Achieving sub-nanometre particle mapping with energy-filtered TEM

Area of Science:

• Materials Science
• Nanotechnology
• Analytical Chemistry

Background:

• Oxide dispersion strengthened (ODS) reduced activation FeCr alloys are crucial for future fusion reactors.
• Characterizing sub-nanometre particles in these alloys is essential for understanding their properties.
• Previous methods lacked the resolution to analyze such small particles.

Purpose of the Study:

• To develop and apply a novel method for chemical mapping of sub-nanometre particles.
• To characterize the nanoscale structure and composition of particles in ODS FeCr alloys.
• To investigate the impact of particle composition on alloy properties.

Main Methods:

• Utilized state-of-the-art energy-filtered transmission electron microscopy (EFTEM).
• Employed multivariate statistical analysis (MSA) for data reconstruction and signal isolation.
• Applied the technique to ODS reduced activation FeCr alloys.

Main Results:

• Successfully mapped the chemical composition of particles smaller than 1 nm.
• Identified a core-shell structure in most nanometer-sized particles.
• Observed an Yttrium-Chromium-Oxygen-rich core and a Chromium-Oxygen-rich shell.
• Found that nanoparticle segregation reduced dissolved Chromium in the matrix.

Conclusions:

• The developed EFTEM-MSA technique enables unprecedented chemical mapping of sub-nanometre particles.
• Nanoparticle composition and segregation in ODS FeCr alloys negatively affect matrix Chromium content.
• This finding has significant implications for the corrosion resistance and long-term performance of fusion reactor materials.