Nanofibers and nano-carbons, due to their excellent mechanical and thermal properties, hold immense potential in composite materials, electronic devices, and other fields. However, these nanomaterials, with their high surface energy and strong van der Waals forces, are prone to agglomeration in liquids, forming heterogeneous suspensions that severely limit their performance. Ultrasonic dispersion technology, with its unique physical effects, has become a core method for overcoming this challenge, paving the way for the efficient utilization of nanomaterial suspensions.
The core mechanism of ultrasonic dispersion originates from the cavitation effect in liquids. When high-frequency ultrasound waves, typically above 20kHz, are transmitted into a suspension, they induce alternating changes in positive and negative pressure, forming numerous microbubbles in the negative pressure zone. When these microbubbles rapidly collapse, they release localized high temperatures and pressures, generating strong impact forces and microjets that can precisely penetrate the gaps between nanoparticles, breaking up the agglomerated structure. This dispersion method combines high efficiency and uniformity; the uniform sound field of the high-frequency sound waves ensures that nanoparticles are evenly distributed throughout the system, avoiding localized agglomeration residues.
The value of ultrasonic dispersion is particularly prominent in the treatment of nano-carbon suspensions. Both single-walled carbon nanotubes and carbon nanofibers can be effectively dissociated using ultrasonic energy. Studies have shown that, with the addition of dispersants such as sodium carboxymethyl cellulose, and by controlling the ultrasonic amplitude at 40% and treating for 20 minutes, stable dispersion of carbon nanofibers in an aqueous system can be achieved. When this dispersion is used to prepare paper-based friction materials, it reduces the wear rate by 58%, increases the planar thermal conductivity by 9.1%, and significantly optimizes friction performance. For carbon nanotubes, the shear force generated by ultrasound can disrupt intermolecular forces, forming single or small bundle dispersions, laying the foundation for applications such as conductive inks and catalyst supports.
Ultrasonic dispersion of nanofiber suspensions is equally crucial. In the electrospinning process of preparing nanofibers, ultrasonic treatment of the spinning solution doped with carbon nanotubes ensures uniform distribution of carbon nanotubes within the fiber matrix, forming a reinforcing network structure and significantly improving the tensile strength and modulus of the fibers. Experiments have confirmed that ultrasonic parameters must be precisely matched to material properties. For example, high-power ultrasonic equipment can generate a stronger cavitation effect, resulting in a more ideal dispersion effect for high-concentration nanofiber suspensions; however, energy input must be controlled to avoid damage to the fiber structure.
Ultrasonic dispersion technology bridges the gap between nanomaterials and practical applications, achieving homogenization of suspension systems by regulating the cavitation effect. From paper-based materials to functional fibers, its application in the fields of nano-carbon and nanofibers demonstrates the material development logic of "breaking bottlenecks through technology," providing reliable support for the large-scale production of high-end nanocomposite materials.
