Multifunctional MXene/Aramid Nanofiber Composite Films for Efficient Electromagnetic Interference Shielding and Repeatable Early Fire Detection

[Image: see text] Rapid development of highly integrated electronic and telecommunication devices has led to urgent demands for electromagnetic interference (EMI) shielding materials that incorporate flame retardancy, and more desirably the early fire detection ability, due to the potential fire hazards caused by heat propagation and thermal failure of the devices during operation. Here, multifunctional flexible films having the main dual functions of high EMI shielding performance and repeatable fire detection ability are fabricated by vacuum filtration of the mixture of MXene and aramid nanofiber (ANF) suspensions. ANFs serve to reinforce MXene films via the formation of hydrogen bonding between the carbonyl groups of ANFs and the hydroxyl groups of MXene. When the ANF content is 20 wt %, the tensile strength of the film is increased from 24.6 MPa for a pure MXene film to 79.5 MPa, and such a composite film (9 μm thickness) exhibits a high EMI shielding effectiveness (SE) value of ∼40 dB and a specific SE (SSE) value of 4361.1 dB/mm. Upon fire exposure, the composite films can trigger the fire detection system within 10 s owing to the thermoelectric property of MXene. The self-extinguishing feature of ANFs ensures the structural integrity of the films during burning, thus allowing for continuous alarm signals. Moreover, the films also exhibit excellent Joule heating and photothermal conversion performances with rapid response and sufficient heating reliability.