Restrained reshaping for ultra-compact, aligned, highly thermally conductive boron nitride nanosheet all-ceramic fibers

Abstract

The fabrication of compact, highly thermally conductive 2D material-based fibers has remained challenging due to difficulties in achieving both structural integrity and alignment. Here, we present a restrained reshaping process combined with ultrafast sintering to produce boron nitride nanosheet (BNNS) all-ceramic fibers (BACFs) with exceptional properties. The core restrained reshaping process converts uniaxial pressure into circumferential compression, enabling regulated deformation with continuous stress transfer. This approach yields fibers with a high relative density (86.4%) and superior BNNS alignment (Herman's orientation parameter = 0.789). The good densification and orientation facilitate BNNS fusion with enhanced grain contact during sintering, achieving a record-high thermal conductivity of 42.1 Wm⁻¹ K⁻¹ and excellent mechanical flexibility (bending radius <0.3 mm). The unique alignment of BNNSs in BACFs enhances both intra-fiber and inter-fiber thermal conductivity when woven into fabrics, demonstrating superior heat dissipation performance. This work establishes restrained reshaping as a scalable and versatile method for developing high-performance thermal management materials and dense 2D material-based fibers.