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Amorphization and dynamic annealing of hexagonal SiC upon heavy-ion irradiation: Effects on swelling and mechanical properties

Abstract : Structural, mechanical, and dimensional evolutions of silicon carbide (SiC) induced by heavy-ion irradiations are studied by means of Rutherford backscattering spectrometry and channeling (RBS/C), nanoindentation, and surface profilometry measurements. 4H- and 6H-SiC single crystals were irradiated with 4 MeV Au(2+) and 4 MeV Xe(+) ions at room temperature (RT) or 400 degrees C. Using a Monte Carlo program to simulate the RBS/C spectra (MCCHASY code), we find that Au ion irradiation at RT induces a total silicon sublattice disorder related to full amorphization at a dose of about 0.4 displacement per atom (dpa). A two-step damage process is found on the basis of the disordered fractions deduced from RBS/C data. Complete amorphization cannot be reached upon both Au and Xe ion irradiations at 400 degrees C up to about 26 dpa because of the dynamic annealing of defects. When complete amorphization is reached at RT, the Young's modulus and Berkovich hardness of irradiated 6H-SiC samples are lower by, respectively, 40% and 45% than those of the virgin crystals. The out-of-plane expansion measured by surface profilometry increases versus irradiation dose and the saturation value measured in the completely amorphous layer (normalized to the ion projected range) is close to 25%. We show that the modifications of the macroscopic properties are mainly due to the amorphization of the material. The macroscopic elasticity constants and dimensional properties are predicted for a composite material made of crystalline matrix containing dispersed amorphous inclusions using simple analytical homogenization models. Voigt's model seems to give the best approximation for disordered fractions larger than 20% in the second step of the damage process.
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Submitted on : Tuesday, February 28, 2012 - 3:14:50 PM
Last modification on : Wednesday, October 14, 2020 - 4:01:57 AM

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X. Kerbiriou, J. M. Costantini, M. Sauzay, S. Sorieul, L. Thome, et al.. Amorphization and dynamic annealing of hexagonal SiC upon heavy-ion irradiation: Effects on swelling and mechanical properties. Journal of Applied Physics, American Institute of Physics, 2009, 105, pp.073513. ⟨10.1063/1.3103771⟩. ⟨in2p3-00674943⟩

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