Template free, large scale synthesis of cobalt nanowires using magnetic fields for alignment

The application of an external magnetic field on a metallic cobalt nanoparticle loaded exhaust gas stream produced by reducing flame synthesis resulted in the formation of self-aligned metallic cobalt nanowires of 20-50 nm diameter. This template free, continuous and rapid production method afforded nanowires with an aspect ratio of over 1000 (length/diameter) at a production rate of over 30 g h(-1). At high magnetic fields the nanowires formed bundles with distinctive parallel orientation. In the absence of a directing magnetic field, thermophoresis promoted an irregular growth and resulted in highly branched and porous nanomeshes on cooled, stainless steel collectors. The high production rates of this template free preparation method suggest application of the process for large scale manufacturing of magnetic nanomeshes for filtration or nanowires for magnetic storage and anisotropic functional materials.