Can the degree of crystallinity of ball-milled Mg₂Ni intermetallic compound decide its electrochemical characteristics?

Abstract

Downloaded by [University of Otago] at 08:50 19 July 2015 2 Nanostructured Mg2Ni intermetallic compounds were synthesised by high energy ball milling.Effect of milling time on structure and surface morphology of milled powders were studied using X-ray diffraction and scanning electron microscopy. Crystallite size and degree of crystallinity were confirmed by using transmission electron microscopy and selected area electron diffraction analysis. The particle size of 20 hrs milled electrode material is 230 nm and it reduced to 40 nm when the milling time is increased to 30 hrs. Further increase in the milling time reduces the particles size drastically and starts agglomerating. In order to understand the effect of milling time on reaction rates, Differential Thermal Analysis was performed. Activation energy of the milled powders was calculated using Kissinger analysis. 30 hrs milled powder exhibit lower activation energy than others. Cyclic voltammetry, electrochemical impedance spectroscopy and charge-discharge studies were done on the prepared electrode materials. 30 hrs milled electrode material delivers maximum discharge capacity with a superior capacity retention after twenty cycles at 20 mAg 1 .

Hydrogen storage properties of magnesium based alloys Mg67Ni(32-x)Nb1Alx (x = 1, 3, and 5) by using response surface methodology

“…The A 2 B 7 -based alloy electrode exhibits a discharge capacity of 370 mAh g −1 , while the AB 5 alloy electrode demonstrates a discharge capacity of 300 mAh g −1 . The present reviews show that nanostructured particles are improving hydrogen storage capacity [18,19]. It is well established that achieving nanocrystalline structure is possible and easier through mechanical alloying than any other processing technique like melt quenching, Chemical Vapour Deposition, and Physical Vapour Deposition [20][21][22][23][24][25].…”

Mechanical alloying of Mg0.8-XTi0.2 and study the effect of adding (x = 0.2 wt%) transition metal like Sc, Zr, or Nb on their phase transitions, activation energy, and hydrogen storage properties

“…While the substitution of Zr and Nb in Mg has resulted a higher charge transfer resistance value owing to the formation of a stable oxide/hydroxide layer on the electrode surface. 42,[53][54][55] This hydroxide layer completely covers the electrode surface, thereby limiting the electrochemical kinetics of the electrode material. Consequently, the double layer capacitance (C dl ) and diffusion coefficient of electrode material decrease.…”

Off-stoichiometric Na3−3xV2+x(PO4)3/C nanocomposites as cathode materials for high-performance sodium-ion batteries prepared by high-energy ball milling

“…30,31 The ball milling process results in an intimate mixture of reactants in a short time and creates fresh surfaces with defects on the surface of the powders, resulting in the modication of the electrochemical performance of electrode material. 32,33 In addition, the ball milling process represents a low cost process with high exibility for the manufacture of nano-structured composites. Yaoqin Hu et al compared LiFePO 4 cathode synthesized by sol-gel and ball milling method and found that ball milled LiFePO 4 has higher discharge capacity during galvanostatic cycling at low to moderate discharge rates.…”