Benoit lefez - Academia.edu (original) (raw)

Papers by Benoit lefez

Thermal Spray 2005: Proceedings from the International Thermal Spray Conference

As already shown 3 years ago, the preoxidation of smooth (Ra < 0.05 µm) low carbon steel subst... more As already shown 3 years ago, the preoxidation of smooth (Ra < 0.05 µm) low carbon steel substrates in a furnace under a CO2 rich atmosphere at atmospheric pressure allows the formation of a wustite (Fe1-xO) layer which improves significantly the adhesion (> 55 MPa) of alumina coatings in spite of the rather low roughness (0.10 µm < Ra < 1.00 µm) of the oxidized surface. This contribution is devoted to a more precise study of the wustite layer and its interface with the alumina layer by X-ray diffraction (XRD), Mossbauer spectroscopy and scanning electron microscopy (SEM). Firstly the substrate was oxidized under different temperatures and durations in order to control the oxide layer thickness and structure. Secondly the substrate samples were preoxidized during 15 minutes at 1273 K under CO2 atmosphere and, afterwards, preheated by the plasma jet in air just before coating. In this case the analysis was focused both on the alumina splat formation and the interface betw...

Abhurite Sn 21 O 6 Cl 16 (OH) 14 is a tin oxy-hydroxychloride discovered in 1985 as a tin corrosi... more Abhurite Sn 21 O 6 Cl 16 (OH) 14 is a tin oxy-hydroxychloride discovered in 1985 as a tin corrosion product formed after long immersion in sea water, has been synthesised and studied using FTIRAS analysis. The vibrational spectra obtained in transmission and reflectance modes of analysis are presented and compared to the vibrational spectra determined by Kramers Kronig analysis. Transversal and longitudinal (TO and LO) optical modes have been identified.

Revue de Métallurgie, 1998

On montre comment la spectroscopie infrarouge peut etre utilisee en reflexion lors de l’etude de ... more On montre comment la spectroscopie infrarouge peut etre utilisee en reflexion lors de l’etude de produits d’oxydation. Elle pallie les faiblesses de la diffraction de rayons X lors de l’etude analytique de produits sous forme amorphe.Elle permet d’atteindre l’epaisseur des couches sans les detruire et sans preparation particuliere. L’organisation des produits d’oxydation peut etre obtenue par comparaison des spectres experimentaux avec des spectres calcules sur la base de structures de couches modelisees.Des exemples relatifs a l’oxydation thermique de differentes nuances telles que Z8C17, Z8CS17, Z8CAT17 et Ni-Cr80/20 sont traites au cours de cet article.

Revue de Métallurgie, 1994

Thin Solid Films, 1995

Cupric oxide in thin film form is studied by infrared reflectance spectroscopy and is characteris... more Cupric oxide in thin film form is studied by infrared reflectance spectroscopy and is characterised by absorption bands at 480 and 540 cm−1 (associated with transverse optical vibration modes) and at 600 cm−1 (associated with longitudinal optical vibration mode).The modelisation of reflection spectra obtained when CuO oxide is present under different morphologies (inclusion, aggregate or outer layer of a multilayer system) predicts a shift of the band at 480 cm−1 to 520 cm−1. The experimental spectra obtained by copper oxidation confirm this trend and the influence of oxide film structure on the details of the spectra.Thus, infrared reflection spectroscopy is an appropriate method for the study and the understanding of complex structures such those developed during the oxidation of copper-nickel alloys.

Nanotechnology, 2011

A new synthesis protocol is described to obtain a CdTe decorated magnetite bifunctional nanosyste... more A new synthesis protocol is described to obtain a CdTe decorated magnetite bifunctional nanosystem via dodecylamine (DDA) as cross linker. High resolution transmission electron microscopy (HRTEM), energy-dispersive x-ray spectroscopy (EDAX), vibrating sample magnetometry (VSM), Fourier transform infrared spectroscopy (FTIR), diffuse reflectance spectroscopy (DRS) and fluorescence microscopy are used to characterize the constitution, size, composition and physical properties of these superparamagnetic-fluorescent nanoparticles. These CdTe decorated magnetite nanoparticles were then functionalized with anti-epidermal growth factor receptor (EGFR) antibody to specifically target cells expressing this receptor. The EGFR is a transmembrane glycoprotein and is expressed on tumor cells from different tissue origins including human leukemic cell line Molt-4 cells. The magnetite-CdTe composite nanosystem is shown to perform excellently for specific selection, magnetic separation and fluorescent detection of EGFR positive Molt-4 cells from a mixed population. Flow cytometry and confocal laser scanning microscopy results show that this composite nanosystem has great potential in antibody functionalized magnetic separation and imaging of cells using cell surface receptor antibody.

