Faculty Publications
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Item Evolutionary algorithm based structure search and first-principles study of B12C3polytypes(Elsevier Ltd, 2017) Harikrishnan, H.; Ajith, K.M.; Chandra, S.; Mundachali Cheruvalath, V.The structure search based on evolutionary algorithm has yielded six unique Boron Carbide structures in B12C3stoichiometry, three of them with negative formation energies. Their formation energies lie within a band of 166 meV/atom, so they can be formed together in any optimal high temperature synthesis of B12C3and they are thermodynamically stable at temperatures up to 660 K. This work is the first independent confirmation using structure search that B11Cp(CBC) is the ground state structure of B12C3stoichiometry. New structures like the 14-atom-cage and the supercell (B11Cp)(B10Cpe 2)(CBC)(CBB) have also emerged in the structure search. Five structures have base-centered monoclinic symmetry and the supercell has triclinic symmetry, implying that the determination of monoclinic symmetry in B12C3by experimental measurements is an option for further inquiry. The mechanical stability of these systems are established through the analysis of their elastic constants and their dynamical stability from the phonon data. The high value of Bulk modulus (?250 GPa) indicates their high hardness and the B/G value confirms their brittle nature. The electronic structure shows that they are semiconductors with a significant reduction in the band gap when the structure does not contain the CBC chain. The curve fitting of the cumulative IR spectrum against the experimental spectrum implies that the presence of B11Cp(CBC) in the ground state composition could mostly be through structures of larger unit cells. The hardness values of these systems estimated by using the semi-empirical model based on bond strength are in excellent agreement with the experimental values. For the four structures with chain the hardness values are close to the superhard regime (>40 GPa). © 2016 Elsevier B.V.Item Semiconducting B13C2 system: Structure search and DFT-based analysis(Institute of Physics, 2019) Pillai, H.G.; Madam, A.K.; Chandra, S.; Cheruvalath, V.M.DFT calculation on Boron Carbide in B13C2 stoichiometry using a 15-atom unit cell necessarily results in metallic ground state regardless of the crystal structure. This is because such a unit cell consists of odd number of electrons, and hence complete filling of the top most band(s) of nonzero occupancy is impossible. This is in contrast to the observed semiconducting nature. If the crystal structure of B13C2 is made of a 30-atom unit cell which cannot be reduced to a 15 atom cell, there is a possibility of obtaining either a metallic or a semiconducting state as such a cell consists of an even number of electrons. In this work the evolutionary algorithm based structure search using 30-atom unit cells has yielded a previously unreported semiconducting system of B13C2 with unique bonding pattern. The mechanical and dynamical stability of the system have been properly established through the computation of elastic constants and phonon spectra. Its bond lengths, elastic moduli, hardness and infrared spectrum are in good agreement with experimental data. ©2019 IOP Publishing Ltd.Item Stone-Wales Defect Induced Performance Improvement of BC3 Monolayer for High Capacity Lithium-Ion Rechargeable Battery Anode Applications(American Chemical Society, 2020) Thomas, S.; Madam, A.K.; Asle Zaeem, M.A.First-principles density functional theory (DFT) computations were adopted to assess the potential application of a boron carbide (BC3) monolayer with point and topological defects as an anode material in alkali metal-based lithium (Li) ion rechargeable batteries. Results show that point defects (mono and bi vacancies) induce a large structural deformation upon Li intercalation which restricts their use for anode application. However, the Stone-Wales defect filled BC3 monolayer shows high structural stability with a negative Li binding energy of -1.961 eV in comparison with -0.930 eV of its pristine form. It is also noticed that after adsorbing the Li atom, the semiconducting characteristics of both the pristine and Stone-Wales defect filled BC3 monolayers are transformed into metallic, electrically conductive states. More importantly, the Li alkali metal atom shows fast diffusion on the surfaces of both the pristine and the Stone-Wales defect filled BC3 monolayers with low energy barriers of 0.34 and 0.33 eV, respectively. Besides, both the pristine and Stone-Wales defect filled BC3 monolayers exhibit high theoretical specific capacities of 1144 and 1287 mAhg-1, which are much higher than that of a traditional graphite anode and stand among the highest values of anode materials detailed in literature. The Li alkali metal intercalated monolayers BC3 show small average open-circuit voltages of 0.485 and 0.465 V for pristine and Stone-Wales defect cases, respectively. On the basis of the aforementioned details, the present study suggests that the Stone-Wales type topological defect incorporated BC3 monolayer is a promising anode material for Li-ion based rechargeable batteries with high storage capacity, low Li diffusion energy barrier, and low average open-circuit voltage. © 2020 American Chemical Society.Item Anharmonicities in the temperature-dependent bending rigidity of BC3 monolayer(Elsevier Ltd, 2020) Mrudul, M.S.; Thomas, S.; Ajith, K.M.The present work