|Ultrasonic Devices to Disperse Nanomaterials|
Nanomaterials have become an integral component of products as diverse as sunscreens, performance coatings, or plastic composites. Ultrasonic cavitation is used to disperse nano-size particles into liquids, such as water, oil, solvents or resins.
UP200S ultrasonic homogenizer for particle dispersion
The application of ultrasonics to nanomaterials has manifold effects. The most obvious is the dispersing of materials in liquids in order to break particle agglomerates. Another process is the application of ultrasound during particle synthesis or precipitation. Generally, this leads to smaller particles and increased size uniformity. Ultrasonic cavitation improves the material transfer at particle surfaces, too. This effect can be used to improve surface functionalization of materials having a high specific surface area.
Nanomaterials, e.g. metal oxides, nanoclays or carbon nanotubes tend to be agglomerated when mixed into a liquid. Effective means of deagglomerating and dispersing are needed to overcome the bonding forces after wettening the powder. The ultrasonic breakup of the agglomerate structures in aqueous and non-aqueous suspensions allows utilizing the full potential of nanosize materials. Investigations at various dispersions of nanoparticulate agglomerates with a variable solid content have demonstrated the considerable advantage of ultrasound when compared with other technologies, such as rotor stator mixers (e.g. ultra turrax), piston homogenizers, or wet milling methods, e.g. bead mills or colloid mills. Hielscher ultrasonic systems can be run at fairly high solids concentrations. For example for silica the breakage rate was found to be independent of the solid concentration up to 50% by weight. Ultrasound can be applied for the dispersing of high concentration master-batches – processing low and high viscosity liquids. This makes ultrasound good processing solution for paints and coatings, based on different media, such as water, resin or oil.