Rust morphology characterization of polyurethane and acrylic-based marine antifouling paints after salt spray test on scribed specimens

A newly developed, polyurethane-based, marine antifouling coating, containing 2% immobilized Econea, was examined in terms of its anticorrosion performance. The novelty of the experimental formulation arises from the immobilization of the biocide which minimizes leaching and was accomplished via a newly developed functionalization method, based on reaction of the biocide with highly reactive isocyanate functionality. The painting system was applied on steel specimens, then scribed with a sharp cutter and examined for 12 weeks in cyclic salt spray exposure. Identification of the rust morphologies was performed with XRD, Raman spectroscopy, SEM, and EDS methods. The absence of paint deformation during the experiment led to the formation of compact corrosion products, firmly adherent to the substrate, allowing transformation to more protective forms, such as oxides (hematite, maghemite, magnetite) and the least harmful of the oxyhydroxides (goethite, feroxyhyte), found in the mixture, ensuring sufficient corrosion protection. The unscratched part of the paint served as a barrier to corrosion product expansion beyond the scribed areas. An acrylic-based antifouling system was also examined for reasons of comparison. The experimental formulation exhibited superior anticorrosion performance overall, since the acrylic system presented extended material loss, blistering, checking, and extensive substrate rust coverage beneath the multilayer coat, implying unsatisfactory corrosion protection.     

Organic derivatization of single-walled carbon nanotubes by clays and intercalated derivatives

Single-walled carbon nanotubes were derivatized by the catalytic action of aluminosilicate minerals. Hydrothermal treatment of carbon nanotubes with clay and an aliphatic acid gave side alkylated carbon nanotubes-clay composites, which could be of value in various technological applications. XRD pattern indicates that alcylated carbon nanotubes are intercalated between the clay layers. Following acid demineralization, functionalized carbon nanotubes were obtained and characterized.     

MASS TRANSFER EFFECTS ON THE ETCH RATE OF GAAS IN FLOW SYSTEMS

In industrial wet etching reactors, the fluid contacts the substrate surface as a spray of flowing stream, thus introducing mass-transfer resistances to the reaction rate. The etching of gallium arsenide in H₂O₂-NH₄OH-H₂O solutions was studied using an open-channel flow reactor to simulate the industrial conditions. The etch rate was always lower than that obtained under kinetic control, and the dependence of etch rate on H₂O₂ concentration shifted closer to first order. From the calculation of the ratio of rate constant to mass-transfer coefficient, the reaction-rate and mass-transfer resistances were both significant in this system. When the mass-transfer coefficient was calculated from equations for flow past a flat plate, the prediction of etch rate was good, particularly when the starting length for velocity boundary layer development ahead of concentration boundary layer development was taken into account. Another approach for the calculation of mass-transfer coefficient, based on the assumptions for flow between parallel plates, best represented the relative insensitivity of etch rate to fluid velocity.     

Microstructure and mechanical properties of zirconia stabilized with increasing Y2O3, for use in dental restorations

The present in vitro study aims at characterizing dental zirconia ceramics, which are stabilized with a high amount of Y₂O₃. Two groups of specimens were fabricated by computer-aided design/computer-aided manufacturing technique. The specimens of each group were divided into two subgroups (SGs): SGs 1a and 2a contained a relatively low amount of Y₂O₃ (6–8 wt.%), whereas SGs 1b and 2b contained a higher amount of Y₂O₃ (8–10 wt.%). The influence of yttria content on their microstructure and mechanical properties was experimentally determined. The statistical significance of the differences in the mechanical properties between the SGs was evaluated by the t-test (p < 5% was considered statistically significant). Homogeneous and dense ceramics with fine nanostructure, comprising grains of yttria-stabilized tetragonal and cubic zirconia, sized between ∼160 and ∼800 nm, were produced. The increase of yttria content, which causes an increase in grain size, favors the formation of cubic zirconia, resulting in mechanical properties’ slight reduction; yet, the differences were not statistically significant. Consequently, the mechanical properties (HV 11.74–12.91 GPa, and K_IC 2.66–4.25 MPa m^0.5) and the good esthetics of the investigated zirconia ceramics stabilized with high yttria content qualify these zirconia materials for fabricating dental restorations, because they can approach the properties and the esthetics of dental hard tissues as well as the tooth structure.     