investigated the temperature-dependent thermodynamic and structural characteristics of graphene-like monolayer boron carbide (g-BC3) using classical molecular dynamics simulations. Herein, we mainly focused on the temperature dependence of mean square displacement of thermally stimulated ripples and bending rigidity of g-BC3. We observed that at high temperatures, the specific heat capacity at constant volume exhibits a significant increase beyond the limit of Dulong-Petit value due to the presence of anharmonicity in the g-BC3. Besides, the linear thermal expansion coefficient is found to be negative owing to the excitation of low-frequency bending vibrations in the out-of-plane orientation. Studies reveal that the out-of-plane of height fluctuations and bending rigidity are fully dependent on temperature and are described using the continuum theory of membranes. Moreover, the study on the height fluctuation and correlation shows variation from the estimation of the harmonic theory of membranes as a consequence of the anharmonic features of g-BC3. We believe that our study will provide a notable contribution to numerous applications of g-BC3 including nanoelectromechanical (NEMS) devices to become a reality. © 2020 Elsevier LtdItem Optimization of Wear Properties of B4C Nanoparticle-Reinforced Al7075 Nanocomposites Using Taguchi Approach(Springer, 2023) Kumar, G.A.; Satheesh, J.; Murthy, K.V.S.; Mallikarjuna, H.M.; Puneeth, N.; Koppad, P.G.In the present work, Al7075 nanocomposites with varying B4C contents were produced using powder metallurgy technique. The developed nanocomposites were subjected to microstructure, grain size and wear behaviour analysis. Dry sliding wear test of nanocomposites was conducted as per ASTM G99 standard using pin on disc test ring using Taguchi L9 approach with varying B4C nanoparticles (2.5, 5 and 10%), load (10, 20 and 30 N), speed (200, 250 and 300 rpm) and sintering temperature (500, 550 and 600 °C). Scanning electron microscopy (SEM) analysis showed uniform dispersion and good bonding between B4C nanoparticles and Al7075 matrix. Grain size analysis conducted according to ASTM E112-96 showed that irrespective of sintering temperature the average grain diameter of nanocomposites decreased as the B4C nanoparticle content increased. According to response table for S/N ratio, the most influential parameter on wear volume was B4C nanoparticles content. Worn surface analysis showed delamination and abrasion as dominant mechanisms for nanocomposites with lower B4C nanoparticle content and abrasion for nanocomposites with higher B4C nanoparticle content. © 2022, The Institution of Engineers (India).Item Optimization of process parameters for friction stir processing (FSP) of AA8090/boron carbide surface composites(Springer Science and Business Media Deutschland GmbH, 2024) Adiga, K.; Herbert, M.A.; Rao, S.S.; Shettigar, A.K.Friction Stir Processing (FSP) is an innovative and promising technique for microstructure refinement, material property enhancement, and surface composite production. The current study describes the fabrication of AA8090/boron carbide surface composites (SCs) by FSP. Experimental studies were conducted by varying the FSP parameters, specifically the rotational speed (800–1400 rpm), traverse speed (25–75 mm/min), and groove width (1–1.8 mm). Ultimate Tensile Strength (UTS), Surface Roughness (SR), and Percentage Elongation (El) were used as response measures. Experiments were planned based on the central composite design (CCD) of Response Surface Methodology (RSM) and a mathematical relationship between the input parameters and UTS, SR and El, and were obtained by RSM. The model adequacy was tested using analysis of variance (ANOVA). The models enabled the examination of individual and interaction effects of input parameters on the UTS, SR, and El of the produced SCs. AA8090/boron carbide SC strength was optimal of 366 MPa at 800 rpm, 75 mm/min, and 1.8 mm and optimal 21.13% elongation at 1400 rpm, 25 mm/min, and 1 mm. A smoother surface with 0.82-μm roughness was optimal at 1400 rpm, 25 mm/min, and 1.2 mm. The present study uses the FSP method to synthesize near-net-shaped SCs without further machining by systematically selecting process parameters. The study shows that the increase in rotational speed during AA8090/boron carbide SC fabrication produces composites with a good surface finish, lower UTS, and good ductility. However, the increase in the other two parameters, namely, traverse speed and groove width, produces low ductile composites with rougher surfaces and higher strengths. Graphical abstract: (Figure presented.) © International Institute of Welding 2024.Item Optimization of the Properties of Functionalized BC3 Monolayer for Superior Electrode of Solid-State Sodium-Ion Batteries(John Wiley and Sons Inc, 2025) Vudumula, K.; Yadav, A.K.; Maurya, G.K.; Singh, R.; Nikhil, K.S.; Pandey, S.K.Solid-state batteries offer superior safety, high energy density, and the ability to function effectively across a wide range of temperatures. Sodium-ion (Na-ion) solid-state batteries are a promising alternative to lithium-ion batteries due to sodium's abundance and low cost. A high-quality electrode is crucial for achieving high performance in Na-ion batteries. In this study, structural stability, electronic properties, and performance of functionalized hexagonal boron carbide (BC3) are investigated for ultrathin electrodes using density functional theory (DFT). The effective