Faculty Publications

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    Growth and temperature dependent electrical properties of ZnO nanostructures
    (2013) Santhosh Kumar, A.; Nagaraja, K.K.; Nagaraja, H.S.
    Zinc oxide (ZnO) nanostructured films are grown using Polyvinyal alcohol (PVA)-citric acid modified sol gel process and the effect of (0, 1, and 2Wt%) PVA content on growth, crystallanity, microstructure and electrical properties are investigated. The XRD patterns confirm that the films are polycrystalline nature. 1 Wt% assisted grown samples are found to be good crystallanity with (002) preferred orientation. The SEM micrographs confirm that the 1 Wt% PVA assisted grown films are composed of vertically oriented ∼1.2 μm length nanorods. The temperature dependent electrical resistivity of the films has been measured using the four-probe method. The electrical resistivity found to be 7.08 ω-cm at room temperature for vertically oriented nanorods composed films, which are grown using 1Wt% PVA. © 2013 AIP Publishing LLC.
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    Structural stability studies of graphene in sintered ceramic nanocomposites
    (Elsevier Ltd, 2014) Inam, F.; Vo, T.; Badekai Ramachandra, B.R.
    The post-sintering structural stability of graphene in alumina nanocomposites synthesised by Spark Plasma Sintering (SPS) and Hot Pressing (HP) was compared. Raman spectroscopy, thermogravimetric analyses and electrical conductivity analyses were conducted to characterise degradation of graphene due to the utilisation of different sintering techniques and conditions. Scanning Electron Microscopy confirmed good dispersion of graphene in SPSed and HPed sample. Graphene in SPSed and HPed nanocomposite samples sintered using longer durations (60 min) were found to possess higher crystallinity, thermal stability and electrical conductivity as compared to SPSed samples sintered using shorter sintering durations (10-20 min). This was attributed to the thermally induced graphitisation caused by longer sintering durations, which was lacking in SPSed samples processed using shorter sintering durations and lower temperature. No additional effect of DC pulsed current on the structural stability of graphene for nanocomposites were observed for samples prepared by SPS. © 2014 Elsevier Ltd and Techna Group S.r.l.
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    Synthesis and photocatalytic properties of graphitic carbon nitride nanofibers using porous anodic alumina templates
    (Institute of Physics Publishing helen.craven@iop.org, 2017) Suchitra, S.M.; Udayashankar, N.K.
    In the present study, we describe an effective method for the synthesis of Graphitic carbon nitride (GCN) nanostructures using porous anodic alumina (AAO) membrane as template by simple thermal condensation of cyanamide. Synthesized nanostructure was fully analysed by various techniques to detect its crystalline nature, morphology, luminescent properties followed by the evaluation of its photocatalytic activity in the degradation of Methylene blue dye. Structural analysis of synthesized GCNNF was systematically carried out using x-ray powder diffraction (XRD) and scanning electron microscope (SEM), and. The results confirmed the growth of GCN inside the nanochannels of anodic alumina templates. Luminescent properties of GCNNF were studied using photoluminescence (PL) spectroscopy. PL analysis showed the presence of a strong emission peak in the wavelength range of 350-600 nm in blue region. GCNNF displays higher photocatalytic performance in the photodegradation of methylene blue compare to the bulk GCN. Highlights 1. In the present paper, we report the synthesis of graphitic carbon nitride nanofibers (GCNNF) using porous anodic aluminium oxide membranes as templates through thermal condensation of cyanamide at 500 °C. 2. The synthesis of Graphitic carbon nitride nanofibers using porous andic alumina template is the efficient approach for increasing crystallinity and surface area. 3. The high surface area of graphitic carbon nitride nanofibers has a good impact on novel optical and photocatalytic properties of the bulkGCN. 4. AAO templating of GCN is one of the versatile method to produce tailorable GCN nanostructures with higher surface area and less number of structural defects. 5. Towards photocatalytic degradation of dyes, the tuning of physical properties is very essential thing hence we are succeeded in achieving better catalytic performance of GCN nanostructures by making use of AAO templates. © 2017 IOP Publishing Ltd.
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    Effect of indium content on the characteristics of indium tin oxide thin films
    (Institute of Physics Publishing helen.craven@iop.org, 2018) Navya, K.; Bharath, S.P.; Bangera, K.V.; Shivakumar, G.K.
