Sandra Dire - Academia.edu (original) (raw)

Papers by Sandra Dire

Materials, Oct 11, 2020

This study aims to demonstrate the remarkable features of graphene-based fillers, which are able ... more This study aims to demonstrate the remarkable features of graphene-based fillers, which are able to improve the protective performance of acrylic coatings. Furthermore, the joint application of a cataphoretic primer and a spray top coat, containing graphene and functionalized graphene oxide flakes, respectively, enables the deposition of a double-layer coating with high conductivity and abrasion resistance properties, capable of offering excellent corrosion resistance to the metal substrate. The surface morphology of the single-and double-layer coatings was investigated by optical and electron microscopies, analysing the defectiveness introduced in the polymer matrix due to the filler agglomeration. The behavior in aggressive environments was assessed by exposure of the samples in the salt spray chamber, evaluating the blister formation and the adhesion level of the coatings. Electrochemical impedance spectroscopy measurements were employed to study the corrosion protection properties of the coatings, whose conductivity and abrasion resistance features were analysed by conductivity assessment and scrub tests, respectively. The incorporation of graphene-based fillers in the cataphoretic primer improves the corrosion protection properties of the system, while the graphene flakes provide the top coat spray layer with high conductivity and excellent abrasion resistance features. Thus, this work demonstrates the possibility of employing different types of graphene-based fillers and deposition methods for the creation of multifunctional coatings.

Coatings, Jun 26, 2020

This study aims to demonstrate the excellent protective performance of functionalized graphene ox... more This study aims to demonstrate the excellent protective performance of functionalized graphene oxide (fGO) flakes in acrylic cataphoretic coatings. The filler content provides an important contribution in improving the chemical and mechanical resistance of the acrylic matrix. The morphology of the fillers was first investigated by optical and electron microscopy, analysing the distribution of the fGO flakes within the polymer matrix. After that, the flakes were added to the cataphoretic bath in different concentrations, resulting in four series of samples. The cathodic delamination of the coatings was assessed with cathodic polarization cycles and with measurements carried out with a scanning Kelvin probe. Finally, the abrasion resistance at the macroscopic and microscopic level was studied by scrub testing and scratching atomic force microscopy analysis, respectively. The incorporation of fGO at the optimized concentration of 0.2 wt.% greatly increases the cathodic delamination resistance of the acrylic matrix, resulting in an effective barrier against the effects of absorbed aggressive substances. Graphene-based fillers also enhance abrasion resistance, thanks to their high mechanical strength. Thus, this work demonstrates the great protective benefits that can be obtained when using fGO flakes as reinforcing fillers in cataphoretic coatings.

Springer eBooks, 2018

The use of general descriptive names, registered names, trademarks, service marks, etc. in this p... more The use of general descriptive names, registered names, trademarks, service marks, etc. in this publication does not imply, even in the absence of a specific statement, that such names are exempt from the relevant protective laws and regulations and therefore free for general use. The publisher, the authors and the editors are safe to assume that the advice and information in this book are believed to be true and accurate at the date of publication. Neither the publisher nor the authors or the editors give a warranty, express or implied, with respect to the material contained herein or for any errors or omissions that may have been made. The publisher remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Sensors, Apr 14, 2021

This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY

Journal of Applied Physics

The aim of this work is to highlight the correlation between treatment conditions, composition, a... more The aim of this work is to highlight the correlation between treatment conditions, composition, and structure of reduced zinc oxide (ZnO:Zn) with optical and radioluminescence properties for the production of high yield scintillating powders. Purchased zinc oxide (ZnO) powders (≈0.35 ± 0.15 μm) were thermally reduced in Ar/H2 (3%) atmosphere at temperatures ranging between 600 (≈0.40 ± 0.17 μm) and 1000 °C (≈6.4 ± 1.6 μm), obtaining ZnO:Zn powders. The reduction degree, evaluated through energy dispersive spectroscopy, showed a linear increase from 0% up to 20% (800 °C sample), reaching a plateau condition at about 25% for the highest treatment temperatures (1000 °C sample). Structural analysis highlighted the existence of a threshold temperature, previously reported in the literature, around 800 °C, beyond which (i) the grain size remarkably increases, (ii) the shape changes from hexagonal to round-shaped, and (iii) the intensity of electron spin resonance (ESR)-active defects at g...

Journal of Photochemistry and Photobiology A: Chemistry

Composites Science and Technology

Polymer Degradation and Stability

Journal of Alloys and Compounds

Materials Chemistry and Physics, 2022

ZnO is a worldwide used activator for a rubber vulcanization process, which promotes fast curing ... more ZnO is a worldwide used activator for a rubber vulcanization process, which promotes fast curing kinetics and high cross-linking densities of rubber nanocomposites (NCs). However, its extended use together with leaching phenomena occurring during the production and life cycle of rubber products, especially tires, entails potential environmental risks, as ecotoxicity toward aquatic organisms. Pushed by this issue, a novel activator was developed, which introduces highly dispersed and active zinc species in the vulcanization process, reducing the amount of employed ZnO and keeping high the curing efficiency. The activator is constituted by Zn(II) single sites, anchored on the surface of SiO 2 nanoparticles (NPs) through the coordination with functionalizing amino silane groups. It behaves as a doublefunction material, acting at the same time as a rubber reinforcing filler and a curing activator. The higher availability and reactivity of the single-site Zn(II) centers toward curative agents impart faster kinetics and higher efficiency to the vulcanization process of silica/ isoprene NCs, compared to conventionally used ZnO activators. Moreover, the NCs show a high cross-linking degree and improved dynamic mechanical properties, despite the remarkably lower amount of zinc employed than that normally used for rubber composites in tires. Finally, the structural stability of Zn(II) single sites during the curing reactions and in the final materials may represent a turning point toward the elimination of zinc leaching phenomena.

