Faculty Publications
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Publications by NITK Faculty
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Item Solar enhanced soaring: Tapping into ambient solar energy for optimized airfoil performance(Jenny Stanford Publishing, 2024) Akhtar, M.S.; Ting, D.S.-K.; Kalathi, J.T.The amount of solar and background radiation absorbed by birds varies according to their wing shape, pigmentation, porosity, etc. Birds are equipped with unique features to thrive, including attracting the opposite sex, regulating body temperatures, and soaring in the sky. The research focuses on solar/sky radiation 146by examining how the NACA0012 airfoil, representing the wing of a bird, performs when its upper surface temperature is higher or lower than the surrounding ambient air. This is realized by performing 2-dimensional simulations in OpenFOAM at a Reynolds number of 33,000, where the Spalart-Allmaras model is used to simulate the flow turbulence. The upper surface of the airfoil is warmed to 330 K and cooled to 270 K at a pressure of 1 atm, an ambient temperature of 300 K, and a Mach number of 0.0725. The results illustrate the airfoil with the cooler top surface exhibits a lower drag and higher lift than its warmer top surface counterpart. A maximum reduction of drag coefficient from 0.065 to 0.061 and an increase in lift coefficient from 0.89 to 0.93 at an angle of attack of 11° are achieved. In short, tuning the upper surface of the NACA0012 airfoil to temperatures lower than the ambient provides better aerodynamic performance. © 2024 Jenny Stanford Publishing Pte. Ltd. All rights reserved.Item Hybrid strategies for the treatment of latex-like wastewater from industries(Elsevier, 2024) Raagasweatha, R.K.; Ahamed, A.; Mahalingam, H.; Kalathi, J.T.Water, a vital part of daily life, is given special attention. Sadly, the wastewater generation rate is growing faster than its recycling rate due to various anthropogenic activities. The need for innovations in treating wastewater to meet freshwater requirements encourages the application of different advanced techniques in wastewater treatment. The advanced oxidation process, a tertiary treatment technique, has proven successful for many industrial effluent treatments. This chapter discusses the use of Fenton’s oxidation coupled with ultrasonication (US) as an efficient treatment for treating industrial wastewater containing emulsion polymers. The predominant presence of emulsion polymers in the untreated wastewater from industries, such as coatings and dispersions, creates a latex-like wastewater with characteristics similar to the latex wastewater produced in the rubber processing industries. This type of wastewater is typically characterized by very high TSS and COD values, thus making it impossible for conventional wastewater treatment plants to successfully reduce the COD/BOD values below acceptable discharge limits. In this chapter, an attempt is made to treat industrial wastewater samples containing emulsion polymers by combining sonolysis and Fenton oxidation. Photo-Fenton oxidation (PFO) and US techniques were carried out in different combinations, and the best COD reduction of ~97% was achieved by a combination featuring an initial 30min US (36kHz, 500W) followed by PFO (40min) and simultaneous US (36kHz) and PFO (40min). This corresponds to approximately 50% reduction in treatment time which can be deployed for treating latex-like wastewater in industries, whereas a COD reduction of 92% is achieved with PFO alone in 70min. However, the initial rate of COD reduction is more prominent with the combination of sonication. Hybrid processes such as US-PFO could be viable and effective options for achieving the best results in the treatment of industrial wastewater. © 2025 Elsevier Ltd. All rights reserved.Item Effects of Solvents on Structure, Morphology and Thermal Stability of Polystyrene-HNTs Nanocomposites by Ultrasound Assisted Solution Casting Method(Elsevier Ltd, 2017) Buruga, K.; Kalathi, J.T.Polymer-clay nanocomposites are extensively investigated as they are economical in comparison with other nanofillers and drastically enhances various physical and engineering properties of polymers. Among various clays used for polymer-nanocomposites, Halloysite nanotubes (HNTs) have gained tremendous attention as they have unique structure and properties. In the present work we have successfully synthesised polystyrene-HNT nanocomposites by ultrasound assisted solution intercalation method. In this method solvent plays a very crucial role in enhancing the overall properties of resultant nanocomposites as arrangement of filler in the polymer matrix depends upon how well the solvent is able to disperse filler which inturn enhances polymer properties. Hence in this work solvents toluene, benzene, chloroform, dichoromethane (DCM), tetrahydrofuran (THF) and carbontetrachloride (CCl4) were used for synthesis of nanocomposites and effect of these solvent on structure, morphology and thermal stability of nanocomposites was investigated. As per the characterization analysis, toluene