EFFECT OF SURFACE COATING RATIO OF SURFACE-MODIFIED PARTICLES ON THE CONTACT POTENTIAL DIFFERENCE BETWEEN A POWDER BED AND A METAL

Experimental and theoretical studies have been conducted on the effect of the surface coating ratio of surface modified SiO2 particles on th e measurement of the contract potential difference between a powder be d and a metal. The applied potential, which is a characteristic proper ty of an electrostatic charge, and surface coating ratio have the same tendency in relation to the mixture ratio of fine to core particles. The surface coating ratio peaks at a certain mixture ratio. On scannin g electron microscope photographs, agglomerated particles are observed on core particle surfaces at a high mixture ratio. The surface coatin g ratio starts to decrease after peaking at a certain mixture ratio, b ecause the fine particles re-entrain. The experimental data agree well with the calculated results that take into account the sticking proba bility of the fine particles to the core particle surfaces. A theoreti cal equation is derived for the relationship between the surface coati ng ratio and the mixture ratio. The relationship between the angle of repose of powder and the mixture ratio indicates the same tendency as the relationship between the applied voltage and the mixture ratio.