Microstructure and Discharge Performance of Aluminum Al 6061 Alloy as Anode for Electrolyte Activated Battery

Electrolyte activated battery finds its important use during natural disaster emergencies, such as floods and typhoons. Nevertheless, high corrosion rate will deteriorate the discharge performance of the battery and it is influenced by the type of electrolyte and discharge current. In this study, the corrosion and discharge performance of a commercial Al 6061 aluminum alloy as an anode are investigated at different discharge currents (0.001, 0.01, and 1 mA) and in different electrolytes, namely salt water, urea, and distilled water. Scanning electron microscopy results show that electrode in salt water has the most serious corrosion, followed by that of in urea and in distilled water. These electrodeelectrolyte combinations are further investigated with potentiodynamic polarization, galvanostatic discharge, and electrochemical impedance spectroscopy (EIS) to understand their discharge potential, discharge behavior, and corrosion mechanism. Among all combinations, aluminum in water is found to have the highest discharge performance with discharge potentials ranging from 716 to 744 mV, regardless of discharge current

Data analysis of the long-term residual effect of cathodic protection on reinforced concrete structures

The application of impressed current cathodic protection (CP) is a well-established technology for the corrosion protection of reinforced concrete structures situated in marine environments. While the protective benefits of cathodic protection are well known, the lasting effects following the discontinuation of CP current are not entirely understood. This paper presents research findings on the residual protective effect which is known to occur following long durations of impressed current cathodic protection. The residual effect was replicated in university laboratories using reinforced concrete test blocks and accelerated CP testing methods. The experimental results depicted a clear improvement in the electrochemical state of the reinforcing steel with a shift of 150 to 300 mV to more positive values following CP application. The research also involved analysis of monitoring data from six in-service cathodic protection systems which were operating in Australia for nearly two decades. The behaviour of the steel potential readings was analysed and the results of the combined research confirmed that the protection provided by cathodic protection systems does not actually cease when the CP current is switched off. Rather, the embedded steel undergoes a significant and sustained shift to more positive values and this phenomenon is documented and discussed in this paper

Effect of electrolyte on electrochemical characteristics of MmNi3.55Co0.72Al0.3Mn0.43 alloy electrode for hydrogen storage

A series of experiments have been performed to investigate the effects of three electrolytes of different compositions (EO, EA and EM) on the electrochemical characteristics of MmNi3.55Co0.72Al0.3Mn0.43 hydrogen storage alloy electrode. Electrolytes EA and EM were obtained by adding appropriate amounts of Al2(SO4)3 and MnSO4 to the original electrolyte EO (6 M KOH + 1 wt% LiOH), respectively. Electrode activation, maximum capacity, cycle life, self-discharge and high-rate discharge characteristics have been studied. It was found that a maximum capacity of about 260 mA h/g has been obtained for the alloy electrodes in all these electrolytes after 5-7 cycles of charging/discharging. The alloy electrodes have a good durability in electrolytes EA and EM, especially after 175 cycles. Using the capacity retention as an indication of self-discharge resistance, almost identical degree of capacity retention (82% after 4 days and 45% after 16 days) has been observed at 298 K, regardless of the electrolytes used. When tested at higher temperature, however, a higher capacity retention (46% after 3 days) at 333 K has been observed for electrodes in electrolyte EA, and about 32% for electrodes in both electrolytes EO and EM. As to high-rate discharge behavior of the results of high-rate discharge tests indicated that about 50% of discharge efficiencies were obtained in the three electrolytes at 333 K by continuous-model high-rate discharge method, at a discharge rate of 7C, and 22% in 298 K. The alloy electrode in electrolyte EM has the best durability, in which about 50% of discharge efficiency at DC = 9C was obtained by step-model high-rate discharge method at 333 K, which was even higher than that at 298 K. © 2008.Link_to_subscribed_fulltex

