Experimental and theoretical study on air reaction wetting and brazing of Si3N4 ceramic by Ag-CuO filler metal: Performance and interfacial behavior

Reactive air brazing of Si 3 N 4 ceramic was successfully achieved by using Ag-CuO filler metal. The effects of CuO content on the wettability of Ag-CuO/Si 3 N 4 system and the shear strength of Si 3 N 4 /Si 3 N 4 joint were investigated, and meanwhile the interfacial behavior was analyzed and discussed. Moreover, the work of adhesion, interfacial energy, and electronic properties of Ag/Si 3 N 4 , Ag/CuO and Ag/SiO 2 interfaces were evaluated by first-principles calculations. The Ag-CuO/Si 3 N 4 system transforms from no-wetting into wetting due to the oxidation of Si 3 N 4 substrate and the formation of SiO 2 layer on the substrate surface. The maximum average joint shear strength of over 50 MPa is obtained as the CuO content is 8 at.%. Compared with the Ag(111)/Si 3 N 4 (0001) interface, the Ag(110)/CuO(001) and Ag(110)/SiO 2 (001) interfaces show stronger interfacial bonding due to the formation of Ag-O ionic bond, indicating that the addition of CuO and the formation of SiO 2 contribute to the enhancement of interfacial bonding.