Particle Formation in the Flame

The optimal situation would be to minimize unnecessary loss of surface area by freezing the sintering of aggregated Pt primary particles after a short residence time in the flame, before they become mixed up with carbon and ionomer particles. 

The ability to make thinner electrodes is usually advantageous for enhancing mass transport characteristics. In the case of NanoSpray Combustion-prepared materials, electrode layer thickness (20-25 pm) is not necessarily a determining factor of performance because the enhanced porosity allows for thicker electrodes without compromising mass transport behavior. 

In order to control particle size it is possible to use water or air to cool the flame. Cold air, provided from a water-cooled quenching ring, has been used to quench the aerosol coming out of the flame [78]. The quenching helps deerease the 

In the case of direct deposition onNafion substrate, since that is only stable at lower temperatures the flame must be cooled before it reaches the substrate surface. The NRC-IFCI was doing such cooling using an air knife system that cut the flame at a set distance from the nozzle body. The distance, angle, and position of the air knife system control the substrate temperature. In general, in the flame process there are several parameters fliat can be modified in order to optimize the platinum deposition process. These are  

Solvent type and concentration Propellant concentration Precursor concentration 

---