S. Bouhtiyya - Academia.edu (original) (raw)

Papers by S. Bouhtiyya

Thin Solid Films, 2006

Bilayered palladium (30 nm thick)–magnesium (350 nm thick) thin films were prepared using the pul... more Bilayered palladium (30 nm thick)–magnesium (350 nm thick) thin films were prepared using the pulsed laser deposition technique in the presence of various background gases (Ar, He and a mixture He+H2) under different partial pressures (47 and 27 Pa). According to the deposition atmosphere, the Pd/Mg interface shows either a sharp or an extended transition. The electrochemical hydriding properties and

International Journal of Hydrogen Energy, 2008

Pulsed laser deposition Microstructure Metal hydride electrode a b s t r a c t Pd thin films were... more Pulsed laser deposition Microstructure Metal hydride electrode a b s t r a c t Pd thin films were prepared by pulsed laser deposition (PLD) under different helium background gas pressures (50, 350 and 800 mTorr). The Pd films were characterized using X-ray diffraction (XRD), X-ray reflectivity (XRR), Rutherford, backscattering spectrometry (RBS), scanning electron microscopy (SEM), atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS). Their electrochemical hydriding behavior was studied in 1 M KOH solution. All the films are nanostructured (crystallite size between 7 and 15 nm), slightly preferentially orientated in the /1 1 1S direction and anisotropically deformed in the /1 0 0S direction. The films deposited at 350 and 800 mTorr are less deformed than those deposited at 50 mTorr. The helium pressure has a major effect on the film morphology. Pd films deposited at 50 mTorr are very smooth and dense, those deposited at 350 mTorr are still dense but with a rougher surface while at 800 mTorr, the films are very rough and porous (porosity of $30%). These differences in film morphology are related to the decrease of the kinetic energy (from 31 to 1.6 eV) of the Pd impinging species with increasing He pressure, as determined from time-of-flight emission spectroscopy.

International Journal of Hydrogen Energy, 2009

Magnesium Palladium Thin film Pulsed laser deposition Hydrogen electrosorption a b s t r a c t Th... more Magnesium Palladium Thin film Pulsed laser deposition Hydrogen electrosorption a b s t r a c t Three-layered Pd/Mg/Pd thin films were prepared by pulsed laser deposition in the presence of helium gas. For Pd layer deposition, the He pressure was fixed at 200 mTorr whereas different pressures of He were used for Mg layer deposition (50, 200 and 600 mTorr). The degree of crystallinity and of (001) texture in the Mg layer increase with increasing He pressure. In addition, the increase in He pressure upon Mg deposition greatly accentuates the roughness of the Mg layer, which induces an extension of the outer Pd/Mg interface region. In contrast, the inner Pd/Mg interface is sharp for all the Pd/Mg/Pd films. The electrochemical hydrogen sorption properties of the Pd/Mg/Pd films are improved by increasing the He pressure for Mg layer deposition. However, the maximum H-solubility in the Mg layer remains low (H/Mg w0.26) and is not significantly increased by the presence of the inner Pd layer, indicating that Mg hydride phase is confined in the outer Pd/Mg interface region.

Electrochimica Acta, 2014

ABSTRACT Thin films of VN with different thickness were prepared by D.C. reactive magnetron sputt... more ABSTRACT Thin films of VN with different thickness were prepared by D.C. reactive magnetron sputtering. Crystalline films with a preferential growth in the direction (111) were obtained. The electrochemical performances of the films with different thickness have been investigated. The mechanism of charge storage depends on the nature of the electrolyte. In the presence of KOH fast and reversible redox reactions take place while only double layer capacitance is observed when NEt4BF4 in acetonitrile is used as electrolyte. Thin films with a thickness of 25 nm show the highest specific capacitance (422 F.g−1) in 1 M KOH electrolyte. Films possess an active volume in which the charge is stored and a bulk volume for electron conduction. The active volume of the films is of the same order of magnitude regardless of the electrode thickness. Real devices with a symmetric configuration were prepared. The devices were tested in 1 M KOH electrolyte and PVA-KOH gel electrolyte. VN films with a thickness below 100 nm can reach the volumetric power of electrolytic capacitors (125 Wcm−3) with much higher volumetric energy density (0.01Whcm−3), thus emphasizing the usefulness of combining high capacitance together with high electronic conductivity.

Scripta Materialia, 2013

RuN films that crystallized in the ZnS-like structure with [1 1 1] preferred orientation have bee... more RuN films that crystallized in the ZnS-like structure with [1 1 1] preferred orientation have been deposited by reactive sputtering. Preliminary results are reported on the electrochemical properties of such films as electrode materials for supercapacitors and lithium-ion batteries. Cyclic voltammetric experiments indicate an attractive capacitance value of 37 F g À1 . Moreover, galvanostatic measurements indicate that RuN films reversibly react with lithium through a conversion reaction with Ru(0) nanoparticle formation. A high capacity value of $700 mAh g À1 at C/2 rate is achievable.

Review of Scientific Instruments, 2014

This article presents a device for the study of physisorbed elements on polished surfaces (diamet... more This article presents a device for the study of physisorbed elements on polished surfaces (diameter ⩽56 mm) of the kind used in mass metrology. The technique is based on mass spectrometry of molecules desorbed after heating under vacuum of the analyzed surface. We describe a first application of the device to study current and future mass standards in order to understand how their surface reactivity depends on storage conditions, cleaning processes, and polishing methods. Surface contamination analysis by thermal desorption mass spectrometry to examine the effect of cleaning on pure iridium is given as an example.

Electrochemistry Communications, 2013

ABSTRACT Vanadium nitride thin film has been coupled with electrodeposited nickel oxide in order ... more ABSTRACT Vanadium nitride thin film has been coupled with electrodeposited nickel oxide in order to design an electrochemical capacitor microdevice. VN has been used as negative electrode while NiO was used as the positive one in 1 M KOH electrolyte. VN exhibits a pseudo-capacitive behavior while NiO shows a faradaic behavior. This asymmetric microdevice has been operated between 0.5 and up to 1.8 V in aqueous based electrolyte (1 M KOH). Long term cycling ability (10,000 charge/discharge cycles) has been demonstrated with interesting energy (1.0 μW h cm− 2) and power (40 mW cm− 2) densities.

Wear, 2015

This paper shows how Angle-Resolved Scattering can reveal wear on engineered surfaces. The sample... more This paper shows how Angle-Resolved Scattering can reveal wear on engineered surfaces. The samples studied, three discs made of steel 100Cr6H used in gear wheels in the automotive industry, were assessed after they had undergone ball-on-disc tests. Scattering maps recorded for spatial frequencies from 0.1 mm À 1 to 2.7 mm À 1 show a contrast inversion around 0.36 mm À 1 revealing the wear trace. Besides measurements of rms roughness, where mean values are 20 nm and 24 nm depending on the locations considered, stationarity and isotropy, we demonstrate the ability of the technique to reveal localized wear on this type of surface in a rapid, robust and convenient way. We show that the tool trace is influenced by the load magnitude rather than by the number of oscillation cycles and highlight the key role played by surface roughness in how the sample responds to wear tests.