IR@CGCRI - Central Glass and Ceramic Research Institute (CSIR)
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Development of chromium doped nanoengineered YAS glass based optical fibers with and without rare-earths for use as a saturable absorber to make pulse fiber laser along with broadband sources
No full textThe demand of high bandwidth in optical communications as well as increasing need
for tunable fiber laser source and laser cavity components like fiber saturable absorber for allfiber
application lead to search for new materials that can serve for said purposes and besides
provide other applications like fiber dosimetry. In this dissertation, chromium especially in
+4 state in glass core of preform has been fabricated (using MCVD solution doping method)
and drawn to fiber to investigate their different properties. Although chromium in different
crystal hosts and in some kind of glasses is known to posses desired properties but those are
not reported in case of fiber-based system. Nevertheless, the development of such Cr-doped
fiber is challenging because of multiple bottlenecks such as chromium evaporation problem,
stabilization of Cr+4, achieving nano-phase separated core etc. Accordingly, various material
characterization techniques viz. Scanning Electron Microscopy, Transmission Electron
Microscopy, X-ray Photoelectron Spectroscopy, X-Ray Diffraction, Electron Probe Micro
Analysis etc. are used to optimize different process parameters to achieve the desire target.
Nano-engineering of core glass in terms of nano-phase separation has been
administrated by thermal annealing and investigated using optical and material
characterizations. The compositional variations and microscopic study between the phases in
phase separated core glass was carried out by spot energy dispersive X-ray in conjunction
with TEM. Other fabrication method like powder-in-tube (PIT) was also tried using wet
chemical method for synthesis of YAG crystal powder followed by fiber implementation and
respective characterizations.
Some representative fabricated yttria-alumino-silicate (YAS) based fibers were set for
experiment. Presence of different oxidation states including the desired +4 state is inferred
from absorption spectra and emission spectra at NIR region with proper excitation
wavelength. Fluorescence lifetime, photo-bleaching and Raman spectra are also investigated
besides study on influence of divalent alkaline earth ions towards retention of Cr+4 ion in
ultimate fiber core.
The fibers were also set for the experiment regarding the electron irradiation effect
resulting characteristic induced absorption and its posterior optical bleaching property (at
633/1070 nm wavelengths) has been investigated. In this experiment we also established that
the desired properties of fibers are depends on Cr+4 ion whose amount in turn determined on
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some divalent alkaline earth ions (Mg here). The study indicates the potentiality of the
fabricated fibers in dosimetric application.
Another important feature, saturable absorption, has been studied at 1.55 μm and 2
μm region for some representative fabricated fibers. Incorporating them in different laser
cavities (EDFL and TDFL) show pulsed laser output, even nanosecond pulse (EDFL
produces 432 ns pulse width, while TDFL produces 59 ns pulse width) also achieved.
Effect of chromium codoping on rare-earths like erbium (Er) doped fiber has also
been studied due to the overlapping fluorescence band of both ions expecting improvement in
erbium lasing. The fabricated fibers were compared with pure erbium doped fiber shows
improvement in terms of the ratio of bleached to residual resonant absorption and net-gain to
small signal absorption emerges as useful for core pumping NIR applications. Besides,
reduced up-conversion phenomena and long NIR fluorescence lifetimes put positive remark
on the fabricated fibers
27R-SiAlON Reinforced AlN Composite: Synthesis, Sintering and Characterization
No full textSynthesis of powder containing a dual phase mixture of 27R-SiAlON and AlN has been successfully carried out through carbothermal reduction and nitridation route. The probable reaction sequences of formation have been identified through the analysis of transient appearances of intermediate phases associated with parameters like loss of carbon, oxygen and weight as well as nitrogen uptake. Formation of 27R-SiAlON takes place through further reaction of a primary polytype phase, Si3Al7O3N9. FTIR spectra provide supplementary evidence for supporting the revealed model of reaction sequences. Particles are agglomerative in nature consisting of fine grains, as low as below 50 nm in size. Spark plasma sintering was applied for an initial densification trial of this bi-phasic powder without externally added sintering aid. The densified samples exhibited elongated grain-reinforced composite microstructure with improved properties over monolithic AlN
‘Cotton-ball’ shaped porous iron-nickel sulfide: A high-rate cathode for long-life aqueous rechargeable battery
No full textAqueous rechargeable batteries (ARB) offer reasonably higher energy density and cycle life than their non-aqueous counterparts. Yet, the bottleneck is a limited choice of positive electrodes coupled with low-rate capability and inadequate cycle life. We report here a wet chemical approach to synthesize in-situ three-dimensional (3D) ‘cotton-ball’ shaped porous iron-nickel sulfide (FeNi2S4) (henceforth referred to as PINS) as a diffusion-controlled ARB electrode. It shows a high specific capacity of 177 mA h g−1 at 1 A g−1 vs Pt in the alkaline electrolyte with excellent rate capability (89 mA h g−1 at 40 A g−1) and ultra-long cycle life (10,000 cycles). Furthermore, a pouch-type full-cell ARB (FeNi2S4//AC) delivers an energy density of 56.7 Wh kg−1 at a power density of 871.5 W kg−1 with high cycling stability (10,000 cycles). The present study offers a straightforward and efficient approach for developing nanostructured transition metal sulfide-based cathode materials for practical ARB
