Defects, Corrugation and Temperature Govern Rarefied-Air Drag on Graphene Coatings

TL;DR

This study uses molecular dynamics simulations to demonstrate that graphene coatings on surfaces reduce gas-surface momentum exchange and drag in rarefied atmospheres, even with structural defects present.

Contribution

It reveals that graphene coatings significantly lower tangential momentum accommodation coefficient and drag, maintaining performance despite defects, in rarefied gas conditions.

Findings

Graphene coating reduces TMAC and drag on surfaces.

Performance persists at high temperatures and defect densities.

Benchmarking against graphite confirms similar effects.

Abstract

In rarefied atmospheric environments, where continuum fluid dynamics breaks down, aerodynamic drag is governed by gas-surface momentum exchange, making surface structure and chemistry key design knobs. Using molecular dynamics simulations, we show that coating the $\alpha$-Al2O3(0001) surface with graphene markedly reduces the tangential momentum accommodation coefficient (TMAC) of N2, shifting scattering toward more specular reflection and thereby lowering drag; we further benchmark this response against graphite. The reduction strengthens up to 900 K. While structural defects can increase TMAC via defect-induced corrugation and local atomic and electronic rearrangements, graphene retains its performance at experimentally relevant defect densities.