G. Blondiaux

Hybrid gadolinium oxide nanoparticles combining imaging and therapy

The cytotoxicity of luminescent paramagnetic gadolinium oxide nanoparticles activated by harmless thermal neutron irradiation was evaluated on a luciferase coding gene transfected lymphome cells (EL4-Luc). Cellular uptake of nanoparticles was determined by fluorescence and magnetic resonance imaging and by ICP-MS analyses while the metabolic activity of irradiated EL4-Luc cells was monitored by bioluminescence. The alteration of the irradiated cells depends both on neutron irradiation dose and on gadolinium content within cells. In addition to their dual modality imaging ability, the application of these multifunctional particles for neutron capture therapy can be envisaged.

Helium behavior in UO2 polycrystalline disks

AbstractThe behavior of helium implanted in sintered uranium dioxide disks has been investigated as a function of annealingtemperature. UO 2 disks have been implanted with 1 MeV 3 He at a nominal fluence of 5·10 16 3 Hecm 2 using a Van deGraaff accelerator. The 3 He(d,a) 1 H nuclear reaction analysis method was used to determine the helium depth profile inthe UO 2 disks. Partial flaking was observed after annealing at 500 C for local He concentration of 1 at.%. Afterannealing at 600 C flaking has affected the whole surface. The formation of helium bubbles is discussed. 2003 Elsevier B.V. All rights reserved. PACS: 66.30.h; 61.82.m; 81.05.Je 1. IntroductionThe release of fission gases, mostly Xe, from UO 2 and spent fuels has been extensively studied since themiddle of the 1960s [1–5]. The solubility of these gases isextremely low in UO 2 and, as a consequence, the gasatoms tend to precipitate into bubbles. In irradiatedfuels, a high density ( 10 17 cm 3 ) of small intragranularbubbles of about 2 nm uniformly distributed in thematrix are observed [6,7]. The size of the bubbles in-creases and the concentration decreases slightly withincreasing temperature and burnup. At higher burnupand/or temperatures a second bubble population is cre-ated with a larger mean diameter (10–20 nm) [7]. Theprecipitation of bubbles has also been demonstrated foruranium dioxide samples implanted with Kr and Xe evenat temperatures as low as 300–350 C [8,9].Fewer experiments have been performed on the be-havior of helium gas produced by alpha decay of acti-nides [10,11]. Yet the amount of helium produced afterirradiation are large in particular in the case of MOXfuels: the amount of helium produced in MOX (burnup47.5 GWd/tU) after 10000 years is evaluated at 6700cm

Use of channeling in association with charged particle activation to study the position of light elements at trace level in crystals: The case of carbon in GaAlAs prepared by MO-VPE

Abstract Ion channeling and charged particles activation were combined to determine the lattice position of carbon impurities at sub-ppm levels in the GaAlAs lattice. The 12 C(d, n) 13 N reaction was used applying a 2.7 MeV deuteron beam. For GaAlAs epitaxial layers prepared by MO-VPE, carbon was found to be mostly interstitial in a tetrahedral position for low concentrations and mostly substitutional probably on an arsenic site, for higher concentrations.

Elaboration, characterization and electrical properties of NaAlO thin films

Abstract The ionic conductivity of NaAlO thin films (0.1–1.5 μm thick) deposited by r.f. and r.f.-magnetron sputtering was analyzed by the complex impedance method. The stability, the microtexture and the composition of the deposits are closely dependent on the operating conditions. The sputtering parameters were adjusted in order to optimize the deposition process. The combination of r.f. power and partial pressure of oxygen allows various sodium concentrations to be obtained in the NaAlO deposits. The ionic conductivity of these films follows an Arrhenius law with temperature and exhibits a maximum for the atomic ratio Na/Al = 0.08 ± 0.01 .

Elaboration and ionic conductivity of LiAlO thin films

Abstract Thin films (thickness: 0.2 to 2 microm) of LiAlO mixed oxides were obtained by rf-magnetron sputtering in order to prepare ionic conductors. The stability, microtexture and composition of the deposits depend closely on the operating conditions. The conductivities of these films were measured using the complex impedance method. Their electrical conductivity follows an Arrhenius law and exhibits a maximum for a lithium content corresponding to a Li/Al ration of 0.13.

