Binod Kumar

Polymer-ceramic composite electrolytes

A polymer-ceramic composite electrolyte is provided which may be formed into a thin film having a room temperature conductivity of from 10-5 S cm-1 to 10-3 S cm-1. In one embodiment, the composite electrolyte comprises from about 30 to 60% by weight poly(ethylene oxide), from about 10 to 20% by weight lithium tetrafluoroborate, and from about 25 to 60% by weight lithium nitride. The film is preferably produced by mixing and grinding the components, then placing the ground mixture in a die and compacting the mixture to form a disc which is then flattened. The resulting film is annealed to ensure high conductivity at room temperature.

Evaluation of doped polyethylene oxide as solid electrolyte

This report presents results of an investigation on preparation and characterization of polyethylene oxide (PEO) and lithium tetrafluoroborate (LiBF4) complexes for application as solid electrolytes in polymer batteries. AC conductivity and permittivity (dielectric constant) as a function of frequency, temperature, and concentration of lithium tetrafluoroborate (LiBF4) in polyethylene oxide (PEO) films were measured with a TA Instruments DEA 2970, Dielectric Analyzer. Differential Scanning Calorimetry (DSC) was used to trace changes of the morphology of the polymeric medium. Thermogravimetry (TG)/derivative thermogravimetry (DTG) were used to follow the decomposition of components and define the maximum temperature limits for these measurements. Infrared Spectroscopy monitored structural evolution as the O:Li ratio in the polymer complex was varied. Thin films of a complex (O:Li = 8) were used to assemble Li/Polymer/Li Cell for electrochemical characterization. The study showed that the relationship of dopant concentration to electrical properties is rather complex. Degree of ion-pairing, dissociation of ions on dilution, changes in the morphology of the polymeric medium, and variations in viscosity and its consequence on ion mobility were considered to explain the data. An optimum in room conductivity occurred in a complex with O:Li ratio of 8.

Pulse Electric Fields for EPD of Thermal Barrier Coatings

Conventional electrophoretic deposition is being combined with pulse electric fields to deposit yttria stabilized zirconia from ethanol based suspensions onto bondcoated turbine alloys for thermal barrier coatings. The addition of the pulse electric fields to the electrophoretic process has demonstrated the capability to decrease the coating roughness, minimize hydrolysis, and decrease coating edge effects commonly encountered in electrokinetic and electrochemical deposition processes. Subsequent to the electrophoretic deposition process the green body coatings were subjected to a combined binder burnout and sintering process for further coating densification. The coatings have been qualified in terms of surface roughness as well as microstructure and experiments have been performed to show that the pulse EPD process can deposit TBC materials onto turbine components.

Time-resolved luminescence and decay characteristics of Gd3+ in fluoroarsenate and fluorophosphate glasses☆

Light excitation of Gd3+ in fluoroarsenate and fluorophosphate glasses to the 6Ij and 6DJ multiplets leads to luminescence, originating from the 6P72 and 6P52 levels, with an evolution time dependent on the nature of the glass (1.3−1.4 ms and 1.1−1.2 ms respectively) and a lifetime (9.2 ms) independent of the host lattice. The luminescence rise time, which relates to the relaxation time of the 6IJ and 6DJ multiplets, leads to values of k1 + kr for the 6IJ multiplet equal to 2.7 × 103s−1 (fluoroarsenate) and 3.9 × 103s−1 (fluorophosphate). Slightly shorter luminescence rise times were observed following excitation of Gd3+ to the 6DJ multiplet. Direct excitation of Gd3+ to the 6PJ levels leads to luminescence with no measurable rise time and with a lifetime equal to 9.2 ms.