Studies On Damage In SiC Induced By Helium Ions Irradiation

Material issue has been one of the key factors restricting the development of future advanced nuclear. Advanced nuclear device is in a high temperature, high flux neutron irradiation and other harsh environment, where neutron irradiation not only can cause severe damage in the cladding material of displacement but also nuclear transmutation reactions induced by neutrons in the envelope materials can generate a lot of He atoms. He atoms with a low solubility in the material can migrate gathering into He bubbles at high temperatures. Displacement damage and He-doped cladding material behavior can cause microscopic changes in the structure and macro performance degradation affecting the safe operation of the reactor. Sintered Si C is a kind of ceramic material with a high melting point, high corrosion resistance, high thermal conductivity, low thermal expansion coefficient and low neutron cross section,which is considered to be one potential cladding candidate material used for advanced nuclear device. At present, domestic and foreign researchers mainly studied single Si C and there is a lack of research for Sintered Si C.We studied Sintered Si C irradiated by He ions preliminarily, as compared to single 6H-Si C, we also studied 6H-Si C irradiated by He ions further. In this paper, for researching He ion irradiation-induced macroscopic and microscopic properties of Si C material with different doses under different temperatures, many testing methods were used, the main conclusions are shown as follows:1. He-irradiated 6H-Si C was studied. Raman measurments indicate that:Amorphization of 6H-Si C irradiated to a high flunce at RT occurred; Recovery of defects appeared in the high-temperature irradiation, when helium bubbles exist, they could inhibit defects recovery. HRXRD measurments indicate that: The XRD curveappeared diffuse scattering, when 6H-Si C was irradiated to a high flunce at RT; With dose increased under high temperature irradiation, near-surface strain and maximum strain peaks moved to a small angle.2. He-irradiated Sintered Si C was studied. Raman measurments indicates that:The intensity of the Raman peaks decreased with increasing fluence because of the influence of lattice defects induced by He implantation on the absorption coefficient of the damaged layer. The relative Raman intensity changes at different rates due to the formation of He bubbles. Nano-indentation measurments indicate that: When Sintered Si C was irradiated to a high flunce at RT, the averaged nano-indentation hardness was lower than the unimplanted specimen attributed to the coating effect of the amorphous layer. When Sintered Si C was irradiated to a high flunce at 600℃,with implantation fluence increasing the averaged nano-indentation hardness increases gradually due to I-loops formed. TEM measurments indicate that: The morphology and density of He bubbles in grain interiors(GIs) and at grain boundaries(GBs) are related to the implantation fluence.3. Compared He-irradiated 6H-Si C with Sintered Si C. It can be seen that under the same irradiated conditions, the new Si-Si bond vibration mode appeared in the Raman spectroscopy of 6H-Si C; Sintered Si C showed a greater difference in hardness;it was easier to nucleate and grow up for He bubbles in the Sintered Si C.