The degradation of vanadium-based alloys during hydrogen sorption cycles is closely linked to defect accumulation(e.g.,dislocation and lattice strain),yet the atomic-scale origins of such defects remain poorly underst...The degradation of vanadium-based alloys during hydrogen sorption cycles is closely linked to defect accumulation(e.g.,dislocation and lattice strain),yet the atomic-scale origins of such defects remain poorly understood.In present study,we reveal the crucial role of initial lattice distortion,quantified by the atomic size difference(δ),in the defect formation and accumulation of V-based alloys.Alloys with higherδvalues exhibit accelerated attenuation of reversible hydrogen capacity(13.22%forδ=4.32%vs.5.60%forδ=3.85%over 100 cycles),accompanied by increased plateau slope factors(Sf)and defect concentrations.High-resolution microscopy uncovers a two-stage defect evolution,associated with the generation of two types of nano-scale hierarchical structures.During the first cycle,nanograins with different spatial orientations show up,which geometrically leads to the formation of dislocations between the misoriented interfaces.In subsequent cycles,alternating nano-layered structures(1-2 nm thickness)gradually appear within the nanograins,resulting in the formation of subgrain boundaries accompanied with the local distortion and strains.These hierarchical nanostructures,driven byδ-dependent lattice distortion,are identified as the primary cause of the defects in alloys.This work provides a microstructure-guided strategy for designing durable hydrogen storage alloys by minimizing atomic size mismatch.展开更多
基金granted by the National Key R&D Program of China(No.2022YFB3803700)Sichuan Science and Technology Program(No.PG-PGFG-JFKF23-000009-0).
文摘The degradation of vanadium-based alloys during hydrogen sorption cycles is closely linked to defect accumulation(e.g.,dislocation and lattice strain),yet the atomic-scale origins of such defects remain poorly understood.In present study,we reveal the crucial role of initial lattice distortion,quantified by the atomic size difference(δ),in the defect formation and accumulation of V-based alloys.Alloys with higherδvalues exhibit accelerated attenuation of reversible hydrogen capacity(13.22%forδ=4.32%vs.5.60%forδ=3.85%over 100 cycles),accompanied by increased plateau slope factors(Sf)and defect concentrations.High-resolution microscopy uncovers a two-stage defect evolution,associated with the generation of two types of nano-scale hierarchical structures.During the first cycle,nanograins with different spatial orientations show up,which geometrically leads to the formation of dislocations between the misoriented interfaces.In subsequent cycles,alternating nano-layered structures(1-2 nm thickness)gradually appear within the nanograins,resulting in the formation of subgrain boundaries accompanied with the local distortion and strains.These hierarchical nanostructures,driven byδ-dependent lattice distortion,are identified as the primary cause of the defects in alloys.This work provides a microstructure-guided strategy for designing durable hydrogen storage alloys by minimizing atomic size mismatch.
