Department Of Physics
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Item All-redox hybrid supercapacitors based on carbon modified stacked zinc cobaltite nanosheets(Royal Society of Chemistry, 2023-09-12T00:00:00) Kour, Simran; Kour, Pawanpreet; Sharma, A.L.The role of energy in the present century has increased with the fast advancement of the global economy. In this regard, hybrid supercapacitors (HSCs) as energy storage systems have become an extensive research focus worldwide. This study reports the synthesis of carbon-loaded ZnCo2O4 stacked nanosheets via an in situ hydrothermal process followed by annealing. The electrochemical response was tested in a 2-electrode system. The optimized composite exhibited a capacitance of ?527.6 F g?1 at 5 mV s?1. The symmetric SC (SSC) possessed an energy density (Ed) of ?17.3 W h kg?1 corresponding to a power density (Pd) of 2.25 kW kg?1. Two asymmetric all-redox HSCs have also been fabricated using an optimized composite material as the positive electrode. The previously synthesized MnCo2O4/AC (HSC1) and MnO2/AC (HSC2) were taken as negative electrodes. HSC1 exhibited an Ed of ?24.4 W h kg?1 corresponding to a Pd of ?0.8 kW kg?1. On the other hand, HSC2 exhibited the highest Ed of ?30.8 W h kg?1 at 2.4 kW kg?1. The real-time application of the composite is tested with the fabricated HSCs. HSC1 exhibited a capacitive retention of ?72.2% after 10 000 cycles. On the other hand, HSC2 exhibited a capacitive retention of ?73.4% after 10 000 cycles. The SSC, HSC1, and HSC2 illuminated a 39 red LED panel for ?3 min, 7 min, and 13 min, respectively. The results suggested the promising performance of all-redox HSCs. The overall results present a sustainable approach for creating hierarchical energy materials for the construction of future energy-storage systems. � 2023 The Royal Society of Chemistry.Item Blast mitigation properties of porous nano-carbon(Elsevier Ltd, 2021-11-03T00:00:00) Chinke, Shamal L.; Sandhu, Inderpal S.; Alegaonkar, Prashant S.Designing and development of a superior shock mitigation nano�material shield is an emerging armour building technology. We report, the effect of Kolsky bar simulated blast waves, onto the shock damping characteristics of the porous nano�carbon (abbreviation: PNC), synthesized by pyrolysis of biomass precursor. Measurement of stress (?)�strain (?), constitutive variables reveal the elasto�plastic behaviour suggesting moderate built�up, and accumulation of stress; independent of applied strain before reaching a yield ~50 MPa. Gruneisen fatigue parameter is estimated to be less (~0.92) over a theoretical Rayleigh limit with >80% post impact damage of porous component. The loci of dictated shock states derived from Rankine�Hugoniot formulism demonstrates the hydrodynamic interplay between pressure (P), volume (V), shock (US) and particle (UP) velocity. For PNC, Rayleigh slope is observed to be reduced, whereas, US became pressure independent over 10 GPa. Behaviour of P�UP hydrodynamic equation displays 30% variation in shock states and predicts a reduction of sound speed by a factor of ~0.25 in porous matrix. Behind the shock wavefront, matrix particles attend a max�speed of 100 km�s?1. The value of elastic limit for PNC is ~8.62 GPa as obtained by analysing the actual shock profile, with an evidence of phase transformation. Electron and force microscopy studies show reduction in an area, effectively, by 20�30%, thickness by six�fold factors with a rise in topological disorder. Hydro�physical variables inferred from Raman, scanning electron, transmission electron, and atomic force microscopy is comparatively discussed for PNC and other nano�carbons. Shock topology obtained by pressure�time signal processing shows ~30% impact of the shock onto PNC and manifested as shock echo. Details of the analysis are presented. � 2021 Elsevier B.V.Item Shock wave hydrodynamics of nano-carbons(Elsevier Ltd, 2021-02-02T00:00:00) Chinke, Shamal L.; Sandhu, Inperpal S.; Bhave, Tejashree M.; Alegaonkar, Prashant S.Dynamic deformation of nano-carbons by shock waves is an important object in technological applications as well as in basic sciences. We report, on hydrodynamic response of two types of nano-carbon systems: graphene nano-flakes (GNF) and carbon nano-spheres (CNS) by subjecting them to the Klosky bar shock test (at strain rate 102�104/s). Data of stress (?), strain (?), and strain rate (?) were obtained with time to analyse the behaviour of constitutive parameter (?�?). In elastic region GNF showed superior stress sensitivity at least by fivefold over CNS, whereas, stress accumulation ability of CNS was found to be ten times better than GNF. In plastic region both the systems were behaved quiet complexly. They comprised of various stages of deformation like inter�particle separation, micro�structure gliding, fracture, and perforation. To obtain hydrodynamic variables a few thermodynamic assumptions like matrix homogeneity, linear volume deformity, negligible temperature rise were made to set up the Lagrange�Rankine�Hugoniot model. Interplay of built�in pressure (P), particle velocity (UP), shock velocity (US), specific volume (V/VO), density (?), shock energy (E), behind and ahead of the shock wavefront led to the establishment of the equation of state for the system. Theoretical shock profile was vis-�-vis compared with the experimentally obtained shock results. Distribution of impulse pressure over the topology of the nano-carbons was examined that exhibited non-uniform shock energy dissipation pattern with peak pressure ~250 N/m2. Our calculations revealed that, almost ~65% shock energy was damped within GNF and ~89% in CNS. Details of the analysis are presented. � 2021 Elsevier B.V.