Mechanical Response of He-Implanted Amorphous SiOC/Crystalline Fe Nanolaminates

A Zare,M Nastasi,T A Harriman,L Shao,J Gigax,D A Lucca,Q Su

doi:10.1038/s41598-019-41226-w

Abstract

This study investigates the microstructural evolution and mechanical response of sputter-deposited amorphous silicon oxycarbide (SiOC)/crystalline Fe nanolaminates, a single layer SiOC film, and a single layer Fe film subjected to ion implantation at room temperature to obtain a maximum He concentration of 5 at. %. X-ray diffraction and transmission electron microscopy indicated no evidence of implantation-induced phase transformation or layer breakdown in the nanolaminates. Implantation resulted in the formation of He bubbles and an increase in the average size of the Fe grains in the individual Fe layers of the nanolaminates and the single layer Fe film, but the bubble density and grain size were found to be smaller in the former. By reducing the thicknesses of individual layers in the nanolaminates, bubble density and grain size were further decreased. No He bubbles were observed in the SiOC layers of the nanolaminates and the single layer SiOC film. Nanoindentation and scanning probe microscopy revealed an increase in the hardness of both single layer SiOC and Fe films after implantation. For the nanolaminates, changes in hardness were found to depend on the thicknesses of the individual layers, where reducing the layer thickness to 14 nm resulted in mitigation of implantation-induced hardening.

Highlights

In addition to crystalline/crystalline nanolaminates, there has been increasing interest in developing amorphous/crystalline nanolaminates composed of alternating amorphous and crystalline layers as irradiation tolerant materials
The present study aims to address this gap by evaluating the mechanical properties of silicon oxycarbide (SiOC)/Fe nanolaminates and films consisting of only SiOC or Fe before and after He implantation using nanoindentation and in-situ scanning probe microscopy (SPM)
Since irradiation damage is primarily produced by nuclear collisions between the incident ions and target atoms[28], the damage distribution is expected to be closely related to the distribution of implanted ions[29]

Summary

Introduction

In addition to crystalline/crystalline nanolaminates, there has been increasing interest in developing amorphous/crystalline nanolaminates composed of alternating amorphous and crystalline layers as irradiation tolerant materials. Studies have demonstrated that at low irradiation fluences, certain families of amorphous alloys exhibit better irradiation tolerance than crystalline metals, with no signs of He bubble formation, surface blistering, or flaking[8,14]. It was demonstrated that amorphous/crystalline nanolaminates consisting of amorphous SiOC/crystalline α-Fe have desirable structural stability over a range of irradiation/implantation conditions (i.e., ion species, energy, and temperature)[20,21,22,23]. Potential applications of these nanolaminates include advanced reactor designs and fuel cycle technologies[20,22,24]. The role of the amorphous/crystalline interfaces is investigated by studying nanolaminates with different thicknesses of individual layers

Methods

Results

Discussion

Conclusion