He-H synergistic effects influence the performance of structural materials in fusion reactors. Due to the lack of high-intensity fusion neutron sources, multiple ion beam irradiation has been widely used as an emulation method to study its synergistic effects. However, the damage rate under multiple ion beam irradiation is three to four orders of magnitude higher than that under fusion neutron irradiation, and its effect on the cavity swelling is still unclear. In this study, pure nickel was irradiated with single and triple ion beams to ~1 displacements per atom (dpa) at 450 °C. The damage rate ranged from 1.4 × 10⁻⁴ to 1.4 × 10⁻³ dpa/s, with the identical gas-dose ratios of ~400 H appm/dpa and 100 He appm/dpa. Large and isolated cavities formed under single ion irradiation, while triple ion irradiation induced smaller and denser cavities and higher swelling. As the damage rate increased, the cavity size, density, and swelling decreased, due to the constraint of cavity nucleation and growth processes. The effect of damage rate on cavity evolution under triple ion irradiation strongly depends on two competing factors: the enhancement of aggregation and binding of H/He/vacancies, and the enhancement of vacancies–interstitials recombination with increasing damage rate.

This study systematically investigated the diffusion bonding of SiC ceramics using Ti interlayers via spark plasma sintering. The effects of holding time (5 min, 10 min, 20 min), joining temperature (1300 °C, 1400 °C, 1500 °C), and Ti foil thickness (5 μm, 10 μm, 20 μm) on joint microstructure and shear strength were characterized through SEM, TEM, XRD, and EDS. The results revealed that the joining temperature was the key factor influencing joint performance, while the holding time and Ti foil thickness had relatively minor effects. When joined at 1300 °C, the primary reaction products in the interlayer consisted of TSC, TiC, and Ti₅Si₃ phases. Prolonged holding times improved the shear strength, but inhomogeneous phase distribution adversely affected the stability of mechanical properties. In joints with thinner Ti interlayers (5 μm and 10 μm), Si-rich phases tend to aggregate in the central region, leading to stress concentration and reduced joint strength. As the joining temperature increased to 1400 °C and 1500 °C, the Ti₅Si₃ phase was gradually consumed, and the interlayer primarily contained TSC and TiC phases, leading to a significant enhancement in shear strength, with a maximum value of 127.67 MPa achieved at 1400 °C. These findings provide important experimental evidence and theoretical support for optimizing the joining process of SiC ceramics.