Conference Papers
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Item Electronic band structure and photoemission spectra of graphene on silicon substrate(SPIE spie@spie.org, 2014) Javvaji, B.; Ravikumar, A.; Shenoy, B.M.; Roy Mahapatra, D.; Rahman, M.R.; Hegde, G.M.Synergizing graphene on silicon based nanostructures is pivotal in advancing nano-electronic device technology. A combination of molecular dynamics and density functional theory has been used to predict the electronic energy band structure and photo-emission spectrum for graphene-Si system with silicon as a substrate for graphene. The equilibrium geometry of the system after energy minimization is obtained from molecular dynamics simulations. For the stable geometry obtained, density functional theory calculations are employed to determine the energy band structure and dielectric constant of the system. Further the work function of the system which is a direct consequence of photoemission spectrum is calculated from the energy band structure using random phase approximations. © 2014 SPIE.Item Optoelectronic properties of graphene silicon nano-texture(Institute of Electrical and Electronics Engineers Inc., 2014) Brahmanandam, J.; Ajmalghan, M.; Abhilash, R.K.; Roy Mahapatra, D.; Rahman, M.R.; Hegde, G.M.Graphene on silicon with silicon dioxide quantum dots is a promising opto-electronic material. The optical band gap and the corresponding optical conductivity are estimated using the density functional approach with the combination of molecular dynamics. The regular repeating unit cell of graphene silicon nano-texture is identified using the classical molecular dynamics simulations. Electronic calculations predict the optical band gap is around 0.2 eV and the optical conductivity is identified to be 0.3 times the quantum conductance. © 2014 IEEE.Item Optoelectronic properties of graphene on silicon substrate: Effect of defects in graphene(SPIE spie@spie.org, 2015) Javvaji, B.; Ajmalghan, M.; Roy Mahapatra, D.; Rahman, M.R.; Hegde, G.M.Engineering of electronic energy band structure in graphene based nanostructures has several potential applications. Substrate induced bandgap opening in graphene results several optoelectronic properties due to the inter-band transitions. Various defects like structures, including Stone-Walls and higher-order defects are observed when a graphene sheet is exfoliated from graphite and in many other growth conditions. Existence of defect in graphene based nanostructures may cause changes in optoelectronic properties. Defect engineered graphene on silicon system are considered in this paper to study the tunability of optoelectronic properties. Graphene on silicon atomic system is equilibrated using molecular dynamics simulation scheme. Based on this study, we confirm the existence of a stable super-lattice. Density functional calculations are employed to determine the energy band structure for the super-lattice. Increase in the optical energy bandgap is observed with increasing of order of the complexity in the defect structure. Optical conductivity is computed as a function of incident electromagnetic energy which is also increasing with increase in the defect order. Tunability in optoelectronic properties will be useful in understanding graphene based design of photodetectors, photodiodes and tunnelling transistors. © 2015 SPIE.Item Complex impedance spectroscopy properties of Fe3BO6 nanocrystallites prepared by combustion method(Elsevier Ltd, 2019) Kumari, K.; Ramteke, R.; Rahman, M.R.In this investigation, we report a part of our work on Impedance spectroscopy of Fe3BO6 nanoceramics prepared by a selfcombustion of a solid precursor mixture of 60Fe2O3-40B2O3 using camphor as a fuel in ambient air. A single phase compound Fe3BO6 of an orthorhombic crystal structure with Pnma space group and average crystallites size D = 42 nm is analyzed from the X-ray diffractogram. The Z?