The Role Of Ultrasonic Homogenizer in The Dispersion Of Nano-silica

The dispersion effect of ultrasonic homogenizers is mainly based on the "ultrasonic cavitation effect," which, in conjunction with mechanical shearing and acoustic flow disturbance, achieves particle refinement and dispersion. Its core mechanism can be divided into three stages: First, the ultrasonic generator produces high-frequency sound waves of 15kHz-1MHz, which are transmitted to the dispersion medium through an ultrasonic amplitude transformer (transmitter head). Second, as the sound waves propagate in the liquid medium, alternating high-pressure and low-pressure zones are formed. In the low-pressure zone, the liquid is stretched to form a large number of tiny vacuum bubbles (cavitation bubbles). These bubbles expand rapidly and collapse violently under the pressure of the high-pressure zone. Finally, at the moment of bubble collapse, shock waves with pressures up to thousands of atmospheres, high-speed microjets (speeds up to 100m/s), and local extreme temperatures (up to 5000K) are generated in a very small local area. These energies work together to break up and uniformly disperse the nano-silica aggregates in the medium. Compared with mechanical stirring, the particles are subjected to less mechanical impact force, are less likely to become flat, and can obtain a dispersion system with a pointed particle size distribution.

Nano-silica aggregates are classified into soft aggregates (formed by weak forces such as van der Waals forces and hydrogen bonds) and hard aggregates (formed by chemical bonds between particles). Traditional methods such as mechanical stirring and high-speed centrifugation are difficult to completely break down hard aggregates and are prone to secondary agglomeration. The cavitation effect and microjets generated by ultrasonic homogenizers can precisely act on the internal gaps of aggregates, tearing the aggregate structure from the inside like a "miniature hammer." Both soft and hard aggregates can be efficiently broken down into individual nano-silica particles or small-sized aggregates (usually dispersed to the original particle size level). For example, in the dispersion of nano-silica in aqueous solution, after ultrasonic homogenization, the originally agglomerated particles can be dispersed into a monodisperse system with uniform particle size. Laser particle size analyzer detection shows that the particle size distribution can be significantly narrowed, and the polydispersity index (PDI) can be reduced to below 0.2, fully utilizing the specific surface area advantage of nanoparticles. Meanwhile, the ultrasonic homogenizer can adjust parameters such as output power and amplitude according to the characteristics of the sample, adapting to the dispersion needs of nano-silica of different concentrations and media. Whether it is a small test tube sample in the laboratory or a high-viscosity slurry in industrial production, it can achieve efficient dispersion.

The dispersion effect of nano-silica directly determines the extent of its nano-effects and application value. Ultrasonic homogenizers, with their unique working mechanism based on cavitation, play a crucial role in breaking up agglomerates, inhibiting secondary agglomeration, optimizing dispersion uniformity, and assisting in surface modification, making them an indispensable key piece of equipment in the nano-silica dispersion process. Their high efficiency, energy saving, pollution-free operation, and strong adaptability have led to their widespread application in composite materials, coatings, cement, biomedicine, and other fields, effectively promoting the development of the nano-silica industry.