Browsing by Author "Singh, R."

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A DFT study of the adsorption behavior and sensing properties of CO gas on monolayer MoSe2 in CO2-rich environment
(Springer Science and Business Media Deutschland GmbH, 2024) Vinturaj, V.; Yadav, A.K.; Singh, R.; Garg, V.; Bhardwaj, R.; Ajith, K.M.; Pandey, S.K.
Context: Carbon monoxide, also known as the “silent killer,” is a colorless, odorless, tasteless, and non-irritable gas that, when inhaled, enters the bloodstream and lungs, binds with the hemoglobin, and blocks oxygen from reaching tissues and cells. In this work, the monolayer MoSe2-based CO gas sensors were designed using density functional theory calculation with several dopants including Al, Au, Pd, Ni, Cu, and P. Here, Cu and P were found to be the best dopants, with adsorption energies of −0.67 eV (Cu) and −0.54 eV (P) and recovery times of 1.66 s and 13.8 ms respectively. Cu conductivity for CO adsorption was found to be 2.74 times that of CO2 adsorption in the 1.0–2.26 eV range. P displayed the highest selectivity, followed by Pd and Ni. The dopants, Pd and Ni, were found suitable for building CO gas scavengers due to their high recovery times of 9.76 × 1020 s and 2.47 × 1011 s. Similarly, the adsorption of CO2 on doped monolayer MoSe2 was also investigated. In this study, it is found that monolayer MoSe2 could be employed to create high-performance CO sensors in a CO2-rich environment. Method: The electrical characteristics of all doped MoSe2 monolayers are obtained using a DFT calculation with the PBE-GGA method from the Quantum ESPRESSO package. The self-consistent field (SCF) computations were performed using a 7 × 7 × 1 k-point grid and a norm-conserving pseudo potential (NCPP) file. To determine electrical conductivity, the semi-classical version of Boltzmann transport theory, implemented in the Boltz Trap code, was used. © The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature 2024.
A high thermally stable polyacrylonitrile (PAN)-based gel polymer electrolyte for rechargeable Mg-ion battery
(Springer, 2020) Singh, R.; Janakiraman, S.; Khalifa, M.; Anandhan, S.; Ghosh, S.; Adyam, A.; Biswas, K.
The ionic conductivity and thermal stability of the electrolyte-separator system is an essential parameter for improving battery performance and safety. The present work addresses the high thermally stable gel polymer electrolyte (GPE) using polyacrylonitrile (PAN) as a polymer membrane and magnesium perchlorate in propylene carbonate (Mg(ClO4)2-PC) as a liquid electrolyte. The PAN based polymer membrane is prepared by electrospinning process which produces a bead free and uniformly distributed nanofibers. The electrospun PAN based GPE is characterized by different physical and electrochemical techniques like X-ray diffraction, field emission scanning electron microscopy, thermogravimetric analysis, differential scanning calorimetry, ionic conductivity, linear sweep voltammetry, magnesium ion transference number and electrochemical impedance spectroscopy. The ionic conductivity of PAN is 3.28 mS cm?1, compared to that of PP Celgard is 1.97 × 10–4 mS cm?1 at 30 °C. The electrochemical stability of PAN is 4.6 V and also exhibits excellent interfacial stability with magnesium metal. The results showed that the PAN-based GPE has higher ionic conductivity and thermal stability than the polypropylene (PP) Celgard membrane. © 2020, Springer Science+Business Media, LLC, part of Springer Nature.
An electroactive ?-phase polyvinylidene fluoride as gel polymer electrolyte for magnesium–ion battery application
(Elsevier B.V., 2019) Singh, R.; Janakiraman, S.; Khalifa, M.; Anandhan, S.; Ghosh, S.; Adyam, A.; Biswas, K.
