1,720,966 research outputs found
Electrochemical behaviour of nickel–aluminium bronze in chloride media: influence of pH and benzotriazole
No full textThe corrosion properties of the nickel–aluminium bronze (NAB) in aqueous chloride media were investigated at different pHs by using linear potential sweep voltammetry and scanning electron microscopy. The NAB electrochemical behaviour was dependent on the solution pH, due to the different stabilities of the phases present within its microstructure. In particular, at solution pHs higher than 4.0 the NAB oxidation was driven by the dissolution of the copper-rich ?-phase, whereas at pH values lower than 4.0 its anodic behaviour was controlled by the oxidation of the iron-, nickel- and aluminium-rich ?I-, ?II- and ?IV-phases. Furthermore, a kinetic model for the NAB oxidation, in neutral chloride solutions, was developed on the basis of the observed behaviour, i.e., order of reactions of NAB with respect to protons and chloride. Finally, considering the high affinity of benzotriazole for copper, the corrosion performance of NAB was studied in the presence of the inhibitor in neutral (pH of 6.2) and acidic (pH of 3.5) chloride solutions, where NAB exhibited different anodic behaviours
The study of aluminium anodes for high power density Al/Air batteries with brine electrolytes
No full textAluminium alloys containing small additions of both tin (~0.1 wt %) and gallium (~0.05 wt %) are shown to dissolve anodically at high rates in sodium chloride media at room temperatures; current densities >0.2 A cm-2 can be obtained at potentials close to the open circuit potential, ~-1500 mV vs SCE. The tin exists in the alloys as a second phase, typically as ~1 ?m inclusions (precipitates) distributed throughout the aluminium structure, and anodic dissolution occurs to form pits around the tin inclusions. Although the distribution of the gallium in the alloy could not be established, it is also shown to be critical in the formation of these pits as well as maintaining their activity. The stability of the alloys to open circuit corrosion and the overpotential for high rate dissolution, both critical to battery performance, is shown to depend on factors in addition to elemental composition; both heat treatment and mechanical working influence the performance of the alloy. The correlation between alloy performance and their microstructure has been investigated
Sensors for corrosion detection: measurement of copper ions in 3.5% sodium chloride using screen-printed platinum electrodes
Full text linkPlanar screen-printed platinum electrodes developed for use in corrosion monitoring have been evaluated using cyclic differential pulse voltammetry and shown to detect cupric ions (Cu2+) over a range up to 100 mM in a background of 3.5% by weight sodium chloride solution. The reduction of Cu2+ to metallic copper is shown to proceed as two successive single-electron transfer reactions involving an intermediate chemical step where the cuprous ion (Cu+) is complexed by chloride to form the dichlorocuprous anion CuCl2-. By comparison, the complexation step during the oxidation of copper to Cu2+ can involve a number of different chlorocopper(I) complexes of the general form [CuCl(n+1)]n- depending on the chloride concentration, which can make detection via a stripping reaction difficult
The environment factors affecting the performance of nickel-aluminum bronze (NAB)
No full textCorrosion and galvanic compatibility studies of a cast nickel-aluminum bronze, NAB (UNS C95800), coupled with an area ratio 1:1 to titanium and a cupronickel (Cu-15Ni) alloy, have been made in brackish seawater. The galvanic currents and mixed-potentials have been routinely monitored for a period of 6 months (from January ’03 to June ’03) as part of a 3 year program. Additionally, environmental factors including dissolved oxygen, seawater temperature and salinity, have been studied in order to assess their affects on the corrosion performance of NAB in natural seawater. Accelerated corrosion rates for the NAB coupled to titanium or Cu-Ni alloy have occurred compared with the uncoupled NAB. Subsequent testing has shown the accelerated corrosion rates are linked to the biofouling season and the local test environment. Corrosion rates decrease at the end of the fouling season. Decoupled potentials indicate a significant polarization of the cathode component, which has been attributed to a surface modification of the titanium and Cu-Ni alloy by the formation of a biofilm. In the case of the Cu-Ni, an enrichment in iron and nickel within the oxide film may also be involved
Modern approaches to marine antifouling coatings
Full text linkMarine structures such as platforms, jetties and ship hulls are subject to diverse and severe biofouling. Methods for inhibiting both organic and inorganic growth on wetted substrates are varied but most antifouling systems take the form of protective coatings. Biofouling can negatively affect the hydrodynamics of a hull by increasing the required propulsive power and the fuel consumption. This paper reviews the development of antifouling coatings for the prevention of marine biological fouling. As a result of the 2001 International Maritime Organization (IMO) ban on tributyltin (TBT), replacement antifouling coatings have to be environmentally acceptable as well as maintain a long life. Tin-free self-polishing copolymer (SPC) and foul release technologies are current applications but many alternatives have been suggested. Modern approaches to environmentally effective antifouling systems and their performance are highlighted
