Browsing by Author "Alegaonkar, Ashwini P."

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    Microwave scattering parameters of ferro-nanocarbon composites for tracking range countermeasures
    (Royal Society of Chemistry, 2021-12-18T00:00:00) Alegaonkar, Ashwini P.; Baskey, Himangshu B.; Alegaonkar, Prashant S.
    In the strategic sector, frequently, the radar signatures in the microwave frequency region are cluttered, which can be overcome by designing and developing an effective electromagnetic interference (EMI) shield. Herein, we report the analysis of the s-parameter performance of ferro-nanocarbon (FNC) composites tested over the frequency region of 8-12 GHz (X-band). The FNC composite was prepared via a simple, single-pot, solid-state sublimation route with different contents of iron (1-4%). The fabricated material was characterised using X-ray diffractometry, scanning electron microscopy, vibrating sample magnetometry and several spectroscopic techniques such as infrared, UV-visible, and energy dispersive X-ray analysis. S-parameter and reflection loss studies were performed by transforming the composite material into a coaxial- and rectangular-shaped specimen, respectively. In the analysis, the inclusion of iron resulted in the formation of crystalline Fe2O3 (d[110]) and Fe3O4 (d[220]) phases, which were self-dispersed in the nanocarbon structure. The inclusion of iron was responsible for creating an asymmetric bond molecular environment in C-O-Fe, resulting in synergistic magneto-dielectric effects in terms of long-range polarization ordering mainly through the transitions between the O-2p and Fe-3d states to engage the incoming microwave field effectively. This composite showed a good performance of >98% shielding effectiveness with an infinite bandwidth and >99% return loss at a matching frequency of 9.01 GHz. This journal is � The Royal Society of Chemistry.
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    Reduced graphene oxide doped tellurium nanotubes for high performance supercapacitor
    (Frontiers Media S.A., 2022-10-20T00:00:00) Rani, Pinki; Alegaonkar, Ashwini P.; Biswas, Rathindranath; Jewariya, Yogesh; Kanta Haldar, Krishna; Alegaonkar, Prashant S.
    Supercapacitors have been achieving great interest in energy storage systems for the past couple of decades. Such devices with superior performance, mainly, depending on the material architecture of the electrodes. We report on the preparation of Tellurium nanotubes (Te-tubes diameter ?100�nm and length ?700�nm), with variable doping of conducting network reduced graphene oxide (rGO) to fabricate high-performance electrode characteristics of rGO @ Te. The prepared material was characterized using XRD, FTIR, FESEM, and Raman spectroscopy techniques, including Brunauer-Emmett-Teller, Barrett-Joyner-Halenda measurements. FTIR study revealed that 15% rGO @ Te has a wide C-O vibration band at ? 1,100�1,300�cm?1, over other compositions. FESEM study shows the Te-tubes dispersion in rGO layers. The EDX study revealed that 15% of the composition has an optimistic concentration of C and O elements. In other compositions, either at lower/higher rGO concentration, an uneven count of C and O is observed. These support efficient charge dynamics to achieve superior ultra-capacitor characteristics, thereby achieving specific capacitance Csp 170 + F/g @ 10�mV/s in a symmetric configuration. The reported values are thirty times higher than pristine Te-tubes (?5�F/g). This finding suggests that rGO @ Te is a promising candidate for supercapacitor. Copyright � 2022 Rani, Alegaonkar, Biswas, Jewariya, Kanta Haldar and Alegaonkar.
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    Tellurium nanostructures for optoelectronic applications
    (Springer Science and Business Media Deutschland GmbH, 2022-03-29T00:00:00) Rani, Pinki; Alegaonkar, Ashwini P.; Mahapatra, Santosh K.; Alegaonkar, Prashant S.
    We report on fabrication of tellurium nanostructures (TN) that demonstrated promising applications in optoelectronics. Initially, TN were synthesized using a simple, one-step, room temperature, wet-chemical technique. During synthesis, the effect of number of parameters such as precursor concentration, its content, solvent ratios, their pH and reaction time has been investigated at a temperature ~ 120��C. The obtained product was examined by UV�visible, IR spectroscopy, X-ray diffractometry, electron microscopy and energy-dispersive X-ray spectroscopic characterization techniques. Analysis revealed that TN have profound impact on the structure�property relationship through active and passive participation of Mo catalyst. During its initial growth stages, Te and O bonding gets influenced by Mo to form Mo�O�Te�O and Te�Mo�Te moieties, typically, at 6�h. This has implication onto the structural phase transformation of TN from Te-tube (TT) to Te-flake (TF) and then to TT again. Possible transformation mechanism is explained. Structurally, TN had hexagonal quasi-crystalline atomic arrangement with morphologically thin, transparent, bunched and close-caped TT characteristics having diameter 50�100�nm and length 0.8�2.1��m, whereas TF is found to be thin, geometrically squared with area ~ 7 to 10 �m2. On their implementation for optoelectronic assessments, over the wavelength range 0.3�2.1��m (power density ~ 100 mW/cm2), they showed peculiar luminescent and dark I�V responses. Relevant photocarrier dynamics has been revealed. TT, typically, showed 160% quantum efficiency, whereas TF ~ 40% is useful for optoelectronic devices. Details are presented. Graphical abstract: Fabrication and optoelectronic assessments of tellurium nanostructure that showed time-dependent structural phase transformation from tube to flake to tube. [Figure not available: see fulltext.] � 2022, The Author(s), under exclusive licence to Springer-Verlag GmbH, DE part of Springer Nature.
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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