Research Information System
Thesis Type: Postgraduate
Institution Of The Thesis: Gazi Üniversitesi, Fen Bilimleri Enstitüsü, Turkey
Approval Date: 2010
Student: AYNUR DİLEK KULAK TAŞTEMÜRLÜ
Supervisor: MUZAFFER BALBAŞI
Abstract:Conducting polymer that can be distinguished from other polymers due to their high electrical conductivity comparable to that of metals. Among them, polypyrrole (PPy) has attracted more attentions as a promising candidate such as electrocatalysis, photoelectrochemical devices, ion exchangers and sensor applications in many fields, due to its relatively high conductivity, can easily be obtained and environmental stability. In this study, it is aimed to obtain have different electrical conductivities composite films for use humidity sensors. In study, containing different ratio of SiO2, poly(vinyl alcohol) - polypyrrole (PVA - PPy) composite films were synthesized by chemical oxidative polymerization method. The electrical properties of the synthesized films were investigated by impedance spectroscopy (IS), their electrical properties were compared with each other and as humidity sensor sensitivities were tested. The alternate current (ac) electrical conductivity (σac) of the films have been investigated at different temperatures (~ 30 - 80 oC) at a frequency ranging from 10 Hz to 10 MHz. Impedance spectroscopy analysis showed that the electrical conductivity of the composite films increased with increasing temperature and a high correlation of Arrhenius - type equation fits the temperature dependence but a correlation between the contribution of SiO2 and conductivity change could not be obtained. 1 % SiO2 doped, composite film was shown the highest electrical conductivity with (~ 80 ºC) 7,163x10-5 S / cm. Using the data for the experimental conductivity - temperature, conductivity were calculated activation energies (1,29 - 1,48 meV) for the composite films. Behavior of both surfaces are metalized capacitive type commercial and synthesized polymer films in humid environments have been tested at room conditions (at 25 oC, relative humidity, RH 37 - 40 %) and also in humid environment provided over the NaCl (RH ~ 68 %) and sensors time constants (τ) were calculated. This value (τ) is 18.32 sec for commercial membrane. Time constant value closest to the commercial membrane (τ = 63,56 sec) it was seen that 5 % SiO2 doped, composite film with the smallest thickness (48 μm). The results of the sensor tests show that, close to the response curve of original commercial membrane with decreasing thickness of the composite films. Effect on the response of the sensor SiO2 contribution is not understood. Experimental results show that ~ 20 μm thickness of the composite films can be used as a capacitive - type humidity sensors to decrease water diffusion distance in membrane and because of reduce the value of time constant membranes.