Faculty Publications
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Item A comprehensive study on the structural, morphological, compositional and optical properties of ZnxCd1-xS thin films(Institute of Physics Publishing helen.craven@iop.org, 2019) Barman, B.; Bangera, K.V.; Shivakumar, G.K.The absorption loss in cadmium sulfide (CdS) thin films which are widely used as a window layer in a photovoltaic cell limits the efficiency of the device. This issue can be addressed by ZnxCd1-xS thin films due to its tunable band gap nature. Herein, the various composition of ZnxCd1-xS (x=0, 0.15, 0.30, 0.45, 0.70, 0.85, 1) thin films were grown by a vacuum thermal evaporation technique and the characteristics of the films were investigated by varying the composition 'x'. The x-ray diffraction (XRD) studies displayed that the as-deposited films consist of diffraction peaks from both CdS and ZnS lattice. The formation of ternary ZnxCd1-xS films was verified when the deposited films were subjected to an annealing treatment. The morphology of the films was analyzed using a scanning electron microscope (SEM) and it was observed that the films are uniform, homogeneous and free from any pin-holes and cracks. The presence of Zn, Cd and S elements were quantized using an energy dispersive spectroscopy. Optical studies showed a successful non-linear band gap engineering (2.42-3.49 eV) for the deposited ZnxCd1-xS thin films. All films showed a very high optical transmittance of above 70% in the visible wavelength region. © 2020 IOP Publishing Ltd.Item An Investigation on the Influence of Thermal Damage on the Physical, Mechanical and Acoustic Behavior of Indian Gondwana Shale(Springer, 2020) Srinivasan, V.; Tripathy, A.; Gupta, T.; Singh, T.N.In the present study, the effect of thermal treatment on the physical, mechanical and fracturing behavior of Gondwana shale samples from India was investigated. Acoustic Emission signals were used to identify the changes brought in by temperature variations on the crack damage zones and failure attributes in shale. The results suggested that mechanical parameters such as uniaxial compressive strength, tensile strength (?t), elastic modulus, mode-I fracture toughness (KIC), cohesion, and brittleness index (B1) exhibited a strong negative correlation with thermal damage (Dt). But, the internal angle of friction and brittleness index (B2) showed a reasonable positive relation with thermal treatment. The deformation of the shale was dominated by its clay mineral enrichment, the characteristics of which changed with heating. The intensity of fracturing as observed from acoustic signals was chiefly controlled by the orientation of bedding planes and the degree of thermal treatment. The initiation and propagation of macro-crack were found to be greatly influenced by the degree of thermal damage. Under compression, thermally damaged samples showed similar deformation pattern, while under Brazilian tensile load, the deformation path became inconsistent with increasing temperatures. It was observed that thermal damage in tested shale decreased the layer compaction, which eased the fracturing intensity, thereby reducing the overall strength of the samples. The present investigation concludes that even a slight change of the thermal conditions can substantially alter shale fracturing behavior and failure attributes posing serious safety concerns of deep geo-engineering structures. © 2020, Springer-Verlag GmbH Austria, part of Springer Nature.Item Ultralow Lattice Thermal Conductivity and Enhanced Mechanical Properties of Cu and Sb Co-Doped SnTe Thermoelectric Material with a Complex Microstructure Evolution(American Chemical Society, 2022) Kihoi, S.K.; Shenoy, U.S.; Kahiu, J.N.; Kim, H.; Bhat, D.K.; Lee, H.S.SnTe is an exceptionally promising eco-friendly thermoelectric material that continues to draw immense interest as a source of alternative energy recovered from waste heat energy. Here, we investigate the effect of introducing Cu as a single doping element rather than phase separated in SnTe followed by Sb co-doping to tune the lattice thermal conductivity. A microstructure evolution was observed which influences the thermoelectric performance of these SnTe-based materials. An overall power factor of ∼22 μW/cmK2 and an ultralow lattice thermal conductivity of 0.39 W/mK are reported. A maximum ZT of 0.86 is also reported with an all-time record high hardness value of 165 Hv among SnTe-based thermoelectric materials. Through DFT calculations, we show that Cu opens the band gap of SnTe, whereas Sb in the presence of Cu introduces resonance levels and causes band convergence. This kind of enhanced thermoelectric performance is paramount for the application of SnTe in recovery of heat into useful electrical energy. © 2022 American Chemical SocietyItem Experimental study on failure and fracturing attributes of granite after thermal treatments with different cooling conditions(Elsevier B.V., 2022) Srinivasan, V.; Hasainar, H.; Singh, T.N.Thermal damage is one of the fundamental mechanisms affecting the stability of rocks encountered in many deep geo-engineering ventures such as nuclear waste isolation, geothermal extraction etc. In the present study, the findings on influence of heating and subsequent cooling conditions on the fracturing and mechanical behaviour of an Indian granite are discussed. The granite samples from Jalore region of India were heated from room