Faculty Publications
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Item Optimization of deposition conditions for development of high corrosion resistant Zn-Fe multilayer coatings(2011) Yogesha, S.; Hegde, A.C.Composition modulated multilayer alloy (CMMA) coating of Zn-Fe was developed galvanostatically on mild steel through single bath technique (SBT), using thiamine hydrochloride as additive. Electrodeposits with different coating matrices were developed, using square current pulses. Potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) methods were used to assess the corrosion performance of the coatings. The cyclic cathode current densities (CCCDs) and number of layers were optimized, for highest corrosion resistance. Experimental results showed that CMMA Zn-Fe coating, developed at 2.0-4.0 A/dm2, having 300 layers is ?30 times higher corrosion resistant than corresponding monolithic alloy of same thickness. The corrosion resistance increased with number of layers up to a certain number of layers; and then decreased. The better corrosion resistance was attributed to the dielectric barrier at the interface, evidenced by dielectric spectroscopy. The formation of multilayer and corrosion mechanism was analyzed using scanning electron microscopy (SEM). © 2011 Elsevier B.V. All rights reserved.Item Effects of the Reynolds number on two-dimensional dielectrophoretic motions of a pair of particles under a uniform electric field(Korean Society of Mechanical Engineers, 2016) Kang, S.; Mannoor, M.; Maniyeri, R.This paper presents two-dimensional direct numerical simulations to explore the effect of the Reynolds number on the Dielectrophoretic (DEP) motion of a pair of freely suspended particles in an unbounded viscous fluid under an external uniform electric field. Accordingly, the electric potential is obtained by solving the Maxwell’s equation with a great sudden change in the electric conductivity at the particle-fluid interface and then the Maxwell stress tensor is integrated to determine the DEP force exerted on each particle. The fluid flow and particle movement, on the other hand, are predicted by solving the continuity and Navier-Stokes equations together with the kinetic equations. Numerical simulations are carried out using a finite volume approach, composed of a sharp interface method for the electric potential and a direct-forcing immersed-boundary method for the fluid flow. Through the simulations, it is found that both particles with the same sign of the conductivity revolve and eventually align themselves in a line with the electric field. With different signs, to the contrary, they revolve in the reverse way and eventually become lined up at a right angle with the electric field. The DEP motion also depends significantly on the Reynolds number defined based on the external electric field for all the combinations of the conductivity signs. When the Reynolds number is approximately below Recr ? 0.1, the DEP motion becomes independent of the Reynolds number and thus can be exactly predicted by the no-inertia solver that neglects all the inertial and convective effects. With increasing Reynolds number above the critical number, on the other hand, the particles trace larger trajectories and thus take longer time during their revolution to the eventual in-line alignment. © 2016, The Korean Society of Mechanical Engineers and Springer-Verlag Berlin Heidelberg.Item 11.39 fJ/conversion-step 780 kS/s 8 bit switched capacitor-based area and energyefficient successive approximation register ADC in 90 nm complementary metal-oxide- semiconductor(Institution of Engineering and Technology journals@theiet.org, 2018) Narasimaiah, J.D.; Laxminidhi, T.; Bhat, M.S.In this study, a design technique for low-energy consumption and area-efficient successive approximation register analogue-to-digital converter (ADC) is presented. Digital-to-analogue conversion equivalent voltage is acquired utilising passive sharing of charge between two unit capacitors and integration of the shared charge onto an input sample-and-hold capacitor, via a switched capacitor integrator circuit. The architecture is less parasitic sensitive and low noise, yielding an area and energyefficient ADC. To demonstrate the efficacy of the proposed technique, a ±350 mV 8 bit 0.78 MS/s ADC is designed in a 90 nm complementary metal-oxide-semiconductor process. The ADC core has a small area footprint of 0.00145 mm2 and has a figure-of-merit of 11.39 fJ/conv-step. © 2018, The Institution of Engineering and Technology.Item PMMA-LZO Composite Dielectric Film with an Improved Energy Storage Density(Springer New York LLC barbara.b.bertram@gsk.com, 2019) Kishor Kumar, M.J.; Kalathi, J.T.Energy storage materials in modern electronic devices and renewable energy systems are inevitable. The incorporation of inorganic fillers into the polymer matrix is a promising option for the advancement of storage materials with high energy density. The agglomeration of inorganic fillers in the polymer matrix and phase separation remain the main obstacles to efficient applications of the composites for energy storage. Here, the primary attention was given to achieve a uniform distribution of high-k LZO (Lanthanum Zirconium Oxide) filler into a PMMA (Polymethylmethacrylate) matrix to enhance the dielectric constant and energy storage density of PMMA while keeping dielectric loss at minimum. We prepared PMMA-LZO composite films with variable LZO content by ultrasound-assisted mixing followed by spin coating the solution on ITO (Indium tin oxide) coated glass. The effect of LZO content on dielectric properties of the LZO-PMMA films was studied. Dielectric constant (k) of PMMA was found to be increased from 3.1 to 15.3 at 15 vol.% LZO loading with a dielectric loss of 0.0582. However, 10 vol.% LZO loaded PMMA showed an improved dielectric constant of 13.4 while the dielectric loss remained the same as that of the neat PMMA. The LZO-PMMA films with 10 vol.% and 15 vol.% of LZO loading exhibited maximum energy density of 5.94 J cm?3 and 6.53 J cm?3, respectively. Overall, the 10 vol.