High-energy ball milling of intermetallic Ti-Cu alloys for the preparation of oxide nanoparticles

Copper and titanium oxides in the nano-size range show unique chemical and physical properties and thus have been intensively considered for novel and smart applications. In this work, oxide nanoparticles were prepared by high-energy ball milling of Ti-Cu alloys followed by a controlled oxidation process. Alloys of the Ti-Cu system Ti-50Cu, Ti-57Cu, and Ti-65Cu (in wt.%) prepared by arc melting were selected considering they provide different starting brittle intermetallic phases before milling. Microstructural investigation indicated that Ti-50Cu was composed of Ti₂Cu and TiCu, while Ti-57Cu was single-phase TiCu. Ti-65Cu was dual-phase and consisted of Ti₃Cu₄ and Ti₂Cu_3. A mean particle size below 10 nm was achieved after high-energy ball milling for all compositions. The oxidation process was then investigated in two temperature ranges. At high oxidation temperatures of 700–800 °C, a complete oxidation took place leading to oxides TiO₂-rutile and CuO in all alloys. However, at a low oxidation temperature (350 °C), partial oxidation occurred and different oxides were obtained. Ti-50Cu was the most promising alloy and led to a mix of TiO₂ (rutile and anatase), CuO, Cu₂O, and Ti₃Cu₃O. After long exposure to thermal oxidation, the resulting oxides remained in the nanometric range with a particle size distribution showing a D50 of approximately 6 nm.