Antonella Glisenti

Amphiphilic block copolymer/poly(dimethylsiloxane) (PDMS) blends and nanocomposites for improved fouling-release.

Amphiphilic diblock copolymers, Sz6 and Sz12, consisting of a poly(dimethylsiloxane) block (average degree of polymerisation = 132) and a PEGylated-fluoroalkyl modified polystyrene block (Sz, average degree of polymerisation = 6, 12) were prepared by atom transfer radical polymerization (ATRP). Coatings were obtained from blends of either block copolymer (1–10 wt%) with a poly(dimethylsiloxane) (PDMS) matrix. The coating surface presented a simultaneous hydrophobic and lipophobic character, owing to the strong surface segregation of the lowest surface energy fluoroalkyl chains of the block copolymer. Surface chemical composition and wettability of the films were affected by exposure to water. Block copolymer Sz6 was also blended with PDMS and a 0.1 wt% amount of multiwall carbon nanotubes (CNT). The excellent fouling-release (FR) properties of these new coatings against the macroalga Ulva linza essentially resulted from the inclusion of the amphiphilic block copolymer, while the addition of CNT did not appear to improve the FR properties.

XPS characterization of gel-derived silicon oxycarbide glasses

Abstract The results of an XPS study of sol-gel-derived silicon oxycarbide glasses are presented. Si(2p) XPS peak showed the presence of all the possible mixed silicon oxycarbide units, i.e. SiCxO4 − x, 0 ≤ × ≤ 4. C(1s) XPS peak suggested the presence of three components at 283, 284.5–285.0 and 285.5 eV. The first two are due respectively to carbon atoms into CSi4 sites (283 eV) and aromatic carbon environment and/or aliphatic CHx, x = 1, 2 (284.5–285.0 eV), whereas the last one has been assigned to carbon atoms sharing bonds simultaneously with silicon and oxygen atoms forming SiOC units. It was also found that the fracture surface is richer in carbon compared with the bulk.

Study of the surface acidity of an hematite powder

In this work, the interaction between α-Fe2O3 (hematite) powder samples and pyridine, 2,6-dimethyl pyridine, carbon monoxide and carbon dioxide was studied, at atmospheric pressure as well as under high vacuum (HV) conditions. The powder was characterised by means of diffuse reflectance infrared Fourier transform (DRIFT) and X-ray photoelectron spectroscopies (XPS), X-ray diffraction (XRD) and thermal analysis (TGA-DSC). Chemisorption experiments at atmospheric pressure were studied by means of DRIFT spectroscopy while those carried out under HV conditions were followed by means of quadrupolar mass spectrometry (QMS) and XPS. The study of the interaction of pyridine with α-Fe2O3 allowed us to appreciate the presence of both Bronsted and Lewis acid sites on the powder surfaces. Moreover, the use of CO as probe molecule indicated the existence of non equivalent Lewis acid sites. Finally, CO2 may interact with the powder sample either reacting with surface OH groups giving rise to bicarbonate species, or with surface cations and neighbouring oxide ions to originate bidentate carbonate species.

Chemical and compositional changes induced by N+ implantation in amorphous SiC films

The effects of 30 keV N+ implantation in amorphous silicon carbide films deposited on silicon substrates by rf sputtering over a fluence range of 1×1016–2×1017 ions cm−2, are studied by means of x‐ray photoelectron spectroscopy (XPS), Auger electron spectroscopy (AES), and infrared (IR) absorption techniques. The ion‐induced modifications of these films have been investigated on the basis of the chemical state evolution of Si, C, and N (using XPS and AES) and on the basis of the vibrational features of the films components (using IR absorption). The results show that implanted N bonds Si selectively, substituting the C atoms in the silicon carbide, and the C substitution by N results in a composite layer of carbonitrides and free C. An ion‐induced C transport has also been observed and correlations are established between the formation of silicon carbonitrides and the dynamical behavior of the C in the implanted layer. The latter appears as a superposition of (a) a chemically induced atomic redistribution...

A comparison between different fouling-release elastomer coatings containing surface-active polymers

Surface-active polymers derived from styrene monomers containing siloxane (S), fluoroalkyl (F) and/or ethoxylated (E) side chains were blended with an elastomer matrix, either poly(dimethyl siloxane) (PDMS) or poly(styrene-b-(ethylene-co-butylene)-b-styrene) (SEBS), and spray-coated on top of PDMS or SEBS preformed films. By contact angle and X-ray photoelectron spectroscopy measurements, it was found that the surface-active polymer preferentially populated the outermost layers of the coating, despite its low content in the blend. However, the self-segregation process and the response to the external environment strongly depended on both the chemistry of the polymer and the type of matrix used for the blend. Additionally, mechanical testing showed that the elastic modulus of SEBS-based coatings was one order of magnitude higher than that of the corresponding PDMS-based coatings. The coatings were subjected to laboratory bioassays with the marine alga Ulva linza. PDMS-based coatings had superior fouling-release properties compared to the SEBS-based coatings.