-value decreases with a shift in the peak frequency towards the higher side with rise in temperature arises possibly due to the presence of dipolar response in the material, which is in good agreement with the observation of complex impedance data. Temperature dependent impedance describes Fe3BO6 to be an ionic conductor; with activation energy (Ea) value0.73 eV. The Ea-values so obtained for the dielectric relaxation from the tp-values suggests a conduction mechanism involving the polaron hopping. © 2019 Elsevier Ltd. All rights reserved.Item Mineralogical studies of low grade iron ore from Bellary-Hospet region, India(American Institute of Physics Inc. subs@aip.org, 2019) Mohanraj, G.T.; Krishneindu, P.; Choudhary, R.P.; Meena, S.S.; Yusuf, S.M.; Rahman, M.R.Detailed mineralogical characterization study has been conducted on low grade iron ore sample from Bellary-Hospet region, Karnataka, India by using XRD, optical microscopy and Mössbauer spectroscopy techniques for identifying the eminence of iron ore sample. Liberation analysis was carried out by particle size analysis and specific gravity measurement. Chemical analysis results showed that, -125+90μ size fraction assaying up to 57.34% Fe, 8.55% SiO 2 and 8.6% Al 2 O 3 . XRD analysis revealed the presence of major hematite phase along with kaolinite, gibbsite, quartz and goethite in the sample. Microscopic study confirms the transformation of magnetite to hematite by martitization. Mössbauer spectrum reveals the existence of hematite α-Fe 2 O 3 phase with small distortion in crystal structure. © 2019 Author(s).Item Investigating Sedimentation and Rheological properties of Magnetorheological Fluids using various carrier fluids(IOP Publishing Ltd, 2019) Aruna, M.N.; Rahman, M.R.; Joladarashi, S.; Kumara, H.The present paper focuses on the preparation of Magnetorheological (MR) fluids samples with three types of carrier fluids are silicone, light paraffin and Poly-alpha-olefin (5, 30 and 400 cSt) viscosity oils with 25% volume fraction of carbonyl iron particles and 3% fumed silica as a thixotropic agent to improve sedimentation of the MR fluid. The morphology, magnetic saturation and phase of the carbonyl iron particles were investigated using field emission scanning electron microscopy (FESEM), super quantum interface interference device (SQUID), X-ray diffraction (XRD) respectively. The results found that obtained powder particles spherical in shape, and a high magnetic saturation of 270 (emu/gm) with the applied field of 15000 (Oe). The prepared MR fluids rheological properties were tested using Anton Paar MCR702 Twin drive rheometer fitted with a magneto-rheological module. Sedimentation stability examined using direct observation method. © Published under licence by IOP Publishing Ltd.Item Investigation of steady state rheological properties and sedimentation of coated and pure carbonyl iron particles based magneto-rheological fluids(Elsevier Ltd, 2020) Swaroop, K.V.; Aruna, M.N.; Kumar, H.; Rahman, M.R.MR fluids face a major problem of sedimentation rate due to the high- density difference between the magnetic particles and the carrier medium that affects the performance of the magnetorheological devices. In this work, two MRF samples are prepared, where MRF-1 and MRF-2 are pure and coated carbonyl iron particles (CIPs) based MR fluids. The surface modification of the CIPs is performed using the solvent dispersion method to improve the sedimentation rate. The spherical shape and particle size analysis of the pure CIPs and coated CIPs' morphology is investigated using the Scanning Electron Microscope (SEM). The Thermal Gravimetric Analysis (TGA) shows that the coated CIPs have high thermal stability and confirm that 6% by wt. coating is present in the coated sample. The chemical bonding of the coated CIPs is detected using the Fourier Transform Infrared Spectroscopy (FT-IR). The saturation magnetization (Ms) of pure and coated CIPs is 245 emu/g and 120 emu/g, respectively, at 15 kOe, which is obtained by using a superconducting quantum interface device (SQUID). The rheology flow curve properties show that MRF-1 and MRF-2 exhibit yield stress of about 10 kpa and 9 kpa, respectively, for varying magnetic fields ranging from 0 to 343 