Preparation of homogeneous, bulk nanocrystalline Ni/Mo alloys with tripled vickers hardness using flame-made metal nanoparticles

Metals and metal-alloys have been traditionally prepared by large-scale reduction and ore refining. The present work demonstrates how this reduction and alloying step can be executed within flame aerosol reactors on a sub-second time scale and gives access to metal-alloy nanoparticles of 10-50 nm size at high production rate. We demonstrate the preparation of Ni/Mo and Hastelloy like metal nanoparticles as examples for this process and showed that the product particles exhibited an exceptionally high air stability and narrow particle size distribution in comparison to presently accessible materials. Sintering and compaction gave access to centimeter-sized bulk nanocrystalline alloys with strongly enhanced Vickers hardness. The versatility of already broadly used aerosol processing of oxides suggests that the extension of flame synthesis to metals and alloys may offer an alternative for the preparation of multicomponent nanocrystalline metals.