EN-MILD approach for Ti3C2Tx MXene synthesis with an ultrahigh electrical conductivity of about 2.4 × 104 S cm−1.

As a new class of two-dimensional materials, the MXene family has triggered attention because of its unique electrical and mechanical properties. MXene’s excellent electrical conductivity and hydrophilicity make it an ideal option for polymer nanocomposite fabrication. For the first time, polymer nanocomposites of polyvinyl alcohol (PVA)/Ti3C2T x (MXene) were used for charge storage applications in the X-band frequency range (8.2–12.4 GHz). By implementing solution casting and vacuum-assisted filtration (VAF), flexible thin films with exceptional dielectric properties (solution casting @ 10.0 wt % MXene: ε′ = 370.5 and tan δ = 0.11 and VAF @ 10.0 wt % MXene: ε′ = 3166 and tan δ = 0.09) were fabricated. The reported dielectric constants in this study are among the highest values obtained in X-band frequency with low dielectric losses. This outstanding performance originates from the high electrical conductivity of synthesized Ti3C2T x MXene (σ ≈ 1.4 ± 0.077 × 106 S/m; the highest reported value for Ti3C2T x MXene to date in the literature), great dispersion state, and the nacre-like structure of the polymer nanocomposites. Combining the exceptional properties of MXene with the effective nacre-like structure, PVA/MXene nanocomposites can be used as a novel charge storage material, fulfilling the requirements of flexible electronics and energy storage devices.

Carbon nanotube (CNT)/polymer nanocomposites exhibit excellent electrical properties by forming a percolated network. Adding a secondary filler can significantly affect the CNTs’ network, resulting in changing the electrical properties. In this work, we investigated the effect of adding manganese dioxide nanowires (MnO2NWs) as a secondary nanofiller on the CNTs’ network structure inside a poly(vinylidene fluoride) (PVDF) matrix. Incorporating MnO2NWs to PVDF/CNT samples produced a better state of dispersion of CNTs, as corroborated by light microscopy and transmission electron microscopy. The steady shear and oscillatory shear flows were employed to obtain a better insight into the nanofiller structure and viscoelastic behavior of the nanocomposites. The transient response under steady shear flow revealed that the stress overshoot of hybrid nanocomposites (two-fillers), PVDF/CNT/MnO2NWs, increased dramatically in comparison to binary nanocomposites (single-filler), PVDF/CNT and PVDF/MnO2NWs. This can be attributed to microstructural changes. Large amplitude oscillatory shear characterization was also performed to further investigate the effect of the secondary nanofiller on the nonlinear viscoelastic behavior of the samples. The nonlinear rheological observations were explained using quantitative nonlinear parameters [strain-stiffening ratio (S) and shear-thickening ratio (T)] and Lissajous-Bowditch plots. Results indicated that a more rigid nanofiller network was formed for the hybrid nanocomposites due to the better dispersion state of CNTs and this led to a more nonlinear viscoelastic behavior.

This study reports the fabrication of hybrid nanocomposites based on silver nanowire/manganese dioxide nanowire/poly(methyl methacrylate) (AgNW/MnONW/PMMA), using a solution casting technique, with outstanding dielectric permittivity and low dielectric loss. AgNW was synthesized using the hard-template technique, and MnONW was synthesized employing a hydrothermal method. The prepared AgNW:MnONW (2.0:1.0 vol %) hybrid nanocomposite showed a high dielectric permittivity (64 at 8.2 GHz) and low dielectric loss (0.31 at 8.2 GHz), which are among the best reported values in the literature in the X-band frequency range (8.2-12.4 GHz). The superior dielectric properties of the hybrid nanocomposites were attributed to (i) dimensionality match between the nanofillers, which increased their synergy, (ii) better dispersion state of AgNW in the presence of MnONW, (iii) positioning of ferroelectric MnONW in between AgNWs, which increased the dielectric permittivity of nanodielectrics, thereby increasing dielectric permittivity of the hybrid nanocomposites, (iv) barrier role of MnONW, i.e., cutting off the contact spots of AgNWs and leading to lower dielectric loss, and (v) AgNW aligned structure, which increased the effective surface area of AgNWs, as nanoelectrodes. Comparison of the dielectric properties of the developed hybrid nanocomposites with the literature highlights their great potential for flexible capacitors.