Influence of Pt, Fe/Ni/Cr-containing intermetallics and deuterium on the oxidation of Zr-based materials

An in situ gas phase analysis technique and the ¹⁸O-SIMS technique are used to evaluate the transport of oxygen and hydrogen in oxidation of Zr-based materials. At 400 °C, it is found that oxygen dissociation efficiency decreases in the order: Pt > Zr₂Fe > Zr₂Ni > ZrCr₂  Zircaloy-2. Two Zr-plates partly coated with 200 Å porous Pt, with and respectively without D in the substrate, were oxidized in two stages at 400 °C. SIMS depth profiles in the Pt area show that an enhanced oxidation takes place mainly by inward oxygen transport. A minimum in the oxide thickness was found near the Pt area on both Zr plates. Two Ar-filled Zircaloy-2 tubes with ZrSn liner were exposed at 370 °C to 22 mbar water, filled in from one side. Our experimental results suggest that a proper choice of the SPP composition and size distribution can lead to reduced hydrogen uptake during oxidation of Zr-based materials in water.     

Mechanisms of oiliness additives

Ultrathin film interferometry has been used to measure the boundary film-forming behaviour of long chain, carboxylic acid oiliness additives. It has been shown that in dry conditions, these acids form very thin films of around 2–3 nm thickness. However when water is present, some acids form significantly thicker films, around 10 nm in thickness. The behaviour of these films is very similar to that previously seen with metal carboxylate additive films, including thick film collapse at high rolling speeds followed by film reformation at slow speeds. It is suggested thick films formed by long chain carboxylic acid additives result from reaction of the acids at the rolling solid surfaces in the presence of water to form deposits of insoluble iron carboxylate.     

Influence of the bias voltage on the formation of beryllium films by a thermionic vacuum arc method

Beryllium is intended to be used as suggested material for the first wall in the thermonuclear power plants. Some tiles of the first wall will be of inconel coated by a beryllium layer that must be adherent to the substrate and have a compact structure in order to resist as much as possible the dramatic interaction with the high energetic plasma particles, ions, electrons and neutrons. Applying bias voltages (−200 to + 700 V) on the substrates, the morphology of the prepared Be layers using the original thermionic vacuum arc method developed at NILPRP was controlled in order to obtain smooth surfaces, free of holes and lamellar structures. The prepared films were studied and characterized by scanning electron microscopy (SEM), atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS) and Auger spectroscopy (AES). The films prepared using negative bias voltages were found to be more compact and smooth with an average roughness (R_ms) of 7 nm.     

Magnetic susceptibility of Fulde-Ferrell superconductors

We investigate the magnetic susceptibility of a BCS superconductor with partially depaired states (Fulde state) as a possible explanation of deviations from the Chandrasekar-Clogston limit.     

A gas phase analysis technique applied to in-situ studies of gas–solid interactions

An ultrahigh vacuum technique using mass spectrometry for in-situ investigations of gas–solid interactions is described in this paper. Examples of chemical reactions (oxidation, hydration) between solids and gas mixtures, dissociation of gases on solid surfaces, outgassing of solid materials and permeation of gases through membranes are discussed where the experimental arrangement is explained in detail. This Gas Phase Analysis (GPA) technique can be used at temperatures from room temperature to 1200 °C and at pressures up to 1 atm. Aspects related to sample preparation, isotopic gas mixture selection, data acquisition, calibration and interpretation of the experimental data are also addressed.     

Parameter estimation in a thermoelastic composite problem via adjoint formulation and model reduction

Advances in nondestructive material characterization are providing a wealth of information that could be exploited to gain insight into general aspects of material performance and, in particular, discover relationships between microstructure and thermo‐mechanical properties in polycrystalline and other complex composite materials. In order to facilitate the integration of such measurements into existing models, as well as inform new physics‐based predictions, we developed a C++/MPI computational framework for sensitivity analysis and parameter estimation. The framework utilizes a micro‐mechanical modeling based on fast Fourier transforms, direct and adjoint formulations, and Markov chain Monte Carlo sampling techniques. We illustrate the characteristics of this framework and demonstrate its utility by computing the residual stresses arising from thermal expansion of an elastic composite and using data from simulated experiments. We show that the availability of nondestructive 3‐D measurements is crucial to reduce the uncertainty in predictions, emphasizing the importance of an integrated experimental/modeling/data analysis approach for improved material characterization and design. Copyright © 2017 John Wiley & Sons, Ltd.