    Transparent IxT1-xO (x = 0 to 1) alloyed thin films were deposited by spray pyrolysis technique at a substrate temperature of 400 °C. The effect of incorporation of indium on structural, optical and electrical properties of tin oxide thin films were studied. Characterization of thin films was carried out using x-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive x-ray spectroscopy (EDAX), UV-Visible absorption spectroscopy. XRD results revealed that IxT1-xO thin films were polycrystalline in nature with good crystallinity. Incorporation of indium effectively modifies the surface morphology of the films. The band gap was varied from 3.7 eV to 3 eV. Maximum electrical conductivity of 44.52 × 103 ?-1 m-1 and transmittance of 90% is obtained for I0.5T0.5O films, hence can be used as highly transparent and conducting electrodes. © 2018 IOP Publishing Ltd.
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    Influence of microballoon wall thickness on dynamic mechanical analysis of closed cell foams
    (Institute of Physics Publishing helen.craven@iop.org, 2019) Doddamani, M.
    Thermoplastics are most commonly used in industrial and consumer products. The growing interest in making them lightweight is always a priority in industrial practices. Investigations on thermoplastic based closed cell foams wall thickness variations for dynamic mechanical analysis (DMA), and crystallinity are scarce. The present study investigates storage modulus, loss modulus, damping, and % crystallinity as a function of glass microballoon/high-density polyethylene (GMB/HDPE) foam wall thickness and volume fraction variations. Crystallinity percentage variation in HDPE and their foams are analyzed through DSC traces. GMBs are mixed with HDPE in plasticorder, and subsequently, GMB/HDPE composite blend is compression molded. Varying wall thickness (particle density variations) GMB particles across three different volume fractions (20, 40 and 60%) are prepared. Storage modulus, loss modulus, and damping are observed to be increasing with particle wall thickness and volume fraction as compared to HDPE matrix resin. Thick walled GMB particle with the highest GMB content registered enhanced storage modulus compared to thin walled ones at lower temperatures. DMA properties increase with increasing wall thickness. Damping is noted to be less sensitive than the storage and loss modulus. Crystallinity is observed to be decreasing with increasing wall thickness and GMB content. Higher crystalline phase contributes towards DMA properties at lower filler loadings while higher wall thickness plays a vital role at higher filler content. © 2020 IOP Publishing Ltd.
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    A single step unique microstructural growth of porous colossal dielectric constant titanium oxide
    (Springer Verlag service@springer.de, 2019) Meti, S.; Hosangadi Prutvi, S.P.; Rahman, M.R.; Bhat K, U.K.
    New microstructure of TiO 2 grown in hydrothermal process is reported on. The influence of hydrothermal process parameters, such as heating temperature, on growth dynamics is also reported. The improvement in surface area and crystallinity are reached by the hydrothermal process, as compared to other growth techniques. The synthesized TiO 2 is characterized by XRD technique and subjected to Rietveld analysis. The results indicate that the obtained TiO 2 is of tetragonal structure. The results of other characterization techniques such as micrography, Raman spectroscopy and TGA are also reported. The obtained TiO 2 is tested for its electrical properties and it shows good dielectric strength in the flat band region from 40 Hz to 1 MHz. © 2019, Springer-Verlag GmbH Germany, part of Springer Nature.
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    Durable, efficient, and flexible piezoelectric nanogenerator from electrospun PANi/HNT/PVDF blend nanocomposite
    (John Wiley and Sons Inc. cs-journals@wiley.com, 2019) Khalifa, M.; Mahendran, A.; Anandhan, S.
    Currently, there is considerable research focus on portable, lightweight, shock-resistant, and inexpensive wearable devices that are ideally powered by harvesting abundant mechanical or vibration energy, making battery or related wiring superfluous. In this study, piezoelectric nanogenerator was electrospun from PANi (polyaniline)/HNT (halloysite nanotube)/PVDF (poly[vinylidene fluoride]) blend nanocomposite. Polymorphism, crystallinity and morphology of the nanogenerator were explored in detail. HNT and PANi acted as a nucleating agent and conductive filler, respectively in PVDF; their synergism helps improve the piezoelectric performance of PVDF. The piezoelectric performance of the nanogenerator patch was studied under various external mechanical stresses, such as pressure, tapping, and impact. A maximum voltage output of approximately 7.2 V was generated by the nanogenerator under impact. The nanogenerator patch attached to human arm exhibited not only excellent piezoelectric response during arm movements, but, also proved to be flexible, highly sensitive and durable. This nanogenerator could possibly be used in wearable piezoelectric energy conversion application for self-powered devices. POLYM. COMPOS., 40:1663–1675, 2019. © 2018 Society of Plastics Engineers. © 2018 Society of Plastics Engineers
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    One step synthesis of silver nanowires using fructose as a reducing agent and its antibacterial and antioxidant analysis
    (Institute of Physics Publishing helen.craven@iop.org, 2019) Sharma, D.; Rakshana, D.A.; Mohan Balakrishnan, R.M.; JagadeeshBabu, P.E.
