Bidirectionally enhanced thermally conductive and mechanical properties MXene nanocomposite film via covalently bridged functionalized single-walled carbon nanotube

The development of thermal interface materials (TIMs) with excellent mechanical properties and efficient heat dissipation capability has become very necessary for the next generation of integrated electronics and flexible devices. Herein, a covalently cross-linked cellulose nanofiber/MXene/single-walled carbon nanotube (CNF/ MXene/SWCNT-KH550, K-CMC) nanocomposite film was successfully fabricated by vacuum-assisted self -assembly method. This unique cross-linked ternary narce-like structure greatly promoted the load transfer and energy dissipation between the components, thereby improving the mechanical properties of K-CMC nano composite films. CNF/MXene/2wt%SWCNT-KH550(K-CMC2) nanocomposite film exhibits superior tensile strength of 255.1 MPa and satisfactory toughness of 3.9 MJ/m3. Additionally, strong covalent cross-linking network also effectively promotes the transfer of phonons between the components, notably in both vertical and horizontal directions. The K-CMC2 nanocomposite film exhibits in-plane thermal conductivity of 25.06 W m-1 K-1 and through-plane thermal conductivity of 1.64 W m-1 K- 1, which enhanced 871% and 680% relative to the pure CNF film, respectively. The effective medium theory (EMT) proves that the formation of covalent cross-linked network effectively reduces the interfacial thermal resistance by 31.35%. These superior comprehensive properties endow the K-CMC nanocomposite films with great potential in the field of high power electronics.