A High-Temperature Reducing Jet Reactor for Flame-Based Metal Nanoparticle Production

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. In particular, here we have produced carbon-coated copper nanoparticles from an aqueous copper formate precursor solution and characterized them by aerosol mobility distribution measurements, electron microscopy, and x-ray diffraction. Copper serves here as a prototype for non-oxide materials that are generally difficult to produce in flame-based reactors. This work demonstrates that such materials can be produced in substantial quantities with particle diameters below 50 nm in this new process.