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Maity T.,University College Cork | Goswami S.,Indian Central Glass and Ceramic Research Institute | Bhattacharya D.,Indian Central Glass and Ceramic Research Institute | Roy S.,University College Cork
Physical Review Letters | Year: 2013

We observe an enormous spontaneous exchange bias (∼300-600 Oe) - measured in an unmagnetized state following zero-field cooling - in a nanocomposite of BiFeO3 (∼94%)-Bi2Fe4O 9 (∼6%) over a temperature range 5-300 K. Depending on the path followed in tracing the hysteresis loop - positive (p) or negative (n) - as well as the maximum field applied, the exchange bias (HE) varies significantly with -HEp>HEn. The temperature dependence of HE is nonmonotonic. It increases, initially, till ∼150 K and then decreases as the blocking temperature TB is approached. All these rich features appear to be originating from the spontaneous symmetry breaking and consequent onset of unidirectional anisotropy driven by "superinteraction bias coupling" between the ferromagnetic core of Bi2Fe4O9 (of average size ∼19 nm) and the canted antiferromagnetic structure of BiFeO3 (of average size ∼112 nm) via superspin glass moments at the shell. © 2013 American Physical Society.

Saha J.,Indian Central Glass and Ceramic Research Institute | De G.,Indian Central Glass and Ceramic Research Institute
Chemical Communications | Year: 2013

Cubic (Im3m) mesoporous silica nanofibers were successfully prepared using a new F127-PVA-SiO2 tri-constituent assembly approach by the electrospinning technique. PVA was used to protect the F127 directed cubic micelles which usually deform during electrospinning. The preformed Au NPs can be loaded inside the mesopores of the nanofibers. © 2013 The Royal Society of Chemistry.

Ghosh S.,Indian Central Glass and Ceramic Research Institute | Naskar M.K.,Indian Central Glass and Ceramic Research Institute
RSC Advances | Year: 2013

Mesoporous γ-Al2O3 nanorods were synthesized by a reverse microemulsion (water in oil, w/o) technique using an aqueous-based alumina sol, the anionic surfactant AOT (sodium bis(2-ethylhexyl sulfosuccinate)), the non-ionic co-surfactant Span 80 (sorbitan monooleate) and cyclohexane as an organic solvent. The γ-Al2O3 phase was obtained at 500 °C with a slight transformation to -Al 2O3 at 700 °C-900 °C, while a mixed phase of γ-,and α-Al2O3 resulted at 1000 °C. The BET surface area, pore volume and average pore size of the 500 °C-treated sample was found to be 59.3 m2 g-1, 0.040 cm3 g-1 and 2.65 nm respectively, which changed slightly in the temperature range of 500 °C-900 °C. The mesoporous γ-alumina nanorods were formed through rod-like micelle formation in the presence of surfactant/co-surfactant in organic solvent, which was illustrated by a proposed mechanism. This journal is © The Royal Society of Chemistry 2013.

Ghosh S.,Indian Central Glass and Ceramic Research Institute | Naskar M.K.,Indian Central Glass and Ceramic Research Institute
Journal of the American Ceramic Society | Year: 2014

Mesoporous alumina (MA)was synthesized by sol-gel based evaporation-induced self-assembly process using aluminum isopropoxide as alumina source in the presence of three different types of triblock copolymers (TBCs), F68, F127, and L64. The role of different TBCs as surfactants on thermal, crystallization, textural, and microstructural properties of the alumina powders was studied. To understand the effects of different copolymers, the adsorption efficiency of the samples for Congo red (CR) was studied. For all the surfactants, the XRD results showed the stability of γ-Al2O3 phase up to 1000°C for 1 h dwell time. A maximum value (431.8 m2/g) of Brunauer- Emmet-Teller surface area was obtained for the 400°C-treated powder prepared from F68 surfactant. The transmission electron microscopy micrograph exhibited worm-like mesoporous structures of the 400°C-treated powders prepared from F68 and F127 surfactants. The adsorption performance for CR of the 400°C-treated powders for different surfactants was in the order of F68 > F127 > L64. A tentative mechanism was illustrated to understand the roles of different block copolymers on the properties of the prepared MA. © 2013 The American Ceramic Society.

Mishra M.K.,Indian Central Glass and Ceramic Research Institute | De G.,Indian Central Glass and Ceramic Research Institute
Journal of Materials Chemistry C | Year: 2013

Multicoloured fluorescent nanocomposite films containing homogeneously dispersed Cu ion-doped Cd0.5Zn0.5S alloy QDs capped by P123 and organically modified SiO2 have been fabricated. The concentration of QDs in the film is as high as 40 mol% with respect to the equivalent SiO2. The cured transparent films showed strong photoluminescence covering the entire visible window with very high quantum yield ensuring applications. © 2013 The Royal Society of Chemistry.

