Abrupt elastic-to-plastic transition in pentagonal nanowires under bending

Area of Science:

• Materials Science
• Nanotechnology
• Mechanical Engineering

Background:

• Silver (Ag) and gold (Au) nanowires (NWs) are crucial for flexible electronics.
• Understanding their mechanical properties under strain is vital for device reliability.

Purpose of the Study:

• To investigate the bending behavior and mechanical transition of pentagonal Ag and Au NWs.
• To explore the effect of alumina coating on NW mechanical durability.

Main Methods:

• In-situ bending of Ag and Au NWs in a cantilever beam configuration within a scanning electron microscope (SEM).
• Observation and analysis of NW profile changes during bending.
• Comparison of coated and uncoated NWs under mechanical stress.

Main Results:

• An unusual, abrupt elastic-to-plastic transition was observed in uncoated NWs, characterized by a sudden change in bending profile.
• Unlike tensile or three-point bending, NWs did not fracture immediately after the plastic event, suggesting defect-blocking mechanisms.
• Alumina-coated NWs did not exhibit the abrupt transition and showed enhanced elastic deformation capabilities, possibly due to suppressed dislocation formation.

Conclusions:

• The five-fold twinned structure of NWs may lead to dislocation pile-up and sudden stress release, causing the abrupt plastic event.
• Alumina coating improves the mechanical durability of NWs by potentially preventing dislocation formation, enabling greater deformation without fracture.
• Enhanced mechanical durability is critical for Ag and Au NWs in applications involving high, inhomogeneous strain fields, such as in flexible conductive networks.