Recent Trends in Power Transformer Fault Diagnosis and Condition Assessment

Power transformers are interface between different voltage levels of essential importance. Because of the long manufacturing processes, transformers are one of the most critical and expensive equipment and so this is one of the reasons why condition monitoring becomes more popular. Monitoring systems as basis for diagnostics open the possibility for expanding the operating time, reducing the risk of expensive failures and allows several maintenance strategies. With different monitoring techniques, detailed informations about the transformer condition can be received and helps to minimize the probability of an unexpected outage. In this paper a methodology has been developed to use information derived from condition monitoring and diagnostics for rehabilitation purposes of transformers. The interpretation and understanding of the test data are obtained from the International Standards

Effect of Ga doping on Microstructural, Optical and Photocatalytic Properties of Nanostructured Zinc Oxide Thin Films

Ga doped nanostructured zinc oxide thin films (thickness, 160-170 nm) on pure silica glass substrate were prepared from zinc acetate based precursor solutions by varying Ga doping level (0 to 6%). The presence of nanocrystalline hexagonal ZnO was confirmed by X-ray diffraction study whereas the field emission scanning and transmission electron microscopic analyses evidenced the existence of quasi-spherical ZnO with a decreased trend in crystallite/particle size vis-à-vis an enhancement of direct band gap energy of the films on increasing the doping level. Root means square (RMS) film surface roughness was determined by atomic force microscope and found maximum RMS roughness value in 1% doped film. Photoluminescence (PL) emission spectral study revealed the formation of various intrinsic/extrinsic defects along with the presence of characteristics band edge emission of ZnO at ~ 385 nm (UVPL). However, a lowest relative intensity of the UVPL emission was found in 1% doped film (G1ZO), indicating an appreciable decrease in the recombination rate of photogenerated charge carriers in the semiconductor. The photocatalytic activity of the films towards degradation of rhodamine 6G dye was performed under UV (254 nm) and obtained the maximum value of dye degradation rate constant (considering first order reaction kinetics) in 1% doped film (G1ZO). On increasing doping level, the trend in change of defect concentration (oxygen vacancies) as analyzed by Raman spectral study was found identical with the dye photodegradation activity of the films. The G1ZO film would expect to decompose micro-organisms even under exposure of visible light

Indium Oxide Based Nanomaterials: Fabrication Strategies, Properties, Applications, Challenges and Future Prospect

Nanostructured metal oxide semiconductors (MOS) in the form of thin film or bulk attract significant interest of materials researchers in both basic and applied sciences. Among these important MOSs, indium oxide (IO) is a valuable one due to its novel properties and wide range of applications in diversified fields. IO based nanostructured thin films possess excellent visible transparency, metal-like electrical conductivity and infrared reflectance properties. This chapter mainly highlights the synthesis strategies of IO based bulk nanomaterials with variable morphologies starting from spherical nanoparticles to nano-rods, nano-wires, nano-needles, nanopencils, nanopushpins etc. In addition, thin film deposition and periodic 1-dimensional (1D)/2-dimensional (2D) surface texturing techniques of IO based nanostructured thin films vis-à-vis their functional properties and applications have been discussed. The chapter covers a state-of-the-art survey on the fabrication strategies and recent advancement in the properties of IO based nanomaterials with their different areas of applications. Finally, the challenges and future prospect of IO based nanomaterials have been discussed briefly

One pot low temperature synthesis of graphene coupled Gd-doped ZnFe2O4 nanocomposite for effective removal of antibiotic levofloxacin drug

Nanocomposites of reduced graphene oxide (rGO) coupled gadolinium doped ZnFe2O4 (GZFG) have been successfully one pot in-situ synthesized adopting low temperature solution process from zinc nitrate, iron nitrate, gadolinium acetate and graphene oxide with varying concentrations of gadolinium (upto 10% Gd with respect to Zn) in the precursor medium. X-ray diffraction and transmission electron microscopy studies confirm the presence of single phase cubic spinel structure of ZnFe2O4 that uniformly distributed over the rGO layers. With increasing Gd doping concentration in precursor medium, the average crystallite size of ZnFe2O4 diminishes gradually from similar to 11 to similar to 5.5 nm. Raman and X-ray photoelectron spectral analyses confirm an existence of interaction between rGO and ZnFe2O4 in GZFG samples. Using antibiotic levofloxacin in water, the drug removal capacity (DRC) of GZFG has been performed by optimization of parameters such as gadolinium doping concentration in precursor medium, solution pH, etc. However, the gadolinium doping leads to an improvement in DRC of the nanocomposite and the 5% Gd doped sample shows about 86% DRC at the optimized condition. This simple strategy can be utilized in the synthesis of rGO coupled Gd doped other metal oxide nanocomposites for DRC application. GRAPHICS]

Antimicrobial activity study of Ag-ZnO nanoflowers synthesised from neem extract and application in cotton textiles

