Thermal stability and dielectric relaxation behavior of in situ prepared poly(vinyl alcohol) (PVA)-reduced graphene oxid
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ORIGINAL CONTRIBUTION
Thermal stability and dielectric relaxation behavior of in situ prepared poly(vinyl alcohol) (PVA)-reduced graphene oxide (RGO) composites Heena Wadhwa 1 & Geeta Kandhol 2 & Uday P. Deshpande 3 & Suman Mahendia 2
&
Shyam Kumar 2
Received: 10 December 2019 / Revised: 22 July 2020 / Accepted: 3 August 2020 # Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract Poly(vinyl alcohol) (PVA)-reduced graphene oxide (RGO) composite films have been prepared via in situ reduction of graphene oxide (GO) inside PVA matrix. In order to study microstructure and morphology of prepared PVA-RGO composite films, transmission electron microscopy (TEM), Fourier-transform infrared (FTIR) spectroscopy, UV-Visible absorption spectroscopy, X-ray diffraction (XRD) technique, and Raman spectroscopy were utilized. Thermogravimetric analysis (TGA) depicts the increase in thermal stability of PVA with increasing loading of RGO. The dielectric properties of composites were explored in frequency range 100 Hz–2.5 MHz which depicts increase in dielectric permittivity and ac conductivity of composite films with increasing RGO loading. The dielectric relaxation behavior and dispersion parameters of composite films were analyzed using Cole-Cole plots using a MATLAB program based on the Havrilak-Negami (HN) model. Keywords PVA-RGO composites . Thermogravimetric analysis . Dielectric relaxation . Cole-Cole plots . Havrilak-Negami (HN) model
Introduction From past few decades, polymer-based composites have been in locus of intense research due to versatile properties offered by polymers like flexibility, good mechanical strength, and tuneable electrical and optical properties [1–3]. Polymer composites with large dielectric constant are in high demand for development of charge storage devices and flexible electronics. For these purposes, large variety of polymers have been tested viz. poly(vinyl alcohol) (PVA), polyamide, poly(methyl methacrylate) (PMMA), and poly(vinylpyrrolidone) (PVP) [4–9] for making such composites. Also, several methods have been explored to tune their dielectric permittivity like ion irradiation and implantation; among these, making
* Suman Mahendia [email protected]; [email protected] 1
Department of Physics, Goverment PG College, Hisar 125001, India
2
Department of Physics, Kurukshetra University, Kurukshetra, Haryana 136119, India
3
UGC-DAE Consortium for Scientific Research, Indore, Madhya Pradesh 452017, India
of composites by addition of high dielectric constant material viz. ceramics and ferroelectric metal oxides as dopant is the most common approach [10–14]. However, this strategy usually requires high loading concentration of dopant which results in unwanted increase of rigidity, brittleness, poor transparency, etc. of resultant polymer composites. Sometimes, increased dielectric constant of polymer composites meet with large loss tangent values which are highly undesirable [15–17]. To overcome these problems, conductive fillers like metal nanoparticles and carbon-based
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