Discharge Behavior of Water-Activated Magnesium Battery

Water-activated magnesium batteries possess several favorable attributes for energy storage and lighting sources. In this chapter, a portable-sized magnesium battery which consisted of MnO2 cathodes and magnesium alloy anodes, being activated by drops of water, was investigated. The anode and cathode potential as well as their electrochemical impedance under a constant current load was monitored to evaluate the effect of water content, cell stacking, and discharging cycles. It was revealed that the discharge behavior was initially controlled by the depletion of water, followed by the cease of cathode reaction and the accumulation of Mg(OH)2 at anode. The problem of low anode efficiency caused by stacking cells was analyzed, and its countermeasure was proposed. Several approaches to improve the battery performance were also presented

Direction Dependence of Compressive Properties of Mg Processed by Directional Solidification

Pure Mg consisting of elongated grains was fabricated by the directional solidification process, and its compressive properties were investigated at room temperature, 473 and 773 K under the conditions where the angle between the long axis direction of the elongated grains and the compression direction was 0, 45 and 90 degree. At room temperature, the specimen at the angle of 45 degree was fractured prior to " ¼ 0:3, although the specimens at the angles of 0 and 90 degree were not fractured even at " ¼ 0:3. In addition, the yield stress at the angle of 45 degree was higher than those at the angles of 0 and 90 degree. The (0002) basal planes were distributed at a tilt of 30-50 degree to the solidification direction. This was responsible for the higher yield stress at the angle of 45 degree. Also, the yield stress at the angle of 0 degree was lower than that at the angle of 90 degree. The lower yield stress at the angle of 0 degree was attributed to twinning. At 473 K, the yield stress at the angle of 45 degree decreased significantly. The large decrease in yield stress at the angle of 45 degree resulted from grain boundary sliding. At 773 K, the yield stresses were almost the same, irrespectively of the loading direction. Thus, compressive properties of the directionally solidified Mg were affected by the loading direction

SIGMA: Scala Internal Domain-Specific Languages for Model Manipulations

International audienceModel manipulation environments automate model operations such as model consistency checking and model transformation. A number of external model manipulation Domain-Specific Languages (DSL) have been proposed, in particular for the Eclipse Modeling Framework (EMF). While their higher levels of abstraction result in gains in expressiveness over general-purpose languages, their limitations in versatility, performance, and tool support together with the need to learn new languages may significantly contribute to accidental complexities. In this paper, we present Sigma, a family of internal DSLs embedded in Scala for EMF model consistency checking, model-to-model and model-to-text transformations. It combines the benefits of external model manipulation DSLs with general-purpose programming taking full advantage of Scala versatility, performance and tool support. The DSLs are compared to the state-of-the-art Epsilon languages in non-trivial model manipulation tasks that resulted in 20% to 70% reduction in code size and significantly better performance

Effect of Reduction in Thickness and Rolling Conditions on Mechanical Properties and Microstructure of Rolled Mg-8Al-1Zn-1Ca Alloy

A cast Mg-8Al-1Zn-1Ca magnesium alloy was multipass hot rolled at different sample and roll temperatures. The effect of the rolling conditions and reduction in thickness on the microstructure and mechanical properties was investigated. The optimal combination of the ultimate tensile strength, 351 MPa, yield strength, 304 MPa, and ductility, 12.2%, was obtained with the 3 mm thick Mg-8Al-1Zn-1Ca rolled sheet, which was produced with a roll temperature of 80°C and sample temperature of 430°C. This rolling process resulted in the formation of a bimodal structure in the α-Mg matrix, which consequently led to good ductility and high strength, exclusively by the hot rolling process. The 3 mm thick rolled sheet exhibited fine (mean grain size of 2.7 μm) and coarse grain regions (mean grain size of 13.6 μm) with area fractions of 29% and 71%, respectively. In summary, the balance between the strength and ductility was enhanced by the grain refinement of the α-Mg matrix and by controlling the frequency and orientation of the grains

Nanoporous surface fabricated on metal sheets by alloying/dealloying technique

An alloying/dealloying technique including stacking rolling was used to fabricate nanoporous architecture on Au sheet surface. Under appropriate conditions, a nanoporous surface layer with a thickness of 150–250 nm was generated. The extended immersion of the sample in the electrolyte (HNO3) increased the ligament size of the nanoporous architecture up to 41 nm. Cross-sectional observations suggested that the nanoporous surface layer can be seamlessly bonded to the bulk substrate Au. True surface area, which was measured by an electrochemical method, decreased as ligament size increased by the extended immersion. The relationship among surface area, ligament size and volume shrinkage was investigated

An atomistic study of Y segregation at a {101¯1}–{101¯2} double twin in Mg

Segregation at a triple junction of grain boundaries has not been explained much because the structure of a triple junction is very complicated. The present paper describes Monte Carlo simulations by which Y segregation was investigated at a triple junction of a {101¯1}–{101¯2} double twin in Mg. Y atoms segregated at the extension sites in the {101¯1} and {101¯2} twin boundaries. However, they were not necessarily more segregated at the triple junction of the double twin, although the free volumes at the extension sites of the triple junction were larger on average than those of the other boundaries. Thus, the Y segregation behavior at the triple junction cannot be explained only by the free volume. The anisotropic factor of the atomic Voronoi polyhedron was developed to explain the Y segregation behavior at the triple junction. In addition, the shortest interatomic distance and coordination number affected Y segregation at the triple junction. Also, segregation at the triple junction strongly depended on the Y concentration, which resulted from variations in the local atomic configuration. Thus, the Y segregation behavior at the triple junction was complicated, in contrast to those at twin boundaries, even when the size effect was predominant

Deformation Characteristics of Recycled AZ91 Mg Alloy Containing Oxide Contaminants

Deformation characteristics of a recycled AZ91 Mg alloy, obtained from machined chips by solid state recycling, were investigated by conducting tensile tests between room temperature and 773K in the strain rate range of 3:3 102–3:3 104 s1. Tensile properties of the recycled specimen were compared with those of a reference specimen. The elongation to failure of the recycled specimen was lower than that of the reference specimen, except at room temperature and 753K with 3:3 104 s1. The recycled specimen contained oxide contaminants whose size was 2 mm. Such oxide contaminants were responsible for the reduction in elongation to failure. The cavity formation due to the oxide contaminants was analyzed using existing theoretical models, and experimental results were compared with analytical results. [doi:10.2320/matertrans.MC200770