Cast Anode Research Articles

Формирование и исследование свойств покрытий из металлического стекла FeWCrMoBC на стали 35

Introduction. To obtain metallic glass coatings it is necessary to achieve high cooling rates of melt. FeWCrMoBC composition has high melt viscosity and sufficient glass-forming ability to fix of the amorphous state at cooling rates implemented by electric discharge alloying with the use of a crystalline electrode. The purpose of the work is one-stage deposition of amorphous coating by electric discharge alloying, using crystalline anode FeWCrMoBC, prepared by casting and studying the properties of modified surface of carbon steel: wettability, high-temperature resistance, tribological properties. Methods and Results. The structure of anode and coatings was investigated by X-ray diffraction analysis in CuKα radiation on a DRON-7 diffractometer. In contrast to the X-ray patterns of the anode material, sharp Bregg reflexes were not observed on the X-ray patterns of the coatings, but a wide halo was present in the range of angles 2Ѳ = 40–50°, which indicates its amorphous structure. The cyclic high-temperature resistance test was carried out at 700 °C for 100 hours. The wear rate and coefficient of friction of the specimens were studied under dry sliding friction at a speed of 0.47 m/s at a load of 25 N with the use of a counterbody made of high-speed steel M45. The influence of the discharge pulse duty cycle on the character of mass transfer (anode erosion, cathode weight gain, mass transfer coefficient) during coating formation was investigated. With a decrease in the duty cycle of the discharge pulses up to 9 times, the erosion of the anode increased up to 5 times, and the cathode mass gain increased up to 2.2 times. The maximum mass-transfer coefficient was achieved at the highest duty cycle. An increase in a number of surface properties of carbon steel after coating was observed: the hardness of the surface of the specimens increased by 2.3–2.6 times; the average thickness of the coatings was in the range of 56–80.6 µm; the wetting angle was in the range of 108.4–121.3°; the coefficient of friction decreased by 1.2–1.4 times; the wear resistance increased by 2–3.3 times; oxidizability in air decreased by 14–18 times. Scope and Conclusions. The achieved higher properties (hardness, wear resistance, high-temperature resistance, and hydrophobicity) of the executive surfaces of parts made of carbon steel after deposition of the proposed coatings can be used in various branches of engineering production. The results of the work confirmed the possibility of deposition of metallic glass coatings by electric discharge alloying with the use of cast anode material FeWCrMoBC on carbon steel.

Novel concept of bolt-microtubular geometry for solid oxide fuel cells

This study introduces a proof of concept for a novel solid oxide fuel cell geometry called bolt-microtubular. Bolt-microtubular anode supports are formed by winding tape cast anode support strip on a threaded rod followed by isostatic pressing. Bolt-microtubular cells are built by dip coating other cell layers on these supports. Conventional microtubular anode supports and cells are also fabricated similarly for comparison and, microstructural, mechanical and electrochemical investigations are carried out. Different anode current collection strategies are also examined. The results indicate that with the proposed methods thread patterns can be successfully created on the anode supports and bolt-microtubular anode supports without any structural damages can be obtained after sintering. Although three point bending tests show ∼27% decrease in the fracture strength of the anode supports with bolt-microtubular design for the wall thickness studied, bolt-microtubular cells outperform microtubular ones due to enhanced electrolyte-electrode interfaces and effective current collection. The highest peak electrochemical performance of 0.293 Wcm−2 at 800 °C is obtained from the bolt-microtubular cell with external current collection, whereas the maximum power density of classical microtubular cell under the same operating conditions is 0.227 Wcm−2. The overall results reveal that bolt-microtubular design is promising and deserves further investigations.

Influence of heat treatment on the discharge performance of Mg-Al and Mg-Zn alloys as anodes for the Mg-air battery

