IR@CGCRI - Central Glass and Ceramic Research Institute (CSIR)
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Enhanced solar hydrogen generation using Cu-Cu2O integrated polypyrrole nanofibers as heterostructured catalysts
No full textNanostructured conducting polymeric materials are beneficial for electron conduction and mass transport, showing prominent photocatalytic performance for dye degradation under visible light. Herein, we report a simple colloidal route for large-scale synthesis of copper and copper oxides (Cu2O) modified polypyrrole nanofibers (PPy) heterostructures, which demonstrate significantly high performance towards H2 generation under visible light. The presence of Cu nanoparticles (NPs) of 50 nm and cubic shaped Cu2O nanoparticles of size ~200 nm endows the heterostructures with a large specific surface area as well as good dispersion of nanoparticles on PPy nanofibers allows the migration of electron during catalysis. The UV-Visible diffuse reflectance spectra displayed strong absorption in the visible region, which favors the photocatalytic performance. Under visible light irradiation, Cu2O/PPy exhibits excellent H2 production with the rate of 67 mmol h−1 which is ~12 times higher than PPy (5.7 mmol h–1). The optimal catalyst Cu/PPy-0.05 exhibits the high hydrogen generation rate of ~ 50 mmol h–1, which reaches 8.6 times of pure PPy. The Mott–Schottky plot revealed that photo generated charge carrier concentration has been increased considerably for Cu2O/PPy (2.791013cm3) compare to pure PPy (1.431011 cm3). The high-performance Cu2O/PPy catalyst provides a fervent alternative to noble metal-based catalysts for the hydrogen generation in practical applications
Synthetic and structural investigation of ZnO nano-rods, hydrothermally grown over Au coated optical fiber for evanescent field-based detection of aqueous ammonia
Get PDFWe present the fabrication of modified clad optical fiber coated with ZnO nanorod over Au thin film to be served as ammonia gas sensor. The deposited material ZnO synthesized by hydrothermal process and modified clad fiber is coated by Autoclave technique. The as-synthesized materials are characterized by XRD, XPS, FTIR, Raman spectra and its hexagonal nanorods morphology was checked by FESEM. The ZnO coated over Au thin film fiber is found to be a good candidate towards ammonia sensing. The developed sesnor exihibted sensitivity (%) ~ 0.638 of ammonia gas at room temperature
Gain-flattened hybrid EDFA operating in C plus L band with parallel pumping distribution technique
No full textA novel C + L band hybrid erbium-doped fibre amplifier (EDFA) using a two-stage configuration was proposed and demonstrated experimentally. The amplifier is composed of a 0.5-m long hafnium bismuth erbium co-doped fibre (EDF) to provide gain within the C-band and a 4-m long zirconia-based EDF to provide gain within the L-band. The proposed amplifier was examined based on the multi-wavelength input source. A parallel pumping distribution technique was used to mitigate the amplifier complexity. The C + L band amplifier achieved a gain flattening of over 55 nm bandwidth for the three levels of the input powers. A gain-flattening of roughly 10.9, 15.5, and 19.2 dB were obtained, respectively, for the input signal powers of -5, -10, and -15 dBm. An average noise figure of 6.4, 5.4, and 4.7 dB was achieved, respectively, for the input signal powers of -5, -10, and -15 dBm
Significantly suppressed leakage current and reduced band gap of BiFeO3 through Ba-Zr Co-Substitution: Structural, optical, electrical and magnetic study
No full textBismuth Ferrite (BFO), Ba substituted BFO (BBFO) and Ba-Zr co-substituted BFO (BBFZO) nanoparticles have been synthesized via citrate-gel route. The common problem of BFO i.e; compositional instability, low magnetization and high leakage current was resolved by this doping technique. Remanent magnetization and remanent polarization improved significantly for BBFZO sample compared to that of BFO. Structural, optical and improved dielectric properties were also investigated. Structural study confirmed the enhanced structural distortion in BFO due to doping of Ba and Ba-Zr ions. The calculated energy band gap has been reduced to 1.52 eV for BBFZO nanoparticles from a value of 2.55 eV for BFO. Leakage current was suppressed by almost seven orders of magnitude for Ba-Zr co-substituted bulk BFO compared to that of undoped BFO. Morphological study of bulk samples has shown gradual reduction in grain size upon Ba doping and Ba-Zr co-doping in BFO, respectively
