Lihua Guo,Guoqiang Wang,Feng Zhang,Linyuan Lu,Bin Luo,Hongtao Huang,Jun Lin
The fissile fuel loss in tungsten (W) based ceramic-metal (Cermet) element used in nuclear thermal propulsion is of great importance. In this study, the W-Y 2 O 3 composite matrix was manufactured tentatively by Spark Plasma Sintering (SPS) to relieve the fuel loss. Performance evaluation of hydrogen (H 2 ) permeation and diffusion behaviors in the matrix was carried out by a gas permeation device. The results indicate that the diffusion coefficient of H 2 in the pure W matrix is nearly 10 times larger than that in the W-Y 2 O 3 matrix at a test temperature of 823 K. Based on the results, a careful investigation of the fuel loss mechanism of the Y 2 O 3 dispersed W matrix was performed. SEM and TEM showed that the fine Y 2 O 3 particles are distributed along grain boundaries of the W ternary-phase and present a distinct transition region of about 10 nm between the Y 2 O 3 and W phases. In particular, the crystallographic orientation relationship suggests that a semi-coherent structure is formed at the W/Y 2 O 3 phase interface : (0 1 −1) W || (1 0 −1) Y 2 O 3 and [0 1 1] W || [1 1 1] Y 2 O 3 . This semi-coherent structure is favorable for binding the two phases together tightly, thus hindering the inward diffusion of H 2 greatly. Moreover, the improved density and refined size of the W grains are achieved. Therefore, there is no doubt that the dispersion of Y 2 O 3 is beneficial for lowering the H 2 diffusion rate in the W matrix and thus reducing the fuel loss effectively. This work furthers our understanding of the key role of Y 2 O 3 in the W matrix used in nuclear thermal propulsion.
Ni-W-ZrO 2 -CeO 2 nanocomposites were prepared by pulse electrodeposition for high wear and corrosion resistance as a protective coating. The structure (morphology, phase composition, roughness, crystallite size , surface feature) and properties (hardness, wear and corrosion resistance) of the nanocomposites were evaluated by various methods. The formation mechanism of the nanocomposites were proposed. The results show that the nanocomposite coatings are dense with nodular-like structure. The cauliflower-like protrusion clusters were formed due to the ‘tip discharge effect’ in the uneven distribution of electric field. It demonstrated that these nanoparticles were homogeneously distributed in the Ni-W matrix. The presence of the nanoparticles in Ni-W matrix improved the hardness, wear and corrosion resistance . The combination of ceramic particles and rare earth oxide particles was an excellent reinforcement phase for Ni-W matrix. The sample obtained at 1000 Hz has the optimal hardness and wear resistance, as well as the satisfying corrosion resistance. The nanocomposite deposited for 10 min owns the superior corrosion resistance in the initial stage of immersion. Ni-W-ZrO 2 -CeO 2 nanocomposites own excellent performance and exhibit potential application values in harsh conditions.
危险品化学品经营许可证（带存储）