Fine study of hierarchical interphase constructed by Ti3SiC2 and carbon nanotubes in SiCf/SiC composites

The interphase in silicon carbide fiber-reinforced silicon carbide ceramic matrix composites (SiCf/SiC) assumes a significant role in the mechanical properties exhibited at elevated temperatures. The strength, toughness, and chemical stability of a composite is frequently influenced by the optimization of its interphase. In this work, the MAX phase (Ti3SiC2) and carbon nanotubes (CNTs) were successively deposited on the SiCf using the molten salt method and chemical vapor deposition technique, respectively, to create a hierarchical structure. Transmission electron microscopy was employed to undertake a comprehensive investigation of the interfacial component in SiCf/SiC composites. The detailed study of interphases in SiCf/SiC composites has been conducted through the analysis of crystallization, the bonding natures, and the micromorphology, encompassing geometry and constituent characteristics. A bilayer consisting of TiC-Ti3SiC2/Ti5Si3 and a vertical array of carbon nanotubes (CNTs) with a length of 7 μm is fabricated on the surface of SiCf/Ti3SiC2-CNTs. The SiCf/Ti3SiC2/SiC and SiCf/Ti3SiC2-CNTs/SiC composites exhibit lamellar structures of Ti3SiC2, which indicates a further crystallization of Ti3SiC2 resulting from the formation of SiC matrix by PIP procedure. The interphase of SiCf/Ti3SiC2-CNTs/SiC composite may be categorized into four distinct layers: a TiC phase, a TiSi2 phase, a transition phase of TiSi2/TiC, and a Ti3SiC2 phase. This interphase structure is more intricate compared to the interphase structure observed in the SiCf/Ti3SiC2/SiC composite. This research indicates significant value for the future design and optimization of interfaces.