IR@CGCRI - Central Glass and Ceramic Research Institute (CSIR)
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Effect of alumina impurity on microstructure and properties of alumina based conventionally brazed joints
Get PDFMo-Mn metallization of alumina ceramics of different purity has been performed at 1400 degrees C for 10 min in moist hydrogen and nitrogen atmosphere. Nickel coating has been applied onto the metallized alumina ceramics at 1000 degrees C for 1 h in a reducing hydrogen atmosphere. Finally, metallized and nickel coated alumina ceramics has been brazed with another metallized and nickel coated alumina ceramics using CuAg filler alloy at 900 degrees C for 10 min in a vacuum furnace at 1 x 10(-6) Ton pressure. X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) analysis has been carried out for phase analysis, microstructural investigation and elemental composition analysis. The adhesive strength of the metallizing layer and brazing strength of the joint have been measured by pull down breaking strength method. SEM study has shown that the width of the interfacial reaction region between the metallizing layer and substrate enhances with increasing the impurity content in the alumina ceramics. It has been observed that the adhesive strength of the metallizing layer depends on the interfacial reaction layer thickness. The adhesive strength of the metallizing layer has been increased with increasing the thickness of interfacial reaction layer. High adhesive strength of the metallizing layer as well as brazing strength has been achieved for alumina ceramics with high impurity content
Fabrication and photoelectrochemical activity of hierarchically Porous TiO2-ZnO heterojunction film
No full textFor the first time, we report the fabrication of hierarchically (macro with nested meso) porous nanocrystalline TiO2-ZnO heterojunction film onto fluorine-doped tin oxide-coated glass substrate by colloidal crystal templating technique using poly(methyl methacrylate) (PMMA) spheres as template. Accordingly, the precursor solutions of titanium isopropoxide and zinc acetate dihydrate in the presence of Pluronic P123 were used to impregnate the individual solution into the template. Initially, nanocrystalline TiO(2)inverse opal mesoporous film was deposited using the titanium precursor. The film was cured at 450 degrees C in an air atmosphere. A similar process was adopted to deposit nanocrystalline ZnO inverse opal mesoporous film onto the TiO(2)to obtain hierarchically porous TiO2-ZnO heterojunction nanocrystalline film. Morphology of the fabricated films showed a periodic arrangement of macropores, whereas the microstructural analysis confirmed the presence of nested mesopores in the film network. Chemical interaction existed between TiO(2)with ZnO forming the heterojunction film was ascertained by X-ray photoelectron spectroscopy. Light harvesting efficiency of the samples was studied, and the photoelectrochemical (PEC) performance of the hierarchically porous heterojunction films as photoanode showed about 5 times enhancement in photocurrent density compared to the pristine metal-oxide-semiconductor film under visible light exposure. The porous nanocrystalline hierarchically porous inverse opal heterojunction film could be used as an efficient photoanode in PEC cell
Effective Separation of Photogenerated Electron-Hole Pairs by Radial Field Facilitates Ultrahigh Photoresponse in Single Semiconductor Nanowire Photodetectors
No full textWe report an investigation on the observation of ultrahigh photoresponse (photogain, G(Pc) > 10(6)) in single nanowire photodetectors of diameter <100 nm. The investigation, which is a combination of experimental observations and theoretical analysis of the ultrahigh optical response of semiconductor nanowires, has been carried out with an emphasis on Ge nanowires. Semiconductor nanowire photodetectors show a signature of photogating where G(Pc) rolls off with increasing illumination intensity. We show that surface band bending due to depleted surface layers in nanowires induces a strong radial field (similar to 10(8 )V/m at the nanowire surface) that causes physical separation of photogenerated electron-hole pairs. This was established quantitatively through a self-consistent theoretical model based on coupled Schrodinger and Poisson equations. It shows that carrier separation slows down the surface recombination velocity to a low value (<1 cm/s), thus reducing the carrier recombination rate and extending the recombination lifetime by a few orders of magnitude. An important outcome of the model is the prediction of G(Pc) similar to 10(6) in a single Ge nanowire (with diameter 60 nm), which matches well with our experimental observation. The model also shows an inverse dependence of G(Pc) on the diameter that has been observed experimentally. Though carried out in the context of Ge nanowires, the physical model developed has general applicability in other semiconductor nanowires as well
