Sputter-deposited Al/CuO multilayers exhibit fast combustion reactions in which an exothermic chemical reaction wavecontrolled by the migration of oxygen atoms from the oxide matrix toward the aluminum layers through interfacial layersmoves throughout the multilayer at subsonic rates (meters per second to tens of meters per second). We directly observed the structural and chemical evolution of Al/CuO/Al multilayers upon heating to 700 °C using high-magnification transmission electron microscopy (TEM) and scanning TEM, providing simultaneous subnanometrer imaging resolution and detailed chemical analysis. Interestingly, as deposited, the trilayer is characterized by two distinct interfacial layers: 4.1 ± 0.2 nm thick amorphous alumina and a 15 ± 5 nm thick mixture of AlO x and Cu x Al y O z , at the bottom interface and top interface, respectively. Upon heating, we accurately characterized the evolving nature and structure of these interfaces, which are rapidly replaced by the reaction terminal oxide (Al 2 O 3 ). For the first time, we unraveled the release of gaseous O from the sparse columnar and defective CuO well below reaction onset (at ∼200 °C) which accumulates at interfaces and contributes to initiate the Al oxidation process at the vicinity of native interfaces. The oxidation process is demonstrated to be accompanied by a continuous densification and modification of the CuO layer. Between 300 and 350 °C, we observed a brutal shrinkage of the CuO layer (14% loss of its initial thickness) leading to the mechanical fracture in the top alumina growing layer. Consequently, this latter becomes highly permeable to oxygens leading to a brutal enhancement of the oxidation rate (×4). We also characterized stressed-induced interfacial delamination at 500 °C pointing clearly to the mechanical fragility of the top interface after the CuO transformation. Altogether, these results permit one to establish a multistep reaction scenario in Al/CuO sputter-deposited films supporting to an unprecedented level a mechanistic assignation of differential scanning calorimetry peaks. This study offers potential benefits for the development of aging models enabling the virtual prediction of the calorimetric response of exothermic Al/CuO thin-film reactions.

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Oxide-alloy interface of Ti6242S Ti-based alloy was investigated by STEM-EELS technique, after oxidation in both N 2-free and synthetic air atmospheres at 650°C for 1000 h. The chemical shift of Ti-L 2,3 edge and its specific fine structure along the oxide-alloy interface were used as fingerprint to distinguish the different compositions of titanium nitrides and oxynitrides. TiN, Ti 2 N and TiN x O y were identified in the sample oxidized in synthetic air at the oxide-alloy interface. Moreover, a decreasing in the oxidation state of Ti oxides was found along with Sn segregation at the oxide-alloy interface for the sample oxidized in N 2-free atmosphere.

Al/CuO energetic structure are attractive materials due to their high thermal output and propensity to produce gas. They are widely used to bond components or as next generation of MEMS igniters. In such systems, the reaction process is largely dominated by the outward migration of oxygen atoms from the CuO matrix toward the aluminum layers, and many recent studies have already demonstrated that the interfacial nanolayer between the two reactive layers plays a major role in the material properties. Here we demonstrate that the ALD deposition of a thin ZnO layer on the CuO prior to Al deposition (by sputtering) leads to a substantial increase in the efficiency of the overall reaction. The CuO/ZnO/Al foils generate 98% of their theoretical enthalpy within a single reaction at 900 °C, whereas conventional ZnO-free CuO/Al foils produce only 78% of their theoretical enthalpy, distributed over two distinct reaction steps at 550 °C and 850 °C. Combining high-resolution transmission electron microscopy, X-ray diffraction, and differential scanning calorimetry, we characterized the successive formation of a thin zinc aluminate (ZnAlO) and zinc oxide interfacial layers, which act as an effective barrier layer against oxygen diffusion at low temperature.

Ferromagnetic resonance has been used to investigate the effect of Mn/Si and Co/Mn atomic disorder on the magnetic properties and dynamic relaxation of Co 2 MnSi Heusler alloy. He + ion irradiation at 150 KeV is used to induce Co/Mn and Mn/Si swap in the initial structure of the material. While Mn/Si disorder is found to show similar magnetic behavior as compared to the L2 1 order, we observe a strong impact of Co/Mn swap on the static and dynamic properties of the alloy. These results are explained with regard to electronic band structure and damping coefficient first-principles calculations showing the modification of the minority-spin density of states at the Fermi energy and local magnetic orbital moment with Co/Mn swap.

We have investigated the atomic disorder induced by a 150 keV He + ion irradiation in a 40 nm thick Co 2 MnSi Heusler alloy. Disorder parameters on each atomic site are deduced from normal and anomalous X-ray diffraction measurements with Co and Cu Kα sources. While the film grows mainly in the L2 1 phase with inclusion of B2 grains, we observe an increase of both the Mn-Si and Co-Mn exchanges with the ion fluence. HAADF-STEM analysis demonstrates that the increase in Mn-Si disorder corresponds to a growing size of the B2 grains while the Co-Mn exchange is accounted for a D0 3 disorder type in the L2 1 matrix. These structural modifications are shown to decrease the

This study focuses on the corrosion behaviour of Ti-6Al-2Sn-4Zr-2Mo-Si alloy in presence of NaCl deposit in air at 560°C. The active oxidation mechanism at the origin of the corrosion phenomenon enhancement in presence of solid NaCl is thought to be connected to the formation of both external and internal thick oxidation areas. Thermodynamic calculations allowed showing the role played by the different alloying elements in the formation of the external oxide and detailed TEM characterisations brought new insights regarding the nature and origin of the internal oxidation area.

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