Ph.D. Student (alumnus)

Synthesis of superconducting magnesium diboride (MgB2) composites.

Email: john.defouw(@gmail.com)

B.S., Materials Science and Engineering, Purdue University

Originally from Grand Rapids, Michigan, I came to Northwestern University and the Dunand Research Group with an undergraduate degree (BS) in Materials Science and Engineering from Purdue University in West Lafayette, Indiana. At Purdue, I was also a Co-Op student working for a total of 24 months in research and development with a supplier in the automotive industry and did a group senior design project on the heat treatment of cast Ni-based superalloys. I completed my Ph.D. thesis work on the synthesis of superconducting magnesium diboride (MgB2) composites. I also worked on the synthesis of Ni-based foams and bulk metallic glass foams by infiltration of a removable salt pattern.

Magnesium diboride is a superconductor with a critical temperature around 39 K. While this is not as high as the high-temperature cuprate superconductors (Tc well above 100 K) it is higher than other intermetallic superconductors such as Nb3Sn that is used in magnetic resonance imaging (MRI) components. Wires of MgB2 would allow practical application near 20 K, which can be achieved with conventional refrigeration techniques and would not require the expensive liquid He that Nb3Sn requires. However, MgB2 is a brittle ceramic and wires cannot be drawn as with a ductile metal. For this reason, practical wires of MgB2 must be in combination with a ductile metal phase. We study the synthesis of MgB2 in situ both for liquid metal infiltration (reaction of commercial B fibers within liquid Mg to form a Mg/MgB2 fiber composite after solidification) and Powder-In-Tube wire making techniques (MgB2 or Mg + B powder is drawn within a metallic tube to produce a metal wire with MgB2 core).

Publications

1. Marcus L. Young, John DeFouw, Jon D. Almer, Dean R. Haeffner, and David C. Dunand: "Load Partitioning during Compressive Loading of a Mg/MgB2 Composite", accepted for publication in Acta Materialia 2007.
2. Alan Brothers, Richard Scheunemann, John DeFouw, David Dunand. “Processing and Structure of Open-Celled Amorphous Metal Foams.” Scripta Materialia 52 335 2005.
3. Alan Brothers, Richard Scheunemann, John DeFouw, David Dunand. “Processing and Structure of Open-Celled Amorphous Metal Foams.” Scripta Materialia 52 335 2005.
4. James V. Marzik, Raymond J. Suplinskas, William J. Croft, Warren J. MoberlyChan, John D. DeFouw, and David C. Dunand. “The Effect of Dopant Additions on the Microstructure of Boron Fibers Before and After Reaction to MgB2.” Materials Research Society Symposium Proceedings 848 FF6.2.1 2005.
5. John DeFouw and David Dunand. “In situ synthesis of superconducting MgB2 fibers within a magnesium matrix.” Applied Physics Letters 83 120 2003.