On the importance of total polar phenols to monitor the stability of Greek virgin olive oil

A large number of virgin olive oil samples obtained from different areas in Greece were analyzed for various quality parameters. The work focuses on the colorimetric determination of total phenols with the Folin‐Ciocalteu reagent and its importance in predicting shelf life of virgin olive oil. The results indicate a good correlation of total polar phenol content with the stability of the oil. Colorimetric determination of ortho‐diphenol content does not seem to be a better means for predicting virgin olive oil stability. RP‐HPLC quantification of hydroxytyrosol and tyrosol in their free form gives poor results in the case of freshly extracted oils. It is concluded that until an easy‐to‐manage HPLC method will be available, which will quantify accurately both free and bound forms of hydroxytyrosol and other phenolics, the colorimetric method for the determination of total polar phenols remains a good practical means to evaluate the stability of virgin olive oil.     

Interaction of Cis- and Trans-RuCl (2)(DMSO)(4) With Human Serum Albumin

The interaction between cis- and trans- RuCl(2)(DMSO)(4) and human serum albumin have been investigated through UV-Vis, circular dichroism, fluorescence spectroscopy and inductively couplet plasma atomic emission spectroscopy (ICP(AES)) method Albumin can specifically bind 1 mole of cis-isomer and 2 moles of the trans-isomer RuCl(2)(DMSO)(4) complex. The interaction of RuCl(2)(DMSO)(4) with HSA causes: a conformational change with the loss of helical stability of protein; the strong quenching of the Trp 214 fluorescence indicating that the conformational change of the hydrophobic binding pocked in subdomain IIA takes place; a local perturbation of the warfarin binding site and induce some conformational changes at neighbour domains, a changing of the binding abilities towards heme.     

Microwave‐induced enhancement of the dissolution rate of poorly water‐soluble tibolone from poly(ethylene glycol) solid dispersions

In this study, solid dispersions of poorly water‐soluble Tibolone in a poly(ethylene glycol) matrix were prepared with conventional melt mixing and microwave irradiation. The results of the assay content, LC–MS, and ¹H‐NMR indicated that microwave irradiation did not affect drug stability when a relatively low irradiation power (440 W) was used. Fourier transform infrared spectroscopy indicated that there were no hydrogen bonds formed between Tibolone and poly(ethylene glycol), and this affected the drug's crystallinity and its particle size distribution. The dissolution rate of the drug was slightly higher in the case of dispersions prepared by microwave irradiation. This enhancement of the drug dissolution rate was probably due to the lower size of the Tibolone particles in the dispersions prepared by microwave irradiation. The application of microwaves represents a promising alternative to conventional preparative methods of drug dispersions. The main advantage in comparison with conventional melt mixing is that solid dispersions can be prepared in much shorter times. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Aviation fuel JP-5 and biodiesel on a diesel engine

Naval aviation turbine fuel, JP-5, has been accepted as alternative to JP-8 in the frame of the Single Fuel Policy. This has resulted in some ongoing research on JP-5 fuel for its application as a naval single fuel. The necessity to cope with the environmental problems identified in the process of implementing the Single Fuel Policy as well as the strict requirements of modern diesel engines has lead to the need of improved single fuel quality. The development of biomass derived substitutes for diesel, such as biodiesel, is a possible attractive solution. The present paper is an effort to evaluate JP-5 along with diesel and biodiesel for use in a diesel engine. These fuels were used alone and in various mixture fractions in a single cylinder stationary diesel engine in order to evaluate their performance under defined operating conditions of the engine. JP-5 reduced both the NOx and particulate matter emissions as compared to the reference fuel case. Biodiesel significantly lowered particulate emissions, but slightly increased NOx emissions and fuel consumption. Fuel sulfur content has an undesired effect on smoke opacity. Biodiesel increased the fuel consumption when added to petroleum fuels and the increase was larger at high engine loads. Diesel and JP-5 showed similar fuel consumption, with diesel consumption increasing at high engine loads. Ternary blends showed similar behavior. The blends with lower biodiesel content showed lower volumetric fuel consumption.     

Adsorption of polluting substances on activated carbons prepared from rice husk and sugarcane bagasse

Rice husk and sugarcane bagasse were chemically impregnated with ZnCl₂ and carbonized at 700 °C in a large-scale rotary furnace. The activated carbons (ACs) obtained had BET surface area of 811 and 864 m²/g, respectively, and were essentially microporous. The adsorption of arsenic, humic acid, phenol and a municipal solid waste landfill leachate was examined. Both ACs showed the best adsorption behaviour towards phenol, removing around 80% at the equilibrium time of 4 h. The adsorption isotherms for arsenic and humic acid were also favourable, although the maximum loadings achieved were lower than that of phenol. Finally, the rice husk AC showed 60% and 70% removal efficiency for colour and COD, respectively, when tested on a landfill leachate.