Aluminium–air cells are high-energy density (<400 W h kg−1) primary batteries developed in the 1960s. This review shows the influence of the materials, including: aluminium alloy, oxygen reduction ...catalyst and electrolyte type, in the battery performance. Two issues are considered: (a) the parasitic corrosion of aluminium at open-circuit potential and under discharge, due to the reduction of water on the anode and (b) the formation of a passive hydroxide layer on aluminium, which inhibits dissolution and shifts its potential to positive values. To overcome these two issues, super-pure (99.999 wt%) aluminium alloyed with traces of Mg, Sn, In and Ga are used to inhibit corrosion or to break down the passive hydroxide layer. Since high-purity aluminium alloys are expensive, an alternative approach is to add inhibitors or additives directly into the electrolyte. The effectiveness of binary and ternary alloys and the addition of different electrolyte additives are evaluated. Novel methods to overcome the self-corrosion problem include using anionic membranes and gel electrolytes or alternative solvents, such as alcohols or ionic liquids, to replace aqueous solutions. The air cathode is also considered and future opportunities and directions for the development of aluminium–air cells are highlighted.
► Discussion of the rationale to choose a suitable alloy for Al–air battery. ► Effect of the properties and preparation route to enhance the oxidation of Al. ► Effect of the inhibitors on the anode oxidation in the alkaline electrolyte. ► Comparison of the performance of high-activity oxygen reduction electrodes.
Marine 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.
Nickel–aluminium bronze (NAB) alloys show good corrosion resistance under marine conditions. The corrosion behaviour of cast and wrought NAB alloys is illustrated in this work through a range of ...electrochemical techniques including open-circuit potentiometry with time, oxygen reduction voltammetry, NAB dissolution voltammetry, potential step (or flow step) current transients and linear polarisation resistance. The galvanic coupling of NAB to stainless steel or copper is examined by zero resistance ammetery. The importance of using controlled flow working electrodes is illustrated by the use of a rotating disc electrode, a rotating cylinder electrode and a bimetallic (NAB/copper–nickel) rotating cylinder electrode. In addition to controlling the hydrodynamics, such electrodes allow charge transfer data to separate from those of mass transport control under mixed kinetic control. Longer term seawater immersion trials on planar coupons coupled to titanium or cupronickel are also reported. The relative contributions of erosion and corrosion attack are considered using a wall-jet electrode and the corrosion characteristics of NAB are compared to those of copper and copper–nickel in chloride media.
Many global environmental agendas, including halting biodiversity loss, reversing land degradation, and limiting climate change, depend upon retaining forests with high ecological integrity, yet the ...scale and degree of forest modification remain poorly quantified and mapped. By integrating data on observed and inferred human pressures and an index of lost connectivity, we generate a globally consistent, continuous index of forest condition as determined by the degree of anthropogenic modification. Globally, only 17.4 million km
of forest (40.5%) has high landscape-level integrity (mostly found in Canada, Russia, the Amazon, Central Africa, and New Guinea) and only 27% of this area is found in nationally designated protected areas. Of the forest inside protected areas, only 56% has high landscape-level integrity. Ambitious policies that prioritize the retention of forest integrity, especially in the most intact areas, are now urgently needed alongside current efforts aimed at halting deforestation and restoring the integrity of forests globally.
Electrolytic plasma techniques have been used to surface modify 6082 aluminium alloy to a depth of 100 mm. Potentiodynamic polarisations and electrochemical impedance spectroscopy (EIS) have been ...made under static conditions in order to evaluate the corrosion performance of both unsealed and sealed PEO coatings. The erosion and erosion corrosion performance of the unsealed PEO Al2O3 coating has also been assessed for a range erodent kinetic energies which varied between 0.016 and 7.1 mJ. The erosion and erosion-corrosion tests were carried out using subangular sand particles ranging in size from 135 to 235 mm. Scanning electron microscopy (SEM) was used to investigate the coating microstructure and the coating/substrate interface. The analyses show that the PEO Al2O3 coatings studied in this investigation had a pore/crack network to the Al alloy substrate, which compromised the corrosion performance and ultimately the erosioncorrosion performance.
A new mechanistic model has been established for the chemical and electrochemical mechanisms controlling nickel–aluminium bronze crevice corrosion. The crevice corrosion was initially confined to ...eutectoid regions with slight attack of the copper rich α-phase within the α+κ
III eutectoid. In the presence of high chloride concentrations, copper and aluminium complexes form and the hydrolysis of these complexes leads to the acidification of the crevice solution chemistry. As the crevice solution becomes increasingly acidic the initial protection of the κ-phases due to their higher aluminium contents is lost and become anodic to the α-phase. The continuous nature of the κ
III-phase makes it vulnerable with an ∼80
μm depth of attack after only the first month which is accompanied by internal copper redeposited at cathodic sites. Crevice corrosion of copper-based alloys is often reported to be controlled by a copper-ion concentration cell, however, for nickel–aluminium bronze it appears that primarily the crevice corrosion propagation results from a combined action of localised acidification and differential aeration between the bold and occluded zones. This mechanistic understanding provides further insights in to the development of crevice corrosion experienced by nickel–aluminium bronze after long-term exposures to natural seawater for up to 3 years.
