Faculty Publications
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Item Performance Analysis of Novel Graphene Process Low-Noise Amplifier with Multi-stage Stagger-Tuned Approach over D-band(Springer, 2024) Nandini, P.; Naik, D.N.; Gorre, P.; Gupta, M.P.; Kumar, S.; Al-Shidaifat, A.; Song, H.This work reports an ultra-low noise, multi-stage stagger-tuned low-noise amplifier (MS-ST-LNA) over the D-band performance and achieves a best trade-off between noise, bandwidth, and gain parameters. The ultra-low-noise is achieved in three ways: First, the high-gain 3-stage stagger tuned amplifier (STA) realizes a 3X gain compared to the conventional single-stage amplifier, which sets a low floor noise. Second, the stagger-tuned amplifier achieves 1.6 times lower noise than the traditional single-stage amplifier. Finally, the stagger tune realizes a high-order transfer function, which mitigates the high-frequency noise. The full LNA is implemented and fabricated using a commercial nano-manufacturing 9-nm graphene film FET on a silicon wafer using a 0.065-?m commercial process, occupying an area of 0.21 mm2. The proposed design achieves an optimum performance: a maximum measured gain of 20.5 dB and a minimum noise figure (NF) of 4.2 dB over 123.7 to 162.5 GHz. The proposed LNA consumes ultra-low power consumption of 21.3 mW under the power supply of 1.2 V. © The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature 2024.Item Investigation on Tribological Behavior of Al7075-TiC/Graphene Nano-composite Using Taguchi Method(Springer Science and Business Media Deutschland GmbH, 2024) Lingaraju, S.V.; Hatti, G.; Jadhav, M.R.; Dhuttargaon, M.S.; Doddamani, S.This study addresses the limited understanding of how nano-materials affect the mechanical properties and wear behavior of AMMNCs, focusing on challenges in achieving uniform nano-material distribution and optimizing processing parameters. This study explores the fabrication and tribological performance of Al7075 hybrid metal matrix nano-composites reinforced with TiC and Graphene using ultrasonic stir casting. By varying TiC content (0.5 to 2.5 wt%) and maintaining 0.25-wt% Graphene, the composites were tested under dry sliding conditions. Results indicate that the hybrid nano-composite with 1.5 wt% TiC and 0.25 wt% Graphene exhibits optimal wear resistance and frictional behavior, attributed to improved hardness and reduced surface damage. This results from harder particles intermingling with the softer alloy, which shows increased hardness with reduced delamination, cracks, and fractures of inside surfaces during wear. © The Author(s), under exclusive licence to Springer Nature Switzerland AG 2024.Item An iron(iii) oxide-anchored conductive polymer-graphene ternary nanocomposite decorated disposable paper electrode for non-enzymatic detection of serotonin(Royal Society of Chemistry, 2024) Prashanth, S.; Aziz, R.A.; Raghu, S.V.; Shim, Y.-B.; Prasad, K.; Vasudeva Adhikari, A.V.Serotonin, also known as 5-hydroxytryptamine (5-HT), is an important neurotransmitter that regulates many physiological processes. Both low and high concentrations of 5-HT in the body are associated with several neurological disorders. Hence, there is an urgent need to develop fast, accurate, reliable, and cost-effective disposable sensors for 5-HT detection. Herein, we report the sensing of 5-HT using a disposable paper-based electrode (PPE) modified with a ternary nanocomposite comprising poly(pyrrole) (P(py)), reduced graphene oxide (rGO), and iron oxide (Fe2O3). The sensor material was well characterized in terms of its structural, morphological, and chemical attributes using electron microscopy, spectral techniques, and electrochemical studies to prove the robust formation of the electroactive ternary nanocomposite and its suitability for 5-HT detection. The developed sensor exhibited an impressive limit of detection (LOD) of 22 nM with a wide linear range of 0.01 to 500 ?M, which falls in the recommended clinically relevant range. The analytical recovery, spike sample analysis, and interference studies with ascorbic acid (AA), uric acid (UA), and epinephrine (E) showed satisfactory results, wherein the sensor could detect simultaneously both 5-HT and dopamine (DA). The potential practical utility of the developed sensor was further assessed by quantifying the concentration of 5-HT in the brain samples of Drosophila melanogaster, a versatile genetic model organism employed for modeling different neural disorders in humans, and validated by gold-standard HPLC-UV experiments. The as-fabricated single-run disposable sensor with a ternary nanocomposite exhibits excellent stability with good reproducibility and is a promising platform for identifying clinically relevant concentrations of 5-HT. © 2024 RSC.Item Copper-graphene nanocomposite fabrication through LP-DED process: Powder preparation, characterization and printability studies(Elsevier Ltd, 2024) Sharma, S.; Thanumoorthy, R.S.; Bontha, S.; Balan, A.S.S.Copper and its alloys play a crucial role in various engineering applications due to their excellent conductive properties. However, their poor laser absorptivity and high conductivity make them a complex material to work with using laser additive manufacturing processes, hindering the ease of fabrication of precise and complex geometries. To overcome this