Ultrafast sintering of boron nitride nanosheet assembled microspheres with strong processability for high-performance thermal management materials

Boron nitride nanosheet (BNNS)-based thermal management materials (TMMs) are increasingly vital in the rapidly evolving electronics industry but face limitations due to the anisotropic thermal conductivity of BNNS. Here, by ultrafast sintering, we synthesized cohesive BNNS microspheres (CBMs) with good processability and a strong ability to build isotropic thermally conductive pathways in various types of TMMs. This process produced the rapid fusion of BNNSs into spheres with a smooth surface, which weakens particle interactions and thus improves the ability to fill space including free-flowing properties (a low angle of repose of 21.6°) and dense packing behavior (a high tap density of 0.457 g cm⁻³). Additionally, such structure also allows for uniform distribution of stress under intense shearing, leading to a strong disintegration resistance which improves the processability and the quality of dispersal. By simple mixing, an isotropic thermal conductivity of 10.4 W m⁻¹ K⁻¹ was achieved with 65 wt% of CBM in the composite. Benefiting from its great processability and thermal conductivity enhancing ability, CBM was fabricated into various types of TMM such as pre-cured (pad), fluidic (grease), and in situ cured (adhesive, potting compound) products, all of which outperform industrial products. CBM represented a significant advancement in the development of high-performance TMMs, especially in high-efficiency fabrication and product diversity.