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Iodine oxide particle (IOP) growth modelling

Measured time-resolved particle size distribution data was used to develop a coagulational growth model which accounts for the growth of fractal IOP's with open, low density structures as observed (see laboratory work on IOP's) whilst taking into account inter-particle, short-range van der Waals interactions and hydrodynamic forces [Saunders and Plane, 2006b].

An example of the model fits to a time series of size distribution data is shown in Figure 5. The best-fit procedure allowed for estimation of the parameters of fractal dimension (Df) and primary particle size (r0) used to characterise all fractal forms.


Figure 5 Comparison of model fits (lines) to the measured distributions (discrete points) at the coagulation times indicated. Best-fit parameter values were as follows; r0 = 3.3 nm (all times), Df = 2.2 (20 s), 2.4 (45 s) and 2.5 (70, 95 and 120 s). For all fits, particle density was calculated from the relevant r0 and Df values and coagulation started at rn=1 = 0.30 nm, corresponding to the size of a single I2O5 molecule - Figure taken from Saunders and Plane (2006b)

The modelled value of Df = 2.5 at the longest growth times is consistent with the particle-cluster diffusion limited aggregation (DLA) mechanism.
References

Saunders, R.W., and J.M.C. Plane (2006b) Fractal growth modelling of I2O5 nanoparticles. J. Aerosol Sci., 37, 1737.
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