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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 | Year: 2014

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.


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 | Year: 2013

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.


Satish T.N.,Gas Turbine Research Establishment | Murthy R.,Gas Turbine Research Establishment | Singh A.K.,Center for Piezoceramics and Devices
Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering | Year: 2014

The rotor tip clearance in a gas turbine engine varies throughout the engine operating regime. It has considerable influence on the engine performance. Blade to casing rub is imminent at certain operating points of the engine. Mechanical rub at high speeds could damage the total engine hardware. A precise measurement helps to obtain the optimum engine performance with safe engine operation. In this article a typical case study related to fan clearance measurement is discussed, where indications of a proven measurement system is not in agreement with the physical event during engine test. Centrifugal, thermal, assembly and wear effects can affect tip clearance measurement. Centrifugal forces untwist the blade tip, resulting in change in the effective area of the target that is seen by capacitance sensor. Relative component growths due to thermal effect result in the displacement of the sensor from its original position. This could induce error into this measurement. Assembly errors are seen during blade to disc assembly. Wear occurs under the action of centrifugal loading and vibration in compressor blades dovetail roots that are attached to the disc. This leads to wear in involved metal surfaces and it could be a source of error in this measurement. Measurement system also has its own uncertainty. During the current work all sources of errors were evaluated. Probable actual running clearance on the engine and reasons for the mismatch in indication were successfully arrived at through analytical and experimental studies. This work has provided an insight into probable sources of errors and their treatment methodologies using analytical and experimental techniques. This has helped in identifying the changes needed in the calibration procedure, methods to reduce the measurement system uncertainty band and measurement procedure. © IMechE 2013 Reprints and permissions: sagepub.co.uk/ journalsPermissions.nav.


Nwathore N.,Center for Piezoceramics and Devices | Lonkar C.M.,Center for Piezoceramics and Devices | Kharat D.K.,Center for Piezoceramics and Devices
Bulletin of Materials Science | Year: 2011

The effect of temperature on polarization reversal of strontium-doped lead zirconate titanate ceramics was studied. The piezoelectric properties viz. dielectric constant and piezoelectric coupling coefficient, were used for polarization reversal characteristic. These properties and apparent coercive field weremeasured during polarization reversal at different temperatures. Results indicated that at higher temperature apparent coercive field decreased. Polarization reversal and further polarization reversal was quite asymmetric. After polarization reversal, dielectric constant was found to increase at all temperatures while piezoelectric coupling coefficient increased above the temperature of polarization. The trend shown by dielectric constant indicates that at 25°C, 1.5 kV/mm field can be applied safely to this material without much compromising the properties. D.c. field of 3.0 kV/mm and 100°C temperature can be predicted as poling parameters from their effect on k p. Apparent coercive field has shown non-linear relationship with temperature. It was of exponential decay type. © Indian Academy of Sciences.


Singh A.K.,Center for Piezoceramics and Devices
Indian Journal of Pure and Applied Physics | Year: 2013

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.


Premkumar S.,Center for Piezoceramics and Devices | Shinde S.D.,Center for Piezoceramics and Devices | Kumar H.H.,Center for Piezoceramics and Devices | Kharat D.K.,Center for Piezoceramics and Devices
Proceedings - ISPTS-1, 1st International Symposium on Physics and Technology of Sensors | Year: 2012

Many actuator applications require high resolution, accuracy and fast response time. Piezoelectric multi-layer actuators are used for such applications to manage displacements from nanometer to micrometer range and the response time in microseconds at comparatively low drive voltages. This paper deals with the characterization of lead zirconate titanate (PZT) ceramic multilayer actuators fabricated by tape casting method utilizing impedance analysis and strain measurements. Width mode resonance frequency is predicted using finite element analysis. The electrical impedance spectrums in the frequency range 100 kHz to 250 kHz of PZT multilayers show a small change in resonant behavior. Possible reasons for this change are discussed. Presence of defect in the multi-layer actuator is validated by optical microscopy. The results also show the displacement response at 75V of defect free PZT multilayer actuator. © 2012 IEEE.


Singh A.K.,Center for Piezoceramics and Devices | Raykar V.S.,Center for Piezoceramics and Devices
Materials Research Innovations | Year: 2013

In this paper, we have examined the effect of surface plasmon resonance (SPR) of silver nanostructures on the effective thermal conductivity (TC) of silver nanofluids (NFs). The results show that the type of capping ligand and its interaction with nanoparticles with temperature are two important phenomena in characterising the SPR of silver NFs. A polyvinylpyrrolidone ligand is found to be favourable for both TC and SPR increment, while 2,2′-bipyridine shows only TC enhancement. The ligand layer structure and its change in heat transfer properties according to the applied physical variables are responsible for the change in SPR dependent effective thermal conductivity (ETC) properties of NFs. © W. S. Maney & Son Ltd. 2013.


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.


Singh A.K.,Center for Piezoceramics and Devices | Nakate U.T.,Indian Defence Institute of Advanced Technology
The Scientific World Journal | Year: 2014

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.


PubMed | Indian Defence Institute of Advanced Technology and Center for Piezoceramics and Devices
Type: | Journal: TheScientificWorldJournal | Year: 2014

We report synthesis of ZrO nanoparticles (NPs) using microwave assisted chemical method at 80C temperature. Synthesized ZrO NPs were calcinated at 400C 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 ZrO phases having crystallite size of the order 8.8nm from most intense XRD peak as obtained using Scherrer formula. Electron microscope analysis shows that the NPs were less than 10nm and highly uniform in size having spherical morphology. BET surface area of ZrO NPs was found to be 65.85m/g with corresponding particle size of 16nm. The band gap of synthesized NPs was found to be 2.49eV and PL spectra of ZrO synthesized NPs showed strong peak at 414nm, which corresponds to near band edge emission (UV emission) and a relatively weak peak at 475 and 562nm.

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