High compacted aluminum nitride (AlN) substrates were prepared by aqueous tape casting. Aluminium dihydrogen phosphate was used to modify AlN particle surface from hydrolysis during casting process. The absolute value of zeta potential for the AlN particle treated by Al(H₂PO₄)₂ was 60mv at pH = 9. The slurry suitable for tape casting was prepared which possessed shear-thinning behavior and appropriate viscosity. The results showed that the green tapes own excellent properties including high bulk density, uniform pore distribution and low porosity. The samples were fired at 1700°C (lower than melting point of Pt) with pressureless sintering process which can be used to fabricate complex device.

In this paper, a two-dimensional characteristic unit was used to simulate the thermal–mechanical performance of a fully ceramic microencapsulated (FCM) fuel pellet, and the criterion of FCM structure integrity was discussed. FCM structure integrity can be reflected though the integrity of the silicon carbide (SiC) matrix or SiC layers because of the excellent fission retention capability of SiC ceramics. The maximum temperature of the SiC matrix under normal conditions of the pressure water reactor (PWR) environment was about 1390 K, which was lower than the decomposition point of SiC. The maximum hoop stress of the SiC matrix, especially the inner part, was up to about 1200 MPa, and the hoop stress of the non-fuel region part was lower than the inner part, which can be attributed to the deformation of tristructural-isotopic (TRISO) particles. The hoop stress of the SiC layers at the end of life was only about 180 MPa, which is much lower than the strength of the chemical vapor deposition (CVD)-SiC. The failure probability of the SiC layer was lower than 9 × 10⁻⁵; thus, the integrity of SiC layers and the fission retention capability were maintained. The structure integrity of FCM fuel was broken because the SiC matrix cracked.

Wire and arc additive manufacturing based on cold metal transfer (WAAM-CMT), as a kind of clean and advanced technology, has been widely researched recently. It was analyzed in detail for the microstructure and mechanical properties of WAAM-CMT printed TiB₂/AlSi7Mg0.6 samples fore-and-aft heat treatment in this study. Compared with the grain size of casted AlSi7Mg0.6 samples (252 μm), the grain size of WAAM-CMT printed AlSi7Mg0.6 samples (53.4 μm) was refined, showing that WAAM-CMT process could result in significant grain refinement. Besides, the grain size of WAAM-CMT printed TiB₂/AlSi7Mg0.6 samples was about 35 μm, revealing that the addition of TiB₂ particles played a role in grain refinement. Nevertheless, the grain size distribution was not uniform, showing a mixture of fine grain and coarse grain, and the mechanical properties were anisotropic of the as-printed samples. This study shows that T6 heat treatment is an efficient way to improve the nonuniform microstructure and eliminate the anisotropy in mechanical properties.

Silicon carbide (SiC) is a promising structural and cladding material for accident tolerant fuel cladding of nuclear reactor due to its excellent properties. However, when exposed to severe environments (e.g., during neutron irradiation), lattice defects are created in amounts significantly greater than normal concentrations. Then, a series of radiation damage behaviors (e.g., radiation swelling) appear. Accurate understanding of radiation damage of nuclear materials is the key to the design of new fuel cladding materials. Multi-scale computational simulations are often required to understand the physical mechanism of radiation damage. In this work, the effect of neutron irradiation on the volume swelling of cubic-SiC film with 0.3 mm was studied by using the combination of molecular dynamics (MD) and rate theory (RT). It was found that for C-vacancy (C_V), C-interstitial (C_I), Si-vacancy (Si_V), Si-interstitial (Si_I), and Si-antisite (Si_C), the volume of supercell increases linearly with the increase of concentration of these defects, while the volume of supercell decreases linearly with the increase of defect concentration for C-antisite (C_Si). Furthermore, according to the neutron spectrum of a certain reactor, one RT model was constructed to simulate the evolution of point defect under neutron irradiation. Then, the relationship between the volume swelling and the dose of neutrons can be obtained through the results of MD and RT. It was found that swelling typically increases logarithmically with radiation dose and saturates at relatively low doses, and that the critical dose for abrupt transition of volume is consistent with the available experimental data, which indicates that the rate theory model can effectively describe the radiation damage evolution process of SiC. This work not only presents a systematic study on the relationship between various point defect and excess volume, but also gives a good example of multi-scale modelling through coupling the results of binary collision, MD and RT methods, etc., regardless of the multi-scale modelling only focus on the evolution of primary point defects.

The effect of non-fuel part size on the thermal-mechanical performance of fully ceramic microencapsulated (FCMTM) Fuel was investigated, and the non-fuel part size was selected according to integrity maintaining of non-fuel part and silicon carbide (SiC) layers. The non-fuel part size can affect the FCMTM temperature and stress distribution greatly by changing the distance between tristructural isotropic (TRISO) particles. The maximum temperature of SiC matrix increased from 1220 K to 1450 K with the non-fuel part size increasing from 100 μm to 500 μm, and the matrix temperature of all the samples was lower than the decomposition point of SiC ceramics. The maximum hoop stress decreased with non-fuel part size, but the inner part exhibiteda crosscurrent trend. The inner part of the SiC matrix lost structure integrity because of the large hoop stress caused by the deformation of TRISO particles, however, the non-fuel parts of FCMTM pellet may maintain their integrity when the non-fuel part size was larger than 300 μm. SiC layers hoop stress increased with non-fuel part size, and the failure probability of SiC layer was lower than 2.2 × 10⁻⁴ for the FCMTM pellet with small non-fuel part size. The integrity of non-fuel and SiC layers can be maintained for the FCMTM pellet with the non-fuel part size from 300 μm to 400 μm.

Hydrogen plays an important role in the corrosion of zirconium alloys, and the degree of influence highly depends on the alloy composition and conditions. In this work, the effects of hydrogenation on the corrosion behavior of Zircaloy-4 in water containing 3.5 ppm Li + 1000 ppm B at 360 °C/18.6 MPa were investigated. The results revealed that hydrogenation can shorten the corrosion transition time and increase the corrosion rates of Zircaloy-4. The higher corrosion rates can be ascribed to the larger stress in the oxide film of hydrogenated samples, which can accelerate the evolution of the microstructure of the oxide film. In addition, we also found that hydrogenation has little effect on the t-ZrO₂ content in the oxide film and there is no direct correspondence between the t-ZrO₂ content and the corrosion resistance of the Zircaloy-4.