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

Applied Superconductivity Energy Storage Group

Spintronic and Electronic Materials Group

Thin Film Technology Group

Terahertz Science, Solid State Physics Group

Nano Structured Materials

Advanced Photovoltaic Materials