Faculty Publications
Permanent URI for this communityhttps://idr.nitk.ac.in/handle/123456789/18736
Publications by NITK Faculty
Browse
6 results
Search Results
Item Structural and magnetic studies of tin doped α-Fe2O3 (α-SnxFe2-xO3) nanoparticles prepared by microwave assisted synthesis(American Institute of Physics Inc. subs@aip.org, 2016) Bindu, K.; Chowdhury, P.; Ajith, A.; Nagaraja, H.S.Hematite (α-Fe2O3) doped with tetravalent ions have potential applications in various fields such as gas sensors, memories, energy storage devices because of their electrical and magnetic properties. Microwave assisted synthesis was used to prepare Tin doped α-Fe2O3 [α-SnxFe2-xO3]. The structural and morphological studies were investigated using X-ray diffraction (XRD) and Scanning electron microscopy (SEM). XRD patterns revealed that α-Fe2O3 and α-SnxFe2-xO3 were having rhombohedral structure. The compositional study was done by Energy dispersive X-ray Spectroscopy (EDS). The magnetic properties were studied by Vibrating Sample Magnetometry (VSM). Results shows that the prepared samples were found to be antiferromagnetic in nature and the results are discussed in detail. © 2016 Author(s).Item Optical and electrical properties of ITO thin films sputtered on flexible FEP substrate as passive thermal control system for space applications(Elsevier, 2016) Sibin, K.P.; Swain, N.; Chowdhury, P.; Dey, A.; Sridhara, N.; Shashikala, H.D.; Sharma, A.K.; Barshilia, H.C.ITO thin films were deposited on flexible fluorinated ethylene propylene (FEP) substrates by pulsed direct current reactive magnetron sputtering system using an In:Sn (90%-10% wt.) alloy target. The influence of the deposition parameters (argon and oxygen flow rates, and substrate temperature) and effect of coating thickness on the optical, electrical, structural and microstructural properties of ITO thin films deposited on FEP was investigated. The thickness of the ITO coatings was varied from 5 to 180 nm. The optimized ITO coating (10 nm thick) exhibited high IR emittance (79%) on FEP substrate with high average solar transmittance (94.0%) and moderate sheet resistance (3 k?/sq.). We also investigated in detail the angular dependence of reflectance as well as haze factor of thin ITO coatings. Our results suggest that 10 nm thick ITO coating exhibits an average haze factor of 8.6%. The high value of IR emittance, moderate sheet resistance and high solar transmittance along with low haze factor indicate the suitability of ITO thin films on FEP substrates as flexible optical solar reflector for space applications. © 2015 Elsevier B.V. All rights reserved.Item Effect of electrolyte temperature on the formation of highly ordered nanoporous alumina template(Elsevier B.V., 2016) Boominathasellarajan, B.; Sharma, M.; Ghosh, S.K.; Nagaraja, H.S.; Barshilia, H.C.; Chowdhury, P.In this work, we present a systematic influence of electrolyte temperature along with anodizing potential on the pore parameters during two-step anodization of Al in H2SO4 electrolyte. Top surface morphology of the nanoporous templates was examined with the help of field emission scanning electron microscope and atomic force microscope. Three-dimensional (3D) Fast Fourier Transform (FFT) image analysis was then employed to quantify pore regularity and pore periodicity as a function of both the bath temperature (1-15 °C) and the anodic potential (15-25 V). A highest pore regularity ratio of 5 × 108 was obtained at 3°C and 25 V with a pore diameter of 32 ± 3 nm and inter-pore distance of 65 nm. With further increase in temperature, the pore regularity ratio was found to decrease drastically. It was found that higher temperature favored the dissolution of compact aluminum oxide layer isotropically along the pore length. This process in effect enhanced the pore size, growth rate, and template top surface roughness without affecting much inter-pore distance. Self-ordering of the pores was found to improve with increasing anodizing potential with a critical influence of the current density along