Penghui Lei

To meet the application requirements for structural components in Gen-IV nuclear reactors, it is essential to improve the high-temperature mechanical properties of 25Ni-20Cr (S35140) austenitic stainless steel. In this research, an improved austenitic stainless steel (N-S35140), derived from S35140 steel, was investigated. The scanning transmission electron microscopy (STEM) results indicate that the addition of titanium (Ti) microalloying elements to S35140 steel led to the precipitation of new strengthening nano phases, including M(C, N), MC, MN and Ti(C, N), in N-S35140. These precipitates effectively compensated for the loss of high-temperature strength resulting from the substantial reduction in carbon content. During the in situ transmission electron microscopy (TEM) compressive process at room temperature, the yield strength of N-S35140 steel is 618.4 MPa. At room temperature, the tensile strength of N-S35140 steel is 638.5 MPa, with a yield strength of 392.8 MPa and an elongation of 32.7%, which surpasses those of S35140 steel at room temperature. N-S35140 steel exhibits a tensile strength of 330.6 MPa, a yield strength of 228.2 MPa, and an elongation of 51.4% during the in situ scanning electron microscopy (SEM) tensile test conducted at 650 °C. As a consequence, the improved N-S35140 steel demonstrates significantly enhanced mechanical properties compared to the original S35140 steel, positioning it as a promising candidate for structural components in Gen-IV nuclear reactors.

In the rim zone of UO₂ nuclear fuel pellets, high burn-up and low temperatures drive changes in the microstructure, leading to the formation of high burn-up structures (HBS). This review focuses on the formation of HBS, beginning with a description of the two contentious mechanisms—recrystallization and polygonization—that are believed to be the primary controlling factors. We discuss experimental and simulation studies that support both mechanisms, emphasizing that although each mechanism can explain certain aspects of HBS formation, neither recrystallization nor polygonization alone is sufficient to fully explain the observed phenomena. Furthermore, we emphasize the intrinsic relationship between these two mechanisms, suggesting that they represent different manifestations of the same underlying process under varying conditions, and we reference relevant studies that support this perspective. Lastly, we underline the significance of investigating the formation processes of HBS and provide an outlook on future research directions based on the current state of knowledge.

A novel low-carbon 9Cr-ODS steel was exposed to corrosion in lead–bismuth eutectic saturated with oxygen at 500 °C for 1000 h, leading to the formation of three distinct layers of oxide film. From the outermost to the innermost layer, these included a Fe₃O₄ layer infiltrated with Pb, a FeCr₂O₄ layer, and an inner oxide zone. The inner oxide zone was primarily composed of an unoxidized matrix and Cr₂O₃. The formation of the inner oxide zone was primarily attributed to the preferential oxidation of Cr following the infiltration of insufficient O content. Two distinct morphologies of the inner oxide zone were identified: one is porous, while the other is non-porous. The porous morphology is characterized by low Fe content and Pb infiltration. The loss of Fe is the main factor contributing to the development of the porous inner oxide zone and the infiltration of Pb, while the short-range diffusion of Cr promotes the growth of Cr₂O₃, resulting in a needle-like morphology.

Transition metal nitrides have extensive applications, including magnetic storage devices, hardware resistance coatings, and low-temperature fuel cells. This study investigated the structural, electrical, and mechanical properties of thin zirconium nitride (ZrN) films by examining the effects of laser irradiation times. Thin ZrN films were deposited on glass substrates using pulsed DC magnetron sputtering and irradiated with a diode laser for 6 and 10 min. Characterization was performed using X-ray diffraction (XRD), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), nanoindentation, and four-point probe techniques. Extended laser irradiation times resulted in increased numbers of peaks on XRD analysis, indicating enhanced crystalline behavior of thin ZrN film. SEM analysis revealed surface voids, while HRTEM showed nanostructured ZrN with uniform plane orientation. The electrical properties of the thin ZrN film improved with extended laser irradiation, as demonstrated by a reduction in sheet resistance from 0.43 × 10⁹ Ω to 0.04 × 10⁹ Ω. Additionally, nanoindentation tests revealed an increase in hardness, rising from 8.91 GPa to 9.36 GPa.

In this study, the stability of Cr₂O₃, ZrO₂, and Mn₃O₄ oxide films in high-temperature liquid lead–bismuth eutectic (LBE) was systematically investigated using both experimental and first principles calculation methods. The research findings indicated that Cr₂O₃ demonstrated superior structural integrity at corrosion temperatures of both 600 °C and 700 °C and displayed exceptional resistance to LBE corrosion. ZrO₂ demonstrates resistance to LBE infiltration. However, the emergence of cracks in the vicinity of the ZrO₂ layer and the metal interface undermines the protective layer’s integrity. Mn₃O₄ exhibits susceptibility to corrosion by LBE and lacks resistance to its effects. First principles calculations indicate that Pb and Bi atoms are most readily adsorbed onto the Mn₃O₄ surface, promoting the detachment of Mn atoms. The results show that the corrosion resistance of the three oxide films is ranked in the following order: Cr₂O₃ > ZrO₂ > Mn₃O₄.