Understanding interfacial dynamics: Hydrostatic pressure-induced sono-dispersion of carbon nanotubes

Abstract

Homogeneously dispersing carbon nanotubes (CNTs) is crucial for minimizing agglomeration issues commonly encountered in commercially available CNTs samples, thereby enhancing their unique mechanical, electrical, thermal, and optical properties. In this study, we propose an alternative hydrostatic pressure-driven dispersion approach to effectively disperse CNTs and assess the impact of hydrostatic pressure on CNTs dispersion in deionized water (DIW). Our results demonstrate that ultrasonic treatment under a hydrostatic pressure of 0.1 MPa enables the achievement of a high concentration of multi-walled carbon nanotubes (MWCNTs) at approximately 4.23 mg/ml, significantly surpassing concentrations reported in recent studies (∼1.9 mg/ml). Thin buckypaper generated from these solutions exhibit exceptional electrical conductivity (∼4938 S/m). Numerical modeling demonstrates that the shock wave induced by bubble implosion is significantly enhanced, reaching 80 MPa under hydrostatic pressure, markedly higher than atmospheric pressure in previous studies (∼1.6 MPa). This enhancement leads to a twofold improvement in dispersion efficiency. For the first time, we reveal the underlying mechanism of nanobubbles (NBs) in dispersion stability. Our experimental results show a significant increase in the generation of NBs resulting from ultrasonic bubble collapse under hydrostatic pressure. This phenomenon plays a crucial role in the long-term stabilization of dispersion, which we observed over several months. The presence of negatively charged hydroxyl groups on the interface of the NBs is identified as a key factor in this stabilization process. The hydrostatic pressure-driven dispersion approach presented is essential for the large-scale dispersion of CNTs and other nanomaterials.