Rapidly solidified Al–12.5 Si–1 Ni ribbons were prepared bymelt spinning. The Si solid solubility was extended to high values asdeduced from X-ray diffraction and TEM. This high solubility of Si wasfound to have significant effects on the various properties of this alloy.High values of electric resistivity was observed which was about four timesthe fully annealed values. Furthermore rapid solidification improved thetensile strength and the toughness of this alloy as compared with itsclassically solidified counter part. The relaxation kinetics was followedby isothermal resistivity measurements. The relaxation follows an equationwhich has the Johnson-Mehl-Avrami (JMA) form. No metastable phase wasobserved.

On one hand, the experimental crystallographic data of Chang andRead and the theoretical ones of Lieberman et al. permit a physicalapproach of the martensitic transformation of Au–47.5% at. Cd. On theother hand, an extension to the AuCd crystallographic system of the simplemicromechanical model, developed by Lexcellent et al. for CuZnAlsingle crystals, allows an efficient modelling of the tension-compressionand pure tension tests, performed on single crystals by Nakanishi et al. in the pseudoelastic range.

A new experimental method aiming to the characterization of self-affine rough surfaces is presented. Based on a three dimensional reconstruction of the relief from stereo pairs obtained with a scanning electron microscope, it allows a non-destructive quantitative analysis of fracture surfaces, with a xy and z resolution only slightly lower than the original images. The roughness index of the fracture surface of an aluminum alloy is recovered, as well as the Hurst exponents of reconstructed computer-generated fractional Brownian reliefs.

The electronic and magnetic structures of the perovskite CaMnO3 are self-consistently calculated assuming two crystal structures at the same formula unit volume within the local spin density functional theory and the augmented spherical wave (ASW) method. From the comparisons of energy differences between the different magnetic states the ground state configuration is an insulator with G-type ordering. This result together with the magnitudes of the magnetic moments are in agreement with experiment. The influence of mixing between Mn and O is found spin dependent from the analysis of the crystal orbital overlap population (COOP) which enable to describe the chemical bond. The calculations underline a feature of a half metallic ferromagnet which could be connected with the colossal magnetoresistance (CMR) property of related compounds.

From observations of extended dislocation nodes in β silicon nitride, possible stacking fault structures in the basal plane of this compound have been investigated. It has been found that stacking fault structure is locally analogous to α silicon nitride. A phase transformation α to β or β to α can also be achieved by cooperative shear of partial dislocations with $1/3\langle1\bar{1}00\rangle$ Burgers vectors.

The cationic composition of a titanium ferrite (Fe2.5Ti0.5O4) has been followed by XPS during its oxidation in cation deficient phases (without crystallographic transformation) in order to reveal a dynamic segregation phenomenon. Indeed, during this oxidation, an important modification of the chemical composition of the first layers of the material has been revealed: below 350 °C, the titanium ferrites surface becomes richer in iron and poorer in titanium. But, if the reaction is extended above 400 °C, some titanium can move to the surface. This phenomenon has been interpreted on the basis of the differences of mobility of the different ions which are present in the material. Finally, at 450 °C, on the surface of the spinel, the α–Fe2O3 phase begins to appear and hides the ferrite.

Preliminary results are presented from the study of grain boundary structurein bulk nanocrystalline copper using high-resolution electron microscopy. A recently developed method of image analysis is applied to an experimentalimage of a grain boundary between two copper grains. Maps are produced ofthe fringe spacing and the local rotation of the lattice as a function ofposition in the image. The analysis of the fringe spacing shows that nooxide layer exists between the copper grains. This confirms that thesurface oxide layer coating the copper particles can be eliminated duringthe formation of the bulk material. By studying the way the rotation of thelattice takes place across the grain boundary, an upper limit for theinterface width is obtained. The reliability and accuracy of the resultsare discussed.

The experimental results concerning the modification of the NeI emission spectra as well as the time evolution of both the discharge current and the yellow line intensity with the wavelength of 585.3 nm, at the H2 and/or SF6 addition to the Ne+1%Xe Penningmixture, are obtained for the narrow gap dielectric barrier discharges. The H2 andSF6 contribution to the depletion of the lower level 1s 2 through Penningcollisions and also the hydrogen participation to the feeding of the upper level2p 1 of the optical transition 2p 1−1s 2 of the neon have been revealed.

The chemical properties of the gaseous species generated in a humid airgliding arc discharge are investigated. Aqueous solutions are used as the targetsexposed to the plasma, and this allows to evidence strong acid and oxidizing effectson various solutes by means of spectrometric or potentiometric methods. The influenceof some working parameters such as the input gas flow, the distance from theelectrodes to the target or the electrode gap is examined on the chemical transformand simple experimental laws are derived. A general feature is observed for oxidationand suggests the occurrence of an auto-catalytic step in the relevant kineticmechanism.

