C. Andreazza-Vignolle

Bio: C. Andreazza-Vignolle is an academic researcher from University of Orléans. The author has contributed to research in topics: Thin film & Sputtering. The author has an hindex of 15, co-authored 39 publications receiving 802 citations. Previous affiliations of C. Andreazza-Vignolle include University of Poitiers & Centre national de la recherche scientifique.

Surface morphology and characterization of thin graphene films on SiC vicinal substrate

Abstract: In this Brief Report we present a study of a 6H-SiC(0001) vicinal substrate annealed at various temperatures under ultrahigh vacuum. By combining x-ray photoelectron spectroscopy and atomic force microscopy, we investigated the morphology and the chemical surface changes accompanying the formation of graphene sheets. After annealing at $1100\text{ }\ifmmode^\circ\else\textdegree\fi{}\text{C}$ step/terrace structures of the SiC substrate are clearly identified and a terrace widening is observed due to step bunching up. At $1300\text{ }\ifmmode^\circ\else\textdegree\fi{}\text{C}$ approximately two graphene layers are formed and the surface steps completely disappear.

Color-Switchable, Emission-Enhanced Fluorescence Realized by Engineering C-dot@C-dot Nanoparticles

Abstract: This paper reports the preparation and properties of color-switchable fluorescent carbon nanodots (C-dots). C-dots that emit dark turquoise and green–yellow fluorescence under 365 nm UV illumination were obtained from the hydrothermal decomposition of citric acid. Dark green fluorescent C-dots were obtained by conjugating prepared C-dots to form C-dot@C-dot nanoparticles. After successful conjugation of the C-dots, the fluorescence emission undergoes a blue-shift of nearly 20 nm (∼0.15 eV) under UV excitation at 370 nm. The C-dots emit goldenrod, green–yellow, and gold light under excitation at 455 nm, which shows that the prepared C-dots are color-switchable. Furthermore, conjugation of the C-dots results in enhanced, red-shifted absorption of the π–π* transition of the aromatic sp2 domains due to the conjugated π-electron system. N incorporation in the carbon structure leads to a degree of dipoles for all the aromatic sp2 bonds. The enhanced absorption in a wide range from 226 to 601 nm indicates extend...

Nucleation and initial growth of platinum islands by plasma sputter deposition

Abstract: The nucleation and islands growth of platinum have been followed from an early stage through to complete substrate coverage. Thus, this study of initial stages of thin film growth has allowed to improve the understanding of growth mechanisms and to control the final nanomaterials structure. In the presented deposition method, the metal atom source is a negatively biased metal wire submitted to the bombardment of ions created in HF plasma. The originality of this plasma sputtering technique is that in addition to the metal atom flux, the substrate surface is submitted to a high flux of low energy ions, inducing a high atomic surface mobility and modifying the growth mode with respect to conventional deposition techniques (magnetron sputtering or evaporation). Platinum deposits have been investigated by ex situ characterisation techniques: grazing incidence-small angle X-ray scattering (GISAXS) and X-ray diffraction (GIXD) in conjunction with transmission electron microscopy (TEM). Using morphological parameters as coverage rate, islands number density and islands size, different mechanisms (scale laws, islands mobility, coalescence, etc.) governing the growth are described vs. Ar ion and Pt atom energies and fluxes.

Surface nitriding of titanium and aluminium by laser-induced plasma

Abstract: In this work we study a nitriding technique for titanium and aluminium by means of laser-induced plasma. The synthesised layers are composed of a nitrogen concentration gradient over several μm depth, and are expected to be useful for tribological applications with no adhesion problems. The method is tested on the synthesis of titanium nitride, and the role of the laser wavelength and pulse time duration is inspected by comparing layers obtained with two kinds of pulsed laser: a CO2 laser (λ=10.6 μm) and an XeCl excimer laser (λ=308 nm). The laser-plasma treatment is then applied to the superficial nitriding of aluminium, which is known to be difficult to carry out. Comparison is made between the nitriding process efficiencies of these two metals.

Surface modification of titanium, titanium alloys, and related materials for biomedical applications

Abstract: Titanium and titanium alloys are widely used in biomedical devices and components, especially as hard tissue replacements as well as in cardiac and cardiovascular applications, because of their desirable properties, such as relatively low modulus, good fatigue strength, formability, machinability, corrosion resistance, and biocompatibility. However, titanium and its alloys cannot meet all of the clinical requirements. Therefore, in order to improve the biological, chemical, and mechanical properties, surface modification is often performed. This article reviews the various surface modification technologies pertaining to titanium and titanium alloys including mechanical treatment, thermal spraying, sol–gel, chemical and electrochemical treatment, and ion implantation from the perspective of biomedical engineering. Recent work has shown that the wear resistance, corrosion resistance, and biological properties of titanium and titanium alloys can be improved selectively using the appropriate surface treatment techniques while the desirable bulk attributes of the materials are retained. The proper surface treatment expands the use of titanium and titanium alloys in the biomedical fields. Some of the recent applications are also discussed in this paper.

Laser Material Processing

Abstract: In the laser treatment of a workpiece (9), e.g. for surface hardening, melting, alloying, cladding, welding or cutting, the adverse effect of reflectivity of the surface, when a pure, monochromatic laser (6) is used, is remedied by the simultaneous application of a relatively shorter wavelength beam (1). The two beams (1)(5) may be combined by a beam coupler (4) or may reach the workpiece (9) by separate optical paths (not shown). The shorter wavelength beam (1) improves the coupling efficiency of the higher- powered laser beam (5).

Innovations in palladium membrane research

Abstract: This review highlights various aspects of current palladium membrane research and serves as a comprehensive bibliography covering palladium membrane preparation methods and applications. There are many promising uses for palladium membranes, although widespread use of the available technologies is constrained primarily by the high cost of palladium, lack of durability due to hydrogen embrittlement, and susceptibility to fouling. Various researchers in the field are tackling these problems and fabricating thinner palladium alloy composite membranes that better withstand contaminantion and thermal cycling. What has been accomplished to address these issues and the directions presently being explored are discussed.