Atomic insights into thickness-dependent deformation mechanism and mechanical properties of Ag/PMMA ultra-thin nanofilms

Gaojian Lin; Wenpeng Gao; Pengwan Chen; Weifu Sun; Sergei A Chizhik; Alexander A Makhaniok; Galina B Melnikova; Tatiana A Kuznetsova

doi:10.1039/d3na00295k

Atomic insights into thickness-dependent deformation mechanism and mechanical properties of Ag/PMMA ultra-thin nanofilms

Nanoscale Adv. 2023 Aug 11;5(18):4934-4949. doi: 10.1039/d3na00295k. eCollection 2023 Sep 12.

Authors

Gaojian Lin^{1

2

3}, Wenpeng Gao^{1

2

3}, Pengwan Chen^{1

2

3}, Weifu Sun^{1

2

3}, Sergei A Chizhik⁴, Alexander A Makhaniok⁴, Galina B Melnikova⁴, Tatiana A Kuznetsova⁴

Affiliations

¹ State Key Laboratory of Explosion Science and Technology, School of Mechantronic Engineering, Beijing Institute of Technology Beijing 100081 China weifu.sun@bit.edu.cn.
² Beijing Institute of Technology Chongqing Innovation Center Chongqing 401120 China.
³ Explosion Protection and Emergency Disposal Technology Engineering Research Center of the Ministry of Education Beijing 10081 China.
⁴ A.V. Luikov Heat and Mass Transfer Institute of the National Academy of Sciences of Belarus Minsk 220072 Republic of Belarus.

Abstract

In this work, the nanoindentations on bilayer composite nanofilms composed of metal Ag and polymer PMMA were simulated using molecular dynamics. The effects of the thickness of Ag and PMMA on the elastic moduli of the composite films were analyzed from Hertz contact theory, dislocation evolution and atomic migration. The results show that the maximum penetration depth that the Hertz model could well describe is about 6 Å, and this limiting value is almost independent on the film thickness. The deformation mode of the Ag films gradually changes from bending mode to indentation mode with an increase in Ag thickness, which improves the elastic modulus of the composite films. The rule of mixtures could give a theoretical prediction about the elastic modulus of the composite film close to the nanoindentation, and Hertz theory could also be used as long as the thickness of Ag films exceeded a certain value. The introduction of a PMMA layer impedes the development of dislocation in the Ag layer and improves the elastic limit of the composite films. This work provides an important basis for experimentally measuring the overall elastic modulus of metal/polymer composite film based on nanoindentation or extracting the elastic modulus of metal film from the overall indentation response of the composite film.