The gel polymer electrolytes (GPEs) are currently interesting research area in rechargeable batteries. In the present study, synthesis and characterization of electroactive gel polymer electrolyte (EGPE) for Mg-ion batteries application have been investigated. The bead free electroactive polyvinylidene fluoride (PVDF) with high porosity is achieved by an electrospinning process. The ?-phase of PVDF is polar and electroactive with a high dipole moment. Electroactive ?-phase is confirmed by X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR). Field emission scanning electron microscopy (FESEM) study is done to analyze the structure and morphology of the electroactive membrane. The electroactive gel polymer electrolyte is formed by immersing an electroactive PVDF membrane in 0.3 M magnesium perchlorate (MgClO4) and propylene carbonate (PC) solution. The ionic conductivity of electroactive ?-phase PVDF membrane is achieved to be 1.49 mS cm?1 at 30 °C, which is higher than commercial available polypropylene (PP) Celgard. Tortuosity of electroactive gel polymer electrolyte is found to be 1.44. The voltage stability of the EGPE is stable up to a high voltage of 5.0 V against Mg+2/Mg. The total ionic transference number and magnesium ion transference number of EGPE are also investigated to confirm high ionic conductivity. © 2019 Elsevier B.V.
BEV-MoSeg: Segmenting Moving Objects in Bird's Eye View
(Institute of Electrical and Electronics Engineers Inc., 2023) Sigatapu, A.K.; Satagopan, V.; Sistu, G.; Singh, R.; Narasimhadhan, A.V.
Accurate detection of moving objects plays a vital role in motion planning and vehicle maneuvering for autonomous vehicles. Though there is a significant improvement in perception tasks like object detection and semantic segmentation by adopting Bird's Eye View (BEV) based techniques like LiftSplatShoot, SimpleBEV etc., the moving object segmentation has gained limited attention. This research addresses this gap and propose a novel end-to-end architecture that implicitly utilizes temporal cues like optical flow in BEV space by correlation or cross-attention for moving vehicle segmentation. This work also introduces custom labels to annotate moving objects in the nuScenes dataset, enhancing its utility for the BEV motion segmentation task. We achieved an Moving Vehicle IoU Score of 26% on nuScenes dataset on full six camera rig and 22% on single front camera. The code for generating these labels and the qualitative results of our model can be found in, Project page with code: https://ajayrafa25.github.io/BEV-MoSeg/ Â© 2023 IEEE.
Development of thick SiC coating on thin wall tube of zircaloy-4 using laser based directed energy deposition technique
(Elsevier B.V., 2020) Rai, A.K.; Srinivasulu, B.; Paul, C.P.; Singh, R.; Rai, S.K.; Mishra, G.K.; Bontha, S.; Bindra, K.S.
In the present study, optimization of various laser-processing parameters for the deposition of thick SiC coating on zircaloy-4 (Zry-4) tube is studied in view of the development of accident tolerant fuel clad material for current and future nuclear reactors with the enhanced safety. The SiC coatings are deposited using laser directed energy deposition (LDED). It is found to be quite challenging to deposit desired SiC coating on a thin (~400 ?m) substrate of Zry-4 tubes due to either its excessive melting or damage. This is minimized largely by cooling the tube from inside by passing Ar gas (20 l min?1). It is observed that different processing parameters play a vital role on homogeneity, uniformity and defects-free SiC coatings as well as on the melting and oxidation of Zry-4 substrate. A uniform and homogeneous coating of SiC is deposited on Zry-4 at the optimized laser power density of 4.52 kW cm?2, powder feed rate of 2.71 g min?1and scan speed of 325 mm min?1. The interface between SiC coatings and substrate is characterized using different techniques such as optical microscopy, scanning electron microscopy and X-ray diffraction to access the homogeneity, uniformity, defects and to identify the different phases formed in the coated layer. Coated layer is found to be consisting of Zr(?), SiC, ZrSi2, ZrSi and ZrC types of phases and the same is also confirmed by the ThermoCalc(R) based ternary phase diagram. Further, the effect of processing parameters on substrate melting and the nature of SiC coating is explained by simulating the substrate temperature using COMSOL@ multi-physics. To the author's best knowledge, this would be the first study to report the laser directed energy deposition of SiC on Zry-4 alloy. © 2020 Elsevier B.V.
DFT Calculations for Temperature Stable Quantum Capacitance of VS2 Based Electrodes for Supercapacitors
(Institute of Electrical and Electronics Engineers Inc., 2024) Yadav, A.K.; Shreevathsa, N.S.; Singh, R.; Das, P.P.; Garg, V.; Pandey, S.K.