Homogeneous and polymorphic transformations to ordered intermetallics in nanostructured Au-Cu multilayer thin films
No full textAtomic arrangements in the nanostructured grains and interfaces of thermally evaporated Au/Cu multilayer thin films on polycrystalline Si substrate have been explored through GIXRD, HRTEM, simulation, and direct structure imaging. GIXRD pattern conforms to cF4 solid solution of Au and Cu with peak broadening and shift. Comparative analysis with simulation indicated the presence of cP4, tP4, oP8, and oI40 phases in the multilayer. The Cu layer is amorphous. Localized amorphous phase forms at the Cu-Si interface due to the impingement of Cu atoms during deposition. Interfaces of Au-Cu are wavy. The Au layer is polycrystalline and columnar with some twin-like defects present in them. At the Cu-Au interface, diffusionally grown cP4, tP4, oI40, and oP8 phases could be observed. Adatom mobility, concurrent growth, and coalescence of growth islands lead to columnar growth. Ordered intermetallic phases could be related with the cF4 solid solution phase through polymorphism. The strain associated with the polymorphs and the solid solution phase is quite small. Faceted semi-coherent interfaces of the ordered phases with the solid solution phase have been resolved. The ordered phases grow into the solid solution matrix by homogeneous transformation. Structure imaging of the ordered phases indicated that most of the time a cluster of atoms is imaged in these structures. The interfaces are likely to be chemically diffused in nature. Polymorphism and homogeneous nature of the transformation at low temperature allows local transformation to ordered phases, that explain the phase field ambiguity in the binary phase diagram. Such structural details are critical in understanding the novel properties in these nanostructured alloys
Modulation of resistive switching properties of non-stoichiometric WO3-x based asymmetric MIM structure by interface barrier modification
No full textThe impact of device operation condition and ambient moisture on the interface-type resistive switching (RS) characteristics of a non-stoichiometric polycrystalline tungsten oxide (WO3-x) based metal-insulator-metal device with an Au top electrode and a Pt bottom electrode has been investigated. The device exhibits rectification and stable bipolar RS characteristics without the need for any forming step, where the switching is primarily dominated by the Schottky type Au/WO3-x interface. DC conduction characteristics of the device have been investigated at different temperature, bias stress, and relative humidity conditions. Current conduction through the active layer has been found to be dominated by Schottky emission at low electric field and Poole-Frenkel emission at high electric field. An increase in current and a strong reduction in the rectification characteristic have been observed on subjecting the device to DC bias stress of appropriate polarity as well as increasing ambient moisture. Modification of the Schottky barrier due to defect redistribution when DC bias stress is applied and due to the dipoles induced at the Au/WO3-x interface by water molecules with increasing ambient moisture content have been discussed as a possible mechanism of the observed RS modulation
Structural, Morphological, and Optical Properties of Ag-Doped TiO2 Thin-Film over Fiber Optic Substrate for Sensing Applications
No full textAg-doped TiO2 (rAg/Ti, r 1−3 = 2, 4, 6 wt%) is synthesized by a hydrothermal technique. Different characterizations, that is, X-ray powder diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) analysis, photoluminescence (PL) spectra analysis, X-ray photoelectron spectroscopy (XPS), field emission scanning electron microscope (FESEM), energy dispersive X-ray analysis (EDX), and Brunauer–Emmett–Teller (BET) analysis, are conducted to study the utility of the developed thin-film material as a sensing medium over the fiber substrate. The as-prepared material is hydrothermally deposited over the optical fiber to construct a fiber optic sensing probe. The optical properties of TiO2 are simulated theoretically by MATLAB simulation that reveals that optical absorption appears at the wavelength of 763 nm. The initial performance of the rAg/Ti-based optical fiber is investigated with the amine group in the range of 500−1500 ppm and a satisfactory response is found toward ethylenediamine (EDA) analytes with average sensitivity (S av, in %) as 41.81 at 1200 ppm
Studies on processing of layered oxide-bonded porous sic ceramic filter materials
