IR@CGCRI - Central Glass and Ceramic Research Institute (CSIR)
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An efficient wideband hafnia-bismuth erbium co-doped fiber amplifier with flat-gain over 80 nm wavelength span
No full textA new wideband erbium doped fiber amplifier (EDFA) is proposed and demonstrated, utilizing a newly fabricated hafnia-bismuth erbium co-doped fiber (HB-EDF) as a gain medium. The proposed amplifier is tested in both double-pass series and parallel configurations, using 22 cm and 150 cm long HB-EDFs to realize amplification in C and L-band wavelength region, respectively. Both series and parallel configurations obtained a wideband operation at wavelength region from 1520 to 1610 nm. At input signal power of -10 dBm, the parallel HB-EDFA achieved a flat gain of 12.1 dB with a gain ripple of less than 2 dB, along the wavelength region of 80 nm from 1525 to 1605 nm. Within the flat gain region, the noise figure was less than 11.8 dB. Overall, the parallel HB-EDFA has a better performance than the series HB-EDFA
The effect of 980 nm and 1480 nm pumping on the performance of newly Hafnium Bismuth Erbium-doped fiber amplifier
Get PDFAn experimental study on the comparison of optical amplifying performance between 980 nm and 1480 nm pumping for the newly Hafnium Bismuth Erbium co-doped fiber (HB-DF) has been presented. A short length of 1-meter HB-EDF was used as the gain medium of the optical amplifier. 1480 nm pumping is found to provide higher attainable gain and lower noise figure compared to 980 nm pumping. At 1480 nm pumping, the average small signal gain for HB-EDFA in the single pass configuration has improved by 13.4 dB in the C-band region range from 1525 nm to 1565 nm. In the double-pass configuration, a maximum small signal gain of 36.6 dB was achieved at the wavelength of 1560 nm, this is 11.6 dB higher compared to the HB-EDFA with 980 nm pumping. The double pass HB-EDFA with 1480 nm pumping has exhibited a reduction of average noise figure by 23.4% and 29.8% for-30 dBm and-10 dBm of input signal power respectively in the C- and L-band region
Densification, Microstructure, and Tribomechanical Performance of SPS-Processed 27R-SiAlON Polytype-Reinforced AlN: A Comparison Between Continuous and Pulsed Direct Current Mode
No full textThe effects of current conduction modes of spark plasma sintering (SPS) (within the temperature range of 1800 degrees C to 2000 degrees C) on densification, microstructure, and tribomechanical properties of indigenously processed, additive-free AlN reinforced with 27R-SiAlON polytype (prepared by carbothermal-reduction-nitridation technique) have been reported. Sintering curves and density data of sintered specimens under pulsed direct current mode (PM) show improved densification over continuous direct current mode. The reason for enhanced density under PM may be due to the enhanced electrical discharge within the capacitor banks formed on the insulating surface of SiAlON particles. Low-temperature sintered specimen principally contained equiaxed grains, while higher sintering temperature promoted elongation in grains. The denser composite (maximum being sintered at 2000 degrees C) offered much improved Vickers hardness and indentation fracture toughness in comparison to those for less dense specimens. Composites sintered under PM show the existence of elongated 27R-SiAlON grains. These elongated grains facilitate enhanced energy dissipation through crack bridging and deflection, which are the key factors behind obtaining the higher toughness of the dense composite. Unlubricated linear scratch experiments also indicated better wear resistance of the higher temperature sintered specimen. The present study establishes the suitability of using PM during SPS processing of AlN composite reinforced with 27R-SiAlON polytype that offers satisfactory tribomechanical performance. (C) The Minerals, Metals & Materials Society and ASM International 201
Synthesis of Eu2O3 doped BaO-TiO2-GeO2 based glass-ceramics: Crystallization kinetics, optical and electrical properties
