Enhanced In-Plane Thermal Conductivity and Mechanical Strength of Flexible Films by Aligning and Interconnecting Si3N4 Nanowires

Asthe rapid development of advanced foldable electronic devices,flexible and insulating composite films with ultra-high in-plane thermalconductivity have received increasing attention as thermal managementmaterials. Silicon nitride nanowires (Si(3)N(4)NWs)have been considered as promising fillers for preparing anisotropicthermally conductive composite films due to their extremely high thermalconductivity, low dielectric properties, and excellent mechanicalproperties. However, an efficient approach to synthesize Si(3)N(4)NWs in a large scale still need to be explored. In thiswork, large quantities of Si(3)N(4)NWs were successfullyprepared using a modified CRN method, presenting the advantages ofhigh aspect ratio, high purity, and easy collection. On the basis,the super-flexible PVA/Si(3)N(4)NWs composite filmswere further prepared with the assistance of vacuum filtration method.Due to the highly oriented Si(3)N(4)NWs interconnectedto form a complete phonon transport network in the horizontal direction,the composite films exhibited a high in-plane thermal conductivityof 15.4 W & BULL;m(-1)& BULL;K-1. Theenhancement effect of Si(3)N(4)NWs on the compositethermal conductivity was further demonstrated by the actual heat transferprocess and finite element simulations. More significantly, the Si(3)N(4)NWs enabled the composite film presenting goodthermal stability, high electrical insulation, and excellent mechanicalstrength, which was beneficial for thermal management applicationsin modern electronic devices.