Electrochemical characteristics of La-Ni-Al thin films

AB5 based hydrogen storage thin films (LaNi4.25Al0.75), deposited on Cu substrate by dc magnetron sputtering, have been investigated in this paper. X-ray diffraction (XRD) revealed that the microstructure of the film was in crystal form. SEM, AFM and FIB analyses proved that on the surface there were many pores of approximately 15-40 nm in diameter of random size. The cross section of the film revealed that it was rather dense and defect-free, with a uniform thickness of about 4.2 μm. Electrochemical properties of the films were measured by simulated battery tests. The single layer LaNi4.25Al0.75 film undergoes a longer activation period than typical AB5 alloys in bulk and the maximum discharge capacity of the film was about 220 mAh/g. Two electrochemical behaviour (distinct to the bulk materials) were observed for the film electrode in which there was an apparent increase in intermediate potential for each discharge process, as well as a local increase of discharge potential during its activation period. © 2007 Elsevier B.V. All rights reserved.Link_to_subscribed_fulltex

Structural stability of single-layered LaNi4.25Al0.75 film and its electrochemical hydrogen-storage properties

AB 5-based hydrogen storage thin films (LaNi4.25Al0.75), deposited on Cu substrate by dc magnetron sputtering were investigated in this study. X-ray diffraction (XRD) revealed that the microstructure of the layer was in crystal form. SEM and AFM analyses proved that the film appeared to be rather rough with numerous randomly sized pores of approximately 15-40 in nm diameter. Structural stability of the film was examined by the combined analyses of DSC, XRD, and SEM, which indicated that this film maintained its structural stability below 500 K or so, and a network structure was ob served on the film after being heated at 700 K for 30 min. Electrochemical hydrogen-storage properties of the films were investigated by simulated battery tests. It was found that single-layered LaNi4.25Al0.75 film exhibited electrochemical hydrogen-storage properties similar to typical AB5 alloys in bulk, and the maximum discharge capacity of the film was about 220 mAh/g. After 20 charge/discharge cycles, small needle-shaped aluminium oxide was formed on some fractions of the film surface.Link_to_subscribed_fulltex

Self-discharge behavior of LaNi 5-based hydrogen storage electrodes in different electrolytes

Nickel-metal hydride (Ni-MH) batteries using hydrogen storage alloys as negative electrode materials have been developed and commercialized because of their high energy density, high rate capability and long cycle life, without causing environmental pollution (Song et al. J Alloys Comp 298:254, 2000; Jang et al. J Alloys Comp 268:290, 1998). However, the self-discharge rate is relatively higher than that of the Ni-Cd batteries, which would certainly be disadvantageous in practical applications. The capacity loss of a battery during storage is often related to self-discharge in the cells. Self-discharge takes place from a highly charged state of a cell to a lower state of charge (SOC) and is typically caused by the highly oxidizing or reducing characteristic of one or both of the electrodes in the cell. This self-discharge behavior may be affected by various factors such as gases, impurities, temperature, type of alloy electrode, electrolytes, or charge/discharge methods. The loss of capacity can be permanent or recoverable, depending on the nature of the mechanism (chemical or electrochemical) and aging condition. In this paper, the effects of electrolyte composition and temperature on self-discharge behavior of LaNi 5-based hydrogen storage alloy electrodes for Ni-MH batteries have been investigated. It was found that both reversible and irreversible capacity loss of MH electrode tested at 333 K were higher than that at 298 K. When tested at 298 K and 333 K, reversible capacity loss was mainly affected by the electrolyte, while the irreversible capacity loss was not affected. The dissolution of Al from the electrode can be reduced more effectively in an electrolyte with Al addition, compared with that in normal electrolyte. This resulted in a lower reversible capacity loss for the electrode exposed in the Al 3+-rich electrolyte. SEM analysis has shown that some needle shape and hexagonal corrosion products were formed on the surface of the alloy electrodes, especially after storage at high temperature. © 2008 Springer-Verlag.Link_to_subscribed_fulltex

Microstructure and discharge performance of aluminum Al 6061 alloy as anode for electrolyte activated battery