Using density functional theory calculations, we demonstrate the quantum capacitance of the VS2 electrode which can be improved by doping with non-metallic elements such as nitrogen (N), phosphorus (P), and arsenic (As) atoms. The radius, charge, and morphology of these non-metallic elements help to improve the performance of VS2 material as electrodes of supercapacitors. The As-doped VS2 monolayer demonstrated the maximum quantum capacitance of 31.2369 μF/cm2 at 300 K. At 1200 K, quantum capacitance reaches the value of 25.2149 μF/cm2, showing the inconsiderable change in value for this wide range of temperature variation. Additionally, the other important properties of undoped and doped VS2 monolayers such as density of states, energy band structure, electrical conductivity, thermal conductivity, and the Seebeck coefficient were also computed and examined in detail. The band structure of the P and As-doped VS2 monolayers showed a metallic nature, which is suitable for electrode application. In the case of As-doped VS2 material, a high figure of merit of 3.536 was observed by using DFT-D2 calculations, due to the large Seebeck coefficient and significant electrical conductivity. Our findings will be helpful in further exploring the suitability of VS2 monolayers as electrodes of supercapacitors. © 2002-2012 IEEE.
DFT Study about the Effect of Doping on the Properties of GaSb Material and Designing of High-Efficiency Infrared Photodetector
(John Wiley and Sons Inc, 2023) Bhandari, B.; Yadav, A.K.; Singh, R.; Kiran, G.; Singh, A.K.; Garg, V.; Pandey, S.K.
The gallium antimonide (GaSb) material has very attractive electronic and optoelectronic properties which are suitable for next-generation infrared (IR) photodetector applications. In this work, properties of undoped GaSb material such as density of states, bandstructure, electron density, absorption coefficient, dielectric function, refractive index, and extinction coefficient are calculated using density-functional theory (DFT). Moreover, the effects of doping with Ge, Sn, and Zn elements on these properties of GaSb material are investigated. It is found that undoped GaSb material exhibits a direct gap of ≈0.72 eV. Among different doping elements, Ge-doped GaSb produces a very significant enhancement in optical properties. The Ge-doped GaSb demonstrates a four times higher absorption coefficient in comparison to undoped GaSb in the IR region at 0.8 eV photon energy. GaSb-based photodetector device is designed using the Solar Cell Capacitance Simulator (SCAPS) 1D tool. The efficiency of the designed photodetector with optimum thicknesses and doping of different layers is found to be improved from 21.34% to 25.91% after incorporating the absorption data set obtained from the DFT calculations. Additionally, the photodetector with optimum parameters demonstrates maximum responsivity of value ≈0.31 A W−1. In the previous findings, it is demonstrated that GaSb is a very suitable material for next-generation IR photodetector applications. © 2023 Wiley-VCH GmbH.
Dynamics of strongly coupled fluid-filled micro-cavities and PMUTs in integrated microfluidic devices
(2016) Dangi, A.; Singh, R.; Deshmukh, D.; Pratap, R.
In this work, we present a novel device developed by integration of an array of Piezoelectric Micromachined Ultrasonic Transducers (PMUTs) with a microfluidic chip that can be used for characterizing the acoustical properties of the liquid present in the back-cavity of the PMUT. PMUT membrane operates in flexural mode of vibration and it is directly coupled with the cylindrical back-cavity formed during the release of the PMUT membrane. This leads to very strong structural-acoustic coupling between the PMUT and the liquid present in the its back-cavity. Presence of fluid around the thin PMUT membrane causes a significant reduction in the resonant frequencies of the PMUT due to mass loading imposed by the surrounding fluid. It also leads to the excitation of the acoustic modes of the cylindrical back-cavity when the PMUT vibrates near the fundamental acoustic frequencies of the cavity. These acoustic reverberations appear in the vibration response of the PMUT in form of additional resonant peaks. Further we explore the feasibility of capturing the acoustic signature of microbubbles introduced in the backcavity liquid. Microbubbles are generated on the microfluidic chip using flow focusing technique and introduced in the cylindrical back-cavity of the PMUT through a network of channels and wells made on PDMS and adhered to the PMUT from the backside. This approach can provide an alternative method for on-chip characterization of microbubbles. Copyright � 2016 by ASME.