adsorption of Li, Na, K, and Mg atoms at the BC3 surface is also investigated. The BC3 monolayer has a ?0.8 eV indirect bandgap, which becomes metallic after Na adsorption, making it suitable for electrode applications. Additionally, the Na-adsorbed BC3 monolayer shows the lowest adsorption energy (?1.2 eV), which is the most stable lattice structure among others. The Na-adsorbed BC3 demonstrated a theoretical capacity of 1152 mAh g?1, which is comparable with the Li-adsorbed electrode. Moreover, the Na-adsorbed BC3 electrode shows a very small variation (0.18 V) for open circuit voltage (OCV), indicating this electrode is robust in terms of voltage stability. These findings show that the functionalized BC3 ultrathin electrode is very suitable for the electrode of Na-ion solid-state batteries. © 2025 Wiley-VCH GmbH.Item Tribological performance and 3-D surface characterisation of age-hardened Al2090-based ceramic composites(SAGE Publications Ltd, 2025) Sharath, B.N.; Mahesh, V.; Mahesh, V.; Kattimani, S.; Harursampath, D.This study investigates the synergistic influence of boron nitride (BN) tertiary ceramic additives and age-hardening treatment on the microhardness and wear resistance of Al2090-based hybrid composites, fabricated using the stir casting method. X-ray diffraction (XRD), scanning electron microscopy (SEM), and atomic force microscopy (AFM) studies are carried out to assess the phases present, microstructure, and surface properties, respectively. The metallurgical investigations confirm a relatively superior uniformity in the distribution of particles and the ageing of precipitation at 150°C, vis-à-vis the other temperatures explored in this study. The experimental examinations conducted as per ASTM (E8 and G99) standards revealed a significant improvement in both the hardness and the primary tribological properties, when micron-sized boron carbide, graphite, and boron nitride were used as reinforcements. Age-hardened samples, especially the hybrid composite HS-2 with 5 wt.% each of boron carbide, graphite, and boron nitride, demonstrated an enhanced hardness of 25.23% and lower surface roughness (44.3 nm) compared to Al2090 (AS), due to the presence of load-bearing ceramic reinforcements. Increasing the applied load led to higher wear rates and coefficients of friction for Al2090. However, heat-treated hybrid metal matrix composites (HMMCs) exhibited a contrary behaviour, suggesting enhanced durability. The investigation highlighted the better wear resistance of heat-treated and near-optimally reinforced HMMCs, indicating their potential candidature for wear-resistant aerospace applications. © IMechE 2025.Item On enhancing the high-temperature wear behaviour of Al2090-based hybrid composites using tertiary ceramic particles(SAGE Publications Ltd, 2025) Sharath, B.N.; Mahesh, V.; Mahesh, V.; Kattimani, S.; Harursampath, D.This study explores the impact of reinforcing an Al2090 matrix with silicon nitride (Si3N4) as a tertiary ceramic alongside boron carbide (B4C) and graphite (Gr) to improve wear resistance at elevated temperatures. Hybrid composite samples were produced using the stir-casting technique. Experimental results show that incorporating Si3N4increased hardness by 35.7%, while wear resistance improved by 43.7% with a combined reinforcement of B4C, Gr, and Si3N4at 18 wt.%. Scanning electron microscopy (SEM) revealed the formation of a mechanically mixed layer (MML) composed of B4C, Gr, and Si3N4, which acted as an effective insulating barrier, protecting the sample surface from the steel disc. A noteworthy 69% of wear resistance improvement was accomplished at 300 °C for the composite with 9 wt.% B4C, 6 wt.% Gr, and 3 wt.% Si3N4. Atomic force microscopy (AFM) analysis further indicated enhanced surface properties for this composition. These findings highlight the potential of this hybrid composite for high-temperature aerospace applications, such as in engines, heat shields, and structural components. © IMechE 2024Item Optimization of Processing Parameters and Wear Performance of B4C Reinforced AA6061 Composites Through Taguchi Methodology(Springer, 2025) Manjunatha, C.; Varun, K.R.; Nagaraja, K.C.; Soni, P.K.; Kumar, R.S.; Prasad, C.; Kumar, P.; Nithesh, K.G.Two or more elements with different physical and chemical characteristics make up the composite material. The composite may be prepared using a variety of methods, but stir casting is a popular choice since it is easy to use and reasonably priced. In this investigation, stir casting was used to create AA6061-Boron Carbide (B4C) composites. Composites with 10% weight percentage of B4C were selected for wear analysis. The Taguchi technique was applied to the wear study in order to identify the ideal values. Utilizing a Pin-on-Disk testing device under dry sliding circumstances, anthropological investigations were carried out. With B4C content and wear depth as the system output, the three factors load (N), sliding distance (SD), and sliding velocity (SV) were evaluated using the L27 orthogonal array. To comprehend the impact of factors and how they contribute to wear loss, analysis of variance was used. Experimental tests were conducted to validate the analysis results using the optimal values. Scanning Electron Microscopic (SEM) analysis of the samples revealed both abrasive and adhesive wear on the contact surfaces of the specimens, aiding in understanding the wear mechanisms in the composites. © The Institution of Engineers (India) 2024.