IR@CGCRI - Central Glass and Ceramic Research Institute (CSIR)
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Structural and optical properties of silicon oxycarbide thin films using silane based precursors via sol-gel process
No full textSilicon oxycarbide (SiCxOy) is a candidate material for white luminescence. This work investigates the formation of SiCxOy thin film coating by sol-gel route using various silanes namely, methyltrimethoxy silane (MTMS) with or without using tetraethyl orthosilicate, vinyltrimethoxysilane and polydimethyl siloxane, followed by calcination at 1000 °C/1 h under Ar atmosphere. The structural and optical properties of the developed films were studied by X-ray diffractomete (XRD), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), field emission scanning electron microscopy (FESEM), electron paramagnetic resonance (EPR) spectroscopy and Photoluminescence (PL). XRD plot shows amorphous nature of silicon oxycarbide (SiCxOy) while FTIR reveals Si-C band at 795 cm−1 and Si-O-Si band at 1085 cm−1 confirming the presence of SiCxOy. XPS analysis of MTMS derived coating revealed stoichiometry of SiC0.3O2.25 which is comparable to SiCxOy (0.2<x<0.6, y<1.6). EPR spectra analysis shows presence of Si-dangling bond which could be the probable cause of luminescence center in SiCxOy as observed from PL study. FESEM shows uniform coating of thickness ∼200 nm. PL spectra shows blue and green emission peaks at ∼ 403–452 and ∼ 483–560 nm, respectively
Beam quality evolution in large-mode-area specially doped laser fiber through bend-induced effective refractive index change
No full textThe effect of bending in a specially doped large-mode-area (LMA) gain fiber on the beam quality of the laser and amplifier has been studied through simulation and experimentation. The effect on the overlap between the fundamental mode (FM) and the doping region due to bend-induced refractive index change was studied theoretically by varying the bend radius. Bend radius of the gain fiber in the range of 5-8 cm was used to study the evolution of beam quality at the amplified output. The numerical simulation of the overlap between the FM and the dopant distribution in the core of the gain fiber for different bending radii is well matched to the experimentally measured beam quality of the amplified output for the respective bending of the gain fiber. The master oscillator (having M 2 = 1.1) was successfully amplified to 35 W maintaining the near-diffraction-limited beam quality (M 2 = 1.05) using a confined doped LMA gain fiber with a bend radius of 8 cm. However, the use of a uniform doped LMA gain fiber with similar bend configuration degrades the beam quality (M 2 = 1.37) at the amplified output power of 31.3 W
Role of Surface Chemistry of Ta Metal Foil on the Growth of GaN Nanorods by Laser Molecular Beam Epitaxy and Their Field Emission Characteristics
No full textThis study investigates the influence of surface nitridation of Ta metal foil substrates on the growth of GaN nanorods using the laser molecular beam epitaxy (LMBE) technique and the field emission characteristics of the grown GaN nanorod ensemble. Surface morphology examinations underscore the pivotal role of Ta foil nitridation in shaping the dimensions and densities of GaN nanorods. Bare Ta foil fosters the formation of high-density, vertically self-aligned GaN nanorods at a growth temperature of 700 degree celsius. Furthermore, the density of these nanorods is directly related to the duration of Ta foil nitridation, with increased duration leading to a reduced nanorod density. X-ray Photoelectron Spectroscopy (XPS) studies reveal that the transition of the Ta foil surface from tantalum oxide to tantalum nitride during nitridation emerges as a crucial factor influencing GaN nanorod growth. Photoluminescence (PL) spectroscopy at ambient temperature reveals a strong near-band-edge (NBE) emission peak with negligible defect-related peaks, displaying the high optical quality of the GaN nanorods. The highly dense vertically aligned GaN nanorod ensemble growth without Ta prenitridation exhibits the most favorable field emission performance, featuring a turn-on field of 2.1 V/mu m, a field enhancement factor of 2480, and a stable long-term operation at the emission current density of 2.26 mA/cm2. This study advances the understanding of the role of the surface chemistry of metal foil in determining GaN nanorod growth and opens up exciting possibilities for tailoring advanced optoelectronic devices for specific application requirements
Pulsed Fiber Lasers Employing Diverse Saturable Absorbers and Chirped Pulse Amplification Technique
No full textEngineering the Meta-Phosphate Bao–Al2O3–P2O5 Glass Network for High Average Power (HAP) Laser Applications: Systematic Composition Modifications and SiO2 Integration