Materials Research Bulletin, 1996

The longitudinal (LO) frequencies as well as the transversal (TO) frequencies are determined in a... more The longitudinal (LO) frequencies as well as the transversal (TO) frequencies are determined in a series of cobaltite spinels: COCOS, ZnCozO,, MnCozO+ FeCozOd, CuCo204, and NiCozO4. The data were obtained from the infrared reflectance spectra of thin layers on cobalt substrate.

Journal of Materials Chemistry, 2012

ABSTRACT A high surface area carbon composite with Fe3O4 nanoparticles is synthesized by pyrolysi... more ABSTRACT A high surface area carbon composite with Fe3O4 nanoparticles is synthesized by pyrolysis of an iron containing Metal Organic Framework (MOF). The composite can be prepared by annealing the MOF at different temperatures (500 °C and 600 °C), each case exhibiting unique properties in terms of the hydrophobic behaviour and surface area, resulting in specific applicability domains. We highlight the exceptional behaviour of this material as a magnetically separable and recyclable superadsorbent for removal and recovery of environmental pollutants (oil/hydrocarbon and dye/phenol).

$Research paper thumbnail of Characterization of Spinel‐Type Cobalt and Nickel Oxide Thin Films by X‐Ray Near Grazing Diffraction, Transmission and Reflectance Spectroscopies, and Cyclic Voltammetry$

Journal of The Electrochemical Society, 1995

Characterization of Spinel‐Type Cobalt and Nickel Oxide Thin Films by X‐Ray Near Grazing Diffract... more Characterization of Spinel‐Type Cobalt and Nickel Oxide Thin Films by X‐Ray Near Grazing Diffraction, Transmission and Reflectance Spectroscopies, and Cyclic Voltammetry. [Journal of The Electrochemical Society 142, 1777 (1995)]. ...

Analytical Chemistry, 1982

Self-assembled polyelectrolyte multilayer films comprised of poly(allylamine) derivatized with an... more Self-assembled polyelectrolyte multilayer films comprised of poly(allylamine) derivatized with an Os-(bpy)2ClPyCHcomplex (PAH-Os), and poly(vinylsulfonate), PVS, or poly(styrensulfonate), PSS, have been studied by Fourier transform infrared reflection-absorption spectroscopy. The infrared absorbances of the characteristic SO3-, CH2, NH3 + , and aromatic bipyridine and pyridine groups have been characterized, and their intensity increases with the number of self-assembled layers and redox charge. The characteristic infrared signatures are the 1040 cm-1 band assigned to the aromatic ligands in the osmium complex (ν(Py)), PAH-Os, and the 1040 cm-1 (νs(SO3-)) and 1213 cm-1 (νa(SO3-)) bands for SO3 groups in PVS. The νs(SO3-) vibrational mode of PVS senses the local NH3 + environment of the cationic PAH-Os resulting in a band shift of 22 cm-1 for the first polyallylamine layer. Subtractively normalized Fourier transform infrared spectroscopy during the oxidation of the Os centers in the (PAH-Os)n(PVS)m multilayer reveals that different vibrational modes of bipyridine ligands in the osmium redox center of PAH-Os and the sulfonate groups of PVS are affected by charge-ligand electrostatic interaction and dipole reorganization in the multilayers.

Surface and Coatings Technology, 2016

Abstract In order to improve the oxidation resistance of Nb–Nb 5 Si 3 composites, a multilayer co... more Abstract In order to improve the oxidation resistance of Nb–Nb 5 Si 3 composites, a multilayer coating with a top coating consisting of mixed phases of oxides and chromium borides was made. The substrates were firstly coated with a pure Cr layer by cathodic triode sputtering and then borosiliconized according to a two-step pack cementation process. The as-obtained coatings were characterized using scanning electron microscopy (SEM), energy and wavelength dispersive X-ray spectroscopies (EDS, WDS), X-ray diffraction (XRD), infrared (IRRAS) and Raman spectroscopies. The results showed that the multiphase layer is composed of mixed phases of oxides (silica and borosilicate) and chromium borides (outer layer) and chromium silicide (inner layer). The coating formation mechanism involves a eutectic liquid (43 mol%SiO 2 –57 mol%CrO) created by the reaction between Cr and SiO gas. Oxidation of the chromium borides leads to the formation of boron oxide, which enhances the fluidity of borosilicate phases with a healing effect, the efficiency of which depends on the mass coating.