    Silver nanowires were synthesised using hydrothermal method by reducing silver nitrate (AgNO3) using fructose in the presence of poly-vinylpyrrolidone (PVP). The parameters such as the effect of process temperature, AgNO3 molarity, PVP and fructose (C6H12O6) concentration influencing the synthesis of silver nanowires (Ag NWs) were investigated. The scanning electron microscope (SEM) images showed that ultra-long, uniform and thin silver nanowires were obtained under optimized conditions; 0.02 M AgNO3, 0.016 g ml-1 of fructose, 0.16 g ml-1 of PVP at 160 °C within 22 h. The dynamic light scattering (DLS) analysis revealed that the silver nanowires obtained have an average diameter of 77 nm possessing high level of crystallinity with face centered cubic (fcc) phase that is evident from the x-ray diffraction (XRD) patterns peaked at (111), (200), (220), (311) and (222) planes. FT-IR (Fourier transform infrared spectroscopy) results suggested that there is adsorption of PVP molecules on the silver atoms. Ag NWs exhibited better antibacterial activity against Escherichia coli and high antioxidant activity against 2,2-diphenyl-1- picrylhydrazyl (DPPH) free radical scavenger. This work gives a green approach to the hydrothermal synthesis of Ag NWs using fructose with a promising antibacterial and antioxidant properties. © 2019 IOP Publishing Ltd.
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    Self-powered flexible piezoelectric nanogenerator made of poly (vinylidene fluoride)/Zirconium oxide nanocomposite
    (Institute of Physics Publishing helen.craven@iop.org, 2019) Naik, R.; Somasekhara Rao, T.
    The electroactive ?-phase is the most desirable due to its highest piezo-, pyro-, and ferroelectric properties in Poly (vinylidene fluoride) (PVDF). The ?-phase can be nucleated by incorporation of nanoparticles into PVDF. The objective of this study is the preparation and characterization of the pristine PVDF film, and intensified dosages of the ZrO2 modified composite PVDF films, further piezoelectric properties of nanocomposites films are evaluated. The nanocomposite films have been prepared by solution casting method with different loadings of ZrO2. The prepared films are characterized by Scanning electron microscope (SEM), x-ray diffraction (X-RD) analysis, Fourier transform infrared spectra (FTIR), and Differential scanning calorimetry (DSC), to study surface morphology, ?-phase content, crystallinity, and melting temperature. The experimental analysis shows that the ?-phase percentage and melting temperature of the films increases with ZrO2 loading, but the percentage of crystallinity decreases. Nanogenerators are fabricated by using the films, and piezoelectric performances of the nanogenerators are evaluated under various external stresses. The maximum voltage generated in the case of 5 wt% loading of ZrO2 is 1560 mV for 100 g of load, which is approximately eight times higher than the voltage generated in the pristine-PVDF and 2.2 V is generated while tapping by hand. © 2019 IOP Publishing Ltd.
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    Eco-friendly lightweight filament synthesis and mechanical characterization of additively manufactured closed cell foams
    (Elsevier Ltd, 2019) Patil, B.; Bharath Kumar, B.R.; Bontha, S.; Balla, V.K.; Powar, S.; Hemanth Kumar, V.H.; Suresha, S.N.; Doddamani, M.
    Environmentally pollutant fly ash cenospheres (hollow microballoons) are utilized with most widely consumed, relatively expensive high density polyethylene (HDPE) for developing lightweight eco-friendly filament for 3D printing of closed cell foams. Cenospheres (20, 40 and 60 by volume %) are blended with HDPE and subsequently extruded in filament to be used for 3D printing. Cenosphere/HDPE blends are studied for melt flow index (MFI) and rheological properties. MFI decreases with cenospheres addition. Complex viscosity, storage and loss modulus increase with filler loading. DSC results on the filament and printed samples reveal increasing crystallization temperature and decreasing crystallinity % with no appreciable change in peak melting temperature. Cooling rate variations exhibit crystallinity differences between the filament and the prints. CTE decreases with increasing cenosphere content resulting in lower thermal stresses and under diffusion of raster leading to non-warped prints. Micrography on freeze fractured filament and prints show cenospheres uniform distribution in HDPE. Intact cenospheres lower the foam density making it lightweight. Tensile tests are carried out on filaments and printed samples while flexural properties are investigated for 3D prints. Cenospheres addition resulted in improved tensile modulus and decreased filament strength. Tensile and flexural modulus of printed foams increases with filler content. Results are also compared with injection molded samples. Printed foams registered comparable tensile strength. Specific tensile modulus is noted to be increased with cenospheres loading implying weight saving potential of 3D printed foams. Property map reveals printed foams advantage over other fillers and HDPE composites synthesized through injection and compression molding. © 2019 Elsevier Ltd