Chaoqun Peng

Influence of Ga and Hg on microstructure and electrochemical corrosion behavior of Mg alloy anode materials

The effects of Hg and Ga on the electrochemical corrosion behavior of Mg-5%Hg (molar fraction) alloys were investigated by the measurement of polarization curves and galvanostatic test. The microstructure of the alloys and the corroded surface of the specimens were investigated by scanning electron microscopy, X-ray diffractometry and emission spectrum analysis. It can be concluded that the addition of 1%Ga (molar fraction) reduces corrosion current density from 26.98 mA/cm2 to 2.34 mA/cm2; while the addition of 1%Hg (molar fraction) increases corrosion current density. The addition of Ga and Hg both promotes the electrochemical activity of the alloys and the influence of Ga is more effective than Hg. Mg-5%Hg-1%Ga alloy has the best electrochemical activity, showing mean potential of -1.992 V. The activation mechanism of the magnesium alloy produced by Hg and Ga was put forward. Magnesium atoms are dissolved in liquid Hg and Ga to form amalgam and undergo severe oxidation at the amalgam/electrolyte interface.

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.

Microstructure and properties of Al/Sip composites for thermal management applications

Aluminum matrix composite reinforced with high amount of Si particle is an advanced electronic packaging material used in thermal management. In this work, Al/Sip composites with different Si contents were prepared by rapid solidification and hot pressing. Fine and homogeneous microstructures with defect-free were achieved, and no detrimental reaction was detected. The typical thermo-physical properties such as the thermal conductivity and coefficient of thermal expansion (CTE) of the Al/Sip composites were acceptable as electronic packaging material for semiconductor devices. The CTE increased gradually with the temperature. Additionally, the mechanical properties of the composites were measured. The technological performance (workability, platability, and laser weldability) of the composites were also evaluated.

Transitional Suspensions Containing Thermosensitive Dispersant for Three-Dimensional Printing.

Tailoring the rheology of suspensions is an essential and persistent issue form many applications, especially three-dimensional (3D) printing. Colloidal suspensions of ceramic powder (Al2O3) dispersed by a special thermosensitive dispersant (poly(acrylic acid)-poly(N-isopropylacrylamide), PAA-PNIPAM) were designed, which underwent a remarkable fluid-gel transition in response to thermal stimulus due to the phase transition of the graft chains (-PNIPAM). 3D periodic structures with a fine size of 100 μm were assembled by 3D printing.

Microstructural evolutions of Cu(Ni)/AuSn/Ni joints during reflow

Abstract Interfacial reactions of the Ni/AuSn/Ni and Cu/AuSn/Ni joints are experimentally studied at 330 °C for various reflow times. The microstructures and mechanical properties of the as-solidified solder joints are examined. The as-solidified solder matrix of Ni/AuSn/Ni presents a typical eutectic ζ-(Au,Ni)5Sn+δ-(Au,Ni)Sn lamellar microstructure after reflow at 330 °C for 30 s. After reflow for 60 s, a thin and flat (Ni,Au)3Sn2 intermetallic compound (IMC) layer is formed, and some needle-like (Ni,Au)3Sn2 phases grow from the IMC layer into the solder matrix. On the other hand, a cellular-type ζ(Cu) layer is found at the upper AuSn/Cu interface in the Cu/AuSn/Ni joint after reflow for 30 s, and a (Ni,Au,Cu)3Sn2 IMC layer is also formed at the lower AuSn/Ni interface. For both joints the IMC layer grows significantly with the increase of reflow time, but the growth rate of (Ni,Au,Cu)3Sn2 IMC in the Cu/AuSn/Ni joint is smaller than that of the (Ni,Au)3Sn2 layer in the Ni/AuSn/Ni joint. The comparisons of the shear strength and fracture surface between the Ni/AuSn/Ni and Cu/AuSn/Ni joints suggest that the coupling effect of the Cu/AuSn/Ni sandwich joint is helpful to prevent the excessive growth of (Ni,Au)3Sn2, which in turn enhances the mechanical reliability of the solder joint.

Microstructure evolution of spray-formed hypereutectic Al-Si alloys in semisolid reheating process

Abstract The Al-27%Si alloy was prepared by the spray forming process, and its microstructure evolution during the semisolid reheating process was investigated. The results show that, the primary Si phase coarsens during the reheating process and the coarsening rate increases with the increase of reheating temperature. The eutectic phase is produced in the molten region when quenched in the cold water. The microstructure evolution in the semisolid state can be divided into three stages. The remarkable characteristic of the first stage is only a solid-state phase transformation process. However, the region around the α(Al) matrix gradually melts in the second stage. The primary Si in the liquid phase coarsens obviously, and the eutectic phase is produced in the molten region when the specimens are quenched in cold water. In the last stage, the same thing as that in the second stage happens except that all the α(Al) matrixes are melted.