Simultaneously improved permittivity and breakdown strength, accompanied with reduced dielectric loss and conductivity, are difficult to achieve in polymer nanocomposites with conductive fillers by blending to construct a homogeneous structure. In this work, an MXene/fluoropolymer nanocomposite with a gradient sandwich structure has been prepared by casting various polymer solutions thrice, followed by annealing. Unfunctionalized Ti₃C₂T_x MXene nanosheets with lower conductivity and higher Young's modulus compared to graphene nanosheets have been utilized as fillers. Polyvinylidene fluoride (PVDF) has been employed as the polymer matrix. High interface compatibility between MXene and PVDF, as well as between the adjacent two sub-layers in the sandwich composite, has been obtained due to effects of p–π conjugation, hydrogen bond and similarity compatibility, leading to enhanced interface polarization and improved permittivity. The interface barrier effect between the neighboring two sub-layers restrains electric tree growth, resulting in elevated breakdown strength. Compared with mono-layered composites and PVDF, the sandwich composite shows improved comprehensive electrical properties. It has a permittivity of ∼26 at 100 Hz, a breakdown strength of ∼350 MV m⁻¹ and an energy density (efficiency) of ∼12.5 J cm⁻³ (∼64%) at breakdown strength. This work might open the way for large-scale fabrication of promising nanocomposites with a high energy storage density.

A high relative permittivity and breakdown strength are important to the high energy storage of dielectrics. However, in homogeneous composites, electric tree growth leads to premature breakdown. The thermal breakdown of a polymer matrix from excessive heat accumulation results in a low breakdown strength of the composites. In this work, polymer/2D MXene/2D BN nanocomposites were fabricated in a sandwich construction. Ti₃C₂ nanosheets with a high electric conductivity and stiffness, as well as hexagonal BN (h-BN) nanosheets with an ultrahigh thermal conductivity and breakdown strength, were employed as fillers. Polyvinylidene fluoride (PVDF) was used as the matrix. A mild interface polarization between MXene and PVDF endows the composite with the desirable dielectric properties. Charge injection from the electrodes can be depressed owing to BN in two outer sub-layers, and electric tree growth across the thickness can be impeded due to the interface barrier effect between two adjacent sub-layers. A high breakdown property was obtained. An acceptable temperature-dependence of relative permittivity and breakdown strength was gained and is ascribed to heat evacuation from MXene and BN. The inhomogeneous composite is superior to the homogeneous counterpart. The optimized sandwich composite has a breakdown strength of 235 MV m⁻¹ and relative permittivity of 24@1 kHz at 140 °C. This work might open up the way for the large-scale preparation of promising composite dielectrics.

Bio-inspired superamphiphobicity, including high contact angles, low sliding angles and non-stick traits, in combination with high durability, such as strong wear resistance, pH endurance and mechanical properties, are difficult to simultaneously obtain in the large-scale fabrication of amphiphobic materials with the presently used blends of polymers and surface-modified hard inorganic nanoparticles. In the current work, a series of highly abrasion-resistant superamphiphobic membranes applicable in a wide pH range were fabricated by a facile vacuum filtration process from suspensions containing snake-shaped silica hybrid nanowires. Tetraethyl orthosilicate, trimethoxyoctadecylsilane and 2-perfluorooctylethyltrimethoxysilane monomers were hydrolyzed and condensed to yield silica nanowires through finely regulated anisotropic sol–gel growth in a water/oil emulsion. The snake-shaped morphology, aspect ratio and elemental distribution of the nanowires were tailored to endow them with strong self-assembly capacity due to capillary force action. As a result, a porous 3D network morphology and hierarchical structure were achieved across the entire membrane thickness based on the self-weaving behavior of the nanowires. Superamphiphobicity was acquired, including a maximum water contact angle (WCA) of ca. 162° and an oil contact angle (OCA) of ca. 155°. The water sliding angle (WSA) and oil sliding angle (OSA) were less than 5°. Desirable non-stick, anti-fouling, flexible and self-standing traits were obtained. Well-maintained superamphiphobicity was observed in a wide pH range (1 to 12). After 300 abrasion cycles, the superamphiphobicity was retained due to the porous 3D network morphology and hierarchical structure across the whole membrane thickness. Therefore, excellent superamphiphobicity and damage tolerance were finely balanced on the surfaces of these nanowire membranes. This work may enable large-scale preparation of promising superamphiphobic surfaces.

Using V ₂ C-CNT switchboard-like hybrid particles as filler for preparing promising composite dielectrics based on fluorine-migration effect.