This work investigated the use of heat treatment to improve the battery performance of cast Mg-6Zn and Mg-8Al anodes for primary Mg-air batteries. The reason for anodic efficiency drop was quantitively analyzed. Anodes after heat treatment had a discharge voltage that was higher and more-stable than that of cast anodes, attributed to a higher open circuit voltage and smoother exfoliation of discharge products. The solution heat-treated Mg-6Zn had the best discharge capacity of 1185 mAh g−1 and an anodic efficiency of 56 % at 40 mA cm−2, compared with 928 mAh g−1 and 44 % for as-cast Mg-6Zn at the same current density. The T6 treated (solution and annealing) Mg-8Al anodes produced the best discharge capacity of 1418 mAh g−1 and anodic efficiency (at 40 mA cm−2) of 63 %. Heat treatment also enhanced the peak energy density from 926 mWh g−1 (2.5 mA cm−2) to 1463 mWh g−1 (at 10 mA cm−2 after solution treatment) for Mg-6Zn and from 1501 mWh g−1 (20 mA cm−2) to 1736 mWh g−1 (at 20 mA cm−2 after the T6 heat treatment) for Mg-8Al. These improvements were caused by suppressing the anodic hydrogen reaction and dissolving harmful large-sized precipitates. Heat treatment should be considered essential in the production of high-performance anodes for Mg-air batteries.

Corrosion and discharge performance of a magnesium aluminum eutectic alloy as anode for magnesium–air batteries

Magnesium aluminum eutectic alloy (Mg–34 % Al) was prepared as anode of magnesium–air battery with a view to decrease the corrosion rate of magnesium anode. Results indicate that as–cast eutectic alloy has a lower corrosion rate and a lower discharge activity in 3.5 % NaCl solution. The assembled battery with as–cast eutectic alloy as anode, a water soluble graphene poly (sodium 4–styrenesulfonate)/graphene based NaCl solution and a graphene/Mn3O4 nanometre composite as air cathode catalyst has a higher discharge activity. Lower corrosion rate of as–cast anode is due to corrosion products of black aluminum–rich oxide formed in fine lamella β–Mg17Al12 phase.

Influence of Zr and Be on microstructure and electrochemical behavior of AZ63 anode

In this study, the effect of Zr and Be on the microstructure and electrochemical properties of a common magnesium alloy anode, AZ63, used in cathodic protection, was investigated. The AZ63, as well as Zr (0.25, 0.50, 0.70, and 0.90 wt%) and Be (0.0001, 0.001, 0.01, and 0.1 wt%) bearing AZ63 anodes, were prepared. The microstructure and electrochemical characteristics of the cast anodes were characterized. The results showed that the addition of Zr refines the grain size of the AZ63 anode; and above 0.5 wt% Zr, forms Al2Zr and β‐Mg17Al12. In contrast, grain coarsening was observed with increasing Be content. Moreover, the addition of 0.1 wt% Be to the anode resulted in the spheroidization of the β‐phase. Also, it was shown that AZ63‐0.5 wt% Zr provides the lowest corrosion rate among the experimented anodes, and the higher the Be content, the lower the corrosion rate of the anode. Higher content of both Be and Zr alloying elements resulted in improved efficiency of the anode for 20% and 13%, respectively. The results of this study indicate higher impact of Be on the efficiency increment of the AZ63 anode.

Recovery of metals from anodic dissolution slime of waste from electric and electronic equipment(WEEE) by extraction in ionic liquids

The recovery of metals from a multi-component alloy obtained by crushing, melting and anodic dissolu-tion of waste from electric and electronic equipment(WEEE) was investigated. The anodic dissolution of the alloy was carried out in an electrolysis cell with one copper cathode and a central cast anode, immersed in the electrolyte formed by choline chloride-ethylene glycol-iodine. The temperature of the electrolyte during the process was 343 K. Depending on the electrolysis parameters(current density and cell voltage), cathodic deposits of Sn, Pb and Zn of >99% purity were obtained. Cyclic voltammetry was used in order to determine the deposition potentials of the studied metals. The obtained metallic deposits were subject of determination of XRD, SEM/EDX and AFM in order to evidence the deposits structure and morphology. The experiments performed demonstrated the possibility of separating/selective recovery of metals from the multi-component alloy resulted from the waste from electrical and electronic equipment by anodic dissolution in ionic liquids.

Corrosion Behavior of Al-Zn-In Sacrificial Anode Alloys Produced by Conventional Casting and Semi-Solid Metal Casting Processes

A challenge in producing a sacrificial anode through conventional casting method is that the alloying elements in casting segregate during solidification, which further causes non-uniform anode corrosion reducing anode performance. In this paper, we investigated the performance of Al-5Zn-0.02In anode produced by conventional casting compared with by semi-solid casting technique. The performance of produced anodes were measured in terms of anode potential, current capacity, consumption rate and anode efficiency in 3.5% NaCl solution for 14 days. We found that the microstructure of the conventional cast anode had dendrites and coarse grains and the corrosion caused pitting corrosion. In contrast, the semi-solid cast anode had fine grains without any dendrites. The corrosion attacked mainly the grain boundaries and less on the matrix. Surprisingly, the conventional cast anode has about 10% higher efficiency than that of semi-solid cast anode.