No full textThe metaphosphate glasses are the preferred gain media for high-power solid-state laser applications. In the context of solid-state glass lasers, the main challenge to attain high average power (HAP) is to govern excessive thermal loading during operation. This work focuses on addressing thermal loading issues through improving thermal and mechanical properties of the meta-phosphate BaO–Al2O3–P2O5 laser glass system by engineering its molecular structure through systematic composition modifications with SiO2 incorporation. FTIR, Raman and 27Al MAS-NMR spectroscopy indicate stronger P–O–P bridges with decreasing glass basicity and increasing [AlO4] formations beyond 12.5 mol% Al2O3. The O/P ratio increases from 3.05 to 3.43 with up to 20 mol% SiO2 in Series-A and from 3.13 to 3.49 with up to 15 mol% SiO2 in Series-B, altering the Al coordination number from 6 to 4 to maintain the glass network charge balance. Increased [AlO4] formation raises Young's modulus from 61 GPa to 73 GPa and decreases Poisson's ratio from 0.30 to 0.24. These changes enhance fracture toughness and reduce CTE. Further, SiO2 inclusion enhances thermal conductivity by increasing glass network compactness and rigidity. These modifications highlight the improved thermo-mechanical properties of the SiO2-modified Series-B glasses. Yb3+ emission cross-section rises from 0.495 × 10−20 cm2 in ABSP-A1 glass to 0.502 × 10−20 cm2 in ABSP-B1 with increased [AlO4] formation. More AlPO4-like units in ABSP-B1 increase average glass phonon energy, reducing Yb3+ fluorescence lifetime from 1062 μs to 945 μs, whereas SiO2 addition boosts Yb3+ fluorescence lifetime again. Lower OH− content further extends Yb3+ fluorescence lifetime in Series-B glasses with higher SiO2 content. This study underscores the intricate relationship between glass molecular structure and thermal, mechanical, and spectroscopic properties, advancing high-power silico-phosphate laser glass development
Conjugated Polymer-Supported Doped Bi2WO6 S-Scheme Heterojunction for Proficient Water Splitting via Dual Regulation of Band Gap Engineering and Improved Charge Separation
No full textDesigning potent photocatalysts for water splitting is one of the foremost challenges in operative solar energy harvesting, and particularly, exploring Bi2WO6-based photocatalysts remains unresolved due to its intrinsic drawbacks of fast charge recombination, poor conductivity, and inadequate catalytic efficiency. Herein, we present a strategy to tune the band gap of molybdenum-doped Bi2WO6 (Mo-Bi2WO6) by an amalgamation of conducting polymer nanofibers for efficient hydrogen generation via photocatalytic water splitting. The heterostructures mimic natural photosynthetic systems via S-scheme charge transfer, utilizing the conducting polymer component to harvest photons for reduction reaction and the transition metal part to hasten catalytic activities by facile charge transfer, which drastically lowers the transport resistance, as reflected in impedance spectra. The optimal content of 2 wt % Mo-BiWO6 as a cocatalyst in the heterostructures reaches a remarkable H2 production rate of 131 mmol g–1 h–1 with an 18% higher apparent quantum efficiency than pure PPy. Moreover, the heterostructure displays 200- fold higher photocurrent density with fortuitous photostability. The presence of PPy efficiently suppresses charge recombination of Mo-Bi2WO6 and improves interfacial charge transfer at the heterostructure. The dominant factor for higher photocatalytic activity is proposed based on a femtosecond transient absorption spectra study supported further by time-resolved photoluminescence spectra and valence band X-ray photoelectron spectroscopy. This work provides a facile approach to developing high-performance, noble-metal-free visible light-driven photocatalysts for efficient solar-fuel production
Synthesis and fabrication of ultra-lowexpansion glass-ceramic in ternary Li2O-Al2O3-SiO2system utilizing industrial waste
No full textThe rapid rise of industrial solid wastes creates a major concern for environmental pollution. Thus, recycling of the wastes towards value added product development has become a real challenge [1].In this work, a low thermal expansion glass-ceramic (GC) material based on ternary Li2O-Al2O3-SiO2 (LAS)system has been prepared using industrial waste (Blast furnace slag) and low-cost aluminosilicate minerals (China clay and pyrophyllite)whileTiO2has beenused as nucleating agentin the glass composition.The raw material after mixing is melted at relatively lower temperature (~1450oC) compared to pure LAS system by melt-quenching route. A part of the precursor powder for pristine glass has also been prepared by sol-gel processing utilizing Li2CO3 and Al (NO3)3.9H2O to obtain better homogeneity in the glass composition vis-à-vis glass-ceramics at lower melting temperature [2].The cast glass is annealed followed by ceramization. Initially, the thermal properties of material have been characterized