清华大学 核能与新能源技术研究院，北京 100084
刘马林，杨旭，刘荣正，等. 流化床-化学气相沉积制备核燃料颗粒铝金属包覆层［J］. 中国粉体技术，2025，31（5）：1-9.
LIU Malin， YANG Xu， LIU Rongzheng， et al. Preparation of aluminum coating for nuclear fuel particles by fluidized bed chemical vapor deposition［J］. China Powder Science and Technology，2025，31（5）：1−9.
DOI：10.13732/j.issn.1008-5548.2025.05.008
收稿日期：2024-11-21，修回日期：2025-05-08，上线日期：2025-07-04。
基金项目：国家万人计划青年拔尖人才项目，编号：20224723061；国家自然科学基金项目，编号：22478220。
第一作者简介：刘马林（1982—），男，副教授，博士，博士生导师，国家万人计划青年拔尖人才，研究方向为先进核燃料设计、制备和评价。E-mail：liumalin@tsinghua. edu. cn。
通信作者简介：杨旭（1995—），男，助理研究员，博士，研究方向为包覆颗粒金属及碳化物包覆层研究。E-mail：yangxuthu@tsinghua.edu. cn。
摘要：【目的】 针对金属基燃料元件中铀核芯与外部金属基体间的相容性不好，运行过程中核芯与基体界面处易出现空隙导致燃料元件失效的问题，设计含有铝金属包覆层的包覆颗粒，通过金属包覆层提升核芯与金属基体间的界面相容性。【方法】 采用流化床-化学气相沉积技术，以三异丁基铝为前驱体在颗粒表面沉积铝包覆层，设计铝包覆层的前驱体输运与包覆层沉积装置，研究铝包覆层包括前驱体输运条件、沉积温度参数、颗粒流化参数等的制备工艺。【结果】 通过对设备与工艺参数的调节，可以提升铝包覆层的沉积效率与包覆质量，最终获得金属铝包覆层的制备工艺与参数，在球形颗粒和非球形颗粒表面均制备得到厚度约8 μm且均匀的铝包覆层，包覆层生长速率约2. 6 μm/h，内部致密并且实现与核芯间的紧密结合。【结论】 流化床-化学气相沉积法适宜于铝金属包覆层的制备，可以用于下一步的金属基核燃料研究，但在包覆速率和宏量生产工艺方面还有值得继续优化。
关键词：包覆颗粒；先进核燃料；铝包覆层；流化床；化学气相沉积
Objective Metal matrix dispersion nuclear fuel elements have garnered widespread attention worldwide. Currently, the metal matrix dispersion fuel elements in use are U-Mo alloy powders or U3Si2 core particles uniformly dispersed within an aluminum (Al) matrix. These fuel elements exhibit favorable thermal conductivity, and the dispersed nature of the fuel allows for efficient heat removal and a higher uranium concentration compared to conventional fuel types. However, in the highly irradiated environment within a reactor, the interface between the fuel core and the external Al matrix is prone to expansion, leading to void formation. This study aims to deposit a uniform Al coating on nuclear fuel particles via the fluidized bed-chemical vapor deposition (FB-CVD) method to enhance the compatibility between the particles and the external Al matrix.
Methods Spherical zirconia particles with a diameter of 500 μm were used to simulate uranium dioxide particles. Irregular tungsten carbide (WC) particles， sized between 50-100 μm, were utilized as the core to simulate irregular U3Si2 cores. The Al coating was prepared using an FB-CVD device with a conical fluidization tube, ensuring uniform coating by moving the particles like a fountain. In the experimental setup, triisobutylaluminum (TIBA) served as the precursor, placed in an evaporation tank outside the equipment. The TIBA vapor was transported to the fluidized bed by carrier gas, and the Al coating was deposited on particles through the high-temperature decomposition of TIBA. During the experiment, particle fluidization and the precursor deposition rate were regulated by adjusting the deposition temperature and carrier gas flow rate, while the precursor transport rate was controlled by modifying its evaporation temperature and carrier gas rate. The effects of various process parameters on the growth of Al coating were studied.
Results and Discussion A uniform and durable aluminum coating was achieved by optimizing the precursor carrier gas velocity, reaction temperature, and precursor evaporation temperature. The coated particles showed a metallic luster, with no adhesion between them, indicating good fluidity during the coating process without stagnation in any specific region. A uniform and intact Al coating free from cracking, protrusions, or delamination was formed, and it was well-bonded with the matrix particles. Energy dispersive spectroscopy (EDS) analysis revealed that Al was the main component of the coating, with a growth rate of approximately 2. 6 μm/h. Additionally, by co-fluidizing zirconia particles with irregular WC particles, a uniform Al coating on the surface of the irregular particles was realized as the irregular WC particles were driven to form a uniform flow pattern.
Conclusion A uniform and dense Al coating was successfully deposited on the surfaces of the spherical zirconia particles and irregular WC particles using TIBA as the precursor via the FB-CVD method. The conclusions are: 1) An Al coating preparation system was designed, and stable transport of the TIBA precursor was successfully realized. A stable and durable Al coating was achieved through process parameter optimization. 2) The relationship between the growth rate of Al coating and process parameters was verified. The deposition rate of the Al coating increased with higher reaction temperatures and precursor transport volumes, but excessive increases led to undesirable deposition in other areas of the equipment. 3) The growth rate of the Al coating was about 2. 6 μm/h， and the prepared Al coating exhibited uniform thickness with interior pores. Also, the coating was tightly bonded to the core without gaps or delamination. 4) A uniform Al coating on the surface of irregular particles was achieved through the co-fluidization process.
Keywords：coated particle; advanced nuclear fuel; aluminum coating; fluidized bed; chemical vapor deposition
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