Rheological Characteristics of 2D Titanium Carbide (MXene) Dispersions: A Guide for Processing MXenes

Abstract

Understanding the rheological properties of two-dimensional (2D) materials in suspension is critical for the development of various solution processing and manufacturing techniques. 2D carbides and nitrides (MXenes) constitute one of the largest families of 2D materials with >20 synthesized compositions and applications already ranging from energy storage to medicine to optoelectronics. However, in spite of a report on clay-like behavior, not much is known about their rheological response. In this study, rheological behavior of single- and multilayer TiCT in aqueous dispersions was investigated. Viscous and viscoelastic properties of MXene dispersions were studied over a variety of concentrations from colloidal dispersions to high loading slurries, showing that a multilayer MXene suspension with up to 70 wt % can exhibit flowability. Processing guidelines for the fabrication of MXene films, coatings, and fibers have been established based on the rheological properties. Surprisingly, high viscosity was observed at very low concentrations for solutions of single-layer MXene flakes. Single-layer colloidal solutions were found to exhibit partial elasticity even at the lowest tested concentrations (<0.20 mg/mL) due to the presence of strong surface charge and excellent hydrophilicity of MXene, making them amenable to fabrication at dilute concentrations. Overall, the findings of this study provide fundamental insights into the rheological response of this quickly growing 2D family of materials in aqueous environments as well as offer guidelines for processing of MXenes.

A Facile, High‐Yield, and Freeze‐and‐Thaw‐Assisted Approach to Fabricate MXene with Plentiful Wrinkles and Its Application in On‐Chip Micro‐Supercapacitors

“…More interestingly, FAT treatment can change the rheological property of m‐MXene. From Figure S6a,b, Supporting Information, after the FAT treatment, the gel‐like m‐MXene with high concentration (15 wt%) becomes flexible due to the decrease of viscosity and modulus, manifesting the appearance of a mass of single‐layer MXene with low viscosity and modulus, which can be observed by Cryo scanning electron microscopy (Cryo‐SEM) images in Figure S7, Supporting Information.…”

Two‐Dimensional Conjugated Aromatic Networks as High‐Site‐Density and Single‐Atom Electrocatalysts for the Oxygen Reduction Reaction

“…[3a, 4, 6c, 7] Owing to the natural M-N 4 high active sites,m etal phthalocyanine-based materials are widely studied for electrocatalysis and recognized as one of the most potential alternatives to noble materials. These novel 2D laminar CAN-Pc(M) materials were fabricated by exfoliating metal polyphthalocyanine (that is,FePPc, CoPPc, and FeCoPPc), in which the ORR-active Fe-N 4 and Co-N 4 sites were condensed in one conjugated plane via four aromatic rings.S imilar to other exfoliated materials (for example,g raphene, [9] MXene lamellar membranes [10] and graphitic carbon nitride [11] ), the 2D CAN-Pc(M) materials showed physical, electronic,a nd catalytic properties thatare unattainable in conventional counterparts (that is,polyphthalocyanine,p repared via the solid-phase synthesis [12] )a nd metal phthalocyanines (that is,F ePc and CoPc). These novel 2D laminar CAN-Pc(M) materials were fabricated by exfoliating metal polyphthalocyanine (that is,FePPc, CoPPc, and FeCoPPc), in which the ORR-active Fe-N 4 and Co-N 4 sites were condensed in one conjugated plane via four aromatic rings.S imilar to other exfoliated materials (for example,g raphene, [9] MXene lamellar membranes [10] and graphitic carbon nitride [11] ), the 2D CAN-Pc(M) materials showed physical, electronic,a nd catalytic properties thatare unattainable in conventional counterparts (that is,polyphthalocyanine,p repared via the solid-phase synthesis [12] )a nd metal phthalocyanines (that is,F ePc and CoPc).…”

Electrochromic Effect in Titanium Carbide MXene Thin Films Produced by Dip‐Coating

“…Due to the hydrophilic surface of MXenes, they can easily be processed in aqueous solutions at room temperature, [39] allowing deposition onto flexible and stretchable substrates. [40,41] Scalable techniques that produce uniform transparent MXene films on a substrate are necessary.…”