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LGEP 2014 ID = 1381; International audience; Semiconducting amorphous YBa2Cu3O6 + x (x < 0.5, a-YBCO) films of 140 nm to 880 nm thickness were deposited by direct current (DC) hollow cathode sputtering at low temperature (≈ 150 °C). The film microstructure was typically granular. Dielectric measurements from 100 Hz to 2 MHz were performed in the 300-430 K range to characterize the charge transport behavior. Alternating current conductivity values were extracted and the frequency dependence revealed a relaxation mechanism, which strength increased with temperature according to an Arrhenius law. The activation energy values matched those deduced from the temperature dependence of DC conductivity. The observed relaxation was in line with the hopping charge transport mechanism. A tri-layer device (metal/a-YBCO/metal on Si/SiO2 substrate) was processed using standard lithography. DC electrical tests confirmed the Schottky nature of the metal/a-YBCO contact. The optical response at 850 nm wavelength exhibited a high-pass behavior (maximum response at 100 kHz/1.6 μs time constant). The device current noise spectrum - of "blue" character - was investigated and discussed, in line with the frequency behavior of a-YBCO conductivity. A large signal/noise ratio was obtained, resulting in detectivity D* > 109 cm*Hz1/2*W− 1 in the 7 kHz to 100 kHz frequency range. These results are testifying for the very good performance of a-YBCO as room temperature pyroelectric sensing material.

Fretting corrosion damages are commonly observed when two metallic bodies, which are in contact with each other, are subjected to oscillatory motions of low amplitude. Such kind of degradation mode is often responsible for limited durability of aeronautical joints. In the present paper, a multifunctional duplex coating based on Si–C–N and diamond-like carbon (DLC) materials, combining corrosion resistance and good tribological properties is described. Amorphous hydrogenated SiC, SiCN, SiC/DLC and SiCN/DLC were deposited on steel substrates by a plasma assisted chemical vapour deposition (PACVD) technique, using tetramethylsilane (TMS), ammonia (NH 3 ) or acetylene (C 2 H 2 ) as gas precursors. Nitrogen incorporation has shown to improve the corrosion protection ability of SiC coatings. The corrosion behaviour and the tribological performance in aqueous media of SiCN/DLC coating have therefore been investigated. A test rig has been designed to validate the fretting resistance of this duplex coating for aeronautic applications. It was found that the combination of a SiCN-based PACVD sublayer with a DLC topcoat could provide an enhanced solution to withstand both fretting and corrosion.

This study was aimed to clarify the influence of secondary mineral constituents (iron and aluminium oxides, kaolinite) and organic matter on the determination of the phosphate-fixing capacity (PFIX) of well-drained low-activity clay soils. This study was done on soil samples (0–2 mm) and on their particle size fractions. The phosphate-fixing capacity, estimated by an isotopic exchange method, was highly related to the total iron content of the soils. The phosphate-fixing capacity of the particle size fractions was related to their mineralogical composition, and to the organisation of their constituents. H2O2 strongly increased the phosphate-fixing capacity of the soils and of their particle size fractions. Two hypotheses were proposed to explain this. Either H2O2 caused the formation in vitro of amorphous constituents with a high phosphate fixing capacity; or the destruction of organic matter by H2O2 caused the apparition of new surfaces previously masked by organo-mineral aggregation and/or caused the apparition on surfaces of fixation sites previously occupied by organic compounds. Key words: Phosphate-fixing capacity, low-activity clay soils, particle size fractionation, mineralogy, organic matter, H2O2 effect

Argon ion bombardment changes completely the nature of metal-Si contacts: the metal-Si(n) contact becomes ohmic, the metal-Si(p) contact becomes rectifying. The radiation effects are large even for energies as low as 100 eV. The amorphous surface layer is enriched in donors, thus giving rise to metal-n + -n and metal-n + -p structures. The conduction process is dominated by the amorphous-crystalline interface in the depth of the Si substrate. Comparison is made with amorphous-crystalline or damaged-crystalline junctions made by other techniques Les caracteristiques I(V) d'un contact metal-Si monocristallin faiblement dope sont radicalement modifiees par bombardement d'ions argon: le contact metal-Si(n) devient ohmique, le contact metal-Si(p) devient redresseur. L'effet d'irradiation est considerable meme pour des energies de l'ordre de 100 eV. La couche de surface amorphe, enrichie en donneurs, donne naissance a des structures metal-n + -n et metal-n + -p. La conduction est dominee par l'interface Si(amorphe)-Si(cristal) dans la profondeur du materiau. Les caracteristiques electriques sont comparees a celles de jonctions Si(amorphe)-Si(cristal) ou Si(endommage)-Si(cristal) realisees par d'autres techniques

The expansion of three solid solutions of the ferrite phase, C6A2F, C4AF and C6AF2, in the presence of CaSO4 · 2H2O, Ca(OH)2 and siliceous powder with water/solid ratio of 0.3, has been compared with that of two reference mortars: the first containing C3A, Ca(OH)2 and CaSO4 · 2H2O, the second C3A doped by 4,5% Fe2O3, Ca(OH)2 and CaSO4 · 2H2O. The expansion of mortars, based on the ferrite phase, has been observed to be a function of Al2O3 contents, and is much weaker than that of mortars based on C3A. For these last ones, the expansion decreases from C3A to doped C3A. The expansion due to the reaction of monosulfoaluminate and gypsum is much quicker if yielded by C3A. On the contrary that one due to the monosulfoaluminate yielded by ferrite is very small. Owing to these results, it seems that the low ettringite contents and the lower expansion of ferrites compared with the C3A are due not only to their low reactivity, but also to the formation of amorphous ferric compounds that cause a lowering of the hydration.

A knowledge of electron behaviour in the matter is needed, from a fundamental point of view in scanning electron microscopy, electron microanalysis and in source fields of space physics. The transmission and backscattering coefficients of amorphous and polycrystalline samples bombarded with monoenergetic electron beams are presented. A completely automated apparatus designed for measuring the coefficients is described. Semi-empirical laws have been established. These accurately describe the experimental results for energies ranging from 0.5 to 30 MeV Donnees des coefficients de transmission et de retrodiffusion de cibles amorphes ou polycristallines bombardees par un faisceau d'electrons monocinetiques. Description de l'appareillage utilise