Dynamics of strongly coupled fluid-filled micro-cavities and PMUTs in integrated microfluidic devices
(American Society of Mechanical Engineers (ASME) infocentral@asme.org, 2016) Dangi, A.; Singh, R.; Deshmukh, D.; Pratap, R.
In this work, we present a novel device developed by integration of an array of Piezoelectric Micromachined Ultrasonic Transducers (PMUTs) with a microfluidic chip that can be used for characterizing the acoustical properties of the liquid present in the back-cavity of the PMUT. PMUT membrane operates in flexural mode of vibration and it is directly coupled with the cylindrical back-cavity formed during the release of the PMUT membrane. This leads to very strong structural-acoustic coupling between the PMUT and the liquid present in the its back-cavity. Presence of fluid around the thin PMUT membrane causes a significant reduction in the resonant frequencies of the PMUT due to mass loading imposed by the surrounding fluid. It also leads to the excitation of the acoustic modes of the cylindrical back-cavity when the PMUT vibrates near the fundamental acoustic frequencies of the cavity. These acoustic reverberations appear in the vibration response of the PMUT in form of additional resonant peaks. Further we explore the feasibility of capturing the acoustic signature of microbubbles introduced in the backcavity liquid. Microbubbles are generated on the microfluidic chip using flow focusing technique and introduced in the cylindrical back-cavity of the PMUT through a network of channels and wells made on PDMS and adhered to the PMUT from the backside. This approach can provide an alternative method for on-chip characterization of microbubbles. Â© Â© 2016 by ASME.
Effect of Introducing Defects and Doping on Different Properties of Monolayer MoS2
(John Wiley and Sons Inc, 2023) Prajakta, K.; Vinturaj, V.P.; Singh, R.; Garg, V.; Pandey, S.K.; Pandey, S.K.
Herein, the comprehensive study of different properties of undoped MoS2, MoS2 lattice with sulfur (S) and, molybdenum (Mo) vacancy, and MoS2 with substitutional doping of niobium (Nb), vanadium (V), and zinc (Zn) atoms is done. The density functional theory (DFT) is used and the electronic properties like density of states, band structure, electron density, and optical properties like dielectric function, optical conductivity, and refractive index are studied. It is observed that undoped MoS2 monolayer shows direct bandgap semiconductor characteristics with a bandgap of around 1.79 eV. P-type characteristics are observed for Nb-, V-, and Zn-doped MoS2 lattices. The real part and imaginary parts of all optical parameters along x and z directions for different MoS2 supercells are found to be anisotropic in nature up to a photon energy of almost 11 eV and thereafter they show nearly isotropic nature. Finally, it is found that the obtained properties of MoS2 monolayer as per literature are suitable for next-generation MOSFET application. © 2023 Wiley-VCH GmbH.
An electroactive ?-phase polyvinylidene fluoride as gel polymer electrolyte for magnesium ion battery application
(2019) Singh, R.; Janakiraman, S.; Khalifa, M.; Anandhan, S.; Ghosh, S.; Venimadhav, A.; Biswas, K.
The gel polymer electrolytes (GPEs) are currently interesting research area in rechargeable batteries. In the present study, synthesis and characterization of electroactive gel polymer electrolyte (EGPE) for Mg-ion batteries application have been investigated. The bead free electroactive polyvinylidene fluoride (PVDF) with high porosity is achieved by an electrospinning process. The ?-phase of PVDF is polar and electroactive with a high dipole moment. Electroactive ?-phase is confirmed by X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR). Field emission scanning electron microscopy (FESEM) study is done to analyze the structure and morphology of the electroactive membrane. The electroactive gel polymer electrolyte is formed by immersing an electroactive PVDF membrane in 0.3 M magnesium perchlorate (MgClO4) and propylene carbonate (PC) solution. The ionic conductivity of electroactive ?-phase PVDF membrane is achieved to be 1.49 mS cm?1 at 30 C, which is higher than commercial available polypropylene (PP) Celgard. Tortuosity of electroactive gel polymer electrolyte is found to be 1.44. The voltage stability of the EGPE is stable up to a high voltage of 5.0 V against Mg+2/Mg. The total ionic transference number and magnesium ion transference number of EGPE are also investigated to confirm high ionic conductivity. 2019 Elsevier B.V.
