Faculty Publications
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Item Ionic conductivity and dielectric studies of acid doped cellulose acetate propionate solid electrolyte for supercapacitor(John Wiley and Sons Inc, 2016) Sudhakar, Y.N.; Bhat, D.; Muthu, M.Phosphoric acid doped cellulose acetate propionate (CAP) consisting of poly(ethylene glycol) (PEG) as plasticizer was investigated. Ionic conductivities and dielectric studies were carried at different temperature with varying concentration of H3PO4 using AC impedance method. The highest conductivity was 8.1 × 10-4 S cm-1 at 343 K and a long tail was featured in dielectric studies indicating good capacitance nature of the electrolyte. Interactions between added constituents were observed in FTIR and differential scanning calorimetry studies. Thin and compact fabricated supercapacitor demonstrated specific capacitance of 64 F g-1 using cyclic voltammetry. Furthermore, the supercapacitor properties like AC impedance and charge-discharge were studied. Stability was up to 96% at 1000th cycle. POLYM. ENG. SCI., 56:196-203, 2016. © 2015 Society of Plastics Engineers.Item Integer and fractional order-based viscoelastic constitutive modeling to predict the frequency and magnetic field-induced properties of magnetorheological elastomer(American Society of Mechanical Engineers (ASME), 2018) Poojary, U.R.; Gangadharan, K.V.Magnetorheological elastomer (MRE)-based semi-active vibration mitigation device demands a mathematical representation of its smart characteristics. To model the material behavior over broadband frequency, the simplicity of the mathematical formulation is very important. Material modeling of MRE involves the theory of viscoelasticity, which describes the properties intermediate between the solid and the liquid. In the present study, viscoelastic property of MRE is modeled by an integer and fractional order derivative approaches. Integer order-based model comprises of six parameters, and the fraction order model is represented by five parameters. The parameters of the model are identified by minimizing the error between the response from the model and the dynamic compression test data. Performance of the model is evaluated with respect to the optimized parameters estimated at different sets of regularly spaced arbitrary input frequencies. A linear and quadratic interpolation function is chosen to generalize the variation of parameters with respect to the magnetic field and frequency. The predicted response from the model revealed that the fractional order model describes the properties of MRE in a simplest form with reduced number of parameters. This model has a greater control over the real and imaginary part of the complex stiffness, which facilitates in choosing a better interpolating function to improve the accuracy. Furthermore, it is confirmed that the realistic assessment on the performance of a model is based on its ability to reproduce the results obtained from optimized parameters. © © 2018 by ASME.Item Effect of grain refinement on material properties of Mg-8%Al-0.5%Zn alloy after the combined processes of multi-direction forging and equal channel angular pressing(Institute of Physics, 2019) Naik, G.M.; Anjan, B.N.; Narendranath, S.; S Satheesh Kumar, S.; Preetham Kumar, G.V.Establishing the novel microstructure is an effective method to accelerate the applications of magnesium and its alloys. In this work, an Mg-8%Al-0.5%Zn alloy (AZ80 Mg) with ultra-fine-grain (UFG) size of ?1.29 ?m was achieved by the combined processes of multi-directional forging (MDF) and equal channel angular pressing (ECAP). The achieved ultra-fine grain structure made the Mg alloy, owing to inclusive performance as the structural material. The AZ80 Mg alloy with MDF 6 pass followed by two pass ECAP has superior mechanical properties such as ultimate tensile strength (UTS) of 352 MPa and elongation of 11% when compared to as-received Mg alloy. Also, an unprocessed Mg alloy showed the corrosion rate of a 13.28 mm y?1, the corrosion rate of processed Mg alloy could be further decelerated through a change of microstructure obtained from combined processes of MDF and ECAP. This study outstandingly obtained a 94% reduction of corrosion rate after MDF-3P followed by an ECAP-2P (0.77 mm y?1) process