AAAR 32nd Annual Conference
September 30 - October 4, 2013
Oregon Convention Center
Portland, Oregon, USA
Abstract View
Evolution of Particle Size Distribution of Pristine and Doped Titanium Dioxide in a Flame Reactor: Role of Various Process Parameters
JIAXI FANG, Yang Wang, Tandeep Chadha, MengMeng Yang, Pratim Biswas, Washington University in St Louis
Abstract Number: 281 Working Group: Nanoparticles and Materials Synthesis
Abstract Flame Aerosol Reactor (FLAR) technology is a single step widely utilized commercial methodology for synthesizing nanomaterials. Despite its commercial success, there is still a lack of complete understanding in the fundamental particle formation mechanisms in flames below 3 nm. Challenges in measuring particle size distributions in flames are partially due to difficulties in sampling caused by rapid timescales of aerosol processes such as nucleation, condensation, sintering, and coagulation. In addition particles below 3nm are difficult to measure due to previous limitations in instrumentation. Electrical mobility classification of sub 3nm particles suffer from particle losses due to diffusion and flow instabilities at higher sheath flow rates while condensation particle counters have low detection efficiencies below 3nm. It is widely known that size distributions below 3 nm are no longer continuous as particle diameters become discrete due to the presence of stable molecular clusters. Careful characterization of nanoparticles below 3 nm in a flame aerosol reactor has yet to be performed.
We report particle size distributions of TiO2 in a premixed methane-air flame aerosol reactor for both pristine titanium dioxide and the effects of adding copper dopants. Particles were classified with high resolving powers using a Half-Mini DMA and detected using a faraday cage electrometer. The Half-mini DMA was operated at extremely high sheath flow rates (up to 740 liters per minute) while maintaining laminar flow thereby minimizing diffusion losses during electrical mobility classification. The faraday cage electrometer enabled detection of singly charged particles below 2nm. The evolution of size distributions with respect to height in the flame was examined with respect to varying process parameters such as residence time, equivalence ratio, and precursor concentration. An understanding of these process parameters will be critical in the ability to commercialize and scale up flame aerosol reactors for new applications such as mixed component systems.