Estimating multiple physical parameters from speech data
(2016) Kalluri, S.B.; Vijayakumar, A.; Vijayasenan, D.; Singh, R.
In this work, we explore prediction of different physical parameters from speech data. We aim to predict shoulder size and waist size of people from speech data in addition to the conventional height and weight parameters. A data-set with this information is created from 207 volunteers. A bag of words representation based on log magnitude spectrum is used as features. A support vector regression predicts the physical parameters from the bag of the words representation. The system is able to achieve a root mean square error of 6.6 cm for height estimation, 2.6cm for shoulder size, 7.1cm for waist size and 8.9 kg for weight estimation. The results of height estimation is on par with state of the art results. � 2016 IEEE.
Estimating multiple physical parameters from speech data
(IEEE Computer Society help@computer.org, 2016) Kalluri, S.B.; Vijayakumar, A.; Vijayasenan, D.; Singh, R.
In this work, we explore prediction of different physical parameters from speech data. We aim to predict shoulder size and waist size of people from speech data in addition to the conventional height and weight parameters. A data-set with this information is created from 207 volunteers. A bag of words representation based on log magnitude spectrum is used as features. A support vector regression predicts the physical parameters from the bag of the words representation. The system is able to achieve a root mean square error of 6.6 cm for height estimation, 2.6cm for shoulder size, 7.1cm for waist size and 8.9 kg for weight estimation. The results of height estimation is on par with state of the art results. Â© 2016 IEEE.
Growth optimization and DFT investigation of doping effect on properties of VS2 monolayer crystals
(Springer Science and Business Media Deutschland GmbH, 2023) Yadav, A.K.; Patel, C.; Kiran, G.; Singh, R.; Singh, A.K.; Garg, V.; Mukherjee, S.; Pandey, S.K.
The vanadium disulfide (VS2) material, a prominent member of the two-dimensional materials family, has great potential to bridge the performance gap between current performance and contemporary energy storage device needs. Here, we report the optimization of the growth temperature of VS2 monolayer crystals using a chemical vapor deposition system. It is also found the crystal size increases with the increase of growth temperature up to 770 °C. Further increasing of growth temperature resulted in a reduction of crystal size. The atomic force microscopy measurement demonstrated the growth of monolayer thick VS2 crystal. Raman spectra revealed the formation of H-phase monolayer high-quality VS2 crystals. To understand the precise impact of doping on electronic properties, the substitutional doping of VS2 monolayer with chromium, molybdenum, and tungsten was also examined using density functional theory. The VS2 monolayer exhibits an indirect energy band gap that decreases after chromium doping of the VS2 lattice and vanishes after molybdenum and tungsten doping. Finally, it is found that tungsten-doped VS2 monolayer exhibits strong metallic character and other exceptional properties, making it suitable for electrodes of various energy storage devices. Graphical abstract: [Figure not available: see fulltext.]. © 2023, The Author(s), under exclusive licence to EDP Sciences, SIF and Springer-Verlag GmbH Germany, part of Springer Nature.
Large and Uniform Single Crystals of MoS2Monolayers for ppb-Level NO2Sensing
(American Chemical Society, 2022) Patel, C.; Singh, R.; Dubey, M.; Pandey, S.K.; Upadhyay, S.N.; Kumar, V.; Sriram, S.; Than Htay, M.; Pakhira, S.; Atuchin, V.V.; Mukherjee, S.
Recently, unprecedented interest has been immersed toward the synthesis of two-dimensional (2D) transition metal dichalcogenides via the chemical vapor deposition (CVD) system. Synthesis of a uniform and large-sized monolayer MoS2atomic thin film via CVD is still a major bottleneck owing to strong dependence on diverse associated growth parameters. In this work, we have proposed the most viable recipe which is suitable for controlling the nucleation density of Mo and producing a 90 μm-long MoS2monolayer crystal and (695 × 394.8) μm2large MoS2monolayered film on SiO2/Si and c-plane sapphire, respectively. Moreover, MoS2monolayer sensing performance has been thoroughly investigated for NO2exposure at room temperature with a varying response of 4-57.5 for the 100-100 ppm level. Furthermore, the MoS2monolayer sensor exhibits an ultrasensitive NO2detection with limit of detection and limit of qualification values of 1.4 and 4.6 ppb, respectively. In addition, the first-principles-based density functional theory has been employed to analyze the adsorption of NO2on the surfaces of the 2D MoS2monolayer. It is observed that the electronic band gap of the MoS2monolayer after NO2adsorption is reduced by 0.7 eV due to molecular orbital hybridization. © 2022 American Chemical Society. All rights reserved.
