IR@CGCRI - Central Glass and Ceramic Research Institute (CSIR)
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AlN-SWCNT Metacomposites Having Tunable Negative Permittivity in Radio and Microwave Frequencies
No full textDiscovery of plasmon resonance and negative permittivity in carbon allotropes at much lower frequencies than those of metals has evoked interest to develop random metacomposites by suitable means of addition of these dispersoids in an overall dielectric matrix. Random metacomposites have always the advantage for their easy preparation techniques over those of their regular arrayed artificial counterpart. However, thermal management during the heat generation by electromagnetic attenuation in metamaterials is not yet studied well. The present communication discusses the dielectric permittivities and loss parameters of aluminum nitride-single-wall carbon nanotube (AlN-SWCNT) composites considering high thermal conductivities of both materials. The composites are dense and have been prepared by a standard powder technological method using hot pressing at 1850 degrees C under a nitrogen atmosphere. Increase in the negative permittivity value with SWCNT concentration (1, 3, and 6 vol %) in the composites had been observed at low frequencies. Characterization of the materials with Fourier transform infrared (FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, and microstructure analysis by scanning and transmission electron microscopy (TEM) revealed the survivability of the SWCNTs and the nature of the matrix-filler interface. Plasmonic resonance following Drude's law could be observed at much lower plasma frequencies than that of pure SWCNT and for very little SWCNT addition. Exhibition of the negative permittivity has been explained with relation to the microstructure of the composites observed from field emission scanning electron micrographs (FESEM), TEM images, and the equivalent circuit model. High energy conversion efficiency is expected in these composites due to the possession of dual functionalities like high thermal conductivity as well as high negative permittivity, which should ensure the application of these materials in wave filter, cloaking device, supercapacitors, and wireless communication
Optical Properties of Chromium and Erbium Co-Doped Alumina-Germania-Calcia-Yttria-Silica Based Fiber
No full textWe report the fabrication details and optical characterization of novel Erbium (Er) and Chromium (Cr) co-doped alumina-germania-calcia-yttria-silica fiber. Co-doping with Er and Cr is chosen as potentially promising for enhancing the fiber's fluorescent and amplifying potential in the near-infrared (NIR) region at `resonant' (viz. into Er band absorption maximum, @976 nm) and `non-resonant' (viz. off Er band while into Cr broad absorption band, @905/1064 nm) excitations. Our results reveal strong coupling, at both kinds of excitation, of Er- and Cr- subsystems in the fiber. This effect is justified by the presence of pronounced 1.5-1.6 mu m emission, characteristic to Er ions, at 905/1064 nm excitations and, at 976-nm excitation, by notable spectral broadening of the fiber's NIR fluorescence and gain, comprising the lines inherent to Er3+ (1.5-1.6 mu m) and Cr3+/Cr4+ (1.15-1.45 mu m), as compared to purely Er-doped silicate fiber, exemplified here by commercial `L20' (Er20-4/125) and `L40' (Er40-4/125) fibers
Dispersion Study of Zirconia Nano-Powders Using Dolapix CE64 and M65 Dispersant to Develop UF Membrane over Novel Clay-Alumina Based Ceramic Support for Water Treatment
No full textDispersion of zirconia powder in aqueous suspension using suitable dispersant for coating application was studied. Zeta potential experiments were conducted in search of stable suspensions. Sedimentation tests were carried out in both acidic and basic pH range, i.e. from 2 to 11. Zirconia slurry as coating material was used for coating on clay-alumina tubular ceramic support. The slurry was composed of zirconia nano powder, water, dispersant and organic binder. Z irconia nano powders were characterized by XRD, surface area by multipoint BET and TEM. The effect of dispersant concentration on zeta potential of zirconia suspension and effect of pH, sedimentation rate and rheology (viscosity) of zirconia suspension were studied. The coated tubes were air dried and sintered in furnace at 700 degrees C for 2 h. The prepared UF membrane was subjected to characterization in terms of permeability, FESEM, molecular weight cut off, etc. The UF membrane was used for separation of two types of water - effluent A (kitchen sink wastewater) and effluent B (surface water of a lake). The membrane was effective to remove the pathogenic organisms, organic load in terms of BOD, COD, etc. The treated water may be reused in agriculture or industrial purposes
Ethanol Sensing Properties of Nanocrystalline alpha-MoO3
