title: Building a nano-crystalline α-alumina layer at a liquid metal/sapphire interface by ultrasound.
abstract: Transitional layers at the metal/ceramic interface play an very important role in ceramic joining. In this study, sapphire blocks were ultrasonically dipped in liquid Sn-Zn-Al alloy. It is found that the ultrasound promoted rapid oxidation reaction of aluminum at the Sn-Zn-Al/sapphire interface at 230°C in the ambient atmosphere, resulting in the formation of a nano-crystalline α-Al2O3 layer (NCAL). In a ∼2nm boundary layer of the NCAL, the lattice matches the sapphire substrate well. Thus, a smooth transition of the lattice from sapphire to metal was formed through the NCAL. Ultrasonically soldered sapphire joints were made with Sn-Zn-Al as the filler alloy. Compressive shear strength of the joints reached 43-48MPa, which is relatively high comparing to other Al2O3 joints made of Sn alloys doped with Ti or Rear Earth elements. Thus, a new mechanism of ultrasonic soldering, i.e. building an oxide transitional layer on the surface of the solid, was revealed. We expect this sonochemical process to be applicable to other metal/oxide systems.
authors.affiliation: State Key Laboratory of Advanced Welding and Joining, Harbin Institute of Technology, Harbin 150001, People's Republic of China. Electronic address: cui.wei.55711283500@gmail.com.
authors.forename: Wei
authors.initials: W
authors.lastname: Cui
authors.affiliation: State Key Laboratory of Advanced Welding and Joining, Harbin Institute of Technology, Harbin 150001, People's Republic of China. Electronic address: jcyan@hit.edu.cn.
authors.forename: Jiuchun
authors.initials: J
authors.lastname: Yan
authors.affiliation: State Key Laboratory of Advanced Welding and Joining, Harbin Institute of Technology, Harbin 150001, People's Republic of China.
authors.forename: Yan
authors.initials: Y
authors.lastname: Dai
authors.affiliation: State Key Laboratory of Advanced Welding and Joining, Harbin Institute of Technology, Harbin 150001, People's Republic of China.
authors.forename: Dandan
authors.initials: D
authors.lastname: Li
keywords: Alumina; Interfacial oxidation; Low temperature; Nano-crystalline layer; Ultrasonic