Microstructures and interfacial behavior of Ag-CuO/AlN system by air wetting and brazing: Experiments and first-principles calculations

Reactive air wetting and brazing of AlN ceramic were performed using Ag-(0-20)at%CuO fillers. The wettability, joint mechanical properties and microstructural evolution were investigated, and the related surface energies, interfacial stability and electronic properties of Ag-CuO/AlN system were evaluated comprehensively by density functional theory (DFT) calculations. With the CuO content increasing, the contact angle of Ag-CuO/AlN system reduces significantly from over 120(degrees) to <10(degrees). The variation of joint strength is closely related to the formation of interfacial Al2O3 layer and the thickness of Ag layer, and the average shear strength of AlN/AlN joint arrives at the maximum of 57.5 MPa. Moreover, the DFT calculations demonstrate that the Ag(111)/ Al2O3(001) and Ag(111)/CuO(001) interfaces present stronger and more stable interfacial bonding than the Ag (111)/AlN(001) interface owing to the formation of O-Ag ionic bond, suggesting that the Ag/AlN interface can be effectively strengthened due to the addition of CuO and in-situ oxidation of AlN substrate.