Optical and magnetic properties of terbium doped zinc oxide nanoparticles with lithium as charge compensator
No full textRare earth doped ZnO continues to be a topic of interest since the current predominating semiconductor (ZnO) nanomaterials is tending towards limited functionality. The present study has been conducted to investigate the role of Li concentration (0.25-1.0%) on optical and magnetic properties of sol-gel derived Tb (1%) doped zinc oxide nanoparticles, which is useful in ZnO based optoelectronics devices. The XPS result ascertained the oxidation state of all elements in the samples. The absorption study demonstrated the encroachment in the visible region up to 600 nm with the incorporation of Li1.0% in Tb-doped zinc oxide. The photoluminescence ana-lysis is used to demonstrate the enhancement in Tb related peak with Li (0.5%) co-doping con-centration. Magnetic measurement indicates the weak ferromagnetic behaviour in synthesized doped ZnO samples, while pure zinc oxide shows small diamagnetic response with a contribution of ferromagnetism. The non-magnetic lithium ions stabilize the cation vacancies and support the magnetic nature of terbium. Tuning of properties in rare earth doped ZnO without change in rare earth (Tb) doping concentration has been obtained by co-doping of Li. The specific properties can be used in different electro-optic and magnetic devices
Synergistic anti-cancer activity of etoposide drug loaded calcium aluminium layered double hydroxide nanoconjugate for possible application in non small cell lung carcinoma
No full textThe present research reports a facile synthesis of bare phase pure CaAl-LDH nanoparticle (sample A) and intercalation of anti-cancer drug etoposide (ETO) into the same via simple anion exchange technique to obtain ETO loaded CaAl-LDH (sample B). The basal spacing (d(002)) of sample A was increased from 8.5764 angstrom to 17.18 angstrom upon intercalation of ETO. Further ETO loading was found to be 27.72% as estimated by UV-Vis spectrophotometer. The release profile of ETO from sample B in phosphate buffer saline (PBS) at pH 7.4 follows quasi-Fickian diffusion phenomenon in Korsmeyer-Peppas kinetics model. In vitro cell viability was undertaken using A549 (human lung adenocarcinoma) cell line in a dose dependent manner to determine the synergistic anti-cancer potential of sample B. It was observed that at an equivalent dose, the cancer cell viability was substantially reduced, in case of sample B compared to sample A and bare etoposide drug, respectively, which was further corroborated by cell proliferation/migration assay. The cellular uptake using A549 cell line showed an increasing trend with increasing time period (11.67% and 19.30% at 24 h and 72 h) respectively, confirmed by flow cytometry, exhibiting a substantial reduction of CAMKIIa protein for sample A and sample B to 110.52 pg/ml and 95.14 pg/ml respectively. Results also showed significant down regulation of SOD gene activity. All the above results exhibited the synergistic anti-cancer potential of sample B for possible application in the management of non small cell lung carcinoma (NSCLC)
Nano gold coated hierarchically porous zinc titanium oxide sol-gel based thin film: fabrication and photoelectrochemical activity
No full textIn this work, for the first time homogeneously distributed near periodic macroporous (HDPM) with nested mesoporous (hierarchically porous) semicrystalline zinc titanium oxide (ZTO) thin film on pure silica glass and fluorine doped tin oxide coated glass substrates was deposited by sol-gel dip coating technique from an optimized precursor solution of zinc nitrate hexahydrate and titanium isopropoxide with acetylacetone in low boiling solvents. The HDPM film formation was carried out by simple breath figure method where the pore formation occurred from the generated water droplets via molecular condensation onto the as-deposited cold solution film surface owing to solvent evaporation. Zinc to titanium ratio in precursor solution, room relative humidity and other critical parameters were tailored towards optimization of the periodic macropores formation. Gold nanoparticles (NPs) were further deposited onto the ZTO thin films by solution technique. Crystallinity, surface morphology and microstructure of the thin films were critically analyzed by X-ray diffraction, atomic force, scanning, and transmission electron microscopic studies. The photoelectrochemical (PEC) performance of the films was examined under visible light irradiation. A significant improvement in PEC activity was observed in nano Au coated hierarchically porous thin film. This facile fabrication process could be applied in different mixed metal oxide thin films for improving the PEC activity of the materials
Mn incorporated MoS2 nanoflowers: A high performance electrode material for symmetric supercapacitor
