Engineering oxide-structured niobium composites via atomic layer deposition and spark plasma sintering

The precise control of nanoscale oxide dispersions offers a promising route to improve the mechanical performance of refractory metal systems. This study employs an atomic layer deposition (ALD)-based approach to deposit conformal TiO 2 nanocoatings on pure niobium powder surfaces using a rotary reactor, followed by densification via spark plasma sintering (SPS). During SPS consolidation, amorphous TiO 2 shells undergo phase transformation and redistribution, yielding crystalline rutile TiO 2 nanoparticles (10–20 nm) and interfacial Nb–Ti–O composite oxide phases localized along grain boundaries. Multiscale characterization confirms the spatial segregation and microstructural distribution of these phases. The ALD-derived oxide dispersoids suppress grain growth and impede dislocation motion, increasing hardness by up to 43 % in oxide-rich regions, as measured through nanoindentation. This strengthening arises from grain-boundary pinning, particle–dislocation interactions, and interfacial oxide stabilization, with the formation of Nb–Ti–O composite phases playing a notable role alongside discrete TiO 2 dispersoids. This study presents a scalable, contamination-free surface engineering strategy for fabricating nanostructured Nb-based composites with refined microstructures and enhanced room-temperature mechanical response. The approach offers a viable processing platform for refractory metal systems, with potential extension to high-temperature structural applications pending future thermal aging and mechanical evaluation at elevated temperatures .