Laboratoire d’analyse et d’architecture des systèmes
Y.GAO, M.IACHELLA, E.C.MATTSON, A.LUCERO, J.KIM, M.DJAFARI ROUHANI, Y.J.CHABAL, C.ROSSI, A.ESTEVE
NEO, University of Texas
Revue Scientifique : Journal of Physical Chemistry C, 29p., Juillet 2018, DOI: 10.1021/acs.jpcc.8b04952 , N° 18193
Deposition of Al onto ZnO surfaces is important for metal/insulator contacts in microelectronics and photovoltaic devices, and also for nano-energetic materials; yet there have not been fundamental studies of these interfaces, in particular those involving the polar faces of ZnO. Density Functional calculations and Low Energy Ion Scattering (LEIS) studies are combined to unravel the chemistry of Al interaction on polar ZnO surfaces, revealing that Al atoms quasi spontaneously replace surface Zn atoms on both O-and Zn-terminated ZnO surfaces. In this process, aluminum atoms attract oxygen atoms, releasing zinc atoms through electrostatic repulsion within the growing alumina film. Kinetics and thermodynamics calculations indicate that zinc atoms accumulate on the surface rather than migrating into ZnO bulk at room temperature, due to high bulk diffusion barriers. Upon annealing to moderate temperatures, LEIS studies indicate that surface Zn atoms desorb at ~ 140-150 °C, which is consistent with the calculated 1.31 eV activation barrier.
Manifestation avec acte : GRC: Energetic Materials ( ) 2018 du 03 juin au 08 juin 2018, Newry (USA), Juin 2018, 2p. , N° 18157
P.CHAMPIGNEUX, C.RENAULT-SENTENAC, D.BOURRIER, C.ROSSI, M.L.DELIA, A.BERGEL
LGC, NEO, TEAM
Revue Scientifique : Bioelectrochemistry, Vol.121, pp.191-200, Juin 2018 , N° 18045
A.NICOLLET, L.SALVAGNAC, V.BAIJOT, A.ESTEVE, C.ROSSI
Revue Scientifique : Sensors and Actuators A: Physical, Vol.273, pp.249-255, Avril 2018 , N° 18080
Pyroswitches and circuit breakers play an important safety role in electrical systems. A miniature one-shot circuit breaker based on the violent reaction of a nanothermite is presented for safety application as protection against overcurrent, external perturbation and short circuit of a broad range of equipment and systems. This device consists of two circuits assembled together to define a cavity. An ignition chip is placed into this cavity and ignites, within less than 100 µs, a few milligrams of nanothermites powder. The resulting violent reaction interrupts a thick copper connection within 1 ms. After the presentation of the device design, fabrication and assembly, we demonstrate the good operation and reproducibility of the device (100 % of success rate) with a response time much lower than that of classical mechanical circuit breakers, which are slow. The response time can be tuned from 1.02 ms to 0.57 ms just by adjusting the mass of nanothermites from 5.59 to 13.24 mg, i.e., adjusting the volumetric solid loadings from 5.6 to 19 %. The nanothermite-based circuit breaker presented in this paper offers unprecedented advantages: it is built using only safe substances and is based on a low-2 cost mass fabrication process that is compatible with electronics. The proposed concept is generic and can be applied to a large number of applications (electrical storage, aerospace manufacturing, human safety, demolition parachute opening, road vehicles, battery powered machines…).
I.ABDALLAH, JA.ZAPATA CORREA, G.LAHINER, B.WAROT-FONROSE, J.CURE, Y.J.CHABAL, A.ESTEVE, C.ROSSI
CEMES/CNRS, NEO, University of Texas
Revue Scientifique : ACS Applied Energy Materials, Avril 2018, doi 10.1021/acsaem.8b00296 , N° 18085
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 towards the aluminum layers through interfacial layers- moves throughout the multilayer at subsonic rates (m/s to tens of m/s). 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 (STEM), providing simultaneous sub-nanometrer 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 15 ± 5 nm thick mixture of AlOx and CuxAlyOz, 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 (Al2O3). 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 - 350 °C, we observed a brutal shrinkage of 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 mechanical fragility of the top interface after the CuO transformation. Altogether, these results permit to establish a multi-step reaction scenario in Al/CuO sputter-deposited films supporting to an unprecedented level a mechanistic assignation of Differential Scanning Calorimetry (DSC) 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.
