(232d) Functionalization of Ultrafine Particles by Atomic Layer Deposition in a Fluidized Bed Reactor

There are numerous applications for ultrafine particles having controlled surface properties while maintaining bulk materials properties. This functionalization of primary particles in the micron, submicron and nanometer size range is of particular interest. Self-limiting sequential Atomic Layer Deposition (ALD) surface chemical reactions allow the growth of nearly perfect films on primary particles. Films are pinhole-free, chemically bonded to the substrate particle surface and have a thickness controlled to within approximately 1 Å. The process is carried out in a scalable fluidized bed reactor which allows the processing of large quantities of powders. This presentation will focus on the self-limiting surface reaction processing and the ability to place nearly perfect nanothick films on primary particles that fluidize as dynamic aggregates. The fluidization of nanopowders will be shown using a pulsed laser imaging system. In addition, product gas analysis via an in-line mass spectrometer obtained in real time allows the surface reactions to be monitored continuously. It will be shown that a fluidized bed reactor provides for low cost rapid Particle ALD reaction processing with virtually no waste products being formed.