Solid-electrolyte interphase (SEI) formation at highly ordered pyrolytic graphite (HOPG) surface has been studied with in-situ AFM. The morphology and thickness of both the top particle layer of the SEI and the bottom layer of the SEI that was caused by lithium insertion were investigated. The formation mechanism of the SEI was proposed accordingly. Ex-situ FESEM and EDS were also used to analyze the composition of the electrode after cycling to confirm the proposed mechanism.

Ultrasonic welding is a rapidly developing field. It is an industrial technique whereby high-frequency ultrasonic acoustic vibrations are locally applied to workpieces being pressed together to create a solid-state weld. A big advantage of ultrasonic welding is its efficiency of joining dissimilar thin metal sheets or foils used in battery, aerospace, and auto industry. The invention of more sophisticated and inexpensive equipment and increased demand have led to a growing knowledge of the fundamental process. However, many aspects of ultrasonic welding still require additional studies, such as better relating weld quality to process parameters. Inspecting the quality of the ultrasonic welding joints in-line also poses new challenges. Currently, destructive tensile test is one of the most effective ways to inspect the joint quality in laboratory, but it cannot be applied for in-line inspection. In this paper, the feasibility of using shearography technique for inspecting ultrasonic weld quality has been studied. A new shearography system with submillimeter resolution was designed, built, and tested. An extensive experimental study of ultrasonic welding nondestructive testing (NDT) was performed. The experimental results show that the effective welded area could be extracted from the shearography phase map. This paper shows that shearography is a potential technology for the NDT of ultrasonic welding.