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This page is under construction
This page lists a few suggested research projects meant for
bachelor, master or other short term projects. Their size and
scope can be adapted according to the specific project type.
Please note that there is no grant associated to these projects.
If you are a student registered in a foreign institution and have
the possibility to apply for a grant (ERASMUS for example), you
will also be very welcome in our laboratory. In exceptional cases,
we may provide limited financial help but we do unfortunately not
have funding for extended support.
If you are interested in any of those projects, please do not
hesitate to contact Dr. Jean-Claude Grivel for further information.
jean@risoe.dtu.dk
REBa2Cu3O7 coated conductors
Bi2223 and Bi2212 tapes
In Bi2223 tapes as well as bulk ceramic samples, a significant porosity develops during reaction as an intrinsic consequence of the formation mechanism of the compound. This drawback sets severe limitations to the critical current densities achievable in the samples and necessitates additional pressing treatments to obtain dense ceramics. One possible way to circumvent this problem is to make use of sintering aids in the form of minute amounts (0.2% - 1%) of an additive, which can promote the formation of a liquid phase and prevent expansion of the ceramic. CaF
2
for example was found to result in significant improvements. Other potential sintering aids should be tested both in tapes and in bulk samples.Techniques: Wire manufacture by Powder-in-Tube method, x-ray diffraction (maybe synchrotron), electron microscopy, differential scanning calorimetry, dilatometry, T
c
and critical current measurements.
MgB2 wires
In MgB
2
wires, significant improvements of the critical current density can be obtained by reducing the size of the MgB
2
particles. Small particles can be formed when the starting reagents include nanometer sized B powder, but grain growth during reaction with Mg must be suppressed as much as possible. One strategy is to lower the MgB
2
formation temperature by adding small amounts of additives forming low temperature liquid phases by reacting first with Mg. Interesting results were obtained with Ag and Cu in particular. In view of further improvements, we propose to test simultaneous additions of two or more elements forming low temperature eutectic melts.
Techniques: Wire manufacture by Powder-in-Tube method, x-ray diffraction (maybe synchrotron), electron microscopy, differential scanning calorimetry, T
c
and critical current measurements.
While carbon doping has been shown to improve the performance of MgB
2
wires in magnetic fields, it also decreases the critical temperature of the phase. Few other elements can be substituted into MgB
2
and have been shown to result in interesting improvements in bulk samples. However, not many of these alternative doping strategies have been tested in wires and their effect on transport critical currents is poorly known. We suggest performing systematic investigations on promising doping elements.
Techniques: Wire manufacture by Powder-in-Tube method, x-ray diffraction (maybe synchrotron), electron microscopy, differential scanning calorimetry, T
c
and critical current measurements.
Other superconducting materials
High temperature superconducting wires and tapes have been nearly exclusively developed with the compounds MgB
2
, Bi
2
Sr
2
CaCu
2
O
8
, (Bi,Pb)
2
Sr
2
Ca
2
Cu
3
O
10
, YBa
2
Cu
3
O
7
and the highest T
c
materials based on Tl or Hg. There are however many other superconducting oxides with intermediate transition temperatures that may be of high interest for applications at temperatures lower than 77K. In fact, the performance of nowadays HTS wires and tapes may not be good enough for working safely at this temperature. We are interested in testing the potential of other HTS materials for applications in the form of wires or tapes in the 20K – 60K range. Such development work requires fundamental investigations of the critical current density of candidate compounds and manufacture of short test wires and tapes. There are numerous possibilities for defining research projects in this new direction of research.
New materials
There are still many unknown ternary phase diagrams including CuO and SrO (CaO or BaO) and transition element oxides. Establishing the phase equilibria in one of them would be an interesting basic project on materials science with the exiting possibility of discovering new compounds.
In this project, you will be preparing polycrystalline samples by means of a solid-state technique, use x-ray diffraction for phase analysis and lattice parameter diffraction as well as scanning electron microscopy and energy dispersive x-ray analysis for determination of compositions.
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