No full textEnergy storage devices based on the two-dimensional transition metal dichalcogenides (TMDs) have great interest due to their fascinating physical and chemical properties. In this study, Mn incorporated MoS2 nanosheets are self-assembled into nanoflowers via a simple one-step hydrothermal process. The nanoflowers retain the feature of the high specific surface area of the nanosheets and the intercalation of Mn atoms up to a certain amount increases the porosity of MoS2, thus enhancing active sites for reaction. The presence of an intermediate oxidation state of Mn (Mn3+), which also plays an important role in increasing capacitance, is highest in low doped sample resulting in superior capacitance performance compared to bare and high Mn content samples. So the supercapacitor electrode made of low Mn incorporated MoS2 nanoflowers exhibits maximum specific capacitance (430 F g(-1)), energy density 48.9 W h kg(-1) and power density 5.0 kW kg(-1) with excellent capacitance retention up to 5000 cycles at 10 A g(-1), when used as a supercapacitor electrode. Further, the performance of the electrode material has been examined by lightning four LED bulbs in series showing longer discharge time. Our findings open new areas to explore Mn doping with TMDs as next-generation energy devices systematically. (C) 2020 Elsevier Ltd. All rights reserved
Synthesis of novel ternary g-C3N4/SiC/C-Dots photocatalysts and their visible-light-induced activities in removal of various contaminants
No full textDifferent visible-light-driven nanocomposites were fabricated via combination of g-C3N4 (CN) with SiC and carbon dots (C-Dots) in the current research work. The features of photocatalysts were investigated by various analyses. The photocatalytic abilities were investigated by removal four aquatic pollutants. The outcomes demonstrated that the CN/SiC/C-Dots (0.25 mL) system has excellent photoability in the elimination of MB, fuchsine, RhB, and CR, which was about 26.9, 20.9, 24.4, and 15.2-folds premier than the single CN, respectively. The boosted photodegradation performance was related to the efficient separation of charges and high visible-light absorption, be- cause of coupling CN with SiC and C-Dots. It was confirmed that the h(+) and O-2(-) plays essential roles in pho- tocatalytic abilities. In our belief, this research work represents a novel method for the production of ternary metal-free nanocomposites based on CN, which could efficiently solve environmental crises
Microstructure, phase and electrical conductivity analyses of spark plasma sintered boron carbide machined with WEDM
No full textElectrical conductivity is an essential property for machining of sintered boron carbide especially by wire electrical discharge machining (WEDM) process. Pure boron carbide was spark plasma sintered to full density at 2050 degrees C. Rietveld refinement on XRD analysis confirmed presence of B13C2 as the major phase in the powder as well as in the sintered samples.Electrical conductivity was found to be similar to 48 Omega(-1) m(-1). The sintered specimens were successfully machined using WEDM technique. The microstructure of powder, machined and fractured surfaces of the sintered boron carbide were analyzed. At low power of WEDM with pulse current less than 140 A formation of molten, oxidized phases of boron carbide was observed as well as the development of surface cracks were minimum on the machined surface. Thus this work is aiming at achieving better product quality with sintered boron carbide specimens which are machined by WEDM
Review—Non-Invasive Monitoring of Human Health by Exhaled Breath Analysis: A Comprehensive Review
Get PDFExhaled human breath analysis is a very promisingfield of research work having great potential for diagnosis of diseases in non-invasive way. Breath analysis has attracted huge attention in thefield of medical diagnosis and disease monitoring in the last twodecades. VOCs/gases (Volatile Organic Compounds) in exhaled breath bear thefinger-prints of metabolic and biophysicalprocesses going on in human body. It’s a non-invasive, fast, non-hazardous, cost effective, and point of care process for diseasestate monitoring and environmental exposure assessment in human beings. Some VOCs/gases in exhaled breath are bio-markers ofdifferent diseases and their presence in excess amount is indicative of un-healthiness. Breath analysis has the potential for earlydetection of diseases. However, it is still underused and commercial device is yet not available owing to multiferrious challenges.This review is intended to provide an overview of major biomarkers (VOCs/gases) present in exhaled breath, importance of theiranalysis towards disease monitoring, analytical techniques involved, promising materials for breath analysis etc. Finally, relatedchallenges and limitations along with future scope will be touched upon.will be touched upon