Influence of nitrogen doping on different properties of a-C : H

Amorphous hydrogenated carbon (a-C:H) exhibits outstanding properties such as high hardness, low mechanical wear and friction, high thermal conductivity, etc. These properties are irreversibly altered above 400 °C. Doping the a-C:H films with nitrogen revealed the possibility to continuously tune properties such as internal stress, hardness, electrical conductivity and surface energy. X-ray photoelectron spectroscopy has been used to analyze the chemical and structural modifications caused by the introduction of nitrogen into the films. An increased onset temperature of the thermal C-H bond decomposition in a-C:H films up to 600 °C (in vacuum) is observed. Hardness measurements on N-doped samples show an increase in thermal stability of the films, however, without ever reaching the hardness values obtained from the undoped a-C:H film.

Chemical Interactions in Titanium- and Tungsten-Implanted Fused Silica

Abstract Silica glasses were implanted with titanium at energies of 30 and 190 keV at a dose of 5 × 1016 cm−2 and with tungsten at 200 keV and dose of 1.6 × 1016 cm−2 and 5 × 1016 cm−2. A set of titanium- and tungsten-implanted samples was also subsequently implanted with nitrogen in the energy range of 15–100 keV and dose of 2 × 1017 cm−2. Samples were characterized by X-ray photoelectron spectroscopy, secondary ion mass spectrometry, Rutherford backscattering spectrometry, nuclear reaction analysis and, partially, IR-diffuse reflectance. Titanium silicide and titanium oxide compounds were observed in titanium-implanted samples. Subsequent nitrogen implantation destroys the titanium silicide species, inducing the formation of titanium metallic clusters and substoichiometric silicon nitrides: titanium oxides are transformed to titanium oxynitrides. Tungsten implantation causes the formation of metallic tungsten precipitates and the presence of tungsten oxides was observed. Nitrogen implantation favours the formation of tungsten oxynitrides. Thermodynamic considerations were applied to explain the chemical interactions between implanted species and substrate.

High fluence implantation in glasses: chemical interactions

Abstract Results will be given on chemical interactions in amorphous SiO 2 implanted with reactive and non-reactive species. Samples were implanted with nitrogen, silicon, titanium and silver; a set of samples already implanted with these elements (excluding those implanted with nitrogen) has been subjected to a second implant with nitrogen ions. at the dose of 2 × 10 17 ions cm −2 , at different energies. Samples have been characterized by secondary ion mass spectrometry, X-ray photoelectron spectroscopy, nuclear techniques and optical absorption measurements. Radiation damage and chemical effects have been discriminated; precipitation of the implanted species, as well as chemical compound formation in the interaction both between the implanted species and the host matrix and between the implanted species themselves have been detected.

The reactivity of a Fe-Ti-O mixed oxide under different atmospheres : study of the interaction with simple alcohol molecules

Abstract In this paper, the interaction between simple alcohols (methanol to 1-butanol) and a Fe–Ti mixed oxide was investigated. The reactivity of the mixed system was studied both at atmospheric pressure and in vacuum conditions and compared with that of the pure oxides (TiO 2 and Fe 2 O 3 ). To understand the influence of the oxygen presence in the reaction mixture, the reactivity was investigated both in inert gas as well as in oxygen atmosphere. X-ray photoelectron spectroscopy (XPS) and quadrupole mass spectrometry (QMS) have been used for the experiment in high vacuum (HV), while Fourier transform infrared spectroscopy (FTIR) and QMS have been used for the experiment in rough vacuum and under atmospheric pressure conditions. The characterisation of the sample by means of XPS, X-ray diffraction and IR spectroscopy preceded the reactivity study. When compared with Fe 2 O 3 , the Fe–Ti–O mixed oxide seems to be less reactive with respect to the alcohols; the interaction between alcohol and surface is mainly molecular, as in the case of TiO 2 . Moreover, the oxidising power of the mixed oxide is lower than that of Fe 2 O 3 (only traces of carbonic compounds are evident).

Reactivity of simple alcohols on Fe2O3powders

The interaction between α-Fe2O3 powders and methanol, ethanol, propan-1-ol and butan-1-ol has been studied by means of FTIR and XPS. Mass spectrometry has been used to characterise the volatile products. Methanol is chemisorbed mainly dissociatively whereas molecular chemisorption is prevalent in higher alcohols. When methanol is chemisorbed, heating induces the formation of formate (at temperatures >400 K) while hydrocarbons are the main products (at temperatures >500 K) of the other alcohols. Considerations are made concerning surface acidic sites in connection with the thermal treatment of the sample and with alcohol chemisorption.