Effect of Surface on Tuning the Properties of Platelet‐Like h‐BN Nanopowder via Oxidation

A systematic study of oxidation‐driven property modulation in platelet‐like h‐BN nanopowders subjected to controlled thermal treatments between 50°C and 800°C in air is carried out. Multimodal characterization by XRD, FTIR, and UV–Vis spectroscopies reveals a two‐stage transformation: (i) progressive disordering and hydroxyl removal below 500°C, linked to defect accumulation and partial oxidation from the nanoparticle side surfaces, and (ii) recrystallization with concurrent formation and intercalation of molten B 2 O 3 above 600°C. The anisotropic evolution of crystallite sizes and lattice strain demonstrates preferential c ‐axis recovery, while FTIR redshifts of the E 1u B–N stretching mode correlate with oxidation–induced bond distortion. Optical analysis shows a temperature‐dependent band gap narrowing from ≈5.9 to 5.4 eV, arising from both intrinsic lattice expansion and extrinsic B 2 O 3 formation. This work establishes a mechanistic link between surface chemistry, anisotropic structural recovery, and bandgap tuning in h‐BN, offering a controllable route to functional property engineering.