Pradeep Sambyal

Encapsulation of γ-Fe2O3 decorated reduced graphene oxide in polyaniline core–shell tubes as an exceptional tracker for electromagnetic environmental pollution

The ultimate goal of the development of a new material γ-Fe2O3 decorated reduced graphene oxide (rGO)–polyaniline (PANI) core–shell tubes has been done for absorbing electromagnetic interference (EMI) pollution. Herein, we report on the synthesis and characterization of PANI tubes consisting of rGO decorated with iron oxide nanoparticles (RF). The intercalated RF was synthesized by thermal decomposition of ferric acetyl acetonate in a reducing atmosphere. Furthermore, RF was encapsulated through oxidative polymerization of aniline in the presence of β-naphthalene sulphonic acid which results in RF–PANI core–shell morphology. Scanning electron microscopy results confirm the formation of tubular core–shell morphology having 5–15 μm length and 1–5 μm diameter. The presence of rGO–γ-Fe2O3 in PANI core enhances the interfacial polarization and the effective anisotropy energy of the composite which contributes to more scattering and leads to high shielding effectiveness (SET ∼ 51 dB) at a critical thickness of 2.5 mm. Additionally, the effective complex permeability and permittivity parameters of the composites have been evaluated from the experimental scattering parameters (S11 & S21) using theoretical calculations given in Nicholson–Ross and Weir algorithms.

Tailored polyaniline/barium strontium titanate/expanded graphite multiphase composite for efficient radar absorption

The present paper reports the synthesis of a high-performance microwave absorbing material using a simple, cost-effective and scalable method by encapsulating barium strontium titanate (BST) and expanded graphite (EG) in a polyaniline (PANI) matrix. One of the formulations (higher content of BST) shows shielding effectiveness due to absorption of more than 50 dB (>99.9999% attenuation) with minimum reflection loss (≤1 dB) in the Ku-band (12.4–18 GHz) frequency range. Another formulation (higher content of EG) shows a total shielding effectiveness of more than 81 dB with a reflection loss of 10 dB. In order to probe the relationship between the observed shielding response and the electromagnetic attributes, dielectric and permeability parameters have been calculated from the measured scattering parameters (S11, S22, S12, S21) using the Nicolson–Ross–Weir algorithm. The synthesised formulations were characterized thoroughly using XRD, FTIR, TGA, UV, Raman spectroscopy, SEM and HRTEM.

New insight into the shape-controlled synthesis and microwave shielding properties of iron oxide covered with reduced graphene oxide

We proposed various approaches for the shape-controlled synthesis of iron oxide-RGO composites to evaluate the effect of different morphologies on their microwave shielding properties. The nature of various ferrite structures (flakes, cubes and rods) covered by reduced graphene oxide multilayers has been investigated using X-ray diffraction, Raman spectroscopy, FT-IR, scanning electron microscopy, high-resolution transmission electron microscopy and X-ray photoelectron spectroscopic techniques. The electromagnetic interference (EMI) shielding effectiveness of iron oxide of different shapes coated with reduced graphene oxide was investigated in the Ku band frequency range (12.4–18 GHz). The rod shaped iron oxide covered with reduced graphene oxide sheets demonstrates the highest shielding effectiveness value of ∼33.30 dB (>99.9% attenuation) as compared to flake and cube shaped iron oxides due to the combined effect of magnetic losses (hysteresis, eddy current loss and effective anisotropy) and dielectric losses (space charge polarization, interfacial polarization, surface defects, multiple scattering, etc.). These innovative proposed structures and their obtained EMI shielding results deliver a new insight into the morphology dependent nature of iron oxides covered with RGO nanosheets and create new opportunities for next generation EMI materials.