Faculty Publications
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Item Influence of additives on the synthesis of carbonyl iron suspension on rheological and sedimentation properties of magnetorheological (MR) fluids(Institute of Physics Publishing helen.craven@iop.org, 2019) Aruna, M.N.; Rahman, M.R.; Joladarashi, S.; Kumar, H.Magnetorheological (MR) fluid is one of the major constituent element in structural suspensions and damping characteristic in automobile applications. The major drawback is sedimentation in MR fluids, in the present study an attempt has been done to address the sedimentation issue. The synthesis and characterization of MR fluid in combination with clay and additives leads to improvement in sedimentation rate. The four different types of MR fluid were prepared in combination with clay, friction reducing agent and poly-alpha-olefin (PAO) oil naming as MRFp-1, 2, 3 and 4 as tabulated in table 1. The cost effective MRFp-3 shows better result compared to commercially available MR fluid with respect to off/on state shear stress, viscosity. It is also observed that in-house prepared MRFp-3 has better sedimentation than commercially available (LORD-132DG) up to 700 h. © 2019 IOP Publishing Ltd.Item Highly Sensitive and Stable NO2 Gas Sensors Based on SWNTs with Exceptional Recovery Time(Institute of Electrical and Electronics Engineers Inc., 2019) Chauhan, S.S.; Kumar, D.; Chaturvedi, P.; Rahman, M.R.Room temperature operable and highly sensitive NO2 gas sensors are fabricated based on (i) random and (ii) aligned networks of single-walled carbon nanotubes (SWNTs). The fabricated sensors are very sensitive, stable, and show shorter recovery time in the presence of UV light. Also, the variation of the response and recovery with network density is analyzed. The thin film resistor (TFR) of random network is fabricated by a reliable, cost-effective, and reproducible vacuum filtration method. The aligned network is fabricated using AC di-electrophoresis (DEP) technique. Electrodes spacing is optimized to avoid the chaining effect of aligned and bridged SWNTs between the gold electrode pair to enhance the stability and sensitivity of the sensor. Both the sensors based on random and aligned networks of SWNTs is tested with NO2 at room temperature. It is found that the sensor made of the aligned network shows 3.5 times more sensitivity as compared to the random networks gas sensor but recovery time increases. It is also observed that sensors fabricated by TFR and aligned network techniques are stable and having less than 0.02 % and 0.15 % change in resistance with baseline, respectively. The TFR gas sensors fabricated using as prepared (AP) and purified and low functionality (P2) SWNTs show higher stability but less sensitive compared to the aligned network. The measured complete recovery time of sensors based on random and aligned SWNTs are 50 sec and 124 sec, respectively, for 0.5 ppm NO2. It is also observed that as the network density decreases response improves but the recovery time increases. © 2001-2012 IEEE.Item Design and fabrication of optimized magnetic roller for permanent roll magnetic separator (PRMS): Finite element method magnetics (FEMM) approach(Elsevier B.V., 2021) Mohanraj, G.T.; Rahman, M.R.; Joladarashi, S.; Hanumanthappa, H.; Shanmugam, B.K.; Vardhan, H.; Rabbani, S.A.In the present work, an attempt has been made to develop a PRMS in a cost effective and environmental friendly way through FEMM analysis of magnetic roller (active part of PRMS). The FEMM analysis indicates that, the optimized magnetic roller having magnet-to-steel disk thickness ratio of 5 mm: 2.5 mm was proved to be gainful in beneficiating paramagnetic minerals due to the best magnetic field value from the roller surface that is, 0.89 to 2.59 T. Prediction analysis was performed on FEMM data using artificial neural network (ANN) modelling technique. Further, the design calculations of lab scale PRMS in terms of power requirements and belt tensions were addressed. The fabricated PRMS was tested on paramagnetic mineral (hematite ore) assayed 51.24% of Fe, 10.20% of SiO2, and 2.98% of Al2O3 for different roller speeds and the belt thickness. The result showed that, at 0.5 mm belt thickness with 180 rpm roller speed the fabricated lab scale PRMS works well in terms of improvement in the Fe content up to 59.5% at the concentrate along with the Fe recovery of 71.41%. The obtained results suggest that, the FEMM analysis is more suitable to optimize the effective magnetic roller for the PRMS. © 2021 The Society of Powder Technology JapanItem Flexible and cost effective CNT coated cotton fabric for CO gas sensing application(Elsevier B.V., 2023) D.s, A.K.; Chauhan, S.S.; Krishnamoorthy, K.; P, D.B.; Bharathi, K.D.; Ravikumar, A.; Rahman, M.R.In this paper, a low-cost and room temperature flexible carbon monoxide (CO) gas sensor is presented using multi-walled carbon nanotubes coated cotton fabric. A dip and drying method is used to fabricate a lightweight, and high-performance fabric based CO gas sensor using different concentrations of multi-walled carbon nanotubes (MWCNTs). Transmission electron microscopy (TEM) is utilized for examining the deagglomeration of MWCNTs in the presence of a sufficient amount of surfactant. The field-emission scanning electron microscopy (FESEM) is used to evaluate the formation of a uniform network of MWCNTs on the cotton fabric. Fourier transform infrared (FTIR) spectroscopy is used to confirm the presence of functional groups which plays an important role in CO gas sensing. The fabricated cotton fabric coated with MWCNTs (CCM) sensors are tested with different concentrations of CO gas ranging from 25 ppm to 100 ppm at room temperature. It is found that in comparison to all other sensors, the CCM sensor coated with the higher concentration of MWCNTs (0.5 mg/ml) shows a maximum response of 9.11 % at 25 ppm and 15.2 % at 100 ppm concentration of CO gas respectively. The CCM 4 sensor shows the fastest response and recovery within 49s for 25–100 ppm of CO gas. Moreover, the fabricated CCM sensor exhibited good repeatability, reproducibility, and selectivity. These sensors are suitable for low-cost smart textile applications. © 2023 Elsevier B.V.Item Cost effective synthesis of sulfur and nitrogen co-doped graphene aerogel and application in binder free supercapacitor(American Institute of Physics, 2024) Muhiuddin, M.; Khan, A.Z.; Devi, N.A.; Bharadishettar, N.; Meti, S.; Siddique, A.B.; Bhat K, U.; Akhtar, W.; Rahman, M.R.Incorporating heteroatoms into graphene lattice results in enhanced electrical conductivity and electrochemically active sites and has significant importance in developing high-performance supercapacitors. In this study, sulfur and nitrogen co-doped graphene aerogel is synthesized via hydrothermal technique followed by a simple but effective freeze-thawing and ambient pressure drying process (referred to as SN-GA). The process requires low-cost raw materials and cost-effective equipment without the utilization of any special instrument that operates at ultra-low temperatures, under high pressure, or vacuum environment. Ammonium sulfate [(NH4)2SO4] and ethylenediamine are used as a source of sulfur and nitrogen and as a reducing agent. (NH4)2SO4 with different molarities (0, 12, 24, and 36 mM) are used to synthesize four different aerogel samples marked as GA, SN-GA1, SN-GA2, and SN-GA3. The electrode is prepared using an SN-GA2 sample, exhibiting an outstanding specific capacitance of 244 F g−1 at an applied current density of 1 A g−1 with almost 98.5% Coulomb efficiency. Furthermore, based on the SN-GA2 sample, the symmetrical supercapacitor is fabricated, displaying an energy density of 18.14 Wh kg−1 at a power density of 498.4 W kg−1. Hence, SN-GA2 renders a promising material for supercapacitor applications. © 2024 Author(s).