Search results for "Ang"
showing 10 items of 39486 documents
Space charge accumulation in undersea HVDC cables as function of heat exchange conditions at the boundaries – water-air interface
2020
Transmission lines with undersea HVDC cables are an interesting technological solution for the supply of electrical energy to islands. The accumulation of space charge inside the dielectric layer of a HVDC cable is one of the most important element to consider in its design and during operation. The formation of space charge is due to various factors including the high dependence on the temperature of the electrical conductivity of the insulation and the establishment of a thermal gradient under load conditions. This research is focused on the space charge accumulation phenomenon around a section of a HVDC cable half dipped in water and half in air. Due to the high difference in thermal con…
Contributed Review: Review of thermal methods for space charge measurement.
2016
The space charge accumulation phenomenon has garnered great interest over the last two decades because of the increased use of direct current in high voltage electrical systems. In this context, a significant relevance has been achieved by the thermal methods, used for solid dielectrics. This paper presents a review of this non-destructive measurement system used for the measurement of space charge. The thermal pulse method, the thermal step method, and the laser intensity modulation method are described. For each configuration, the principle of operation, the thicknesses analyzed, and the spatial resolution are described, reporting also the main related applications
The challenge in realizing an exchange coupled BiFeO3-double perovskite bilayer
2020
Abstract In this work we propose a device design for efficient voltage control of magnetism. The magnetization of a ferrimagnetic double perovskite may be manipulated by an exchange coupled layer of multiferroic BiFeO3. Bilayers of Barium doped BiFeO3 and ferrimagnetic double perovskite Sr2FeMoO6 have been prepared by pulsed laser deposition motivated by the possibility of strong interlayer exchange coupling. While single layers of each material show high quality we observe that in both stacking orders the first layer decomposes during the deposition of the second layer. The reason for the decomposition are strongly differing growth conditions for BiFeO3 and Sr2FeMoO6. This means that the g…
Characteristics of industrially manufactured amorphous hydrogenated carbon (a-C:H) depositions on high-density polyethylene
2016
Industrially high-density polyethylene (HDPE) was successively covered by two types of amorphous hydrogenated carbon (a-C:H) films, one more flexible (f-type) and the other more robust (r-type). The films have been grown by radio frequency plasma-enhanced chemical vapor deposition (RF-PECVD) technique with acetylene plasma. The surface morphology of both types has been studied by atomic force microscopy (AFM) and scanning electron microscopy (SEM). Contact angle measurements and Raman spectroscopy analysis were done to investigate the surface wettability and carbon chemical composition. Both types display similar morphology and grain growth pattern. Contact angle measurements revealed surfa…
Temperature Coefficients of Crystal Defects in Multicrystalline Silicon Wafers
2020
This article investigates the influence of crystallographic defects on the temperature sensitivity of multicrystalline silicon wafers. The thermal characteristics of the implied open-circuit voltage is assessed since it determines most of the total temperature sensitivity of the material. Spatially resolved temperature-dependent analysis is performed on wafers from various brick positions; intragrain regions, grain boundaries, and dislocation clusters are examined. The crystal regions are studied before and after subjecting the wafers to phosphorus gettering, aiming to alter the metallic impurity concentration in various regions across the wafers. Most intragrain regions and grain boundarie…
Impact of Annealing Temperature on Tunneling Magnetoresistance Multilayer Stacks
2020
The effect of annealing temperatures on the tunnel magnetoresistance (TMR) of MgO-based magnetic tunnel junctions (MTJs) has been investigated for annealing between 190 and 370°C. The TMR shows a maximum value of 215% at an annealing temperature of 330°C. A strong sensitivity of the TMR and the exchange bias of the pinned ferromagnetic layers on the annealing temperature are observed. Depending on sensor application requirements, the MTJ can be optimized either for stability and pinning strength or for a high TMR signal by choosing the appropriate annealing temperature. The switching mechanism of the ferromagnetic layers in the MTJ and the influence of the annealing on the layer properties,…
Isothermal relaxation of discommensurations in K2ZnCl4
1994
At the incommensurate-ferroelectric transition temperature T c of K 2 ZnCl 4 , the dielectric susceptibility contains an anomalous contribution both above and below T c . Previous quasi-static dielectric measurements and hysteresis loops demonstrated that this anomalous part arises from the peculiar dynamics of discommensurations. We have used isothermal dielectric measurements to get some insight into the long time dynamics of these discommensurations. We have found that the characteristic relaxation times τ are of the order of 10 4 s in the incommensurate and in the ferroelectric phase. Even more unusual is a non-monotonous relaxation which is observed in a restricted temperature range ab…
EBSD, XRD and SRS characterization of a casting Al-7wt%Si alloy processed by equal channel angular extrusion: Dislocation density evaluation
2019
Abstract Aluminum‑silicon (Al Si) alloys of high silicon contents are composite materials; they are used whenever high casting properties are required. They are slightly ductile below 8wt%Si. An increase in ductility can be obtained by refining Si-crystals in elaboration or by a further hot working. In the present work, an Al-7wt%Si alloy was processed by Equal Channel Angular Extrusion (ECAE) at temperatures 20 °C and 160 °C up to three passes. The die was formed by two cylindrical channels with characteristic angles Φ = 110° and Ψ = 0. EBSD, X ray diffraction (XRD) and Strain Rate Sensitivity (SRS) were used to characterize the microstructure and the mechanical properties. High levels of …
High temperature oxidation of Mg2(Si-Sn)
2016
Abstract High temperature oxidation of Mg 2 Si 1- x Sn x alloys ( x = 0.1 ⿿ 0.6) has been investigated. The oxidation rate was slow for temperatures below 430 °C. In the temperature range between 430⿿500 °C all the alloys exhibited breakaway oxidation. The onset temperature of the breakaway region in general decreased with increasing level of Sn in the alloy. The breakaway behavior is explained by a combination of the formation of a non-protective MgO layer and the formation of Sn-rich liquid at the interface between the oxide and Mg depleted Mg 2 Sn.
Structural, microstructural and dielectric studies in multiferroic LaSrNiO4-δ prepared by mechanical milling method
2016
Abstract The solid solution LaSrNiO 4-δ has been successfully prepared by a rapid method combining mechanical milling and heat treatment. The structure and microstructure transformations were characterized by X-ray powder diffraction, scanning and transmission electron microscopy. The dielectric property was also investigated. After 10 h of milling and 8 h of heat treatment at 1300 °C, X-ray diffraction analysis revealed LaSrNiO 4-δ single phase, exhibiting tetragonal structure with space group of I4/mmm. This result was confirmed by using the ED pattern for sample using the [001] orientation. The corresponding lattice images show the compound to be well ordered, indicating the absence of s…