MgB2 Composite Superconductors Made by Ex Situ and In Situ Process

2006 ◽  
Vol 47 ◽  
pp. 131-136 ◽  
Author(s):  
Pavol Kováč ◽  
I. Hušek ◽  
T. Melišek
Keyword(s):  
Current Density ◽  
Transport Current ◽  
Ex Situ ◽  
Boron Diffusion ◽  
Critical Temperatures ◽  
Mgb2 Wires ◽  
Composite Superconductors ◽  
Current Densities ◽  
Composite Wires

Generally, two basic routes called as in-situ and ex-situ process are used for composite MgB2 wires now. Mentioned processes have been used for making of single-core composite wires. The applied heat treatment parameters influence the microstructure of MgB2 phase, critical temperature and critical current density, but it has also decisive effect on the MgB2/metal reaction. It was found that the transport current densities are much more sensitive to the used sheath material than critical temperatures. The main factors limiting the transport current density are cracks introduced by deformation and porosity caused by the boron diffusion in ex-situ and in-situ wires, respectively.

Current densities of MgB2 wires by combined ex situ/in situ process

2009 ◽  
Vol 106 (1) ◽  
pp. 013910 ◽  
Author(s):  
P. Kováč ◽  
M. Reissner ◽  
T. Melišek ◽  
I. Hušek ◽  
S. Mohammad
Keyword(s):  
Ex Situ ◽  
Mgb2 Wires ◽  
Current Densities

scholarly journals Influence of Preparation Process on Microstructure, Critical Current Density and Tc of MgB2/Fe/Cu Wires

2007 ◽  
Vol 546-549 ◽  
pp. 2031-2034
Author(s):  
Y.F. Wu ◽  
G. Yan ◽  
J.S. Li ◽  
Y. Feng ◽  
Shao Kai Chen ◽  
...  
Keyword(s):  
Heat Treatment ◽  
Current Density ◽  
Rolling Process ◽  
High Energy ◽  
Transport Current ◽  
Post Heat Treatment ◽  
Mechanically Alloyed ◽  
Mgb2 Wires ◽  
Powder In Tube ◽  
Transport Current Density

The powder-in-tube MgB2 wires were prepared by high energy milling of Mg and B powder. The powder was not mechanically alloyed for 2h short milling time. However, the MgB2 grains in wires were very small (20~100nm) and resemble the dimple after post-heat treatment. The clear evidence for transcrystlline fracture was observed. It indicated that the grain connection was greatly improved and the fluxing pinning was significantly enhanced. Another point to view was no intermediate annealing during the whole rolling process. The influence of the post-heat treatment on the transport current density was studied. Despite the lower Tc of about 35K, the transport current density reached to 3×104A/cm2 at 15K and 3.5T for wires sintered at 700°C.

scholarly journals Importance of the pyrolysis for microstructure and superconducting properties of CSD-grown GdBa2Cu3O7−x-HfO2 nanocomposite films by the ex-situ approach

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Pablo Cayado ◽  
Hannes Rijckaert ◽  
Els Bruneel ◽  
Manuela Erbe ◽  
Jens Hänisch ◽  
...  
Keyword(s):  
Processing Parameters ◽  
Nanocomposite Films ◽  
Ex Situ ◽  
Superconducting Properties ◽  
Critical Temperatures ◽  
Solution Deposition ◽  
Nanoparticle Distribution ◽  
Current Densities ◽  
First Time ◽  
Lower Heating

Abstract For the first time, GdBa2Cu3O7−x nanocomposites were prepared by chemical solution deposition following the ex-situ approach. In particular, ~ 220 nm GdBa2Cu3O7−x-HfO2 (GdBCO-HfO2) nanocomposite films were fabricated starting from a colloidal solution of 5 mol% HfO2 nanoparticles. Hereby, one of the main challenges is to avoid the accumulation of the nanoparticles at the substrate interface during the pyrolysis, which would later prevent the epitaxial nucleation of the GdBCO grains. Therefore, the effect of pyrolysis processing parameters such as heating ramp and temperature on the homogeneity of the nanoparticle distribution has been investigated. By increasing the heating ramp to 300 °C/h and decreasing the final temperature to 300 °C, a more homogenous nanoparticle distribution was achieved. This translates into improved superconducting properties of the grown films reaching critical temperatures (Tc) of 94.5 K and self-field critical current densities ($${J}_{\mathrm{c}}^{\mathrm{sf}}$$ J c sf ) at 77 K of 2.1 MA/cm2 with respect to films pyrolyzed at higher temperatures or lower heating ramps.

Critical current density and pinning behaviour of mono-core MgB2 wires prepared by internal magnesium diffusion and in-situ powder-in-tube method

2014 ◽  
Vol 505 ◽  
pp. 39-43 ◽  
Author(s):  
Boris Brunner ◽  
Pavol Kováč ◽  
Michael Reissner ◽  
Imrich Hušek ◽  
Tibor Melišek ◽  
...  
Keyword(s):  
Critical Current Density ◽  
Critical Current ◽  
Current Density ◽  
Mgb2 Wires ◽  
Powder In Tube

scholarly journals Analytical Investigation of Fuel Cells by Using In Situ and Ex Situ Diagnostic Methods

2010 ◽  
Vol 638-642 ◽  
pp. 1125-1130
Author(s):  
Günter Schiller ◽  
Erich Gülzow ◽  
Mathias Schulze ◽  
Norbert Wagner ◽  
K. Andreas Friedrich
Keyword(s):  
Fuel Cells ◽  
Current Density ◽  
Printed Circuit Boards ◽  
Analytical Investigation ◽  
Diagnostic Methods ◽  
Electrochemical Methods ◽  
Measuring System ◽  
Ex Situ ◽  
German Aerospace

