IR@CGCRI - Central Glass and Ceramic Research Institute (CSIR)
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Investigation of Densification Pathway of Magnesia Refractory through Non-Isothermal Kinetics
No full textAbstract: Brucite-derived calcined magnesia, which was synthesized from kimberlite tailings was studied for its sintering kinetics. The non-isothermal sintering kinetics of the calcined MgO were studied using dilatometric data obtained under controlled heating conditions with a Thermo-Mechanical Analyzer. Both model-free and model-based analyses were conducted to investigate the sintering behaviour. Iso-conversional methods such as Ozawa–Flynn–Wall (OFW) and Friedman approaches indicated an apparent activation energy (Ea) in the range of 500–630 kJ·mol⁻¹ up to 80% conversion. Beyond this point, Ea increased significantly to approximately 1000 kJ·mol⁻¹, suggesting a shift in the dominant sintering mechanism.
Multiple linear regression analysis revealed that a single-step, n-dimensional Avrami–Erofeev model most accurately described the sintering pathway (Ea=686 kJ·mol⁻¹, n= 0.19 and log A= 21.09 s-1) with a high coefficient of regression (R² = 0.997315). Additionally, isothermal sintering was also performed in the temperature range of 1500 –1700 °C under static conditions. XRD analysis confirmed the exclusive presence of the periclase (MgO) phase post-sintering, while energy-dispersive X-ray spectroscopy (EDS) detected trace amounts of calcium at the grain boundaries. This study provides a comprehensive theoretical foundation and introduces a novel perspective for understanding the sintering behaviour of magnesia
Bi−S Bond Mediated Direct Z-Scheme BiOCl/Cu2SnS3 Heterostructure for Efficient Photocatalytic Hydrogen Generation
No full textThe advancement of photocatalytic technology for solar-driven hydrogen (H2) production remains hindered by several challenges in developing efficient photocatalysts. A key issue is the rapid recombination of charge carriers, which significantly limits the light-harvesting ability of materials like BiOCl and Cu2SnS3 quantum dots (CTS QDs), despite the faster charge mobility and quantum confinement effect, respectively. Herein, a BiOCl/CTS (BCTS) heterostructure was synthesized by loading CTS QDs onto BiOCl 2D nanosheets (NSs), that demonstrated excellent photocatalytic activity under visible light irradiation. The improved hydrogen generation rate (HGR) was primarily due to an interfacial Bi−S bond formation, which facilitates the creation of direct Z-scheme heterojunction and an internal electric field at the interface, promoting efficient charge transfer between BiOCl and CTS. Moreover, due to the amalgamation of Bi−S bond formation and interfacial electric field, the optimized BCTS-5% heterostructure exhibited a high HGR of 8.27 mmol g−1 h−1, and an apparent quantum yield (AQY) of 61 %, ~4 times higher than pristine BiOCl. First-principle density functional theory (DFT) calculations further revealed the presence of a Bi−S bond with a bond length of ~2.85 Å and a minimal work function of 2.37 eV for the heterostructure, both of which are critical for enhancing H2 generation efficiency
Study on the Influence of SiO2 on Thermal, Mechanical and Thermo-optical Properties of Rare Earth Doped Alminophosphate Glass for High Average Power (HAP) Laser Application
No full textThis PhD thesis explores advancements in glass host materials for high-average-power (HAP)
laser applications and environmentally sustainable commercial glass production. In Part A, the
thermal, mechanical, thermo-optical and spectroscopic properties of silico-phosphate glasses
are optimized through systematic compositional modifications. The incorporation of SiO₂ into
BaO-Al₂O₃-P₂O₅ (Al2O3 ≥12.5 mol%) glasses enhances thermal conductivity, reduces the
coefficient of thermal expansion, and increases fracture toughness while maintaining structural
stability, despite a reduction in Yb³⁺ fluorescence lifetime. Further, modifying MgO-BaOAl₂O₃-P₂O₅-SiO₂ glasses with optimized oxygen-to-phosphorus (O/P) ratios and SiO2 content
improves rigidity, fracture toughness, thermal expansion coefficient and hydration resistance,
balancing gains in thermo-mechanical and thermo-optical properties against minor reductions
in laser gain coefficients. Additionally, Er³⁺ and Yb³⁺/Er³⁺ co-doped silico-phosphate glasses
exhibit efficient energy transfer mechanisms, stable structural integrity, and promising
fluorescence lifetimes, particularly in compositions such as ABSP-M3(YbEr15), reinforcing
their suitability for HAP applications. In Part B, the thesis addresses sustainability in industrial
glass manufacturing by using boron-containing carbon-free minerals, such as colemanite and
borax penta-hydrate, as alternative sources for CaO and Na₂O in soda lime silicate (SLS) glass.
