Browsing by Subject "Anodes"
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Item Plasma diagnostics on high current ignitrons(Texas Tech University, 1989-08) Burke, John E.This report describes the results of diagnostic techniques utilized to study the plasma of a specially built demountable ignitron switch. Three anode geometries, flat (standard), inverted cup, and inverted cup with slits, were installed to study the effect of anode geometry on the plasma. Diagnostics included voltage and current monitoring, high speed photography via a Dynafax rotating camera, interferometry via a Mach-Zehnder interferometer and argon laser, and spectroscopy via high speed photography with line mercury filters. All measurements were taken with the ignitron operating in the crowbarred configuration. A 2.56 mF, 10 kV capacitor bank and 1 /xH test stand holding the forward (series) ignitron and demountable (crowbar) ignitron comprise the test circuit. All three anodes were utilized in the photographic analysis; the flat anode was utilized in the interferometric analysis; and the flat and slit-cup anodes were utilized in the spectroscopic analysis.Item Tin-based nanocomposite alloy anodes for lithium-ion batteries(2014-05) Leibowitz, Joshua Abel; Manthiram, ArumugamLithium-alloying anode materials have attracted much attention as an alternative to carbon due to their high theoretical gravimetric capacities (e.g. Li4.4Si: 4200 mAh g-1, Li4.4Sn: 990 mAh g-1, and Li3Sb: 660 mAh g-1). An additional benefit of lithium alloying metals is that some of the react at a higher potentials vs. Li/Li+ than carbon, which can mitigate safety issues caused by solid-electrolyte interface layer formation and lithium plating. One of the most promising lithium -alloying anode materials that are being pursued are Sn-based materials due to their high capacity and tap density. This thesis investigates the synthesis and characterization of Sn-based lithium-ion battery anodes. SnSb-TiC-C and FeSn2-TiC nanocomposite alloy anodes for lithium-ion batteries have been synthesized by a mechanochemical process involving high-energy mechanical milling of Ti/Sn, Ti/M (M = Fe or Sb), and C. Characterization of the nanocomposites formed with x-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) reveals that these alloys are composed of crystalline nanoparticles of FeSn2 and SnSb dispersed in a matrix of TiC and carbon. The SnSb-TiC-C alloy shows an initial gravimetric capacity of 653 mAh g-1 (1384 mAh cm-3), an initial coulombic efficiency of 85%, and a tap density of 1.8 g cm-3. The FeSn2-TiC alloy shows an initial gravimetric capacity of 510 mAh g-1 (1073 mAh cm-3), an initial coulombic efficiency of 71%, and a tap density of 2.1 g cm-3. The TiC-C buffer matrix in the nanocomposite alloy anodes accommodates the large volume change occurring during the charge-discharge process and leads to good cyclability compared to pure FeSn2 and SnSb anodes.