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Thermomechanical Processing of High T c Superconducting Wire

Thermomechanical Processing of High T c Superconducting Wire. Super BSCCO Family C. Bjelkengren B. Cooper Y. King S. Maltas. Superconductivity Review. High Tc Superconduction originates from crystal structure Highly anisotropic (superconduction along Cu-O planes)

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Thermomechanical Processing of High T c Superconducting Wire

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  1. Thermomechanical Processing of High Tc Superconducting Wire Super BSCCO Family C. Bjelkengren B. Cooper Y. King S. Maltas

  2. Superconductivity Review • High Tc Superconduction originates from crystal structure • Highly anisotropic (superconduction along Cu-O planes) • Maintain grain/Cu-O plane alignment to maximize superconduction • Cu3+ valence states lead to partly filled energy bands • Oxidation to Cu3+ leads to p-type conductivity • Weak localization of valence electrons (low ionic character) • Alkaline and rare earth metals act as charge reservoirs Super BSCCO Family 2

  3. Basic Plan and Time Line • Improve the superconductivity through various thermomechanical processes to align grains and Cu-O planes • Week 1-3: Characterization of BSCCO Tape • Week 4-8: Investigation of Thermomechanical Processes • Week 9-14: Improving Superconductivity/Working on Prototype Super BSCCO Family 3

  4. Weeks 1-3 • Characterization of BSCCO Tape • Preparation of Samples: long/short transverse, filet • Light Microscopy: structural observations • Scanning Electron Microscopy: qualitative microstructural observations • Differential Scanning Calorimetery: phase transition identification • Critical Current Measurement: initial property characterization • X-ray Analysis: Lotgering factor - quantitatively measures texture by the intensity of the 2 peaks where 0=completely random and 1=completely textured Super BSCCO Family 4

  5. Sample Preparation • Characterization of BSCCO Tape • Preparation of Samples in Epoxy: • Short transverse |||||| • Long transverse |||||| • Filet |||||| • Polished to expose BSSCO . Super BSCCO Family 5

  6. Samples: Short Transverse Cut Sample in Epoxy and Coated in Gold (for SEM) Long Transverse Cut Sample in Epoxy and Coated in Gold (for SEM) Filet Cut Sample in Epoxy Super BSCCO Family 6

  7. Light Microscopy: • Structural observations ST 165x ST 330x Super BSCCO Family 7

  8. Light Microscopy: • Structural observations LT 660x Fillet 165x Super BSCCO Family 8

  9. Scanning Electron Microscopy • Qualitative Microstructural Observations ST 420x LT 420x Super BSCCO Family 9

  10. Differential Scanning Calorimetery • Phase Transition Identification 200 deg C to 600 deg C @ 20 C/min -170 deg C to 300 deg C @ 20 C/min Super BSCCO Family 10

  11. Work Today • Critical Current Measurement: initial property characterization • Setup Built and Ready for Testing • X-ray Analysis: Lotgering factor - quantitatively measures texture by the intensity of the 2 peaks where 0=completely random and 1=completely textured • Samples Polished and Ready for Testing Super BSCCO Family 11

  12. In the Next Few Weeks… • Investigation effects of thermomechanical processes on superconductivity • Cold Deformation: rolling, suspend under tension • Heat Treatment: 150 – 800 oC • Uniaxial Hot Deformation • Hot Isotactic Pressing • Directional Graingrowth: temperature gradient Super BSCCO Family 12

  13. Improving Superconductivity • Improving Superconductivity • Defined Processing Sequence • Determine Optimal Processing Variables: T, t, P • Measure of Success Ic, x-ray, SEM • Quantitative: Ic = 150 kA, Improve Lotgering Factor • Qualitative: SEM Super BSCCO Family 13

  14. Areas of Further Research • Research Thermomechanical Processes • Research Prototype Ideas • Locate Resource Facilities • Cold Deformation • Heat Treatment • Uniaxial Hot Deformation • Hot Isotactic Pressing • Directional Graingrowth Super BSCCO Family 14

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