Faculty Publications
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Item An empirical model for the estimation of moisture ratio during microwave drying of plaster of Paris(2008) Ganesapillai, M.G.; Iyyaswami, I.; Murugesan, T.The drying characteristics of plaster of Paris (POP) under microwave irradiation were studied for different shapes of materials through various drying parameters like microwave power, initial moisture content, and drying time. An empirical model for the estimation of moisture ratio was developed using the drying kinetic data of POP. Further, the experimental data on moisture ratio of POP for different operating conditions were fitted with the nine basic drying model equations. Based on the observations, the constants and coefficients of the literature models were rewritten in the form of Arrhenius and logarithmic expressions considering microwave power as input variable. Fifty-eight new model expressions were derived by changing the constants and coefficients and tested using the present experimental data. From the analysis of RMSE, ?2, and EF parameters for the derived models, a suitable empirical model (Model No. 55, RMSE = 0.0874; ?2 = 0.0020; EF = 0.9999) was established to represent the present experimental data on microwave drying of POP.Item Synthesis and desalination performance of Ar+-N+ irradiated polysulfone based new NF membrane(2011) Hegde, C.; Isloor, A.M.; Padaki, M.; Wanichapichart, P.; Liangdeng, Y.In the last few years, membrane technology has gained more attention from polymer chemists throughout the globe. Nowadays, surface modification of membrane is very useful in biotechnology and food science. In the present investigation, we have synthesized polysulfone based composite nanofiltration (NF) membranes, and characterized these membranes by FT-IR, SEM and membrane performance studies. Surface plasma treatment was carried out by irradiation with argon and nitrogen beams in suitable conditions. It was observed that nitrogen beam caused surface roughness that was more severe than the Ar beam. After irradiation, water contact angle was slightly increased. For pure water permeability, flux increased linearly with the operating pressure. However, for the salt solution, the flux was decreased marginally and salt rejection increased after irradiation due to surface modification. The modification effect was characterized in terms of contact angle, AFM employed roughness measurement and dielectric property. It revealed that irradiated NF membranes showed higher salt rejection and lower flux as compared to the nonmodified membranes. Accordingly, the roughness of the membrane surface intensively affected the performance of RO membrane. © 2010 Elsevier B.V.Item LiClO4-doped plasticized chitosan and poly(ethylene glycol) blend as biodegradable polymer electrolyte for supercapacitors(Institute for Ionics, 2013) Sudhakar, Y.N.; Muthu, M.; Bhat, D.K.Biodegradable polymer electrolyte comprising the blend of chitosan (CS) and poly(ethylene glycol) (PEG) plasticized with ethylene carbonate and propylene carbonate, as host polymer, and lithium perchlorate (LiClO4), as a dopant, was prepared by solution casting technique. The ionic conductivity has been calculated using the bulk impedance obtained through impedance spectroscopy. The variation of conductivity and dielectric properties has been investigated as a function of polymer blend ratio, plasticizer content and LiClO4 concentration at temperature range of 298-343 K. The DSC thermograms show two broad peaks for CS/PEG blend and increased with increase in the LiClO4 content. The maximum conductivity has been found to be 1. 1 × 10-4 S cm-1 at room temperature for 70:30 (CS/PEG) concentration. The electric modulus of the electrolyte film exhibits a long tail feature indicative of good capacitance. The activation energy of all samples was calculated using the Arrhenius plot, and it has been found to be 0. 12 to 0. 