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

Abstract Reactive air brazing of Si3N4 ceramic was successfully achieved by using Ag-CuO filler metal. The effects of CuO content on the wettability of Ag-CuO/Si3N4 system and the shear strength of Si3N4/Si3N4 joint were investigated, and meanwhile the interfacial behavior was analyzed and discussed. Moreover, the work of adhesion, interfacial energy, and electronic properties of Ag/Si3N4, Ag/CuO and Ag/SiO2 interfaces were evaluated by first-principles calculations. The Ag-CuO/Si3N4 system transforms from no-wetting into wetting due to the oxidation of Si3N4 substrate and the formation of SiO2 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)/Si3N4(0001) interface, the Ag(110)/CuO(001) and Ag(110)/SiO2(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 SiO2 contribute to the enhancement of interfacial bonding.