Tuning of anodic oxidation parameters for the production of nanostructured TiO2 films

Titanium dioxide is the most common among titanium oxides and minerals. It can be either synthesized bychemical routes or generated by anodic oxidation of titanium. The latter way allows to tune oxide properties bymodulating process parameters, and it has gained much attention thanks to the wide variety of thicknesses,morphologies, structures and compositions of the oxide produced. The peculiar engineered properties ofanodized titanium find applications in biomedical industry, automotive field, architecture and design, as well asin photovoltaic cells and in photocatalytic purification devices.This article provides an overview of anodic oxidation treatments currently applied to form nanostructured oxidelayers on titanium, paying special attention to their applications

Perfluoropolyethers as superhydrophobizing agents for carbon-based surfaces of fuel cell gas diffusion layers

Perfluoropolyether (PFPE) peroxide confers superhydrophobic properties to carbon black (CB) and carbon cloth (CC) as Gas Diffusion Layer (GDL) materials by direct functionalization. The thermal decomposition of PFPE peroxide synthesizes PFPE radicals which covalently bond the unsaturated moieties on carbonaceous surfaces. PFPE-functionalized CB and CC were characterized by X-ray photoelectron spectroscopy (XPS), surface area analysis, resistivity measurements, scanning electron microscopy (SEM) and contact angle measurements. The PFPE-modified materials resulted superhydrophobic were employed for the fabrication of single and dual layer GDLs. GDLs were tested in a single fuel cell at the lab scale. The cell tests were run at two temperatures (60°C and 80°C) with a relative humidity (RH) of hydrogen and air feeding gases equal to 80/100% and 60/100%, respectively

Immobilization of TiO2 nanopowders in multilayer fluorinated coatings for highly efficient clear and turbid wastewater remediation

The use of nanosized photocatalytic TiO2 in suspension or slurry type reactors is well reported. However, the industrial feasibility of such systems is limited, on account of the low quantum efficiency reported for slurry processes and of the need for a post-treatment catalyst recovery stage, which may present poor efficiency, with the double drawback of dispersing nanoparticles in the environment and losing precious photocatalyst. In this work, the photodegradative activity of titanium dioxide immobilized into a multilayered transparent fluoropolymeric matrix has been studied. Several TiO2 nanostructured powders featuring different primary particle size, crystalline phase and specific surface area have been produced by the flame spray pyrolysis (FSP) of organic solutions containing titanium (IV) isopropoxide. The activity of such powders has been tested and compared to that of TiO2 P25 by Evonik Degussa, which is the reference nanopowder commonly employed in the evaluation of the photocatalytic activity of non-commercial TiO2. A multilayer ionomeric-perfiuorinated matrix has been used to immobilize the powders, having high chemical resistance and transparency towards UV light, good permeability to oxygen and good wettability to favor interactions with the polluted aqueous solutions

Pietro Pedeferri: l'ossidazione anodica tra scienza e arte

The paper is oriented to the study of chlorides corrosion of carbon steel in simulating alkaline concrete pore solutions.Cyclic voltammetries (CV) were performed in order to evaluate the influence of pH, in the range of 12.6-13.8, on theinhibiting properties of nitrite and anions of two organic acid, lactate and aspartate, on localized corrosion initiation.The results confirm that the corrosion resistance of steel in solutions with the same pH of concrete is strictly dependentupon the chlorides-alkalinity ratio (Figures 6, 7). The inhibitors showed an additive contribute to alkalinity withdifferent weight for the three substances considered during testing.The CV tests were performed in aerated solutions at room temperature on disk specimens machined from a carbonsteel bar, with an exposed surface of 0.67 cm2. Disk electrode (RDE) rotating at 2500 rpm was employed for reducingthe effect of diffusion. The test was performed after conditioning of the working electrode at -1 V vs SCE for 60 s, reequilibrationfor 15 s and two polarization cycles between -1.7 and + 1 V vs SCE at 50 mV / s scan rate.Before test, the specimen was passivated in the test solution for 72 hours to grant the formation of a stable protectivelayer on the steel surface without chloride addition. The inhibitors were added into the passivation solution beforethe immersion of specimen, at different concentrations, 0.01, 0.1 and 1 M for sodium nitrite, 1 M for sodium lactateand 0.1 M for sodium aspartate. Two characteristic potentials related to pitting initiation susceptibility, E1,1st and E1,2nd,were derived by the first and the second CV cycle, respectively (Figures 1, 3, 4, 5). The results confirm that the criticalthreshold for localized corrosion initiation can be expressed as a function of a critical [Cl-] / [OH-] ratio; the probabilityof pitting initiation is low in the case of [Cl-] / [OH-] ratio lower than 0.6 (eqs. 1-4). The nitrite addition causes anincrement in the critical [Cl-] / [OH-] ratio (Figure 8-10) that can be quantified by introducing an efficiency parameterf* (eq. 9; Figure 13). This parameter defines the effectiveness of the inhibitor compared to alkalinity. It is about onefor nitrite ions. Thus, nitrite ions show an inhibition of corrosion initiation similar to that of hydroxyl ions. For aspartateions (Figure 11), f* depends upon pH (Figures 14, 15); above 12.6, the higher the pH, the higher the f* was noticed. AtpH equal to 13.8, the aspartate showed a f* value higher than nitrites at the same concentration.Sodium lactate showed an almost nil f* parameter, denoting a negligible inhibition on pit initiation (Figure 12). Thus,the positive effect observed during previous long-term tests on concrete specimens should be ascribed to an effect onthe propagation phase rather than initiation of the localized corrosion

Study and Characterization of Insulating Panels for Sustainable Buildings Made by Waste Cardboard and PCMs

The study and development of an innovative material for building insulation is really important for a sustainable society in order to improve comfort and reduce energy consumption. The aim of this work is the development of insulating panels for sustainable buildings based on an innovative material made of waste paper and PCMs. Phase Change Materials (PCMs) have been used for many years in the building industry as smart insulation technology because of their properties of storing and releasing high quantity of latent heat at useful temperatures. The integration of PCMs into cellulose matrix during the waste paper recycling process has been developed in order to obtain a composite material with enhanced thermal properties suitable for building panels. In order to guarantee safety and durability of the product the addition of flame retardant and anti-humidity additives into the composite material has been studied. The results obtained have shown the possibility to realize an innovative and sustainable material suitable to replace insulating panels presently used