Effect of Starting Materials and Present State of Cold Densified MgB 2 wires for Industrial Scale-up M.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

Supercond. Sci. Technol. 23 (2010)

99% nano size amorphous with excess Mg 99% nano size amorphous stoichiometric 97% crystalline

Supercond. Sci. Technol. 23 (2010) % nano size amorphous 97% crystalline with high annealing temp 97% crystalline with low annealing temp

JOURNAL OF APPLIED PHYSICS 105, (2009)

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) ]

HIP0.2 GPaTapesSerquis et al., 2003 Metallic anvils> 0.2 GPa Bulk samplesPrikhna et al., 2008 Hot pressing0.1 GPaTapesKumakura et al., 2008 Hot Pressing 0.1 GPaTapesYamada et al., 2006 Cold Pressing (before reaction) P = 0.1 GpaBulk samples Matsushita (2008): little effect P > 1 GPa Wires and Tapes Present work: Higher mass density (Connectivity) Higher J c Reduced electrical resistivity Hot Pressing (during reaction) Application of High Pressures on in situ MgB 2

Binary MgB 2 : 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 MgB 2 : Higher mass density due to volume contraction

Binary MgB 2 : CHPD improves grain connectivity Hossain MSA, Supercond. Sci. Technol. 22 (2009) (7pp)

0 GPa1.5 GPa A. B. Binary 18-filament MgB 2 wire: CHPD applied

J c vs. B at 4.2, 20 and 25 K for 18-filament binary MgB 2 wires densified at 1.5 Gpa on short and15cm long samples 2 nd International Forum, ISEM, UOW – 28/03/2011 Hossain MSA, Supercond. Sci. Technol. 26(2011) (7pp)

MgB 2 wires, doped with 10 wt.% C 4 H 6 O 5 NbTi: J c = 1 x 10 5 A/cm 2 at 8T/4.2K compression Almost isotropic behavior Hossain MSA, Supercond. Sci. Technol. 22 (2009) (8pp)

OSU measurement: MgB 2 wires, after 1.8 Gpa, Alloyed with 10 wt.% C 4 H 6 O 5 At 20K, Jc = 10^4 A/cm 2 at >7T!!!

Comparison of various additives used in MgB2 wires after CHPD

CHPD improves the homogeneity of J c in the s/c layer MgB C/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 MgB 2 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 MgB 2 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 MgB 2 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 J c in binary and alloyed MgB 2 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 MgB 2 wires with practically isotropic properties exhibited the highest value of J c reported so far: B(10 4 ) = 13.4 // / ┴ T at 4.2K. B(10 4 ) = 7.1 // /6.7 ┴ T at 20K CHPD has the potential for the production of long length MgB 2 wires

Applied SuperconductivityEnergy Storage Group Spintronic and Electronic Materials Group Thin Film Technology Group Terahertz Science, Solid State Physics Group Nano Structured Materials Advanced Photovoltaic Materials