Irradiation-induced β to α SiC transformation at low temperature

Abstract

We observed that β-SiC, neutron irradiated to 9 dpa (displacements per atom) at ≈1440 °C, began transforming to α-SiC, with radiation-induced Frank dislocation loops serving as the apparent nucleation sites. 1440 °C is a far lower temperature than usual β → α phase transformations in SiC. SiC is considered for applications in advanced nuclear systems, as well as for electronic or spintronic applications requiring ion irradiation processing. β-SiC, preferred for nuclear applications, is metastable and undergoes a phase transformation at high temperatures (typically 2000 °C and above). Nuclear reactor concepts are not expected to reach the very high temperatures for thermal transformation. However, our results indicate incipient β → α phase transformation, in the form of small (~5–10 nm) pockets of α-SiC forming in the β matrix. In service transformation could degrade structural stability and fuel integrity for SiC-based materials operated in this regime. However, engineering this transformation deliberately using ion irradiation could enable new electronic applications.

Low‐temperature joining of SiC ceramics using NITE phase with Al2O3‐Ho2O3 additive

“…The absence of α-SiC was attributed to the limited phase transition from β-to α-SiC at relatively low temperature. 19 Reflections in Figure 1B-D indicated no obvious phase difference among these simulated surrogate samples. The relative density of the surrogate was measured to be 53.7% for the specimen after heat treatment at 1500°C, 54.4% for 1600°C, 69.0% for 1700°C, and 79.8% for 1800°C.…”

“…It could be seen from Figure B the major phase after firing was β ‐SiC with the minor phase of HoAlO 3 . The absence of α ‐SiC was attributed to the limited phase transition from β ‐ to α ‐SiC at relatively low temperature . Reflections in Figure B‐D indicated no obvious phase difference among these simulated surrogate samples.…”

Microstructure and indentation damage resistance of ZrB2‐20 vol.%SiC ipo‐eutectic composites

“…In addition, it is found that mainly β‐SiC could be detected in the composite. It is interesting that from liquid state to solid state, cubic beta silicon carbide was formed but not hexagonal alfa silicon carbide . A More detailed analysis is needed.…”

“…It is interesting that from liquid state to solid state, cubic beta silicon carbide was formed but not hexagonal alfa silicon carbide. 29 A More detailed analysis is needed. On the surface perpendicular to the solidification direction, the calculated Lotgering factor f (00l) for ZrB 2 phase was 0.98 and on the surface parallel to the resolidification direction the Lotgering factor of f (hk0) was 0.25.…”

The Preparation and Microstructure of Nanocrystal 3C-SiC/ZrO2 Bilayer Films

“…Because of its high-temperature stability, excellent irradiation resistance, low neutron capture cross section and non-reaction with water at high temperature, SiC will be an ideal candidate for use as the coating of zirconium alloys. Compared with SiC with other crystal structures, β-SiC (also named 3C-SiC) has better anti-wear, lower processing temperature, and higher corrosion resistance and irradiation resistance [ 9 ]. Meanwhile, 3C-SiC has been successfully used as the middle layer for preventing fission product diffusion and providing structural support in TRISO (Tri-Structural Isotropic) fuel particles [ 10 ].…”