This approach significantly lowers the melting temperature by up to 500 °C, reducing energy
consumption and CO₂ emissions while maintaining desirable glass properties, such as enhanced
Vickers’ micro-hardness and lower thermal expansion coefficients. Together, the findings
contribute to the development of high-performance laser glasses and sustainable, energyefficient glass production, addressing both technological and environmental challenges
Immobilized Gold Nanoparticles on a Glass-Based Scaffold for Direct Solar-Driven H2 from Water Vapor
No full textSolar-driven green hydrogen (H2) production through photocatalytic water splitting is a promising solution to combat climate change. A key challenge lies in developing photocatalyst materials capable of efficiently splitting water vapor under practical conditions. In this study, we present a photocatalytic system based on gold nanoparticles immobilized on a glass-based porous scaffold through reactive metal support interactions. This structure exhibits a high solar-to-hydrogen (STH) conversion efficiency of 2.2% under simulated solar light. Long-term cycling tests demonstrate stable H2 evolution, with observed declines in efficiency caused by surface hydroxyl and carboxyl group formation, although it is effectively restored through plasma treatment. These findings provide valuable insights into the design of robust and efficient photocatalytic materials, advancing the potential path for scalable commercial applications
Synergic Effect of Atomic-Scale Interface Engineering and Built-in Electric Field at S-Scheme Bi2WO6/ZnIn2S4 Heterojunctions for Photocatalytic Hydrogen Evolution
No full textThe photocatalytic hydrogen evolution reaction (HER) is a promising avenue for sustainable energy conversion, but its efficiency is hindered by rapid charge carrier recombination. In this study, we rationally designed a novel S-scheme heterojunction through the in-situ growth of ZnIn2S4 (ZIS) nanoflakes on assembled Bi2WO6 (BWO) nanorods, forming Bi2WO6/ZnIn2S4 (BWIS) heterostructure with a nanoflake-assembled morphology.Upon visible-light irradiation, the optimized BWIS system exhibited a remarkable photocatalytic HER rate of 392 μmol. g1. h1, representing an enhancement of 24.5-fold compared to pristine BWO, with an Apparent Quantum Yield of 53% at 420 nm. Systematic experimental analyses revealed that well-aligned band structures and work function difference between BWO and ZIS generate a built-in electric field, facilitating directional S-scheme charge transfer from BWO to ZIS. In concert with the optimized interface, this internal field significantly suppresses charge carrier recombination and enhances charge separation and transport kinetics. The formation of interfacial Bi–S bonds facilitate efficient charge transfer pathways, while the presence of metallic Bi (Bi⁰) is an effective electron reservoir, further elevating charge mobility. This work underscores the pivotal role of atomic-scale interface engineering, internal electric field optimization, and defect modulation in advancing S-scheme charge transfer mechanisms, ultimately culminating in superior photocatalytic hydrogen production performance
Ceramic Supported Catalytic Membrane Based Fermentative Reactor Process for Biohydrogen Production from Industrial Wastewater
No full textBiohydrogen production from carbohydrate rich organic wastes by fermentation route emerges as a sustainable option for renewable energy generation. Application of membrane technology in fermentation process can be beneficial as the membrane facilitate in removing the H2 generation inhibitors from the fermentation reaction, such as volatile fatty acids (VFA) and alcohols and improves the process yield. In the present study a novel nickel oxide (NiO) based ceramic catalytic membrane is developed on clay-alumina tubular support withan intermediate bentonite clay coating for application in membrane bioreactor (MBR) process. The prepared membrane showed highly hydrophilic surface involving static water contact angle of 320. A reduction in the clean water permeability (CWP) ofmembrane was observed due to the surface coating, 25 Lm-2h-1bar-1in comparison with that of the pristine support,105 Lm-2h-1bar-1.From FESEM and EDX analysis, impregnation of NiO,~28-29 (wt%) was evident on the membrane surface.Further, VFA rejection efficiency of the catalytic membrane was observed high with respect to butyric acid (50%) and acetic acid (60%) compared to thepristine support (30–40%).
