SiC具有耐辐射、低感生放射性、耐高温等特点,在先进核能系统中具有重要的应用.用1.5 MeV的Si离子在常温下注入单晶六方SiC和多晶化学气相沉积SiC,注量分别为1×1014—2×1016 cm?2和1×1015—2×1016 cm?2,利用X射线衍射(XRD)仪和白光干涉仪测量材料的晶格常数和辐照肿胀随着注量增大的变化规律.结果显示:在1.5 MeV Si离子常温辐照下,注量达到2×1015 cm?2时,单晶六方SiC完全非晶化;注量在1×1015—5×1015 cm?2,单晶六方SiC的辐照肿胀明显高于多晶化学气相沉积SiC的辐照肿胀;注量达到1×1016 cm?2时,单晶六方SiC和多晶化学气相沉积SiC的辐照肿胀达到饱和并趋于一致,肿胀结果表明常温辐照环境下多晶化学气相沉积SiC的非晶化阈值剂量大于单晶六方SiC.通过分析单晶六方SiC和多晶化学气相沉积SiC常温辐照肿胀差异的原因,研究了晶界对SiC材料非晶化肿胀规律的影响,并对XRD辐照肿胀测量方法的适用范围进行了讨论.%Silicon carbide (SiC) is considered as one of the most promising structural and coating materials for advanced nuclear applications, due to its low neutron capture cross section and excellent irradiation resistance. The difference in swelling behavior between monocrystalline and polycrystalline SiC is experimentally investigated by heavy ion irradiation at room temperature (RT). In this work, single crystal hexagonal (6H) SiC and polycrystalline chemically vapor-deposited (CVD) SiC are irradiated by 1.5 MeV Si ions with the fluences of 1×1014–2×1016 cm?2 and 1×1015–2×1016 cm?2, respectively, at RT. The step height of irradiation swelling is measured by a white light interferometer and the lattice expansion of the damage layer is characterized by using X-ray diffraction (XRD) spectrometry, in addition, the actual irradiation swelling is obtained by dividing the height of swelling step by the depth of damage layer. The XRD profiles show that the lattice expansion in the damage layer increases with the increase of irradiation fluence, and the new diffraction peak relating to the lattice structure of damage layer disappears in a fluence of 2 × 1015 cm?2, which means that the damage layer is completely amorphous at this time and the threshold dose of amorphization at RT in single crystal 6H-SiC is less than 0.8 dpa. The direct-impact model is used to fit the swelling step heights of CVD SiC and 6H-SiC irradiated by 1.5 MeV Si, and the swelling results show that the amorphization threshold dose of polycrystalline CVD SiC is larger than that of single crystal 6H-SiC. In the present work, three distinct stages are found in the heavy-ion irradiation swellings between monocrystalline and polycrystalline SiC. i.e., low-fluence region, intermediate-fluence region, and high-fluence region stage. 1) In the low-fluence region, the swellings are similar to each other, since the swelling is mainly contributed to by point defects in this region, and the micron sized grains in polycrystalline CVD SiC are of single crystal structure. 2) In the intermediate-fluence region, the irradiation swelling of the polycrystalline CVD SiC is smaller than that of the single crystal 6H-SiC, since the irradiation-induced amorphousness in polycrystalline CVD SiC is relatively hard to occur due to the existence of grain boundary in this region. 3) The irradiation swellings of 6H-SiC and CVD SiC are almost the same at the high-fluence region stage, since the irradiation swelling is caused by amorphization in this region, and the swelling depends on the difference between densities before and after irradiation. In addition, in the irradiation swelling analysis of SiC materials, XRD swelling measurement method is suitable for irradiation swelling induced by point defects, especially for neutron irradiation experiments.
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