Interfacial toughness of the nickel-nickel oxide system

International audienc

In situ ESEM investigations of the oxide growth on hot work tools steel: effect of the water vapour

5th International Conference on the Microscopy of Oxidation, UNIV LIMERICK, LIMERICK, IRELAND, AUG 26-29, 2002International audienceTempered martensitic steel modified AISI H11 is used in forging processes where tool failure can result from the combination of thermo-mechanical and chemical damage. A better knowledge of the oxidation mechanisms in this material could be useful for a better appreciation of its service behaviour and lifetime. the low chromium content of this Fe-Cr type steel allows the development of mainly Fe2-xCrxO3 oxides with corundum structure and leads to enhanced oxidation in the presence of water vapour. In situ FEG-ESEM images show the scale microstructural modifications during high temperature exposure, as well as the lateral growth of oxide particles. Together with GIXRD, SEM/EDS and SIMS analysis. FEG-ESEM also allows assessment of the H2O effect on oxidation behaviour during high temperature exposures (600 and 700degreesC). Water vapour induces either pores or crystallites size increase, favours faceted oxides particles with enhanced density at the highest partial pressure. At this microscopic scale. anisotropic growth of crystallites is observed, and size expansion rates are found to be linear and characteristic of each individual particle. Temperature acts principally on oxide film microstructure. Whatever the environment, homogeneous scale growth is observed at 600degreesC whereas the steel surface is heterogeneously covered by oxides at 700degreesC

Obese sedentary patients with dyspnoea on exertion who are at low risk for coronary artery disease by clinical criteria have a very low prevalence of coronary artery disease

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/106981/1/cob12053.pd

Magnetic anisotropy in hole-doped superconducting Ba 0.67K 0.33Fe 2As2 probed by polarized inelastic neutron scattering

We use polarized inelastic neutron scattering (INS) to study spin excitations of optimally hole-doped superconductor Ba$_{0.67}$K$_{0.33}$Fe$_2$As$_{2}$ ($T_c=38$ K). In the normal state, the imaginary part of the dynamic susceptibility, $\chi^{\prime\prime}(Q,\omega)$, shows magnetic anisotropy for energies below $\sim$7 meV with c-axis polarized spin excitations larger than that of the in-plane component. Upon entering into the superconducting state, previous unpolarized INS experiments have shown that spin gaps at $\sim$5 and 0.75 meV open at wave vectors $Q=(0.5,0.5,0)$ and $(0.5,0.5,1)$, respectively, with a broad neutron spin resonance at $E_r=15$ meV. Our neutron polarization analysis reveals that the large difference in spin gaps is purely due to different spin gaps in the c-axis and in-plane polarized spin excitations, resulting resonance with different energy widths for the c-axis and in-plane spin excitations. The observation of spin anisotropy in both opitmally electron and hole-doped BaFe$_2$As$_2$ is due to their proximity to the AF ordered BaFe$_2$As$_2$ where spin anisotropy exists below $T_N$.Comment: 5 pages, 4 figure

Strong short-range magnetic order in a frustrated FCC lattice and its possible role in the iron structural transformation

We investigate magnetic properties of a frustrated Heisenberg antiferromagnet with a face-centered cubic (FCC) lattice and exchange interactions between the nearest- and next-nearest neighbours, J1 and J2. In a collinear phase with the wave vector Q = (pi,pi,pi) the equations of the self-consistent spin-wave theory for the sublattice magnetization and the average short range order parameter are obtained and numerically solved. The dependence of the Neel temperature T_N on the ratio J2/J1 is obtained. It is shown, that at strong enough frustration there is a wide temperature region above T_N with strong short range magnetic order. Application of this result to description of structural phase transition between alpha and gamma-phase of Fe is considered

Distinguishing s±s^{\pm} and s++s^{++} electron pairing symmetries by neutron spin resonance in superconducting NaFe0.935_{0.935}Co0.045_{0.045}As

A determination of the superconducting (SC) electron pairing symmetry forms the basis for establishing a microscopic mechansim for superconductivity. For iron pnictide superconductors, the $s^\pm$-pairing symmetry theory predicts the presence of a sharp neutron spin resonance at an energy below the sum of hole and electron SC gap energies ($E\leq 2\Delta$) below $T_c$. On the other hand, the $s^{++}$-pairing symmetry expects a broad spin excitation enhancement at an energy above $2\Delta$ below $T_c$. Although the resonance has been observed in iron pnictide superconductors at an energy below $2\Delta$ consistent with the $s^\pm$-pairing symmetry, the mode has also be interpreted as arising from the $s^{++}$-pairing symmetry with $E\ge 2\Delta$ due to its broad energy width and the large uncertainty in determining the SC gaps. Here we use inelastic neutron scattering to reveal a sharp resonance at E=7 meV in SC NaFe$_{0.935}$Co$_{0.045}$As ($T_c = 18$ K). On warming towards $T_c$, the mode energy hardly softens while its energy width increases rapidly. By comparing with calculated spin-excitations spectra within the $s^{\pm}$ and $s^{++}$-pairing symmetries, we conclude that the ground-state resonance in NaFe$_{0.935}$Co$_{0.045}$As is only consistent with the $s^{\pm}$-pairing, and is inconsistent with the $s^{++}$-pairing symmetry.Comment: 9 pages, 8 figures. submitted to PR

Design and in vitro studies of a needle-type glucose sensor for subcutaneous monitoring

International audienceA new miniaturized glucose oxidase based needle-type glu¬ cose mlcrosensor has been developed for subcutaneous glu¬ cose monitoring. The sensor Is equivalent In shape and size to a 26-gauge needle (0.45-mm o.d.) and can be Implanted with ease without any Incision. The novel configuration greatly facilitates the deposition of enzyme and polymer films so that sensors with characteristics suitable for In vivo use (upper limit of linear range > 15 mM, response time 60%). The sensor response is largely Independent of ox¬ ygen tension In the normal physiological range. It also ex¬ hibits good selectivity against common interferences except for the exogenous drug acetaminophen