STUDY OF THE STRUCTURAL-PHASE STATE OF THE MECHANICALLY ACTIVATED SYSTEM Pd-Ti-Mg

This work examines the structural–phase state and microstructural organization of mechanically activated ternary Pd-Ti-Mg powders as candidate materials for solid-state hydrogen storage. Elemental powders were processed by high-energy planetary milling (Pulverisette 7, 500 rpm; BPR=10:1) in Ar. X-ray diffraction (Cu Kα) reveals fcc-Pd (Fm-3m, a=3.887 Å), α-Ti (hcp, P6₃/mmc, a=2.950 Å, c=4.681 Å), a metastable fcc-Ti fraction (Fm-3m, a=4.060 Å), and minor hcp-Mg (P63/mmc, a=3.209 Å, c=5.211 Å); no distinct intermetallic peaks are resolved at the bulk level. Laser diffraction shows a multimodal size distribution with D10≈5 µm, D50≈20 µm, D90≈50 µm (span≈2.25), a fine sub-5 µm mode, and a coarse 300-600 µm tail attributed to Mg. SEM-EDS mapping evidences a mosaic microstructure: isometric Pd-rich domains (~10-60 µm), platy Ti-rich fragments (~20–80 µm), local Pd-Ti colocalization at interfaces (interpreted as a prereaction state for Pd-Ti intermetallics), and predominantly intergranular, dispersed Mg. The combined data indicate abundant high-energy interfaces and shortened diffusion paths created by mechanical activation, which allows guidingfurther optimization of the structural state of the material for subsequent hydrogen-related investigation. while avoiding premature formation of bulk intermetallics. The results provide a microstructure-guided route to tune capacity, kinetics, and cycling stability via controlled milling parameters and targeted thermal schedules that promote beneficial Pd↔Ti interfacial reactions while limiting Mg segregation and oxidation.

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