IR@CGCRI - Central Glass and Ceramic Research Institute (CSIR)
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Thermal stability and photoluminescence properties of RE-doped (RE = Ho, Er, Tm) alumina nanoparticles in bulk and fiber-optic silica glass
No full textWe present the thermal stability and the photoluminescence properties of RE-doped (RE = Ho, Er, Tm) alumina nanoparticles in the phase system Al2O3-SiO2 with respect to the chemical composition and the thermal processing conditions applied in the fiber-optic technology. The alumina and silica soot reacted together to form mullite when the Al2O3 concentration was higher than 5 mol. %. We have demonstrated that the solubility limits of RE ions in the mullite nanocrystals are strongly limited. The RE ions preferentially occupy highly disordered positions on the nanoparticle surface or in the amorphous Al3+-enriched shell around the nanoparticles, exhibiting maximal lifetime of approx. 1.2 ms, 10.0 ms and 0.6 ms in the Ho-, Er- and Tm-doped samples. Rapid cooling of the samples with stoichiometric composition 3Al2O3.2SiO2 managed to prepare highly defective mullite nanocrystals with embedded RE ions, exhibiting promising photoluminescence lifetimes of 5.6 ms and 2.4 ms in the case of Ho3+ and Tm3+ ions, respectively. In optical fibers with 5 mol. % Al2O3, the formation of amorphous Al3+-enriched nanoparticles was observed and the photoluminescence lifetime was in a good agreement with corresponding bulk samples. Exploitation of the RE-doped stoichiometric mullite in the fiberoptic technology may be a perspective way to improve the photoluminescence efficiency of active optical fibers for high-power applications
Mica (KMg3AlSi3O10F2) based glass-ceramic composite sealant with thermal stability for SOFC application
No full textIn this work, pre-synthesized fluorophlogopite mica (KMg3AlSi3O10F2) crystalline powder was added into potassium-magnesium boro-alumino-silicate (K2O-MgO-B2O3-Al2O3-SiO2) glass powder to synthesize glass-ceramic composite (GCC) sealant for solid oxide fuel cell (SOFC) application. The basic purpose was to report the influence of KMg3AlSi3O10F2 on microstructure, thermal expansion and volume shrinkage behavior of GCCs in terms of their SOFC sealing ability. The predominant crystalline phase was also identified as fluorophlogopite mica (KMg3AlSi3-O10F2) by X-ray diffraction in the GCCs heat-treated at 900 degrees C (for 2 h) followed by 800 degrees C (for 10 h). Higher thermal expansion (10.65-10.81 x 10(-6)/K at 50-800 degrees C) compatible with SOFC components (metallic electrode/interconnect, ceramic electrolyte) was realized for 5-10 wt % mica containing GCC. However, it was found decreased linearly with adding further KMg3AlSi3O10F2 content (20-40 wt%) in the composites. GCC with 5 wt % of mica was stable under thermal cycling testing and no significant degradation was observed in thermal expansion till 10 cycles. Field emission scanning electron microscopy revealed the spherical shaped nanocrystallites morphology of those GCCs and that was ascribed for their compact bonding with SOFC components. Heating stage microscopy (HSM) ensured the lower softening temperature (752 +/- 7 degrees C) for 5 wt % mica containing GCC which furthermore showed 11-13% volume shrinkage (to ensure the self-healing) in SOFC operating temperature. In a summary, the above factors confirmed the suitability of 5 wt % mica (KMg3AlSi3O10F2) containing K2O-MgO-B2O3-Al2O3-SiO2 system (GCC) for SOFC sealant application. (C) 2020 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved
Energy efficiency in buildings and related assessment tools under Indian perspective
No full textThe Building sector stands only after the Industrial sector as far as energy utilization and related CO2 emission criterions are concerned. Electricity use in buildings is increasing by leaps and bounds due to growing urbanization, climate change-related factors and economic developments. An energy efficient building (EEB) or in a broader sense green building (GB), besides making positive impact on Environment and Public Health, also minimizes operating costs, maximizes productivity by the users and facilitates creation of sustainable community. The potential to reduce energy consumption through energy efficient design of new buildings and retrofits to existing buildings are quite high. The rating tools available in India are utilized to help the decision makers to quantify the energy and water efficiency and other parameters to finally establish the performance of the building with least environment damaging