Effect of Starting Materials and Present
State of Cold Densified MgB2 wires for
Industrial Scale-upM.S.A. Hossain, C. Senatore, R. Flükiger, M. Tomsic, S. X.
Dou
Superconductivity Symposium, Izmir– 05/07/2011
Outline
Superconductivity Symposium, Izmir– 05/07/2011
Superconductivity Symposium, Izmir– 05/07/2011
Superconductivity Symposium, Izmir– 05/07/2011
Supercond. Sci. Technol. 23 (2010) 075014
Supercond. Sci. Technol. 23 (2010) 075014
99% nano size amorphous with excess Mg
99% nano size amorphous stoichiometric
97% crystalline
Supercond. Sci. Technol. 23 (2010) 075014
99% nano size amorphous
97% crystalline with high annealing temp
97% crystalline with low annealing temp
JOURNAL OF APPLIED PHYSICS 105, 103913 (2009)
JOURNAL OF APPLIED PHYSICS 105, 103913 (2009)
Superconductivity Symposium, Izmir– 05/07/2011
Superconductivity Symposium, Izmir– 05/07/2011
2 ways to improve the properties of MgB2 superconductors :
1.Intrinsic (homogeneous dopant induced Hc2 enhancement)2.Extrinsic (reduced porosity i.e better connectivity between grains)
Collings et al. Sust 21 (2008) 103001]
HIP 0.2 GPa Tapes Serquis et al., 2003Metallic anvils > 0.2 GPa Bulk samples Prikhna et al., 2008Hot pressing 0.1 GPa Tapes Kumakura et al., 2008 Hot Pressing 0.1 GPa Tapes Yamada et al., 2006
Cold Pressing (before reaction)
P = 0.1 Gpa Bulk samples Matsushita (2008): little effect
P > 1 GPa Wires and Tapes Present work:
Higher mass density (Connectivity)Higher Jc
Reduced electrical resistivity
Hot Pressing (during reaction)
Application of High Pressures on in situ MgB2
Binary MgB2 : Applying Pressures from 4 sides on square wires.
The directional elongated morphology of the Mg is always visible in cold deformed Mg+B powder mixtures
Drawn to a square cross section After cold densification at 2 GPa 1.0 mm 1.0 mm
Binary MgB2 : Higher mass density due to volume contraction
Binary MgB2 : CHPD improves grain connectivity
Hossain MSA, Supercond. Sci. Technol. 22 (2009) 085002 (7pp)
0 GPa 1.5 GPa
A.
B.
Binary 18-filament MgB2 wire: CHPD applied
Jc vs. B at 4.2, 20 and 25 K for 18-filament binary MgB2 wires densified at 1.5 Gpa on short and15cm long samples
2nd International Forum, ISEM, UOW – 28/03/2011
Hossain MSA, Supercond. Sci. Technol. 26(2011) 085002 (7pp)
MgB2 wires, doped with 10 wt.% C4H6O5
6 7 8 9 10 11 12 13 14 15 16 17 18 19 20102
103
104
105
12.9 T
13.4 T
Square Wire (0 GPa) J
c// (2 GPa)
Jc (2 GPa)
B (T)
J c( A
/cm
2 )
600 C/4hrsC4H6O5 additive
//
NbTi: Jc = 1 x 105 A/cm2 at 8T/4.2Kcompression
Almost isotropic behavior
Hossain MSA, Supercond. Sci. Technol. 22 (2009) 095004 (8pp)
René Flükiger-1.8 GPa- edge on
Magnetic Field, B, T
0 2 4 6 8 10 12 14
Cri
tica
l Cur
rent
, Jc,
A/c
m2
102
103
104
105
106
10 K12.5 15.0 K 17.5 K20.0 K 22.5 K 25.0 K27.5 K 30.0 K32.5 K
OSU measurement: MgB2 wires, after 1.8 Gpa, Alloyed with 10 wt.% C4H6O5
At 20K, Jc = 10^4 A/cm2 at >7T!!!
Comparison of various additives used in MgB2 wires after CHPD
CHPD improves the homogeneity of Jc in the s/c layer
MgB2 - 650C/1hMgB2 - 650C/1h
… as a consequence, also the n value of I-V curve is increased
Accepted by IEEE transactions on Applied Superconductivity
n-factor improves in both binary and alloyed MgB2 sample after CHPD:
Accepted by IEEE transactions on Applied Superconductivity
First test on densification of longer wire lengths (1 meter) by means of an automatic press/release/advance mechanism
Accepted by IEEE transactions on Applied Superconductivity
Industrially Potential Isotropic wires
Still lot to do…….
The further improvement of MgB2 conductors involves the following main factors,
i) the availability of amorphous, high purity Boron powder with sizes in the 100 nm range,
ii) the optimization of mass density in MgB2 filaments, by improved densification methods,
iii) the enhancement of the filling factor, which is at present higher for in situ wires than for IMD processed wires, and
iv) further studies on cold deformation are needed in order to obtain wires with smaller filament diameters for reducing the losses in AC applications.
Summary
Cold High Pressure Densification determines a strong
enhancement of Jc in binary and alloyed MgB2 wires due to
higher mass density inside the filament.
Resistivity decreases, resulting in an increased current-carrying cross section
Homogeneity is improved and thus the n value of I-V curve is increased
Square MgB2 wires with practically isotropic properties exhibited the highest value of Jc reported so far: B(104) = 13.4// / 12.95┴ T at 4.2K. B(104) = 7.1///6.7┴ T at 20K
CHPD has the potential for the production of long length MgB2 wires
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Nano Structured Materials
Advanced Photovoltaic Materials