A new model for particle growth can predict the well known lognormal particle size distribution from first principles in a physically realistic way. The model is completely different from the usually applied coagulation models; it is based on a residence time approach, where the time available for the particles to grow determines the size distribution. The model is generally relevant in fields such as nanoparticle physics, aerosol science or environmental science, whenever particle growth occurs during transport through a growth zone due to diffusion and drift. Model predictions show excellent agreement with published experimental data obtained with the inert-gas evaporation technique.

https://iopscience.iop.org/article/10.1088/0957-4484/10/1/006/pdf

New approach to the origin of lognormal size distributions of nanoparticles

A new numerical approach for solving coagulation equation, TEMOM model, is first presented. In this model, the closure of the moment equations is approached using the Taylor-series expansion technique. Through constructing a system of three first-order ordinary differential equations, the most important indexes for describing aerosol dynamics, including particle number density, particle mass and geometric standard deviation, are easily obtained. This approach has no prior requirement for particle size spectrum, and the limitation existing in the log-normal distribution theory automatically disappears. This new approach is tested by comparing it with known accurate solutions both in the free molecular and the continuum regime. The results show that this new approach can be used to solve the particle general dynamic equation undergoing Brownian coagulation with sufficient accuracy, while less computational cost is needed.

A New Moment Method for Solving the Coagulation Equation for Particles in Brownian Motion

Aqueous suspension of fumed oxides, particle size distribution and zeta potential

The log-normal size distribution theory of brownian aerosol coagulation for the entire particle size range: Part I—analytical solution using the harmonic mean coagulation kernel

Magnetic nanoparticles with extremely high anisotropy such as chemically ordered L10 phase FePt nanoparticles have been considered one of the best candidates for future magnetic recording media with areal density beyond 1 Tbit/in2 for either the nanocomposite-film-type heat-assisted magnetic recording (HAMR) media or the self-organized-magnetic-array (SOMA)-type bit patterned media. However, current preparation methods via phase transformation must overcome many obstacles, including particle agglomeration, twinning, and difficulty of easy axis alignment. In this paper, the effort on and promise of the preparation of monodispersed magnetic nanoparticles with high anisotropy by a gas phase condensation method is reviewed and reported. The focus is to review recent progress on the fabrication of monodispersed highly ordered L10 phase FePt nanoparticles without phase transformation, successfully self-assembled and magnetically aligned magnetic nanoparticles for SOMA and HAMR media. The mechanisms for directly forming L10 phase FePt nanoparticles during nucleation and growth processes and magnetically aligning these particles are analyzed.

Y.J. Lee

Papers

The Log-Normal Size Distribution Theory for Brownian Coagulation in the Low Knudsen Number Regime