% LZO loading was found to be optimum to achieve a stable film with improved dielectric properties. This work provides a viable approach for the development of flexible, high-energy density materials with a minimum dielectric loss. © 2019, The Minerals, Metals & Materials Society.Item Investigation on the dielectric performance of PVDF-HFP/LZO composites(Elsevier Ltd, 2020) M J, K.K.; Kalathi, J.T.The energy storage density of the film capacitor is crucial for optoelectronic devices. Among various dielectrics, polyvinylidene-fluoride-co-hexafluoropropylene (PVDF-HFP) copolymer is widely preferred due to its inherent high dielectric constant and breakdown strength. However, the low energy storage density and high dielectric loss (tan ?) of PVDF-HFP remains challenging in the present scenario. In this work, we demonstrated how to improve the dielectric constant and energy density of PVDF-HFP with low dielectric losses by formulating PVDF-HFP/Lanthanum Zirconium Oxide (LZO) composite ink at low temperature. We performed the computational modeling of the thin-film capacitor, consisting of PVDF-HFP/LZO as a dielectric layer, to find the optimum LZO content for achieving a high energy density. A computational model of the film capacitor and dielectric shielding was built with PVDF-HFP/LZO composites having a different LZO content to understand its effect on the electric field distribution, polarization, and energy storage density. We compared the dielectric properties of the PVDF-HFP/LZO thin-film capacitor predicted by simulations with the experimental values measured by impedance analysis. The optimum LZO content in PVDF-HFP was determined as 15 vol% to achieve a high energy storage density of 15.8 J/cm3 at 545 MV/m breakdown strength with low dielectric losses. Dielectric constant and energy storage density of the PVDF-HFP/LZO15 composite film were nearly doubled compared to that of neat PVDF-HFP by keeping dielectric losses low. © 2020 Elsevier B.V.Item Experimental studies on mechanical and dielectric behavior of Glycerol filled Silicone rubber composites(IOP Publishing Ltd, 2021) Mathias, K.A.; Hiremath, H.; Kulkarni, S.M.In this study, Silicone rubber composites are prepared with Glycerol filler in three different volume fractions. The samples developed are subjected to mechanical and dielectric testing. The tensile strength increases first and later decreases with Glycerol loading whereas compression strength decreases with Glycerol loading. Modulus of elasticity in tension and compression both decreases with the increase of Glycerol loading. Dielectric permittivity, dissipation factor and conductivity are increases with the increase of Glycerol loading. The Silicone Rubber (SR) composite with 15% volume of Glycerol filler shown a maximum reduction in modulus of elasticity of 29% (in tension) and 16.8% (in compression), and maximum improvement in the dielectric permittivity of 112% compared to neat silicone rubber. The reduction in modulus of elasticity with an increase in dielectric permittivity with an increase in Glycerol loading suggests that this material is a potential candidate for materials to be used in soft dielectric sensors and actuator applications. © 2021 IOP Publishing LtdItem Study on low-frequency dielectric behavior of the carbon black/polymer nanocomposite(Springer, 2021) Hiremath, H.; Mathias, K.A.; Sondar, P.R.; Shrishail, M.H.; Kulkarni, S.M.Recently, polymer-based dielectric materials have become one of the key materials to play an essential role in clean energy production, energy transformation, and energy storage applications. The end usage is the energy storage capability because it is a trade-off between dielectric permittivity, dielectric loss, and dissipation factor. Hence, it is of prime importance to study the dielectric properties of polymer materials by adding filler material at a low-frequency range. In the present study, polydimethylsiloxane/carbon black nanocomposites are prepared using the solution cast method. The dielectric properties, such as dielectric constant, dielectric loss, and dissipation factors due to the concentration of filler particles and low-frequency effect on the nanocomposites, are examined. Also, different empirical models are used to estimate the dielectric permittivity of polymer nanocomposites. The low-frequency range of 100 Hz to 1 MHz and the effect of varying volume fractions of carbon black show a significant change in the dielectric properties. It is found that the nanocomposites have a higher dielectric permittivity than the base polymer material. It is also observed that an increase in filler concentration increases the dielectric permittivity, which is confirmed with an empirical model. © 2021, The Author(s).Item Analytical modelling of ultra-small group delay variation of ultra-broadband RF power amplifier using NSGA-II algorithm(John Wiley and Sons Ltd, 2024) Kumar, K.; Kumar, S.; Kumar Kanaujia, B.K.This paper proposes a ± 9.4 ps ultra-small group delay (GD) variation of fully integrated 65 nm complementary metal oxide semiconductor (CMOS) power amplifier (PA) over 6.5–17 GHz broadband for wireless application. The proposed CMOS PA is realised by using broadband stage, RLC inter-stage and power stage topologies. The non-dominated sorting genetic algorithm (NSGA-II) is employed for PA parameter optimisation to ensure a small GD variation of ±9.4 ps over broadband with an excellent small signal gain flatness of 23.65 ± 1.85 for 6.5–17 GHz. The small GD variation of ±9.4 ps and ± 11.05 ps are attained under two cases of DC supply voltages of 2.4/1.2 V and 1.2/1.2 V, respectively. To the best of author's knowledge, the achieved GD variations are lowest among all CMOS PAs as reported so far. In addition, an analytical modelling of GD is derived to validating the minimum GD variation using zero-pole compensation. With supply voltages of 2.4/1.2 V at 6.5 GHz, the large signal power gain, Psat and OP1dB are 26 dB, 19.3 dBm and 17.94 dBm, respectively, while peak power added efficiency (PAE) is 38.196%. At reduced supply voltages of 1.2/1.2 V, the PA achieves maximum power gain of 17.7 dB and peak PAE of 35% at 6.5 GHz. The CMOS PA occupies an area of 0.206 mm2. © 2023 John Wiley & Sons Ltd.