Mechanisms and kinetics of MgB2 synthesis from boron fibers

John D. DeFouw; David C. Dunand

doi:10.1016/j.actamat.2008.07.049

Mechanisms and kinetics of MgB₂ synthesis from boron fibers

John D. DeFouw^*, David C. Dunand

^*Corresponding author for this work

Materials Science and Engineering

Research output: Contribution to journal › Article › peer-review

20 Scopus citations

Abstract

Superconducting MgB₂ fibers were synthesized through the reaction of liquid magnesium with 140 μm diameter boron fibers. Fiber reaction occurs by two concurrent mechanisms. First, concentric MgB₂, MgB₄ and MgB₇ shells grow radially into the B fibers. Diffusion modeling provides rate constants and effective diffusion coefficients for the borides and their activation energies. Second, radial cracks form in the MgB₄ or MgB₇ shells, allowing for Mg ingress into the fibers and diffusional growth of MgB₂ wedges in the radial and circumferential directions. Combining both shell and wedge MgB₂ growth mechanisms into a single model provides predictions of overall MgB₂ reaction kinetics as a function of time and temperature, which are in good agreement with in situ X-ray diffraction measurements performed at 885-1025 °C.

Original language	English (US)
Pages (from-to)	5751-5763
Number of pages	13
Journal	Acta Materialia
Volume	56
Issue number	19
DOIs	https://doi.org/10.1016/j.actamat.2008.07.049
State	Published - Nov 2008

Funding

This work was supported by the US National Science Foundation through Grant No. DMR-0319051. The authors thank Dr. J. Marzik of Specialty Materials, Inc. for providing boron fibers and Drs. J. Quintana, Q. Ma and D. Keane for help in performing the diffraction experiments at the DuPont-Northwestern-Dow Collaborative Access Team (DND-CAT). DND-CAT is supported by E.I. DuPont de Nemours & Co., The Dow Chemical Company and the State of Illinois and is located at Sector 5 of the Advanced Photon Source which is supported by the US Department of Energy under Contract No. DE-AC02-06CH11357.

Keywords

Chemical synthesis
Magnesium diboride
Superconductor
Theory and modeling (kinetics, transport, diffusion)
X-ray diffraction

ASJC Scopus subject areas

Electronic, Optical and Magnetic Materials
Ceramics and Composites
Polymers and Plastics
Metals and Alloys

Access to Document

10.1016/j.actamat.2008.07.049

Cite this

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title = "Mechanisms and kinetics of MgB2 synthesis from boron fibers",

abstract = "Superconducting MgB2 fibers were synthesized through the reaction of liquid magnesium with 140 μm diameter boron fibers. Fiber reaction occurs by two concurrent mechanisms. First, concentric MgB2, MgB4 and MgB7 shells grow radially into the B fibers. Diffusion modeling provides rate constants and effective diffusion coefficients for the borides and their activation energies. Second, radial cracks form in the MgB4 or MgB7 shells, allowing for Mg ingress into the fibers and diffusional growth of MgB2 wedges in the radial and circumferential directions. Combining both shell and wedge MgB2 growth mechanisms into a single model provides predictions of overall MgB2 reaction kinetics as a function of time and temperature, which are in good agreement with in situ X-ray diffraction measurements performed at 885-1025 °C.",

keywords = "Chemical synthesis, Magnesium diboride, Superconductor, Theory and modeling (kinetics, transport, diffusion), X-ray diffraction",

author = "DeFouw, {John D.} and Dunand, {David C.}",

note = "Funding Information: This work was supported by the US National Science Foundation through Grant No. DMR-0319051. The authors thank Dr. J. Marzik of Specialty Materials, Inc. for providing boron fibers and Drs. J. Quintana, Q. Ma and D. Keane for help in performing the diffraction experiments at the DuPont-Northwestern-Dow Collaborative Access Team (DND-CAT). DND-CAT is supported by E.I. DuPont de Nemours & Co., The Dow Chemical Company and the State of Illinois and is located at Sector 5 of the Advanced Photon Source which is supported by the US Department of Energy under Contract No. DE-AC02-06CH11357. ",

year = "2008",

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AU - Dunand, David C.

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N2 - Superconducting MgB2 fibers were synthesized through the reaction of liquid magnesium with 140 μm diameter boron fibers. Fiber reaction occurs by two concurrent mechanisms. First, concentric MgB2, MgB4 and MgB7 shells grow radially into the B fibers. Diffusion modeling provides rate constants and effective diffusion coefficients for the borides and their activation energies. Second, radial cracks form in the MgB4 or MgB7 shells, allowing for Mg ingress into the fibers and diffusional growth of MgB2 wedges in the radial and circumferential directions. Combining both shell and wedge MgB2 growth mechanisms into a single model provides predictions of overall MgB2 reaction kinetics as a function of time and temperature, which are in good agreement with in situ X-ray diffraction measurements performed at 885-1025 °C.

AB - Superconducting MgB2 fibers were synthesized through the reaction of liquid magnesium with 140 μm diameter boron fibers. Fiber reaction occurs by two concurrent mechanisms. First, concentric MgB2, MgB4 and MgB7 shells grow radially into the B fibers. Diffusion modeling provides rate constants and effective diffusion coefficients for the borides and their activation energies. Second, radial cracks form in the MgB4 or MgB7 shells, allowing for Mg ingress into the fibers and diffusional growth of MgB2 wedges in the radial and circumferential directions. Combining both shell and wedge MgB2 growth mechanisms into a single model provides predictions of overall MgB2 reaction kinetics as a function of time and temperature, which are in good agreement with in situ X-ray diffraction measurements performed at 885-1025 °C.

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KW - X-ray diffraction

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