V. Martina

Study of Polymer Particles Suspensions for Electrophoretic Deposition

Recently a great interest has been expressed in electrophoretic deposition (EPD) of polymers, both as particles and as chains. It is generally accepted that also for polymer particles, the Derjaguin-Landau-Verwey-Overbeek (DLVO) theory is valid, therefore, in principle, polymer suspensions suitable for EPD could be easily obtained by dispersing polymer particles in an aqueous or nonaqueous medium. Nevertheless, this work demonstrated that in order to obtain good quality deposits based on poly(ether ether ketone) (PEEK) and poly(tetrafluoroethylene) (PTFE), some additives have to be used. In the case of PEEK, a dispersant providing citrate anions was successfully used, whereas for PTFE a steric suspension stabilization was reached by adding polyvinylpyrrolidone (PVP). In such a way, codeposition of PEEK and PTFE was achieved. The efficiency of the EPD process was demonstrated by means of differential scanning calorimetry (DSC) measurements. A thermal program consisting of heat/cool/heat cycles at a low rate was used in order to evaluate the crystalline amount of each polymer in the deposits. In order to explain the obtained results, it needed to also consider the dimension and structural characteristic of the polymer particles.

A Chemometric Study of Alumina/PEEK and Hydroxyapatite/PEEK Suspensions Prepared for Electrophoretic Deposition of Multifunctional Coatings

Poly(etherether-ketone) (PEEK) suspensions in ethanol and isopropanol containing also α-alumina and hydroxyapatite powders were studied. An innovative method was used in the study of the quality of suspensions. We studied suspensions by means of zeta potential and grain-size measurements. The comparison amongst the different suspensions was carried out by using statistical and chemometric tools, especially by the use of an explorative test based on the Principal Component Analysis (PCA). The chemometric analysis was performed by involving different combinations of each type of powder and each type of solvent.

Hybrid Conducting Nanocomposites Coatings for Corrosion Protection

Recently, several studies in the fields of new materials have introduced the possibility to use CPs as suitable matrices to disperse nanostructured elements, such as nanoparticles or nanotubes. It has been shown that the introduction of nanostructures into a polymer matrix can improve the electrical conductivity and the mechanical properties of the original polymer matrix. The combination of conductive polymers with conductive particles (better if carbon nanostructures), producing a new class of materials known as hybrid conducting nanocompo‐ sites, has already shown some synergistic properties, with a variety of applications in the energy field.

A Comparison between Conventional Thermal Treatment and Excimer Laser Irradiation Performed on Alumina/PEEK Composite Coatings

Poly(etherether-ketone)-alumina coating were deposited by EPD. In order to densify the coatings, conventional thermal treatments were performed at a temperature equal or higher than the melting point of the polymer. The samples treated at the lower temperature showed an increase in the quality of crystallinity of the polymer. As an alternative method, an excimer laser was used to treat the surface of the composite coatings. The laser beam irradiation did not induce any modification in the crystalline structure of the polymer and at the same time did not produce strong degradation of the polymer molecule, also when the laser beam fluence was higher than the ablation limit. The most relevant modification induced by both the treatments was a change in the morphology and the porosity.

Nickel Electrodeposition on Electrophoretically Deposited Carbon Nanotube Films

Multi-walled carbon nanotubes (CNTs) were deposited by electrophoretic deposition on stainless steel substrates forming homogeneous porous CNT deposits. These CNT structures were then coated with a thin layer of Ni by electrodeposition. SEM and TEM observations confirmed that the Ni layer covered uniformly the CNT surfaces. This Ni coating treatment could facilitate the dispersion of CNTs in metal matrix composites leading to improved mechanical and thermal properties.

Functional Characterisations of Hybrid Nanocomposite Films Based on Polyaniline and Carbon Nanotubes

The combination of nanoparticles and conducting polymers, known as hybrid conducting nanocomposites, is a new emerging field. The combination of conductive polymers, such as polyaniline (PANI), with conductive carbon nanotubes (CNTs) has already shown some synergistic properties. As a consequence, they have a variety of applications, such as sensors, actuators, touch screens, etc.. Usually PANI and CNTs are combined by using electrochemical synthesis starting with the monomer aniline. In this work PANI-CNTs nanocomposite films were obtained by using different combinations of two methods, Electrochemical Deposition (ELD) and Electrophoretic Deposition (EPD). The samples prepared by using these combined methods were compared with the material prepared by the usual electrochemical synthesis. Therefore, all the films so prepared were characterised and their electrochemical properties were investigated, particularly for evaluating their use as supercapacitor components.