• M Revanasiddappa

      Articles written in Bulletin of Materials Science

    • Synthesis, characterization and low frequency a.c. conduction of polyaniline/fly ash composites

      S C Raghavendra Syed Khasim M Revanasiddappa M V N Ambika Prasad A B Kulkarni

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      in situ polymerization of aniline was carried out in the presence of fly ash (FA) to synthesize polyaniline/fly ash (PANI/FA) composites. The PANI/FA composites have been synthesized with various compositions (15, 20, 30 and 40 wt%) of FA in PANI. The composites, thus synthesized have been characterized by infrared spectroscopy and X-ray diffraction. The morphology of these samples was studied by scanning electron microscopy. Further the a.c. conductivity of these composites have been investigated in the frequency range 102–106 Hz. The presence of polarons and bipolarons are made responsible for frequency dependence of a.c. conductivity in these composites. The Cole–Cole plots indicate clear shift in the distribution of relaxation times as the wt% of FA in PANI changes. These composites show almost symmetric semicircles of Cole–Cole plots indicating the Debye-type relaxation in their polarization response.

    • Synthesis, characterization and magnetic properties of polyaniline/𝛾-Fe2O3 composites

      Syed Khasim S C Raghavendra M Revanasiddappa K C Sajjan Mohana Lakshmi Muhammad Faisal

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      Conducting polyaniline/𝛾-Fe2O3 (PANI/FE) composites have been synthesized using an in situ deposition technique by placing fine-graded 𝛾-Fe2O3 in a polymerization mixture of aniline. The composites are characterized by using scanning electron microscopy (SEM), X-ray diffraction (XRD) and infrared (IR) spectroscopy. The electrical properties such as d.c. and a.c. conductivities are studied by sandwitching the pellets of these composites between the silver electrodes. It is observed that the conductivity increases up to a composition of 20 wt.% of 𝛾-Fe2O3 in polyaniline and decreases thereafter. The initial increase in conductivity is attributed to the extended chain length of polyaniline, where polarons possess sufficient energy to hop between favourable sites. Beyond 20 wt.% of 𝛾-Fe2O3 in polyaniline, the blocking of charge carrier hop occurs, reducing conductivity values. The magnetic properties such as hysteresis characteristics and normalized a.c. susceptibility are also measured, which show a strong dependence on content of 𝛾-Fe2O3 in polyaniline. Because of superparamagnetic behaviour of these composites, they may find extensive technological applications, especially for absorbing and shielding applications in microwave frequencies.

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