Aluminum nitride (AlN) ceramics are widely used in advanced electronic and thermal management applications due to their high thermal conductivity and favorable mechanical properties. However, achieving high densification and optimized mechanical performance remains a challenge during sintering. In this study, the effect of hexagonal boron nitride (h-BN) as a sintering additive on the sintering behavior, densification kinetics, microstructure, and mechanical properties of AlN ceramics was systematically investigated. High-purity AlN powders with varying h-BN contents were prepared via ball milling and consolidated using hot pressing at 1900 °C under a nitrogen atmosphere. The results reveal that increasing h-BN content reduces the required sintering temperature, attributed to the lubricating effect of h-BN that enhances particle rearrangement during sintering. An optimal h-BN concentration range (1-3 wt%) was identified, providing a favorable balance between densification rate and microstructural refinement. SEM analysis confirmed that h-BN addition significantly reduced porosity and promoted a more uniform and compact microstructure compared to monolithic AlN. Mechanical testing demonstrated a substantial improvement in tensile strength, with h-BN-reinforced AlN exhibiting an ultimate tensile strength of approximately 260 MPa, compared to 145 MPa for pure AlN. Although a slight reduction in ductility was observed, the enhanced stiffness and strength indicate effective load transfer and crack-bridging mechanisms introduced by h-BN.

Keywords: Aluminum nitride, Hexagonal boron nitride, Densification.