temperature to 600 °C followed by slow cooling and water quenching treatments. It was observed that rapid cooling through quenching had a greater impact on strength, elastic properties than slow cooling rate. Moreover, a drastic shift in terms of fracturing thresholds was witnessed, as a function of both temperature and sudden thermal shock experienced by rock at higher cooling rate. The simultaneous AE monitoring results suggested an early crack damage at higher thermal regimes. With help of microscopic observations, it was observed that inter-granular crack boundaries widened with increasing thermal damage experienced by minerals under both cooling conditions. However, the fracturing process was intense under rapid cooling treatment due to the invasion of water due to quenching which accelerated severe intra-crack growths, especially at higher thermal stress because of the rapid cooling rate than the slow cooling. The increased intensity of thermal cracks with temperatures and with variation in cooling rate was inferred as the primary reason for decay of rock characteristics. This was very well supplemented by decay in strength properties and changes in fracturing attributes of the tested granite as inferred from acoustic monitoring. © 2022Item A review study of thermal conductivity and influencing physico-mechanical properties of rocks(Inderscience Publishers, 2023) Dileep, G.; Tripathi, A.K.; Murthy, C.S.N.; Pal, S.K.Geothermal exploration and heat flow studies rely heavily on rock's thermal conductivity, and it controls the subsurface temperature distribution. A broad study of rock thermal properties has become progressively indispensable for geotechnical, civil, mining, and tunnel engineers. The thermal properties of rocks are essential to the ground modification technique of geothermal heat pumps, environmentally conscious projects like dumping high-level nuclear waste in underground sites, and a wide range of engineering projects. The steady-state technique is commonly employed for homogeneous materials, providing a more precise thermal conductivity value despite longer testing times. Conversely, the transient technique is preferred for heterogeneous materials with moisture content, considering this factor but requiring multiple tests to achieve accurate results. This paper explores the predominant approaches used to measure rock thermal conductivity and identify the factors that influence it. Additionally, researchers present a generic equation for predicting the thermal conductivity of rocks using data they have gathered. According to this article, the thermal conductivity of rocks is influenced by several factors such as porosity, density, pressure, moisture content, variations in mineral composition, temperature, and more. © 2023 Inderscience Enterprises Ltd.Item MULTIDIMENSIONAL INVESTIGATION OF THERMAL BEHAVIOR OF HIGH-POWER ELECTRIC VEHICLE MOTOR DURING ON-ROAD DRIVING CONDITIONS THROUGH ELECTROMAGNETIC, THERMAL, AND DRIVE CYCLE ANALYSIS(Begell House Inc., 2024) Chauhan, V.K.S.; Koorata, P.K.This study addresses the critical need to understand the thermal behavior of electric motors in real-world driving conditions, which is crucial for the global transition to electric vehicles (EVs) and for achieving sustainable energy goals. The real-world driving conditions include acceleration and deceleration, resulting in speed variations, and existing research often limits its scope to constant speed conditions, potentially providing misleading results. As existing research predominantly confines itself to constant speed conditions, our study fills this gap by investigating temperature variations during on-road driving scenarios, utilizing the SAE J227 drive cycle as a benchmark. Based on recent studies, we consider the design parameters of an appropriate EV motor and subject the developed model to thermal and fluid flow analyses. The impact of confinement on motor temperature rise is also explored for potential temperature reduction, contributing up to 4 percent temperature reduction. The drive cycle–based study indicated that running the motor at a constant speed yields a considerably lower temperature rise (ΔT < 74°C) than actual driving conditions. In contrast, temperatures in actual driving scenarios could exceed 136°C within similar durations. This study looks into the actual heating challenges faced by electric motors used in EVs by integrating analyses from electrical, thermal, and transportation engineering. © 2024 by Begell House, Inc. www.begellhouse.com.Item Enhanced Electrical, Thermal, and Mechanical Properties of SnTe through Equimolar Multication Alloying for Suitable Device Applications(American Chemical Society, 2024) Kihoi, S.K.; Shenoy, U.S.; Kim, H.; Kahiu, J.N.; Kim, C.M.; Park, K.