High Temperature Material Processes (An International Quarterly of High-Technology Plasma Processes), 2004

ABSTRACT To improve the adhesion of alumina coatings on low carbon steel, it is necessary to deve... more ABSTRACT To improve the adhesion of alumina coatings on low carbon steel, it is necessary to develop an oxide layer with a controlled thickness and chemistry at its surface. The best results were obtained with a wustite layer. The Wustite layer (Fe1-xO) is developed on a smooth low carbon iron substrate by its oxidation within a fiirnace under a pure CO2 atmosphere. However, before spraying, a preheating of the substrate and thus of its oxide surface by the plasma is mandatory in order to eliminate condensates and adsorbates. This step of the process induces more or less the transformation of wustite into magnetite (Fe3O4). The purpose of this paper is the study of the influence of the magnetite phase and of the thickness of the oxide layer on the adhesion of Al2O3 coatings. The results show that the control of the oxide layer thickness is very important for a good adhesion which is probably linked to the cohesion of the layer. Below a critical thickness of the oxide layer the rupture of the coating is adhesive (at the interface alumina-iron oxide). Over it is a cohesive rupture inside the oxide layer. The composition of the oxide plays a role that is not still completely clarified, but the physico-chemical continuity of the phases present in the interfacial zone seems to be a crucial point.

Nanoscale, 2012

A laser photochemical process is introduced to realize superhydrophobic conducting carbon coating... more A laser photochemical process is introduced to realize superhydrophobic conducting carbon coatings with broccoli-type hierarchical morphology for use as a metal-free counter electrode in a dye sensitized solar cell. The process involves pulsed excimer laser irradiation of a thin layer of liquid haloaromatic organic solvent o-dichlorobenzene (DCB). The coating reflects a carbon nanoparticle-self assembled and process-controlled morphology that yields solar to electric power conversion efficiency of 5.1% as opposed to 6.2% obtained with the conventional Pt-based electrode.

Materials Chemistry and Physics, 2007

Materials at High Temperatures, 2009

ABSTRACT We report the chemical analysis of 47Nb 16Si 25Ti 8Hf 2Al 2Cr alloy sheet exposed in sta... more ABSTRACT We report the chemical analysis of 47Nb 16Si 25Ti 8Hf 2Al 2Cr alloy sheet exposed in static air at 1200°C for 150, 300, 450, 600 and 900 seconds. This alloy exhibits linear oxidation kinetics. The dendritic phase M5Si3 (with M=Hf and Ti) is observed to be not oxidised rapidly compared to the (Nb,Ti)ss, due to low oxygen solubility.Distribution of elements in the cross section of the oxide scales was analysed by energy-dispersive X-ray spectrometry and mapping in a scanning electron microscope. TiNb2O7 and Nb2O5 have been detected by X-ray diffraction. In addition, Fourier-transform IR spectroscopy showed absorbance peaks which are a clear signature of the formation of Si—O—Si, Si—O—Ti, and Si—O—Hf bonding in the oxidation layer. This analysis suggests that the film contains also amorphous silicates, not detected with X-ray diffraction.

Journal of Solid State Chemistry, 2008

... δ 300 K (mm s −1 ) a, 3.22±0.01. Δ 300 K (mm s −1 ), 1.71±0.02. dδ/dT (mm s −1 K −1 ), (−3.4±... more ... δ 300 K (mm s −1 ) a, 3.22±0.01. Δ 300 K (mm s −1 ), 1.71±0.02. dδ/dT (mm s −1 K −1 ), (−3.4±0.4)10 −4. dΔ/dT (mm s −1 K −1 ), (−3.8±0.4)10 −4. M eff (amu), 122±14. d[ln(A(T)/A(25 K)] (K −1 ), (−8.0±0.5)10 −3. θ D (K), 151±5. f 300 K, 0.09±0.02. f 77 K, 0.51±0.05. f 4 K, 0.74± ...

Materials Science Forum, 1997

Le developpement de la spectroscopie de reflexion speculaire a angle variable dans l'infrarou... more Le developpement de la spectroscopie de reflexion speculaire a angle variable dans l'infrarouge en tant que methode d'analyse de surface necessite la mise en oeuvre de modeles theoriques permettant d'identifier les bandes d'absorption. En consequence, les systemes Cr 2 O 3 /Fe, MnCr 2 O 4 /Fe, TiO 2 /Fe, NiCr 2 O 4 /Fe et NiFe 2 O 4 /Fe ont ete etudies. L'etude etendue aux systemes multicouches permet d'analyser les etapes initiales de l'oxydation d'alliages commerciaux: Incoloy 800, Inconel 600 et X et de mettre en evidence l'influence des elements d'alliage mineurs.