Process and properties of vertically aligned graphene coated Ni foam composite interlayer for brazing C/C composite and Nb

To address the problem of high residual stresses and high-temperature service requirements in the brazed joints of carbon/carbon (C/C) composites and niobium (Nb), vertically aligned few-layer graphene (VFG) coupled with the TiNi solder were used during the brazing process. VFG was prepared by plasma enhanced chemical vapor deposition (PECVD) method in this study. The microstructure and the chemical state of the surface of the VFG and the joint were characterized by scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, and Raman spectroscopy. Results revealed that the in-situ and uniform distribution of (Ti,Nb)₂Ni particles and annular (Ti,Nb)C phases in the joint seam, effectively reduced the coefficient of thermal expansion of the joint seam and relieved the residual stresses in the joint. Meanwhile, the evenly distributed Nb solid solution endowed sound plasticity at high temperature to the joint seam. The shear strength of the joint at 1 000 ℃ reached 33 MPa, which is 450% higher than the directly brazed joint without interlayer.