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Seminars & Lectures

* TITLE

Significant enhancement of critical current density and effective pinning centers in MgB2 with nano-SiC, Si and C addition

* SPEAKERS

Name	Affiliation	E-mail
Prof. X. L. Wang

* HOST(Applicant)

Name	Affiliation	E-mail
-

* DATE / TIME

2003-06-28, 11:00 am

* PLACE

포항공대 공학 3동

* ABSTRACT

Institute for Superconducting and Electronic Materials,
University of Wollongong, Northfields Ave. NSW, 2552,
Australia

Polycrystalline MgB2 samples with additions of 0-10 wt % nano-
powders of SiC, Si, and C, were prepared by an in-situ
reaction process. The phases, microstructures, and flux
pinning were characterized by XRD, TEM, and magnetic
measurements. It was observed that the samples doped with
nano-sized SiC have best pinning performance, while nano-Si
or nano-C powders showed a similar improved field dependence
of the critical current over a wide temperature range
compared with both undoped samples and samples with coarse
SiC and Si powders. Both magnetic and transport Jc were as
high as 3000-40000 A/cm2 in 8 T at 5 K, one or two orders of
magnitude higher than for these nano-particle added MgB2. Tc
only dropped 2 K and remained unchanged with further doping
level for these nano-particle doping. X-ray diffraction
results indicated that Si and SiC had reacted with Mg to
form Mg2Si. We also found that a very short-time sintering (3
min) at 900 oC heat treated samples exhibited high Jc values
of more than 1 MA/cm2 at 20 K in zero field with enhanced
pinning at high fields, but without forming Mg2Si. The
neutron diffraction and Rietveld analysis indicated that no
evidence of Si doping into the lattice in the Si doped MgB2
samples. Nano-particle inclusions, such as Mg2Si,
precipitates of MgO, unreacted nano-particles observed using
TEM are proposed to be responsible for the enhancement of
flux pinning in high fields.

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