0000000001192745
AUTHOR
Alexandre Zimmer
Morphological and chemical dynamics upon electrochemical cyclic sodiation of electrochromic tungsten oxide coatings extracted by in situ ellipsometry.
The sodiation–desodiation process of sputtered amorphous electrochromic tungsten oxide coatings in an aqueous-based medium was simultaneously monitored over 99 cycles by cyclic voltammetry and in situ spectroscopic ellipsometry. This allowed extracting the evolution of optical and geometrical parameters upon cycling. The resulting electrochemical coloring-bleaching process was dynamically fitted in the 1.8–2.8 eV optical range with a four-phase model including a constrained spline parametrization of the dielectric function. This allows real time access to thickness, surface roughness, and dielectric function of N a x W O 3 . The temporal evolution of the latter in the fully colored state wa…
Towards enhanced durability of electrochromic WO3 interfaced with liquid or ceramic sodium-based electrolytes
Abstract The reversible intercalation of sodium ion into tungsten oxide WO3 appears as an interesting alternative to hydrogen or lithium ion reduction in order to get the characteristic transition from clear transparent to bluish coloration in electrochromic devices, but it has been comparatively less considered. In order to address further viable all-ceramic devices based on sodium ion intercalation and overcome the issue of WO3 degradation in aqueous media, three configurations of WO3 thin film-based electrochromic half-cells were tested, namely in (i) aqueous acidified Na2SO4 electrolyte, (ii) room temperature ionic liquid BEPipTFSI electrolyte and (iii) aqueous acidified Na2SO4 electrol…
Electrodéposition et caractérisations optiques de nanofils de Tellure monocristallins
International audience
A lap joint simulant laboratory test method of aluminium alloys
A lap joint simulant cavity (LJSC) with a gap thickness of 200 μm has been developed to test corrosion of assembled coated aluminium alloys. The LJSC was instrumented with electrodes allowing simultaneous pH and potential measurements in 0.5 M NaCl solution. Assuming the outer part of the LJSC is electrochemically inactive (painted sheet) it was confirmed that in free corroding conditions the pH inside the LJSC tends more towards alkalinisation. On the opposite, if the outer part of the LJSC is electrochemically active (unpainted sheet) the pH inside the LJSC tends towards an acidic value.
Real-Time ellipsometric spectra without systematics errors
International audience; In real-time measurement, it is difficult to reduce systematic errors on spectra of ellipsometric angles Ψ and Δ by the mean of two measurementsat two analyzer positions with the incidence plane +45° and -45° [1-2]. Generally, the analyzer is mounted on a motorized rotation stage. Therotation of the optical component from -45° to +45° requires few seconds, and this is incompatible with dynamic measurements.
Simulation of pH-controlled dissolution of aluminium based on a modified Scanning Electrochemical Microscope experiment to mimic localized trenching on aluminium alloys
Abstract Some constituent intermetallic (IMPs) particles at the surface of aluminium alloys are considered as preferential sites for the initiation of structural corrosion resulting in localized trenching around the particles and the surrounding Al matrix. In this work, a modified scanning electrochemical microscope (SECM) experiment was used to induce such phenomena via a local alcalinisation on 200 nm thick aluminium coatings promoting their local dissolution in an aerated 0.1 M NaCl electrolyte. The local alcalinisation was induced by the oxygen reduction reaction on the tip of a SECM which mimics the surface of an isolated IMP. From a phenomenological point of view, reproducible cylindr…
Enseignement et recherche sont inséparables
Les politiques publiques françaises concentrent les moyens de recherche sur quelques “sites”, aux dépens de régions entières, creusant les inégalités entre universités dites “d’élite” ou “de masse”. Mais de nombreux travaux empiriques démontrent l’inefficacité d’une telle concentration des moyens.
