Faculty Publications
Permanent URI for this communityhttps://idr.nitk.ac.in/handle/123456789/18736
Publications by NITK Faculty
Browse
20 results
Search Results
Item Nonlinear transmittance and optical power limiting in magnesium ferrite nanoparticles: effects of laser pulsewidth and particle size(Royal Society of Chemistry, 2016) Perumbilavil, S.; Sridharan, K.; Abraham, A.R.; Janardhanan, H.P.; Kalarikkal, N.; Philip, R.We report comparative measurements of size dependent nonlinear transmission and optical power limiting in nanocrystalline magnesium ferrite (MgFe2O4) particles excited by short (nanosecond) and ultrashort (femtosecond) laser pulses. A standard sol-gel technique is employed to synthesize particles in the size range of 10-50 nm, using polyvinyl alcohol as the chelating agent. The structure and morphology of the samples are studied using X-ray diffraction, scanning electron microscopy and transmission electron microscopy. Growth of the particles in time is tracked through Fourier transform infrared spectroscopy. Nonlinear transmission measurements have been carried out using the open aperture Z-scan technique employing 532 nm, 5 nanosecond pulses and 800 nm, 100 femtosecond pulses, respectively. The measured optical nonlinearity is primarily of a reverse saturable absorption (RSA) nature, arising mostly from excited state absorption for nanosecond excitation, and two-photon absorption for femtosecond excitation. The optical limiting efficiency is found to increase with particle size for both cases. The calculated nonlinear parameters indicate that these materials are potential candidates for optical limiting applications. © The Royal Society of Chemistry.Item Magnetically retrievable nickel hydroxide functionalised AFe2O4 (A = Mn, Ni) spinel nanocatalyst for alcohol oxidation(Springer Nature, 2016) Bhat, P.B.; Badekai Ramachandra, B.R.Ultrasmall nickel hydroxide functionalised AFe2O4 (A = Mn, Ni) nanocatalyst was synthesized by traditional co-precipitation method and was examined for oxidation of aromatic alcohols to carbonyls using hydrogen peroxide as terminal oxidant. A very high surface area of 104.55 m2 g?1 was achieved for ferromagnetic MnFe2O4 and 100.50 m2 g?1 for superparamagnetic NiFe2O4, respectively. Efficient oxidation was observed due to the synergized effect of nickel hydroxide (bronsted base) on Lewis center (Fe) of the nanocatalyst. Catalyst recycling experiments revealed that the ultrasmall nanocatalyst can be easily recovered by external magnet and applied for nearly complete oxidation of alcohols for at least five successive cycles. Furthermore, the nickel hydroxide functionalised ultrasmall nanocatalyst exhibited higher efficiency for benzyl alcohol oxidation compared to Ni(OH)2, bare MnFe2O4 and NiFe2O4. Higher conversion rate was observed for nickel hydroxide functionalised NiFe2O4 compared to MnFe2O4. Ultrasmall magnetic nickel hydroxide functionalised nanocatalyst showed environmental friendly, greener route for the oxidation of alcohols without significant loss in activity and selectivity within successive runs. © 2015, The Author(s).Item Microwave assisted growth of stannous ferrite microcubes as electrodes for potentiometric nonenzymatic H2O2 sensor and supercapacitor applications(Elsevier Ltd, 2016) Bindu, K.; Sridharan, K.; Ajith, K.M.; Lim, H.N.; Nagaraja, H.S.Electrochemical sensors and supercapacitors are two noteworthy applications of electrochemistry. Herein, we report the synthesis of SnFe2O4 microcubes and Fe2O3 nanorods through a facile microwave assisted technique which are employed in fabricating the electrodes for nonenzymatic hydrogen peroxide (H2O2) sensor and supercapacitor applications. SnFe2O4 microcubes exhibited an enhanced specific capacitance of 172 Fg?1 at a scan rate of 5 mVs?1 in comparison to Fe2O3 nanorods (70 Fg?1). Furthermore, the H2O2 sensing performance of the fabricated SnFe2O4 electrodes through chronopotentiometry studies in 0.1 M PBS solution (at pH 7) with a wide linear range revealed a good sensitivity of 2.7 mV ?M?1 ?g?1 with a lowest detection limit of 41 nM at a signal-to-noise ratio of 3. These results indicate that SnFe2O4 microcubes are excellent materials for the cost effective design and development of efficient supercapacitors as well as nonenzymatic sensors. © 2016 Elsevier LtdItem Influence of ageing time on hardness, microstructure and