Sergio Antonio Pellice

Hybrid Sol-Gel Coatings Produced from TEOS and γ-MPS

Hybrids sols from tetraetoxysilane (TEOS) and 3-(methacryloxypropyl) trimethoxysilane (γ-MPS) were prepared in acid medium for different TEOS/γ-MPS ratios and were modified by the addition of a colloidal silica suspension. The stability of the different sols was evaluated by viscosity measurements; the sols showed a Newtonian behaviour and the ageing effect was negligible even after two months from their preparation. Coatings were obtained by dipping at different withdrawal rates and heat-treated between 150 and 250°C. Transparent coatings with thickness higher than 4 μm were reached for most of the studied compositions. The surface microhardness of coatings for each composition and thermal treatment was evaluated by the pencil hardness test. The thermal stability was followed by simultaneous thermogravimetric and differential thermal analysis (TGA-DTA) determining the limit temperatures at which the coatings can be treated without losingits hybrid character. A structural analysis was made by deconvolution of Fourier transformed infrared spectra (FTIR) of self-supported films observing the influence of the organic groups on the silica network.

Coatings Containing Silica Nanoparticles and Glass Ceramic Particles Applied onto Surgical Grade Stainless Steel

Metals are the most used materials as orthopaedic or dental implants for their excellent mechanical properties. However they are not able to create a natural bonding with the mineralized bone and they could release metallic particles that could finally end in the removal of the implant. A promising alternative to avoid those effects is to protect the implant with a biocompatible coating. In this work there are analyzed two kinds of protective organic-inorganic coatings made by sol gel technique with the adding of silica particles, in order to increase the barrier effect of the coating, and glass-ceramic (GC) particles with the aim of generating bioactivity. X-ray photoelectron spectroscopy (XPS) and electrochemical techniques were used to analyze the bioactive and protective response of this silica reinforced coatings with the adding GC particles applied on surgical grade stainless steel.

Epoxy-silica/clay nanocomposite for silver-based antibacterial thin coatings: Synthesis and structural characterization

Development of new functional coatings in the field of health care, as antibacterial applications, deals with a straight control of the diffusive properties that rules the releasing of the active component. In this work, the development of a silver-rich nanocomposite thin coating, loaded with organically modified clay nanoparticles, is presented. The synthesis process included an environment-friendly silanization process of clay nanoparticles (Laponite® S482) with (3-glycidoxypropyl)trimethoxysilane (GPTMS) and the further hydrolytic condensation with tetraethoxysilane (TEOS). Silanization process and the obtained coatings were analysed by Fourier transformed infrared spectroscopy, UV-visible spectroscopy, X-ray diffraction, thermogravimetric curves and scanning electron microscopy. The silanization process of clay nanoparticles with the organically reactive alkyl alkoxysilane, allowed to stabilize and exfoliate the clay nanosheets within a hybrid organic-inorganic sol-gel material. Ring opening of grafted epoxy groups carried to an increasing of the basal spacing, of intercalated clay nanosheets, from 1.3 to 1.8nm. Moreover, incorporation of organically modified clay nanosheets introduced a significant stabilization on the development of silver nanoparticles inside the structure of the nanocomposite coating, retaining the silver inside the coating material and restricting the growing of silver nanoparticles on the surface of the coating. Antibacterial behaviour, against E. coli cultures, performed through agar diffusion tests, provided promising results that allow assuming that the studied nanocomposite coating serves as a reservoir of ionic silver, permitting the antibacterial effect.

Synthesis and characterization of silver-rich coatings loaded with functionalized clay nanoparticles

AbstractA synthetic exfoliated nanoclay smectite type, Laponite® S482, was incorporated as a functionalized load in a silica hybrid matrix synthesized by the sol–gel route. The previous functionalization was carried out through a “grafting” reaction with (3-glycidoxypropyl)trimethoxysilane (GPTMS) assisted by ultrasonic dispersion. The precursor sols were synthesized by acid-catalyzed hydrolytic condensation between tetraethoxysilane (TEOS) and functionalized GPTMS, a silver ions source was added in order to obtain a coating material with controlled silver releasing properties. Coatings were obtained by “dip-coating” on different substrates. Structural characterization of the coatings was conducted by SAXS and SEM-EDS, the results revealed a complex silica matrix with intercalated nanoclays, an organic fraction and a homogeneous content of Ag+. The electrochemical characterization was realized by EIS tests on stainless steel coated substrates AISI 316L type; the results showed good barriers properties and a high integrity of the coatings loaded with nanoclay. The evolution of the release of Ag+ ions was studied by XRF, through exposing the coatings to a leaching process at steady state and determining the residual content of Ag within the coat at different immersion times. It was found that the addition of 1.5 wt. % of clay, in respect to condensed silica, decreased the initial diffusion rate of Ag+ ions at near the half part, allowing its potential use in the development of antibacterial coatings with longer terms of life.