The waste MXene sediments (MXS) generated during the Ti 3 AlC 2 MAX etching process could not be further utilized, resulting in a significant waste of resources. Herein, the ice-template freeze-drying process was used to promote the spontaneous aggregation of waste MXS into 2D layers with micrometer-scale lateral dimensions. A polydopamine (PDA) layer was constructed on the MXS surface to enhance its mechanical strength while providing its abundant surface-active groups. The fibrillation of cellulose was achieved by deep eutectic solvent treatment of waste wood for lignin cleavage and further sodium chlorite bleaching process to obtain nanocellulose (NC). The low-speed ball-milling process was used to achieve homogeneous mixing and structural self-assembly between MXS@PDA and NC to achieve high value-added applications for MXS and wood materials. The polymer-based composites (named as NMP) with excellent photo-thermal conversion properties and mechanical stability were obtained by compounding NC/MXS@PDA with polyvinyl alcohol (PVA). The NMP-50 film has the tensile strength of 223.30 MPa and toughness of 5.99 MJ/m 3 , which are 110.78% and 252.35% higher than NC/PVA films. The introduction of NC/MXS@PDA reduces the wear rate of NMP films by 85.04%, resulting in an obvious increase in photothermal conversion efficiency and a significant improvement in thermal stability as compared to NC/PVA films. The strategy of preparing functionalized composites by MXS layers and NC self-assembly process provides a valuable reference for the preparation of high-strength and recyclable photothermal materials.
The development of flexible composites based on the transition metal carbides/nitrides (MXenes) is gaining popularity because of MXenes’ high application potentials for electromagnetic interference (EMI) shields. Here, we prepare a new type of ultraflexible composite films composed of “trashed” MXene sediment (MS) and waterborne polyurethane using a simple, facile solution casting approach. In addition to the outstanding mechanical strength and electrical conductivity, an extremely wide-range of MS contents can be achieved for the composites, resulting in EMI shielding effectiveness (SE) that may be controlled over a wide range. The X-band EMI SE of the flexible, low-density composites containing 70 wt % MS reaches 45.3 dB at a thickness of merely 0.51 mm. Moreover, the SE values of more than 34.5 dB in the ultrabroadband gigahertz frequency range including X-band, P-band, K-band, and R-band, are accomplished for the thin composites. Furthermore, the MS/WPU composite films show excellent electrothermal and photothermal performance, demonstrating the multifunctionalities of the MS-based EMI shields. Combined with the cost-efficient, sustainable, and scalable preparation approach, the ultraflexible, multifunctional composites from “trashed MXene” show great potentials for next-generation electronics. This work also opens a new avenue for the creation of innovative, high-performance, multifunctional flexible composites.
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