challenge, graphene-reinforced copper powders were employed to enhance laser absorptivity. With graphene addition, there was a substantial increase in the laser absorptivity. The addition of graphene improved laser absorptivity from 15 % for pure copper to ~60 % in Gr-Cu composites. However, the flowability deteriorated at higher compositions, which could result from increased specific surface area due to graphene agglomeration and its nanoscale surface. The influence of graphene on the ease of fabrication employing laser powder-directed energy deposition was evaluated with a single-track and bulk deposition. A single-track study revealed that pure copper tracks were inconsistent and exhibited poor bonding due to their poor laser absorptivity. Meanwhile, graphene?copper composite tracks displayed stable melt pools and uniform tracks, which could result from enhanced absorptivity. Geometrically sound and defect-free Gr-Cu tracks were deposited using 750 W laser power with composite powders, while pure copper tracks at 950 W laser power deposition yielded defective tracks. However, a graphene percentage above 0.1 % resulted in the formation of keyhole porosity due to a significant enhancement in laser absorption (~60 %). A similar observation was made for bulk deposition, i.e., defect-free deposition for Gr-Cu composites ?0.1 % graphene and keyhole porosities in the deposition of 0.25Gr-Cu and 0.8Gr-Cu. © 2024 The Society of Manufacturing EngineersItem Nonlinear buckling and free vibration analysis of auxetic graphene origami composite beams under nonuniform thermal environment(Taylor and Francis Ltd., 2025) Shashiraj; Pitchaimani, J.; Kattimani, S.This study examines the thermo-mechanical behavior of auxetic metamaterial beams enhanced by graphene origami (GOri) under spatially varying nonuniform temperature distributions (SVTD). Utilizing Timoshenko beam theory considering von-Kármánn type nonlinear strain–displacement relationship, GOri beams are modeled as layered structures. The Ritz method is employed to solve equilibrium equations, analyzing the impact of GOri distribution patterns, content, and folding degree on post-buckling and vibration paths. The effects of five SVTDs, three end conditions, and three GOri distribution patterns on buckling, post-buckling behavior, and nonlinear free vibration characteristics are explored. Findings reveal that the parabolic temperature distribution with peak temperatures at beam ends (P-MAE) results in higher critical temperatures and nonlinear free vibration frequencies. This research provides crucial insights into the design and optimization of GOri-enabled metamaterial structures in complex thermal environments, highlighting the significant influence of nonuniform temperature distributions along the beam’s length. © 2024 Taylor & Francis Group, LLC.Item Neodymium doped graphene quantum dots/PANI composite for supercapacitor application(Elsevier Ltd, 2025) Muhiuddin, M.; Bharadishettar, N.; Devi, N.A.; Gautam, A.; Chauhan, S.S.; Siddique, A.B.; Ahmad, M.I.; Satyanarayan, M.N.; K, U.B.; Akhtar, W.; Rahman, M.R.The publication presents a streamlined and economical technique for fabricating advanced electrode materials to enhance the energy storage capabilities of supercapacitors (SCs). The focus is on synthesizing neodymium-doped graphene quantum dots (Nd-GQDs) via a microwave-assisted hydrothermal (MAH) process. This method uses microwave irradiation's rapid heating and efficient energy transfer under low pressure and minimal reaction time. The resulting Nd-GQDs exhibit enhanced electrochemical properties, including increased capacitance and improved charge storage, making this approach practical and effective for advancing supercapacitor technology. An exceptional specific capacitance of 618 F g?1 at a 5 mV s?1 scan rate is demonstrated using Nd-GQDs as the SC electrode material. Due to their high specific capacitance, Nd-GQDs, when combined with polyaniline (PANI), improve the energy and power density of SCs. Nd-GQDs/PANI composites with varying amounts of Nd-GQDs in symmetric SCs are fabricated to demonstrate their promising properties for SC applications. SCs fabricated with 20 mL of Nd-GQDs in the PANI matrix showed a superior specific capacitance of 354 F g?1 at a current density of 1 A g?1, while the energy density and power density were 49.15 Wh kg?1 and 2000 W kg?1, respectively. © 2025 Elsevier B.V.Item The cohesion strength of electrodeposited Zn/GO nanocomposite coating on stainless steel(Elsevier Ltd, 2025) Bharathi, K.D.; Udaya Bhat, K.; Bhat Panemangalore, P.; Arun Kumar, D.S.; Rahman, M.R.Graphene based nanocomposite coatings have incredible scope in enhancing the physical properties of composite materials. In this study, pure Zn and Zn/GO nanocomposite coatings were successfully prepared by electrodeposition technique on the SS304 stainless steel. The Zn/GO nanocomposite coatings were prepared by varying concentration of GO, coating time and CTAB ratio. The nanocomposite coatings were characterized by using the Field emission scanning electron microscopy (FESEM), X-ray diffractometry (XRD), Energy-dispersive X-ray spectroscopy (EDS), and Raman spectroscopy. Cohesion strength (LC) using scratch test at RT noticed that the LC values increased with the concentration of GO. The scratch tests revealed that Zn/GO composite produced