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| Author(s): |
Cassio de Campos Tambelli
Total Authors: 1
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| Document type: | Master's Dissertation |
| Press: | São Carlos. |
| Institution: | Universidade de São Paulo (USP). Instituto de Física de São Carlos (IFSC/BT) |
| Defense date: | 2000-06-02 |
| Examining board members: |
Jose Pedro Donoso Gonzalez;
Agnieszka Joanna Pawlicka Maule;
Ernesto Chaves Pereira de Souza
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| Advisor: | Jose Pedro Donoso Gonzalez |
| Abstract | |
Polymeric electrolytes based on poly(ethylene oxide) (PEO) and alkaline salts has been subject of scientific and technological interest due to its potential applications as solid electrolytes in electrochemical devices. The ionic conductivity of such electrolytes results from the fact that the macromolecule acts as a solvent for the salt, leaving it partially dissociated. Nuclear magnetic resonance (NMR) techniques were used to characterize the 1H and 7Li nuclear spin dynamics in order to investigate the transport properties associated to the ionic conduction mechanisms of polymeric composites based on PEO8:LiC1O4 and particles of α and γ-alumina. NMR lineshapes and spin-lattice relaxation were measured at 36 MHz (1 H) and 155.4 MHz (7Li) as a function of temperature in the range of 170-350 K. Physical characterization of the particles was realized by measuring the particle size distribution, porosity and superficial area. Differential scanning calorimetry (DSC) and ac electric conductivity of the composites were measured. 1H NMR results show that the polymeric chains of the composite prepared with 20 wt.% of α-alumina has a greater mobility if compared with the unfilled polymeric material. No changes in linewidth and relaxation rates were observed following the addition of 5 wt.% of α or γ-alumina. The 7Li mobility increases when 20 wt.% of &3945;-alumina is added to the starting polymeric material. On the other hand, addition of 20 wt.% of γ-alumina do not alter the relaxation rates but produces a small change in linewidth. Results are discussed in accordance with the Lewis acid-base interaction (AU) | |