Research on interface structure during nanowelding with molecular dynamics and experimental method

Abstract

The mechanism of nanowelding between single-walled carbon nanotubes (SWNTs) and Ni substrate was investigated by molecular dynamics (MD) and experimental method. The horizontal oriented nanowelding system composed of metal electrode and SWNT subsystem was built for simulation study. The dynamic process of nanowelding was described completely at atomistic length scales, and the evolution of welding interface structure under different temperature and time was revealed by MD method. Simulation results showed nanowelding could be accomplished at a temperature (1500 K) below the melting point of Ni (1726 K). The mechanism responsible for nanowelding was revealed as the result of the high-frequency ultrasonic energy softening the metal and causing plastic deformation of the metal under the clamping stress because of the 'acoustic softening effect.' Based on simulation results, reliable contact between SWNTs and Ni substrate was built under proper nanowelding parameters by experiments. SWNTs were deposited on Ni substrate by electrophoretic deposition. The samples of sedimentary SWNT films were applied to ultrasonic nanowelding. Scanning electron microscopy results proved that SWNTs were embedded into the Ni metal layer and acted as stable filed emitter. The welded cathode exhibited enhanced field emission properties. The turn-on field of welded cathode decreased from 5.2 to 2.1 V/μm. By using nanowelding technique, high efficiency of preparing SWNT cathode is achieved and the progress in manufacturing large-scale of SWNT cathode is accelerated. Show more