Time Evolution Of Particle Size Distribution Research Articles

The effects of model misspecification on shelf-life prediction of nano-sols under pH acceleration

ABSTRACT Shelf-life prediction of liquid-type (such as nano-sol) products is an interesting research topic. Recently, a pH acceleration method has been proposed in the literature to address the shelf-life prediction of nano-sol. The time evolution of particle-size distribution was obtained and modelled. There are two approaches for modelling the particle-size distribution, either by using a parametric approach (mixture-normal distribution) or a distribution-free approach. The main goal of this study is to quantify the seriousness of model misspecification on the shelf-life prediction when the true particle-size distribution follows a mixture-normal distribution, but wrongly treated it by a distribution-free model. The results demonstrated that the relative bias of shelf-life prediction may be under-estimated up to 13.66%, while its relative variability may be seriously inflated up to 13.35 times by using a distribution-free approach. The study shows that these effects of model misspecification are moderately large and cannot be neglected even when the sample size and the measurement times are small.

Model for predicting particle size evolution during nanoparticle aggregation in refrigerant–oil mixture

Nanorefrigerant–oil mixture is a promising energy-efficient refrigeration working fluid with superior thermophysical properties, and the prediction for its thermophysical properties requires the actual size of the particles in refrigerant–oil mixture. Due to the competitive adsorption of different liquid molecules on particle surface, the actual particle size of refrigerant–oil mixture cannot be predicted by the existing models developed for the nanofluids with single-component base fluid. This paper presents a model for predicting the particle size evolution during nanoparticle aggregation in refrigerant–oil mixture, considering the competitive adsorption behavior and its effects on particle movement and interaction. For model validation, the time-evolution of particle size distribution and the average size are calculated and compared with the existing experimental data. The model prediction agrees with 92% of the experimental data within deviation of ±10% and the mean deviation is 3.7%. In addition, the model can reflect the influences of oil mass fraction, initial particle concentration, primary nanoparticle diameter and temperature on particle size evolution. It is found that the adsorption layer has a significant effect on the aggregation behavior and the particle size evolution.

A Simulation Method to Predict Time-Evolution of Particle Size Distribution in Microemulsion Polymerization of Styrene

The method for simulating the time-evolution of the particle size distribution of polymer particles generated in the O/W microemulsion polymerization of styrene initiated by a water-soluble initiator is proposed based on the following kinetic model: The radicals generated in the aqueous phase enter the micelles, propagate therein and transform them into new polymer particles with (1) negligible bimolecular termination in the aqueous phase, and with (2) negligible entry of the second radical into the preformed polymer particles, and hence, (3) propagation of growing radicals stops only by a chain transfer reaction to monomer, (4) growth of polymer particles stops only by the desorption of the radicals generated by chain transfer out of the particles, and (5) the radicals produced by chain transfer may desorb from the particle or initiate propagation in the same particle. The average diameter calculated from the simulated particle size distribution agrees well with that measured experimentally by dynamic light scattering. The simulated particle size distribution agrees with that measured experimentally with a transmission electron microscope.