to optimize the nucleation and crystallization temperatures for converting glass to glass-ceramics. It has been observed that nucleation and crystallization schedule play a crucial role to achieve the desired properties in LAS system. The XRD study reveals the presence of lithium aluminosilicate (β-eucryptite-β-spodumene solid solution) as major crystalline phase along with a minor crystal phase, calcium aluminosilicate. The glass heat-treated at 730°C/8h shows ultra-low CTE value of 8×10-7/0C in low temperature range of 0-2000C whereas 19×10-7/0C (0-5000C). The increase in soaking time of crystallization to more than 8h results in an increase in CTE value from 19×10-7/0C to 26×10-7/0C and 29×10-7/0C at 10 and 12h respectively. Formation of β-spodumene crystal phase become predominant along with calcium aluminosilicate as heat-treatment time is increased beyond 8h; thus, resulting in higher thermal expansion coefficient of the material. The crystallite size for heat-treated sample also increased from 54 nm to 62 and 72 nm as soaking time is increased resulting in the formation of bigger size crystals. The present work demonstrates an effective approach towards efficient utilization of waste for the development of low CTE glass-ceramics for cook-top plate of LPG gas ovenand optical applications[3]
Rapid adsorption and simultaneous photocatalytic effect of Ru doped flower like antimony tungstate
No full textRuthenium (Ru) doped antimony tungstate microflowers, prepared through hydrothermal process, have been investigated for simultaneous adsorption and photocatalysis. The pattern of evolution of microflower structures, however, can be tailored by the synthesis period. This change is observed from the field effect scanning electron microscope and transmission electron microscope images. A possible mechanism behind this morphological change has been developed. An argument based on the zeta potential may be responsible for this distinct morphology due to the strong electrostatic interactions. The variation of a particular x-ray diffraction peak corresponding to the plane {012} with variation of Ru doping percentage shows the decrease in crystallinity along the perpendicular direction to this plane. Besides, the optimum Ru doping percentage is evaluated on the basis of photocatalytic efficiency towards methylene blue (MB) degradation under visible light. The highest dye removal efficiency is observed for 2% Ru doped Sb2WO6 (SWO) adsorbing 97% of the MB dye followed by photocatalytic degradation of almost 64% of the remaining dye in 80 min. Furthermore, using different dyes, it is concluded that Ru-SWO showcases high adsorption toward the cationic dyes while it neither adsorbs the anionic dye nor displays photocatalytic degradation
Design of a polymer-based cladding mode stripper with a distributed temperature profile
No full textAn optimized polymer -based fiber cladding mode stripper (CMS) is presented experimentally. A unique partial fiber stripping method is introduced in CMS fabrication to enable distributed power extraction and temperature along the length of the CMS. The designed CMS based on a 400 mu m double -clad fiber (DCF) extracts 300 W of inner cladding power, with an attenuation coefficient of 18.8 dB along with a temperature gradient of 0.17degree celsius/watt. The fabricated CMS is used to develop an all -fiber 150 W thulium fiber laser at 1.94 mu m. (c) 2024 Optica Publishing Grou
Nanostructured NiO for Catalytic Oxidation of CO: Microstructural and Anionic Effects of the Precursors
No full textTransition metal oxides are suitable catalysts, capable of converting toxic carbon monoxide to carbon dioxide. Morphological and textural behaviors of the catalyst influence the catalytic conversion efficiencies. The present work highlights the role of anions of the nickel-based precursor salts in hydrothermally synthesized (180 °C/24 h) nickel oxide catalysts toward CO conversion concerning their surface area, pore dimensions, and microstructural characteristics. Precursors having different anions used in NiO synthesis have distinct effects in shaping the physicochemical features of the synthesized catalysts governing the catalytic conversion process which were investigated in this study. The nitrate and acetate-based NiO with flower-like morphology exhibit a comparatively low surface area (BET) and larger pore volume and diameter than the sulfate-based precursor. Catalytic CO oxidation study reveals that T100 i.e., the temperature to reach 100 % volume conversion of CO to CO2 was 249, 209, and 274 °C for nitrate, acetate, and sulfate-based precursors, respectively. It was evident that the higher pore volume is a critical parameter that facilitates and governs efficient catalytic CO oxidation at comparatively low temperatures. The evolution of the pore properties and their reciprocity with the catalytic activity has been expounded in this study