Get PDFEthanol sensors with effective and selective sensitivity are extensively used by traffic police to detect drunken drivers, in wine industries for controlling the fermentation process, food package testing, different medical applications etc. Orthorhombic phase pure alpha-MoO3 nanoparticles were synthesized via facile sol-gel technique to ethanol sensor. It was observed that the gas sensing response of the sample toward 100 ppm of ethanol vapor is 59% at 350 degrees C. The response and the recovery time of the gas sensor toward 100 ppm ethanol vapor are found to be 34 s and 70 s, respectively. The main obstacle for a gas sensor to be an excellent breath analyser is to remain insensitive toward the main interfering agent of exhaling human breath i.e. moisture. Prepared sensor is highly selective and shows almost no response toward saturated moisture
Thermal Shock Resistance of Porous Silicon Carbide Ceramics Prepared Using Clay and Alumina as Additives
No full textPorous silicon carbide ceramics were prepared by an in situ reaction bonding process using clay and alumina as additives. The effects of alumina additive, pore former on phase composition, microstructure, flexural strength and thermal shock resistance of the ceramics were studied. Thermal shock resistance of porous SiC ceramics due to cooling was evaluated as a function of quenching temperatures and quenching cycles using water- and air-quenching technique. It was observed that residual strength of the quenched samples in water decreased with increase in the quenching temperature but was almost independent of quenching cycles. In water quenching, the surface of the sample cooled almost instantly but the inside remained hot which created an uneven thermal profile and generated microcracks in the sample; as a result sudden reduction of flexural strength was observed. The results showed that flexural strength and thermal shock resistance properties of the ceramics prepared with alumina are better than those of the ceramics prepared without alumina and the material was found suitable for hot gas filtration application
Corrigendum to "Al-Mg-Ca-Layered Double Oxides for Efficient Removal of As(V) from Water: The Role of Amides" (vol 64, pg 1594, 2019)
Get PDFCorrigendum to "Hierarchical Porous Carbon Nanospheres for Efficient Removal of Toxic Organic Water Contaminants of Phenol and Methylene Blue" (vol 63, pg 559, 2018)
Get PDFGreen synthesis of iron oxide nanoparticles for arsenic remediation in water and sludge utilization
No full textIron oxide nanoparticles (IONPs) were synthesized via an affordable and environmentally friendly route using waste banana peel extract. The polyphenol-rich extract acted as a stabilizing and reducing agent resulting in formation of -Fe2O3 with a particle size of around 60nm. The composition, phase, morphology and size of the nanoparticles were analyzed by X-ray diffraction, field emission scanning electron microscopy, Fourier transform infrared spectroscopy, transmission electron microscopy and a Zetasizer. The efficiency of the IONPs was assessed in terms of arsenic(V) remediation from contaminated water within the range of 0.1-2.0mg/L. Batch study showed that IONPs had a high As(V) adsorption capacity of about 2.715mg/g at 40 degrees C. A statistical approach, viz. an artificial neural network, was adapted for modeling and optimization of the process parameters for achieving maximum As(V) removal efficiency. A set of 54 experimental sets were conducted and the predicted model generated showed an R-2 value of 0.9971 and the corresponding mean squared error value was 0.0000601. Surface binding of the As(V) phenomenon on the green synthesized IONPs was explained on the basis of FTIR spectroscopy, X-ray photoelectron spectroscopy, X-ray fluorescence spectroscopy of the control and the As(V)-loaded IONPs.The spent adsorbent was successfully immobilized in phosphate glass matrix with an objective to provide a complete and sustainable solution for arsenic contamination
Size engineered Cu-doped alpha-MnO2 nanoparticles for exaggerated photocatalytic activity and energy storage application
No full textThis investigation involves the synthesis of Cu doped alpha-MnO2 nanoparticles through modified Chemical route. Obtained nanoparticles (diameter_(similar to)5 nm to (similar to)18 nm) are found mostly stable at high temperature and its size can be modulated by Cu doping and post sintering temperature variation. Cyclic voltammetry and galvanostatic charge-discharge performance indicate the excellent cycling stability along with a maximum capacitance of 229.5 F/g for current density of 1 A/g. Our fabricated device is also capable to power up 73 numbers of LED for 10 min after being charged for 10 s. From the photocatalytic experiment, degradation efficiency of 73.1% has been achieved by using even ultra diluted aqueous solution (0.0025 g/L) of active material to degrade the pollutant dye like Brilliant Green of 5 ppm concentration. Entire results suggest that the synthesized materials are the promising candidate to be used in photocatalysis and supercapacitive application purpose