using 40 mgL?1 GO had 70 % increase in cohesion strength (LC1) in comparison to pure Zn coating deposited with 30 min of coating time at a ratio of 1:2 GO:CTAB. The magnitude of the residual stress in the nanocomposite coating decreases from ?32 MPa (0 mgL?1 of GO) to ?11 MPa (40 mgL?1 of GO) as the GO concentration increases in coatings due to the effect of the kinetic movement of particles while deposition. © 2024Item Green covalent surface functionalization of carbon nanofillers and hybridization to improve the thermal and electrical properties of RTV SR nanocomposites(Elsevier Ltd, 2025) Chandrashekar, A.; Hegde, M.; Siya; Karthik Reddy, B.; Jineesh, J.A.; Ravichandran, V.; Eswaraiah, E.; Prabhu, T.N.In this work, graphene (GP) and multiwalled carbon nanotubes (MWCNT) are covalently surface functionalized via a green method using clove extract. The clove–modified carbon hybrid silicone rubber (SR) nanocomposites are fabricated by incorporating clove –modified GP (CGP) and MWCNT (CMWCNT) in various weight ratios with a total filler loading of 10 wt%. Our study investigated the effect of green covalent surface modification and the use of hybrid filler on the thermal and electrical properties of the silicone rubber. The nanocomposite with 9:1 hybrid ratio showed the highest thermal conductivity of about 0.406 W m?1 K?1, 103 % enhancement and thermal effusivity of about 766.2 Ws1/2 m?2 K?1, 29.64 % enhancement with respect to pure SR. Thermal management performance was evaluated by applying thermal compounds as thermal interface material on a 1 W light emitting diode (LED) bulb for testing. It was found that during heating, the hybrid composite with 9:1 ratio showed 2.3 °C reduction in the surface temperature of the LED bulb (under ON condition) and reduced the surface temperature by 1.8 ? within 20 s and reached almost room temperature in 100 s (under OFF condition). In addition, nanocomposite with 9:1 hybrid ratio showed excellent thermal stability, enhanced electrical resistivity which presents a promising strategy for designing thermally conductive polymer nanocomposites based thermal interface materials in managing excess heat for thermal management applications. © 2025Item Efficiency enhancement in dye-sensitized solar cells through neodymium-doped graphene quantum dot-modified TiO? photoanodes(Elsevier B.V., 2025) Senadeera, G.K.R.; Weerasekara, W.M.S.K.; Jaseetharan, T.; Sandunika, P.U.; Kumari, J.M.K.W.; Dissanayake, M.A.K.L.; Muhiuddin, M.; Rahman, M.R.; Bhat K, U.; Akhtar, M.W.; Udayakumar, U.; Siddique, A.B.; Ekanayake, P.This study explored the effects of Neodymium-doped graphene quantum dots (NdGQDs) on improving the performance efficiency of TiO2 based dye-sensitized solar cells (DSSCs). By employing in-situ physical assisted mixing, DSSCs with optimized NdGQDs in TiO2 photoanodes showed a power conversion efficiency of 8.76 %, a significant improvement compared to the 6.01 % efficiency of pristine TiO2-based DSSCs under 100 mW cm?2 illumination (AM 1.5). Notably, the short-circuit current density increased by 74 %. HRTEM analysis revealed that the NdGQDs have a size range of approximately 7–9 nm. UV–visible spectroscopy and Mott-Schottky analysis revealed a positive shift in the Fermi level, promoting better electron transfer and increased photocurrent density at the expenses of the open circuit voltage. Electrochemical impedance spectroscopy characterization of DSSCs incorporating NdGQD-modified photoanodes revealed a reduction in electron transfer resistance at the photoanode|dye|electrolyte interface, accompanied by an increase in recombination resistance within the device suppressing the electron recombination rate. © 2024 Elsevier B.V.Item Non-linear transient vibration response of graphene origami enhanced metamaterial beams under spatially-varying temperature distributions(Elsevier Ltd, 2025) Shashiraj; Pitchaimani, J.; Kattimani, S.Understanding the dynamic behavior of advanced materials under varying conditions is crucial for the development of resilient and efficient structural systems. This research investigates the non-linear transient response of auxetic metamaterial beams enhanced with graphene origami under spatially varying non-uniform thermal environment. Using Timoshenko beam theory with von-Kármánn type non-linear strain–displacement relations, graphene origami beams are modeled as layered structures. The equilibrium equations are solved using the Ritz method, with a focus on how different graphene origami distribution patterns, content levels, and folding degrees influence the transient response under various time-dependent forces. Non-linear motion equations are solved using the Newmark-Beta method. This study evaluates the impact of five distinct non-uniform temperature distributions, seven types of time-dependent loadings, three boundary conditions, and three configurations of graphene origami distribution on the vibration characteristics. Results indicate that parabolic temperature distributions with peak temperatures at the beam ends lead to substantially decreased dynamic deflections. This research provides valuable insights into the structural dynamics of graphene origami-enhanced metamaterial beams within complex thermal environments, highlighting the considerable influence of spatial temperature variations along the length of the beam. © 2025