wear behaviour of AISI2507 super duplex stainless steel(Institute of Physics Publishing helen.craven@iop.org, 2017) Davanageri, M.; Narendranath, S.; Kadoli, R.The effect of ageing time on hardness, microstructure and wear behaviour of super duplex stainless AISI 2507 is examined. The material was solution treated at 1050 °C and water quenched, further the ageing has been carried out at 850 °C for 30 min, 60 min and 90 min. The chromium (Cr) and molybdenum (Mo) enriched intermetallic sigma phase (?) were found to precipitate at the ferrite/ austenite interface and within the ferrite region. The concentration of intermetallic sigma phase (?), which was quantified by a combination of scanning electron microscopy and image analysis, increases with increasing ageing time, leading to significant increase in the hardness. The x-ray diffraction (XRD) and energy dispersive x-ray (EDX) was employed to investigate the element distribution and phase identification. Wear characterstics of the aged super duplex stainless steel were measured by varying normal loads, sliding speeds, sliding distance and compared with solution treated (as-cast) specimens. Scanning electron microscopy was used to assist in analysis of worn out surfaces. The outcomes suggested that the increase in percentage of sigma phase increases hardness and wear resistance in heat-treated specimens compared to solution treated specimens (as-cast). © 2017 IOP Publishing Ltd.Item Photocatalytic degradation of Irgalite violet dye using nickel ferrite nanoparticles(IWA Publishing 12 Caxton Street London SW1H 0QS, 2019) Vijay, S.; Mohan Balakrishnan, R.M.; Rene, E.R.; Uddandarao, P.Nanotechnologies have prominent applications in the field of science and technology owing to their size-tunable properties providing a promising approach for degradation of various pollutants. In this scenario, the present work aims to study the effect of nickel ferrite nanoparticles on the degradation of Irgalite violet dye by Fenton’s reaction using oxalic acid as an oxidizing agent in the presence of sunlight. The effect of pH and adsorbent dosage on the rate of dye degradation was monitored. Based on these studies it was observed that 99% dye degradation was achieved for catalyst dosage of 0.2 g, 400 ppm dye concentration and 2.0 mM oxalic acid at pH 3.0 within 60 min. The studies reveal that the degradation follows pseudo-first-order kinetics and the catalyst reusability remained constant almost for five cycles. Further, nickel ferrite nanoparticles are proven to be an efficient alternative for the removal of dyes from coloured solutions. © IWA Publishing 2019Item Influence of cations on the dielectric properties of spinel structured nanoferrites(Institute of Physics Publishing helen.craven@iop.org, 2019) Bindu, K.; Ajith, K.M.; Nagaraja, H.S.MFe2O4 (M: Fe, Zn, Ni and Sn) nanoparticles were prepared using single step hydrothermal method. Their structural, compositional and dielectric properties have been studied to investigate the effect of cations on spinel ferrites. XRD confirms the spinel structure of the samples with substitution of Zn, Ni and Sn in the lattice sites of Fe. FTIR spectra of all samples have characteristic ?1 and ?2 bands. SEM and EDS mapping show uniform distribution of cations throughout the samples. ZnFe2O4 and SnFe2O4 have higher ac conductivity and dielectric constant than that of Fe3O4 and NiFe2O4, which can be attributed to the different cationic distribution in the spinel structure. © 2019 IOP Publishing Ltd.Item Structure-Property Correlation of Quenching and Partitioning Heat Treated Silicon-Manganese Steel(Springer Netherlands rbk@louisiana.edu, 2019) Acharya, P.P.; Bhat, R.The present investigation deals with the effect of varying quenching and partitioning parameters on microstructure and mechanical properties of American Iron and Steel Institute 9255 steel. The specimens were fully austenitised at 900 ?C for 45 min and then quenched at 190 ?C and followed by partitioning at various temperatures 280, 320, 360 and 400 ?C and partitioning times 15, 30, 45, 60 and 90 min for each temperature. Post heat treatment includes microstructural analysis that was carried out by using scanning electron microscope (SEM) along with electron back scattered diffraction (EBSD) and x-ray diffraction (XRD) and then correlated to the mechanical properties i.e. tensile properties and hardness of the steel. Results indicate that the specimens quenched at 190 ?C and partitioned over a temperature range 280 to 400 ?C generates multiphase microstructures containing major fraction of martensitic structure (lath and plate-type), transitional ?