[en] The paper relates to integrating technology in a changing organisation of Elf Aquitaine. There is a strong pressure to cut costs and be more effective in the company's operations. A process was initiated in 1994 to re-analyse its E and P (Exploration and Production) research and development (R and D) in order to enhance its alignment with the company assets needs, with a subsequent prioritization of R and D projects. The integration included a strategy for cooperation with other oil and service companies. The author presents the process set up to align the company's R and D program to the business needs of its operations, the various levels of cooperation used, and finally an illustration, in the domain of the geosciences, of the various facets of the ongoing cultural revolution which is required to reach a true integration. 11 figs

[en] In this paper, it is shown how an optical birefringence technique can be used to determine drying stresses in alumina films. The specimen geometry consists of a transparent plate as a substrate material that is coated on both sides with colloid dispersions. The homogeneous compressive stress in the substrate is determined from the optical retardation of a laser beam. The tensile stress in the coating can be easily calculated from the force balance, without any assumptions for its mechanical properties. The stress measurement principle based on photoelasticity, calibration of the experimental setup and initial results on drying stress evolution in alumina films are presented. (paper)

[en] Due to the unique combination of excellent thermal properties, low sputter yield, hydrogen retention and activation, tungsten is the main candidate for the first wall material in future fusion devices. However, its intrinsic brittleness and its susceptibility to operational embrittlement is a major concern. To overcome this drawback, tungsten fiber reinforced tungsten composites featuring pseudo ductility have been developed. Bulk material can be successfully produced utilizing chemical vapor deposition of tungsten fabrics. However, a fully dense composite with a high fiber volume fraction is still a huge challenge. Therefore, a model is currently developed in Comsol including the complex coupling of transport phenomena and chemical reaction kinetics. To validate the model with experimental data, fibers were deposited in heated tubes under controlled parameter variation. The temperature and tungsten growth rate were measured along the fibers and inner tube surfaces for different heater temperatures, partial pressures and gas flows. With the experimental results the prediction of the model has been improved. As next step the model will be applied to design infiltration experiments to fabricate fully dense Wf/W composites with a high fiber volume fraction.

[en] Highlights: • A detailed insight in the development of graded tungsten/steel coatings is given. • The optimized graded coatings show the envisaged highly dense, graded microstructure. • Detailed evaluation of stress profiles through the coatings are given. - Abstract: As structural materials for future fusion power plants, reduced activation ferritic martensitic steels as EUROFER97 can be used. Unfortunately, the interaction of the plasma with the steel would result in a limited lifetime, so protective layers are investigated. An excellent protective material is tungsten, as it shows unique properties with respect to low sputtering, high melting points and low activation. However, the mismatch of thermo-physical properties between tungsten and EUROFER97 can lead to large stress levels and even failure. A possible way to overcome this problem is the use of functionally graded material (FGM). The paper will describe the manufacture of these FGMs by vacuum plasma spraying and their characterization. First of all, two different feeding lines have been used to produce the coatings. A major problem lies in different melting points of tungsten and steel. So the particle size distribution has to be adjusted to achieve sufficient melting of both materials during the spray process. In a second step, the feeding rates were optimized to obtain the wanted amount of tungsten and steel phases in the graded structures. In a thermal spray process, the gradient cannot be made continuously, however it has to be applied in a step-wise manner. In this investigation, samples with 3 and 5 different concentrations (excluding the pure steel and tungsten part) have been produced. The microstructures of these layers have been investigated. In addition, hardness was measured and the residual stress state was determined by the hole drilling method.

[en] The sintering behavior of nanocrystalline ZnO was investigated at only 250 °C. Densification was achieved by the combined effect of uniaxial pressure and the addition of water both in a Field Assisted Sintering Technology/Spark Plasma Sintering apparatus and a hand press with a heater holder. The final pure ZnO materials present high densities (>90% theoretical density) with nano-grain sizes. By measuring the shrinkage rate as a function of applied stress it was possible to identify the stress exponent related to the densification process. A value larger than one points to non-linear relationship going beyond single solid-state diffusion or liquid phase sintering. Only a low amount of water (1.7 wt%) was needed since the process is dictated by the adsorption on the surface of the ZnO particles. Part of the adsorbed water dissociates into H⁺ and OH⁻ ions, which diffuse into the ZnO crystal structure, generating grain boundaries/interfaces with high defect chemistry. As characterized by Kelvin Probe Force Microscopy, and supported by impedance spectroscopy, this highly defective grain boundary area presents much higher surface energy than the bulk. This highly defective grain boundary area with high potential reduces the activation energy of the atomic diffusion, leading to sinter the compound at low temperature.