No full textEu3+ doped transparent glass-ceramics (GCs) containing non-centrosymmetric ferroelastic Ba2TiGe2O8 (BTG) crystals as the major crystalline phase have been synthesized. BTG crystal phase was generated in the glass matrix with mole percent composition 30BaO-15TiO(2)-55GeO(2) synthesized by melt quenching technique followed by controlled crystallization through ceramming heat-treatment. A diffusion controlled surface crystallization event with zero and constant nucleation rates was determined through a comparative study of some linear and nonlinear solid state reaction models. Nonlinear crystallization kinetics studies facilitated determination of the experimental ceramization temperature and time for fabrication of transparent glass-ceramics containing BTG nanocrystals. XRD, FTIR, TEM and FESEM measurements confirmed the dispersion of BTG nanocrystals of size 20-100 nm in the glass matrix. Local crystal environment around Eu3+ ions facilitated the enhancement of photoluminescence of glass-ceramics with respect to the precursor glass. High dielectric constant, low loss and dissipation factors were observed for the GCs
Carbon@carbon double hollow spheres as efficient cathode host for high rate Li-S battery
No full textDevelopment of carbon materials for lithium-sulfur (Li-S) battery that can confine the sulfur species effectively while serving as a conductive matrix for high rate performance has attracted intense research interest. Herein, we report designing of a double hollow spherical carbon (C@C) by using RF resin coated SiO2 as an exo-template. The developed C@C/S cathode could host about 69.1 wt% of S and exhibits a high specific capacity of 1396 mAh g(-1) at 0.05 C corresponding to 83.5% of S utilization. Furthermore, the cathode could sustain a current rate of 5 C (8.4 A g(-1)) and still delivers a reasonable capacity of 320 mAh g(-1) with excellent electrochemical stability at this high rate with no apparent capacity fading for 100 cycles. The present results highlight the importance of morphological pre-design for developing advanced carbon materials as Li-S cathode host
Facet-Dependent Photodegradation of Methylene Blue Using Pristine CeO2 Nanostructures
Get PDFThis work comprises the shape-and facet-dependent catalytic efficacies of different morphologies of CeO2, namely, hexagonal, rectangular, and square. The formation of different shapes of CeO2 is controlled using polyvinyl pyrrolidone as a surfactant. The surface reactivity of formation of differently exposed CeO2 facets is thoroughly investigated using UV-visible, photoluminescence, Raman, and X-ray photoelectron spectroscopies. A correlation between the growth of a surface-reactive facet and the corresponding oxygen vacancies is also established. Considering the tremendous contamination, caused by the textile effluents, the present study articulates the facet-dependent photocatalytic activities of pristine CeO2 for complete degradation of methylene blue within 175 min. The observed degradation time deploying pristine CeO2 as a catalyst is the shortest to be reported in the literature to our best knowledge
Optimization of melting parameters and minimizing OH content in SiO2-B2O3-Na2O-BaO glass system in microwave heating
No full textThis study investigates the optimization of melting process for the glass comprising SiO2-B2O3-Na2O-BaO under microwave (MW) heating. Batches were melted at different temperatures in the range of 900-1250 degrees C to optimize melting condition. X-ray diffraction suggests amorphous nature of samples melted above 1150 degrees C. Optimization of melting time was carried out by varying soaking time (8-60 minutes) at 1250 degrees C. UV-Vis-NIR spectra reveal similar to 90% transmission over 300-2000 nm wavelength range for glass melted at 1250 degrees C. Optical microscopic images suggest that the bubble-free glass can be produced at 1250 degrees C for 1 hour melting in MW heating. MW heating also helps in reducing OH content in glass. However, OH concentration is found to increase with melting time. OH content could be minimized to 68.56 ppm in glass employing oxygen atmosphere melting, which prevents OH diffusion from atmosphere into the melt. Residual stresses are estimated to be less in MW heating than conventional heating. Maximum MW power was observed to be 1 kW with a total electrical power consumption of around 5 kWh. Also, total time needed to prepare the glass is around 2 hours. Thus, MW heating could be an alternate efficient tool in producing low OH content glass
