TiAl₃-TiN Composite Nanoparticles Produced by Hydrogen Plasma-Metal Reaction: Synthesis, Passivation, and Characterization.

TiAl₃ and TiN composite nanoparticles were continuously synthesized from Ti-48Al master alloy by hydrogen plasma-metal reaction in a N₂, H₂ and Ar atmosphere. The phase, morphology, and size of the nanoparticles were studied by X-ray diffraction (XRD) and transmission electronic microscopy (TEM). X-ray photoelectron spectroscopy (XPS) and evolved gas analysis (EGA) were used to analyze the surface phase constitution and oxygen content of the nanoparticles. The as-synthesized nanopowders were mainly composed of nearly spherical TiAl₃ and tetragonal TiN phases, with a mean diameter of ~42 nm and mass fractions of 49.1% and 24.3%, respectively. Passivation in the atmosphere of Ar and O₂ for 24 h at room temperature led to the formation of amorphous Al₂O₃ shells on the TiAl₃ particle surface, with a mean thickness of ~5.0 nm and a mass fraction of ~23.5%, as well as TiO₂ with a mass fraction of ~3.2%.