Effect of Proton Irradiation on the Defect Evolution of Zr/Nb Nanoscale Multilayers

Abstract

Nanoscale multilayer coatings (NMCs) with different crystal structures are considered as capable of self-healing after radiation damage due to the recombination of vacancies and interstitials. This work is focused on a defect distribution study of NMCs based on Zr/Nb layers (25/25 nm and 100/100 nm) after proton irradiation. Coatings with a total thickness of 1.05 ± 0.05 µm were irradiated by 900-keV protons using a pelletron-type electrostatic accelerator with an ion current of 2 µA for durations of 60 min to 120 min. The influence of the irradiation effect was studied by X-ray diffraction analysis (XRD), glow discharge optical emission spectrometry (GD–OES), and Doppler broadening spectroscopy using a variable energy positron beam. The results obtained by these methods are compatible and indicate that defect concentration of Zr/Nb NMCs remains unchanged or slightly decreases with increasing irradiation time.

First-Principles Calculations and Experimental Study of H+-Irradiated Zr/Nb Nanoscale Multilayer System

“…The main changes in the relative GD-OES curves are associated with the accumulation of hydrogen ions. The hydrogen concentration maximum occurs at a depth of ~800 nm, which corresponds to the Bragg peak for H + + ions, according to SRIM calculations [15]. Figure 8 shows a GD-OES profile of the Zr/Nb multilayer system consisting of five Zr-layers approximately 80 ± 10 nm thick and five Nb-layers with 100 ± 10 nm thickness, which agrees well with the STEM results (Figure 3).…”

“…The main changes in the relative GD-OES curves are associated with the accumulation of hydrogen ions. The hydrogen concentration maximum occurs at a depth of ~800 nm, which corresponds to the Bragg peak for H + ions, according to SRIM calculations [15]. The hydrogen distribution has a multimodal character, with local maxima of hydrogen concentration observed at the Nb/Zr interfaces, while the accumulation on Zr/Nb is much lower.…”

“…Specifically, the radiation resistance of Zr/Nb NMCs is actively investigated. Research of irradiation of NMC Zr/Nb by Si + [26], C + [28], Cu + [29], and H + [15] ions also shows high radiation resistance of such nanocomposites. Thus, irradiation by H + ions largely imitates neutron irradiation making nanocomposite NMS Zr/Nb potential material of active zones of nuclear reactors.…”

“…The recombination of vacancies and interstitial atoms takes place during irradiation in the incoherent interfaces [12,13]. Some examples of such systems are Cu/Nb [10], V/Ag [9], Cu/W [8], Zr/Nb [14][15][16][17], etc. For example, Cu/Nb nanolayers show very high stability under helium ion irradiation [18].…”

“…In contrast, only a few studies have discussed the first-principles calculations of irradiated Zr/Nb NMCs. Density functional theory (DFT) calculation can help analyze damaging mechanisms and strain distribution across Zr/Nb layers [15]. The incoherent Zr/Nb interfaces have been considered in [22,29], but there are no such calculations for the semi-coherent and coherent Zr/Nb interfaces.…”