The membranes were used ina batch mode cylindrical bioreactor (7 L)made with stainless steelfor the dark fermentation processutilizing simulated molasses wastewater having initial COD of 8000 mg/L to produce biohydrogen under anaerobic condition in the presence of Clostridium sp. with controlled pH (6-7), temperature 35-400C and stirring conditions (300 rpm).The performance efficiency of fermentation process was compared in three types of system: i) without membrane; ii) with pristine supports and iii) with catalytic membranes.After 120 h of fermentation, biohydrogen generation was recorded as 0.15, 0.35 and 0.48 mol H2/mol of carbohydrate in the systems (i), (ii) and (iii) respectively. Withappropriate optimizationof the wastewater composition in terms of carbohydrate content, use of microorganism consortium such as Clostridium. sp. and Enterobactor. sp. and employing a novel bi-metallic (Ni-Fe) based catalytic membrane can enhance the biohydrogen yield towards establishing a sustainable waste-to-energy production pathway
Discovery of Magnetic Field Line Dependent Anisotropic Chemiresistive Response in Magnetite: A New Piece to the Puzzle Of Magnetoreception
No full textChemiresistive materials, which alter their electrical resistance in response to interactions with surrounding chemicals, are valued for their robustness, rapid detection ability and high sensitivity. Recent research has revealed that the sensing performance of these materials can be enhanced by applying an external magnetic field. In this study, we report a novel finding in the chemiresistive behaviour of magnetite (Fe3O4), where its response has been found to be modulated in an anisotropic manner when exposed to an external magnetic field, analogous to Earth's magnetic field. Remarkably, substantial variations have been observed in response to analytes naturally present in the atmosphere. A remarkable increase in response was observed upon applying a 0.05 mT magnetic field, resulting in a more than 26-fold enhancement in sensitivity to relative humidity (98%), as well as a greater than 10-fold improvement in response to CO2 and a 25-fold increase in response to NO2. This chemiresistive response exhibits a strong anisotropic dependence on the strength, direction and inclination of the magnetic field, suggesting that magnetite's electrical resistance dynamically adapts to both magnetic and chemical environmental changes. The observed behaviour under an Earth-like magnetic field closely mirrors the magnetoreception seen in biological species that rely on magnetite for navigation. This finding may provide new insights into the mechanisms behind magnetite-based magnetoreception observed in various biological species
Impact of Gaseous Environment on the Properties of Refractory Materials
No full textGaseous environment affects the performance of oxide-based refractories. The impact of gases is mainly focused on the stability of the refractory materials under different partial pressures of the constituent gases. Research has primarily focused on the corrosion resistance of silica-aluminium containing refractories. As a result, there is an increasing concern about the interaction of refractories with the gases. Gases can affect refractory materials through chemical reactions, thermal stress, and corrosion, making it crucial to understand these interactions. Identifying corrosion mechanisms is essential for improving the durability and performance of refractory linings in gaseous-rich, high-temperature environments. Although significant progress has been made, ongoing research continues to explore the gaseous interaction with the refractory materials to achieve optimal solutions for the industry. Our study investigates refractory materials such as alumina, magnesia, stoichiometric spinel, alumina-rich spinel, and mullite in nitrogen and hydrogen atmospheres over a 24-h period with controlled gas flow rates. After firing, the refractory bar samples were characterized in terms of apparent porosity and bulk density. Thermomechanical properties, including the modulus of elasticity and modulus of rupture, were measured both before and after exposure to the gas atmosphere to assess the change in properties in the refractory materials. XRD analysis was performed to confirm the presence of spinel and mullite phases before the interaction with gases
Development of A Hydrophobic Multilayer Membrane for Efficient Removal of Polycyclic Aromatic Hydrocarbons (PAHs) in Coastal Groundwater
No full textThe increasing contamination of coastal groundwater by polycyclic aromatic hydrocarbons (PAHs), especially in sensitive areas like the Sundarbans, calls for robust remediation strategies. This study introduces a trilayered superhydrophobic composite membrane built on a mullite–α-alumina tubular support, consisting of a γ-δ alumina base, kaolin clay interlayer, and a silane-modified top layer. Optimized through controlled precursor concentrations, the membrane displayed hierarchical porosity, superhydrophobicity (contact angle ~155°), and thermal and chemical stability. Characterization confirmed the presence of microporous and mesoporous layers, essential for size-exclusion-driven separation.
The membrane's performance was tested on real Sundarbans groundwater samples containing various PAHs, cations, and anions. Gas chromatography identified 11 PAH components per sample, with total concentrations of 6.96 µg/mL and 11.24 µg/mL. The membrane achieved 97.55% PAH removal from Sample A and 58.76% from Sample B. Rejection modeling using Spiegler-Kedem–Film Theory and Extended Nernst–Planck models showed that ion concentration and type significantly influence separation efficiency because of polarization effects. While divalent and multivalent ions were effectively removed (>80%), monovalent ions like Na⁺ and Cl⁻ exhibited lower rejection rates.
This study presents a scalable membrane-based approach for PAH cleanup, harnessing inorganic-organic synergy and hierarchical structure to overcome the limits of traditional technologies
Double Heterojunction Photocatalysts: Strategic Fabrication and Mechanistic Insights Towards Sustainable Fuel Production
No full textExcessive energy crisis has triggered the transformation of solar energy into chemical energy via photocatalysis to establish a sustainable and carbon-neutral society. In this regard, the fabrication of visible-light-active photocatalysts with favourable band edge positions is preferred for achieving maximum solar energy conversion efficiency. However, a single semiconductor suffers from several disadvantages, such as rapid electron–hole recombination, inefficient electron–hole separation and sluggish charge migration dynamics. To improve photocatalytic performance, constructing heterostructures using two semiconductors has been considered an effective strategy. Nonetheless, these binary heterostructures also present several challenges, which can be addressed by combining three semiconductors to form double heterojunctions. The formation of double heterojunctions enhances visible light absorption, increases charge carrier concentration and facilitates superior charge separation owing to the presence of in-built electric fields, thereby ameliorating the photocatalytic efficacy of these heterostructures compared to binary ones. This review article provides a deep insight into the charge transfer mechanisms that occur in different types of double heterojunctions. Moreover, it highlights the applications of these heterostructures in various fields of photocatalysis, such as water splitting, CO2 reduction, N2 fixation and pollutant degradation