Evaporation-driven 3D CNT scaffolding for composite reinforcement

Abstract

The reinforcement of composites by carbon-nanotubes (CNTs) is typically limited by agglomeration and non-uniform dispersion. Thus, achieving a nanocomposite with high density of reinforcement material is a tough challenge. In this work, rather than mixing CNTs in a matrix, we first construct a dense CNT-network scaffold, and then impregnate it by the matrix to obtain a composite. To that end, we explore an evaporation-driven self-assembly approach to form 3D CNT scaffolds on quartz fibers, which combines high CNT density and nanoscale pore size with a straightforward, efficient process. The scaffold is thicker than the fiber by more than an order of magnitude, with a typical pore size of 70 nm and porosity of 60%. The strength of a scaffold-reinforced composite is evaluated by a fragmentation test. μCT 3D-reconstruction of the fragmented scaffold reveals that the matrix-impregnated scaffold creates a multiscale structure that under load behaves much like a fibrous composite. The fragmentation results are analyzed by a mechanical model, demonstrating a scaffold-composite strength of ∼200 MPa. The improved strength and relatively high CNT volume fraction (∼20%), along with the capability of tuning the scaffold thickness and density, make the proposed structure a promising prospect for composite reinforcement, as well as for diverse nanoscale applications.