[en] Material issues pose a significant challenge for the design of future fusion reactors. Recently progress has been made towards fully dense multi short-fibre powder metallurgical production of tungsten-fibre reinforced tungsten (W_f/W) as well as optimizing the process understanding for the routes using chemical vapour deposition (CVD). For CVD-W_f/W weaves and textile preforms are being used to facilitate large scale production. Classically 150 μm tungsten fibres supplied by OSRAM GmbH have been used. In order to facilitate the better use of textile processes less stiff 16 μm filaments are being evaluated. The strength of the 16 μm filament is at 4500 MPa and thus significantly higher than the strength of the 150 μm fibre (∼2500 MPa) (in the as-fabricated state). Better weavability allows a more flexible use of fibre preforms Two main yarn production routes have been investigated: covered yarns where a set of tungsten filaments is held together by a PVA (Polyvinyl alcohol) cover and braided yarns. In order to allow a comparison to the previously used single fibres, yarns with ∼140 μm effective diameter were produced. Braided yarns with tensile strength of 2500 MPa and 6% strain at fracture and twisted yarns with tensile strength of 4500 MPa and 3% strain at fracture. For both yarns single fibre CVD samples have been produced to investigate the infiltration properties of the yarns and thus their applicability for the CVD route. A dense infiltration is observed for all yarns under investigation. (topical issue article)

[en] Highlights: → A new differential chip calorimeter device for high temperatures in various atmospheres and pressures is presented. → The calorimeter chip itself consists of free-standing silicon-nitride membrane beams with the heated sample area at their tip. → The operability of the device was proven up to 1093 K. → The device is operated as differential AC-calorimeter to maximize sensitivity. Alternatively, the calorimeter could also operate as a DSC. → The heat-transfer-model of A. Minakov for addenda calibration and heat capacity calculation can be applied within the known limits. - Abstract: A nanocalorimeter operating in various gas atmospheres and under controllable pressure at temperatures at least up to 1093 K is presented. It was developed to investigate nano-sized samples like nanoparticles and thin films under variable conditions. A special chip with two facing measurement cells for differential measurements was designed. Each cell consists of a thin, free-standing beam of silicon nitride instead of a continuous membrane. Joule heaters and temperature sensors are located at the tip of the SiN cantilevers. The calorimeter chip is mounted in a mobile measurement chamber that allows for preparation of surface-sensitive materials in a glove box. Subsequently the chamber is transferred to the measurement device. The chips are operated as AC calorimeter for sensitive detection of phase transitions. The functionality was demonstrated by calibration with different reference substances. Frequency scans with varying temperatures and gas atmospheres were performed to test the frequency dependency of the chip.

[en] Highlights: • CVD/CVI of W on multiple adjacent fibers was modeled using COMSOL Multiphysics. • Coating growth simulated by transient FEM mesh deformation and remeshing. • Gas-to-surface and surface-to-surface interactions were considered. • Partial pressure inputs obtained from a stationary macroscaled reactor simulation. • Experimental validation via coating thickness, pore structure and relative density. Tungsten (W) has a unique combination of excellent thermal properties, low sputter yield, low hydrogen retention, and acceptable activation. Therefore, W is presently the main candidate for the first wall material in future fusion devices. However, its intrinsic brittleness and its further embrittlement during operation bears the risk of a sudden and catastrophic component failure. As a countermeasure, tungsten fiber-reinforced tungsten (W${}_f$/W) with extrinsic toughening is being developed. A possible synthesis route is chemical vapor deposition (CVD) using heated W fabrics as substrate. The challenge is that the growing CVD-W can isolate domains from precursor access leading to strength-reducing pores. To deepen the process understanding and to optimize the CVD parameters, models were developed with COMSOL Multiphysics and validated experimentally. W deposition rate equations as function of the temperature and the partial pressures of the precursors H${}_2$ and W${\mathrm{F}}_6$ were experimentally validated in previous work. In the present article, these equations are applied to obtain partial pressures within the CVD reactor. The results are taken as input for transient simulations in the microscale, in which W coatings, growing onto multiple adjacent W fibers, were simulated via mesh deformation and remeshing. The surface-to-surface contact of the W coatings and the corresponding potential pore formation were simulated by implementing sophisticated deposition rate stop conditions. Within the measuring uncertainties of $\simeq \pm$1%, the models are validated successfully by experimental comparison regarding the deposition rate, pore structure, and relative densities ranging from 0.6 to 0.9.

[en] The present experiment exploits the interference between the Deeply Virtual Compton Scattering (DVCS) and the Bethe-Heitler processes to extract the imaginary part of DVCS amplitudes on the neutron and on the deuteron from the helicity-dependent D((rvec e), e'γ)X cross section measured at Q²=1.9 GeV² and x_B=0.36. We extract a linear combination of generalized parton distributions (GPDs) particularly sensitive to E_q, the least constrained GPD. A model dependent constraint on the contribution of the up and down quarks to the nucleon spin is deduced