Composition-structure-property effects of antimony in soda-lime-silica glasses
No full textFloat glass-type SiO2-Na2O-CaO glasses with 0 - 10 mol% Sb2O3 were melted and their compositional, structural, thermal and optical properties characterised. All glasses were X-ray amorphous and increasing Sb2O3 content progressively decreased glass transition temperature (T-g) and dilatometric softening point (T-d), despite increases in Al2O3 content from greater crucible corrosion. Sb-121 Mossbauer spectroscopy confirmed that Sb was predominantly incorporated as Sb3+ (Sb3+/Sigma Sb similar to 0.9) and Raman spectroscopy showed that Sb substantially decreased average (Si, Al)-O Q(n) speciation. Both techniques confirmed that Sb3+ ions were incorporated in trigonal pyramidal :SbO3] polyhedra. XRF and Raman spectroscopies confirmed that SO3 content decreased with increasing Sb2O3 content. TGA analysis showed, as a linear function of Sb2O3 content, mass gain commencing at 700 degrees C, reaching a maximum at 1175 degrees C, then mass loss above 1175 degrees C, consistent with oxidation (Sb3+ -> Sb5+) then reduction (Sb5+ -> Sb3+). The TGA samples were shown to have attained or approached Sb redox equilibrium during measurement. Optical absorption spectroscopy (UV-Vis-nIR) showed red-shifts of the UV absorption edge with increasing Sb2O3 content, consistent with increasing intensity of far-UV absorption bands from Sb3+ and Sb5+ s -> p transitions. UV-Vis-nIR fluorescence spectroscopy evidenced a broad luminescence band centred at similar to 25,000 cm(-1), attributed to the P-3(1)-> S-1(0) transition of Sb3+, which is Stokes shifted by similar to 15,000 cm(-1) from the S-1(0)-> P-3(1) absorption at similar to 40,000 cm(-1). The most intense emission occurred at 0.5 mol% Sb2O3, with concentration quenching reducing luminescence intensities at higher Sb2O3 contents. Additions of Sb2O3 to float-type soda-lime-silica glasses could thus enable lower melting energies and/or new solar energy applications
Boron-doped silicon carbide (SiC) thin film on silicon (Si): a novel electrode material for supercapacitor application
No full textIn this work, we report the synthesis of silicon carbide (SiC) thin film on silicon by modified chemical vapour deposition technique using boron-doped liquid polycarbosilane as a precursor. Subsequent microscopic and physical characterizations of this film show the presence of SiC nanocrystal along with boron in the SiC thin film. The electrochemical characterizations of the film shows a highest capacitance of 232F/g at 2.2A/g current density from Galvanostatic charging-discharging method with good cyclic stability upto 2000 cycles. The high capacitance value is attributed to the surface defect states and amorphous carbon which acts as the charge active sites. The result further infers that the (B)SiC/Si is a promising electrode material for high-performance energy storage application
Energy transfer in Tb3+-doped Ba2Y0.67V2O8 phosphors preferential for near white light emission
No full textBa2Y0.67-xTbxV2O8 (x = 0.0-0.3) phosphors were produced by a solid-state methodology. The obtained compounds were isostructural with Ba3V2O8. The UV excited Ba2Y0.67-xTbxV2O8 phosphors exhibited a wide emission band centered at 440 nm realized for the VO4](3) groups, and an intense green emission (545 nm) of Tb3+ ions. The host emission diminished and that of Tb3+ amplified with increasing the Tb3+-dopant up to a certain level of Tb3+ concentration owing to the energy transfer (ET) occurrences. Meanwhile, the coloring parameters navigated from the blue to the bluish-white. The presented strategy of fine-tuning the photoluminescence via the vanadate to Tb3+ ET could deliver potential white light-emitting systems. (C) 2020 Elsevier B.V. All rights reserved
Influence of Soybean Hull Fiber Concentration on the Water Absorption and Mechanical Properties of 3D-Printed Thermoplastic Copolyester/Soybean Hull Fiber Composites
