Preparation of Nanostructured Microporous Metal Foams through Flow Induced Electroless Deposition

Monolithic nanostructured metallic porous structures with a hierarchy of pore size ranging from ca. 10 mu m to 1nm are processed for use as microreactors. The technique is based on flow induced electroless deposition of metals on a porous template known as PolyHIPE Polymer. The process is conducted in a purpose built flow reactor using a processing protocol to allow uniform and efficient metal deposition under flow. Nickel chloride and sodium hypophosphite were used as the metal and reducing agent, respectively. Electroless deposition occurs in the form of grains with a composition of NixPy in which the grain size range was ca. 20-0.2 mu m depending on the composition of the metal deposition solution. Structure formation in the monoliths starts with heat treatment above 600 degrees C resulting in the formation of a 3-dimensional network of capillary-like porous structures which form the walls of large arterial pores. These monoliths have a dense but porous surface providing mechanical strength for the monolith. The porous capillary-like arterial pore walls provide a large surface area for any catalytic activity. The mechanisms of metal deposition and nanostructure formation are evaluated using scanning electron microscopy, energy dispersive X-ray analysis, XRD, BET-surface area, and mercury intrusion porosimetry.