This study aims to understand the physical processes invoked when solid particle erosion occurs in a corrosive media. The literature on wear-corrosion shows some effort has been placed in qualifying ...the interactions between erosion and corrosion leading to ‘synergistic’, ‘additive’ and ‘antagonistic’ terms. These terms are difficult to quantify experimentally with multiple experiments being required and generate considerable errors often suggesting these interactive terms are negligible. Hence the current work seeks to investigate these interactions, the errors associated with their measurement and gain understanding of the processes involved by careful examination of microstructural and mechanical property changes of surfaces subjected to erosion–corrosion. Cast nickel–aluminium bronze/NaCl solution has been chosen to study as this system has been studied at Southampton for several years.
In situ electrochemical, gravimetric and topographical analyses have been evaluated and discussed using microstructural and hardness measurements.
•An innovative approach to investigate the flow corrosion mass transfer kinetics in a wall-jet electrode.•Wall-jet oxygen reduction diffusion coefficients were lower compared other electrode ...geometries.•Greater turbulence intensities at wall-jet electrodes gave higher mass transfer coefficients for oxygen reduction at copper and NAB surfaces.
This work has investigated the corrosion performance and mass transfer of oxygen on copper and nickel-aluminium bronze surfaces within a wall-jet flow cell assembly. Limiting currents of the dissolved oxygen mass-transfer kinetics as a function of volume flow rate at a wall-jet electrode were examined for copper and nickel-aluminium bronze in a 3.5 wt.% NaCl solution. Mass transfer kinetics for the reduction process studied was compared with rotating disc and cylinder electrode data. The wall-jet electrode mass transfer coefficients for commercially pure copper and cast nickel-aluminium bronze were determined to be 0.01-0.06 cm s–1 and 0.01-0.05 cm s–1, respectively.
Perfusion MR imaging measures of relative CBV can distinguish recurrent tumor from posttreatment radiation effects in high-grade gliomas. Currently, relative CBV measurement requires normalization ...based on user-defined reference tissues. A recently proposed method of relative CBV standardization eliminates the need for user input. This study compares the predictive performance of relative CBV standardization against relative CBV normalization for quantifying recurrent tumor burden in high-grade gliomas relative to posttreatment radiation effects.
We recruited 38 previously treated patients with high-grade gliomas (World Health Organization grades III or IV) undergoing surgical re-resection for new contrast-enhancing lesions concerning for recurrent tumor versus posttreatment radiation effects. We recovered 112 image-localized biopsies and quantified the percentage of histologic tumor content versus posttreatment radiation effects for each sample. We measured spatially matched normalized and standardized relative CBV metrics (mean, median) and fractional tumor burden for each biopsy. We compared relative CBV performance to predict tumor content, including the Pearson correlation (
), against histologic tumor content (0%-100%) and the receiver operating characteristic area under the curve for predicting high-versus-low tumor content using binary histologic cutoffs (≥50%; ≥80% tumor).
Across relative CBV metrics, fractional tumor burden showed the highest correlations with tumor content (0%-100%) for normalized (
= 0.63,
< .001) and standardized (
= 0.66,
< .001) values. With binary cutoffs (ie, ≥50%; ≥80% tumor), predictive accuracies were similar for both standardized and normalized metrics and across relative CBV metrics. Median relative CBV achieved the highest area under the curve (normalized = 0.87, standardized = 0.86) for predicting ≥50% tumor, while fractional tumor burden achieved the highest area under the curve (normalized = 0.77, standardized = 0.80) for predicting ≥80% tumor.
Standardization of relative CBV achieves similar performance compared with normalized relative CBV and offers an important step toward workflow optimization and consensus methodology.
Researchers have been analyzing the costs of carbon sequestration for approximately twelve years. The purpose of this paper is to critically review the carbon sequestration cost studies of the past ...dozen years that have evaluated the cost-effectiveness of the forestry option. Several conclusions emerge. While carbon sequestration cost studies all contain essentially the same components they are not comparable on their face due to the inconsistent use of terms, geographic scope, assumptions, program definitions, and methods. For example, there are at least three distinct definitions for a `ton of carbon' that in turn lead to significantly different meanings for the metric `dollars per ton of carbon'. This difference in carbon accounting further complicates comparison of studies. After adjusting for the variation among the studies, it appears that carbon sequestration may play a substantial role in a global greenhouse gas emissions abatement program. In the cost range of 10 to 150 dollars per ton of carbon it may be possible to sequester 250 to 500 million tons per year in the United States, and globally upwards of 2,000 million tons per year, for several decades. However, there are two unresolved issues that may seriously affect the contribution of carbon sequestration to a greenhouse gas mitigation program, and they will likely have counteracting effects. First, the secondary benefits of agricultural land conversion to forests may be as great as the costs. If that is the case, then the unit costs essentially disappear, making carbon sequestration a no-regrets strategy. In the other direction, if leakage is a serious issue at both the national and international levels, as suggested by some studies, then it may occur that governments will expend billions of dollars in subsidies or other forms of incentives, with little or no net gain in carbon, forests or secondary benefits. Preliminary results suggest that market interactions in carbon sequestration program analyses require considerably more attention. This is especially true for interactions between the forest and agricultural land markets and between the wood product sink and the timber markets.
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