Imaging and quantification of hydrogen isotope trapping.

Abstract

The location of hydrogen isotopes is imaged in austenitic stainless steel and model materials using local-electrode atom-probe (LEAP) tomography and trapping energies are measured by thermal desorption spectroscopy. LEAP tomography has sub-nanometer resolution and excellent compositional sensitivity due to pulse counting techniques. Site-specific sample preparation is possible using focused-ion beam, enabling us to show trapping at low density features, such as 4 grain boundaries in a model materials (commercially pure nickel and ultra-fine-grain Al-Mg). LEAP tomography is the only known technique to measure trapping to solute atoms (here, nitrogen in 21Cr-6Ni-9Mn austenitic stainless steel), and this report is the first use of the technique to image trapping in austenitic stainless steels. The experimental work is compared with first-principles calculations of the binding energy of hydrogen isotopes to solid solution nitrogen in stainless steels. 5 ACKNOWLEDGMENTS

Understanding and mitigating hydrogen embrittlement of steels: a review of experimental, modelling and design progress from atomistic to continuum

“…This, however, is usually limited to voltage-mode experiments, as the laser causes complex molecular species, such as ionised molecules of ð 1 HÞ 2 to form. Deuterium studies have been undertaken by several authors [59,64,90,156,204,208], often involving modifications to standard APT systems for introducing hydrogen into samples. These studies have shown that it is possible to image hydrogen within a range of materials; however, the APT is typically limited to only showing localised concentrations on the order of 20 at.…”

A multi-technique study of “barrier layer” nano-porosity in Zr oxides during corrosion and hydrogen pickup using (S)TEM, TKD, APT and NanoSIMS

“…The origins of 1 H + ions detected in the analysis volume is ambiguous because ambient hydrogen cannot be excluded from the atom probe analysis chamber and during the experiment can be attracted to the surface of the cold specimen, field evaporated and ultimately detected [39,40].…”

“…Although deuterium occurs naturally, its isotopic abundance is low (~0.015%), so if it is deliberately introduced into the treated specimen in place of hydrogen then any 2 D + ions detected in the APT analysis can be interpreted with confidence as being a real signal originating from constituent atoms in the specimen, rather than being introduced from external sources [40]. The availability of samples given a second corrosion process in a heavy water autoclave provides us with material spiked with deuterium for a known time and at a defined stage of the oxidation process.…”

Some Advances on Antagonist Effects of Grain Boundaries between the Trapping Process and the Fast Diffusion Path Investigated on Nickel Bicrystals

“…Additionally, SIMS mapping 29,[34][35][36] and recent Atom Probe Tomography observations 37 highlight a gradient of hydrogen content with a path length higher than the GBs thickness which suggests that hydrogen diffusivity and segregation processes cannot be only discussed in relation to the local structure of grain boundaries.…”