Silica particles with diameters in the range of
several micrometers comprised porous silica and nonporous
fused silica. The surface-adhered nanoparticles on both the
types of spherical silica particles were removed by ultrasonic
cleaning. On the basis of the obtained results, the influences of
surface-adhered nanoparticles and nanopores on the coefficient
of dynamic friction (CDF) and aggregation strength (AS) of the
bulk powder behavior and the relationship between bulk
behavior and microscopic particle interaction are discussed.