No full textOxide-bonded porous SiC ceramic filter supports were prepared using SiC powder (d(50) = 212 mu m), Al2O3, and clay as bond forming additives and graphite as pore former following reaction bonding of powder compacts at 1400 degrees C in air. Reaction bonding characteristics, phase composition, porosity, pore size, mechanical strength, and microstructure of porous SiC ceramic supports were investigated. Mullite bond phase formation kinetics was studied following the Johnson-Mehl-Avrami-Kolmogorov (JMAK) model using non-isothermal differential thermal analysis (DTA) data. Compared to porous SiC ceramic filter supports having no needle-like mullite bond phase, materials processed by the mullite bonding technique exhibited higher average strength (22.1%) and elastic modulus (5.4%) at a similar porosity level of similar to 38%, with upper and lower bounds of their strength, modulus, and porosity being 39.1 MPa, 40.2 GPa, and 36.3% and 34.2 MPa, 31.3 GPa, and 33.0%, respectively. Spray coating method was applied for preparation of oxidation-bonded SiC filtration layer having thickness of similar to 150 mu m and pore size of similar to 5-20 mu m over the porous SiC support compacts using aqueous slurry made of fine SiC powder (d(50) = 15 mu m) followed by sintering. The layered ceramics thus prepared are potential materials for gas filter applications
Sol-gel derived cobalt containing Ni-Zn ferrite nanoparticles: Dielectric relaxation and enhanced magnetic property study
No full textA systematic study of transitional metal ion doped nickel-zinc ferrite (NZF) nanoparticles with its magnetic properties and conductivity relaxation mechanism are the objectives of this research. We have prepared cobalt doped NZF nanoparticles (NZCo) via a facile chemical route. X-Ray Diffraction (XRD) and Transmission Electron Microscopy (TEM) analyses suggest the formation of single phase nearly spherical nanoparticles around 60 nm in size. UV-Vis study reveals the redshift of the optical band gap for doped samples. Estimation of particle size using the effective mass model agrees well with TEM/XRD results. The electrical modulus spectra have been analyzed using Harvilliak-Negami model function. Migration energy has been found to be the minimum for 10 mol % doped sample. Frequency-dependent modulus spectra have been converted to time domain data and the relaxation process shows Kohlrausch-Williams-Watts (KWW) type behavior. Carrier motion inside the lattice has been found to be strongly correlated. Room temperature magnetization curve shows that very weak AFM/PM contribution and strong FM interaction inside the system as well as non-collinear spin arrangements between interstitial sites. Law of Approach (L.A.) analysis of the AFM/PM part subtracted hysteresis curve delineates the enhanced magnetic properties such as saturation magnetization, anisotropy constant and coercivity. Multifunctional materials of such kind with optimum behavior at specific doping percentages can be fruitful for electronic industries
Probing the binding interaction of zinc (II) Schiff bases with bovine serum albumin: A spectroscopic and molecular docking study
No full textEntrapping of potent Schiff base with biomimetic environment using fluorescence properties enables better understanding of their interaction for drug-based application. A detailed photophysical study of zinc (II) Schiff bases, 2,6-bis((E)-((2-(dimethylamino) ethyl)imino)methyl)-4-R-phenol, where R = methyl/tertiary butyl/chloro is reported by utilizing bovine serum albumin (BSA) as the bio membrane. Steady state absorption and emission studies of Schiff base-protein system have been found to get altered by change in the compartmental ligand. Alternation of polarity caused by such compartmental ligands is reported by comparing the fluorescence behavior of the probes in microheterogeneous environment in a mixture of dioxane and water of varying composition. Hildebrand equation accounts for negative binding constants among BSA with Schiff base with Cl (-I) group as the compartmental ligand in contrast to the positive magnitudes with ligands exhibiting +I effect. Functionality of such compartmental ligands (intra interactions studied using Hirshfeld analyses) upon binding with the protein is also studied in terms of quenching and denaturation studies. Schiff base with Me is found to be the most favorable ligand that bound to BSA as corroborated from the binding, quenching, micropolarity, and docking studies. Molecular docking studies predict the affinity energies for suitable binding conformations to be similar to - 6 kcal mol(-1) for BSA-Schiff base (with Me ligand)
Radiation-induced effects on micro-scratch of ultra high molecular weight polyethylene biocomposites
No full textSterilization of ultra-high molecular weight polyethylene (UHMWPE) based composites used for acetabular cup liner via UV or gamma-irradiation before surgery is inevitable. Thus, understanding the alteration of mechanical properties and wear resistance of cup liner via irradiation process requires investigation. This paper aims to understand the effect of UV (0.03 J/cm(2)) and gamma (25 kGy) irradiation on mechanical properties and scratch resistance of compression molded UHMWPE composites reinforced with alumina (Al2O3), hydroxyapatite (HAp) and carbon nanotubes (CNTs). After irradiation, nearly 100% increased crystallinity of polyethylene, due to recrystallization, helped in enhancing the hardness and elastic modulus by similar to 1.5 times compared to that of as-processed UHMWPE (Hardness: similar to 70 MPa and Elastic modulus: similar to 1.25 GPa). The recrystallization was not favored by the presence of nano-reinforcements in irradiated UHMWPE based nanocomposites, and caused deterioration in the mechanical properties. The micro-scratch results revealed the remarkable wear resistance (i.e., 1.5 to 2 times lower wear rate) of irradiated samples than that of as-processed samples. Mouse fibroblast L929 in vitro cell culture test confirmed the cytocompatibility of irradiated samples. This study indicated that the UV and gamma irradiated UHMWPE nanocomposites are the challenging candidates as acetabular cup liner. (c) 2021 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/)