Naiguang Wang

Influence of aluminium and lead on activation of magnesium as anode

Mg-6%Al, Mg-5%Pb and Mg-6%Al-5%Pb (mass fraction) alloys were prepared by induction melting with the protection of argon atmosphere. Their electrochemical activations in different electrolyte solutions were investigated by galvanostatic test. The microstructures of these alloys and their corroded surfaces were studied by scanning electron microscopy, X-ray diffractometry and emission spectrum analysis. The results show that the activation of magnesium is not prominent when only aluminum or lead exists in the magnesium matrix, but the coexistence of the two elements can increase the activation. The activation mechanism of Mg-Al-Pb alloy is dissolving-reprecipitating and there is a synergistic effect between aluminium and lead: the precipitated lead oxides on the surface of the alloy can facilitate the precipitation of Al(OH)3, which can peel the Mg(OH)2 film in the form of 2Mg(OH)2•Al(OH)3 and activate the magnesium matrix.

Influence of Mg21Ga5Hg3 compound on electrochemical properties of Mg-5%Hg-5%Ga alloy

Abstract The Mg-Hg-Ga alloys are widely used in high power the seawater batteries. Mg-5%Hg-5%Ga alloy was melted and heat treatments at 573–773 K were performed for different times. The electrochemical and corrosion behaviors of the Mg-5%Hg-5%Ga alloy were studied by means of potentiodynamic, galvanostatic and electrochemical impedance spectroscopy(EIS). Scanning electron microscopy(SEM), energy dispersive spectrometry(EDS) and X-ray diffractometry(XRD) were employed to characterize the microstructures of the alloy. The results demonstrate that the best electrochemical activity occurs in the Mg-5%Hg-5%Ga alloy with homogeneously dispersed Mg 21 Ga 5 Hg 3 compound in α-Mg matrix. The most negative mean potential at 100 mA/cm 2 polarization current density can reach −1.928 V. The largest corrosion current density 19.37 mA/cm 2 of the Mg-5%Hg-5%Ga alloy appears in the Mg-5%Hg-5%Ga alloy with intergranular eutectic α-Mg and Mg 21 Ga 5 Hg 3 .

Corrosion Behavior of Magnesium Alloy AP65 in 3.5% Sodium Chloride Solution

Magnesium alloy AP65 was prepared by melting and casting. The corrosion behavior of the as-cast and solid solution (T4)-treated AP65 alloys in 3.5% sodium chloride solution was investigated by corrosion morphology observation, immersion test, and electrochemical measurements. The results show that the second phase Mg17Al12 surrounded by a lead-enriched area distributes discontinuously along the grain boundaries in the as-cast AP65 alloy. The lead-enriched areas with high activity are susceptible to be attacked during immersion test and can act as places for preferential anodic dissolution. The corrosion resistance of the as-cast AP65 alloy can be improved after T4 treatment and the T4-treated alloy suffers general corrosion.

Corrosion behavior of Mg-Al-Pb and Mg-Al-Pb-Zn-Mn alloys in 3.5% NaCl solution

Abstract Mg-6%Al-5%Pb and Mg-6%Al-5%Pb-0.55%Zn-0.22%Mn (mass fraction) alloys were prepared by induction melting with the protection of argon. The corrosion behaviors of these alloys were studied by electrochemical measurements and immersion tests. The results show that at the corrosion onset of Mg-Al-Pb anode there is an incubation period that can be shortened with 0.55%Zn and 0.22%Mn additions in the magnesium matrix. The corrosion rate of Mg-Al-Pb anode is mainly determined by the incubation period. Short incubation period always leads to high corrosion rate while long incubation period leads to low corrosion rate. The corrosion rates based on the corrosion current density by the electrochemical measurements do not agree with the measurements evaluated from the evolved hydrogen volume.

Research progress of magnesium anodes and their applications in chemical power sources

Magnesium is a promising metal used as anodes for chemical power sources. This metal could theoretically provide negative discharge potential and exhibit large capacity during the discharge process. However, when the magnesium anode is adopted for practical applications, several issues, such as the discharge products adhered to the electrode surface, the self-discharge occurring on the anode material, and the detachment of metallic particles, adversely affect its inherently good discharge performance. In this work, the types of chemical power sources using magnesium as anodes were elaborated, and the approaches to enhance its anode performance were analyzed.