Leveraging Hybrid Modeling for Enhanced Runtime Prediction in Big Data Jobs
(Institute of Electrical and Electronics Engineers Inc., 2024) Singh, R.; Zadokar, V.N.; Kumar, S.; Doddamani, S.S.; Bhowmik, B.
In an era of rapid data expansion, big data has significantly transformed various industries, redefining the processes of data processing, analysis, and utilization. The widespread adoption of digital technologies has driven this surge in big data, leading to an unprecedented accumulation of information from sources such as social media, sensors, and transactions. As big data evolves, it presents significant challenges and unique opportunities, necessitating innovative solutions to leverage its potential fully. One critical challenge in big data environments is accurately predicting job runtimes, essential for optimizing resource utilization and enhancing overall system performance. Current approaches, including analytical models and machine learning algorithms, often need help to manage the complexities of unstructured data and maintain interpretability effectively. This paper proposes a novel hybrid modeling approach that integrates the strengths of both techniques to improve job runtime predictions. The hybrid architecture combines an analytical model, which captures the intricate characteristics of jobs and execution environments, with a machine learning model trained to detect patterns and relationships in historical data. As demonstrated on real-world big datasets, the hybrid model achieves greater accuracy by merging these capabilities. Utilizing the flexible capabilities of PySpark and incorporating advanced feature engineering techniques, the model dynamically adapts to various dataset sizes and complexities, ensuring robust performance across different scenarios. Â© 2024 IEEE.
Micro-Architectural support for High Availability of NoC-based MP-SoC
(Institute of Electrical and Electronics Engineers Inc., 2019) Singh, R.; Ranga, S.V.; Patil, S.; Krishna, M.; Mehta, M.; Anoop, M.N.; Nandy, S.K.; Haldar, C.; Narayan, R.; Neumann, F.; Baufreton, P.
In this paper, we focus on increasing the availability of Multi-Processor System on Chip (MP-SoC) for executing user applications, even when some components of the system are faulty. A Network-on-Chip (NoC) provides high bandwidth communication substrate for the multitude of components/modules in such MP-SoCs. Health of such MP-SoC, and hence its availability, is largely dependent on the health of the NoC. We consider an NoC comprising a bidirectional toroidal mesh interconnection of routers. We use a distributed built-in-self-test to identify faulty communication links. We use information so obtained to determine healthy subsystems that can be made available for executing user applications. This feature is key for enhancing availability of MP-SoCs. We realize this feature as a micro-architectural enhancement in MP-SoC that incurs an insignificant hardware overhead of less than 2%. Latency incurred for analyzing availability of MP-SoC is also insignificant. We functionally validate our proposal by emulating the system on a FPGA device and demonstrate increase in availability of the MP-SoC. Â© 2019 IEEE.
Microstructural evolution and cyclic oxidation behavior of HVOF-sprayed NiCrSi and NiCrC coatings on T11 steel
(Elsevier Inc., 2024) Medabalimi, S.; Hebbale, A.M.; Singh, R.; Desai, V.; Ramesh, M.R.
