Tielong Shen

Irradiation-induced grain growth in nanocrystalline reduced activation ferrite/martensite steel

In this work, we investigate the microstructure evolution of surface-nanocrystallized reduced activation ferrite/martensite steels upon high-dose helium ion irradiation (24.3 dpa). We report a significant irradiation-induced grain growth in the irradiated buried layer at a depth of 300–500 nm, rather than at the peak damage region (at a depth of ∼840 nm). This phenomenon can be explained by the thermal spike model: minimization of the grain boundary (GB) curvature resulting from atomic diffusion in the cascade center near GBs.

The study of damage produced by H-ion and He-ion implantation in Lithium tantalate crystal

LiTaO3 single crystals were implanted by 100keV H-ion or He-ion. The results indicate that H-ion implantation creates a lower damage level than the He-ion implantation does, but the yield of oxygen vacancy produced by H-ion implantation is far higher than by He-ion implantation.

Structural Distortion and Defects in Ti

Ti3AlC2 samples are irradiated in advance by 3.5MeV Fe-ion to the fluence of 1.0×10 16 ion/cm 2 , and then are implanted by 500 keV He-ion with the fluence of 1.0×10 17 ion/cm 2 at room temperature. The irradiated samples are investigated by grazing incidence x-ray diffraction (GIXRD) and transmission electron microscopy (TEM). GIXRD results show serious structural distortion, but without amorphization in the irradiated samples. Fe-ion irradiation and He-ion implantation create much more serious structural distortion than single Fe-ion irradiation. TEM results reveal that there are a large number of defect clusters in the damage region, and dense spherical He bubbles appear in the He depositional region. It seems that the pre-damage does not influence the growth of He bubbles, but He-ion implantation influences the pre-created defect configurations.

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A type of home-made reduced activation martensitic steel, high silicon (SIMP) steel, is homogeneously irradiated with energetic Fe ions to the doses of 0.1, 0.25 and 1 displacement per atom (dpa), respectively, at 300°C and 1 dpa, at 400°C. Microstructural changes are investigated in detail by transmission electron microscopy with cross-section technique. Interstitial defects and defect clusters induced by Fe-ion irradiation are observed in all the specimens under different conditions. It is found that with increasing irradiation temperature, size of defect clusters increases while the density drops quickly. The results of element chemical mapping from the STEM images indicate that the Si element enrichment and Ta element depletion occur inside the precipitates in the matrix of SIMP steel irradiated to a dose of 1 dpa at 300°C. Correlations between the microstructure and irradiation conditions are briefly discussed.

AlC

The effects of high energy Kr26+ ions bombardment in polycrystalline Fe3O4 thin films are reported. The magnetic and electrical transport properties of the Fe3O4 thin films, are sensitive to Kr26+ ions bombardment and exhibit diverse behaviors with different fluence. The modifications could be interpreted by an effects related to the stress and damage induced by bombardment. In addtion, possible mechanism of modifications of Fe3O4 ferrite thin films was discussed briefly by using the variable-range hopping (VRH) model.