[en] The effect of Be (beryllium) addition and the influence of cooling rate on the solidification path of the icosahedral (i) phase in conventional casting Al_62-xBe_xCu_25.5Fe_12.5 (x=0,1,3,5,7 at.%) alloys were investigated by means of X-ray diffraction, differential thermal analysis, SEM and EDX analyses. The addition of Be has been found to modify the i-phase formation mechanism from peritectic reaction to primary solidification. The volume fraction of the i-phase has been observed to increase from 45% for x=0 to 90% for x=7. These results suggested that the substitution of Al by Be is favorable for the increase of the quasicrystal-forming ability (QFA) of the i-phase. Two parameters have been proposed for defining and assessing the QFA for i-phase formed by peritectic reaction. These parameters can be expressed by the reduced quasicrystal transition temperature T_rq=T_p/T_l and the reduced undercooling ΔT_r=ΔT_lp/T_l, respectively, (T_l: liquidus temperature, T_p: peritectic peak temperature, and ΔT_lp=T_l-T_p: freezing range of primary phase)

[en] The cryogenic targets of the Laser Megajoule Facility (LMJ) are hollow spheres. Their internal wall is covered by a solid cryogenic fuel layer. These spheres are filled by permeation through the material. The filling procedure is optimized at room temperature or more (350 K) due to the fact that the permeation coefficient is increases with temperature. At filling temperature, the required pressure is between 1000 and 1300 bar. A difficulty is to prevent the buckling of the shell under the outer pressure during the filling procedure. So the rate of increase in pressure must be limited. A cryogenic compressor has been built to meet this purpose. The pressure delivered by the compressor is governed by the temperature of the (double) condensing cell that has an overall capacity of 90 cc of liquid or ice. To resist the high level of pressure, each condensing cell, made out of stainless steel, consists of an annular shape with numerous small diameter (5 mm) cylindrical bores. An electron-beam-welded cover collects the bores to a tube in connection with HP circuit. An inner/outer copper jacket is hard soldered on the cells for thermal homogeneity. Cooling to 15 or 20 K may be provided either by a Gifford-MacMahon cryorefrigerator or by a liquid helium flow. The beginning of the cool-down is boosted by a liquid nitrogen forced-flow. The complete cool-down time from 300 to 10 K may be decreased to 4 h. To achieve the maximal pressure, the condensing cells may be warmed up to 300 K by means of a accurately driven 600 W heater. This heater may be controlled either by temperature (15-25 K) or by pressure (25-300 K). Depending on the volume to be filled, the total duration of pressure ramping is in the range of 3-4 to 48 h (or more if needed). The increase of pressure versus time may be linear or have another shape. A computer program can control this slope in the range of approximately 0.1-2 bar/min for a 270 cc receiver volume

[en] Complete text of publication follows. Synthetic polymeric membranes have gained interest in separation science, engineering and technology. Fluoropolymers and especially poly(vinylidene fluoride) (PVDF) are used for such applications. Indeed they are well-known for their good properties in terms of chemical, thermal and electrical stabilities, inertness to acids, solvents and oils, and high resistance to ageing and oxidation. However, the high hydrophobicity of the PVDF membrane could limit its application when the fluid phases to be treated are dispersed in an aqueous medium. Therefore there is a need for the development of new surface modification processes, which renders the membrane more hydrophilic and which are clean and robust enough to be used in industrial field. This work focuses on the γ-ray induced grafting of different hydrophilic monomers onto a PA-reinforced PVDF membrane. These polymers are known to be radio-sensitive, and radicals can be generated on both components and their relative proportion determined by ESR. The influence of various parameters was evaluated, related either to the radiation process or the polymerization step, and a global methodology based on thermal properties, viscosimetry and spectroscopic techniques was used to point out the highly selective modification of the PVDF component of the membrane only. Finally, the surface properties of the membrane were evaluated and confirmed the membrane modification.

[en] Complete text of publication follows. Poly (vinylidene fluoride) is characterized by high intrinsic properties associated with the presence of a strong CF bond, responsible for its good chemical and thermal stability and its low surface energy. These properties provide a wide range of applications, from the medical field to the energy one. However, for some specific applications, excellent physicochemical affinity with a given liquid medium as well as a conservation of the dimensional integrity is required. These antagonist properties can be insured by crosslinking the material through an irradiation process such as the used of γ-ray. Compared to traditional methods which consist in a prior chemical modification of the polymers, this strategy can be applied on materials already processed. The mechanisms of the homopolymer radiolysis are relatively well known and involve free radical species which nature and concentration can be measured by ESR. The main scope of this work is to study and improve the crosslinking of PVDF-based polymers induced by γ-radiation. The macroscopic behavior of the irradiated material is related to the ability of the polymer to form crosslinking density can be evaluated from rheological measurements. Finally, a part of the study is focused on the increase of crosslinking efficiency. For this purpose, a chemical crosslinker which is sensitive to free radical reactions was incorporated into the polymer matrix. Thus, a significant improvement in properties is revealed. Moreover, the impact of radiation dose, crosslinker concentration or type of atmosphere during the radiation process is evaluated and their impact on mechanical properties is elucidated.

