Thermomechanical Processing of High Tc Superconducting Wire

Super BSCCO Family

C. BjelkengrenB. CooperY. KingS. Maltas

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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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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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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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Sample Preparation Characterization of BSCCO Tape

Preparation of Samples in Epoxy: Short transverse ||||||

Long transverse ||||||

Filet ||||||

Polished to expose BSSCO

.

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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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Light Microscopy: Structural observations

ST 165x ST 330x

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Light Microscopy: Structural observations

LT 660x Fillet 165x

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Scanning Electron Microscopy Qualitative Microstructural Observations

ST 420x LT 420x

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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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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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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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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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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