compared to as-received Mg alloy. © 2019 IOP Publishing Ltd.Item Effect of zirconium on the properties of polycrystalline Cu-Al-Be shape memory alloy(Elsevier Ltd, 2019) Bala Narasimha, G.; Murigendrappa, S.M.This paper presents an investigation of the effect of zirconium on the properties of polycrystalline Cu-Al-Be shape memory alloy. Mechanical and shape memory properties have been evaluated by varying the compositions of Zr to Cu88.13-Al11.42-Be0.45 alloy ranging from 0.05 to 0.4 wt% with step 0.1 wt%. The results unveil reduction in the grain size of 89.18% with the improved tensile strength of 667 ± 30 MPa and ductility of 23.95 ± 0.86% and excellent shape recovery ratio of 100% with the addition of Zr up to 0.3 wt%. Increase in transformation temperatures is observed with the addition of Zr. © 2019 Elsevier B.V.Item Solar-metallicity gas in the extended halo of a galaxy at z ? 0.12(Oxford University Press, 2020) Pradeep, J.; Sankar, S.; Umasree, T.M.; Narayanan, A.; Khaire, V.; Gebhardt, M.; Sameer; Charlton, J.C.We present the detection and analysis of a weak low-ionization absorber at z = 0.121 22 along the sightline of the blazar PG 1424+240, using spectroscopic data from both HST/COS and STIS. The absorber is a weak Mg II analogue, with an incidence of weak C II and Si II, along with multicomponent C IV and O VI. The low ions are tracing a dense (nH ? 10?3 cm?3) parsec-scale cloud of solar or higher metallicity. The kinematically coincident higher ions are either from a more diffuse (nH ? 10?5–10?4 cm?3) photoionized phase of kiloparsec-scale dimensions or are tracing a warm (T ? 2 × 105 K) collisionally ionized transition temperature plasma layer. The absorber resides in a galaxy overdense region, with 18 luminous (>L?) galaxies within a projected radius of 5 Mpc and velocity of 750 km s?1. The multiphase properties, high metallicity, and proximity to a 1.4L? galaxy, at ? ? 200 kpc and separation |v| = 11 km s?1, favour the possibility of the absorption tracing circumgalactic gas. The absorber serves as an example of weak Mg II–O VI systems as a means to study multiphase high-velocity clouds in external galaxies. © 2020 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical SocietyItem Development of corrosion-resistant Ni–Mo coatings from low-concentration bath: effect of magnetoconvection(Taylor and Francis Ltd., 2021) Gonsalves, C.N.; Hegde, A.C.The phenomenon of magnetoconvection has been used effectively to improve the corrosion protection efficacy of Ni–Mo coatings from a low-concentration bath. Experimental studies demonstrated that magnetoelectrodeposited (MED) coatings developed under parallel (Item Bimetallic nanoparticles grafted ZnO hierarchical structures as efficient visible light driven photocatalyst: An experimental and theoretical study(Elsevier B.V., 2021) Shenoy, S.; Tarafder, K.; Sridharan, K.Bimetallic nanoparticles (NPs) exhibiting novel properties due to synergy between the individual elements have sparkled significant interest as a co-catalyst in enhancing the photocatalytic efficiency of semiconductor materials. Here, we report the photocatalytic activity of NiAg NPs embedded on hierarchical ZnO structures (NiAg-ZnO). Structural and morphological investigations through X-ray diffraction and scanning electron microscopy confirmed the formation of NiAg-ZnO. UV-Vis diffuse reflectance spectroscopy revealed the decrease in the bandgap energy of NiAg-ZnO (2.65 eV) in comparison to pristine ZnO (3.1 eV). Interestingly, the rate of photodegradation of methylene blue and rhodamine B dye molecules under visible light irradiation are two to three times enhanced with NiAg-ZnO in comparison to Ag-ZnO. Enhanced visible light absorption and effective charge separation due to the synergistic metal-semiconductor interface formed by the embedment of NiAg bimetallic NPs on ZnO led to the improved photocatalytic activity. Experimental results are further confirmed through the first principle electronic band structure calculations. © 2021Item Graph representational learning for bandgap prediction in varied perovskite crystals(Elsevier B.V., 2021) Omprakash, P.; Manikandan, B.; Sandeep, A.; Shrivastava, R.; Viswesh, P.; Bhat Panemangalore, D.B.Perovskites are an important class of materials that are actively researched for