A Low-Cost, Non-hazardous Protocol for Surface Texturing of Glass Particles

We present a cheap, efficient, and non-hazardous protocol for altering the roughness of hard particles at the nanometer-scale using a stone tumbler, a tool which is normally used for polishing stones. Six different textures were achieved by lining the tumbler with sandpaper of mean grit diameters dg=201, 58.5, 18.3, 12.6, and 8.4 mu m. Two textures were created by tumbling a batch of glass spheres for 4 h and for 12 h with the 12.6 mu m sandpaper; all other textures were established by tumbling for 12 h. Surface roughness was characterized by the integral length scale, xi, evaluated from 7 nm/pix resolution scanning electron microscope images. Roughness size increased from xi=24 to 31 nm as the grit size decreased from dg to 18.3 mu m and then decreased to xi=6.4nm at the smallest dg The largest xi(=34nm) was achieved using a 12.6 mu m sandpaper and the shorter tumbling time of 4 h. The permeability of a packed column of the particles broadly decreased with increasing xi, indicating that permeability decreases with increasing roughness size.