Microstructural corrosion of aluminium alloys: a predictive finite element model based on corrosion-mimicking experiments
The purpose of this study is to implement the basis of a finite element model (FEM) based on the resolution of the Nernst–Planck equation in order to progress in the predictive simulation of microstructural corrosion on aluminium alloys. Certain constituent intermetallic particles at the surface of aluminium alloys are considered as preferential sites for the initiation of structural corrosion resulting in localised trenching around the particles and the surrounding Al matrix. In this work, a modified scanning electrochemical microscope (SECM) experiment was used to induce such phenomena via a local alkalinization on 200 nm thick aluminium coatings, promoting their local dissolution in an a…
La « politique de site » et le lien enseignement-recherche
Nous présentons ici des travaux empiriques qui invitent à la critique vis-à-vis de la tentation, présente en particulier au CNRS, de concentration des forces dans un plus petit nombre d'unités et de sites, et à la tendance de privilégier un profil unique de chercheur.se.s et de marginaliser certain.es enseignant.e.s-chercheur.s.es dans les laboratoires. Des travaux empiriques ont notamment montré que la concentration des moyens humains et financiers dans de gros centres est contre-productive et a déjà affiché ses limites et ses dangers. Au contraire, une plus grande homogénéité dans la distribution des fonds y est suggérée, pour conduire à une recherche plus fertile. En France, la transform…
Design of a real-time spectroscopic rotating compensator ellipsometer without systematic errors
6th International Conference on Spectroscopic Ellipsometry (ICSE), Kyoto, JAPAN, MAY 26-31, 2013; International audience; We describe a spectroscopic ellipsometer in the visible domain (400-800 nm) based on a rotating compensator technology using two detectors. The classical analyzer is replaced by a fixed Rochon birefringent beamsplitter which splits the incidence light wave into two perpendicularly polarized waves, one oriented at +45 degrees and the other one at-45 degrees according to the plane of incidence. Both emergent optical signals are analyzed by two identical CCD detectors which are synchronized by an optical encoder fixed on the shaft of the step-by-step motor of the compensato…
Interfaces électrochimiques et couches minces sondées par ellipsométrie
Spectroscopic ellipsometry (SE) is a non-invasive, non-destructive, and contactless optical technique which is based on the change in the polarization state of light as it is typically reflected from a thin film sample. Often seen primarily as ex situ or of particularly helpful interest to control in situ vacuum growth processes, SE can also be promoted as an analytical tool to diagnose electrolyte-electrode interface during wet processes. I will mainly highlight in this document my researches contributions in this field: (i) the very early growth stages of bismuth telluride electrodeposition, (ii) the physico-chemical properties of oxides grown in the early regime of plasma electrolytic ox…
Coloration mechanism of electrochromic Na x WO3 thin films
International audience; The coloration mechanism of tungsten trioxide (WO3) upon insertion of alkali ions is still under debate after several decades of research. This Letter provides new insights into the reversible insertion and coloration mechanisms of Na+ ions in WO3 thin films sputter-deposited on ITO/glass substrates. A unique model based on a constrained spline approach was developed and applied to draw out ε1+iε2 from spectroscopic ellipsometry data from 0.6 to 4.8 eV whatever the state of the electrochromic active layer, i.e. as-deposited, colored or bleached. It is shown that electrochemically intercalated sodium-tungsten trioxide, NaxWO3 (x=0.1, 0.2, 0.35), exhibits an absorption…
Visualization 4
Best-fitted evolution of the imaginary part of the pseudo-dielectric function (in red) for a representative sputtered amorphous WO3 coating during the 30th cycle of sodiation-desodiation. The video is accelerated 3.5 times. Total cycle duration: ca. 88 s. The initial bleached state is superimposed in black
Visualization 10
Best-fitted evolution of the imaginary part of the pseudo-dielectric function (in red) for a representative sputtered amorphous WO3 coating during the 90th cycle of sodiation-desodiation. The video is accelerated 3.5 times. Total cycle duration: ca. 88 s. The initial bleached state is superimposed in black
Visualization 8
Best-fitted evolution of the imaginary part of the pseudo-dielectric function (in red) for a representative sputtered amorphous WO3 coating during the 70th cycle of sodiation-desodiation. The video is accelerated 3.5 times. Total cycle duration: ca. 88 s. The initial bleached state is superimposed in black
Data_File_2.csv
Tabulated real (n) and imaginary (k) parts of the complex refraction index of Na0.2WO3 vs energy (eV) and wavelength (nm)
Visualization 7
Best-fitted evolution of the imaginary part of the pseudo-dielectric function (in red) for a representative sputtered amorphous WO3 coating during the 60th cycle of sodiation-desodiation. The video is accelerated 3.5 times. Total cycle duration: ca. 88 s. The initial bleached state is superimposed in black
Visualization 9
Best-fitted evolution of the imaginary part of the pseudo-dielectric function (in red) for a representative sputtered amorphous WO3 coating during the 80th cycle of sodiation-desodiation. The video is accelerated 3.5 times. Total cycle duration: ca. 88 s. The initial bleached state is superimposed in black
Visualization 9
Best-fitted evolution of the imaginary part of the pseudo-dielectric function (in red) for a representative sputtered amorphous WO3 coating during the 80th cycle of sodiation-desodiation. The video is accelerated 3.5 times. Total cycle duration: ca. 88 s. The initial bleached state is superimposed in black
Visualization 1
Best-fitted evolution of the imaginary part of the pseudo-dielectric function for a representative sputtered amorphous WO3 coating during the 5th cycle of sodiation-desodiation. The video is accelerated 3.5 times. Total cycle duration: ca. 88 s.
