Enhanced interfacial strength in carbon-nanotubes-reinforced Al matrix composites via an interface substitution strategy

• An interface substitution strategy of replacing CNT-Al interface with a sandwiched CNT-ceramic-Al interface was proposed. • In-situ pullout tests demonstrated a high interfacial strength of 32.5 MPa for the SiO2@CNT-Al interface. • Interfacial strength was enhanced due to improved CNT-Al wettability and residual compressive stress introduced by coating. • Failure behavior and strengthening mechanism of sandwiched CNT-SiO2-Al interfaces were elucidated. The foremost concern when fabricating carbon nanotube (CNTs)-reinforced Al matrix composites is achieving appropriate interfacial bonding while avoiding intrinsic structural damage. In this study, an interface substitution strategy was developed for replacing the CNT-Al interface with a sandwiched CNT-ceramic-Al interface, thereby enhancing interfacial connections. A uniform, continuous SiO 2 layer was deposited on the CNT surface via a sol–gel process, followed by powder metallurgy routines to fabricate SiO 2 @CNTs/Al composites, in which the CNTs exhibited minimal structural damage and remained well-dispersed without interfacial reactions. An in situ pullout test demonstrated a high interfacial strength of 32.5 MPa for the SiO 2 @CNT-Al interface, attributed to the enhanced residual compressive stress and interfacial wettability. Consequently, the composite strength was significantly enhanced with CNTs addition, aligning well with predictions from the shear lag model. This interface substitution strategy underscored the feasibility of tuning the CNT-metal interfacial states and highlighted the potential for designing advanced nanocarbon/Al composites.