with inter-pore distance. The mechanism of pore growth was discussed in terms of temperature-dependent activation energy controlled dissolution of aluminum. The typical activation energy evaluated at 25 V was 72.8 kJ/mol at 3°C. © 2015 Elsevier Inc. All rights reserved.Item Effect of shape and magnetocrystalline anisotropies in ordered Co nanorod arrays with smaller diameter(Elsevier, 2016) Boominathasellarajan, B.; Nagaraja, H.S.; Barshilia, H.C.; Chowdhury, P.Template assisted growth of Co nanorod arrays through electrochemical route was investigated. During this investigation, the template with nano-pore diameter was kept at a fixed value of 45 nm, whereas the length of the as grown nanorod array was varied from 25 to 400 nm keeping in mind that the aspect ratio (L/D) covers both below and above the unity. X-ray diffraction patterns indicate that the nanorod arrays initiate its textured growth with fcc (111) phase, however, the change in growth texture to hcp (100) was observed as it grows above 200 nm in length. The anisotropy fields extracted from the measured magnetization data reveal that a cross-over from in-plane to out-of-plane anisotropy takes place for L/D ?2.0. Based on the analytical approach, it seems that the shape anisotropy originated from the demagnetization factor with the change in geometry and magnetostatic interaction among the nanorods cause this crossover. However the micromagnetic simulation yields that both magnetocrystalline anisotropy and the magnetostatic interaction along with shape anisotropy are very much important to explain the experimental observations. © 2015 Elsevier B.V. All rights reserved.Item Shape induced magnetic vortex state in hexagonal ordered cofe nanodot arrays using ultrathin alumina shadow mask(Elsevier B.V., 2018) Boominathasellarajan, B.; Saravanan, P.; Ghosh, S.K.; Nagaraja, H.S.; Barshilia, H.C.; Chowdhury, P.The magnetization reversal process of hexagonal ordered CoFe nanodot arrays was investigated as a function of nanodot thickness (td) varying from 10 to 30 nm with fixed diameter. For this purpose, ordered CoFe nanodots with a diameter of 80 ± 4 nm were grown by sputtering using ultra-thin alumina mask. The vortex annihilation and the dynamic spin configuration in the ordered CoFe nanodots were analyzed by means of magnetic hysteresis loops in complement with the micromagnetic simulation studies. A highly pinched hysteresis loop observed at 20 nm thickness suggests the occurrence of vortex state in these nanodots. With increase in dot thickness from 10 to 30 nm, the estimated coercivity values tend to increase from 80 to 175 Oe, indicating irreversible change in the nucleation/annihilation field of vortex state. The measured magnetic properties were then corroborated with the change in the shape of the nanodots from disk to hemisphere through micromagnetic simulation. © 2017 Elsevier B.V.Item Synthesis and electrochemical properties of silver dendrites and silver dendrites/rGO composite for applications in paracetamol sensing(Elsevier Ltd, 2018) Dhanush, S.; Moolayadukkam, M.; Bindu, K.; Chowdhury, P.; Nagaraja, H.S.Electrochemical sensors are one of the important applications of electrochemistry. In this paper, synthesis, characterization and application of Silver Dendrites and Silver Dendrites/rGO sensors for simple and fast determination of Paracetamol are described. Silver dendrites and their composite with graphene oxide were synthesized by galvanic replacement method. The synthesized samples were characterized by XRD, SEM and TEM. XRD reveals the FCC structure of silver and TEM images show the formation of dendritic silver wrapped in the graphene sheets. The Electrochemical paracetamol sensing properties of these samples were tested using cyclic voltammetry and chronoamperometry. The silver dendrites exhibit a sensitivity of 2.807 × 105?A/mM/g and a lower detection limit of 2.5 ?M, whereas, the composite with graphene oxide exhibits a high sensitivity of 2.511 × 106?A /mM/g with a lower detection limit of 0.025 ?M. © 2018 Elsevier Ltd