Contribution of nuclear analytical techniques in optimization of Li-Ge-O thin films

Abstract Compositions of Li–Ge–O electrolyte thin films (0.1 to 3 μm thick) deposited by r.f. sputtering were determined by Rutherford backscattering spectrometry (RBS) and proton induced gamma-ray emission spectroscopy (PIGE). The aim of this paper is to illustrate the interest of these techniques in composition determination of thin films. The use of these techniques allows the optimization of Li–Ge–O thin films composition giving the highest ionic conductivity.

Thermodynamic and Experimental Study of the Chemical Vapor Codeposition in the Silicon‐Boron‐Carbon System at 1400 K

The results of a thermodynamic and experimental study of the codeposition of three elements, silicon, boron, and carbon, by a classical chemical vapor deposition technique in a hot-wall reactor are compared. The initial gaseous mixture consisted of methyltrichlorosilane, boron trichloride, and hydrogen. By the thermodynamic approach, the nonstoichiometry of boron carbide was described from B[sub 4]C to B[sub 10]C, and a comparison can be made between accurate thermodynamic calculation and experimental compositions measured at a given position on the substrate. The thickness and composition uniformity was also studied as a function of the inlet gas composition. The codeposits were first obtained on graphite, but the final purpose was to extend the process to composite materials. When fixed conditions of temperature (T = 1400 K) and total pressure (P = 0.395 atm) were employed, the influence of the total gaseous flux was shown to be great, especially in a hot-wall reactor. The total flux can change the deposition results because of either the depletion phenomenon or some departure from equilibrium.

7Be Recoil Implantation for Ultra-Thin-Layer Activation of Medical Grade Polyethylene. Effect on Wear Resistance.

Abstract Wear of ultra-high-molecular-weight-polyethylene (UHMWPE) is usually measured by gravimetric methods making laboratory wear tests a time consuming exercise. Methods for the determination of polyethylene wear with a higher sensitivity would reduce test times and costs. One of these alternative methods is ultra-thin-layer-activation (UTLA), which relies on recoil implantation of heavy radioactive nuclei, such as 7 Be, by using light mass particle beams. However, the possibility of damages within the polyethylene surface, which would have consequences on its wear behavior, cannot be excluded. In this work the effect of an implantation of 7 Be on wear of a medical grade UHMWPE was studied using a block-on-cylinder screening wear tester. The results show that the implantation of UHMWPE with 7 Be recoils under the implantation conditions chosen does not alter the tribological behavior of medical grade UHMWPE.

Ultra thin layer activation by recoil implantation of radioactive heavy ions: applicability in wear and corrosion studies

Abstract A new calibration procedure is proposed for the application of recoil implantation of radioactive heavy ions (energies between a few hundred keV and a few MeV) into the near surface of materials as part of a research programme on submicrometric wear or corrosion phenomena. The depth profile of implanted radioelements is performed by using ultra thin deposited films obtained by cathode sputtering under argon plasma. Two curves for 56Co ion in nickel have been determined for implantation depths of 110 and 200 nm, respectively, and stress the feasibility and reproductibility of this method for such activated depths. The achieved surface loss detection sensitivities are about 1 and 2 nm respectively. The on line detection mode is performed directly on the sample of interest. A general description of the method is presented. A study of the reaction kinematics followed by a general treatment on the irradiation parameters to be adopted are also developed with the intention of using the ultra thin layer activation method (UTLA) to further applications in research and industry.

Contribution of nuclear analytical techniques in deposition and optimization of thin amorphous films

Abstract Compositions of M-Al-O thin films (M = Li, Na; 0.1–2 μm thick) deposited by rf and rf magnetron sputtering were analyzed by nuclear analytical techniques (Rutherford backscattering spectrometry (RBS) and proton induced gamma-ray emission spectroscopy (PIGE)). The aim of this paper is to illustrate the use of these techniques in composition determination of amorphous thin films. Nuclear methods are compared with energy dispersive X-ray spectrometry (EDS) and show good agreement. With the help of nuclear techniques the Li-Al-O and Na-Al-O deposition process was optimized.