Avinandan Mandal

Graphene decorated with hexagonal shaped M-type ferrite and polyaniline wrapper: a potential candidate for electromagnetic wave absorbing and energy storage device applications

The development of promising microwave absorbing materials is a booming field of research in both the commercial and defense sectors to prevent electromagnetic pollution, and also to enrich the field of stealth technology. Supercapacitors are a symbol of clean energy storage devices. The present work attends to the preparation of hexagonal shaped magnetic M-type hexaferrite, CuFe10Al2O19 (CFA) by a facile chemical co-precipitation method, and the formation of its composites (graphene/CFA) in the presence of acid modified graphene. An in situ approach was employed for the coating of graphene with CFA. Another nanocomposite (graphene/CFA/PANI) was prepared by the wrapping of graphene/CFA with polyaniline (PANI), which was prepared through the in situ chemical oxidation polymerization of aniline. The prepared multifunctional nanocomposites showed an outstanding and improved microwave absorption property (the maximum reflection loss was −63.6 dB at a thickness of 2.5 mm with a broad absorption range) and electrochemical properties (the highest specific capacitance value was 342 F g−1), in contrast to the pristine graphene and CFA. The addition of PANI also improves the microwave absorption and specific capacitance of the nanocomposites. The formation of the multifunctional nanocomposites and their structural characteristics are discussed thoroughly with their impact on the two different fields of applications i.e. microwave absorbing and energy storage device applications individually.

Supercapacitor based on H+ and Ni2+ co-doped polyaniline–MWCNTs nanocomposite: synthesis and electrochemical characterization

In the search for promising electrode materials for supercomputer applications, we have synthesized a Ni2+ doped polyaniline, and a nanocomposite based on multiwalled carbon nanotubes (MWCNTs) and a Ni2+ doped polyaniline (PANI) in a HCl medium by an in situ oxidative polymerization. In the HCl medium and in the presence of Ni2+, PANI becomes co-doped with both H+ and Ni2+. The as synthesized materials were characterized by FTIR and Raman spectroscopy and an XRD study. Field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM) analyses confirmed the successful coating of the co-doped PANI on the MWCNT surface. The electrochemical characterizations were carried out by a three electrode system, with 1 M H2SO4 as the electrolyte. The PANI co-doped with H+ and Ni2+exhibited a specific capacitance of 311 F g−1 at a 0.5 A g−1 constant current, which was higher than that of the solely H+ doped PANI, which exhibited a specific capacitance of 265 F g−1 under the same conditions. The incorporation of MWCNTs to the co-doped PANI influenced the specific capacitance to increase to 781 F g−1 at the same constant current density, with a 92% retention of initial specific capacitance over 700 galvanostatic cycles.

Synthesis and Microwave Absorbing Properties of Cu-Doped Nickel Zinc Ferrite/Pb(Zr0.52Ti0.48)O3 Nanocomposites

Nanocomposites based on Cu-doped nickel zinc ferrite and lead zirconium titanate exhibited significant microwave absorbing properties in the X-band (8.2–12.4 GHz) region. Coprecipitation and homogeneous precipitation methods were utilized to synthesize Cu-doped nickel zinc ferrite (Cu0.2Ni0.4Zn0.4Fe2O4) and lead zirconium titanate (Pb(Zr0.52Ti0.48)O3) nanoparticles, respectively. To develop nanocomposites, dispersion of these nanoparticles into epoxy resin (LY665) polymeric matrix was carried out by using mechanical stirrer. Phase analyses of the nanoparticles were done by X-ray diffraction (XRD). Moreover, morphological characterization was done by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Energy dispersive X-ray spectroscopy (EDS) confirmed the chemical constituents present in the nanocomposites. Complex relative permittivity and complex relative permeability values of the nanocomposites were measured in different microwave frequencies in the X-band (8.2–12.4 GHz) region by employing vector network analyzer (model PNA E8364B), and return loss (dB) values were calculated to identify the microwave absorbing performance of the present nanocomposites. Brilliant microwave absorbing properties have been achieved by the nanocomposites with the minimum return loss of −49.53 dB at 8.44 GHz when sample thickness was 3 mm. For the present nanocomposites, mainly dielectric loss was responsible for loss mechanism.