effects, without compromising the intended functional purpose. The Energy Conservation Building Code (ECBC) was introduced by Bureau of Energy Efficiency (BEE), Govt. of India, in 2007, and subsequently revised during 2017, as a step towards promoting energy efficiency in Commercial building sector. Another Code titled Eco-Niwas Samhita (ENS) had been launched by BEE during December 2018, aiming energy efficiency in Residential building sector. The ECBC and EWS both provide design norms for thermal performance requirement by building envelop; lighting system including Day-lighting; HVAC system efficiency; Electrical Distribution system including Renewable energy generation and Water heating and pumping system. Adoption of these stipulations helps in obtaining Green Rating for Integrated Habitat Assessment (GRIHA) by The Energy Resources Institute (TERI) and another rating by Indian Green Building Council. These ratings help in assessing sustainable parameters in Energy Efficient Buildings. In this paper, an attempt has been made to describe briefly about such rating tools with some examples under the Indian context to establish the advantages of energy efficiency and environmental sustainability in building sector
Diffused metal-insulator transition in NdNiO3 film grown on BaTiO3: Likely evidence of electronic Griffiths phase
Get PDFThis paper reports diffused metal-insulator transitions (MITs) in an oxide with disorder that undergoes a Mott transition. The investigation was carried out in the multilayer film NdNiO3/BaTiO3/SrTiO3 (NNO/BTO/STO), where a large mismatch of lattice constants of NNO with those of BTO leads to strain relaxation and creation of quenched disorder in the NNO film. NNO film in the NNO/BTO/STO multilayer structure shows a broad Mott-type MIT at a temperature T-MI = 160 K from a high-temperature bad metallic phase (1/rho DC d rho DC/dT < 0) with dT a high value of resistivity rho DC approximate to 70 m Omega cm at 300 K to a low temperature insulating phase. Using noise spectroscopy and impedance spectroscopy which can probe the dynamics of the coexisting phases near the MIT, it was observed that in addition to the MIT at T-MI = 160 K, there exists a characteristic temperature T-G %:Z, 230 K well above the T-MI, where large low-frequency correlated fluctuations appear, signifying the appearance of a phase with slow dynamics. T-G signals the onset of a temperature region T-MI < T < T-G with coexisting phases that have been corroborated by the impedance spectroscopy and AC conductivity measurements. It is suggested that the temperature T-G may signify the onset of an electronic Griffiths phase that has been theoretically proposed for Mott transitions with disorder
Glass for Diamond Processing: A tale of two Outstanding Materials
Get PDFThis article aims to give a brief introduction on diamond, its important properties and processing techniques starting from a rough diamond, primarily for the readers from the non-diamond professionals. A sincere effort has been made to describe how chalcogenide glasses can play an important role for diamond processing, especially at the rough diamond inspection stage to help the diamond professionals for making a perfect process planning to realize an augmented
profitability. Chalcogenide glass being a non-oxide and non-conventional glass, a brief overview on this glass, its important properties and specialized fabrication technique has been presented. Finally, diamond processing technique using chalcogenide glass and its advantages has been
elucidated
Boron doped SiC thin film on Silicon synthesized from polycarbosilane: a new lead free material for applications in piezosensors
No full textIn this paper, we are reporting for the first time, the piezosensing characterisations of the SiC thin film on silicon, synthesized from boron containing Liquid Polycarbosilane (PCS) as a precursor deposited by Modified Chemical Vapour Deposition (MoCVD) technique followed by the structural characterisation of the film. Comparison was done on the result of the both undoped and doped SiC thin film to highlight the effect of boron doping on the piezo property of the SiC. Interestingly, it was observed that piezoelectric coefficient (d(33)) of the boron doped SiC thin film was substantially higher (21.33 pm/V) than the undoped SiC thin film (16.21 pm/V). The enhancement in d(33) was analysed considering the polarisation inside the thin film created by boron doping. The result shows a promising boron doped SiC thin film material for the application in high temperature piezo sensors
