Synthesis and electrochemical characterization of 4 V LiRXMn2−XO4 spinels for rechargeable lithium batteries

Lithium ion cells have attracted the researchers ever since the first commercialization of Li//LiCoO2 cells in Japan. However, the high cost and relatively low availability of cobalt has promoted the search for inexpensive and widely available manganate materials. LiMn2O4 is one of these materials which is being investigated extensively. However, LiMn2O4 shows fading of capacity during cycling involving mainly the Jahn–Teller Mn3C ion. In the present work, LiRXMn2−XO4 (RDCo, Ni, Fe, Ti) spinel compounds have been synthesized using low and high temperature methods. These materials were structurally evaluated using XRD. The prepared materials were electrochemically investigated using cyclic voltammetry and galvanostatic cycling techniques. The best performing material was assembled in a coin cell of type 2032 and charged at 500mAup to 4.4V. The cells were cycled at 1mAcurrent drain using 1MLiClO4/PC as an electrolyte. The results indicate that Ti doped spinel shows promising results. Electrical characteristics of these cells are presented in this paper

Low temperature ductile shear failure of Zr41.2Ti13.8Ni10Cu12.5Be22.5 and Cu50Zr35Ti8Hf5Ni2 bulk amorphous alloys

Fractographic study of ductile shear failure under uniaxial compression of rod-like samples of the Zr41.2Ti13.8Ni10Cu12.5Be22.5 and Cu50Zr35Ti8Hf5Ni2 bulk amorphous alloys at temperatures of 300 and 77 K is presented. Although the mechanisms of shear deformation and fracture appeared the same as in conventional amorphous alloys prepared in form of thin ribbons, some new fractographic features are observed, owing to the bulk character of the samples and also due to the large supercooled liquid region of these alloys

Magnetic Force Microscopy Characterization of Magnetic Nanowires and Nanotubes

The fundamental properties of 2D arrays of magnetic nanowires and nanotubes (NWs and NTs) have been well described theoretically, but real systems are subject to certain flaws and imperfections which strongly affect the mechanism and dynamics of magnetization reversal. Therefore, before exploiting the vast potential of magnetic NWs and NTs, there is a need to investigate the materials parameters as well as the field dependent magnetic properties in real systems. Amongst the various issues at stake for a comprehensive understanding of these arrays is the influence of long-range dipolar interactions because these interactions strongly influence the magnetization reversal and thus the switching field distributions (SFD) which plays a significant role for information storage. Particularly, the width of the SFD is important since smaller values of this parameter leads to less recording errors and it is also a measure of the quality of the recording media. Consequently, the understanding and evaluation of the distinct parameters influencing the interactions and the intrinsic SFD in the magnetization reversal process of such arrays is critical for the development of magnetic recording media. It is shown that the intrinsic SFD mostly originates from nonuniformities of the geometrical parameters such as the aspect ratio and the shape of the magnetic nanostructures. This chapter provides an overview of the MFMcharacterization studies undertaken to understand the reversal behavior of 2D arrays of magnetic NWs and NTs at the nanoscale and the motivations to investigate isolated single domain NWs and NTs