Fabrication and Electrochemical Characterization of Freeze-Cast Tubular Solid Oxide Fuel Cells

NASA and others have shown improved power density of planar solid oxide fuel cells (P-SOFCs) fabricated via the freeze casting technique. As a manufacturing process, freeze casting is capable of producing ceramic, metal, and cermet components with unique and tailorable microstructural features that enhance SOFC performance. Low thermo-cyclic durability and slow startup times are common problems for P-SOFCs and have similarly limited the development of freeze cast P-SOFCs. Tubular SOFCs (T-SOFCs) have demonstrated superior thermal cycling capability and relatively fast startup times but have been reported to have lower volumetric power density compared to P-SOFCs. The utilization of freeze casting for fabrication of tubular geometries is suggested as a solution to significantly increase the volumetric power density of T-SOFCs by enhancing gas diffusivity and triple phase boundary reactions and to be at par or better than the power densities of state-of-art P-SOFCs. This paper reports the fabrication and characterization of freeze cast tubular anode supports for SOFCs. NiO-8YSZ (nickel oxide yttria-stabilized zirconia) anode supports were fabricated using three methods: gelation casting, center pin method, and a freeze and drain method. Slurry rheology was modified for vertical dip coating, and a dual purpose freezing and drying chamber was designed and manufactured. The effects of slurry properties and process parameters were studied with respect to the resulting microstructures. The freeze and drain method was determined to be optimum for producing highly porous tubular anode supports with hierarchical, acicular or dendritic micro-pore channels. With an optimized freeze-drying cycle, drying time was reduced significantly with minimal residual moisture in the green bodies. Additionally, the electrochemical performance of the T-SOFCs with freeze cast anode was evaluated. Figure 1

Fabrication and Electrochemical Characterization of Freeze-Cast Tubular Solid Oxide Fuel Cells

The use of freeze casting is suggested as a solution to significantly increase the volumetric power density of Tubular SOFCs (T-SOFCs) by enhancing gas diffusivity and triple phase boundary reactions. This paper reports the fabrication and characterization of freeze cast tubular anode supports for SOFCs. Tubular anode supports were fabricated using three methods: gelation casting, center pin method, and a freeze and drain method. A dual purpose freezing and drying chamber was designed and manufactured. The effects of slurry properties and process parameters were studied with respect to the resulting microstructures. The freeze and drain method was determined to be optimum for producing highly porous tubular anode supports with hierarchical, acicular or dendritic micro-pore channels. With an optimized freeze-drying cycle, drying time was reduced significantly with minimal residual moisture in the green bodies. Additionally, the electrochemical performance of the T-SOFCs with freeze cast anode was evaluated.

The Influence of Anode Composition on Energy Consumption and Current Efficiency in Zinc Electrowinning

The basic method for the electrolytic zinc production is an electrowinning process based on sulfate solutions. The major problems for this industry are low current efficiency and high energy consumption leading to deterioration in the quality of cathodic zinc. The most applied approach for overcoming the mentioned problems is altering the zinc electrowinning conditions. Using Taguchi orthogonal (L25) array, five parameters (anode type, current density, sulfuric acid concentration, electrolyte temperature, and zinc concentration in electrolyte) at five different levels were selected to design and minimize the number of experiments. The experimental conditions were, zinc concentration of 50–80 g/L, acid concentration of 150–180 g/L, current density 500–1000 A/m2 and five different anodes at 30–60°C. Cast anodes of varying compositions that analyzed were Pb-Ag 0.5%, Pb-Ag 2%, Pb-Ag 0.5%-Sn 2%-Ca 1%, Pb-Ag 0.5%-Sn 2%-Bi 1%, and Pb-Ag 0.5%-Sn 2%-Sb 1%. The optimum conditions for the electrowinning process were anode composition: Pb-Ag 0.5%-Sn 2%-Sb 1%, current density: 500 A/m2, acid concentration: 165 g/L, electrolyte temperature: 50°C and Zn concentration: 80 g/L. Analysis of variance (ANOVA) showed that current density was the most important parameter. A smooth and compact structure in zinc deposits was obtained by using anode Pb-Ag 0.5%-Sn 2%-Sb 1%.

