Jean-Luc Delplancke

Galvanostatic anodization of titanium: I. Structures and compositions of the anodic films

Abstract The galvanostatic anodization of commercially pure titanium is studied with current densities lower than 500 A m −2 in 1 M sulphuric acid between 25 and 75°C. Two types of electrochemical behaviour are observed: the first type is characterized by a maximum value of the cell voltage and the second one by a continuous increase of the anode to cathode (which is platinum) potential difference. These different behaviours may be related to different structures of the anodic films (as observed by SEM and TEM) and to the compositions of these films (as determined by Auger analysis, RHEED and HEED).

Sonoelectrochemistry in aqueous electrolyte: A new type of sonoelectroreactor

Abstract A new type of sonoelectroreactor is presented. Its most interesting characteristic is the nature of the working electrode which is made up of the immersed titanium horn itself (anode or cathode). The frequency of the home-made reactor is around 20 kHz. The performances of this sonoelectroreactor are tested during the copper electrodeposition.

Galvanostatic anodization of titanium: II. Reactions efficiencies and electrochemical behaviour model

Abstract The efficiencies of the different anodic reactions observed during the galvanostatic anodization of commercially pure titanium in 1 M sulphuric acid between 25 and 75°C have been studied. The two previously observed electrochemical behaviours are characterized by different kinetics for the anodic film growth, the titanium dissolution, the peroxides formation and the oxygen evolution. Finally, a theoretical interpretation of the obtained data is proposed.

Self-colour anodizing of titanium

Abstract Relations between the colours and the electrochemical parameters (current density, quantity of electricity and temperature of the electrolyte) during the anodization of titanium sheets were studied in a 1 M H 2 SO 4 solution. Mathematical theories were developed for the kinetics of growth of the anodic film and for the colours of this film. These theories show that the relation between the growth and the colour of the film is complicated. Nevertheless, it was possible to find experimental conditions that led to uniform and well-defined colours.

Influence of the anodizing procedure on the structure and the properties of titanium oxide films and its effect on copper nucleation

Abstract Thin oxide films are grown electrochemically on commercially pure titanium substrates. Constant potential (potentiostatic), constant current (galvanostatic) and initial constant current followed by constant potential (combined) growth modes are studied. The structure, the composition, the thickness, the electrochemical and the semiconducting properties of the oxide films are considerably influenced by the growth mode even if the final anodizing potential has a constant value.

Characterisation and behaviour of Ti/TiO2/noble metal anodes

The morphology, composition and the electrical and electrochemical behaviour of the anodic microporous layer, prepared by the galvanostatic anodisation of Ti after sparking, followed by galvanostatic deposition of Pt or Ir have been investigated. These electrodes are proposed to function as dimensionally stable anodes (DSAs). For Ti/TiO2/Pt electrodes, Pt is deposited within some of the micropores of the oxide film. In contrast, for Ti/TiO2/Ir, the metal is deposited preferentially on the top surface. This difference is thought to result from the position of the metal deposition potential with respect to the flat band potential of n-TiO2. Optical imaging of both types of DSA suggests that only a few sites on the surface are responsible for electron exchange at the DSA–electrolyte interface. C-AFM measurements of Ti/TiO2/Pt samples subjected to long-term anodic polarisation, suggest that the Ti-noble metal contact is progressively insulated by thickening of the TiO2 barrier layer, promoting passivation of the DSA. For Ir coated anodes, catalytic activity is directly related to the presence of Ir and to the stability of the catalytic oxide layer. Under Cu electrowinning conditions, the electrochemically formed hydrated Ir oxide was found to be catalytically less stable, than the iridium oxide film subjected to a heat treatment.

Auger Electron Spectroscopy Element Profiles and Interface with Substrates of Electroless Deposited Ternary Alloys

Electroless NiMeP alloys (Me = Cu, Sn, Sb) with high phosphorus content (∼11 weight percent) and a low weight percent of the third component (Me) have been plated in acidic baths onto aluminum, iron, and nickel. Scanning Auger electron spectroscopy is applied to study the element profiles and interface with the substrates. Generally the third component follows the profiles of Ni and P, which proves the alloy formation. A surface enrichment in the third element (Me) is observed in all cases. It is very strong when tin is the third component and very weak in the case of antimony, which is more or less uniformly distributed through the thickness. Decrease of surface concentration of phosphorus is noticed when NiSbP is plated. In Cu profiles three different zones exist : a surface enrichment zone, a groove (a zone of reduced concentration), and a plateau (a zone of almost constant concentration). There is no enrichment in the third element at the interface with the substrate for all three alloys and three substrates. At the interface with aluminum prepared for electroless plating with double zincate pretreatment complete dissolution of the zincate layer has been established.

Influence of Citrate Ions as Complexing Agent for Electrodeposition of CuInSe2 Thin Films

The preparation of CuInSe 2 thin films by electrodeposition is studied. The effect of sodium citrate (Na 3 C 6 H 5 O 7 ) as complexing agent on the electrodeposition of pure copper, indium, selenium and of their ternary alloy is emphasized. Cathodic shifts of the copper and selenium electrodeposition potentials with increasing citrate concentration are observed. On the contrary, the presence of citrate in the electrolyte does not change the indium electrodeposition potential but improves its crystallinity. The surface morphology and the composition of the deposited films are characterized by scanning electron microscopy (SEM). The texture of the deposits and their compositions are analyzed by X-ray diffraction. The formation of CuInSe 2 films with a chalcopyrite structure and good stoichiometry is observed.

Electroless deposited Ni-Re-P, Ni-W-P and Ni-Re-W-P alloys

Coatings of electroless Ni–W–P, Ni–Re–P and Ni–W–Re–P alloys were plated in alkaline citrate baths containing amino alcohols, but not free ammonia ions. The reference Ni–P alloy was used as an intermediate layer in the sandwich: Ni–Me–P/Ni–P/substrate. An extremely homogeneous thickness distribution of all alloy components was found by applying scanning Auger electron spectroscopy (SAES(. The inclusion of refractory metals at the expense of nickel and without substantial change in phosphorus content was established. A non-oxidized state of the codeposited Re and W in Ni–W–P, Ni–Re–P and Ni–W–Re–P alloys was determined by means of X-ray photoelectron spectroscopy examination, as well as by SAES profiles, revealing the absence of oxygen throughout the coatings. All alloy films are amorphous and paramagnetic.

Preparation of stable suspensions of gold nanoparticles in water by sonoelectrochemistry

Stable suspensions of gold nanoparticles in water were prepared with high yield by a novel one-step ultrasound assisted electrochemical process. Various strategies based on the addition of either tailor-made polymers or mixtures of commercially available polymers, in the electrochemical bath have been found successful to avoid nanoparticles aggregation commonly observed by sonoelectrochemistry. alpha-Methoxy-omega-mercapto-poly(ethylene oxide) or poly(vinyl pyrrolidone)/polyethylene oxide mixtures were able to build up a coalescence barrier around the gold nanoparticles. The results showed that the size of the gold nanoparticles could be easily tuned between 5 nm and 35 nm by simple control of the electrochemical parameters, i.e. the deposition time (T(ON)) from 10 ms to 20 ms. The properties of as-prepared gold nanoparticles were compared to the ones of gold colloids prepared by the more conventional wet nanoprecipitation method using chemical reductive agents.