h-BN-based lamellar films with ultralow dielectric constant and high thermal conductivity

The rapid development of artificial intelligence, the Internet of Things, and cloud computing has driven demand for high-performance chips. However, RC delay and limitations in heat dissipation have become major obstacles for the future design of high-end chips. Therefore, materials with ultralow dielectric constant and high thermal conductivity are highly desired. The major challenge in preparing such materials is that factors that promote a low dielectric constant often hinder improvements in thermal conductivity. In this work, we synergistically achieved an ultralow dielectric constant of 1.37 at 10 MHz and a high thermal conductivity of 19.65 W m⁻¹ K⁻¹ in a hexagonal boron nitride based lamellar composite film using boron nitride nanoflakes and one-dimensional nanofiber cellulose. These results are mainly attributed not only to the synergistic effects of low-polarizability functional groups and air gaps in lowering the dielectric constant, but also to the high crystallinity of the composite film, with parallelly stacked highly (0 0 2) oriented boron nitride nanoflakes, which promoted heat transport. Our research demonstrates the possibility of manufacturing a highly thermal conductive material without compromising its dielectric properties. The prepared composite films also exhibited excellent electrical insulation and mechanical properties. © 2025 The Author(s).