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Singh A.K.,Center for Piezoceramics and Devices
Indian Journal of Pure and Applied Physics

Carbon nanotubes (CNTs)-polymethyl methacrylate (PMMA) nanocomposites have been developed for electromagnetic wave absorption (EWA) and dynamic strain sensing in for structural health monitoring. For the purpose CVD synthesized CNTs were characterized for its structural and morphology using X-ray diffraction (XRD) patterns and scanning electron microscopy (SEM) before preparing nanocomposite. The CNTs obtained were of about 10 nm diameter and 0.5 μm length. The prepared CNT/PMMA nanocomposite films (CNT 5% loading) were characterized for their electrical proprities, indicating metallic (resistive) behaviour and electromagnetic absorbance (EWA) behaviour in the X and Ku band showing absorption peaks of around 3.5 dB loss at 8.5 GHz and 20 dB loss at 14.5 GHz. The peppered CNT/PMMA nanocomposite films were used in strain sensor applications for structural health monitoring. The strain sensor results closely matched with standard strain gauge sensor under quasi static as well as dynamic conditions. Source

In this investigation, a cost effective approach has been developed to fabricate photoelectrochemical (PEC) solar cell on cheap steel substrate sensitized with natural dye and performance has been compared with CdS quantum dots (QDs) sensitized PEC cell. The performance of natural dye sensitized PEC cells has been found to be better than QDs senstitized cell and comparable to conventional high cost ITO-FTO based solar cell which makes use of costly synthetic dyes. For the purpose, microwave synthesis of TiO2 and electrophoretic deposition(EPD) of porous, high qualityTiO2 thin films on steel substrate using microwave synthesized nanocrystaline TiO2 has been carried out. The prepared TiO2 thin films were sensitized using natural dyes and QDs of CdS for PEC cell application. Effect of different sensitizers on TiO2 photoanodes was studied using 1M KOH electrolyte in a PEC cell using electrochemical impedance spectroscopy (EIS). Conversion of visible light into electricity has been accomplished using these cells with natural sensitizer providing short circuit current density (Jsc) and open circuit voltage (Voc) values comparable to conventional high cost traditional dyes. The maximum Jsc and Voc are found to be 450.40μAcm−2 and 242.43 mV, respectively, under 10mWcm−2 of illumination for natural dye. © 2014 Bentham Science Publishers. Source

Rath S.K.,Naval Materials Research Laboratory NMRL | Dubey S.,CSIR - National Chemical Laboratory | Kumar G.S.,Indian Defence Institute of Advanced Technology | Kumar S.,Indian Institute of Technology Kharagpur | And 5 more authors.
Journal of Materials Science

A simple two-step process was used to disperse acid functionalized multi-walled carbon nanotubes (CNTs) in poly(vinylidene fluoride) (PVDF). While the neat solvent-cast PVDF showed coexistence of α- and β-phases; the composite films exhibited only β-phase crystals. Further studies on the crystalline behaviour, using differential scanning calorimetry and small-angle X-ray scattering techniques showed an increase in the percentage of crystalline phase with CNT. The network formed by CNTs in the matrix reduced the macroscopic electrical resistivity of composite films. The dielectric constant increased with CNT loading. Further, these composites were investigated for its electromagnetic wave absorbance (EWA) and strain sensing properties. The EWA properties were studied in the X-band (6-12 GHz) region. A maximum of ∼37 dB reflectivity loss at ∼9.0 GHz was obtained in a ∼25 μm thick PVDF film containing only 0.25 wt% of functionalized CNT. Preliminary studies showed a systematic change in electrical resistance by the application of dynamic bending strain in nanocomposite film. The film also showed a significant improvement in mechanical stiffness owing to efficient stress transfer from matrix to filler, the property desirable for a good strain sensor. In view of the unique combination of EWA and electro-mechanical properties, the nanocomposite films are expected to serve as a multifunctional material for strain sensing in health monitoring as well as in radar absorption. © 2013 Springer Science+Business Media New York. Source

Singh A.K.,Center for Piezoceramics and Devices | Nakate U.T.,Indian Defence Institute of Advanced Technology
The Scientific World Journal

We report synthesis of ZrO2 nanoparticles (NPs) using microwave assisted chemical method at 80°C temperature. Synthesized ZrO2 NPs were calcinated at 400°C under air atmosphere and characterized using FTIR, XRD, SEM, TEM, BET, and EDS for their formation, structure, morphology, size, and elemental composition. XRD results revealed the formation of mixed phase monoclinic and tetragonal ZrO2 phases having crystallite size of the order 8.8 nm from most intense XRD peak as obtained using Scherrer formula. Electron microscope analysis shows that the NPs were less than 10 nm and highly uniform in size having spherical morphology. BET surface area of ZrO2 NPs was found to be 65.85 m2/g with corresponding particle size of 16 nm. The band gap of synthesized NPs was found to be 2.49 eV and PL spectra of ZrO2 synthesized NPs showed strong peak at 414 nm, which corresponds to near band edge emission (UV emission) and a relatively weak peak at 475 and 562 nm. © 2014 A. K. Singh and Umesh T. Nakate. Source

Barkade S.S.,North Maharashtra University | Pinjari D.V.,Institute of Chemical Technology | Singh A.K.,Defence Institute of Advanced Technologies DIAT | Singh A.K.,Center for Piezoceramics and Devices | And 6 more authors.
Industrial and Engineering Chemistry Research

Polypyrrole-zinc oxide (PPy/ZnO) hybrid nanocomposites have been synthesized using an ultrasound assisted in situ miniemulsion polymerization of pyrrole in the presence of ZnO nanoparticles. This synthesis approach results in the formation of hybrid functional colloidal particles with uniform size of around 100 nm, which can be used as a sensor for the detection of liquefied petroleum gas (LPG). FTIR analysis shows that the ZnO nanoparticles were encapsulated by the polymerized polypyrrole. Results obtained from TEM and X-ray diffraction analysis indicate that the PPy/ZnO composite particles give evidence of the crystalline nature of ZnO (Wurtize) and a well-defined hybrid nanocomposite structure, which is suitable for LPG sensor development. The controlled size of the hybrid particles obtained using this innovative synthesis strategy minimizes the response time to sense the LPG significantly (2.2 min for PPy/ZnO). The LPG sensing mechanism for the PPy(p-type)/ZnO(n-type) heterojunction has been presented through a change in the height of the barrier potential. © 2013 American Chemical Society. Source

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