Laboratoire d’analyse et d’architecture des systèmes
G.LAHINER, A.NICOLLET, JA.ZAPATA CORREA, L.MARIN MERCADO, N.RICHARD, M.DJAFARI ROUHANI, C.ROSSI, A.ESTEVE
Revue Scientifique : Journal of Applied Physics, Vol.122, N°15, 155105p., Octobre 2017 , N° 17390
Thermite multilayered films have the potential to be used as local high intensity heat sources for a variety of applications. Improving the ability of researchers to more rapidly develop Micro Electro Mechanical Systems devices based on thermite multilayer films requires predictive modeling in which an understanding of the relationship between the properties (ignition and flame propagation), the multilayer structure and composition (bilayer thicknesses, ratio of reactants, and nature of interfaces), and aspects related to integration (substrate conductivity and ignition apparatus) is achieved. Assembling all these aspects, this work proposes an original 2D diffusion-reaction modeling framework to predict the ignition threshold and reaction dynamics of Al/CuO multilayered thin films. This model takes into consideration that CuO first decomposes into Cu2O, and then, released oxygen diffuses across the Cu2O and Al2O3 layers before reacting with pure Al to form Al2O3. This model is experimentally validated from ignition and flame velocity data acquired on Al/CuO multilayers deposited on a Kapton layer. This paper discusses, for the first time, the importance of determining the ceiling temperature above which the multilayers disintegrate, possibly before their complete combustion, thus severely impacting the reaction front velocity and energy release. This work provides a set of heating surface areas to obtain the best ignition conditions, i.e., with minimal ignition power, as a function of the substrate type.
L.MARIN MERCADO, Y.GAO, M.VALLET, I.ABDALLAH, B.WAROT-FONROSE, C.TENAILLEAU, A.LUCERO, J.KIM, A.ESTEVE, Y.J.CHABAL, C.ROSSI
NEO, CEMES/CNRS, CIRIMAT, University of Texas
Revue Scientifique : Langmuir, 8p., Septembre 2017, DOI: 10.1021/acs.langmuir.7b02964 , N° 17369
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 (ZnAl2O4) and zinc oxide interfacial layers, which act as an effective barrier layer against oxygen diffusion at low temperature.
T.CALAIS, D.BOURRIER, A.BANCAUD, Y.J.CHABAL, A.ESTEVE, C.ROSSI
NEO, TEAM, MILE, University of Texas
Revue Scientifique : Langmuir, Septembre 2017, DOI 10.1021/acs.langmuir.7b02159 , N° 17376
DNA-directed assembly of nano-objects as a means to manufacture advanced nanomaterial architectures has been the subject of many studies. However, most applications have dealt with noble metals as there are fundamental difficulties to work with other materials. In this work, we propose a generic and systematic approach for functionalizing and characterizing oxide surfaces with single-stranded DNA oligonucleotides. This protocol is applied to aluminum and copper oxide nanoparticles due to their great interest for the fabrication of highly energetic heterogeneous nanocomposites. The surface densities of streptavidin and biotinylated DNA oligonucleotides are precisely quantified combining atomic absorption spectroscopy with conventional dynamic light scattering and fluorimetry, and maximized to provide a basis for understanding the grafting mechanism. First, the streptavidin coverage is consistently below 20% of the total surface for both nanoparticles. Second, direct and unspecific grafting of DNA single strands onto Al and CuO nanoparticles largely dominates the overall functionalization process:
A.NICOLLET, S.CHARLOT, V.BAIJOT, A.ESTEVE, C.ROSSI
Rapport LAAS N°17156, Août 2017, 1p.
Y.GAO, L.MARIN MERCADO, E.C.MATTSON, J.CURE, C.E.NANAYAKKARA, J.F.VEYAN, A.LUCERO, J.KIM, C.ROSSI, A.ESTEVE, Y.J.CHABAL
University of Texas, NEO
Revue Scientifique : Journal of Physical Chemistry C, Vol.121, N°23, pp.12780-12788, Juin 2017, DOI: 10.1021/acs.jpcc.7b02661 , N° 17098
Deposition of Al on ZnO is used for a number of electronic and catalytic devices as well as for nanoenergetic materials. The interface structure and chemical composition often control the performance of devices. In this study, in situ infrared spectroscopy, X-ray photoemission spectroscopy, and low energy ion scattering are combined to investigate the initial stage of interface formation between Al and ZnO. We find that (a) the interface is highly inhomogeneous with discontinuous Al patches, leaving ∼10% of the ZnO surface uncovered even after deposition of an equivalent of 11 nm-thick Al film; (b) upon Al deposition, Al reduces ZnO by forming Al2O3 and releasing Zn to the surface, and this process continues as more Al is deposited; (c) the reduced surface Zn atoms readily desorb at 150 °C; and (d) at higher temperature (>600 °C) all Al is oxidized as a result of mass transport. Deposition of a thin Al2O3 layer on ZnO prior to Al deposition effectively prevents Al penetration and Zn release, requiring higher temperatures to oxidize Al.
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
Rapport LAAS N°17137, DOI: 10.1021/acs.chemmater.7b01816, Juin 2017, 11p.
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.
V.BAIJOT, M.DJAFARI ROUHANI, C.ROSSI, A.ESTEVE
Revue Scientifique : Combustion and Flame, Vol.180, pp.10-19, Juin 2017 , N° 16410
This paper presents a hierarchical multiscale approach based on a micro-kinetic model enabling to predict temperature, pressure and species generated during the thermite reaction of Al nanoparticles mixed with CuO nanoparticles. Overall, our phenomenological model integrates and combines series of complex atomistic mechanisms, e.g. diffusion and phase transformation, gas phase reactions and interphase exchange mechanisms, in particular molecular condensation, evaporation and decomposition. Thermodynamics considerations as well as Density Functional Theory (DFT) calculations are used to implement rate equations expressing the complex reactions at solid/liquid/gas interphases. We demonstrate that the model can predict the pressure–time dependence, the different phases and compositions with good accuracy at significantly low computational cost. The influence of Al and CuO particle size, compaction or density, alumina shell thickness and stoichiometry on the pressure and temperature versus time is theoretically predicted with fairly good agreement with available experimental data. A maximum pressure of 47 MPa and adiabatic temperature of 3500 K are obtained at high compaction, i.e. 50% of the TMD (Theoretical Maximum Density) for stoichiometric mixture, where AlO is shown to be the prevailing gaseous species. At low compaction, we highlight the role of ambient oxygen condition for which the model gives a maximal pressure of 4.2 MPa for Al rich mixtures (stoichiometric ratio of 1.2).
T.CALAIS, V.BAIJOT, MC.BLATCHE, M.DJAFARI ROUHANI, Y.J.CHABAL, A.ESTEVE, C.ROSSI
NEO, I2C, University of Texas
Manifestation avec acte : E-MRS Spring Meeting 2017 du 22 mai au 26 mai 2017, Strasbourg (France), Mai 2017, 1p. , N° 17116
V.BAIJOT, M.DJAFARI ROUHANI, C.ROSSI, A.ESTEVE
Affiche/Poster : E-MRS Spring Meeting 2017 du 22 mai au 26 mai 2017, Strasbourg (France), Mai 2017, 1p. , N° 17087
L.MARIN MERCADO, A.ESTEVE, Y.GAO, Y.J.CHABAL, C.ROSSI
NEO, University of Texas
Manifestation avec acte : E-MRS Spring Meeting 2017 du 22 mai au 26 mai 2017, Strasbourg (France), Mai 2017, 1p. , N° 17086