Browsing by Author "Tripathi, Krishna C."

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    Microwave scattering behaviour of carbon black/ molybdenum di sulphide /cobalt composite for electromagnetic interference shielding application
    (Elsevier Ltd, 2022-01-28T00:00:00) Yadav, Akshita; Tripathi, Krishna C.; Baskey, Himangshu B.; Alegaonkar, Prashant S.
    Erasing signature of an object from an enemy's radar is, tactically, disruptive move achieved by the effective electromagnetic interference (EMI) shield. We report on the microwave scattering (2�18 GHz) behaviour of the nano-composite for architecting efficient shield composed of carbon black (CB), molybdenum di sulphide (MoS2) and cobalt (Co). Nano-composite, prepared by a facile, solid state synthesis route, are characterized using infrared, x-ray diffractometry, UV�visible, energy dispersive x-ray spectroscopic techniques including scanning electron microscopy. In infrared and Rayleigh analysis, formation of -C-Mo-C, O[dbnd]S[dbnd]O, Mo�O, and Co�O phases generated asymmetric polarization at low % CB content that gets transformed into a symmetric mode due to formation of Co�O and Co�S�C radicals at high CB % to cause maximum power losses. Possible polarization mechanism is discussed. In constitutive analysis, two-fold increase in the dielectric function, the dual behaviour (Debye and Jonscher) of the ac conductivity, and the synergistic magneto-dielectric coupling factor influenced the scattering performance of the composite. Broadly, at 18% composition, the shielding effectiveness is recorded to be > 97@14 GHz with 7.7 GHz of the bandwidth and the thickness ?2.5 mm. The Dallenbach return loss is almost 75% revealing a high-performance shield design @18% CB/MoS2/Co nano-composite. � 2022 Elsevier B.V.
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    Mitigation in broad band microwave shielding properties of Ni-Co/NC composite
    (Elsevier Ltd, 2023-02-09T00:00:00) Sahoo, Suprava; Tripathi, Krishna C.; Baskey, Himangshu; Alegaonkar, Prashant S.
    It is tactically important for a high-resolution seeking tracker to generate clutter, greatly facilitated by electromagnetic interference shielding. Nickel-Cobalt /Nano?carbon (Ni-Co/NC) composites are synthesized by a simple, solid-state combustion method. The scattering performance of Ni-Co/NC composites is reported over the frequency range of 2�18 GHz with varying equal weight % of Nickel and Cobalt from (5 to 25)% and characterized using X-ray diffraction, Fourier transform-infrared spectroscopy, Energy Dispersive X-ray spectroscopy, and Scanning Electron Microscope technique. Additionally, fabricated toroidal specimens are examined for reflection loss measurements. According to analysis, the phases NiO and NiCo2O4 are formed when nickel and cobalt are added to nano?carbon. These phases subsequently diffuse throughout the nano?carbon network to produce the Ni�O stretching vibration modes, O-X-O and X-O-X (where X = Ni or Co) modes. Asymmetric polarization at low nickel?cobalt weight % changes to symmetric polarization at higher weight % in the Ni-Co/NC composites. The analysis of constitutive parameters indicated a hybrid ac conductivity behaviour (Debye- and Jonscher-like), an increase in complex permittivity and permeability, and a variation in synergetic magneto-dielectric coupling energy with frequency. Additionally, the characteristic impedance and skin resistance have been calculated. In general, the 20-wt% Ni-Co/NC composite exhibits the highest absorption at 7.28 GHz at 3.85 mm of thickness at low frequency. However, over a higher frequency range, the 5-wt% Ni-Co/NC composite exhibits a high-performance shield design, achieving ?21.05 dB reflection loss at a thickness of 5.45 mm with 2.24 GHz of effective bandwidth. � 2023 Elsevier B.V.
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    X-band Scattering Characteristics of Nickel/Nanocarbon Composites for Anti-tracking Application
    (John Wiley and Sons Inc, 2021-10-16T00:00:00) Alegaonkar, Ashwini P.; Tripathi, Krishna C.; Baskey, Himangshu B.; Pardeshi, Satish K.; Alegaonkar, Prashant S.
    Creating clutter in high resolution seeking trackers is of tactical importance which could be achieved by the electromagnetic interference (EMI) shielding. Herein, we report on X-band (8�12 GHz) scattering performance of nickel/nano-carbon-composites for architecting an effective EMI shield. Composite material is prepared by facile, one step, solid state combustion technique with variable 1�5 Ni % and characterized using x-ray diffractometry, infrared-,uv-visible, energy dispersive x-ray spectroscopic techniques, and scanning electron microscopy. Further, composite, transformed into coaxial and rectangular shaped specimens, are subjected to s-parameter and reflection loss studies, respectively, over 8�12 GHz. In analysis, incorporation of Ni, majorly, forms crystalline NiO (d[111]) and Ni2O3 (d[002]) phases dispersed within the nanocarbon network which are responsible to create asymmetric stretching bond between Ni?O?C ((Formula presented.) ?1130 cm?1). Dispersion facilitates synergistic magneto-dielectric coupling to provide long range ordering of polarization, mainly, via electronic transitions between Ni?3d to O?2p states to engage incident microwave power effectively. At highest Ni inclusion, composite showed>95 % shielding effectiveness with infinite bandwidth and>99 % return loss@8.97 GHz matching frequency. � 2021 Wiley-VCH GmbH