Som T.,Indian Central Glass and Ceramic Research Institute | Karmakar B.,Indian Central Glass and Ceramic Research Institute
Plasmonics | Year: 2010

A novel series of elliptical gold (Au0) nanoparticles (18-40 nm) embedded antimony glass (K2O-B2O3-Sb2O3) dichroic nanocomposites have been synthesized by a single-step melt-quench in-situ thermochemical reduction technique. X-ray and selected area electron diffractions manifest growth of Au0 nanoparticles along the (111) and (200) crystallographic planes. The transmission electron microscopic image reveals elliptical Au0 nanoparticles having an aspect ratio varying in the range 1.2-2.1. The dichroic behavior of the nanocomposites arises due to elliptical shape of the Au0 nanoparticles. These nanocomposites show strong surface plasmon resonance (SPR) band of Au nanoparticles in the range 610-681 nm and it exhibit red-shifts with increasing Au concentration. They, when co-doped with Sm2O3 and excited at 949 nm, exhibit about sevenfold enhancement of the upconverted red emission transition of 4G5/2→6H9/2 at 636 nm due to local electric field enhancement effect of Au0 nanoparticles induced by its SPR. These nanocomposites are the promising materials for laser, display, and various nanophotonic applications. © Springer Science+Business Media, LLC 2010.

Naskar M.K.,Indian Central Glass and Ceramic Research Institute
Journal of the American Ceramic Society | Year: 2010

Alumina nanoparticles were synthesized following hydrothermal process at 170°C for 6 h, using glucose and other water-based precursor materials. The uncalcined and calcined (550°-1200°C) particles were characterized by differential thermal analysis, thermogravimetry, Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and multipoint Brunauer-Emmett-Teller (BET) surface area. The microstructures of the calcined (at 550°C) particles were examined by field-emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM). XRD and FTIR studies revealed that gamma-alumina (γ-Al2O3) persisted up to 1000°C followed by the appearance of alpha-alumina (α-Al2O3) at 1200°C. BET surface area analysis confirmed that the specific surface area of γ-Al2O3 was higher compared with α-Al2O3. Because of particle agglomeration, the crystallite sizes obtained by the BET method showed larger values than those determined by the XRD method for the samples calcined at 550°-1200°C. For 550°C-treated sample, FESEM micrograph showed the aggregated particles of size 20-80 nm, while TEM image of the same sample revealed a particle size of 5-10 nm. © 2010 The American Ceramic Society.

Dikshit A.K.,Indian Central Glass and Ceramic Research Institute
Polymer - Plastics Technology and Engineering | Year: 2012

The role of different organic polar solvents containing methylene group on rheological behaviour of coated polyimide precursor on silica optical fibre were investigated at different concentrations and temperatures with respect to corresponding original precursor itself. The influence of keto-methyl and N-methyl polar groups are in different chemical structure of organic solvents into the coated precursor against-solvent dilution process has been explored. The interaction in between functional groups moiety containing into precursor and polar methyl group of solvents was also analysed. A substantial knowledge of rheology into coating precursor of polyimide is an important issue to coat successfully into optical fibre. © 2012 Copyright Taylor and Francis Group, LLC.

Jana D.,Indian Central Glass and Ceramic Research Institute | De G.,Indian Central Glass and Ceramic Research Institute
Journal of Materials Chemistry | Year: 2011

Stable and well-dispersed Ag nanoparticles were generated by spontaneous reduction of AgNO 3 in the partially acetylacetonato complexed aluminium tri-sec-butoxide solution without using any additional reducing agent. The addition of higher concentration of AgNO 3 caused agglomeration of Ag nanoparticles resulting in precipitation. Use of polyvinylpyrrolidone as capping agent not only prevents the agglomeration but also causes a controlled growth of Ag nanoparticles in different shapes in alumina sol. The addition of varying concentrations of polyvinylpyrrolidone caused transformation of yellow alumina sol to green and blue coloured sol. These changes were due to the conversion of spherical (yellow) to a mixture of hexagonal and triangular (green), and finally truncated/filleted triangular (blue) Ag nanoparticles. These yellow, green and blue coloured alumina sols were used to prepare different shaped Ag nanoparticle doped optically transparent amorphous alumina films on glass substrates. The shape conversions of the Ag nanoparticles were studied systematically by UV/visible spectrometry, transmission electron microscopy and grazing incidence X-ray diffraction, and a mechanism of growth of the Ag nanoparticles in alumina sol was established. © 2011 The Royal Society of Chemistry.

Dikshit A.K.,Indian Central Glass and Ceramic Research Institute
Optical Materials | Year: 2012

I present here the study of optical and fluorescence properties, structure and morphology of silica nanoparticles bearing laser dye molecules are electrostatically attached with high refractive index organic dopant in acrylic optical preform rod. The photo physical fluorescence behaviour of laser dye molecules at the surface of different size and shape of silica nanoparticles has been reported. The interaction of laser dye-nanoparticles, nature of particles, and effect of various sizes and shapes of silica nanoparticles on fluorescence properties has been investigated. The developed optical preform has high potential for possible applications as bio-analysis sensor probe. © 2012 Elsevier B.V. All rights reserved.

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