This study analyzes NiCrSi and NiCrC coatings developed on low alloy ferritic stainless steel (grade T11) through the HVOF spraying technique. The coatings were characterized by their phase constitution, microstructure, cyclic oxidation behavior, and hardness. X-ray diffraction (XRD) analysis confirmed the presence of the NiCr solid solution matrix as the primary phase in both coatings. Moreover, the microstructure of the NiCrSi coating included the hard intermetallic compounds like Cr?Si and Ni?Si and the NiCrC coating contained the hard phases like Cr?C? and Ni?C which improved the hardness and the wear resistance of the coatings. Microhardness measurements revealed that the coatings had an average hardness of 300 ± 50 HV, significantly greater than the substrate hardness of 225 ± 25 HV. Cyclic oxidation tests were carried out at 700 °C revealed that both the coatings showed a lower weight gain than the uncoated substrate, suggesting enhanced oxidation resistance. This was because the protective oxide layers like Cr?O? and SiO? in the NiCrSi coating and Cr?O? and NiO in the NiCrC coating were formed. X-ray analysis establish ed. the presence of these oxides, which inhibited oxygen penetration through the coatings and provided additional protection against oxidation. Therefore, the study revealed that both NiCrSi and NiCrC coatings have good mechanical and oxidation resistance properties, which make them suitable for high-temperature applications where there is a need for improved durability, wear resistance, and protection against oxidation. © 2024
On the merit of solute segregation and low angle grain boundary for thermal stability and thermal expansion of cold-sprayed CuCrZr
(Elsevier Ltd, 2025) Abhijith Vijay; Sreerag, M.P.; Varalakshmi, S.; Santhy, K.; Singh, R.; Kondás, J.; Makineni, S.K.; Rajasekaran, B.
The precipitation hardenable CuCrZr alloy is a potential alternative to copper for inner liners in rocket thrust engines. Cold spray manufacturing has been seen as a promising processing route to manufacture bulk additive structure of CuCrZr. This work reveals that the cold-sprayed as-deposited Cu-Cr-Zr alloy, in its inherent non-equilibrium state. It is highly stable up to 950 °C and exhibits lower thermal expansion than the equilibrium Cu-Cr-Zr alloy, deduced using HT-XRD and Thermo-Calc. Atomic-scale compositional and diffraction analysis using Atom Probe Tomography (APT) and Electron Backscatter Diffraction (EBSD) support the Zener pinning effect of Cr segregation near the grain boundaries, along with a large fraction of low-angle grain boundaries (LAGBs), that contribute to the high thermal stability and controlled thermal expansion of the deposit. Cold spray deposition naturally yields microstructural features that are conducive to high thermal stability and controlled thermal expansion, features which are comparable to the self-organized microstructures observed in segregation engineering (SE). © 2025 Elsevier B.V.
Optimization of Quantum Capacitance of Functionalized VS2 Monolayer Electrodes to Shrink Hybrid Supercapacitors for On-Chip Energy Sources
(American Chemical Society, 2025) Yadav, A.K.; Thiyyakkandy, J.; Singh, R.; Das, P.P.; Ajith, K.M.; Pandey, S.K.
Quantum capacitance (CQ) of the electrodes plays an important role in enhancing the performance of supercapacitors by directly affecting the overall capacitance. In this study, several approaches including doping, creating vacancy, and adsorption have been used to enhance the CQ of the vanadium disulfide (VS2) electrode using density functional theory calculation. The undoped VS2 monolayer shows a maximum CQ value of 20.19 ?F/cm2. After creating V-vacancy (Vv) in the VS2 monolayer lattice, the CQ value increased to 35.61 ?F/cm2, which is the highest among all doped and defective VS2 lattices at room temperature. When we use VS2 electrodes for supercapacitors, generally ion adsorption occurs at the electrode surface, showing the necessity to investigate the adsorption of alkali/alkaline atoms (Li, Na, K, and Mg) at the VS2 surface to know the change in different properties of the electrode. It is found that generally CQ reduces due to the adsorption of alkali/alkaline atoms at the surface, but the K-adsorption at S-vacancy (Vs) VS2 demonstrated the increment of CQ value from 21.75 to 35.32 ?F/cm2 at room temperature. Additionally, the variation of the adsorption distance of the K atom at the Vs-VS2 surface revealed an optimum distance of value 3.5 Å, indicating that the K atom (radius = 2.43 Å) stabilizes just above the VS2 surface. Moreover, augmentation in CQ was seen with a decrease in temperature and attained a value of 49.96 ?F/cm2 at 100 K. The calculated CQ and open-circuit voltage (OCV) duly confirmed that the K-adsorbed Vs-VS2 is a potential candidate for the anode of hybrid supercapacitors as it has a maximum CQ value at the positive side of the electrochemical potential and an average OCV value of +0.615 V. This study reveals that the CQ of the VS2 electrode can be increased to minimize the size of high-performance hybrid supercapacitors for its application as an on-chip energy source. © 2025 American Chemical Society.