Collision of nanoparticles of covalently bound atoms. Impact of stress-dependent adhesion

TL;DR

This paper investigates the impact of covalently bonded nanoparticle collisions, revealing stress-dependent adhesion effects and developing a theory that accurately predicts critical velocities for bouncing or aggregation.

Contribution

It introduces a novel stress-dependent adhesion phenomenon and provides a theoretical model that aligns well with numerical simulations for covalent nanoparticle collisions.

Findings

Stress-dependent adhesion coefficient increases linearly with maximal stress.

Critical velocity for collision depends on nanoparticle radius.

Elastic moduli of amorphous carbon nanoparticles match experimental data.

Abstract

The impact of nanoparticles (NPs) comprised of atoms with covalent bonding is investigated numerically and theoretically. We use recent models of covalent bonding of carbon atoms and elaborate a numerical model of amorphous carbon (a-C) NPs, which may be applied for modelling soot particles. We compute the elastic moduli of the a-C material which agree well with the available data. We reveal an interesting novel phenomenon - stress dependent adhesion, which refers to stress-enhanced formation of covalent bonds between contacting surfaces. We observe that the effective adhesion coefficient linearly depends on the maximal stress between the surfaces and explain this dependence. We compute the normal restitution coefficient for colliding NPs and explore the dependence of the critical velocity, demarcating bouncing and aggregative collisions, on the NP radius. Using the obtained elastic and stress-dependent adhesive coefficients we develop a theory for the critical velocity. The predictions of the theory agree very well with the simulation results.