was found to be the best solvent for synthesis of nanocomposites with enhanced properties and use of ultrasound aided in uniform distribution of clay in polymer matrix. Increase in basal spacing on sonication was revealed by x-ray diffraction (XRD) analyses. Scanning electron microscopy (SEM) results revealed uniform dispersion of filler inside the matrix on using acoustic cavitation as it promotes proportionate distribution of filler into the polymer matrix. Fourier transform and infrared (FT-IR) results confirmed encapsulation of HNTs into polymer. Differential scanning calorimetry (DSC) reports illustrated increase in glass transition temperature (Tg) on incorporating HNTs. © 2017 Elsevier Ltd.Item Ultrasound assisted Synthesis of Poly (styrene-Co-methylmethacrylate)-HNT's Nanocomposites by In-Situ Emulsion Copolymerization and its Characterization(Elsevier Ltd, 2017) Buruga, K.; Kalathi, J.T.Poly (styrene-co-methylmethacrylate)-HNT nanocomposites have been successfully synthesized by ultrasound assisted emulsion copolymerization without modification of HNT's. The key parameters that affect the stability of the emulsion and hence the properties of the resulting nanocomposites are sonication time and clay loading. The effectsof these parameters on the process were investigated in this study. Thesynthesized nanocomposites were characterized by scanning electron microscope (SEM), X-ray diffraction (XRD), Fourier transform and infrared spectroscopy (FT-IR) and differential scanning calorimetry (DSC) to investigatemorphology and thermal stability. The embodiment of the HNTs into the copolymer matrix was confirmed by FTIR, and XRD analyses positively delineated the complete exfoliation of HNTs into the copolymer matrix on sonication for 60 min. SEM analyses revealed homogenous dispersion of HNTs into the copolymer matrix and DSC analysis showed significant improvement in glass transition temperature (Tg)of composites upto 2 weight% of HNT loading and any further loading of HNT resulted in decrease in Tg.Zeta size and zeta potential analyses confirmed the particles were in nanoscale and possessed good stability respectively. This sonochemical route of preparation proves to be a promising way to accomplish nanocomposites synthesis with insitu polymerisation and to obtain better dispersion of particles in resulting composites. © 2017 Elsevier Ltd.Item Rouse mode analysis of chain relaxation in polymer nanocomposites(Royal Society of Chemistry, 2015) Kalathi, J.T.; Kumar, S.K.; Rubinstein, M.; Grest, G.S.Large-scale molecular dynamics simulations are used to study the internal relaxations of chains in nanoparticle (NP)/polymer composites. We examine the Rouse modes of the chains, a quantity that is closest in spirit to the self-intermediate scattering function, typically determined in an (incoherent) inelastic neutron scattering experiment. Our simulations show that for weakly interacting mixtures of NPs and polymers, the effective monomeric relaxation rates are faster than in a neat melt when the NPs are smaller than the entanglement mesh size. In this case, the NPs serve to reduce both the monomeric friction and the entanglements in the polymer melt, as in the case of a polymer-solvent system. However, for NPs larger than half the entanglement mesh size, the effective monomer relaxation is essentially unaffected for low NP concentrations. Even in this case, we observe a strong reduction in chain entanglements for larger NP loadings. Thus, the role of NPs is to always reduce the number of entanglements, with this effect only becoming pronounced for small NPs or for high concentrations of large NPs. Our studies of the relaxation of single chains resonate with recent neutron spin echo (NSE) experiments, which deduce a similar entanglement dilution effect. © 2015 The Royal Society of Chemistry.Item Nanoparticle Motion in Entangled Melts of Linear and Nonconcatenated Ring Polymers(American Chemical Society service@acs.org, 2017) Ge, T.; Kalathi, J.T.; Halverson, J.D.; Grest, G.S.; Rubinstein, M.The motion of nanoparticles (NPs) in entangled melts of linear polymers and nonconcatenated ring polymers are compared by large-scale molecular dynamics simulations. The comparison provides a paradigm for the effects of polymer architecture on the dynamical coupling between NPs and polymers in nanocomposites. Strongly suppressed motion of NPs with diameter d larger than the entanglement spacing a is observed in a melt of linear polymers before the onset of Fickian NP diffusion. This strong suppression of NP motion occurs progressively as d exceeds a and is related to the hopping diffusion of NPs in the entanglement network. In contrast to the NP motion in linear polymers, the motion of NPs with d > a in ring polymers is not as strongly suppressed prior to Fickian diffusion. The diffusion coefficient D decreases with increasing d much slower in entangled rings than in entangled linear chains. NP motion in entangled nonconcatenated ring polymers is understood through a scaling analysis of the coupling between NP motion and the self-similar entangled dynamics