Power transformer is the one of the largely important as well as one of the costly elements in the electricity grid. Any
malfunction of this element may affect the reliability of the entire network and could have considerable economic impact
on the system. For several reasons, overloading of power transformers beyond their rating has been reported frequently.
The primary issue leading to the failure of transformer is contamination of transformer oil by the working components
due to prolonged high temperature exposure. Transformer oil temperature can be utilized as a primary parameter in
monitoring the life of the transformer. At present, electrical approach are vulnerable to electromagnetic interference and
are limited by sensors lifetime. Other non-contact techniques are ineffective due to difficulties in processing the output
signal. In this work a CuAlNi/Polyimide shape memory alloy composite has been applied to act as a temperature sensor
in mineral oils. The composite film has been developed through thermal evaporation which exhibited two-way
displacement without and post-processing and training. The developed films are employed in a custom made oil rig and
the suitability of using it as a circuit breaker in temperature sensing application has been probed. The circuit breaker can
be triggered by measuring the displacement of the bimorph using laser displacement sensor. The measurement is of noncontact
type and the temperature can be monitored at regular intervals. For comparison a procure Nickel-Titanium spring
with transformation temperature less than 100 °C is also used for the studies. The results show that the developed
bimorphs has good sensitivity of 0.2 mm/°C and the output displacement is significant. Further the effect of
contamination in the mineral oils is also probed by adding known amounts of impurities and the ageing effect has been
studied. A higher resolution measuring system using interferometry has been proposed.
We have succeeded in growing various ZnO nanocrystals, such as nanowires, nanorods, and nanowalls, by a
nanoparticle-assisted pulsed-laser deposition (NAPLD). In this study, low-density ZnO nanowires were synthesized by
introduction of a ZnO buffer layer. Low-density hexagonal cone-shape ZnO cores are formed on the buffer layer, and
vertically-aligned ZnO nanowires are grown on the cores. The density of the nanowires was clearly decreased with
increasing the thickness of the Buffer layer. The buffer layer can be used as one of the effective additives to control the
growth density of the ZnO nano-crystals synthesized by NAPLD.
Fabrication of textured poly-crystalline silicon films from amorphous-silicon (a-Si) films using a line beam is
investigated. The mechanism of laser annealing and simultaneously form a nano-textured surface using an Nd3+: YAG
laser at a wavelength of 355 nm with a line beam is discussed. Amorphous-Si films coated on glass and crystalline
silicon substrates were treated with different laser fluence from 100 to 600 mJ/cm2 and with 90% beam overlap. The
crystallization and texturization characteristics were analyzed through SEM, Raman Spectroscopy, AFM, resistance and
absorbance measurements. Generation of polycrystalline textured peaks was confirmed with different characterization
methods and compared with the results of the conventional circular beam. This approach of line beam with increase in
the scanning speed will allow the faster production of polycrystalline silicon from a-Si for photovoltaic application.
Efficient doping of amorphous silicon(a-Si) is a key issue in the field of photovoltaic applications. In this paper an
attempt has been made to produce a highly highly textured Sb doped a-Si. The a-Si were coated with Sb to a thickness
of 200nm using vacuum evaporation method and treated with an Nd:YAG laser of 355nm with a threshold fluence of
460mJ/cm2 by overlapping the laser spots to 90% of its size. The samples are retretaed with a low laser fluence of
230mJ/cm2 respectively so as to crytsallize and diffuse the Sb on to the surface and to activate the dopant. The laser
doped and subequently laser textured samples were analysed through Scanning Electron microscope (SEM), X-ray
diffraction (XRD) & Atomic Force Microscope(AFM).The traces of SiSb in the XRD peak with improved surface
roughness were observed on the laser doped samples. This represents that the dopants are highly diffused on the a-Si.
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