arXiv subjects

Maria Vrellou

Publications and source records attributed to Maria Vrellou.

4 recordsLinked to original sources

arXiv2026

Tritium as an Unambiguous Isotopic Tracer for Nanoscale Hydrogen Analysis by Atom Probe Tomography

Accurate nanoscale detection of hydrogen is essential for understanding hydrogen-related phenomena in materials, yet conventional deuterium tracing is often complicated by residual background hydrogen. This study evaluates tritium as an unambiguous isotopic marker for nanoscale hydrogen analysis in metals using atom probe tomography (APT). Titanium was selected for its ability to incorporate hydrogen isotopes, providing a suitable platform for tritium detection. Time-of-flight secondary ion mass spectrometry (ToF-SIMS) and electron backscatter diffraction (EBSD) were performed prior to tritium charging to characterize the initial composition and microstructure. APT analysis in laser-mode before and after tritium charging, at three post-charging intervals, enables tracking of tritium incorporation over time. Thermal desorption analysis (TDA) confirmed the presence of tritium and complemented the SIMS measurements, highlighting the role of the surface oxide layer in modulating tritium release. This work serves as a fundamental benchmarking study for leveraging tritium and APT as a combined tool for understanding the nanoscale location of hydrogen in materials, being relevant for interpreting local processes related to e.g., hydrogen embrittlement.

cond-mat.mtrl-sci↗

arXiv2025

Hydrogen response to high-density dislocations in bulk perovskite oxide SrTiO3

Hydrogen plays an increasingly important role in green energy technologies. For instance, proton-conducting oxides with high performance for fuel cell components or electrolysers need to be developed. However, this requires a fundamental understanding of hydrogen-defects interactions. While point defects and grain boundaries in oxides have been extensively studied, the role of dislocations as line defects remains less understood, primarily due to the challenge for effective dislocation engineering in brittle oxides. In this work, we demonstrate the impact of dislocations in bulk single-crystal perovskite oxide SrTiO3 on hydrogen uptake and diffusion using deuterium as tracer. Dislocations with a high density up to ~10 to the power of 14 per square meter were mechanically introduced at room temperature. Exposing this dislocation-rich and the reference regions (with a dislocation density of ~10 to the power of 10 per square meter) to deuterium at 400 {\deg}C for 1h, followed by secondary ion mass spectrometry measurements, we observed a ~100 times increase in deuterium incorporation in the dislocation-rich region. The result suggests that dislocations in oxides can act as an effective reservoir for deuterium. This proof-of-concept brings new insights into the emerging hydrogen-dislocation interactions in functional oxides.

cond-mat.mtrl-sci↗

arXiv2025

Drastic softening of Pd nanoparticles induced by hydrogen cycling

Single crystalline faceted Pd nanoparticles attached to a sapphire substrate were fabricated employing the solid state dewetting method. The as-dewetted nanoparticles tested in compression exhibited all features of dislocation nucleation-controlled plasticity, including the size effect on strength and ultrahigh compressive strength reaching up to 11 GPa. Hydrogen cycling of as-dewetted Pd nanoparticles resulted in their drastic softening and in change of the deformation mode. This softening effect was correlated with the high density of glissile dislocations observed in the cycled particles. This work demonstrates that the nanomechanical behavior of hydride-forming metals can be manipulated by hydrogen cycling.

cond-mat.mtrl-sci↗

arXiv2024

Towards establishing best practice in the analysis of hydrogen and deuterium by atom probe tomography

As hydrogen is touted as a key player in the decarbonization of modern society, it is critical to enable quantitative H analysis at high spatial resolution, if possible at the atomic scale. Indeed, H has a known deleterious impact on the mechanical properties (strength, ductility, toughness) of most materials that can hinder their use as part of the infrastructure of a hydrogen-based economy. Enabling H mapping, including local hydrogen concentration analyses at specific microstructural features, is essential for understanding the multiple ways that H affect the properties of materials, including for instance embrittlement mechanisms and their synergies, but also spatial mapping and quantification of hydrogen isotopes is essential to accurately predict tritium inventory of future fusion power plants, ensuring their safe and efficient operation for example. Atom probe tomography (APT) has the intrinsic capabilities for detecting hydrogen (H), and deuterium (D), and in principle the capacity for performing quantitative mapping of H within a material's microstructure. Yet the accuracy and precision of H analysis by APT remain affected by the influence of residual hydrogen from the ultra-high vacuum chamber that can obscure the signal of H from within the material, along with a complex field evaporation behavior. The present article reports the essence of discussions at a focused workshop held at the Max-Planck Institute for Sustainable Materials in April 2024. The workshop was organized to pave the way to establishing best practices in reporting APT data for the analysis of H. We first summarize the key aspects of the intricacies of H analysis by APT and propose a path for better reporting of the relevant data to support interpretation of APT-based H analysis in materials.

cond-mat.mtrl-sci↗