Rapport LAAS N°18028, Mars 2018
Sputter-deposited Al/CuO multilayers represent the state-of-the-art of energetic nanomaterials. As such, they offer an opportunity for tunable ignition and actuation because their theoretical energy densities are significantly higher than most conventional secondary explosives while being less sensitive to undesired initiation. Both the sensitivity and combustion properties (temperature, rate and products released) can be manipulated via the layering, reactant spacing and stoichiometry of the multilayer and, to a lesser extent, via interface engineering. In this article, we first describe the technology of deposition of Al/CuO multilayers focusing on direct current sputter deposition followed by a comprehensive review of the materials structural characteristics. Next, experimental and theoretical works performed on these reactive multilayered materials to date is presented in terms of methods used, the results acquired on ignition and combustion properties, and conclusions drawn. Emphasis is placed on several studies elucidating the fundamental processes that underlie propagating combustion reactions. We examine the influence of the « ceiling » temperature that traduces the multilayer disintegration when reaching high temperatures (e.g., vaporization temperatures). This paper provides a good support for engineers to safely propose Al/CuO multilayers structure to regulate the energy release rates and ignition threshold in order to manufacture high performance and tunable initiator devices.
J.CURE, H.ASSI, K.COCQ, L.MARIN MERCADO, K.FAJERWERG, P.FAU, E.BECHE, Y.J.CHABAL, A.ESTEVE, C.ROSSI
NEO, LCC, PROMES, University of Texas
Revue Scientifique : Langmuir, Vol.34, N°5, pp.1932-1940, Février 2018, doi 10.1021/acs.langmuir.7b04105 , N° 18020
The integration of high-purity nano-objects on substrates remains a great challenge for addressing scaling-up issues in nanotechnology. For instance, grafting gold nanoparticles (NPs) on zinc oxide films, a major step process for catalysis or photovoltaic applications, still remains difficult to master. We report a modified photodeposition (P-D) approach that achieves tight control of the NPs size (7.5 ± 3 nm), shape (spherical), purity, and high areal density (3500 ± 10 NPs/μm 2) on ZnO films. This deposition method is also compatible with large ZnO surface areas. Combining electronic microscopy and X-ray photoelectron spectroscopy measurements, we demonstrate that growth occurs primarily in confined spaces (between the grains of the ZnO film), resulting in gold NPs embedded within the ZnO surface grains thus establishing a unique NPs/surface arrangement. This modified P-D process offers a powerful method to control nanoparticle morphology and areal density and to achieve strong Au interaction with the metal oxide substrate. This work also highlights the key role of ZnO surface morphology to control the NPs density and their size distribution. Furthermore, we experimentally demonstrate an increase of the ZnO photocatalytic activity due to high densities of Au NPs, opening applications for the decontamination of water or the photoreduction of water for hydrogen production.
V.BAIJOT, M.DJAFARI ROUHANI, C.ROSSI, A.ESTEVE
Rapport LAAS N°17466, Décembre 2017, 4p.
V.BAIJOT, M.DJAFARI ROUHANI, C.ROSSI, A.ESTEVE
Rapport LAAS N°17467, Décembre 2017, 24p.
A.DANGERFIELD, C.E.NANAYAKKARA, A.MALLIKARJUNAN, X.LEI, R.M.PEARLSTEIN, A.DERECSKEI-KOVACS, J.CURE, A.ESTEVE, Y.J.CHABAL
University of Texas, Versum Materials Inc, NEO
Revue Scientifique : Chemistry of Materials, Vol.29, N°14, pp.6022-6029, Décembre 2017, DOI: 10.1021/acs.chemmater.7b01816 , N° 17137
Aminosilanes are attractive precursors for atomic layer deposition of silicon oxides and nitrides because they are halide-free and more reactive than chlorosilanes. However, the deposition of silicon nitride on oxide substrates still requires relatively high temperatures. We show here that for a process involving disec-butylaminosilane and hydrazine, the insertion of Al from trimethyl aluminum allows the deposition of silicon nitride films at relatively low temperatures (250 °C). First-principles calculations reveal that the presence of Al increases the binding of molecular hydrazine, thereby effectively enhancing the reactivity of hydrazine with the silicon precursor during the atomic layer deposition process, which leads to nitrogen incorporation into silicon. However, the range of this enhancement is limited to ∼1 nm, requiring additional trimethylaluminum exposures to continue the Si3N4 deposition.