Visualization 3
Best-fitted evolution of the imaginary part of the pseudo-dielectric function (in red) for a representative sputtered amorphous WO3 coating during the 20th cycle of sodiation-desodiation. The video is accelerated 3.5 times. Total cycle duration: ca. 88 s. The initial bleached state is superimposed in black
Visualization 11
Best-fitted evolution of the imaginary part of the pseudo-dielectric function (in red) for a representative sputtered amorphous WO3 coating during the 99th cycle of sodiation-desodiation. The video is accelerated 3.5 times. Total cycle duration: ca. 88 s. The initial bleached state is superimposed in black
Data_File_2.csv
Tabulated real (n) and imaginary (k) parts of the complex refraction index of Na0.2WO3 vs energy (eV) and wavelength (nm)
Visualization 1
Best-fitted evolution of the imaginary part of the pseudo-dielectric function for a representative sputtered amorphous WO3 coating during the 5th cycle of sodiation-desodiation. The video is accelerated 3.5 times. Total cycle duration: ca. 88 s.
Visualization 8
Best-fitted evolution of the imaginary part of the pseudo-dielectric function (in red) for a representative sputtered amorphous WO3 coating during the 70th cycle of sodiation-desodiation. The video is accelerated 3.5 times. Total cycle duration: ca. 88 s. The initial bleached state is superimposed in black
Visualization 7
Best-fitted evolution of the imaginary part of the pseudo-dielectric function (in red) for a representative sputtered amorphous WO3 coating during the 60th cycle of sodiation-desodiation. The video is accelerated 3.5 times. Total cycle duration: ca. 88 s. The initial bleached state is superimposed in black
Data_File_1.csv
Tabulated real (n) and imaginary (k) parts of the complex refraction index of Na0.1WO3 vs energy (eV) and wavelength (nm)
Visualization 2
Best-fitted evolution of the imaginary part of the pseudo-dielectric function (in red) for a representative sputtered amorphous WO3 coating during the 10th cycle of sodiation-desodiation. The video is accelerated 3.5 times. Total cycle duration: ca. 88 s. The initial bleached state is superimposed in black
Data_File_3.csv
Tabulated real (n) and imaginary (k) parts of the complex refraction index of Na0.35WO3 vs energy (eV) and wavelength (nm)
Visualization 6
Best-fitted evolution of the imaginary part of the pseudo-dielectric function (in red) for a representative sputtered amorphous WO3 coating during the 50th cycle of sodiation-desodiation. The video is accelerated 3.5 times. Total cycle duration: ca. 88 s. The initial bleached state is superimposed in black
Visualization 5
Best-fitted evolution of the imaginary part of the pseudo-dielectric function (in red) for a representative sputtered amorphous WO3 coating during the 40th cycle of sodiation-desodiation. The video is accelerated 3.5 times. Total cycle duration: ca. 88 s. The initial bleached state is superimposed in black
Data_File_3.csv
Tabulated real (n) and imaginary (k) parts of the complex refraction index of Na0.35WO3 vs energy (eV) and wavelength (nm)
Visualization 10
Best-fitted evolution of the imaginary part of the pseudo-dielectric function (in red) for a representative sputtered amorphous WO3 coating during the 90th cycle of sodiation-desodiation. The video is accelerated 3.5 times. Total cycle duration: ca. 88 s. The initial bleached state is superimposed in black
Visualization 5
Best-fitted evolution of the imaginary part of the pseudo-dielectric function (in red) for a representative sputtered amorphous WO3 coating during the 40th cycle of sodiation-desodiation. The video is accelerated 3.5 times. Total cycle duration: ca. 88 s. The initial bleached state is superimposed in black
Data_File_1.csv
Tabulated real (n) and imaginary (k) parts of the complex refraction index of Na0.1WO3 vs energy (eV) and wavelength (nm)
Visualization 6
Best-fitted evolution of the imaginary part of the pseudo-dielectric function (in red) for a representative sputtered amorphous WO3 coating during the 50th cycle of sodiation-desodiation. The video is accelerated 3.5 times. Total cycle duration: ca. 88 s. The initial bleached state is superimposed in black
Visualization 3
Best-fitted evolution of the imaginary part of the pseudo-dielectric function (in red) for a representative sputtered amorphous WO3 coating during the 20th cycle of sodiation-desodiation. The video is accelerated 3.5 times. Total cycle duration: ca. 88 s. The initial bleached state is superimposed in black
Visualization 11
Best-fitted evolution of the imaginary part of the pseudo-dielectric function (in red) for a representative sputtered amorphous WO3 coating during the 99th cycle of sodiation-desodiation. The video is accelerated 3.5 times. Total cycle duration: ca. 88 s. The initial bleached state is superimposed in black
Visualization 2
Best-fitted evolution of the imaginary part of the pseudo-dielectric function (in red) for a representative sputtered amorphous WO3 coating during the 10th cycle of sodiation-desodiation. The video is accelerated 3.5 times. Total cycle duration: ca. 88 s. The initial bleached state is superimposed in black
Visualization 4
Best-fitted evolution of the imaginary part of the pseudo-dielectric function (in red) for a representative sputtered amorphous WO3 coating during the 30th cycle of sodiation-desodiation. The video is accelerated 3.5 times. Total cycle duration: ca. 88 s. The initial bleached state is superimposed in black