38 eV. A carbon-carbon supercapacitor has been fabricated using this electrolyte, and its electrochemical characteristics and performance have been studied. The supercapacitor showed a fairly good specific capacitance of 47 F g-1. © 2012 Springer-Verlag.Item Miscibility, water uptake, ion exchange capacity, conductivity and dielectric studies of poly(methyl methacrylate) and cellulose acetate blends(2013) Jois, H.S.S.; Bhat, D.K.In the last few decades, polymer blends with good miscibility and conductivity have been the focus of study for material scientists. Here, polymer blends of Poly(methyl methacrylate) (PMMA) and Cellulose acetate (CA) of varying blend compositions have been prepared by solution casting method and their miscibility, water uptake, ion exchange capacity (IEC) proton conductivity, and dielectric properties have been studied. Dimethyl formamide (DMF) was used as solvent. Fourier transform infrared spectra (FTIR) and Differential scanning calorimetry (DSC) measurements have been used to analyze the miscibility of the blends. Up to 50/50 PMMA/CA, water uptake showed an increasing trend and for other compositions the value decreased. Ion exchange capacity and conductivity of the blends decreased with increase in PMMA content of the blends. The variations in the blend properties have been attributed to the presence of specific interactions and exchangeable groups in the blend system. The proton conductivity of the blends is in the order of 10-3 S cm-1. Impedance analysis of the blends indicated the absence of any relaxation phenomenon in the blend system. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 3074-3081, 2013 Copyright © 2013 Wiley Periodicals, Inc.Item Lithium salts doped biodegradable gel polymer electrolytes for supercapacitor application(Universite Mohammed Premier Oujda jmaterenvironsci@gmail.com, 2015) Sudhakar, Y.N.; Muthu, M.; Bhat, D.A biodegradable gel polymer (GPE) consisting of Xanthan gum (XG), glycerol, lithium salts like lithium perchlorate and lithium tetraborate were prepared. Using Fourier transform infrared spectroscopy (FTIR), thermal and scanning electron microscopy characterizations the interactions between the components in the gel matrix were studied. Furthermore, a unique electrochemical property was exhibited by GPEs as measured by AC impedance and dielectric studies. The role of anion in the enhancement of conductivity was important in the present study and highest conductivity of 6.4×10-2 S cm-1 at 333K was achieved among lithium salts. Supercapacitor was fabricated using GPE and tested for its electrochemical properties. Supercapacitor showed specific capacitance of was 82 Fg-1 at a scan rate of 5 mV s-1 for Li2B4O7 and 74 Fg-1 at a scan rate of 5 mV s-1. specific energy and specific power. Galvanostatic charge-discharge studies showed excellent cyclic stability.Item Magnetic and dielectric properties of Fe3BO6 nanoplates prepared through self-combustion method(World Scientific Publishing Co. Pte Ltd wspc@wspc.com.sg, 2017) Kumari, K.In the present investigation, a facile synthesis method is explored involving a self-combustion of a solid precursor mixture of iron oxide Fe2O3 and boric acid (H3BO3) using camphor (C10H16O) as fuel in ambient air in order to form a single phase Fe3BO6 crystallites. X-ray diffraction (XRD), Field emission electron microscopy (FESEM), magnetic, and dielectric properties of as prepared sample are studied. From XRD pattern, a single phase compound is observed with an orthorhombic crystal structure (Pnma space group), with average crystallite size of 42 nm. A reasonably uniform size distribution of the plates and self-assemblies is retained in the sample. A magnetic transition is observed in dielectric permittivity (at ~445 K) and power loss (at ~435 K) when plotted against temperature. Aweak peak occurs near 330K due to the charge reordering in the sample. For temperatures above the transition temperature, a sharp increase of the dielectric loss is observed which occurs due to the presence of thermally activated charge carriers. A canted antiferromagnetic Fe3+ ordering in a Fe3BO6 lattice with a localized charge surface layer is an apparent source of exhibiting a ferroelectric feature in this unique example of a centrosymmetric compound. An induced spin current over the Fe sites thus could give rise to a polarization hysteresis loop. Due to the presence of both ferromagnetic as well as polarization ordering, Fe3BO6 behaves like a single phase multiferroic ceramics. © The Author(s).Item Electrical, dielectric and magnetic properties of Sn-doped hematite (?-SnxFe2-xO3) nanoplates synthesized by microwave-assisted method(Elsevier Ltd, 2018) Bindu, K.; Ajith, K.M.; Nagaraja, H.S.Hematite nanoparticles are of interest due to their exceptional electrical and magnetic behavior and various technological applications. The doping of hematite can vary its electrical and magnetic properties. Here, we report the effect of different concentrations of Tin doping on electrical, dielectric and magnetic properties of hematite synthesized by the microwave-assisted method. Tin-doped ?- Fe2O3 (?-SnxFe2-xO3) samples have been characterized using XRD, TGA, FESEM, and EDS (mapping). XRD pattern shows the rhombohedral structure of ?