High Performance Nanofiber Electrodes for Li-Ion Batteries Using Particle/Polymer Electrospinning

The demand for rechargeable batteries with high energy and power densities has never been greater. The functionality of many portable electronic devices is limited by battery size and lifetime. Similarly, electric vehicle propulsion systems require significant improvements to satisfy consumer expectations for long drive distances and short recharge times. To meet the demands of energy-hungry consumers, new battery electrodes with high capacities and long cycle life at fast charging rates must be developed.[1-2] These requirements have motivated intense research efforts to develop next-generation Li-ion battery materials, in particular replacement designs for conventional slurry cast electrodes. One approach is the use electrospun electrodes containing engineered void spaces to enhance Li+ transport rates for high capacities at fast charge/discharge rates. Battery researchers largely focus on preparing new electrodes with high gravimetric capacity, but this metric alone is insufficient to assess a material’s applicability for consumer devices. An electrode’s volumetric capacity is another important measure for applications, such as electric vehicle propulsion, where battery space is limited. Likewise, electrodes must have high areal capacities to limit the amount of inactive components (e.g., current collectors and separators) that contribute to the overall battery size and weight. Because gravimetric, areal, and volumetric capacities are important and complementary measures of battery performance, all three should be examined to fully assess the strengths and weaknesses of new electrode materials and designs. The present work is the latest installment by Pintauro and co-workers on the use of polymer/particle electrospun nanofiber mats for fuel cell and Li-ion battery electrodes.[1-5] While previously reported electrospun battery electrodes have shown impressive performance, these materials were prepared by carbonizing polymer fiber precursors at high temperature. In particle/polymer electrospinning, there is no fiber pyrolysis; the electrospinning and post-processing are performed at room temperature to preserve the beneficial characteristics of the polymer binder that holds electrode particles together. Due to the these characteristics, high gravimetric, areal, and volumetric storage capacities can be achieved at fast charge/discharge rates through the use of thick, densely packed particle/polymer nanofiber mats. Scanning electron microscopy images of as-spun and highly compacted carbon/poly(vinylidene fluoride) (C/PVDF) nanofiber anodes are shown in Figures 1a and 1b. For comparison, a slurry cast anode of the same composition has a very dense structure with essentially no visible voids (see Figure 1c). The presence of intra- and interfiber voids in the electrospun mat is important for battery operation; electrolyte intrusion throughout these voids ensures rapid Li+ transport between the electrolyte and the active material nanoparticles in the radial fiber direction. In addition to C/PVDF anodes, particle/polymer electrospinning can be used to prepare nanofiber electrodes from new active materials and binders as they are developed. In this presentation, recent results will be presented on the fabrication and use of several electrospun particle/polymer nanofiber anodes (with titania, carbon, and silicon powders) and cathodes (with LiCoO2 powder). Charge/discharge properties of half and full cells will be shown as a function of C-rate. Electrode capacities for different fiber mat thicknesses and mat porosities will also be shown and discussed. Overall, the results will demonstrate that proper micron-scale design of electrodes can enhance Li+ transport rates and thus improve Li-ion battery performance. Acknowledgements This work was funded in part by the National Science Foundation (NSF EPS-1004083) through the TN-SCORE program under Thrust 2.

Sacrificial anode stability and polarization potential variation in a ternary Al-xZn-xMg alloy in a seawater-marine environment

In this paper, the effects of zinc (Zn) and magnesium (Mg) addition on the performance of an aluminum-based sacrificial anode in seawater were investigated using a potential measurement method. Anodic efficiency, protection efficiency, and polarized potential were the parameters used. The percentages of Zn and Mg in the anodes were varied from 2% to 8% Zn and 1% to 4% Mg. The alloys produced were tested as sacrificial anodes for the protection of mild steel in seawater at room temperature. Current efficiency as high as 88.36% was obtained in alloys containing 6% Zn and 1% Mg. The polarized potentials obtained for the coupled (steel/Al-based alloys) are as given in the Pourbaix diagrams, with steel lying within the immunity region/cathodic region and the sacrificial anodes within the anodic region. The protection offered by the sacrificial anodes to the steel after the 7th and 8th week was measured and protection efficiency values as high as 99.66% and 99.47% were achieved for the Al-6%Zn-1%Mg cast anode. The microstructures of the cast anodes comprise of intermetallic structures of hexagonal Mg3Zn2 and body-centered cubic Al2Mg3Zn3. These are probably responsible for the breakdown of the passive alumina film, thus enhancing the anode efficiency.