Electrochemical discharge performance of the Mg–Al–Pb–Ce–Y alloy as the anode for Mg–air batteries

The electrochemical discharge performance of the Mg–Al–Pb–Ce–Y alloy in 3.5 wt% NaCl solution is investigated by using electrochemical techniques and compared with that of pure magnesium, AZ31, and Mg–Al–Pb alloys. The results indicate that Mg–Al–Pb–Ce–Y shows enhanced corrosion resistance at open circuit potential, and exhibits better performance than other samples when used as the anodes for Mg–air batteries. The voltage of the battery with the Mg–Al–Pb–Ce–Y anode is higher than those using Mg–Li anodes. The anodic efficiency of Mg–Al–Pb–Ce–Y at 10 mA cm−2 reaches 60.5 ± 0.2%, which is obviously higher than those of commercial AZ and AM magnesium alloys. This enhancement in the performance of Mg–Al–Pb–Ce–Y is owing to its modified microstructure, which reduces the self-corrosion and accelerates the spalling of oxidation products during battery discharge. Furthermore, the dissolution mechanism of Mg–Al–Pb–Ce–Y is also analyzed based on the electrochemical response and microstructure characterization.

Microstructures and electrochemical corrosion properties of Mg–Al–Pb and Mg–Al–Pb–Ce anode materials

Abstract Mg–Al–Pb alloy is a good candidate for the anode material of magnesium seawater battery. For improving the low current utilization efficiency of Mg–Al–Pb alloy, the influence of Ce on the microstructures and electrochemical corrosion properties in a 3.5% NaCl solution was investigated using scanning electron microscope and electrochemical measurements. The results indicate that Ce refines the grain structure of Mg–Al–Pb alloy. The formation of strip Al 11 Ce 3 second phase promotes the uniform distribution of Mg 17 Al 12 phase in Mg–Al–Pb–Ce alloy. The addition of cerium accelerates the discharge activity of Mg–Al–Pb alloy. Due to a large number of cathodic Al 11 Ce 3 and Mg 17 Al 12 phases, Ce promotes the micro-galvanic corrosion and leads to larger corrosion current density and hydrogen evolution rate in Mg–Al–Pb–Ce alloy than those in Mg–Al–Pb alloy. However, Mg–Al–Pb alloy expresses smaller utilization efficiency than Mg–Al–Pb–Ce alloy because of grain detachment.

Effect of pre-annealing on microstructure and compactibility of gas-atomized Al-Si alloy powders

Abstract Effect of pre-annealing treatment temperature on compactibility of gas-atomized Al-27%Si alloy powders was investigated. Microstructure and hardness of the annealed powders were characterized. Pre-annealing results in decreasing Al matrix hardness, dissolving of needle-like eutectic Si phase, precipitation and growth of supersaturated Si atoms, and spheroidisation of primary Si phase. Compactibility of the alloy powders is gradually improved with increasing the annealing temperature to 400 °C. However, it decreases when the temperature is above 400 °C owing to the existence of Si-Si phase clusters and the densely distributed Si particles. A maximum relative density of 96.1% is obtained after annealing at 400 °C for 4 h. In addition, the deviation of compactibility among the pre-annealed powders reaches a maximum at a pressure of 175 MPa. Therefore, a proper pre-annealing treatment can significantly enhance the cold compactibility of gas-atomized Al-Si alloy powders.

Effect of individual and combined additions of Al–5Ti–B, Mn and Sn on sliding wear behavior of A356 alloy

Abstract The effect of grain refiner, Mn and Sn additions on the sliding wear behavior of A356 aluminum alloys was investigated. The microstructure and worn surfaces of the studied alloys were characterized by optical microscopy (OM), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The experimental results indicate that the alloy refined by Al–5Ti–B alloy exhibits equiaxed α(Al) dendrites and performs better wear resistance compared with the alloy without the grain refiner. Moreover, the addition of Mn can change the β-Al5FeSi phase to α-Al(Mn, Fe)Si phase and reduce the possibility of crack formation, thus improving the wear resistance. Sn added to A356 aluminum alloy forms Mg2Sn precipitates after heat treatment. Therefore, the unrealizable precipitation hardening Mg2Si phase and the softening β-Sn phase can reduce the hardness of the alloy, and finally reduce the wear resistance.

Corrosion and discharge performance of Mg–9%Al–2.5%Pb alloy as anode for seawater activated battery

Abstract To obtain a new kind of Mg–Al–Pb alloy anode material with low content of Pb, the corrosion and discharge behavior of Mg–9%Al–2.5%Pb (hereafter in mass fraction) alloy were investigated by immersion tests and electrochemical techniques, and compared with those of Mg–6%Al–5%Pb alloy. The results indicate that Mg–9%Al–2.5%Pb alloy exhibits a lower self-corrosion rate and higher utilization efficiency in contrast with Mg–6%Al–5%Pb alloy because of the higher content of Al. As the result of the decrease of Pb content, the discharge activity of Mg–9%Al–2.5%Pb alloy is relatively weaker but still meets the requirement of anode. These results reveal that Mg–9%Al–2.5%Pb alloy with a low content of Pb can serve as a good candidate for the anode material used in seawater activated battery.