Ice-Templating Synthesis of Hierarchical and Anisotropic Silver-Nanowire-Fabric Aerogel and Its Application for Enhancing Thermal Energy Storage Composites

By bidirectionally freeze-casting silver nanowire (AgNW) suspension, we synthesized hierarchical AgNW aerogel (AgNWA). The AgNWA shows two hierarchical levels: (1) AgNW fabric-like ribbons of interlacing AgNWs and (2) axially and radially aligned assembly of AgNW ribbons. The AgNW ribbons are also connected by AgNW bridges. The AgNWAs have ultrahigh porosity (∼99.7%) and anisotropic electrical and thermal properties. Furthermore, AgNWA is used to enhance phase change materials (PCMs) for high-efficiency thermal energy storage. AgNWA-paraffin PCM nanocomposite was synthesized by infiltrating the AgNWA with paraffin. The PCM composite shows anisotropic electrical conductivity, ∼ 130% thermal-efficiency enhancement, and strong reliability against thermal cycling. Moreover, the effective PCM composite’s thermal capacity (latent heat) is also significantly enhanced, implying a strong AgNW-paraffin interfacial bonding. Thus, a hierarchical and anisotropic AgNWA is fabricated via a bidirectional freeze-casting technique, and it can largely enhance the performance and reliability of PCMs. This provides important insights into the design of oriented three-dimensional network of nanomaterials and also thermal energy storage composites with high performance and reliability.