(159c) Computational Modeling of Silicon Nanoparticle Synthesis In a Laser-Driven Reactor

Synthesis of silicon nanoparticles is of great interest because of their unique optical and electronic properties. Fundamental understanding of the various interconnected mechanisms involved in the particle formation, such as gas phase and gas-surface phase chemical kinetics and particle size/morphology evolution through nucleation, growth, coagulation and coalescence, would be of great value in designing and optimizing processes for producing silicon nanoparticles. In this work, we modeled silicon nanoparticle synthesis by silane decomposition in a six-way cross laser driven aerosol reactor. This corresponds to a reactor system used in our laboratory. Because of the complexity of the problem at hand, the simulation was carried out via several sub-models. First, the chemically reacting flow inside the reactor was simulated in three dimensions in full geometric detail, but with no aerosol dynamics and with highly simplified chemistry. This was done using MPSalsa, a finite element program developed by Sandia National Laboratories. Second, the reaction zone was simulated using an axisymmetric 2-D MPSalsa model, whose boundary conditions were obtained from the first step. Last, a quasi-2-D aerosol dynamics model was used to study the silicon nanoparticle formation using more complete silane decomposition chemistry, together with the temperature and velocities extracted from the reaction zone simulation. Both moment-based and sectional models were used to describe the aerosol dynamics, and results will be compared. In addition, a bivariate moment model that models finite rate coalescence was applied, allowing realistic predictions of primary particle size at high particle number concentration.