Comparison of corrosion and oxygen evolution behaviors between cast and rolled Pb–Ag–Nd anodes

The corrosion and oxygen evolution behaviors of cast and rolled Pb–Ag–Nd anodes were investigated by metalloscopy, environmental scanning electron microscopy, X-ray diffraction analysis, and various electrochemical measurements. The rolled anode exhibits fewer interdendritic boundaries and a dispersed distribution of Pb–Ag eutectic mixtures and Nd-rich phases in its cross-section. This feature inhibits rapid interdendritic corrosion into the metallic substrate along the interdendritic boundary network. In addition, the anodic layer formed on the rolled anode is more stable toward the electrolyte than that formed on the cast anode, reducing the corrosion of the metallic substrate during current interruption. Hence, the rolled anode has a higher corrosion resistance than the cast anode. However, the rolled anode exhibits a slightly higher anodic potential than the cast anode after 72 h of galvanostatic polarization, consistent with the larger charge transfer resistance. This larger charge transfer resistance may result from the oxygen-evolution reactive sites being blocked by the adsorption of more intermediates and oxygen species at the anodic layer/electrolyte interfaces of the rolled anode than at the interfaces of cast anode.

Redox-Stable High-Performance Thin-Film Solid Oxide Fuel Cell

An anode-supported Solid Oxide Fuel Cell (ASC) consists of a mechanically supporting, thick, and highly porous anode substrate, coated on top with thin films of a fine-structured porous anode, a dense electrolyte, and a fine-structured cathode. Both, the anode substrate and the anode are made of a cermet of nickel and yttria-stabilized zirconia (YSZ). An increase of the oxygen partial pressure at the anode side will lead to a reoxidation of the nickel and to microstructural changes. This may result in a macroscopic expansion of the anode substrate and in a complete cell failure, due to cracking of the YSZ electrolyte. In this work, a redox-stable SOFC with a thin-film sol-gel electrolyte is presented. Using tailored suspensions and polymeric sols of varying target particle size, a 1 µm thick, three layer sol-gel electrolyte is coated on top of a tape cast anode substrate and a screen printed anode by spin-coating and dip-coating techniques. With this sol-gel electrolyte a power output larger than 1.25 W/cm2 at 0.7 V and an operating temperature of 600 °C could be demonstrated. In this study, half cells (anode substrate, anode, and electrolyte) are reoxidized in excess air, in order to test the redox stability of these SOFCs. Afterwards the electrolyte is investigated ex situ using optical microscopy and SEM. No cracks are found in the sol-gel electrolyte after reoxidation for 4 hours at 600 °C and 15 minutes at 800 °C, respectively, whereas a lot of cracks are visible in a standard ASC with a 10 µm thick, screen printed electrolyte for both reoxidation conditions. This means the sol-gel electrolyte can tolerate higher degrees of oxidation (DoO) of the anode substrate than the screen printed electrolyte. The residual compressive stresses of both electrolytes are measured to about 600 MPa using XRD and are therefore not responsible for the higher stability against reoxidation of the sol-gel electrolyte. In contrast, the energy release rate has to be larger than a critical value for the creation of cracks in a thin-film on a thick substrate. Due to the fact, that the energy release rate is proportional to the thickness of the thin-film, a thinner film is more stable against cracking than a thicker film at constant tensile stresses. After reoxidation of 8 hours at 600 °C and 60 minutes at 800 °C, respectively, cracks are also found in the sol-gel electrolyte. However, the SOFC with the thin-film sol-gel electrolyte can be considered as stable against reoxidation, because the long reoxidation time of 4 hours at an operating temperature of 600 °C is unlikely to happen under real conditions.

High Areal and Volumetric Capacity Li-Ion Battery Electrodes Prepared Via Particle/Polymer Electrospinning

