Tribo-charge and rebound characteristics of particles impact on inclined or rotating metal target

Tribo-charging of particles has been investigated with particular attention to the effect of impact velocity. The electrical current generated by impact of particles on an inclined or rotating metal target was measured for various impact angles by changing the tangential or normal component of impact velocity. It was found that the tribo-charging current had a maximum value at a certain impact angle. The particle rebound characteristics were also investigated in order to clarify the tribo-charging phenomena of such tendency. Experimentally obtained tangential restitution coefficient had a minimum value at a certain impact angle and increased to unity with the increase in impact angle. On the other hand, normal restitution coefficient had almost constant value up to a certain impact angle. Beyond this angle, the normal restitution coefficient increased sharply and finally exceeded unity. Translational energy loss normalized by initial translational energy had almost constant value as far as the impact angle is smaller than a certain angle. Beyond this critical angle, it decreased linearly to zero. This fact strongly suggests that the contact mode changes from rolling to slipping at this critical angle. Tribo-charging model refined by taking into the rolling and slipping of particle on the metal target agreed well with the experimental results.