This paper is devoted to the theoretical study of the influence of thetemperature and of the doping on the piezoresistance of N-type silicon. In the firststep the fractional change in the resistivity caused by stresses is calculated in theframework of a multivalley model using a kinetic transport formulation based on theBoltzmann transport equation. In the second step shifts in the minima of theconduction band and the resulting shift of the Fermi level are expressed in terms ofdeformation potentials and of stresses. General expressions for the fundamentallinear, π11 and π12, and non-linear, π111, π112,π122 and π123, piezoresistance coefficients are then derived. Plots ofthe non-linear piezoresistance coefficients against the reduced shift of the Fermilevel or against temperature allow us to characterize the influence of doping andtemperature. Finally some attempts are made to estimate the non-linearity for heavilydoped semiconductor gauges.

Two different lead ion positions with tetragonal and orthorhombic localsymmetry were revealed in PbZrO3 ceramics on the base of 207Pb NMRspectra measurements at room temperature. The obtained data and theiranalysis on the base of the spectra shape calculations are in agreement witha symmetry of Pbam nonpolar group space of PbZrO3. The comparison ofobserved spectra in PbTiO3 and PbZrO3 with calculated spectra allowingfor resonance frequency chemical shift and spin-spin interaction show that the displacements of lead and oxygen ions are not random quantities inthe investigated PbZrO3 ceramic samples.

The AC magneto-electric properties (including Faraday rotation, etc.)of a metal-dielectriccomposite are considered in the quasi-static regime.Resonances appear at modified values of the surface plasmon and cyclotronfrequencies, which depend on the applied magnetic field as well as on the microstructure.Whenthe microstructure is periodic and has more than one characteristic lengthscale, the electric permittivity can exhibit a strong dependence on boththe magnitude and the direction of the applied DC magnetic fieldin the vicinity of one of those resonances.The possibility of observing this effect in a suitably fabricatedcomposite film is discussed.

Crystal Orientation Mapping (COM) is a new state-of-the-art technique for makingspatially specific orientation measurements based on the automatic analysis ofelectron backscatter diffraction patterns. The main aim of the work reported is todemonstrate the quantitative application of COM for characterising local orientationperturbations in the vicinity of triple junctions in an Al-3wt%Mg alloy deformed 5%in tension. First, the hardware configuration of the EBSD system is described and theoptimum microscope operating conditions for setting up a COM are determined bymeasuring the spatial resolution of EBSD patterns in pure Al and Ni specimens. Forthis particular investigation, an accelerating voltage of 20 kV was found to be optimum for mapping, resulting in spatial resolutions of 0.51 μm and 0.42 μmfor Al and Ni respectively. Secondly, to provide a visual representation of localorientation perturbations in the vicinity of a triple junction, a COM and patternquality map are presented. The “raw” orientation data extracted from the COM wasquantified using several different post-processing methods. The methodology associatedwith each is discussed and comparisons of the pattern of orientation perturbations aremade using the same “raw” data set.

The PbO–Nb2O5 phase diagram has been investigated, using electron diffractionand high resolution electron microscopy (HREM), for [Pb]/[Nb] ratios between 1 and1.25. Apart from the basic pyrochlore structure, different long periodsuperstructures, forming a homologous series Pb2n+1Nb2n−1O7n−1 based onthe pyrochlore structure have been found. Members with n = 5, 7, 9, 11 have beenobserved and their structure determined based on electron diffraction and HREM. Imagesimulations allow studying the influence of cation and oxygen vacancies in the basicstructure. Ordering of oxygen vacancies could be detected while no cation vacanciesare observed. Deviations from the perfect structure and ordered stacking defects arediscussed.

Hematite particles have been synthesized by a one step thermohydrolysis of nitrate iron (III) solutions. The microwave system (RAMO system) designed by the authors is able to induce very fast heating rates within an autoclave. These operating conditions induce precipitation reactions in the entire volume of the reactor. These precipitation conditions lead to instantaneous nucleation of monodisperse particles (separation of the nucleation and growth events). These results indicate that it should be possible to produce very well-crystallized hematite particles which can be used as precursors for production of magnetite or maghemite.

