Simulation of particle–vortex interactions in the modified chemical vapor deposition process

Germania nanocrystals in Modified Chemical Vapour Deposition

“…The wide range of particle sizes was also observed for Burner B with a non-rotating substrate (the only case considered for this burner). The absence of smaller soot particles in the rotating substrate case may be ascribed to the development, due to rotation, of vortices in the gas flow near the centre-line of the substrate tube [19]. Particles caught up in these vortices are carried to the end of the substrate tube without being deposited on the tube wall and are lost as waste material.…”

“…Where temperature is higher than $1250°C the reaction is reversible if Cl 2 is present and GeCl 4 and O 2 are produced which may be reconverted to GeO 2 if a lower temperature zone is encountered by the gas flow at a later stage. Where the temperature is lower than $1150°C GeCl 4 will remain unconverted unless gas flow vorticity [19] brings it into a region hot enough for reaction with oxygen to occur.…”

Simulation of particle transport and deposition in the modified chemical vapor deposition process

“…The model equations, the thermodynamic properties and diffusivity coefficients for the precursor reactants and products, as well as the reaction kinetics are identical to those used in the previous study [14]. (Note that [14] contains a typographic error and the heat of reaction is 251 kJ/mol and not 251 kJ/kg as printed.…”

“…However, such studies need extending to improve understanding of the particle deposition process for several reasons. Firstly, particle size was not considered, though it was found in our earlier work [14] that there is a large range of particle sizes. Secondly, complex internal interactions were not explored, nor were their influence on particle deposition patterns.…”

“…In order to isolate and predict the effect and importance of different system variables, a computational fluid dynamics (CFD) model was developed [14] to explore the generation-deposition pattern for SiO 2 soot particles as a function of tube rotation rate, particle density and particle size. This previous work focused on particle-vortex interactions and showed that the presence of complex double vortices plays a critical role in the particle deposition pattern.…”