of ring polymers. © 2017 American Chemical Society.Item A facile synthesis of halloysite nanotubes based polymer nanocomposites for glass coating application(Elsevier Ltd, 2018) Buruga, K.; Kalathi, J.T.Halloysite-based polymethyl methacrylate (HNT-PMMA) and polystyrene (HNT-PS) nanocomposite coatings for glasses were synthesized by ultrasound-assisted solution blending method. The coatings were then dip-coated on four different types of soda-lime glass and the spectral, mechanical properties of the coated glasses were analyzed. The coated glass samples displayed a better scratch resistance and surface hydrophobicity, compared to uncoated samples, without any significant changes in their inherent spectral properties. The thermal and mechanical properties (Tg and tensile strength) of the nanocomposites were also enhanced compared to neat polymers. The improvement in thermal and scratch resistance of the coatings is ascribed to the inclusion of halloysite nanotubes (HNTs) in the polymer matrix. Hence, HNT-based PMMA/PS nanocomposite coatings can be effectively used for glasses in automotive and architectural applications. © 2017 Elsevier B.V.Item Polystyrene-halloysite nano tube membranes for water purification(Korean Society of Industrial Engineering Chemistry A-803 Twin Bldg 275-3 Yangjae-Dong Seocho-Kul Seoul 137-130, 2018) Buruga, K.; Kalathi, J.T.; Kim, K.-H.; Ok, Y.S.; Boukhvalov, B.Membrane technologies are a sustainable solution for treatment of water and wastewater. Here, the technical feasibility of polystyrene-halloysite nanotube (PS-HNT) membranes, fabricated by an ultrasound-assisted solution casting method, was explored for water purification. To this end, the effects of various solvents on the structure, morphology, thermal, and mechanical properties of PS-HNT membranes were investigated. Introduction of HNTs (5 wt%) into the polystyrene matrix demonstrated excellent thermal and mechanical properties along with good water flux, rejection of unwanted components, recovery, and regeneration cycles. These membranes were overall useful enough to purify real wastewater collected from pulp and paper mill. © 2017 The Korean Society of Industrial and Engineering ChemistryItem Low-temperature sonochemical synthesis of high dielectric Lanthanum doped Cerium oxide nanopowder(Elsevier Ltd, 2018) Kishor Kumar, M.J.; Kalathi, J.T.Lanthanum (La) doped Cerium Oxide (CeO2) nanopowder was synthesized at a relatively lower temperature (70°C), without calcination in a simple, faster, and efficient way through sonochemical method. X-ray diffraction (XRD) results confirmed the formation of a cubic fluorite structure of nanocrystalline CeO2 and lattice deformation due to La-doping in CeO2. TEM analysis revealed that the size of La-doped CeO2 particles is in the range of 20?50 nm. In addition, selective area electron diffraction (SAED) and high-resolution TEM (HRTEM) analyses portrayed the nano-crystallinity, lattice fringe pattern, and d-spacing details of La-doped CeO2 powder. Lanthanum doping in CeO2 was further confirmed by a shift in Raman band towards the lower frequency (from 464 cm?1 to 457cm?1) along with peak intensity increase. Photoluminescence (PL) emission spectra showed that emission intensity of the La-doped CeO2 at 510 nm is increased due to oxygen vacancy mediated charge transfer. All these results confirm the successful doping of La in CeO2. The La-doped CeO2 powder possesses a high dielectric constant (?r) of 106 and a low dielectric loss (tan ?) of < 0.4 % at 1 kHz. The La-doped CeO2 finds potential applications on developing devices in the field of a thin film capacitor, transistors, and solid oxide fuel cells. © 2018 Elsevier B.V.Item Fabrication of ?-MPS-Modified HNT–PMMA Nanocomposites by Ultrasound-Assisted Miniemulsion Polymerization(Minerals, Metals and Materials Society 184 Thorn Hill Road Warrendale PA 15086, 2018) Buruga, K.; Kalathi, J.T.Halloysite nanotubes (HNTs) were modified with ?-methacryloxypropyltrimethoxysilane (?-MPS) to improve their interaction with the polymer, and the modified HNTs (MHNTs) were subsequently used for the synthesis of MHNT–polymethylmethacrylate (PMMA) nanocomposites by miniemulsion polymerization assisted by ultrasound. Reduced agglomeration of HNTs due to modification with ?-MPS was evident from scanning electron microscopy analysis. Modification of HNTs and exfoliation of MHNTs in the polymer nanocomposite were confirmed by the presence of their respective characteristic peaks in Fourier-transform infrared spectra and x-ray diffraction patterns. Transmission electron microscopic analysis showed that the surface of the MHNTs differed significantly from that of unmodified HNTs. MHNT–PMMA nanocomposite exhibited significantly higher glass-transition temperature (Tg) compared with neat PMMA or unmodified HNT–PMMA nanocomposite. Hence, such modification of HNTs along with miniemulsion polymerization assisted by ultrasound is a promising approach to achieve better dispersion of HNTs in the polymer and to obtain nanocomposites with enhanced properties. © 2018, The Minerals, Metals & Materials Society.