Ultrafast Thermal Conduction of Phase Change Fiber Enabled by Sheath Confinement-Induced Ordered Orientation of Hydroxylated BNNs.

Phase change fibers (PCFs) are increasingly popular in thermal storage and release applications, such as temperature management. However, a simple but effective integration of thermal conductive materials into PCFs to deliver ultrafast thermal conduction remains a big challenge. Herein, a facile one-pot coaxial wet spinning strategy based on sheath-confinement-induced orientation arrangement of hydroxylated boron nitride nanosheets (BNNs-OH) is proposed to fabricate the high-performance PCFs. For the core-sheath PCFs, the cellulose nanofiber (CNF)-reinforced paraffin (CNF/PW) emulsions serve as the phase change core, while the dissolved cellulose and well-dispersed BNNs-OH act as the sheath precursor. By increasing the extrusion speed of the liquid core, the contraction of the fiber sheath is gradually finalized to induce the alignment of BNNs-OH based on the confinement effect. Consequently, the highly oriented BNNs-OH nanosheets in fiber sheath (f = 0.8) endow PCFs with high phase transition enthalpy (125.1 J g), excellent thermal conductivity (10.15 W mK), rapid heat transfer rate (1.6 cm s); moreover, the as-prepared PCFs show good tensile strength (11.21 MPa) and leakage-proof (0.13%). The as-prepared PCFs are combined with thermochromic dyes for functional fabrics or applied as thermal management for a phone, demonstrating excellent thermal conduction and heat dissipation.