Review on the development of truly portable and in-situ capillary electrophoresis systems
No full textCapillary electrophoresis (CE) is a technique which uses an electric field to separate a mixed sample into its constituents. Portable CE systems enable this powerful analysis technique to be used in the field. Many of the challenges for portable systems are similar to those of autonomous in-situ analysis and therefore portable systems may be considered a stepping stone towards autonomous in-situ analysis. CE is widely used for biological and chemical analysis and example applications include: water quality analysis; drug development and quality control; proteomics and DNA analysis; counter-terrorism (explosive material identification) and corrosion monitoring. The technique is often limited to laboratory use, since it requires large electric fields, sensitive detection systems and fluidic control systems. All of these place restrictions in terms of: size, weight, cost, choice of operating solutions, choice of fabrication materials, electrical power and lifetime. In this review we bring together and critique the work by researchers addressing these issues. We emphasize the importance of a holistic approach for portable and in-situ CE systems and discuss all the aspects of the design. We identify gaps in the literature which require attention for the realization of both truly portable and in-situ CE systems
Life under flow: a novel microfluidic device for the assessment of anti-biofilm technologies
No full textIn the current study, we have developed and fabricated a novel lab-on-a-chip device for the investigation of biofilm responses, such as attachment kinetics and initial biofilm formation, to different hydrodynamic conditions. The microfluidic flow channels are designed using computational fluid dynamic simulations so as to have a pre-defined, homogeneous wall shear stress in the channels, ranging from 0.03 to 4.30?Pa, which are relevant to in-service conditions on a ship hull, as well as other man-made marine platforms. Temporal variations of biofilm formation in the microfluidic device were assessed using time-lapse microscopy, nucleic acid staining, and confocal laser scanning microscopy (CLSM). Differences in attachment kinetics were observed with increasing shear stress, i.e., with increasing shear stress there appeared to be a delay in bacterial attachment, i.e., at 55, 120, 150, and 155?min for 0.03, 0.60, 2.15, and 4.30?Pa, respectively. CLSM confirmed marked variations in colony architecture, i.e.,: (i) lower shear stresses resulted in biofilms with distinctive morphologies mainly characterised by mushroom-like structures, interstitial channels, and internal voids, and (ii) for the higher shear stresses compact clusters with large interspaces between them were formed. The key advantage of the developed microfluidic device is the combination of three architectural features in one device, i.e., an open-system design, channel replication, and multiple fully developed shear stresses
Characterisation of crevice and pit solution chemistries using capillary electrophoresis with contactless conductivity detector
No full textThe ability to predict structural degradation in-service is often limited by a lack of understanding of the evolving chemical species occurring within a range of different microenvironments associated with corrosion sites. Capillary electrophoresis (CE) is capable of analysing nanolitre solution volumes with widely disparate concentrations of ionic species, thereby producing accurate and reliable results for the analysis of the chemical compositions found within microenvironment corrosion solutions, such as those found at crevice and pit corrosion sites. In this study, CE with contactless conductivity detection (CCD) has been used to characterize pitting and crevice corrosion solution chemistries for the first time. By using the capillary electrophoresis with contactless conductivity detection (CE-CCD) system, direct and simultaneous detection of seven metal cations (Cu2+, Ni2+, Fe3+, Fe2+, Cr3+, Mn2+, and Al3+) and chloride anions was achieved with a buffer solution of 10 mM 2,6-pyridinedicarboxylic acid and 0.5 mM cetyltrimethylammonium hydroxide at pH 4 using a pre-column complexation method. The detection limits obtained for the metal cations and chloride anions were 100 and 10 ppb, respectively. The CE-CCD methodology has been demonstrated to be a versatile technique capable of speciation and quantifying the ionic species generated within artificial pit (a pencil electrode) and crevice corrosion geometries for carbon steels and nickel-aluminium bronze, thus allowing the evolution of the solution chemistry to be assessed with time and the identification of the key corrosion analyte targets for structural health monitoring
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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