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Progress in in situ MgB 2 wires after Cold High Pressure Densification (CHPD). R. Flükiger, M.S.A. Hossain and C. Senatore Dept. Appl. Physics (GAP), University Geneva, 1211 Geneva, Switzerland, and M. Rindfleisch Hyper Tech Columbus OH (USA).
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Progress in in situ MgB2 wires after Cold High Pressure Densification (CHPD) R. Flükiger, M.S.A. Hossain and C. Senatore Dept. Appl. Physics (GAP), University Geneva, 1211 Geneva, Switzerland, and M. Rindfleisch Hyper Tech Columbus OH (USA) IEA ExCo Stockhom, 19./21.5.2010
For industrial purposes, a method is needed where the wires would be pressed at the end of the deformation process, but before the reaction heat treatment: Cold High Pressure Densification (CHPD) IEA ExCo Stockhom, 19./21.5.2010
Enhancement of mass density in long MgB2wires Cold high pressure Densification Recently applied to tapes and wires Binary MgB2: R. Flükiger, M.S.A. Hossain, C. Senatore, SuST 22 (2009) 085002 Alloyed MgB2: M.S.A. Hossain, C. Senatore, R. Flükiger, M.A. Rindfleisch, M.J. Tomsic, J.H. Kim, S.X. Dou, SuST22 (2009) 095004 Highest values so far on square wires at 4.2K: B(104 A/cm2) = 13.8 T IEA ExCo Stockhom, 19./21.5.2010
Fe/ MgB2 filament at the border of a region pressed at 1.9 GPa (polished sample) IEA ExCo Stockhom, 19./21.5.2010
Binary Fe/MgB2 wire Compression 1.0 mm 1.0 mm Drawn to a square cross section After cold densification at 3 GPa IEA ExCo Stockhom, 19./21.5.2010
Right scale: relative mass density df of reacted MgB2 filaments Left scale: relative density dm of unreacted (Mg+B) mixture Highest relative mass density achievable in in situ wires: 80% IEA ExCo Stockhom, 19./21.5.2010
Determination of mass density in filaments is a very time consuming task. Microhardness, an indirect but very rapid method for estimating the mass density of MgB2 filaments ? IEA ExCo Stockhom, 19./21.5.2010
MgB2tapes alloyed with 10 wt.% malic acid (C4H6O5) Round C4H6O5 alloyed MgB2 wires for the present densification effects: from Hyper Tech Research Inc., Columbus, OH 43212, USA M.S.A.Hossain, C.Senatore, R.Flükiger, M.A.Rindfleisch, M.J.Tomsic, J.H.Kim ,S.X.Dou, SuST 22 (2009) 095004 IEA ExCo Stockhom, 19./21.5.2010
MgB2tapes alloyed with 10 wt.% malic acid (C4H6O5) At 4.2K: B(104)// = 13.2 T B(104)┴ = 12.1 T DBirr = + 3T 0.1 mV/cm IEA ExCo Stockhom, 19./21.5.2010
Cold Densification: No Effect of on Pinning Force fp(b ) does not change after CHPD IEA ExCo Stockhom, 19./21.5.2010
Resistance measurements and transition width After CHPD the cross section area is reduced Reduced electrical resistance: improved connectivity IEA ExCo Stockhom, 19./21.5.2010
Conclusions from Fe/MgB2 Tapes Densified at 1.48 GPa: * Jcenhanced by a factor 2 at 12 T/4.2K * Jc// = 104 A/cm2 at 4.2K: 13.2T * Anisotropy ratio unchanged: texture not influenced by pressure * Pinning properties unchanged * Better connectivity IEA ExCo Stockhom, 19./21.5.2010
Cold High Pressure Densification on MgB2 wires with square cross section IEA ExCo Stockhom, 19./21.5.2010
p = 1.5 GPa 0.1 mV/cm 1.0 mV/cm p = 0 GPa World’s best so far Monofilamentary MgB2 Wire C4H6O5 additions, 4h/600°C IEA ExCo Stockhom, 19./21.5.2010
Monofilamentary MgB2 Wire C4H6O5 additions, 4h/600°C IEA ExCo Stockhom, 19./21.5.2010
Exponential n factor n = 30 4.2 K IEA ExCo Stockhom, 19./21.5.2010
Sequential pressing: first step in direction of long MgB2 wire lengths IEA ExCo Stockhom, 19./21.5.2010
Sequential pressing: Overlapping pressure regions Total wire length: 15 cm MgB2 wires with malic acid additives IEA ExCo Stockhom, 19./21.5.2010
Sequential pressing: Overlapping pressure regions Total wire length: 15 cm MgB2 wires, with 10% SiC additive IEA ExCo Stockhom, 19./21.5.2010
Binary 19-filaments MgB2 wire from Hypertech after Densification IEA ExCo Stockhom, 19./21.5.2010
Conclusion: Sequential pressing with overlapping pressure regions yields the same Jc and nvalues as for short wire samples promising for industrial application of CHPD technique IEA ExCo Stockhom, 19./21.5.2010
Future development in view of longer wire lengths Prototype press at Unige Actually being modified for CHPD on long wire lengths (“sequential densification”, operational: July/August 2010) IEA ExCo Stockhom, 19./21.5.2010
Prototype of « sequential densification » wire IEA ExCo Stockhom, 19./21.5.2010
First prototype for sequential densification • of long MgB2 wires (laboratory use) • Pressing length = 40 mm • Sequence: 4.2 s • Expected densification rate: 10 - 30 m/h • (can be improved by a factor 10 in more • sophisticated industrial machines: > 1 km/day IEA ExCo Stockhom, 19./21.5.2010
Effects of Densification Better connectivity (lower electrical resistivity) Enhancement of Jc at a given field Where is the limit for Jc in MgB2 wires? IEA ExCo Stockhom, 19./21.5.2010
film Infiltration Cold Densification IEA ExCo Stockhom, 19./21.5.2010
Densification methods for long wires Presently: MgB2 Future developments: Hope for enhancement of Jc: Bi-2212 Nb3Sn, PIT, Or any other new powdermetallurgical superconductor
Conclusions • A new technique for MgB2 wires was developed in • Geneva: Cold High Pressure Densification (CHPD) • Very promising technique: Jc(4.2K) = 104 A/cm2 at 13.8 T • (world’s best 12.5 T); further enhancement expected • * Mechanism for enhancing Jc and Birr: percolation • Prototype apparatus for long wire lengths is developed • Enhancement of Jc by a factor of > 2 leads to a strong • reduction of the wire costs for a given project IEA ExCo Stockhom, 19./21.5.2010