Despite widespread commercial success, Li-ion battery technologies require significant improvements to keep pace with increasing energy demands. The scientific community has dedicated considerable time and resources to develop superior Li-ion battery materials. Nevertheless, today’s Li-ion battery performance is limited in terms of: (i) lithium capacity (ii) rate capabilities and (iii) cycle life. Particle/polymer electrospinning is a robust platform which is utilized here to prepare high performance nanofiber electrodes for Li-ion batteries. The approach taken in the present study builds upon the recent work of Pintauro and co-workers who used particle/polymer electrospinning to fabricate hydrogen/air fuel cell electrodes [1, 2]. Potential advantages of electrospun anodes over conventional slurry cast electrodes for Li-ion batteries include: (i) a large electrode/electrolyte interfacial area for enhanced electrochemical oxidation/reduction kinetics, (ii) a controllable interfiber void volume to ensure good electrolyte infiltration into the electrode, and (iii) micron/sub-micron fibers with high nanoparticle content and short Li+ transport pathways in the radial fiber direction. A primary focus of this study was to create anodes with high areal and volumetric capacities. These metrics are often under-emphasized in the battery literature, but they are of critical importance for practical battery applications. An electrode may perform well with a low areal capacity but become less useful at higher loadings due to large internal stresses and/or transport resistances (i.e., low Li+ and/or electronic conductivity). Furthermore, a low areal capacity increases the amount of inactive components (i.e., current collectors, separators, cell housing, etc.) required for full cell construction. New electrode architectures should be prepared with areal capacities comparable to that of commercial graphite anodes to assess their practicality for consumer devices [3]. Likewise, volumetric capacity is an important parameter when battery space is limited, such as electric vehicle applications. Herein, we present two different anodes containing either titania or carbon as the active material with either poly(acrylic acid) or poly(vinylidene fluoride) as the binder (henceforth referred to as TiO2/C/PAA and C/PVDF, respectively). SEM images of these fiber anodes are shown in Figures 1a and b. A typical fiber anode composition was: 40/25/35 wt% TiO2/C/PAA or 65/35 wt% C/PVDF. The fiber diameter in the anode mats was in the range of 900 – 1,400 nm. For comparison, a C/PVDF slurry cast electrode is shown in Figure 1c. To achieve high areal capacities, particle/polymer electrospinning was used to prepare thick TiO2/C/PAA anodes, where multiple fiber mats were stacked to create an electrode of the desired areal loading. The areal capacity dependence on C-rate for electrospun titania-based anodes of three thicknesses (600µm – 1.4 mm) was evaluated. For the 1.4 mm anode, a remarkably high capacity of 2.5 mAh cm-2 was achieved at 1C (vs. 3.9 mAh cm-2 at 0.1C). These areal capacities are comparable to those of commercial graphite anodes (2.5-3.5 mAh cm-2) [3]. As a second example of an electrospun nanofiber Li-ion battery anode, C/PVDF nanofiber electrodes were prepared with a high carbon content (65 wt%) and a high fiber volume fraction (0.89). The 0.1C volumetric capacity of the nanofiber electrode was similar to that of a slurry cast anode of the same composition (98 vs. 110 mAh cm-3, respectively). At a 1C charge/discharge rate, however, the volumetric capacity of the nanofiber anode exceeded that of the slurry cast anode (70 vs. 26 mAh cm-3, respectively) due to improved Li+ transport rates. The excellent performance of the electrospun anodes is attributed to the interfiber voids which provide electrolyte intrusion throughout the electrode, a large electrode/electrolyte interface, and short Li+ transport pathways between the electrolyte and active material nanoparticles. In this presentation, additional results will be presented on the fabrication and use of titania, carbon, and other electrospun Li-ion battery anode materials. Acknowledgements This work was funded in part by the National Science Foundation (NSF EPS-1004083) through the TN-SCORE program under Thrust 2.

Struvite precipitation and phosphorus removal using magnesium sacrificial anode

Struvite precipitation using magnesium sacrificial anode as the only source of magnesium is presented. High-purity magnesium alloy cast anode was found to be very effective in recovery of high-quality struvite from water solutions and from supernatant of fermented waste activated sludge from a wastewater treatment plant that does not practice enhanced biological phosphorus removal. Struvite purity was strongly dependent on the pH and the electric current density. Optimum pH of the 24mM phosphorus and 46mM ammonia solution (1:1.9 P:N ratio) was in the broad range between 7.5 and 9.3, with struvite purity exceeding 90%. Increasing the current density resulted in elevated struvite purity. No upper limits were observed in the studied current range of 0.05–0.2A. Phosphorus removal rate was proportional to the current density and comparable for tests with water solutions and with the supernatant from fermented sludge. The highest P-removal rate achieved was 4.0mgPO4-Pcm−2h−1 at electric current density of 45Am−2. Initial substrate concentrations affected the rate of phosphorus removal. The precipitated struvite accumulated in bulk liquid with significant portions attached to the anode surface from which regular detachment occurred.