Electrolyte activated battery finds its important use during natural disaster emergencies, such as floods and typhoons. Nevertheless, high corrosion rate will deteriorate the discharge performance of the battery and it is influenced by the type of electrolyte and discharge current. In this study, the corrosion and discharge performance of a commercial Al 6061 aluminum alloy as an anode are investigated at different discharge currents (0.001, 0.01, and 1 mA) and in different electrolytes, namely salt water, urea, and distilled water. Scanning electron microscopy results show that electrode in salt water has the most serious corrosion, followed by that of in urea and in distilled water. These electrodeelectrolyte combinations are further investigated with potentiodynamic polarization, galvanostatic discharge, and electrochemical impedance spectroscopy (EIS) to understand their discharge potential, discharge behavior, and corrosion mechanism. Among all combinations, aluminum in water is found to have the highest discharge performance with discharge potentials ranging from 716 to 744 mV, regardless of discharge current

Effects of Oxide Fragments on Microstructure and Mechanical Properties of AA6061 Aluminum Alloy Tube Fabricated by Thermomechanical Consolidation of Machining Chips

An AA6061 aluminum alloy tube was fabricated by compacting machining chips via thermomechanical consolidation, including hot pressing and hot extrusion. The microstructure evolution and formation of oxide particles were investigated in correlation to tensile mechanical properties. It was found that fine Al/Mg oxide particles were formed due to the fracture of oxide layers on the chips and the reaction between Mg and Al2O3 during hot extrusion. The oxide particles inhibited the growth of recrystallized α-Al grains, leading to the formation of a microstructure consisting of coarse elongated grains with sizes of 420 μm and fine equiaxed grains with sizes of 10 μm. After T6 heat treatment, a microstructure with finer grains (grain sizes: 34 μm) formed due to further recrystallization induced by residual strain. The tensile mechanical properties testing results indicated that a good combination of strength (296 MPa) and ductility (7.6%) was achieved in the T6 heat treated samples, which were likely attributed to the high-quality inter-chip bonding, as well as the fine oxide particles which were small enough that further crack nucleation and growth around them were inhibited during tensile deformation. For the purpose of comparison, the microstructure and mechanical properties of the as-extruded and T6 heat treated samples produced by hot extrusion of the cast ingot of AA6061 aluminum alloy were also investigated. The lower tensile strength of solid-state recycled tube sample might be associated with the consumption of Mg atoms by the oxidation reaction, leading to the lower density of β″ precipitates in precipitation strengthening

Effects of Oxide Fragments on Microstructure and Mechanical Properties of AA6061 Aluminum Alloy Tube Fabricated by Thermomechanical Consolidation of Machining Chips

An AA6061 aluminum alloy tube was fabricated by compacting machining chips via thermomechanical consolidation, including hot pressing and hot extrusion. The microstructure evolution and formation of oxide particles were investigated in correlation to tensile mechanical properties. It was found that fine Al/Mg oxide particles were formed due to the fracture of oxide layers on the chips and the reaction between Mg and Al2O3 during hot extrusion. The oxide particles inhibited the growth of recrystallized α-Al grains, leading to the formation of a microstructure consisting of coarse elongated grains with sizes of 420 μm and fine equiaxed grains with sizes of 10 μm. After T6 heat treatment, a microstructure with finer grains (grain sizes: 34 μm) formed due to further recrystallization induced by residual strain. The tensile mechanical properties testing results indicated that a good combination of strength (296 MPa) and ductility (7.6%) was achieved in the T6 heat treated samples, which were likely attributed to the high-quality inter-chip bonding, as well as the fine oxide particles which were small enough that further crack nucleation and growth around them were inhibited during tensile deformation. For the purpose of comparison, the microstructure and mechanical properties of the as-extruded and T6 heat treated samples produced by hot extrusion of the cast ingot of AA6061 aluminum alloy were also investigated. The lower tensile strength of solid-state recycled tube sample might be associated with the consumption of Mg atoms by the oxidation reaction, leading to the lower density of β″ precipitates in precipitation strengthening