of N(2P°) density provides a N2(X 1 $\Sigma _{g}$ ; v≥ 10) density of 6.5 × 1020 m−3 at the maximum of the SLA. This corresponds to 1% of the total N2 molecules in vibrationally excited levels v≥ 10.

Primary power standards in the microwave domain are realized using a calorimetric technique, usually identified with the used measurement system, i.e., the microcalorimeter. It is adjusted for measurement of power ratios with a relative accuracy that, after an appropriate system calibration, is of order of 10−3, at least in the microwave domain (1 GHz–18 GHz). Hereby we describe the calibration process implemented at the Istituto Nazionale di Ricerca Metrologica (Italy) for realizing a coaxial power standard based on indirect heating thermocouples. Particular regard is devoted to describe the nearly ideal thermal load used for determining the microcalorimeter losses and their influence on the measurand accuracy.

This paper reports the first results of an ongoing research work on rapid surface alloying of an AISI 316L stainless steel by low energy, high current pulsed electron beam (LEHCPEB) with the aim of enhancing the corrosion resistance of this material against aggressive halide ions. A Ti powder layer was deposited on the substrate and in-corporate at the top surface by using LEHCPEB. Due to the rapid surface melting, liquid state mixing occurred and a Ti-rich layer formed. The alloyed layer contained a mixture of the $\alpha $ and γ phases because the addition of Ti favors the formation of α. The corrosion resistance of the AISI 316L stainless steel in the simulated body fluid was effectively improved after surface alloying by Ti.

Plasma-assisted nitriding is an attractive surface treatment for metallurgical surface modification to improve wear, hardness and fatigue resistance of austenitic stainless steels. However, this technique requires low temperature processing in order to avoid chromium nitride precipitation and hence the degradation of corrosion properties. This paper presents a low temperature high rate plasma nitriding process and will emphasis on the consequences of nitrogen incorporation on the metallographic and crystallographic properties of the sample surface.