Development of a New Aerosol Reactor for the Synthesis of Metal Nanoparticles

We present a new flame-based aerosol reactor configuration that combines thermal decomposition and hydrogen reduction to produce metal nanoparticles. This approach uses a fuel-rich hydrogen flame as a source of low-cost energy to initiate particle synthesis, but separates the flame chemistry from the particle formation chemistry. Hot combustion products pass through a nozzle to produce a high-temperature reducing jet. A liquid precursor solution is rapidly atomized, evaporated, and decomposed by the expanding jet, initiating particle formation. Particles are then quenched and collected downstream via filter.  We have produced several different metal nanoparticles including pure metals such as copper, silver, and gadolinium; alloys and multi-crystal particles such as copper/silver hybrids.  By modifying the liquid precursor injected into the reactor we can also produce controlled coatings on the particles.  An example of such a coating includes carbon on copper or silver.  Nanoparticles are characterized by aerosol mobility distribution measurements, electron microscopy, and x-ray diffraction.  Silver and copper serves here as a prototype for non-oxide material that is generally difficult to produce in flame-based reactors. This work demonstrates that such materials can be produced in substantial quantities with particle diameters below 20 nm using this new reactor technology.