-I.; Bhat, D.K.; Lee, H.S.With the ever-growing demand for eco-friendly energy sources to mitigate the global rising temperatures, the universal insatiable need for sustainable and efficient energy sources are earnestly being intensively sought after. The ubiquitous heat within, if successfully tapped, is an utterly promising source of energy. To achieve this, a thermoelectric device (TED) is needed. To enhance the conversion efficiency from heat to useful electrical power, we developed a strategy to improve the thermoelectric performance of the materials involved. In this work, equimolar multication alloying (EMMCA) is proposed for the first time and employed to enhance the performance of SnTe-based thermoelectric materials. Beyond the cation’s solubility limit, in situ compositing is observed with an increasing doping ratio, whereby distinct CuInTe2 ternary second phases are dispersed within the SnTe matrix. The electronic properties of the ensuing alloy are significantly enhanced by the resulting carrier concentration modulation and the unique electronic band engineering. A decrease in the thermal transport properties is likewise reported, benefiting from enhanced phonon scattering and diminished electronic contribution. The mechanical properties are also shown to increase with increased alloying. As a result, single-leg TED performance shows substantial output power in comparison with the pristine sample. The outcomes stemming from EMMCA are documented as significantly impactful, contributing to superior overall thermoelectric performance. © 2024 American Chemical Society.Item Prediction of thermal conductivity of quartz chlorite schist rocks: a comparative study of MLR and ridge regression(Inderscience Publishers, 2025) Tripathi, A.K.; Pal, S.K.; Dileep, G.; Raj, A.Thermal conductivity is a key physical property with broad applications in engineering and geosciences, particularly in energy-efficient building design, geothermal energy systems, and subsurface geological studies. Accurate determination of thermal conductivity is essential for understanding heat transfer mechanisms in rock materials. However, direct in-situ measurement is often impractical due to technical and logistical constraints. As a result, indirect estimation methods, which establish empirical relationships between thermal conductivity and various physico-mechanical properties, have gained attention. This study investigates the thermal conductivity of quartz chlorite schist through laboratory experiments, alongside measuring key physico-mechanical properties, including P-wave velocity, porosity, density, and uniaxial compressive strength (UCS). The objective is to analyse the correlations between thermal conductivity and these properties to develop a reliable predictive model. Multiple regression and ridge regression analysis are employed to derive an empirical equation for estimating thermal conductivity based on the measured parameters. The findings of this study contribute to improving indirect assessment techniques, which are valuable for geotechnical and geological applications where direct measurements are challenging. © © 2025 Inderscience Enterprises Ltd.Item Thermoelastic buckling and vibration analysis of shear and normal deformable three-phase bio-inspired composite beams under axially varying temperature fields(Springer, 2025) Patil, H.H.; Pitchaimani, J.The thermoelastic buckling and free vibration behaviors of a Three-Phase Composite (TPC) beam subjected to axially varying Non-Uniform Temperature (NUFT) fields is investigated by incorporating Temperature-Dependent (TD) elastic properties of both Carbon Nanotubes (CNTs) and the matrix. The Shear and Normal Deformable Beam Theory (SNDBT) is used to model the kinematics, and the governing equations are formulated through Hamilton’s principle and solved using the Ritz method. TD elastic properties of CNTs are accounted in terms of TD Hill’s constants. Dispersion issue of CNT is accounted in terms of partial and complete agglomeration effects for more realistic material modeling. The results indicate that the area beneath the NUFT distribution profiles serves as a meaningful parameter for interpreting both the critical buckling temperature (?Tcr) and the induced axial membrane force (N). NUFT-induced differential thermal expansion generates localized thermal strain variations, and the strain reverses its sign whenever the temperature at a point exceeds the spatially averaged temperature for the given NUFT. Consideration of thickness-stretching deformation (Wz) produces noticeable changes in ?Tcr and the fundamental frequency (?1), particularly for the beams with lower aspect-ratio, emphasizing its necessity in thick-beam modeling. The findings provide practical guidance for the design of lightweight, thermally stable composite structures deployed in aerospace and other thermal-environment-critical engineering systems. © The Author(s), under exclusive licence to Springer-Verlag GmbH Austria, part of Springer Nature 2025.Item Establishing high temperature tribological performance and wear mechanism map of engineered in-situ TiB2 reinforced Mg-RE metal matrix composites(Elsevier Ltd, 2025) Sahoo, S.K.; Ramesh, M.R.; Panigrahi, S.K.The high temperature sliding wear behavior of microstructurally engineering in-situ sub-micron sized TiB2 reinforced ZE41 composite was studied and compared with it's base counterpart at varying loading conditions. The wear mechanism maps were constructed by correlating the microstructures of worn surfaces with different test parameters. The severe and catastrophic wear mechanisms like delamination and melt wear were wider in base and composite, while in the case of engineered composite, these zones are significantly narrow down. Due to the presence of thermally stable in-situ TiB2 particles and bimodal precipitates in engineered composite, the material showed sufficient resistance against wear induced deformation. Furthermore, the study established scientific knowhow on high-temperature wear induced deformation behavior by analyzing microstructural evolution in wear subsurface zone. © 2024