Ink‐Jet Printing: A Versatile Method for Multilayer Solid Oxide Fuel Cells Fabrication

The potential of ink‐jet printing for fabrication of components for solid oxide fuel cells has been explored. An anode interlayer, consisting of a composite of NiO and yttria‐stabilized zirconia (YSZ), and an electrolyte layer, YSZ (8 mol%), were ink‐jet printed on a tape cast anode support, 55 wt% NiO–45 wt% YSZ (8 mol%). Scanning electron microscopy of the printed layers sintered at 1400°C revealed a dense electrolyte layer measuring 10–12 μm in thickness. Single cells using these printed layers and strontium‐doped lanthanum manganate (LSM, La0.8Sr0.2MnO3)‐based pasted cathodes were assessed by DC polarization and AC complex impedance methods. The cells exhibited a stable open circuit voltage of 1.1 V around 800°C, in a hydrogen atmosphere. A maximum power density of 500 m·(W·cm)−2 was achieved at 850°C for a typical cell with the electrolyte and anode interlayer cosintered at 1400°C. A composite cathode interlayer, LSM–YSZ, and a cathode current collection layer, LSM, were also ink‐jet printed and incorporated in single cells. However, cells with all components ink‐jet printed showed decreased performance. This pointed to critical issues in the composite cathode microstructure, which is controlled by the composite ink design/formulation and printing parameters that need to be addressed.

Electrochemical Testing of Solid Oxide Fuel Cells with Sol Gel Impregnated Plasma Sprayed Electrolytes

Solid Oxide Fuel Cells (SOFCs) have been fabricated on tape cast anode substrates with plasma sprayed (PS) electrolytes and screen printed cathodes. To reduce the porosity in the PS electrolyte layers, spin coating was used to impregnate the as-sprayed electrolytes with yttria stabilized zirconia (YSZ) sols and YSZ composite sol powder suspensions. Fuel cells with electrolytes impregnated with different techniques were electrochemically tested and compared to fuel cells with no sol gel coatings to correlate the sol gel processing parameters with the resulting electrochemical performance changes. The sol gel impregnation significantly increased the open circuit voltage, slightly decreased the series resistance, and substantially decreased the polarization resistance compared to the cells with as-sprayed electrolytes. Impregnation of electrolytes offers the possibility of producing thinner electrolytes in simpler low-energy plasmas (100% nitrogen, no hydrogen) while lowering gas permeability through the electrolyte and improving fuel cell performance.

Design of 500 W Class SOFC Stack with Homogeneous Cell Performance

Our planar SOFC stacking technology uses unprofiled metallic interconnects (MIC) and thin cells of tape cast anode supported YSZ. The key element is the gas diffusion layer (GDL) between cell and MIC, which consists of so-called SOFConnex{trade mark, serif}. Using square cells with internal manifolds, 0.5 W/cm2 stack power density (800{degree sign}C) can be obtained on short stacks. However, this open design configuration limits (i) the assembly of large stacks and (ii) the durability of operation. A new design, inspired from modeling work, led to oblong-shaped cells, assembled in a closed stack casing with external air manifolding and fuel recovery manifolding, avoiding postcombustion. While stack power density remains similar, the operation at increased fuel utilization has become more stable in the 2nd design. Furthermore, a correlation of performance homogeneity during stack testing was drawn to assembly quality control. A 36-cell stack in dilute H2 at 800 {degree sign}C achieved 625 Wel (28% LHV efficiency, 0.35 W/cm2) under continuous polarisation, with all 6 clusters of 6 cells showing coincident i-V-output.

The development and applications of the anode-support system in electrochemical processes

The purpose of this article is to review the development and applications of a special type of anode, the ‘anode-support’ or ‘basket-anode’ system. This system permits the replacement in an electrochemical process of a cast anode by a metallic anode-support filled with a particulate metal to be dissolved. As raw material small pieces of primary metals, alloys or metal scrap can be used. Generally, the anode-support has the form of a basket with two or more flat parallel perforated sides. Nevertheless, an annular system made of metallic mesh or a rotary anode-support can be utilized. Titanium, stainless steel and other metals have been used to make these supports. The anode-support system has been employed on laboratory, pilot and industrial scale, for electrorefining metals and for the electrochemical generation of some insoluble products. As background, the use of basket-anodes in electroplating and electroforming processes is also reviewed.