Determination of the minimum number of spacer particles ensuring non-contact between host particles — A new approach by numerical modelling

Abstract

The minimal number of spacer particles needed to ensure non-contact of host particles is of special interest with respect to the development of powders aiming at decreasing the interparticle forces between the host particles in order to ensure good flowability, dosing and fluidisation. As there is no detailed analytical approach available in literature of checking two host particles with respect to contact, even for the most simple system of monodisperse, spherical host particles covered by monodisperse, spherical guest particles, the present study is intended to give a sound mathematical solution to the question how many guest particles are minimally needed in order to ensure non-contact of host particles. This solution has been a numerical one up to now. In order to calculate this minimal coverage level a new computation model has been created and implemented in MATLAB®. The program performs three basic steps. The positioning of guest particles represented by imaginary point charges is carried out using Coulomb's Law leading to the uniform distribution of the guest particles on the host particle. In the second step circumcircles of every three guest particles are computed in order to find out the site where the host particles are most likely to get into contact. In the final step two host particles are checked for contact at this site. By multiple executions of these steps with modified numbers of guest particles, the minimal coverage is determined.