Investigation by STEM-EELS of helium density in nanobubbles formed in aged palladium tritides

TL;DR

This study uses STEM-EELS to measure helium density in nanobubbles within aged palladium tritide, revealing their pressure range and enabling differentiation from empty cavities.

Contribution

It demonstrates a novel application of STEM-EELS to quantify helium in nanobubbles, providing insights into their properties after long-term aging.

Findings

Helium densities range from 20 to 140 He/nm3.

Nanobubble pressures are between 0.1 and 3 GPa.

Helium mapping distinguishes bubbles from cavities.

Abstract

3He nanobubbles created by radioactive decay of tritium in palladium tritide are investigated after several years of aging. Scanning Transmission Electron Microscopy Electron Energy-Loss Spectroscopy (STEM-EELS) has been used to measure helium density from the helium K-edge around 23 eV. Helium densities were found between 20 and 140 (+/-30) He/nm3 and the corresponding nanobubble pressures range between 0.1 and 3 (+/-0.2) GPa. Measuring helium density and mapping He atoms by STEM-EELS enables to differentiate bubbles from empty cavities in the palladium tritide matrix.