Influence of substrate temperature on the properties of oxygen‐ion‐assisted deposited CeO2 films

Substrate temperature and ion bombardment during deposition have been observed to modify significantly the optical and structural properties of dielectric thin films. Single‐layer films of CeO2 have been deposited by electron beam evaporation with simultaneous oxygen‐ion bombardment using a Kaufman broad beam ion source and maintaining the substrates at elevated temperature. A systematic study has been made on the influence of (a) substrate temperature in the range ambient to 300 °C, (b) ion energy in the range 300–700 eV, and (c) ion current density 100–220 μA/cm2 on optical properties such as refractive index, extinction coefficient, inhomogeneity, packing density, and structural properties. The refractive index increased with in increase in substrate temperature: ion energy up to 600 eV and ion current density. Homogeneous, absorption free and high index (2.48) films have been obtained at 600 eV, 220 μA/cm2 and at substrate temperature of 300 °C. The packing density of the films was observed to be unity for the same deposition conditions. Substrate temperature with simultaneous ion bombardment modified the structure of the films from highly ordered to fine grain structure.

Influence of surge impedance of the connecting lead in response time measurement of u.h.v. damped capacitive voltage dividers

In the determination of the response time of u.h.v. damped capacitive impulse voltage dividers using the CIGRE IMR-1MS group (1) method and the arrangement suggested by the International Electrotechnical Commission (the I EC square loop),the surge impedance of the connecting lead has been found to influence the accuracy of determination. To avoid this difficulty,a new graphical procedure is proposed. As this method uses only those data points which can be determined with good accuracy, errors in response-time area evaluation do not influence the result.

Influence of Switching Conditions on the VETO Magnitudes in a GIS

Estimation of very fast transient overvoltage (VFTO) has been carried out using EMTP for various switching conditions in a 420 kV gas-insulated substation (GIS). The variation of the VFTO peak along the GIS bus nodes for disconnector and circuit breaker switching operations, as well as the variation of VFTO peak with different magnitudes of trapped charges, have been studied. The results indicate a distinct pattern of variation of VFTO peak along the nodes of the GIS bus in the case of disconnector switch operation as compared to that of circuit-breaker operation. It has also been noticed that the variation of VFTO peak levels are not in direct proportion to the trapped charge present on the HV bus.

Influence of Phase Connection and Terminal Conditions on Natural Frequencies of Three-Phase Transformer Windings

With the increasing use of extra high-voltage transmission in power system expansion, the manufacturers of power apparatus and the electric utilities are studying the nature of overvoltages in power systems due to lightning and, in particular, switching operations. For such analyses, knowledge of the natural frequencies of the windings of transformers under a wide variety of conditions is important. The work reported by the author in a previous paper is extended and equivalent circuits have been developed to represent several sets of terminal conditions. These equivalent circuits can be used to determine the natural frequencies and transient voltages in the windings. Comparison of the measured and the computed results obtained with a model transformer indicates that they are in good agreement. Hence, this method of analysis provides a satisfactory procedure for the estimation of natural frequencies and transient voltages in transformer windings.

Influence of Tempered Microstructures on the Transformation Behaviour of Cold Deformed and Intercritically Annealed Medium Carbon Low Alloy Steel

This research is focused on understanding the role of microstructural variables and processing parameters in obtaining optimised dual phase structures in medium carbon low alloy steels. Tempered Martensite structures produced at 300, 500, and 650 degrees C, were cold rolled to varied degrees ranging from 20 to 80% deformation. Intercritical annealing was then performed at 740, 760, and 780 degrees C for various time duration ranging from 60 seconds to 60 minutes before quenching in water. The transformation behaviour was studied with the aid of optical microscopy and hardness curves. From the results, it is observed that microstructural condition, deformation, and intercritical temperatures influenced the chronological order of the competing stress relaxation and decomposition phase reactions which interfered with the rate of the expected alpha -> gamma transformation. The three unique transformation trends observed are systematically analyzed. It was also observed that the 300 and 500 degrees C tempered initial microstructures were unsuitable for the production of dual structures with optimized strength characteristics.

Influence of planning and governance on the level of urban services

A theoretical framework to analyse the interaction of planning and governance on the extent of outgrowth and level of services is proposed. An indicator framework for quantifying sprawl is also proposed and the same is operationalised for Bangalore. The indicators comprise spatial metrics (derived from temporal satellite remote sensing data) and other metrics obtained from a house-hold survey. The interaction of different indicators with respect to the core city and the outgrowth is determined by multi-dimensional scaling. The analysis reveals the underlying similarities (and dissimilarities) that relate with the different governance structures that prevail here. The paper concludes outlining the challenges in addressing urban sprawl while ensuring adequate level of services that planning and governance have to ensure towards achieving sustainable urbanisation.

The influence of Zr layer thickness on contact deformation and fracture in a ZrN-Zr multilayer coating

In order to understand the influence of ductile metal interlayer on the overall deformation behavior of metal/nitride multilayer, different configurations of metal and nitride layers were deposited and tested under indentation loading. To provide insight into the trends in deformation with multilayer spacings, an FEM model with elastic-perfect plastic metal layers alternate with an elastic nitride on top of an elastic-plastic substrate. The strong strain mismatch between the metal and nitride layers significantly alters the stress field under contact loading leading to micro-cracking in the nitride, large tensile stresses immediately below the contact, and a transition from columnar sliding in thin metal films to a more uniform bending and microcracking in thicker coatings.

