Research on the Preparation and Properties of Iron-based Composites Used as Neutron Absorbing in Gray Control Rod

中国已从美国西屋公司引进、吸收和消化AP1000核电技术。为了形成自主知识产权的关键核电技术，本文对堆芯关键部件灰控制棒用中子吸收体材料进行了相关研究。基于前期对多种元素的核特性及燃耗分析获得了几种符合灰控制棒性能要求的候选元素，如Tm、Tb和Dy。本文采用粉末冶金方法(高能球磨、冷等静压与烧结)制备出了两种堆芯灰控制棒用中子吸收材料Fe-Tm2O3和Fe-TbFeO3-DyFeO3芯块。采用材料分析方法对球磨粉末、烧结块体进行了微观组织与微观化学分析与表征，探索了球磨工艺和烧结工艺对块体物相与性能的影响，测试了块体材料的相关物理性质、力学性能和高温高压耐腐蚀性能。 对Fe-25.68%Tm...China has imported, absorbed and digested the nuclear power technology of the AP1000 reactor from the American Westinghouse Electric Corporation. In order to create a new type nuclear power technology with our own proprietary intellectual property rights, this article presents correlational research about the neutron absorber material used as the gray rod which is the key material in the core of r...学位：工学硕士院系专业：能源学院_核工程与材料学号：3242013115228

Preparation and Properties Investigationof Neutron Absorber Material Fe-TbFeO_3-DyFeO_3

采用粉末冶金工艺制备了Fe-TbFeO_3-DyFeO_3块体材料。利用X射线衍射仪、扫描电子显微镜和透射电子显微镜对球磨粉末和烧结块体进行了微; 观组织分析,测试了块体材料的热物理性能、耐腐蚀性能和离子辐照性能。实验结果表明,通过球磨可获得混合均匀的Fe-Tb_4O_7-Dy_2O_3纳米; 尺寸颗粒的混合粉末。高温下Tb_4O_7转变成Tb_2O_3,烧结块体中的Tb_2O_3和Dy_2O_3的含量随烧结温度升高而降低,在1 200; ℃烧结24; h可获得Fe-TbFeO_3-DyFeO_3块体材料。Fe-TbFeO_3-DyFeO_3块体材料具有高的热导率和低的热膨胀系数,腐蚀性能较差。; 在400~600 ℃辐照至25 dpa,随辐照温度升高辐照肿胀率逐渐降低,400 ℃辐照肿胀率最大为0.5%。Fe-TbFeO_3-DyFeO_3 was prepared by powder metallurgy technology. The; microstructures of ball milled powder mixtures and sintered bulks were; analyzed by X-ray diffraction, scanning electron microscope and; transmission electron microscope. Thermophysical properties, corrosion; resistance and ion irradiation properties of the sintered; Fe-TbFeO_3-DyFeO_3 bulks were measured and analyzed. The experiment; results show that the homogeneous nanocrystalline Fe-Tb_4O_7-Dy_2O_3; powder mixtures are obtained by ball milling. Tb_4O_7 transforms to; Tb_2O_3 at high temperature. Contents of Tb_2O_3 and Dy_2O_3 decrease; with temperature increase during sintering process, and; Fe-TbFeO_3-DyFeO_3 bulks are obtained after sintering at 1 200 ℃ for 24; h. The bulks have high thermal conductivity, low thermal expansion; coefficient and poor corrosion resistance performance. The sintered; bulks are irradiated at 400-600 ℃ for 25 dpa. It is found that the; irradiation swelling rate decreases with temperature increase, and the; maximum swelling rate is 0.5% at 400 ℃.国家科技重大专项大型先进压水堆核电站研究资助项

Tb_4O_7-TiO_2 Mixture Powders Prepared by High Energy Ball Milling

通过高能球磨技术制备了Tb_4O_7-18Ti O_2(质量分数,%)纳米尺度复合粉末。采用激光粒度测试仪、X射线衍射仪(XRD)、扫描电子显微镜(SEM)和透射电子显微镜(TEM)对不同球磨时间的混合粉末的微观形貌组织、颗粒与晶粒大小以及晶格畸变量等进行了研究与表征。结果表明,混合粉末经过高能球磨后其颗粒与晶粒尺寸均达到了纳米级,组织均匀。Tb_4O_7相的X射线衍射峰随球磨时间的增加逐渐宽化且向大角度偏移;Ti O_2相衍射峰强度逐渐降低,在球磨4 h后消失。随球磨时间的增加,颗粒和晶粒的平均尺寸减小,球磨初期减小很快,球磨后期减小缓慢,最后趋于一个稳定值。96 h球磨后颗粒和晶粒的平均尺寸分别为200和95 nm,晶格畸变量达到1.35%。同时探讨了TiO_2相固溶和纳米晶形成原因以及微观组织演变的机制。The nanocrystalline powders of Tb_4O_7-18wt%Ti O_2 were prepared by high energy ball milling. Systematical investigations were carried out on microstructure, particle and grain size, lattice distortion and morphology of the Tb_4O_7-18wt%Ti O_2 milled powders using laser particle analyzer, X-ray diffraction, transmission electron microscopy and scanning electron microscopy. The results show that the nanocrystalline and nanoparticle powders are synthesized and microstructure is homogeneous after high energy ball milling. With the increase of ball milling time, the diffraction peaks of Tb_4O_7 phase are broadened gradually and move to large angles. Meanwhile, the diffraction peaks of Ti O_2 phase weaken gradually and disappear after 4 h milling. At the initial stage of ball milling, both particle size and crystalline size decrease significantly, then the sizes decline slowly and tend to be stable at the late stage of ball milling. After 96 h milling, the average particle size and crystalline size are 200 nm and 95 nm, respectively. The lattice distortion is up to 1.35%. The reason of solid solution of Ti O_2 and nanocrystalline formation and the mechanism of microstructure evolution were also discussed.福建省自然科学基金计划资助项目(2015J01021);; 国家自然科学基金(11305136