-carbides in tempered martensite matrix and retained austenite (RA) for all the conditions. At higher partitioning temperatures i.e. 360 and 400 ?C reveals some bainitic ferrite laths along with martensite and RA. Superior tensile strength, % elongation and modulus of toughness values of 1860 MPa, 12% and 207 MJ/m3 respectively was attained at partitioning time of 15 min at 280 ?C. © 2018, Springer Nature B.V.Item Influence of cations in MFe2O4 (M: Fe, Zn, Ni, Sn) ferrite nanoparticles on the electrocatalytic activity for application in hydrogen peroxide sensor(Institute of Physics Publishing helen.craven@iop.org, 2019) Bindu, K.; Nagaraja, H.S.Hydrothermally prepared MFe2O4 (M: Fe, Zn, Ni and Sn) nanoparticles have been characterized by XRD, SEM and BET. The ferrite nanoparticles have been tested for their electrocatalytic activity and application towards the reduction and sensing of hydrogen peroxide using cyclic voltammetry and chronoamperometry techniques. ZnFe2O4 and SnFe2O4 reveal superior H2O2 sensing performance than Fe3O4 and NiFe2O4, which can be attributed to the lower redox potential of Sn2+/Sn4+ couple, lower charge-transfer resistance and higher specific surface area. ZnFe2O4 and SnFe2O4 have a sensitivity of 4.411 and 3.915 ?AmM-1 ?g-1, respectively, which is greater than that of Fe3O4 (0.434 ?AmM-1 ?g-1) and NiFe2O4 (0.644 ?AmM-1 ?g-1). SnFe2O4 has the lowest limit of detection (2.6 (M) with good selectivity towards H2O2 in the presence of other interference agents. © 2019 IOP Publishing Ltd.Item Development of an industrial ferritic rolling process for IF grade steel(Taylor and Francis Ltd., 2020) Kumar, D.S.; Sambandam, M.; Bhat K, U.K.Interstitial free (IF) grade steels have high transformation temperatures and often results in non-uniform rolling and lower yields. In the present work, industrial ferritic rolling process is developed, where finish rolling is carried out below the Ar1 temperature for the IF grade steel. Offline simulation was carried out using a hot strip mill model (HSMM) software and full-scale ferritic rolling was carried out in a seven-stand hot strip mill under two different finishing and coiling temperatures and compared with austenitic rolling. Furnace drop-out temperature, mill speed and inter-stand cooling were controlled to achieve the desired low rolling temperatures. Both ferritic rolled coils had strained elongated grains and well-developed alpha (<110>//RD) and gamma (<111>//ND) textures. The lower finishing and coiling temperature processed coil shows higher microstructural and textural variation along with the thickness. This work established the optimum parameters for the industrial ferritic rolling process for IF grade steel. © 2020, © 2020 Institute of Materials, Minerals and Mining.Item Reactive magnetron sputtered–assisted deposition of nanocomposite thin films with tuneable magnetic, electrical and interfacial properties(Springer Science and Business Media B.V. editorial@springerplus.com, 2020) Ratnesh, R.K.; Singh, M.; Pathak, S.; Dakulagi, V.In this work, different magnetic thin films of Ni, NiFe and NiFe2O4 are deposited on the SiO2 substrate using sputtering technique. Our experiments confirmed that thin films possess a good nanocrystalline structure. The key deposition parameters controlling their magnetic properties are sheet resistivity, crystalline structure and microtopography of the sputtered thin film. Besides, the reactive gas oxygen (O2) also plays a leading role in transforming the phase and structure of the ferrite film. The nanocrystalline nature of the ferrite film results in the reduction of overall coercivity (HC). The thickness of the sputtered thin film is in the range of 800–1000 Å. The prepared film exhibits roughness in the range of (~ 0.60 to ~ 0.98 nm). Furthermore, the structural transformation study is performed with X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR). The quite low roughness, high resistivity and low Hc make NiFe2O4 thin film as a potential candidate for the future spintronics, optoelectronics, photocatalysis and solar cell applications. © 2020, Springer Nature B.V.