Papers by Dinesh Rangappa
Journal of Materials Chemistry, 2011
ABSTRACT In this paper, we report the preparation of systematically size and shape controlled LiM... more ABSTRACT In this paper, we report the preparation of systematically size and shape controlled LiMnPO4nanocrystals under supercritical fluid conditions. The effect of different reaction conditions such as the reaction time, temperature, surfactant and precursor concentration on the size and shape of the LiMnPO4nanocrystals was studied in detail. It was noticed that shorter reaction time and lower reaction temperature facilitated the formation of crystalline LiMnPO4nanocrystals with size 10 nm. The nanocrystals ranging from 7 to 24 nm were obtained by controlling different reaction conditions. The formation mechanism for the LiMnPO4nanocrystals is proposed based on the obtained results. The effect of nanosize on the electrochemical properties of LiMnPO4nanocrystals was studied. Improved electrochemical performance was observed for 20 nm sized LiMnPO4 after conductive carbon coating. This study indicates the importance of LiMnPO4nanocrystals below 50 nm size in improving the electrochemical performance of LiMnPO4 cathodes.
Asian Journal of Chemistry/Asian journal of chemistry, Apr 30, 2024
This study represents the synthesis, characterization of ZnO nanoparticles and encapsulated compo... more This study represents the synthesis, characterization of ZnO nanoparticles and encapsulated composites with MWCNT, sodium dodecyl sulfate (SDS) and cetyltrimethylammonium bromide (CTAB) for the lubricating performance in petrol engine oil. The facile sol-gel process was used to synthesize ZnO and ZnO-based nanocomposites followed by annealing at 500 ºC. ZnO-based nanocomposite samples were prepared by adding different secondary encapsulating agents such as MWCNT (with different wt.% of 1, 2 and 3), SDS and CTAB. The as-synthesized ZnO and ZnO-based nanocomposite samples were further dispersed in 20W40 grade engine oil separately by taking 50 mL volume of oil. Different amounts of the synthesized samples of 50 mg, 100 mg and 150 mg were blended with the lubricant accordingly by the sonication process. After that the viscosity performances were carried out for all the prepared samples. The dynamic and kinematic viscosity were measured using a redwood viscometer and the temperature varied throughout the analysis at 34, 44 and 55 ºC to observe the optimum temperature effect on viscosity performance. The objective of this work is to determine the temperature effects on the viscosity of commercial lubricant 20W40 grade by blending with different suspended novel nanomaterials.
InTech eBooks, Jun 28, 2011
Journal of Molecular Liquids, Feb 1, 2022
Bulletin of Materials Science, Jul 18, 2021
Starch was isolated from ragi grains using alkali extraction method. Crystallinity of isolated ra... more Starch was isolated from ragi grains using alkali extraction method. Crystallinity of isolated ragi starch (RGS) was studied using X-ray diffraction technique, and thermal properties of RGS were characterized by differential scanning calorimetry. Novel ragi starch (RGS) based gel electrolyte for dye-sensitized solar cells (DSSCs) was prepared and characterized for the first time. In the first part, the effects of additives guanidinium thiocyanate (GSCN) and N-methylbenzimidazole (NMBI) on the photovoltaic performance of DSSC were investigated. Considerable improvement of open circuit voltage was found in the addition of only NMBI to the electrolyte, while only addition of GSCN has an influence on the short circuit current. Synergetic effects were observed when NMBI and GSCN were used together in the gel electrolyte. In the second part, various weight percentages of multiwalled carbon nanotubes (MWCNTs) were added to observe the cell performance. DSSCs fabricated with the optimum weight percentage (1 wt%) of MWCNT achieved a maximum conversion efficiency of 4.34%, an open circuit voltage (Voc) of 0.803 V, short circuit current density (Jsc) of 9.54 mA cm–2 and fill factor (FF) of 56.59%. Here we reported the novel ragi starch-based gel electrolytes for DSSC application along with the effect of different additives, such as GSCN, NMBI, and various weight percentages of MWCNTs incorporated into the gel electrolyte.
