AgCuTi-based composite fillers reinforced with Carbon Nanotubes (CNTs) were prepared by mechanical ball milling and ultrasonic agitation. The morphological features, chemical components, and melting characteristics of the composite fillers with different content of CNTs addition were investigated using Field Emission Scanning Electron Microscopy (FESEM), X-Ray Diffraction (XRD) and a Differential Scanning Calorimeter (DSC). After being heated at 900 ℃, the microstructure of the composite fillers was examined through FESEM and Transmission Electron Microscopy (TEM) to analyze the interfacial characteristics in the AgCuTi-CNTs system. The microstructures of the composite fillers with 0.5 wt% CNTs and 0.1 wt% CNTs were compared. It was found that 0.5 wt% CNTs were favorable for dispersive distribution of the structure. Nano-sized TiC particles formed in the reaction of CNTs with Ti, resulting in the transformation of TiCu₂ with high Ti content and Ti₂Cu₃ phases to TiCu₄ phase with low Ti content. Additionally, the microstructure evolution of the composite fillers was studied by changing the ratio of Ti/CNTs. Results showed that CNTs significantly influenced the wettability of the AgCuTi filler. After addition of 0.3 wt% of CNTs, the spreading area of the composite filler on the C/C composite increased by 146.0%.

The exploration towards cost-effective filler metal for ceramics joining has always been the key issues for ceramics joining. Herein, we reveal that the Al metal prefers to spread on the ZrO₂ based ceramic under the air heating condition, due to the geometric limit effects by in-situ formed dense Al₂O₃ surface. Inspired by this, the joining of ZrO₂ based ceramics was realized in air with Al metal as filler, through the diffusion of Al towards ceramic side. The Al element can induce obvious interfacial bonding effect on Al₂O₃ layer and ZrO₂ ceramic, where the hybridization among the Al-p, Zr-d and O-p orbitals plays a key role. The in-situ formed Al₂O₃ layer on Al filler surface is vital for forming the fine interface (shear strength of ~36 MPa), which results in the relief of lattice mismatch and peak stress at ceramic-filler metal transition interface.