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Doctoral Thesis
DOI
10.11606/T.76.1994.tde-15042014-092035
Document
Author
Full name
Helder Nunes da Cunha
Institute/School/College
Knowledge Area
Date of Defense
Published
São Carlos, 1994
Supervisor
Committee
Faria, Roberto Mendonça (President)
Andrade, Adnei Melges de
Ferreira, Guilherme Fontes Leal
Giacometti, José Alberto
Livi, Rogerio
Title in Portuguese
Condutividade induzida por radiação-x nas fases ferroelétrica e paraelétrica em copoli(fluoreto de vinilideno/tri-fluoretileno)
Keywords in Portuguese
Condutividade induzida
Polímeros ferroelétricos
Transporte dispersivo
Abstract in Portuguese
O comportamento da condutividade induzida por radiação-X (RIC) em copolímeros P(VDF/TrFE) de razões molares 60/40 e 70/30 em suas fases ferroelétrica (temperatura ambiente) e paraelétrica (acima de 110°C), foi estudado para diferentes condições ambientais. Foi observado que a RIC depende fortemente sobre a conformação molecular do polímero. Variaram-se parâmetros experimentais como campo elétrico aplicado, taxa de dose, atmosfera ambiente e, principalmente a temperatura. Medidas auxiliares como correntes termoestimuladas, calorimetria diferencial, espectroscopias infravermelho, ressonância eletrônica paramagnética, difração de raios-X, etc..., deram contribuições no sentido de entender modificações estruturais e morfológicas do material devido à radiação. Para análise dos resultados da condutividade induzida (RIC), foi usado o modelo de transporte em meios dispersivos desenvolvido por Arkhipov e colaboradores. Por meio de ajustes teórico-experimentais obtivemos parâmetros importantes do material como, a mobilidade dos portadores gerados, o coeficiente de recombinação, o parâmetro dispersivo, bem como a energia de geração de pares.
Title in English
Radiation-induced conductivity in ferroelectric and paraelectric phases of poly(vinylidenefluoride-co-trifluoroethylene)
Keywords in English
Dispersive transport
Ferrolectric polymers
Induced conductivity
Abstract in English
The behavior of the radiation induced conductivity (RIC) by X-rays in P(VDF/TrFE) copolymers of 70:30 and 60:40 molar ratios, in their ferro and paraelectric phases, were studied in different environments. It was observed that the RIC depends strongly on the molecular conformation of the polymer. For the experiments several parameters were varied as the external applied field, the dose rate, the atmosphere and mainly the temperature. Auxiliar measurements as thermal stimulated currents, differential scanning calorimetry, EPR and IR spectroscopy, X-ray diffraction, etc..., were used in the sense to supply additional information about morphological and structural variations of the material due to the irradiation. For a complete analysis of the radiation induced conductivity results a dispersive transport model developed by Arkhipov et al was used. From the theoretical experimental fitting we obtained important parameters of the material: carrier mobility, recombination coefficient, dispersive parameter Q, as well as the pair-generation energy.
 
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HelderNunesD.pdf (6.36 Mbytes)
Publishing Date
2014-04-16
 
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