Probing aqueous electrolytes with Fourier Spectrum Pulse-Echo technique
No full textThe nature of variations of ultrasonic wave velocity(v) and attenuation constant(a) with the concentration(c) in aqueous solutions of NaCl, KCl and CsCl are investigated at room temperature(25 degrees C) at 1 MHz and 2 MHz wave frequency. Fourier Spectrum Pulse-Echo (FSPE) technique is used to achieve better accuracy in measurement, particularly for a measurement. Abrupt changes in the values of v and a are noticed at particular solution concentrations for NaCl and KCl but, for CsCl, almost smooth variation in v is observed over the whole concentration range both for 1 MHz and 2 MHz. The nature of variation in v and a in these solutions are analyzed in view of other spectroscopic studies. The well-known Jones-Dole equation that explains the viscosity (eta) variation in many electrolyte solutions, offers satisfactory fits to the experimental velocity variation with parameter values characteristics of the sample. (C) 2019 Elsevier B.V. All rights reserved
In vitro cytotoxicity and ion release of multi-ion doped hydroxyapatite
No full textMulti-ion doped hydroxyapatite (HA) is gaining more attention due to its potential in enhancing multifunctional biological, structural, and mechanical properties for orthopedic and dental applications. In this study, HA doped with multiple cations (Sr+2, Zn+2, Ag+) and anion (F-) was prepared by high-energy ball milling. Sintered HA samples were evaluated for their in vitro cytocompatibility, ion release, and bioactivity. The composition of multi-ion doped HA was optimized using Design of experiments (DOE). Our analysis showed that the contribution of each dopant on cell proliferation changes with culture duration. During first 3 days, F- exhibited strongest influence and during 7-day proliferation Sr+2 and Ag+ had maximum influence. Binary ion doping found to have strong interaction on cell proliferation, while the ternary and quaternary ion doping did not show any interactions. In general, up to twofold increase in the cell viability was achieved with ternary and quaternary ion doping consisting of Sr+2, Zn+2, Ag+ and F-. Although large number of compositions has been identified to exhibit better in vitro cell viability than pure HA, for enhanced long-term cytocompatibility the compositions of multi-ion doped HA would be 2.5Sr-2.5Zn-2.5Ag, 2.5Sr-5Zn-2.5Ag, and 5Sr-2.5Zn-2.5Ag with up to 5 wt% F
White light-emitting Dy3+-doped transparent chloroborosilicate glass: synthesis and optical properties
Get PDFDy3+-doped chloroborosilicate glasses with the composition 35.7SiO(2)-25.5B(2)O(3)-17BaO-3.4K(2)O-3.4Al(2)O(3)-15BaCl(2) (mol%) were prepared using melt quenching technique. The glass transition temperature (T-g) was similar to 610 degrees C. In UV-vis-NIR absorption spectra, characteristic absorption bands of Dy3+ appeared at 322, 347, 364, 388, 795 and 880nm due to spectral transitions from the H-6(15/2) level to various higher levels of Dy3+ ion. The excitation spectrum was recorded at within 200-550nm by monitoring emissions at 576nm. The excitation bands at 392, 428, 453 and 472nm were attributed to the (H15/2I13/2)-H-6-I-4, (4)G(11/2), I-4(15/2) and F-4(9/2) transitions, respectively. Prominent emission bands were observed at wavelengths of 484, 576, 664 and 754nm when excited at 447nm. The bands correspond to the transitions (F9/2H15/2)-F-4-H-6, (F9/2H13/2)-F-4-H-6, (F9/2H11/2)-F-4-H-6 and (F9/2H9/2)-F-4-H-6 F-6(11/2), respectively. The emitted light from all the samples was found to be white. Their color coordinates lie within the white range. The sample containing 0.5wt% Dy2O3 emitted white light with the color coordinates x=0.351, y=0.335, which are the very closest to pure white light and whose color temperature of 4716K is similar to daylight. Such white light-emitting transparent glasses promise to be enormously useful for various photonic applications