The behavior of tetrafluoromethane microwave plasma (2% argon included) has been studied by emission spectroscopy during the treatment of hexatriacontane, a model for high density polyethylene. The evolution of the densities of F* atoms, and CF, CF* 2, radicals has been followed by using the actinometric technique with 2% argon added to the gas. The surface properties, such as surface energy and surface roughness were correlated to the emission intensity of reactives species in the plasma gas phase. We found that the evolution of the fluorinated species emissions in the plasma gas phase can be a direct indication of the surface modifications by the plasma. A mild exposure to the plasma can result in a great decrease of surface energy corresponding to the fluorination. The surface roughness only changes under drastic plasma conditions. Threshold ionization mass spectroscopy is applied to detect the fluorine atoms and CFx radicals. Time resolved measurements in pulsed plasma, give access to the decay rate of F atoms concentration in the afterglow, and to their sticking coefficient on different surfaces. The influences of the discharge parameters and of the surfaces (metal, silicon or hexatriacontane) in contact with the plasma are investigated. The results show that the plasma generated ions and/or UV radiations highly enhance the reactivity of the F atoms on polymer surface.

The characteristics of a low frequency (70 kHz) discharge with non-symmetrical configuration of electrodes in He–O2 mixtures were investigated. The Langmuir probe technique, emission spectroscopy, mass spectrometry and absorption spectroscopy were used for plasma diagnostics. The physicochemical properties of PET (polyethylene terephtalate) were analyzed via contact angle measurements and XPS spectroscopy. The presence of the oxygen is shown to modify both the densities of the helium metastable states and also the energetic character of the discharge. The very efficient loss of He excited species and in particularly the metastables, for amounts of O2 higher than a few percents, affects the surface modification in terms of crosslinking, and therefore the stability. This work has shown that one of the important species responsible for the crosslinking process leading to stable surface properties could be the helium metastables.

This paper addresses the problem of an actuator's load monitoring through a particular fault pattern effects analysis. A load's failure, like a dip of torque superimposed on a constant or sinusoidal steady state load, has an effect on the motor's supply currents. In some cases the high stress and the toxicity of the operating environment of the actuator lead to the inaccessibility of the motor and load set and don't authorize the positioning of sensors. Consequently we use the motor current spectral analysis for the detection of the faults that occur in the load.To propose a global method, this paper presents an approach for the automation of the monitoring and diagnosis processes and studies the capabilities of an easy tool, the spectrogram, to detect the apparition of the fault during the work of the actuator and the signature obtained with different kind of faults and supplies. It also proposes a methodology to determine the parameters of the dip of torque fault. To conclude this study, we show the validity area of the method to other king of failure patterns.

The photon scanning tunneling microscopy (PSTM) allows to characterize the surface topography with high resolution. This microscopy exploits the exponential decay of the evanescent field achieved by the total internal reflection under the surface sample. When the distance between the sensor and the surface becomes small (~ 100 nm), the non propagating photons of the evanescent field can be converted into guided propagating mode of polaritons. A bulk Silicon probe is used in the AFM experiment as a sensor of van der Waals forces.The aim of this paper is to discuss the influence of the atmospheric humidity on the PSTM measurements. We have showed that the theoretical predictions of the dielectrical capture model (DCM) are very different from the experimental results when the humidity level is higher than a threshold value (30%). We present the results obtained with TE polarization, but the same behaviour is found with TM polarization. Although, in this paper we do not propose a theoretical model explaining the deviations between DCM values and experimental, however we found a validity threshold for our experimental results and we have emited the assumption that under high humidity level the pollution film presents on the sample surface slide during the displacement of the probe.

We have built three optical frequency standards based on the two-photontransition of rubidium at 778 nm, and analysed their performance over a period of morethan three years. We discuss some systematic effects that could lead to the reproducibility we observe, and point out the possible improvements of the devices.We also examine the short and long term stabilities of the systems, and show that wehave reached their ultimate performances.

The true and apparent temperature of samples during the deposition of III-V layers by molecular beam epitaxy changes as a result of the variation in spectral emissivityϵ with layer thickness. Taking into account the infrared optical propertiesof these materials, we modelized the variations of the true sample temperature and theapparent temperature (as determined by pyrometric measurement) during the growth. Welimited our study to deposits involving at least one absorbing material (at thepyrometer wavelength), for example GaSb, InAs or InSb. We showed that our simple modelcan agree reasonably with experiments in the 400−500 °C temperature range.