Articles written in Bulletin of Materials Science
Volume 37 Issue 3 May 2014 pp 705-711
In order to improve the cycling performance of LiMn2O4 based cathode materials, we have synthesized a new composition, LiNi0.4M0.1Mn1.5O4 (𝑀 = Al, Bi), by the sol–gel method. The formation of solid solutions is confirmed by structural characterization using TG/DTA, XRD, FT–IR, EPR, SEM and EPR. A.c.-impedance (Nyquist plot) showed a high frequency semicircle and a sloping line in the low-frequency region. The semicircle is ascribed to the Li-ion migration through the interface from the surface layer of the particles to the electrolyte. Cyclic voltammogram (between 3.5 and 4.9 V) for these materials using CR2032 coin-type cell shows two pairs of redox peaks corresponding to two-step reversible intercalation process, wherein Li-ions occupy two different tetragonal 8a sites in spinel Li𝑥Mn2O4 (𝑥 < 1) lattice. The galvanostatic charge/discharge curves for 𝑀 = Al (77 mAh g-1) showed reasonably good capacity retention than that of 𝑀 = Bi (11 mAh g-1) at the end of 17th cycle.
Volume 38 Issue 1 February 2015 pp 169-172
A conducting cotton fabric with a resistance of <1.5 k𝛺 cm-2 was obtained by dip coating of multiwalled carbon nanotubes (MWCNTs) dispersed in a surfactant, sodium dodecyl sulphate (SDS). The dip coating was repeated up to 20 times to increase the loading of MWCNT as observed from optical absorption spectra (𝜆max = 442 nm). The field emission scanning electron microscopy (FE-SEM) image of coated fabric at different magnifications shows micro-fibril structure. Energy-dispersive X-ray analysis (EDXA) spectra show peaks for carbon and other constituent elements of SDS, Na and S. In order to improve the functionality of loaded MWCNT, the coated fabric was treated with 5% HNO3 for 3 h. For such a sample, the resistance decreased significantly to 1.5 k𝛺 cm-2, whereas it is 2.0 and 2.5 k𝛺 cm-2 for untreated and KOH-treated sample. This is in corroboration with 𝐼−𝑉 characteristics, and is attributed to increased loading of MWCNT through hydrogen bonding with glycosidic group present in cotton (cellulose) fibres. The series capacitance of the MWCNT-coated fabric is about 40 𝜇F cm-2, which is found to decrease with the increase in frequency, close to zero at about 20 kHz. A capacitor formed by placing two MWCNT-coated fabrics between etched PCB plates (terminal contacts) shows the charging capacity of about 1 F.
Volume 44, 2021
Continuous Article Publishing mode
Prof. Subi Jacob George — Jawaharlal Nehru Centre for Advanced Scientific Research, Jakkur, Bengaluru
Chemical Sciences 2020
Prof. Surajit Dhara — School of Physics, University of Hyderabad, Hyderabad
Physical Sciences 2020
Click here for Editorial Note on CAP Mode