Ultrasound for dispersion of nanopowders

Citation

(2004), "Ultrasound for dispersion of nanopowders", Pigment & Resin Technology, Vol. 33 No. 6. https://doi.org/10.1108/prt.2004.12933fab.001

Ultrasound for dispersion of nanopowders

Ultrasound for dispersion of nanopowders

Keywords: Powders, Dispersions, Ultrasonics

Dispersion, deagglomeration of powders and the reduction of primary particles in micron and submicron range is required in many industrial processes. Powder of any particle size tends to form agglomerates when being mixed into a liquid. Therefore effective means of deagglomerating and dispersing are required to overcome the bonding forces after wettening the micron-powder or nano-powder.

For this application, Hielscher says that ultrasound has proven to be more effective than many other devices, such as rotor stator mixers (e.g. ultra turrax), piston homogenisers, gear pumps or beat mills, colloid mills and ball mills.

Dispersion by ultrasound is a consequence of microturbulences caused by fluctuation of pressure and cavitation. Investigations at different materials, such as aqueous solutions of nanoparticulate siliciumdioxid powder and spray frozen agglomerates with a variable solid content, have demonstrated the considerable advantage of Hielscher ultrasound equipment when compared with other technologies, reports the company.

Micron-size and nano-size materials down to the size of several nanometers are favoured for many applications due to their large surface area. An increase in available surface area can result in the increase of the reactivity of reagents and catalysts. The ultrasonic breakup of the agglomerate structures in aqueous and non-aqueous suspensions allows to utilise the full potential of such materials.

Hielscher says ultrasound does so on a more energy and cost-effective basis. In addition to that, ultrasonic systems can be run at fairly high concentrations. For example, for silica the breakage rate was found to be independent of the solid concentration up to 50 percent by weight.

Hielscher ultrasonic processors and flow cells for deagglomeration and dispersion are available for laboratory and production level. The industrial systems can easily be retrofitted to work inline. For the research and for the testing of this process as well as for many sonochemical processes laboratory devices or the UIP1000 set are recommended.