Influence of temperature on oxidation mechanisms of fiber-textured AlTiTaN coatings

The oxidation kinetics of AlTiTaN hard coatings deposited at 265 °C by DC magnetron sputtering were investigated between 700 and 950 °C for various durations. By combining dynamic secondary ion mass spectrometry (D-SIMS), X-ray diffraction (XRD), and transmission electron microscopy (TEM) investigations of the different oxidized coatings, we were able to highlight the oxidation mechanisms involved. The TEM cross-section observations combined with XRD analysis show that a single amorphous oxide layer comprising Ti, Al, and Ta formed at 700 °C. Above 750 °C, the oxide scale transforms into a bilayer oxide comprising an Al-rich upper oxide layer and a Ti/Ta-rich oxide layer at the interface with the coated nitride layer. From the D-SIMS analysis, it could be proposed that the oxidation mechanism was governed primarily by inward diffusion of O for temperatures of ≥700 °C, while at ≤750 °C, it is controlled by outward diffusion of Al and inward diffusion of O. Via a combination of structural and chemical analysis, it is possible to propose that crystallization of rutile lattice favors the outward diffusion of Al within the AlTiTa mixed oxide layer with an increase in the temperature of oxidation. The difference in the mechanisms of oxidation at 700 and 900 °C also influences the oxidation kinetics with respect to oxidation time. Formation of a protective alumina layer decreases the rate of oxidation at 900 °C for long durations of oxidation compared to 700 °C. Along with the oxidation behavior, the enhanced thermal stability of AlTiTaN compared to that of the TiAlN coating is illustrated. © 2014 American Chemical Society.SCOPUS: ar.jinfo:eu-repo/semantics/publishe

Measurement of resonance widths in 20Na using the 19Ne + p elastic scattering

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One-step energy scanning of wide low-lying 1- resonances in 13C+p and 13N+p scattering

Thick polyethylene targets have been bombarded with 8.2 MeV 13C and 13N beams accelerated by a cyclotron, i.e. having a relatively large energy spread of about 200 keV. Recoil protons have been detected in order to observe the Jπ=1- wide resonances at E*=8.06 and 5.17 MeV in the 14N and 14O compound nuclei, respectively. It is shown that accurate values of the energy, width and spin of the resonant states can be obtained under experimental conditions which, at first glance, may seem inappropriate. The method is well suited for resonance studies using radioactive beams. The measured width of the 14N resonance (Λ=33.7±1.0 keV) disagrees with a recent measurement (Λ=23 keV). The energy of the 14O resonance was determined to be Ec.m.=526±3 keV instead of 545±10 keV as quoted in the literature. A new paramater-free microscopic calculation was undertaken to solve an apparent discrepancy between the experimental proton width and a previous calculation. © 1992.info:eu-repo/semantics/publishe

Comparative experimental study of the mirror 13N+12C and 13C+12C elastic scatterings

The N13 + C12 and C13 + C12 elastic cross sections are measured at the center-of-mass energies of 7.8, 9.6, and 14.2 MeV, using radioactive N13 and stable C13 beams and position-sensitive solid-state detectors. These data are analyzed with the optical model assuming the same real central part of the nuclear potential for both systems as suggested by charge symmetry. The N13 + C12 angular distributions display a significant backward rise which arises from a parity dependence of the nucleus-nucleus interaction, as for the mirror C13 + C12 system. The corresponding parity terms in both potentials are similar when the different charges of the exchanged nucleons and their different binding energies are properly taken into account. A smaller imaginary part is obtained for N13 + C12 than for C13 + C12, which might be due to a smaller number of open two-body inelastic and direct reaction channels. © 1995 The American Physical Society.info:eu-repo/semantics/publishe

Aspects of the Louvain-la-Neuve results and projects

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Trapping in proton irradiated p+^+-n-n+^+ silicon sensors at fluences anticipated at the HL-LHC outer tracker

The degradation of signal in silicon sensors is studied under conditions expected at the CERN High-Luminosity LHC. 200 $\mu$m thick n-type silicon sensors are irradiated with protons of different energies to fluences of up to $3 \cdot 10^{15}$ neq/cm$^2$. Pulsed red laser light with a wavelength of 672 nm is used to generate electron-hole pairs in the sensors. The induced signals are used to determine the charge collection efficiencies separately for electrons and holes drifting through the sensor. The effective trapping rates are extracted by comparing the results to simulation. The electric field is simulated using Synopsys device simulation assuming two effective defects. The generation and drift of charge carriers are simulated in an independent simulation based on PixelAV. The effective trapping rates are determined from the measured charge collection efficiencies and the simulated and measured time-resolved current pulses are compared. The effective trapping rates determined for both electrons and holes are about 50% smaller than those obtained using standard extrapolations of studies at low fluences and suggests an improved tracker performance over initial expectation

Nuclear astrophysics studies with radioactive Beams in Louvain-La-Neuve

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Resonant scattering of a 19Ne beams on a H-target

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Measurements of the 19Ne(p,y) reaction rate using radioactive BEAMS

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Resonant scattering of isobaric 19Ne and 19F beams on an H target

Resonances in Na20 above the proton threshold have been studied by scattering radioactive Ne19 beams off thick polyethylene targets. The isobaric F19+p scattering was also examined. The analysis of the data under different theoretical approaches is discussed. The energy, total width, spin, and parity of two resonances in Na20 were assigned unambiguously. The results are compared to those obtained by indirect methods. © 1994 The American Physical Society.info:eu-repo/semantics/publishe