Study on the Synthesis and Structural Properties of Zeolite A-MgO Composite for Defluoridation of Water
No full textZeolite A-MgO composite was synthesized in presence of zeolite A particles, MgCl2 and urea solution under hydrothermal reaction at 150(o)C for 5 h followed by calcination at 600 degrees C/2 h. XRD and FTIR results showed the crystallization of MgO along with NaA zeolite crystals. Nano-sheet like MgO particles (50-70 nm) were grown onto the surface of NaA zeolite crystals (1 mu m). BET surface area and pore size of the sample were found to be 69 m(2).g(-1) and 3.9 nm, respectively. XPS analysis showed the binding energies of O1s, Si2p, Na1s, Al2p and Mg2p as 531.6, 102.4, 1072.2, 74.2 and 49.9 eV, respectively. The synthesized product (1 g.L-1 dose) showed 72% adsorption of fluoride (7.24 mg.L-1) within 5 min and reached up to 94% for 90 min at pH 6.8. The adsorption capacity of the sample was calculated as 107.64 mg.g(-1) from Langmuir isotherm. The sample could be regenerated up to 5th cycle. A tentative mechanism for the adsorption of fluoride from aqueous solution by the synthesized zeolite A-MgO composite was proposed
Hydrophobic functionalization of cellulosic substrate by tetrafluoroethane dielectric barrier discharge plasma at atmospheric pressure
No full textHydrophobic functionalization of cellulosic fabric (viscose) was carried out using helium/tetrafluoroethane (He/ TFE) plasma, a commercially available fluorocarbon gas, at the atmospheric pressure. By selecting suitable plasma parameters, He/TFE plasma was produced and maintained in glow state so that the various fragments of TFE in plasma zone could react covalently with the cellulose. After the plasma treatment, the highly hydrophilic cellulosic fabric turned into superhydrophobic fabric with a water absorbency time of >> 60 min, a water contact angle of 153 degrees and a water rolling angle of 5 degrees. The functionalization was found to be wash durable to 25 laundry cycles. From the analyses of species present in plasma zone by optical emission spectroscopy (OES), gas chromatography-mass spectrometry (GC-MS), and the chemical nature of the functionalized substrate by scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and secondary ion mass spectrometry (SIMS), a possible mechanism involved in the reaction of TFE fragments with cellulose macromolecule was arrived at. Further, it could be inferred that the modification took place only at the surface of the fibres at the nanometre level. The study postulates that it is possible to elucidate reactions undergoing in plasma zone and to control them to achieve desirable modification of substrates
Gain clamping performance of Hafnia-bismuth-erbium co-doped fibre amplifier using lasing controlled structure with FBG
No full textIn this study, the gain clamping performance of Hafnia-bismuth-erbium co-doped fibre amplifier (HB-EDFA) using a lasing controlled structure with fibre Bragg grating (FBG) pair is presented. First, the gain and noise figure (NF) characteristics of a bidirectionally pumped HB-EDFA with very short lengths of heavily doped fibre are presented regarding its critical design parameters such as HB-EDF length, pump power, input signal power and signal wavelength. Then, the gain clamping performance of a bidirectionally pumped HB-EDFA having a C-band FBG pair with Bragg wavelengths of 1534 and 1542 nm is experimentally analysed. A good gain clamping capability was obtained using the proposed bidirectionally HB-EDFA design which has resulted in a dynamic signal input power range of 25 dB at 16 dB signal gain for 1.6 m HB-EDF length, and a wider dynamic signal input power range of 30 dB at 10 dB signal gain for 1.1 m HB-EDF length
Perspective of Membrane Processes for the Removal of Arsenic from Water: An Overview
No full textThis article reviews different membrane processes for the removal of arsenic from groundwater. The source of arsenic and its toxic effects on human body are illustrated. Various membrane filtration processes like micro-filtration, nano-filtration, ultra-filtration and reverse osmosis are discussed. The materials used in different membrane techniques are highlighted towards the removal efficiency of arsenic from water. The influence of pH and coexisting ions on rejection efficiency towards the removal of arsenic of these different processes are studied. The constitution of membrane, rejection mechanism, merits and demerits of different membrane techniques and challenges involved therein are discussed. The future direction of research on membrane based technology is also highlighted in this review