You Xie

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.

Lightweight, high-temperature-resistant carbon-bonded carbon fiber (CBCF) composites with excellent thermal insulation properties are desirable materials for thermal protection systems in military and aerospace applications. Here, glucose was introduced into the polyacrylamide hydrogel to form the glucose-polyacrylamide (Glu-PAM) hydrogel. The CBCF composites were prepared using the Glu-PAM hydrogel as a brand-new binder, and the synergistic effect between glucose and acrylamide was investigated. The results showed the Glu-PAM hydrogel could limit the foaming of glucose and enhance the carbon yield of glucose. Meanwhile, the dopamine-modified chopped carbon fiber could be uniformly mixed by high-speed shearing to form a slurry with the Glu-PAM hydrogel. Finally, the slurry was successfully extruded and molded to prepare CBCF composites with a density of 0.158~0.390 g cm⁻³ and excellent thermal insulation performance and good mechanical properties. The compressive strength of CBCF composites with a density of 0.158 g cm⁻³ in the Z direction is 0.18 MPa, and the thermal conductivity in the Z direction at 25 °C and 1200 °C is 0.10 W m⁻¹ k⁻¹ and 0.20 W m⁻¹ k⁻¹, respectively. This study provided an efficient, environment-friendly, and cost-effective strategy for the preparation of CBCF composites.