-SnxFe2-xO3. The synthesized samples have nanoplate like structure with a uniform distribution of tin throughout the sample. Electrical properties were investigated using dielectric and impedance studies. The dc resistivity and ac conductivity decreased with increase in concentration up to x = 0.06 (Sn0.06Fe1.94O3). However, it increased with further increase in the concentration of tin. The hopping of electrons between Fe3+ and Fe2+ in octahedral sites accounts for the observed conduction behavior. A single semi-circle of the cole-cole plot for ?-SnxFe2-xO3 indicates the dominant grain boundary effect in conduction. Dielectric constant and loss factor reveal the dielectric relaxation in ?-SnxFe2-xO3 samples. The magnetic properties were studied using VSM, which shows that ?-SnxFe2-xO3 are antiferromagnetic/weakly ferromagnetic in nature with high coercivity. © 2017 Elsevier B.V.Item 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 Temperature-dependant phase transformation of NixFey?xOz nanoferrites: their dielectric and magnetic properties(Springer Verlag service@springer.de, 2019) Bindu, K.; Nagaraja, H.S.0–5 wt% nickel-doped iron oxide nanoparticles were synthesised using microwave-assisted method. Microwave-treated samples were annealed at 450 °C and 600 °C and named as NixFey?xOz-450 and NixFe2?xO3-600 (x = 0. 0.1, 0.2, 0.3, 0.4 and 0.5), respectively. XRD, TGA, SEM and EDS were performed to study structural, thermal, morphological and compositional properties of the samples. Undoped sample has hematite phase at both 450 and 600°C, which is confirmed from both XRD and TGA. On nickel doping, an intermediate phase formed and there occurred two transition temperatures in TGA. NixFe2?xO3-600 forms rhombohedral phase, while NixFey?xOz-450 forms a mixture of rhombohedral and inverse spinel structures till 2 wt% nickel concentration and pure inverse spinel structure above 2 wt% of nickel doping. M–H curves of samples from vibrating sample magnetometer (VSM) show the ferrimagnetic behaviour of both NixFey?xOz-450 and NixFe2?xO3-600 except Fe2O3-600 which shows antiferromagnetic behaviour. In both set of samples, saturation magnetisation increases with increasing nickel concentration. Further, a two-probe method was used to study electrical and dielectric properties of the samples. AC conductivity (?ac), dielectric constant (??) and loss factor (tan ?) of NixFey?xOz-450 decreased with increase in 2 wt% nickel concentration and then increased with further increase in nickel, whereas these factors varied randomly with increasing nickel concentration for NixFe2?xO3-600. ?ac, ?? and tan ? values of NixFe2?xO3-600 are lower than those of NixFey?xOz-450, which can be attributed to the formation of hematite phase at 600 °C. © 2019, Springer-Verlag GmbH Germany, part of Springer Nature.Item PMMA-LZO Composite Dielectric Film with an Improved Energy Storage Density(Springer New York LLC barbara.b.bertram@gsk.com, 2019) Kishor Kumar, M.J.; Kalathi, J.T.Energy storage materials in modern electronic devices and renewable energy systems are inevitable. The incorporation of inorganic fillers into the polymer matrix is a promising option for the advancement of storage materials with high energy density. The agglomeration of inorganic fillers in the polymer matrix and phase separation remain the main obstacles to efficient applications of the composites for energy storage. Here, the primary attention was given to achieve a uniform distribution of high-k LZO (Lanthanum Zirconium Oxide) filler into a PMMA (Polymethylmethacrylate) matrix to enhance the dielectric constant and energy storage density of PMMA while keeping dielectric loss at minimum. We prepared PMMA-LZO composite films with variable LZO content by ultrasound-assisted mixing followed by spin coating the solution on ITO (Indium tin oxide) coated glass. The effect of LZO content on dielectric properties of the LZO-PMMA films was studied. Dielectric constant (k) of PMMA was found to be increased from 3.1 to 15.3 at 15 vol.% LZO loading with a dielectric loss of 0.0582. However, 10 vol.% LZO loaded PMMA showed an improved dielectric constant of 13.4 while the dielectric loss remained the same as that of the neat PMMA. The LZO-PMMA films with 10 vol.% and 15 vol.% of LZO loading exhibited maximum energy density of 5.94 J cm?3 and 6.53 J cm?3, respectively. Overall, the 10 vol.% LZO loading was found to be optimum to achieve a stable film with improved dielectric properties. This work provides a viable approach for the development of flexible, high-energy density materials with a minimum dielectric loss. © 2019, The Minerals, Metals & Materials Society.