Search

Refractory metal single crystals have been applied in key high-temperature structural components of advanced nuclear reactor power systems, due to their excellent high-temperature properties and outstanding compatibility with nuclear fuels. Although electron beam floating zone melting and plasma arc melting techniques can prepare large-size oriented refractory metals and their alloy single crystals, both have difficulty producing perfect defect-free single crystals because of the high-temperature gradient. The mechanical properties of refractory metal single crystals under different loads all exhibit strong temperature and crystal orientation dependence. Slip and twinning are the two basic deformation mechanisms of refractory metal single crystals, in which low temperatures or high strain rates are more likely to induce twinning. Recrystallization is always induced by the combined action of deformation and annealing, exhibiting a strong crystal orientation dependence. The irradiation hardening and neutron embrittlement appear after exposure to irradiation damage and degrade the material properties, attributed to vacancies, dislocation loops, precipitates, and other irradiation defects, hindering dislocation motion. This paper reviews the research progress of refractory metal single crystals from three aspects, preparation technology, deformation behavior, and irradiation damage, and highlights key directions for future research. Finally, future research directions are prospected to provide a reference for the design and development of refractory metal single crystals for nuclear applications. [ABSTRACT FROM AUTHOR]

Molybdenum-Niobium (Mo-Nb) single crystals possess excellent mechanical properties, such as high strength and low creep rate at high temperatures, which leads to Mo-Nb single crystals' potential application in the irradiated and aerospace environment. Mechanical properties at high temperatures are closely related to structural defects, including the density of dislocation and low-angle grain boundaries in a single-crystal Mo alloy. It is well known that the density of defects is mainly contributed to by processing and annealing. To clarify the microstructural evolution of Mo-Nb single-crystal alloys, thermal annealing tests with temperatures varying from 1100 °C to 1700 °C were conducted. Two Nb contents (3 at.% and 6 at.%) were chosen to investigate the effect of Nb content on the thermal stability (≤1700 °C) of single-crystal Mo-Nb alloys. Samples with high Nb content (6 at.%) soften after annealing, while ductility at room temperature obviously enhances In the low Nb content (3 at.%) sample, however, hardening and softening occur after low (1100 °C) and high temperature annealing, respectively. The evolution of mechanical properties could be mainly attributed to the change of density in the low-angle grain boundary. Furthermore, the changing Nb element and dislocation density during annealing are still important to the strength and ductility of Mo-Nb single crystals. [ABSTRACT FROM AUTHOR]

Background and Objective: Studies have shown that tumor metastasis in a variety of tumors is associated with lymphangiogenesis and lymphatic vessel invasion (LVI). Tumor metastasis is an important factor that affects the prognosis of patients. The aim of this study is to determine the prognostic value of lymphangiogenesis and LVI in non-small cell lung cancer (NSCLC)., Methods: We marked the endothelial cells of lymph vessels in lymphangiogenesis with specific monoclonal antibody D2-40. Immunohistochemistry was used to detect the expression of lymphangiogenesis and LVI in 79 cases of stage I-III NSCLC., Results: The intratumoral lymphatic vessel density (ITLVD) was significantly higher in patients with N2 disease than those with N0 disease (P=0.015). The ITLVD was significantly higher in patients with LVI+ than that in those with LVI- (P = 0.009). The ITLVD was also remarkably higher in poorly differentiated tumors than that in highly differentiated ones (P = 0.007). The ITLVD was remarkably higher in adenocarcinoma than that in squamous cell carcinomas (P = 0.025). Kaplan-Meier revealed that the survival rates of patients with higher ITLVD were remarkably poorer than those with lower ITLVD (P = 0.007). Thus, the ITLVD is an important prognostic factor of NSCLC. The peritumoral lymphatic vessel density is not correlated with the prognosis., Conclusions: The ITLVD level is an important prognostic factor of NSCLC.

Background and Objective: The new edition of the TNM staging for lung and pleural tumours has been finished, which put weight on the extent of primary tumor as one of the important prognosises. But little study has performed on the primary tumor extent < or = 2 cm. The aim of this study is to explore the prognosis of patients with tumor extent < or = 2 cm in stage I of non-small cell lung cancer, which helps us to choose the best treatment for these patients., Methods: Retrospective study on the clinical response and survival time of whom underwent complete surgical resection and diagnosed as T1a of stage I NSCLC from 1998 to 2004 was analyzed. Data was analyzed by SPSS 17.0 software., Results: Overall survival rate was 80.8%. By the study, age (P = 0.241), gender (P = 0.175), history of smoking (P = 0.845), pathologic type ( P =0.265), and systematic mediastinal lymphadenectomy (SML )(P = 0.918) or not, postoperative adjuvant chemotherapy or not ( P = 0.616) and visceral pleural invasion (P = 0.827) were not the prognosises of these patients. Only the tumor differentiation such as poorly differentiated was the important prognosis ( P = 0.01)., Conclusion: In the tumor extent < or = 2 cm of stage I non-small cell lung cancer, the visceral pleural invasion maybe not influence the patients survival. The tumor differentiation is one of the important prognostic factors.