The study of the behaviour of fuel cells by using various in-situ and ex-situ diagnostic methods is a main topic at the German Aerospace Center (DLR). The degradation of cell components of polymer electrolyte fuel cells (PEFC, DMFC) and of solid oxide fuel cells (SOFC) are of special interest. For this purpose physical and electrochemical methods are used individually as well as in combination. In addition to routinely applied electrochemical methods different methods for locally resolved current density measurements by means of segmented cell technology and integrated temperature sensors have been developed. The latest development with segmented bipolar plates based on printed circuit boards (PCB) is used both in single PEFC cells and stacks. Furthermore, a measuring system for segmented SOFC cells has been developed allowing for the spatially resolved characterisation of cells in terms of current density/voltage characteristics, impedance spectroscopy data, operating temperature and gas composition. The paper summarises the capabilities at DLR with respect to the analysis of fuel cells’ behaviour and gives examples of analytical studies to discuss the potentials and limitations of the diagnostic methodology that is applied.

Electromigration Damage in Conductor Lines: Recent Progress in Microscopic Observation and Mechanistic Modelling

1994 ◽  
Vol 338 ◽  
Author(s):  
E. Arzt ◽  
O. Kraft ◽  
U.E. MÖckl
Keyword(s):  
Rational Design ◽  
Recent Progress ◽  
Ex Situ ◽  
Mechanistic Modelling ◽  
Stress Effects ◽  
Recent Developments ◽  
Current Densities ◽  
Damage Map ◽  
Shape Changes

ABSTRACTIn this paper an overview of recent developments in understanding electromigration damage mechanisms is given. Based on our detailed studies, both ex-situ and in-situ, of damage in unpassivated near-bamboo lines, we develop a theoretical electromigration damage map. It explains why “slit-like” failure becomes predominant for narrow lines and low current densities. The mechanism of slit formation is discussed in the light of new analytical and numerical simulations of pore shape changes, which take stress effects into account. Possible implications for the rational design of improved metallization alloys are suggested.

In-Situ and Ex-Situ Investigation of Lateral Current Density Variations in a PEM Fuel Cell With Serpentine Flow Field

2009 ◽  
Author(s):  
Andrew Higier ◽  
Hongtan Liu
Keyword(s):  
Fuel Cell ◽  
Flow Field ◽  
Contact Resistance ◽  
Current Density ◽  
Pem Fuel Cell ◽  
Gas Diffusion ◽  
Operating Conditions ◽  
Ex Situ ◽  
Serpentine Flow Field

One of the most common types of flow field designs used in proton exchange membrane (PEM) fuel cell is the serpentine flow field. It is used for its simplicity of design, its effectiveness in distributing reactants and its water removal capabilities. The knowledge about where current density is higher, under the land or the channel, is critical for flow field design and optimization. Yet, no direct measurement data are available for serpentine flow fields. In this study a fuel cell with a single channel serpentine flow field is used to separately measure the current density under the land and channel on the cathode. In this manner, a systematic study is conducted under a wide variety of conditions and a series of comparisons are made between land and channel current density. Results show that under most operating conditions, current density is higher under the land than that under the channel. However, at low voltage, a rapid drop off in current density occurs under the land due to concentration losses. In order to investigate the cause of the variations of current density under the land and channel and series of ex-situ and in-situ experiments were conducted. In the ex-situ portion of the study, the contact resistance between the gas diffusion electrode (GDE) and the graphite flow plate were measured using an ex-situ impedance spectroscopy technique. The values of the contact resistance under the channel were found to be larger than that under the land. This implies that the contact resistance under the land and channel vary greatly, likely due to variations in compression under different section of the flow field. These variations in turn cause current density variations under the land and channel.

Electromigration Reliability of Electroplated Gold Interconnects

2014 ◽  
Vol 1692 ◽  
Author(s):  
Steve H. Kilgore ◽  
Dieter K. Schroder
Keyword(s):  
Current Density ◽  
Open Circuit ◽  
Constant Current ◽  
Measured Temperature ◽  
Lifetime Distributions ◽  
Current Densities ◽  
Log Normal ◽  
Equipment Application ◽  
A Current

ABSTRACTThe electromigration lifetimes of a very large quantity of passivated electroplated Au interconnects were measured utilizing high-resolution in-situ resistance monitoring equipment. Application of moderate accelerated stress conditions with current density limited to 2 MA/cm2 and oven temperatures in the range of 300°C to 375°C prevented large Joule-heated temperature gradients and electrical overstress failures. A Joule-heated Au film temperature increase of 10°C on average was determined from measured temperature coefficients of resistance (TCRs). A failure criterion of 50% resistance degradation was selected to avoid thermal runaway and catastrophic open circuit failures. All Au lifetime distributions followed log-normal statistics. An activation energy of 0.80 ± 0.05 eV was measured from constant-current electromigration tests at multiple temperatures. A current density exponent of 1.91 ± 0.03 was extracted from multiple current densities at a single constant temperature.

Increased critical current density of in-situ MgB2 wires by Mg deficiency

2015 ◽  
Vol 510 ◽  
pp. 8-12 ◽  
Author(s):  
W. Häßler ◽  
C. Rodig ◽  
C. Damm ◽  
J. Scheiter ◽  
L. Schultz ◽  
...  
Keyword(s):  
Critical Current Density ◽  
Critical Current ◽  
Current Density ◽  
Mgb2 Wires ◽  
Mg Deficiency
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