Wmo Arts And Science College

Kalpetta, India

Wmo Arts And Science College

Kalpetta, India
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Pazhani R.,Electronic Materials Research Laboratory | Padma Kumar H.,Wmo Arts And Science College | Moses Ezhil Raj A.,Scott Christian College | Solomon S.,St Johns College | Thomas J.K.,Electronic Materials Research Laboratory
Journal of Alloys and Compounds | Year: 2011

Phase pure zirconium oxide powders have been synthesized using the single step auto-ignition combustion method, the particles were nanometer sized (20 nm) and the size distribution was very narrow (3.4 nm). Systematic structural characterization revealed the t-ZrO 2 and indexed for its tetragonal structure (a = 3.5975 and c = 5.1649 ). Calculated microstrain in most of the plane indicated the presence of compressive stress (65-288 MPa) along various planes of the particles. Observed space group (P4 2/nmc) revealed the presence of cations in the 8e positions (0.75, 0.25, 0.75) and the anions in the 16 h positions (0.25, 0.25, 0.4534). The metal-oxide (Zr-O) band observed at the low wavenumber region further confirmed the phase purity of the as-prepared ZrO 2 nanopowders. Peaks at the binding energy positions 2.042 and 0.525 keV in the energy dispersive X-ray spectrum revealed oxygen deficient zirconia. The particle size estimated by TEM was in good agreement with the results obtained through X-ray line broadening (20.81 nm) measurements. The nanopowders were sintered to above 98% of the theoretical density by using vacuum sintering technique at a relatively low temperature of 1300 °C. Stable tetragonal ZrO 2 experimentally yield the permittivity value of about 28 at 10 MHz. © 2011 Elsevier B.V. All rights reserved.


Thomas J.K.,Electronic Materials Research Laboratory | Kumar H.P.,Wmo Arts And Science College | Prasad V.S.,Indian National Institute for Interdisciplinary Science and Technology | Solomon S.,St Johns College
Ceramics International | Year: 2011

High quality nanoparticles of barium hafnate have been synthesized using an auto-ignition modified combustion technique. The nanoparticles thus obtained have been characterized by powder X-ray diffraction, thermo gravimetric analysis, differential thermal analysis, Fourier transform infrared spectroscopy and transmission electron microscopy. The XRD studies have shown that the as-prepared BaHfO3 powders are phase pure. The particle size of the as-prepared powder was in the range 20-50 nm. The nanopowder could be sintered to 95% of the theoretical density at 1650 °C for 2 h. The ultrafine cuboidal nature of nanopowders with small degree of agglomeration improved the sinterability at relatively lower temperature and time. The microstructure of the sintered surface was examined using scanning electron microscopy. The dielectric constant (εr) of 30.8 and loss factor (tan δ) of 2.3 × 10-3 were obtained at 1 MHz. © 2010 Elsevier Ltd and Techna Group S.r.l.


Bagchi J.,Inter-University Center for Astronomy and Astrophysics | Vivek M.,Inter-University Center for Astronomy and Astrophysics | Vikram V.,University of Pennsylvania | Hota A.,Center for Excellence in Basic science | And 6 more authors.
Astrophysical Journal | Year: 2014

The radio galaxy phenomenon is directly connected to mass-accreting, spinning supermassive black holes found in the active galactic nuclei. It is still unclear how the collimated jets of relativistic plasma on hundreds to thousands of kiloparsec scales form and why they are nearly always launched from the nuclei of bulge-dominated elliptical galaxies and not flat spirals. Here we present the discovery of the giant radio source J2345-0449 (z = 0.0755), a clear and extremely rare counterexample where relativistic jets are ejected from a luminous and massive spiral galaxy on a scale of ∼1.6 Mpc, the largest known so far. Extreme physical properties observed for this bulgeless spiral host, such as its high optical and infrared luminosity, large dynamical mass, rapid disk rotation, and episodic jet activity, are possibly the results of its unusual formation history, which has also assembled, via gas accretion from a disk, its central black hole of mass >2 × 108 M ⊙. The very high mid-IR luminosity of the galaxy suggests that it is actively forming stars and still building a massive disk. We argue that the launch of these powerful jets is facilitated by an advection-dominated, magnetized accretion flow at a low Eddington rate onto this unusually massive (for a bulgeless disk galaxy) and possibly fast spinning central black hole. Therefore, J2345-0449 is an extremely rare, unusual galactic system whose properties challenge the standard paradigms for black hole growth and the formation of relativistic jets in disk galaxies. Thus, it provides fundamental insight into accretion disk-relativistic jet coupling processes. © 2014. The American Astronomical Society. All rights reserved.


Kumar H.P.,Wmo Arts And Science College | Thomas J.K.,Mar Ivanios College | John A.,St Johns College | Solomon S.,St Johns College
Bulletin of Materials Science | Year: 2011

The effect of PbO addition on the structural, processing and microwave dielectric properties of LnTiTaO6 (Ln = Ce, Pr and Nd) ceramics are reported. Conventional solid state ceramic route was used for the preparation of samples. Phase pure LnTiTaO6 (Ln = Ce, Pr and Nd) ceramics are prepared at a calcination temperature of 1300°C. The samples are sintered at optimized temperatures. Addition of PbO reduces the sintering temperature. The crystal structure of the materials was analysed using X-ray diffraction techniques and the surface morphology of the sintered samples was analysed using scanning electron microscopy. The dielectric constant at microwave frequency range decreases for higher PbO addition for all the samples but the quality factor improves on small PbO addition. The thermal stability of resonant frequency was also improved with PbO addition on all the systems. A number of samples with improved microwave dielectric properties were obtained on all the systems suitable for practical applications. © Indian Academy of Sciences.


Thomas J.K.,Electronic Materials Research Laboratory | Padma Kumar H.,Wmo Arts And Science College | Solomon S.,St Johns College | Mathai K.C.,Electronic Materials Research Laboratory | Koshy J.,Electronic Materials Research Laboratory
Journal of Alloys and Compounds | Year: 2010

Nanocrystalline strontium hafnate (SrHfO3) was synthesized through auto-ignited combustion technique. The X-ray diffraction studies of SrHfO3 nanoparticles have shown that the as-prepared powder was single phase, crystalline, and has an orthorhombic (Pmna) perovskite structure (ABO3). The phase purity of the powder was further examined using; thermo gravimetric analysis, differential thermal analysis, and Fourier transform infrared spectroscopy. The transmission electron microscopy study showed that the particle size of the as-prepared powder is in the range 20-60 nm with a mean size of 40 nm. The nanopowder could be sintered to 98% of the theoretical density at 1620 °C for 3 h. The microstructure of the sintered surface was examined using scanning electron microscopy. The dielectric constant (εr) of 25.13 and loss factor (tan δ) of 5.3 × 10-3 were obtained at 1 MHz. © 2010 Elsevier B.V. All rights reserved.

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