Ceramics International, Dec 1, 2022
Materials Research Bulletin, Nov 1, 2008
ABSTRACT Alkaline earth molybdates, such as BaMoO4 and SrMoO4, films have been successfully fabri... more ABSTRACT Alkaline earth molybdates, such as BaMoO4 and SrMoO4, films have been successfully fabricated on a Mo metal substrate in AOH (A = Ba, Sr) solutions by a ball-rotation-assisted solution reaction, at room temperature. The dissolution of Mo was mainly controlled by the concentration of the H2O2 oxidizing agent and ball-rotation to form MoO42− in the solution. AMoO4 was deposited on the substrate by the reaction between MoO42− and A2+ ions without any high energy or high-temperature treatment. Also, the mass transport of alkaline earth ions onto the solid/solution interface was improved as a result of the vigorous solution agitation by the ball-rotation. Therefore, the rate of deposition of the AMoO4 films was accelerated by the ball-rotation. A decrease in the grain size of the film was observed with an excessive ball-rotation.
Ceramics International, Apr 1, 2021
Systematic analysis of SiO 2 @CaTiO 3 :Dy 3+ (3 mol %) :Li + (0.25-1 mol %) core shell nanopartic... more Systematic analysis of SiO 2 @CaTiO 3 :Dy 3+ (3 mol %) :Li + (0.25-1 mol %) core shell nanoparticles (C-S NPs) were carried out. CaTiO 3 :Dy 3+ (3 mol %) , Li + (0.25-1 mol %) NPs were prepared using low temperature solution combustion method. C-S structured samples were synthesized using SiO 2 in equal weight quantities. All samples were characterised by powder X-ray diffraction (PXRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) in order to study and compare its structural properties. Photoluminescence (PL) properties of uncoated and SiO 2 coated samples were studied in detail and optimum luminescence behaviour was investigated. Higher luminescence intensity is observed for codoped CaTiO 3 :Dy 3+ (3 mol %) :Li + (0.5 mol %) sample. Further enhancement was observed in SiO 2 @CaTiO 3 :Dy 3+ :Li + structured nanoparticles. Emission spectra of SiO 2 @CaTiO 3 :Dy 3+ (3 mol %) :Li + (0.25-1.0 mol %) C-S nanophosphors exhibit white emission dominated by 4 F 9/2 → 6 H 13/2 (570 nm) transition of Dy 3+ ions under. All the results suggested that the present material provides a platform for fabricating new functional materials which can be applied in the field of wLEDs and solid state display applications.
ACS omega, Dec 9, 2021
This paper presents guanidine-functionalized Fe3O4 magnetic nanoparticle-supported palladium (II)... more This paper presents guanidine-functionalized Fe3O4 magnetic nanoparticle-supported palladium (II) (Fe3O4@Guanidine-Pd) as an effective catalyst for Suzuki–Miyaura cross-coupling of aryl halides using phenylboronic acids and also for selective reduction of nitroarenes to their corresponding amines. Fe3O4@Guanidine-Pd synthesized is well characterized using FT-IR spectroscopy, XRD, SEM, TEM, EDX, thermal gravimetric analysis, XPS, inductively coupled plasma-optical emission spectroscopy, and vibrating sample magnetometry analysis. The prepared Fe3O4@Guanidine-Pd showed effective catalytic performance in the Suzuki–Miyaura coupling reactions by converting aryl halides to their corresponding biaryl derivatives in an aqueous environment in a shorter reaction time and with a meagerly small amount of catalyst (0.22 mol %). Also, the prepared Fe3O4@Guanidine-Pd effectively reduced nitroarenes to their corresponding amino derivatives in aqueous media at room temperature with a high turnover number and turnover frequency with the least amount of catalyst (0.13 mol %). The most prominent feature of Fe3O4@Guanidine-Pd as a catalyst is the ease of separation of the catalyst from the reaction mixture after the reaction with the help of an external magnet with good recovery yield and also reuse of the recovered catalyst for a few cycles without significant loss in its catalytic activity.
Electrochimica Acta, Apr 1, 2012
The fascinating properties of graphene are attracting considerable attention in engineering field... more The fascinating properties of graphene are attracting considerable attention in engineering fields such as electronics, optics, and energy engineering. These properties can be controlled by controlling graphene's structure, e.g., the number of layers and the sheet size. In this study, we synthesized nanosized graphene from a platelet-type carbon nanofiber. The thickness and size of nanographene oxide are around 1 nm and 60 nm and we obtained nanographene by hydrazine reduction of nanographene oxide. We applied the nanographene to an ionic-liquid electric double-layer capacitor (EDLC), which exhibited a much larger capacitance per specific surface area than an EDLC using conventional activated carbon. Furthermore, the capacitance increased significantly with increasing cycle time. After 30th cycle, the capacitance was achieved 130 F g −1 , though the surface area was only 240 m 2 g −1. These results suggest that nanographene structure induce the capacitance enhancement.
