Anticorrosion Superhydrophobic Surfaces on AA6082 Aluminum Alloy by HF/HCl Texturing and Self-Assembling of Silane Monolayer.

In this paper, the tailoring of superhydrophobic surfaces on AA6082 aluminum alloy by chemical etching in an HF/HCl solution, followed by silane self-assembling, was applied for enhanced corrosion protection in the marine field. In particular, different etching times were considered in order to optimize the treatment effect. The results indicate that all the prepared surfaces, after silanization, were characterized by superhydrophobic behavior with a contact angle higher than 150°. The contact and sliding angles strongly depend on the surface morphology at varying etching times. The optimum was observed with an etching time of 20 s, where a microscale coral-like structure coupled with a homogeneous and ordered pixel-like nanostructure was obtained on the aluminum surface showing a Cassie-Baxter superhydrophobic behavior with a water contact angle of 180° and a sliding angle equal to 0°. All superhydrophobic surfaces achieved an enhanced corrosion protection efficiency and impedance modulus up to two orders of magnitude higher than the as-received AA6082 in simulated seawater.

Effect of Chemical Surface Texturing on the Superhydrophobic Behavior of Micro-Nano-Roughened AA6082 Surfaces.

Superhydrophobic surfaces on 6082 aluminum alloy substrates are tailored by low-cost chemical surface treatments coupled to a fluorine-free alkyl-silane coating deposition. In particular, three different surface treatments are investigated: boiling water, HF/HCl, and HNO3/HCl etching. The results show that the micro-nano structure and the wetting behavior are greatly influenced by the applied surface texturing treatment. After silanization, all the textured surfaces exhibit a superhydrophobic behavior. The highest water contact angle (WCA, ≈180°) is obtained by HF/HCl etching. Interestingly, the water sliding angle (WSA) is affected by the anisotropic surface characteristics. Indeed, for the HF/HCl and the HNO3/HCl samples, the WSA in the longitudinal direction is lower than the transversal one, which slightly affects the self-cleaning capacity. The results point out that the superhydrophobic behavior of the aluminum alloys surface can be easily tailored by performing a two-step procedure: (i) roughening treatment and (ii) surface chemical silanization. Considering these promising results, the aim of further studies will be to improve the knowledge and optimize the process parameters in order to tailor a superhydrophobic surface with an effective performance in terms of stability and durability.

Synthesis, Characterization and Photocatalytic Behavior of SiO2 @nitrized-TiO2 Nanocomposites Obtained by a Straightforward Novel Approach.

We report on the facile synthesis of SiO2 @nitrized-TiO2 nanocomposite (NST) by calcination of TiO2 xerogel with OctaAmmonium POSS® (N-POSS; POSS=polyhedral oligomeric silsesquioxanes). The as-obtained nanoporous mixed oxide is constituted by uniformly distributed SiO2 and nitrized-TiO2 , where the silica component is present in an amorphous state and TiO2 in an anatase/rutile mixed phase (92.1 % vs. 7.9 %, respectively) with very small anatase crystallites (3.7 nm). The TiO2 lattice is nitrized both at interstitial and substitutional positions. NST features a negatively charged surface with a remarkable surface area (406 m2 g-1 ), endowed with special adsorption capabilities towards cationic dyes. Its photocatalytic behavior was tested by following the degradation of standard aqueous methylene blue and methyl orange solutions under UV and visible light irradiation, according to ISO 10678:2010. For comparison, analogous investigations were carried out on a silica-free N-TiO2 , obtained by using NH4 Cl as nitrogen source.

Towards a rational design of materials for the removal of environmentally relevant cations: polymer inclusion membranes (PIMs) and surface-modified PIMs for Sn2+ sequestration in aqueous solution.

This work is focused on the design and preparation of polymer inclusion membranes (PIMs) for potential applications for stannous cation sequestration from water. For this purpose, the membranes have been synthesized employing two polymeric matrices, namely, polyvinylchloride (PVC) and cellulose triacetate (CTA), properly enriched with different plasticizers. The novelty here proposed relies on the modification of the cited PIMs by selected extractants expected to interact with the target cation in the membrane bulk or onto its surface, as well as in the evaluation of their performances in the sequestration of tin(II) in solution through chemometric tools. The composition of both the membrane and the solution for each trial was selected by means of a D-Optimal Experimental Design. The samples such prepared were characterized by means of TG-DTA, DSC, and static contact angles investigations; their mechanical properties were studied in terms of tensile strength and elastic modulus, whereas their morphology was checked by SEM. The sequestering ability of the PIMs toward stannous cation was studied by means of kinetic and isotherm experiments using DP-ASV. The presence of tin in the membranes after the sequestration tests was ascertained by µ-ED-XRF mapping on selected samples.

Effect of the Compositions on the Biocompatibility of New Alumina-Zirconia-Titania Dental Ceramic Composites.

Dental implant biomaterials are expected to be in contact with living tissues, therefore their toxicity and osseointegration ability must be carefully assessed. In the current study, the wettability, cytotoxicity, and genotoxicity of different alumina-zirconia-titania composites were evaluated. The surface wettability determines the biological event cascade in the bioceramic/human living tissues interface. The measured water contact angle indicated that the wettability strongly depends on the ceramic composition. Notwithstanding the contact angle variability, the ceramic surfaces are hydrophilic. The cytotoxicity of human gingival fibroblast cells with materials, evaluated by an (3-(4,5 methylthiazol-2-yl)-2,5-diphenyl-tetrazolium bromide (MTT) test, revealed an absence of any cytotoxic effect. A relationship was found between the cell viability and the wettability. It was subsequently deduced that the cell viability increases when the wettability increases. This effect is more pronounced when the titania content is higher. Finally, a comet test was applied as complementary biocompatibility test to detect any changes in fibroblast cell DNA. The results showed that the DNA damage is intimately related to the TiO2 content. Genotoxicity was mainly attributed to ceramic composites containing 10 wt.% TiO2. Our research revealed that the newly developed high performance alumina-zirconia-titania ceramic composites contain less than 10 wt.% TiO2, and display promising surface properties, making them suitable for dental implantology applications.

Thermo-Physical Characterization of Carbon Nanotube Composite Foam for Oil Recovery Applications.

To meet the increasing demands for effective cleanup technologies to deal with the oil spill accidents that significantly affect the ecological and environmental systems, promising composite materials based on carbon nanotubes containing silicone foams were investigated. Pump oil, kerosene, and virgin naphtha had been used to assess, during sorption tests, foams behavior. Test results highlighted the advantage of the hydrophobic and oleophilic behavior of carbon nanotubes, and their high mechanical strength for oil spill recovery application was studied. In order to better relate the property-structure relationship for this class of materials, the role and influence of functionalized nanotubes on thermo-physical and morphological characteristics of the foams had been evaluated. The results showed how the pristine nanotubes fillers, despite functionalized ones, led to optimal composite foam performances with high hydrophobic (62 mg g-1) and oleophilic (6830 mg g-1 in kerosene oil) characteristics. The evidenced high oil selectivity was a relevant key point in order to consider the suitable material for oil spill recovery applications. Eventually, the proposed configuration exhibited the best thermo-physical performances and high reusability, leading to the optimal cost-benefits option.