No full textIn this work, fused filament fabrication 3D-printed parts of soybean hull fiber thermoplastic copolyester (TPC) composites with soybean hull fiber concentrations of 0-35 wt.% were tested to understand the influence of mechanical properties and moisture sensitivity on the soybean hull fiber concentration. The composites were analyzed for their microstructures and mechanical properties in as-printed condition and after immersion in deionized water for 168 h. The printed parts with >= 25 wt.% soybean hull fiber were found to have more porosity (9-12%) leading to high rate of water absorption with a maximum weight gain of similar to 8% and up to 4% volumetric swelling. However, in the as-printed condition, these composites exhibited significantly higher elastic modulus of 80 +/- 3 MPa than pure TPC (36 +/- 3 MPa) and their strength improved by 40%. The toughness of the composites decreased below that of pure TPC when the fiber concentration was 35 wt.% due to significant drop in the elongation. The composites with <= 15 wt.% soybean hull fiber showed marginal drop in the mechanical properties due to water absorption. Additionally, the microstructural analysis showed good fiber-matrix interfacial characteristics in as-printed condition, which were damaged due to moisture absorption in addition to defragmentation of fiber bundles. Interestingly, the toughness of TPC-soybean hull fiber composites was immune to water absorption and the deleterious effect of moisture on the mechanical appears to be partly reversible after drying the composites
Influence of Ho2O3 on Optimizing Nanostructured Ln(2)Te(6)O(15) Anti-Glass Phases to Attain Transparent TeO2-Based Glass-Ceramics for Mid-IR Photonic Applications
No full textThe transparent TeO2-based glass-ceramics (GCs) have yet to achieve the breakthrough in photonic technologies, because of poor understanding in optimizing the growth of nanostructured crystalline phases. In the present investigation, the size effect of phase-separation-induced, nanostructured Ln(2)Te(6)O(15)-based (Ln: Gd, Ho) ``anti-glass'' phase in Ho2O3-modified TeO2-based TTLG (in mol%, 80TeO(2)-10TiO(2)-5La(2)O(3)-5Gd(2)O(3)) glass has considered to achieve transparent GCs. Raman study of TTLG glass reveals the presence of TeO3, TeO3 + 1, and TeO4 units with average Te-O coordination number as 3.49. The formation of nanostructured Ln(2)Te(6)O(15) phases in GCs is confirmed by X-ray diffraction (XRD) and transmission electron microscopy (TEM) analysis. Furthermore, TEM analysis confirms that an increase of Ho2O3 concentration has reduced the size of phase-separated domains in nanoscale with superstructure formation to attain transparent GCs. The superiority of this obtained transparent GCs as photonic material for near-IR (NIR) to mid-IR (MIR) range has been established by the realization of enhanced luminescence intensities and bandwidth at approximate to 2900 nm (Ho3+: I-5(6 )-> I-5(7)) and approximate to 2050 nm (Ho3+: I-5(7 )-> I-5(8)). This study offers an opportunity to fabricate the various accessible lanthanide ions-doped and/or co-doped TTLG glass with control over nanostructure, to design a series of GCs which are transparent from visible to MIR range
Reverse Flotation of Natural Magnesite and Process Optimization Using Response Surface Methodology
No full textIndian natural magnesite containing silica and lime as main impurities was beneficiated using reverse froth flotation technique. Pine oil was used as frother, Flotigam EDA as collector and sodium hexametaphosphate as depressant of carbonate group. Operating parameters were optimized using response surface methodology and a quadratic model equation was formulated for the experiment. The effect of different process parameters was studied using Box-Behnken design. Statistical analysis suggested that the model was significant. Moreover, optimum process conditions were predicted after analyzing the experimental data. The beneficiated sample for which the highest silica in froth was achieved was characterized in terms of X-ray diffraction analysis. Further, quantification of the crystalline phases showed that amount of quartz was reduced from 2.3% in raw sample to 1.8% in processed sample