The map of 3D curvatures of a porous medium characterizes most of its capillary properties. A model for directly computing curvatures from athree-dimensional image of the solid matrix of a porous medium is presented. Aprecise distance map of the object is built using the “chamfer” distance of discretegeometry. The set of local maxima of the distance map is used for quick location ofthe normal to each point P of the object's surface. The normal being known,principal radii of curvature are computed in 2D and lead to 3D curvature. This modelwas validated on geometric shapes of known curvature, then applied on a natural snowsample. The snow image was obtained from a serial cut (performed in cold laboratory)observed under specularly reflected light. Views of both fresh and sublimated sectionswere taken for each of the 64 section planes: this allowed easier distinction betweensnow and filling medium and made possible automatic contouring of section planeimages. Curvature maps computed from pore and grain phases respectively were found tobe in excellent agreement for each tested object shape, including the snow sample.

The properties of porous silicon microcavities impregnated with a laser dye are investigated by photoluminescence and reflection measurements. The spontaneous emission spectrum of the optically excited rhodamine 800 is drastically modified by microcavity effects: the peak emission intensity is increased, the linewidth is narrowed. These results demonstrate that using all porous silicon or dye-filled microcavities provides new possibilities to improve the properties of photonic devices.

Considering the increase of the fault current level in electrical network, the current limiters become very interesting. The superconducting limiters are based on the quasi-instantaneous intrinsic transition from superconducting state to normal resistive one. Without detection of default or given order, they reduce the constraints supported by electrical installations above the fault. To avoid the destruction of the superconducting coil, the temperature must not exceed a certain value. Therefore the design of a superconducting coil needs the simultaneous resolution of an electrical equation and a thermal one. This papers deals with a resolution of this coupled problem by the method of Monte-Carlo. This method allows us to calculate the evolution of the resistance of the coil as well as the current of limitation. Experimental results are compared with theoretical ones.

Electron transport properties in tensile strained Si-based materials are theoretically analyzed using Monte-Carlo calculation. We focus our interest on in-plane transport inSi and Si1−y Cy (y ≤ 0.03), grown respectively on 〈001〉Si1−x Gex pseudo-substrate and Si substrate, with a view toField-Effect-Transistor application. In comparison with unstrained Si, the tensilestrain effect is shown to be very attractive in Si: drift mobilities greater than 3000 cm2/Vs are obtained at 300 K for a Ge fraction mole of 0.2 in thepseudo-substrate. In the Si1−y Cy /Si system, that does not need anypseudo-substrate, the beneficial strain effect on transport is counterbalanced by thealloy scattering whose influence on mobility is studied. If the alloy potential isgreater than about 1 eV, the advantage of strain-induced reduction of effective massis lost in terms of stationary transport performance at 300 K.

A magnetoelectrostatic trap consists of a spindle cusp magnetic field configuration and transverse electrostatic potentials applied to the electrodes at the ring and point cusp ends. Plasma confinement studies in this trap is made with a single positive charged particle. When the plasma is injected in such a system a potential well for the positive ions is formed where they could be trapped. Three-dimensional trajectory of the particle was developed by a single-gap mathematical model. The trajectory of a positive ion in the system was analyzed numerically by Runge-Kutta fourth order method. The equations of motion were constructed from the Hamiltonian function. The three-dimensional trajectory of an ion was traced for various possible input parameters. When the electrostatic potentialand angle of injection are kept zero almost all the injected ions (post-cusp region) escape through the aperture. But there exists a critical injection velocity and magnetic field intensity to reflect the particle at axial cusp region. In this forward and backward motion the particle moves in a helical path encircling about the same magnetic lines of force. While introducing some potential difference to the electrodes in the cusp ends, the particle exhibits a "double helix" trajectory about the axis of the spindle cusp configuration. This double helical path leads long duration confinement of the particle in such a system and obviously cusp losses are suppressed. The results are reported for a wide range of input parameters.

Anode for a non-transferred DC plasma spray torch was designed to improve electrothermal efficiency. A theoretical calculation was made for the electrothermalefficiency in a DC plasma torch operating with argon at atmospheric pressure withpower level in the range of 5.2–20 kW using energy balance equations. ANOVA for thetwo level factorial design was done. Plasma gas flow rate, current intensity,nozzle diameter and length were found to influence the efficiency. The efficiencywas found to decrease with increase in current intensity and nozzle length and toincrease with increase in nozzle diameter and gas flow rate. The overall energy balance calculations showed that the heat transfer to the plasma-forming gas decreases with increase in arc current and the same was moresignificant at higher flow rates. Plasma jet velocity for different flow rates, input to the torch and nozzle dimensions was calculated from the gas enthalpy. Itwas found that the velocity increased with increase in the power input to the torchand gas flow rate and decreased with increase in nozzle length and diameter. The current–voltage characteristics of the torch operating with argon gas were studied for different gas flow rates. The Nottingham coefficients were calculated using least – square method.