kA/m. The Herschel-Bulkley model is fitted with the experimental data and the shear thinning behaviour is observed for both MR fluids. The sedimentation study shows that MRF-2 has better settling rate than MRF-1, which is observed by using the visual observation method up to 600 h. © 2020 Elsevier Ltd. All rights reserved.Item Development and characterization of Cu/MWCNT composite prepared by electrodeposition technique(American Institute of Physics Inc. subs@aip.org, 2020) Bharathi, K.D.; Rahman, M.R.; Choudhary, S.; Arya, S.B.Multi walled carbon nanotube (MWCNT) reinforced copper matrix (Cu/MWCNTs) nanocomposites were successfully fabricated by electrodeposition technique using DC-Power source. With various concentrations of CNT, microstructural, micro hardness, tensile stress, and Electrochemical studies were done. The Cu/MWCNT nanocomposites at the highest concentration of 450mg/l exhibited ∼25% and 47% higher tensile strength and Vickers microhardness respectively than that of the pure Cu. Electrochemical AC-impedance and Tafel polarisation analyses confirmed that the corrosion potential (Ecorr) and corrosion current density (icorr) of nanocomposites at 450 «mg/l obtained about 190 »mV SCE and 1.09 μ A/cm2 respectively in 3.5 wt.% NaCl solution. © 2020 Author(s).Item Rheological characterization of tragacanth gum coated carbonyl particles based magnetorheological fluid(American Institute of Physics Inc. subs@aip.org, 2020) Swaroop, K.V.; Aruna, M.N.; Kumar, H.; Rahman, M.R.The surface modification of soft carbonyl particle (CIPs) based magnetorheological (MR) fluids is the most popular method to solve sedimentation problem. In this present work,the two MR fluidswere prepared using pure CIPs (MRF#1) and Tragacanth gum coated CIPs (Tg/ CIPs) (MRF#2) are dispersed in hydraulic oil as a carrier fluid. The morphology, elemental composition and magnetic saturation properties were investigated using scanning electron microscopy (SEM),energy dispersive spectroscopy (EDS), superconducting quantum interface device (SQUID) analysis respectively. In addition to that,chemical bonding and thermal oxidation resistance of CIPs and (Tg/ CIPs) was analyzed using Fourier-transform infrared spectroscopy FTIR and thermo-gravimetric analyzer (TGA). The rheological properties of CIPs and Tg/CIPs based MRFs was tested to determine the flow behaviourat different currents 0,1,2,3 and 4Amps. The experimental results found that Tg/CIPs based MRFs is having higher yield stress of about (16kPa) than pure CIPs (15kPa). The decrease in the density of Tg/CIPs showed better sedimentation ratio (i.e r=91%) than the pure CIPs based MRFs which was observed using naked eye visual method. © 2020 Author(s).Item Fabrication of β-Phase PVDF/MWCNTs Nanofibers on a Flexible Substrate for Energy Harvesting Application(Institute of Electrical and Electronics Engineers Inc., 2024) Chauhan, S.S.; Sharma, S.; Muhiuddin, M.; Rahman, M.R.It is challenging to deposit the pristine polyvinylidene difluoride (PVDF) in β crystalline phase on a flexible substrate since pristine PVDF exists in the α-phase. This paper presents a novel formation of nanofibers membrane of PVDF in which multiwall carbon nanotubes (MWCNT) is added as the composite in PVDF for transformation from α to β phase. The PVDF/MWCNTs nanofibers is electro spun after adding carboxyl functionalized MWCNT with PVDF to form the β phase. The field emission scanning electron microscope (FE-SEM) is used to characterize the presence of the nanofiber's membrane. X-ray diffraction (XRD) is used to characterize the β phase and Fourier-transform infrared spectroscopy (FTIR) is used to detect the functionalized bonds in the formation of PVDF/MWCNTs nanofibers on a flexible Polyethylene Terephthalate (PET). The measurement of the polarization of electric field hysteresis shows good characteristics with Ps, Pr, and EC are 9.58 μC/m2, 4 μC/m2, and 1 MV/m, respectively. The optimized film has a high potential for application as the piezoelectric material in energy harvesting devices fabricated on a flexible PET film. © 2024 IEEE.