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Title: MAGNESIUM PRECIPITATION AND DIFUSSION IN Mg+ ION IMPLANTED SILICON CARBIDE

As a candidate material for fusion reactor applications, silicon carbide (SiC) undergoes transmutation reactions under high-energy neutron irradiation with magnesium as the major metallic transmutant; the others include aluminum, beryllium and phosphorus in addition to helium and hydrogen gaseous species. Calculations by Sawan et al. predict that at a dose of ~100 dpa (displacements per atom), there is ~0.5 at.% Mg generated in SiC. The impact of these transmutants on SiC structural stability is currently unknown. This study uses ion implantation to introduce Mg into SiC. Multiaxial ion-channeling analysis of the as-produced damage state indicates a lower dechanneling yield observed along the <100> axis. The microstructure of the annealed sample was examined using high-resolution scanning transmission electron microscopy. The results show a high concentration of likely non-faulted tetrahedral voids and possible stacking fault tetrahedra near the damage peak. In addition to lattice distortion, dislocations and intrinsic and extrinsic stacking faults are also observed. Magnesium in 3C–SiC prefers to substitute for Si and it forms precipitates of cubic Mg2Si and tetragonal MgC2. The diffusion coefficient of Mg in 3C–SiC single crystal at 1573 K has been determined to be 3.8 ± 0.4E-19 m2/s.
Authors:
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Publication Date:
OSTI Identifier:
1179511
Report Number(s):
PNNL-SA-107486
48707; 44713; AT2030110
DOE Contract Number:
AC05-76RL01830
Resource Type:
Book
Resource Relation:
Related Information: FUSION MATERIALS SEMIANNUAL PROGRESS REPORT FOR THE PERIOD ENDING December 31, 2014, DOE-ER-0313/57:85-86
Publisher:
PJ Pappano; Oak Ridge National Laboratory, Oak Ridge, TN, United States(US).
Research Org:
Pacific Northwest National Laboratory (PNNL), Richland, WA (US), Environmental Molecular Sciences Laboratory (EMSL)
Sponsoring Org:
USDOE
Country of Publication:
United States
Language:
English
Subject:
Mg precipitation; diffusion; ion implantation; SiC; Environmental Molecular Sciences Laboratory