Thermomechanical Processing of High T c Superconducting Wire
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Transcript of Thermomechanical Processing of High T c Superconducting Wire
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Thermomechanical Processing of High Tc Superconducting Wire
Super BSCCO Family
C. BjelkengrenB. CooperY. KingS. Maltas
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Super BSCCO Family2
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
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Super BSCCO Family3
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
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Super BSCCO Family4
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
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Super BSCCO Family5
Sample Preparation Characterization of BSCCO Tape
Preparation of Samples in Epoxy: Short transverse ||||||
Long transverse ||||||
Filet ||||||
Polished to expose BSSCO
.
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Super BSCCO Family6
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
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Super BSCCO Family7
Light Microscopy: Structural observations
ST 165x ST 330x
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Super BSCCO Family8
Light Microscopy: Structural observations
LT 660x Fillet 165x
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Super BSCCO Family9
Scanning Electron Microscopy Qualitative Microstructural Observations
ST 420x LT 420x
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Super BSCCO Family10
Differential Scanning Calorimetery Phase Transition Identification
-170 deg C to 300 deg C @ 20 C/min 200 deg C to 600 deg C @ 20 C/min
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Super BSCCO Family11
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
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Super BSCCO Family12
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
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Super BSCCO Family13
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
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Super BSCCO Family14
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