Jacques Pagetti

Electrolytic composite Ni–PTFE coatings: an adaptation of Guglielmi's model for the phenomena of incorporation

Abstract Co-deposition of inert particles in a metallic matrix enables the production of a large range of composite materials with unique properties. Previous work on examination of the effects of the variation of experimental conditions has produced some understanding of the mechanism. When stirring is carried out using a rotating disk electrode, the hydrodynamic conditions are well defined and can be taken into account. In this paper the model proposed by Guglielmi, which does not take into account agitation of the bath, has been used and modified to explain results for Ni–PTFE deposition incorporating a correction based on the speed of magnetic rotation.

Electrolytic and electroless coatings of Ni–PTFE composites: Study of some characteristics

Abstract This work consists of the realization and characterization of composite coatings of Ni–PTFE carried out by electroless deposition on the one hand and electrolytic deposition on the other hand, obtained by pulsed current (CPS) and d.c. current (DC). The evolution of some properties of these coatings generated by various procedures, properties such as morphology, hardness, ductility and wear resistance, are highlighted.

Electrodeposition and characterisation of Ag–ZrO2 electroplated coatings

Ag–ZrO2 electroplated coatings were produced using a classical DC technique in a silver cyanide bath with added ZrO2 particles. Plating parameters, particle concentration and the stirring rate of the bath were systematically investigated in order to calculate the incorporation rate Vp of the particles in the deposit. It was found that the relationships between Vp, current density and stirring rate were related to the particle concentration in the bath. Moreover, it was established that the mechanical and tribological properties of coating composite, like hardness, friction coefficient and wear resistance increased with the increase in incorporation rate Vp.

Determination of the incorporation rate of PTFE particles in Au-Co-PTFE composite coatings by InfraRed Reflection Absorption Spectroscopy

This work follows previous work dealing with the qualitative analysis of Au-Co-PTFE composite coatings for the determination of the PTFE amount in them. The analytical method of InfraRed Reflection Absorption Spectroscopy (IRRAS) which is performed at large angle of incidence (80°) was previously used, but not calibrated. The purpose of this paper is to realize this calibration so as to study the distribution of PTFE in the coating as a function of current density. The quantitative analysis of PTFE is made by EDS, thereby allowing the calibration of IR measurements. The importance of the surface preparation is pointed out especially for analyses by infrared spectroscopy.

Design of a new bilayer polypyrrole-xerogel hybrid coating for corrosion protection

In order to improve the anticorrosion protection properties of polypyrrole (PPy) films deposited on iron or mild steel, the organic conductive polymer was covered by a thermally and mechanically resistant xerogel layer. The anticorrosion protective effect of such a bilayered coating was evaluated by electrochemical measurements (ixa0=xa0f(E); Exa0=xa0f(t); polarization resistance (Rp)) in NaCl (30xa0gxa0L−1) and in HCl (1xa0M) aqueous solutions and by analysis of NaCl and HCl aqueous solutions in which samples coated by PPy and the xerogel were immersed for one and seven days. The results were compared with those obtained, in the same conditions, for naked mild steel plates, PPy or xerogel coated mild steel plates. The bilayer coating ensures a very efficient protection of mild steel against corrosion. nA synergy between PPy and the xerogel was revealed. Moreover, the weak adherence of the xerogel on PPy was improved by the incorporation in the organic polymer of carboxylic acid-functionalized pyrrole units, and the corrosion protection of these modified layers was still increased.

Functionalization of polypyrroles with acids and β-diketones as complexing groups. Part 1: electrochemical synthesis and properties

The synthesis of pyrroles functionalized by complexing groups such as acetylacetone, dibenzoylmethane or carboxylic acids is described, as well as their electrooxidation into functionalized polypyrroles. We have studied the behavior of poly(functionalized pyrrole) films in the presence of Li+, Ni2+ and Co2+ cations by cyclic voltammetry (CV) and infrared (IR) spectroscopy. The electrochemical response under various conditions differs with the nature of the complexing group. We have also demonstrated the possibility to electrochemically generate copolymers with pyrrole and each functionalized pyrrole. The proportion of functional groups in the copolymers was estimated by following n the peak potential dependence in cyclic voltammetry and was confirmed by IR spectroscopy.

Quantitative characterisation of Au–Co–PTFE composite coatings by differential enthalpic analysis

Abstract Energy dispersive spectrometry (EDS) and infrared reflection absorption spectroscopy (IRRAS) have been previously used for the qualitative and quantitative analysis of PTFE in gold–PTFE composite coatings. The inclusion rate of PTFE particles in the composite coating is determined close to the surface by these two methods and particularly within a thickness of 0.5 μm by EDS. Differential scanning calorimetry (DSC) is investigated for a direct determination of the inclusion rate of PTFE, independently of the depth in the coating. The gold matrix allows us to release from metal oxidation and, associated with PTFE (chemically inert), to isolate easily the composite coating by dissolution of the metal support. Correlation is made between the DSC and EDS methods previously proposed as detection tools.

Functionalization of polypyrroles with acids and β-diketones as complexing groups. Part 2: electrochemical growth of polypyrrole into hybrid zirconium oxopolymer sol–gel coatings

New n hybrid materials were prepared by a sol–gel route from zirconium propoxide and functionalized polypyrroles bearing n a complexing group (carboxylic acid or β-diketone). Formation of polypyrroles in the gel deposited on an indium tin oxide (ITO) electrode was performed electrochemically in aqueous media. The optimal conditions for the n preparation of stable sols were determined, as well as the deposition conditions to obtain reproducible transparent n uniform coatings in which electropolymerization was possible. The xerogels as well as the composites after polymerization n were analyzed with the help of optical microscopy (OM), scanning electron microscopy (SEM) and n X-ray fluorescence. The electrochemical characteristics of the composites were investigated by cyclic voltammetry n and their adherence evaluated. From the polymerization rate and simple n assumptions, n the rate constant for pyrrole polymerization inside the gels has been evaluated.

Electrochemical properties of some benzoxazines: conditions for electropolymerization in alkaline medium

Abstract The electro-oxidation of three isomeric methyl benzoxazines has been studied in acetonitrile and methanol in either neutral or alkaline media. Oxidation potentials have been determined and the reactivity of the benzoxazine cation radicals estimated. In alkaline methanol, the mechanism changes in favour of oxidation of the benzoxazine anion, and formation of a thin polymer layer is observed on metallic substrates. The resulting polymers were analysed by X-ray photoelectron spectroscopy measurements and a polymer formula has been proposed.

Electropolymerization of carboxylic acid functionalized pyrrole into hybrid zirconium–silicon oxopolymer sol–gel coatings

We describe the preparation of new hybrid materials using a novel method previously reported by us. These materials are constituted of an organic part and an inorganic network of silicon and zirconium oxopolymers. The organic polymer is obtained by electropolymerization of an N-functionalized pyrrole entrapped in the xerogel. The latter was obtained from a sol prepared by hydrolysis condensation of a mixture of alkoxysilanes, zirconium alkoxydes and the organic monomer. The chemical and electrochemical conditions to prepare these hybrid materials were investigated by varying the zirconium content, the presence and the nature of doping species in the xerogel, the nature of the electrolytic salt and the hydrolysis catalyst. From the results of cyclic voltammetry, optical microscopy, scanning electron microscopy and X-ray fluorescence, we show that the formation of a conducting polymer with good properties in the xerogel depends on the zirconium content and on both the nature and nthe presence of doping species in the xerogel, whereas the influence of the electrolytic salt is very limited.