Dalton Transactions, 2021

A novel heteroleptic Co(ii) complex has been synthesized, characterized and successfully evaluate... more A novel heteroleptic Co(ii) complex has been synthesized, characterized and successfully evaluated as a precursor for the CVD of Co3O4 thin films with tailored properties.

Electrochimica Acta, 2020

Lanthanoid cations are commonly employed as active corrosion inhibiting agents inside sol-gel coa... more Lanthanoid cations are commonly employed as active corrosion inhibiting agents inside sol-gel coatings derived from organosilanes. However, the effect of lanthanoids on the structure of sol-gel coatings derived from organoalkoxysilanes is still not completely clear and object of debate. Even if it has been reported that lanthanoid ions have a beneficial effect in terms of corrosion protection properties, it has not been completely understood if it is related to the active inhibition of the local electrochemical activity or to a modification of the sol-gel coating structure. In addition, it is still not clear how the lanthanoid ions are distributed in. In order to get some insights into the effect of lanthanoids on the structural and electrochemical properties of sol-gel layers, the present work employs gadolinium ions. Gd was selected also for its magnetic and electronic properties, which strongly affects the signals intensity of many spectroscopy techniques. Accordingly, Gd ions act as a marker to evaluate the localization of lanthanoids in the hybrid network. The structural effect on the sol-gel films promoted by the addition of gadolinium ions has been assessed by means of solid state nuclear magnetic resonance (NMR), Fourier transform infrared (FT-IR) spectroscopy and electron spin resonance (ESR) spectroscopy. The structural features of the Gd-doped coatings have been correlated with their electrochemical response obtained by means of polarization curves and electrochemical impedance spectroscopy (EIS).

Soft Matter, 2021

“Hairy” nanoparticles (HNPs), i.e. inorganic nanoparticles functionalized with polymer chains, ar... more “Hairy” nanoparticles (HNPs), i.e. inorganic nanoparticles functionalized with polymer chains, are promising building blocks for the synthesis of advanced nanocomposite (NC) materials having several technological applications.

Polymer Journal, 2021

Silk sericin (SS) is a natural polymer widely studied in the design of biodegradable materials fo... more Silk sericin (SS) is a natural polymer widely studied in the design of biodegradable materials for cosmetic, biomedical, food, and chemical applications. This work was designed to explore the molecular and structural characteristics of SS extracted from different silk sources with different processing degrees: high-quality cocoons (NCs), defective cocoons (DCs), and raw silk yarn (Y). The last two sources have been less studied. SS solutions were obtained from each source using the high-temperature and high-pressure degumming method (HTHP). The molecular weight distribution and amino acid composition of SS extracts were determined using gel permeation chromatography (GPC) and reversed-phase chromatography (RP HPLC), respectively. SS films were formed from each solution and then characterized by attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR), nuclear magnetic resonance spectroscopy (NMR), and differential scanning calorimetry (DSC). Water uptake and degradation of SS films were also evaluated. The molecular characteristics of SS extracts were related to the processing degree of the silk source. Moreover, the properties of SS films seemed to be dominated by the primary structure and the presence of natural impurities in each extract. The results suggest that silk sources could be selected ad hoc to design SS materials with distinctive properties for specific applications. Three different silk sources were explore for sericin (SS) extraction and film formation. Features of each raw material, especially the degree of processing, have remarkable effects on the primary structure and the presence of nonprotein compounds in the sericin extract. As a result, sericin films exhibited distinctive properties that seemed to be correlated with the amount of natural impurities and the molecular properties of the SS extract obtained from each raw material.

Journal of colloid and interface science, Jan 15, 2018

Organic-inorganic nanobuilding blocks (NBBs) based on silsesquioxanes (SSQs) have potential appli... more Organic-inorganic nanobuilding blocks (NBBs) based on silsesquioxanes (SSQs) have potential applications as nanofillers, thermal stabilizers, and rheological modifiers, which can improve thermomechanical properties of polymer hosts. The possibility to tune both siloxane structure and pendant groups can promote compatibilization and peculiar interactions with a plethora of polymers. However, the control on SSQs molecular architecture and functionalities is usually delicate and requires careful synthetic details. Moreover, investigating the influence of NBBs loading and structure on the hybrid interface and, in turn, on the polymer chains mobility and mechanical properties, may be challenging, especially for low-loaded materials. Herein, we describe the preparation and characterization of polybutadiene (PB) nanocomposites using as innovative fillers thiol-functionalized SSQs nanobuilding blocks (SH-NBBs), with both tailorable functionality and structure. Swelling experiments and, more...

European Journal of Inorganic Chemistry, 2016

Thiol‐functionalized nanobuilding blocks (NBBs) were synthesized from 3‐mercaptopropyltrimethoxys... more Thiol‐functionalized nanobuilding blocks (NBBs) were synthesized from 3‐mercaptopropyltrimethoxysilane by using the in situ water production (ISWP) process in which the water needed to hydrolyze the precursor was provided by means of an esterification reaction. In the present study the reaction between 1‐propanol and chloroacetic acid was used. Whereas the growth of the Si oligomers was followed at room temperature and 100 °C using 1D 29Si and 2D 1H–29Si heteronuclear single quantum correlation (HSQC) NMR spectroscopic experiments, the amount of water delivered along the process was followed by means of 1H NMR spectroscopy. The results show a good correlation between the evolution of the degree of condensation and the amount of water produced in situ. They also point to the preferential formation of cagelike structures and the narrowing of the species distribution over long reaction times. The average size of the growing oligomers was estimated from their diffusion coefficient, whic...