Zinc oxide has gained a tremendous attention from materials researchers owing to its availability, ease of synthesis, biocompatibility, low cytotoxicity and widespread applications. A few green synthesis methods are available in the literature for making hierarchically structured ZnO (ZO)/metal doped ZnO. In this work, a green synthesis of Ag-ZnO flowers (AZO) has been performed from neem extract (Azadiracta indica) by low temperature solution method. Material properties of the samples such as crystallinity/crystal phase, morphology and optical property have been investigated systematically. In addition, the effect of AZO upon the growth of gram positive/negative bacteria has been studied. As prepared AZO along with a biocompatible and chitosan having antimicrobial property has been used for deposition of a robust coating on commercial cotton fabric. The morphology, chemical bond vibrations and antimicrobial activity of the coated fabric against E. coli, S. aureus and fungi C. albicans have been studied. The coated fabric shows excellent antibacterial and antifungal activities. Thus, the material can be used as medical textile in research laboratory and/or other health sectors

Hierarchically structured alpha-nickel hydroxide based superhydrophobic and antibacterial coating on cellulosic materials for oil-water separation

Inspired by hierarchical surface structure of lotus leaf and insect wings, a uniform coating of disorderly oriented semi crystalline alpha-Ni(OH)(2) nanosheets for creating dual scale (micro-nano) has been developed on cellulosic materials (cotton and wood) by a one-step facile solution process. The coating shows an innate superhydrophobic nature with a static water contact angle (SCA) similar to 157 degrees and water shedding angle (WSA) similar to 10 degrees. Growth pattern, morphology and microstructure, thermogravimetric mass loss behaviour and chemical bonding of alpha-Ni(OH)(2) with commercially available cotton fabric as well as antibacterial activity of the coated fabric towards gram positive and negative bacteria have been studied systematically. For long term use as a filter cloth for oil-water separation, the coating is further modified with hexadecyltrimethoxysilane (HDTMS) restoring the hierarchical structure of alpha-Ni(OH)(2). The dual scale surface roughness as well as low surface energy long chain HDTMS layer renders the coating a stable SCA similar to 162 degrees and WSA similar to 8 degrees. The superhydrophobic and superoleophilic alpha-Ni(OH)(2)-HDTMS coating shows self-cleaning ability, similar to 99% oil-water separation efficiency including reusability over 50 separation cycles. The coated sample also shows excellent chemical and mechanical stability as well as laundering fastness. This facile fabrication process can make an avenue for development of other transition metal hydroxides based superhydrophobic and superoleophilic coatings on cellulosic materials

Protein adsorption capability of zinc ferrite nanoparticles formed by a low-temperature solution-based process

We report successful synthesis of zinc ferrite nanoparticles (ZFs) by a facile low-temperature (90 degrees C) solution-based process from ferric nitrate nonahydrate and zinc nitrate hexahydrate precursors in presence of hydrazine hydrate. X-ray diffraction analysis and transmission electron microscopy confirmed the presence of ZFs, which were further characterized by Fourier-transform infrared (FTIR) spectroscopy and thermogravimetric measurements for identification of characteristic chemical bond vibrations and thermal weight loss behavior, respectively. Measurements of magnetic properties at room temperature revealed that the sample showed quite high saturation magnetization (22.0 emu/g at similar to 19,200 G), implying the presence of less impurities/surface defects in the ZFs. The material also showed zero coercivity as a soft-magnetic material. The protein adsorption performance of the ZFs was checked using bovine serum albumin (BSA) as model protein. Excellent protein adsorption capacity of 210 mg/g (close to the value of 218.81 mg/g calculated using the Langmuir model) for BSA concentration of 0.3 mg/mL was obtained at optimized solution pH of 5. This simple process could be adopted for synthesis of different magnetic nanomaterials for use in biomedical applications

Fabrication, structural evaluation, optical and photoelectrochemical properties of soft lithography based 1D/2D surface patterned indium titanium oxide sol-gel thin film

For the first time, we report on successful fabrication of 1-dimensional (ID) nanoprism and 2-dimensional (2D) nanocone shaped surface patterned amorphous indium titanium oxide (INTO) sol-gel based mesoporous thin films on glass by soft lithography. Structural evaluation of the surface patterns over amorphous thin film surfaces was performed by atomic force and transmission electron microscopes as well as X-ray diffraction study. Chemical bonding/oxidation state of constituent elements in INTO film matrix was analyzed by FTIR and X-ray photoelectron spectroscopies. Maximum optical absorption and minimum specular surface reflection in visible region were noticed in 20 patterned film. The thin film with physical thickness over 100 nm was mesoporous in nature (similar to 14% porosity) as measured by spectroscopic ellipsometer. A significant improvement in photoelectrochemical (PEC) activity was found in 2D patterned film under visible light that could be associated with the enhancement in light absorption/trapping by the periodic nanocones. Moreover, the existence of mesopores could provide excess active sites for electrolyte diffusion and mass transportation. Thus, the mesoporous 2D patterned thin film could have substantial opportunity in solar energy conversion. The facile technique could create an avenue for fabrication of complexed surface patterned thin films with improved PEC property. (C) 2017 Elsevier B.V. All rights reserved

Nano gold coated hierarchically porous zinc titanium oxide sol-gel based thin film: fabrication and photoelectrochemical activity

In 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