Influence of nano-fillers on electrical treeing in epoxy insulation

This paper presents the results of a study on the effect of alumina nano-fillers on electrical tree growth in epoxy insulation. Treeing experiments were conducted at a fixed ac voltage of 15 kV, 50 Hz on unfilled epoxy samples as well as epoxy nanocomposites with different loadings of alumina nano-fillers. Time for tree inception as well as tree growth patterns were studied. The results show that there is a significant improvement in tree initiation time with the increase in nano-filler loading. Different tree growth patterns as well as slower tree growth with increasing filler loadings were observed in epoxy nanocomposites. The nature of the tree channel and the elemental composition of the material on the inner lining of the tree channels have been studied using SEM imaging and EDAX analysis respectively of the cut section of the tree channels. It has been shown that the type of bonding at the interface has an influence on the electrical tree growth pattern. The nature of the bonding at the interface between the epoxy and the nano-filler has been studied using FTIR spectrometry. Finally the influence of the interface on tree growth phenomena in nanocomposites has been explained by a physical model.

Influence of Si-C bond density on the properties of a-Si(1-x)C(x) thin films

Amorphous silicon carbide (a-Si(1-x)C(x)) films were deposited on silicon (100) and quartz substrates by pulsed DC reactive magnetron sputtering of silicon in methane (CH(4))-Argon (Ar) atmosphere. The influence of substrate temperature and target power on the composition, carbon bonding configuration, band gap, refractive index and hardness of a-SiC films has been investigated. Increase in substrate temperature results in slightly decreasing the carbon concentration in the films but favors silicon-carbon (Si-C) bonding. Also lower target powers were favorable towards Si-C bonding. X-ray photoelectron spectroscopy (XPS) results agree with the Fourier Transform Infrared (FTIR), UV-vis spectroscopy results. Increase in substrate temperature resulted in increased hardness of the thin films from 13 to 17 GPa and the corresponding bandgap varied from 2.1 to 1.8 eV. (C) 2011 Elsevier B.V. All rights reserved.

Influence of the Methane-Zeolite A Interaction Potential on the Concentration Dependence of Self-diffusivity

Studies on the diffusion of methane in a zeolite structure type LTA (as per IZA nomenclature) have indicated that different types of methane zeolite potentials exist in the literature in which methane is treated within the united-atom model. One set of potentials, referred to as model A, has a methane oxygen diameter of 3.14 angstrom, while another set of potential parameters, model B, employs a larger value of 3.46 angstrom. Fritzsche and co-workers (1993) have shown that these two potentials lead to two distinctly different energetic barriers for the passage of methane through the eight-ring window in the cation-free form of zeolite A. Here, we compute the variation of the self-diffusivity (D) with loading (c) for these two types of potentials and show that this slight variation in the diameter changes the concentration dependence qualitatively: thus, D decreases monotonically with c for model A, while D increases and goes through a maximum before finally decreasing for model B. This effect and the surprising congruence of the diffusion coefficients for both models at high loadings is examined in detail at the molecular level. Simulations for different temperatures reveal the Arrhenius behaviour of the self-diffusion coefficient. The apparent activation energy is found to vary with the loading. We conclude that beside the cage-to-cage jumps, which are essential for the migration of the guest molecules, at high concentrations migration within the cage and guest guest interactions with other molecules become increasingly dominant influences on the diffusion coefficient and make the guest zeolite interaction less important for both model A and model B.

Influence of minor addition of boron on tensile and fatigue properties of wrought Ti-6Al-4V alloy

Addition of boron to cast Ti-6Al-4V alloy leads to significant refinement in grain size, which in turn improves processibilty as well as the mechanical properties of the as-cast alloy. Room temperature tensile and fatigue properties of Wrought Ti-6Al-4V-B alloys with B up to 0.09 wt.% are investigated. Thermo-mechanical processing at 950 degrees C caused kinking of alpha lamellae and alignment of TiB particles in the flow direction with a negligible change in prior beta grain and colony sizes, indicating the absence of dynamic recrystallisation during forging. Characterisation with the aid of X-ray and electron back scattered diffraction reveal a strong basal texture in B free alloy which gets randomised with the 0.09B addition in the forged condition. Marginal enhancement in tensile and fatigue properties upon forging is noted. B free wrought Ti-6Al-4V alloy exhibits better tensile strength as compared to B containing alloy, due to the operation of < c+a > slip on pyramidal planes with high value of CRSS as compared to < a > slip on basal and prismatic planes. Decrease in fatigue strength of Ti-6Al-4V-0.04B in as-cast and the wrought state is observed due to increase in the volume fraction of grain boundary a phase with B addition, which acts as a crack nucleation site. No significant effect of TiB particles on tensile and fatigue properties is observed. (C) 2012 Elsevier B.V. All rights reserved.