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Industrial scaleup of MXene synthesis has faced many challenges, both in the process safety and nanosheet yield. As a step toward the scalability of MXenes, we carried out a one-to-one comparison of the industrial scalability and application performance of two methods for producing Ti3C2Tz MXenes: LiF-HCl acid etching and Lewis acid molten salt etching. This study had an emphasis on nanoscale structure, electrical conductivity, electromagnetic interference (EMI) shielding and supercapacitive properties, yield, and process scalability, both at the etched clay stage and delaminated nanosheet stage. This comparison was completed in parallel with the same starting MAX phase, chemicals, and processing equipment, where necessary. The synthesis process influences the structure and terminal groups of MXenes, altering properties and performance. Notably, the electrical conductivity was superior for acid-etched nanosheets at 2200 S/cm, compared to salt-etched nanosheets at 0.66 S/cm. For EMI shielding effectiveness and capacitance, acid-etched nanosheets performed the highest. The yield of the acid-etched nanosheets was ~ 50% and salt-etched nanosheets was 15%. The acid-etched process was scaled up with a small business partner from 1-g to 200-g MAX phase, with similar properties and yield. When the salt-etching process was scaled up to 25 g of MAX, the properties remained similar to the 1 g batch, with a lower yield of ~ 5%. Although the acid-etching process was better for most metrics, the molten salt-etching method is still in its infancy and has advantages regarding process safety. 

In this work, we investigate how radio frequency heating of admixture of catalyst and RF susceptor can drive the propane dehydrogenation reaction, enabling distributed chemical manufacturing based on electric power rather than fossil fuel heating. 

Abstract Structural color arises from light scattering rather than organic pigments and can be found in Nature, such as in bird feathers and butterfly wings. Synthetic materials can mimic Nature by leveraging materials with contrasting optical characteristics by controlling each materials’ spatial arrangement in a heterostructure. Two-dimensional MXene nanosheets are particularly interesting due to their unique optical properties, but MXenes have not been used directly as a structural colorant because it is challenging to control the spatial placement of MXenes at the nanometer level. Here, we report the emergence of structural color in layer-by-layer (LbL) assemblies of Ti₃C₂T_zMXene nanosheets and polyelectrolyte heterostructures with controlled block thicknesses. The block thickness and spatial placement of MXene are controlled by the assembly’s salt concentration and number of layer pairs. This work demonstrates that optical characteristics of MXene/polyelectrolyte heterostructures depend on MXene content and placement, while deepening the understanding of MXenes within structural color films. 

The major challenge to fabricate MXene/polymer composites are the processing conditions and poor control over the distribution of the MXene nanosheets within the polymer matrix. Traditional ways involve the direct mix of fillers and polymers to form a random homogeneous composite, which leads to inefficient use of fillers. To address these challenges, researchers have focused on the development of ordered MXene/polymer composite structures using various fabrication strategies. In this review, we summarize recent advances of structured MXene/polymer composites and their processing-structure-property relationships. Two main forms of MXene/polymer composites (films and foams) are separately discussed with a focus on the detailed fabrication means and corresponding structures. These architected composites complement those in which MXenes nanosheets are isotropically dispersed throughout, such as those formed by aqueous solution mixing approaches. This review culminates in a perspective on the future opportunities for architected MXene/polymer composites. 

Radio-frequency (RF) heating of thermosetting epoxies is an agile method to decouple the extrudability of epoxy resins from their buildability for additive manufacturing. Through this method, the resin is extruded in the liquid state at the early stages of curing. Then, an RF applicator induces a rapid and uniform increase in temperature of the resin, accelerating the solidification of the printed feature. Understanding the evolution of the resin's RF heating response as it cures is therefore critical in meeting the demands of additive manufacturing. In this work, we show that the high-frequency dielectric loss, determined using in situ rheo-dielectric measurements, of both neat and carbon nanotube (CNT) filled resins is correlated to the heating response at different temperatures throughout curing. Furthermore, we show that the presence of CNTs within the resin augments the heating response and that their dispersion quality is critical to achieving rapid heating rates during the cure. 

Although surface terminations (such as ═O, –Cl, –F, and –OH) on MXene nanosheets strongly influence their functional properties, synthesis of MXenes with desired types and distribution of those terminations is still challenging. Here, it is demonstrated that thermal annealing helps in removing much of the terminal groups of molten salt-etched multilayered (ML) Ti3C2Tz. In this study, the chloride terminations of molten salt-etched ML-Ti3C2Tz were removed via thermal annealing at increased temperatures under an inert (argon) atmosphere. This thermal annealing created some bare sites available for further functionalization of Ti3C2Tz. XRD, EDS, and XPS measurements confirm the removal of much of the terminal groups of ML-Ti3C2Tz. Here, the annealed ML-Ti3C2Tz was refunctionalized by −OH groups and 3-aminopropyl triethoxysilane (APTES), which was confirmed by FTIR. The −OH and APTES surface-modified ML-Ti3C2Tz are evaluated as a solid lubricant, exhibiting ∼70.1 and 66.7% reduction in friction compared to a steel substrate, respectively. This enhanced performance is attributed to the improved interaction or adhesion of functionalized ML-Ti3C2Tz with the substrate material. This approach allows for the effective surface modification of MXenes and control of their functional properties. 

Solid–liquid composites (SLCs) combine the properties of solids and liquids, enhancing functionalities and expanding potential applications. Traditional methods for creating SLCs often face challenges such as low mass transfer efficiency, difficulty in controlling separation behavior, and substantial waste production. Herein, we report a new approach to solve these challenges by using disulfide-based responsive polymeric capsule shells to make liquid-filled monoliths for carbon capture. The capsules are prepared through interfacial polymerization and contain either non-polar poly(α-olefin)432 or highly polar 1-hexyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([HMIM][TFSI]) at 74–82 wt%. Upon gentle heating, the dynamic disulfide bonds of the isolated capsules undergo bond exchange, leading to the fusion of capsule shells into free-standing monoliths that retain >89 wt% of their liquid core and remain stable for at least two weeks. These monoliths demonstrate CO2 absorption rates and capacities comparable to their capsule counterparts; further, in response to radiofrequency (RF), they reach the CO2 desorption temperature in only ∼31 s. This innovative system addresses the limitations of conventional SLC fabrication techniques, offering a versatile and practical approach to fusing polymer capsule shells for applications across separation, energy storage, and carbon capture applications.