Aluminum nitride (AlN) is a critical material in advanced electronics and structural applications due to its high thermal conductivity, excellent electrical insulation, and mechanical robustness. However, its integration into hybrid and composite systems unlocks new functionalities that surpass the limitations of standalone AlN. By combining AlN with polymers, metals, ceramics, or multilayered architectures, researchers have engineered materials with tailored properties for demanding applications in thermal management, electronic packaging, and high-performance structural components.

Polymer-AlN composites leverage the high thermal conductivity of AlN while maintaining the flexibility and processability of polymers. Thermally conductive polymer composites are essential for dissipating heat in electronic devices, where traditional metal heat sinks are unsuitable due to weight or electrical insulation requirements. AlN-filled epoxy resins, for example, achieve thermal conductivities exceeding 10 W/mK at filler loadings of 60-70 vol%. The dispersion of AlN particles within the polymer matrix is critical, as agglomeration can degrade mechanical properties. Surface modification of AlN particles with silane coupling agents improves interfacial adhesion, enhancing both thermal transfer and mechanical strength. Polyimide-AlN composites exhibit similar benefits, withstanding temperatures above 300°C while maintaining dielectric strengths suitable for high-voltage insulation. These materials are widely used in flexible printed circuit boards and encapsulation for power modules.

Ceramic-metal systems incorporating AlN offer unique combinations of thermal and mechanical performance. AlN-Al composites, fabricated through powder metallurgy or infiltration techniques, exhibit thermal conductivities approaching 200 W/mK, rivaling pure copper but with lower density and better dimensional stability. The percolation of metallic phases within the AlN matrix enhances fracture toughness, addressing the brittleness inherent in monolithic AlN. Similarly, AlN-Cu systems are employed in electronic substrates, where the coefficient of thermal expansion (CTE) can be tuned to match semiconductor materials like silicon or gallium arsenide. Direct bonded copper (DBC) substrates, formed by oxidizing AlN surfaces to create a strong bond with copper layers, are indispensable in high-power electronics. These substrates efficiently transfer heat while minimizing thermal stress-induced failures.

Multilayered structures exploit AlN’s properties in combination with other functional materials to achieve anisotropic behavior or multifunctionality. AlN-diamond laminates, for instance, capitalize on diamond’s ultrahigh thermal conductivity (over 2000 W/mK) while using AlN layers as diffusion barriers or electrical insulators. Such structures are pivotal in high-power laser diodes and RF amplifiers. Another example is AlN-silicon carbide (SiC) multilayers, where alternating layers provide graded CTE transitions, reducing interfacial stresses in extreme thermal cycling environments. Thin-film multilayers incorporating AlN as piezoelectric components are also prevalent in MEMS devices, where precise control over stress and acoustic properties is necessary for sensors and actuators.

The mechanical properties of AlN-based composites are significantly enhanced through careful microstructural engineering. In AlN-titanium systems, the formation of interfacial titanium nitride (TiN) during sintering improves bonding strength, leading to composites with fracture toughness values exceeding 5 MPa·m¹/². Similarly, AlN reinforced with carbon nanotubes (CNTs) demonstrates improved wear resistance and load-bearing capacity, making it suitable for cutting tools and aerospace components. The alignment of anisotropic fillers, such as hexagonal boron nitride (hBN) platelets within AlN matrices, further tailors mechanical anisotropy for specific directional strength requirements.

Thermal management remains a dominant application area for AlN composites. In high-brightness LED packaging, AlN-filled silicone gels provide both thermal dissipation and optical transparency, ensuring longevity and efficiency. The addition of AlN to aluminum or copper metal matrix composites (MMCs) enhances their heat spreading capabilities while reducing weight—critical for avionics and satellite systems. Phase-change materials (PCMs) embedded with AlN particles exhibit accelerated heat absorption and release rates, benefiting thermal energy storage systems.

Electrically functional AlN composites are emerging in advanced electronics. AlN’s wide bandgap (6.2 eV) makes it an ideal filler for insulating composites, but when combined with conductive phases like silver or graphene, it enables materials with tailored dielectric constants and loss tangents. These are vital for high-frequency communication devices requiring low signal attenuation. Piezoelectric AlN-polymer composites, where AlN particles are polarized within a flexible matrix, are used in energy harvesting and tactile sensors, converting mechanical vibrations into usable electrical signals.

Challenges persist in optimizing AlN composites, particularly in achieving uniform filler dispersion and minimizing interfacial defects. Advanced processing techniques like spark plasma sintering (SPS) and colloidal processing routes have shown promise in producing dense, homogenous composites with minimal porosity. Future directions include the development of bio-inspired AlN composites mimicking natural hierarchical structures for simultaneous mechanical resilience and thermal efficiency, as well as the integration of AlN into additive manufacturing workflows for complex, customized components.

In summary, hybrid and composite materials incorporating aluminum nitride represent a versatile platform for engineering solutions across thermal, mechanical, and electrical domains. By strategically combining AlN with polymers, metals, ceramics, or layered structures, researchers continue to push the boundaries of material performance, enabling next-generation technologies in electronics, aerospace, and energy systems.