applications in solar cells and other optoelectronic devices due to their ease of fabrication and tuneable bandgaps. High throughput computational techniques like Density Functional Theory (DFT) and Machine Learning (ML) are viable methods to accelerate discovery of new perovskite materials with favourable properties. ML specifically is faster and requires lesser computational power. We recognized the importance of having robust datasets for ML and hence collated a dataset of varied perovskite structures along with their indirect bandgaps. We employed a graph representational learning technique and trained a model that predicted bandgaps for all types of perovskites. The model has a mean absolute error of 0.28 eV and can predict bandgap in a few milliseconds. The metric of generalization gap is introduced to quantify the performance of ML models. This metric will help in building more generalized models that can predict properties for novel materials. Furthermore, we believe that these computational techniques should be user-friendly to those less experienced in the field. Hence, for researchers unacquainted with DFT or ML, we built a pipeline that abstracts the specific processes. This makes it easier for material scientists to quickly screen viable inorganic perovskite compounds allowing them to synthesize and experiment on the more promising compounds. © 2021 Elsevier B.V.Item The utility of proper orthogonal decomposition for dimensionality reduction in understanding behavior of concrete(Techno-Press, 2021) Manoj, A.; Babu Narayan, K.S.B.Properties of wet and set concrete are influenced by a wide range of variables. With new formulations being tried and adopted, understanding workability, strength and durability characteristics of these formulations is of utmost importance. From among the wide range of variables that affect properties of concrete, identification of the most vital, interplay between variables, quantification of influence, for judicious manipulation of mix proportioning, placement, compaction and curing, to get the desired and targeted end results can vastly be improved by employing the state of the art data handling tools. Group method of data handling (GMDH), a set of mathematical algorithms, is of great usage potential in multi-variable data modeling, optimization and pattern recognition. Proper Orthogonal Decomposition (POD) a subset of GMDH, a technique for systematic dimensionality reduction and pattern recognition, is of great importance in studying complex datasets. This paper presents the need for adoption of GMDH techniques in concrete technology with an account of trends in this direction and also provides an illustration of POD’s utility as a valid decision-making tool in dimensionality reduction and projection of behavior of concrete subjected to elevated temperature. © 2021 Techno-Press, Ltd.Item Biodegradation of PEEK Piston Rings(Elsevier Ltd, 2021) Shetty, P.; Dsilva, P.; Sondar, P.R.; Kumar, B.G.; Hegde, S.Polyether ether ketone (PEEK) is considered a high performance thermoplastic with excellent mechanical, chemical, and thermal properties. It is generally believed that this material is chemically and biologically inert, and is used for various biomedical and industrial applications, especially in the form of fiber reinforced polymeric composites. Contrary to the general belief, the present work reports the biodegradation of PEEK piston rings that were used in a reciprocating CO2 compressor. A series of circumstantial and direct evidences were collected by following various tests and characterization methods to confirm the degradation of the piston rings by bacterial attack. The bacterial cells were extracted from the degraded piston rings, cultured in agar medium and then studied using scanning electron microscope. An experimental simulation was carried out by depositing and incubating a bacterial culture on the pristine surface of a PEEK specimen. The simulation experiment revealed an early stage of bacterial degradation in the form of cracking of the PEEK specimen surface. The results of various tests, characterization, and the experimental simulation presented in the paper suggest that PEEK based composites degrade due to enzymatic hydrolysis process by Myxococcus Xanthus, the rod–shaped soil bacteria. © 2021