Positron Annihilation Spectroscopy Complex for Structural Defect Analysis in Metal-Hydrogen Systems

Area of Science:

• Materials Science
• Solid State Physics
• Physical Chemistry

Background:

• Metal-hydrogen systems are crucial for energy storage and catalysis.
• Understanding defect evolution during hydrogen cycling is vital for material stability.
• In situ characterization methods are needed to observe dynamic processes.

Purpose of the Study:

• To develop and validate a novel system for complex in situ research of metal-hydrogen systems.
• To investigate the defect structure of magnesium and magnesium hydride during thermal annealing.
• To assess the impact of hydrogen sorption-desorption cycles on material integrity.

Main Methods:

• Development of a controlled gas reactor with a unique reaction chamber.
• Integration of a radioisotope positron source and positron annihilation spectroscopy (PAS).
• Complementary analysis using scanning electron microscopy (SEM), X-ray diffraction (XRD), and hydrogen sorption-desorption measurements.

Main Results:

• The developed system enables in situ defect structure investigation at temperatures up to 900 °C and pressures up to 50 bar.
• One cycle of magnesium hydrogenation-dehydrogenation led to the accumulation of irreversible hydrogen-induced defects.
• PAS, SEM, XRD, and sorption studies provided a comprehensive understanding of the magnesium-hydrogen system.

Conclusions:

• The novel system is effective for in situ studies of metal-hydrogen interactions and defect evolution.
• Hydrogen cycling in magnesium results in permanent structural damage.
• Combined techniques offer a powerful approach to characterize hydrogen-affected materials.