Titanium dioxide

By standard, we recommend using grinding balls about 10-20x larger than the largest present particle. The presented sample was only agglomerated. A pre-crushing with larger grinding balls was not required.

We recommend using zirconium oxide equipment to avoid discoloration. With steel or hardmetal tungsten carbide, abrasion would discolorate the sample rapidly.

For comminution, a motor oil like viscosity should be set. Too thick paste would slow down the grinding balls. With a too watery slurry, higher abrasion would be expected. For comminution, we added 100 grams of water.

To avoid over pressure, we ground in cycles of one minute of grinding time, followed by 12 minutes of programmed pausing time. The temperature of the bowl should remain smaller than the boiling point of the used liquid; else the programming of the mill needs to be readjusted.

We checked the present particle size distribution by static light scattering. We used our Laser Particle Sizer ANALYSETTE 22 NanoTec and Mie parameters to determine the level of fineness. Proper Mie parameters are required to determine particles in sub micrometer range. We used a refractive index of 2,63509 and an absorption coefficient of 0,01. If a more accurate Mie parameter can be provided, a recalculation of the result can be performed anytime.

After 15 minutes of total grinding time, we checked the particle size distribution and found a d50 <170 nm. The d90 value was < 250 nm and no particles > 400 nm were determined. The sample was separated by sieving. The grinding balls were washed several times to regain a maximum of sample. For higher amounts, the Planetary Mill PULVERISETTE 5 premium line can be equipped with 2x 500 ml bowls to maximize sample amounts.

Particles in sub micrometer range tend to reagglomerate rapidly. Please pretreat the returned sample with strong ultrasonic force several minutes before using. It can be beneficial to add a proper grinding agent for stabilization (e.g. surfactants; but also salts or pH buffers are often used to minimize reagglomeration).