Ultrahigh Critical Current Density across Sliding Electrical Contacts in Structural Superlubric State

Area of Science:

• Materials Science
• Tribology
• Electrical Engineering

Background:

• Conventional sliding electrical contacts (SECs) face a trade-off between high critical current density (CCD) and low friction/wear.
• Structural superlubricity (SSL) offers a potential solution with its characteristics of zero wear, near-zero friction, and full atomic contact.

Purpose of the Study:

• To investigate the critical current density (CCD) of graphite surfaces under structural superlubricity (SSL) conditions.
• To evaluate the potential of SSL contacts for advanced sliding electrical contact applications.

Main Methods:

• Experimental measurement of current density on microscale graphite contact surfaces under sliding conditions.
• Raman spectroscopy for wear-free interface characterization.
• Analysis of the scaling relation of CCD to estimate intrinsic CCD.

Main Results:

• Achieved a measured current density of 17.5 GA/m², approximately 146 times higher than previously reported SECs.
• Observed a coefficient of friction below 0.01 and confirmed a wear-free interface via Raman characterization, indicating SSL.
• Estimated the intrinsic CCD of single crystalline graphite to be 6.69 GA/m², limited by Joule heating.

Conclusions:

• SSL contacts demonstrate exceptional performance in terms of high CCD and ultra-low friction/wear.
• Graphite-based SSL contacts hold significant promise for next-generation SECs, including micro/nanoswitches and conductive slip rings.