Journal of Power Sources, Mar 1, 2017
Solidified flexible hybrid electrolyte was designed and demonstrated. Hybrid electrolyte achieved... more Solidified flexible hybrid electrolyte was designed and demonstrated. Hybrid electrolyte achieved an high ionic conductivity and low activation energy. Hybrid electrolyte is suitable for a flexible and safe battery with Li anode.
Chemical Communications, 2010
We have used common and cheap solvent ethanol as SCF medium. All the chemicals were purchased fro... more We have used common and cheap solvent ethanol as SCF medium. All the chemicals were purchased from Wako, chemicals. Firstly, precursor solution was prepared by dissolving FeCl 2 .4H 2 O (0.4 mmol) in 20 ml oleylamine (60 mmol) and 16 ml ethanol at constant temperature of 60 o C for 1 hour. Solutions of o-H 3 PO 4 (0.4 mmol) and Li acetyl acetonate (0.4 mmol) were prepared by dissolving each compound separately in 2 ml of ethanol. These solutions were slowly added to the above mixture under constant stirring. In a typical synthesis, about 5 ml of precursor solution was charged into 10 cc 3 volume stainless steel reactor and heated up to 250-400 o C temperatures and 38 MPa pressure for 4-10 min. Then, the reaction was terminated by quenching the reactor with cold water bath. The resultant LiFePO 4 nanocrystals were collected by repeated washing and centrifugation with ethanol, followed by drying in a vacuum dry oven at 120 o C for 12 hours.
Transactions on Electrical and Electronic Materials, May 8, 2023
International journal of engineering research and technology, Apr 24, 2018
This paper deals with an experimental study of an inexpensive Concrete Photovoltaic Thermal Colle... more This paper deals with an experimental study of an inexpensive Concrete Photovoltaic Thermal Collector (PV/T)total aperture area of 0.36 m2, used for the simultaneous production of heat and electricity. The Concrete PV/T is characterised by a thin cement concrete slab which performs the function of collecting, absorbing and storing of the solar thermal energy. Above the concrete slab PV cells were pasted .Inside the concrete absorber PVC pipe , copper pipe and Brass pipe are embedded .Outdoor experiments were carried out under varied environmental conditions for several days during two consecutive months (from February to March 2017). The experiments were carried out by measuring the climatic variables, temperatures in different parts of the collectors, and mass flow rates of water, during the test days. Based on these measurements, the behaviour of the systems was analysed. A detailed analysis was carried out for evaluating the thermal performance of the Concrete PV/T under given operating conditions. The results obtained from the Concrete PV/T system were compared with the results obtained from a Conventional Solar PV/T system composed of a flat-plate collector (with a total aperture area of 1m2) tested at the same time.
Journal of Power Sources, 2017
Proceedings of the National Academy of Sciences, India, Section B: biological sciences, May 10, 2023
Materials Today: Proceedings, 2017
In this paper we present a flexible super capacitor which has huge scope towards wearable electro... more In this paper we present a flexible super capacitor which has huge scope towards wearable electronic devices as power supplies. A simple, low-cost, flexible and high-performance supercapacitor consisting of Reduced Graphene Oxide (RGO)/Manganese dioxide (MnO 2) hybrid electrodes have been developed. The as-synthesized self-supporting Reduced Graphene Oxide(RGO)/Manganese dioxide(MnO 2) hybrid electrodes are assembled in the form of solid-state Super capacitor devices with phosphoric acid-polyvinyl alcohol(H 3 PO 4-PVA)as separator.The resultant product are characterized by powder X-ray diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR),Scanning electron microcopy (SEM), and Electrochemical Measurements. The average crystalline size of MnO 2 particles is about 25nm.MnO 2 nanoparticles on RGO uniformly deposited on RGO sheets.
Materials Today: Proceedings, 2017
Fig.1. Systematic scheme for photocatalytic activity Highlights •Pristine and air quenched ZnO na... more Fig.1. Systematic scheme for photocatalytic activity Highlights •Pristine and air quenched ZnO nanoparticles were synthesized by simple combustion method. • Synthesized ZnO for air quenched ZnO has better optoelectronic properties. • ZnO nanoparticles for air quenched ZnO exhibiting complete photodegradation of Methyl Orange dye under UV irradiation. •Photocatalytic activities for all the samples were observed in 150 min.
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Papers by Dinesh Rangappa