[en] As part of the French Inertial Confinement Fusion (ICF) program, CEA has developed Cryogenic Target Assemblies (CTAs) for the Laser MegaJoule (LMJ). These targets are filled by permeation with high pressure deuterium-tritium gas mixture. The evolution of the materials physical properties, particularly organic ones (PI and CH_x), which compose the target is unknown in these hard conditions. The polyimide and CH_x membranes permeation was studied in this context. The hydrogen and helium permeation parameters are unaltered for polyimide membrane after tritium ageing in the 20 K - 300 K temperature range: K(He) = 3.10^-14) exp(-16040/RT) mol.m^-1.s^-1.Pa^-1; K(H₂) = 2.10^-14 exp(-16050/RT) mol.m^-1.s^-1.Pa^-1. First results for the CH_x hydrogen permeation parameters without ageing tritium have been obtained: K(H₂) = 7.10^-13 exp(-10550/RT) mol.m^-1.s^-1.Pa^-1. New CH_x permeation results after tritium ageing are shortly waited. (authors)

[en] A more accurate life prediction for gas turbine blade takes into account the material behavior under the complex Thermo-Mechanical Fatigue(TMF) cycles normally encountered in turbine operation. An experimental program has been carried out to address the thermo-mechanical fatigue life of the IN738LC nickel-base superalloy. In the first phase of the study, out-of-phase and in-phase TMF experiments have been performed on uncoated and coated materials. In the temperature range investigated, the deposition of NiCrA1Y air plasma sprayed coating did not affect the fatigue resistance. In the second phase of the study, a physically-base life prediction model that takes into account of the contribution of different damage mechanisms has been applied. This model was able to reflect the temperature and strain rate dependences of isothermal cycling fatigue lives, and the strain-temperature history effect on the thermo-mechanical fatigue lives

[en] Zr₅₀Ni₂₇Nb₁₈Co₅ amorphous ribbons were hydrogenated using an electrochemical method. Under a current density of 30 mA/cm², the thermal stability of the amorphous phase was found to increase with the charging time. Hardness and fracture strength were found to be independent of charging time, indicating that the Zr-Ni-Nb-Co amorphous alloys preserved its mechanical integrity. (orig.)

[en] The purpose of this study is to evaluate the performance of immunoscintigraphy (IS) to diagnose hepatic metastases of colorectal carcinoma. PATIENTS: IS was performed in 19 patients because of rising serum titres of the tumor markers (12), to evaluate recurrent carcinoma confirmed by other examinations (6) and to assess the spread of an inoperable rectosigmoid tumor (1). METHOD: F(ab')₂ fragments of anti-CEA and 19.9 monoclonal antibodies were used (1.5 mCi if each). Planar scans of the liver were obtained 3 and 5 days post-injection.sup(99m)Tc sulphur colloid scintigraphy was performed at the same time. The data were compared with ultrasonographic and CT scan findings. RESULTS: In 9 cases, IS showed abnormal foci in the liver region. IS and ultrasonography were used simultaneously in 15 patients. The results agreed 13 times (8 negative, 5 positive); IS was positive twice while the ultrasound scans were negative. IS and CT liver scans were carried out simultaneously in 10 patients. The results agreed in all cases. 5 patients underwent laparotomy. Intraoperative findings agreed with IS data in all cases. Our results emphasize the importance of a painstaking examination of the liver region when using IS to diagnose colorectal tumor recurrence. The agree with those obtained by Deland et al. (Sem Nucl Med 15, 2-11, 1985). (Author)

[en] The Megajoule Laser cryogenic system fills, transports and inserts on the Cryogenic Target Positioner (CTP) individual Cryogenic Target Assemblies (CTAs), which are manipulated at about 20K by several cryogenic grippers.This CTA has to meet severe specifications imposed by implosion physics, its own thermal environment, and to respect a lot of interfaces with the permeation cell of the filling station, the several cryogenic grippers, the Megajoule laser interaction chamber,... Therefore, the CTA definition is very complex, and induces a lot of challenging tasks for its fabrication. During the last year, many improvements have been achieved allowing the realization of the first CTA prototype at scale one

[en] The corrosion behaviour of (Ni₆₀Nb₄₀) and Ni-Nb-M (M = Zr, Mo, Ta and Pd) meltspun ribbons was studied by electrochemical and chemical methods at PEMFC environments. The doping of Mo, Pd and Ta decreased the corrosion and passivation current densities, whereas the addition of Zr induced the opposite effect. To understand the change of corrosion behaviour induced by these additional elements, the surface composition and surface oxide layer thickness were analyzed by XPS method.