Comparative Effects of Hydrazine and Thermal Reduction Methods on Electromagnetic Interference Shielding Characteristics in Foamed Titanium Carbonitride MXene Films.

The urgent need for the development of micro-thin shields against electromagnetic interference (EMI) has sparked interest in MXene materials owing to their metallic electrical conductivity and ease of film processing. Meanwhile, postprocessing treatments can potentially exert profound impacts on their shielding effectiveness (SE). This work comprehensively compares two reduction methods, hydrazine versus thermal, to fabricate foamed titanium carbonitride (Ti3CNTx) MXene films for efficient EMI shielding. Upon treatment of ≈ 100 µm-thick MXene films, gaseous transformations of oxygen-containing surface groups induce highly porous structures (up to ≈ 74.0% porosity). The controlled application of hydrazine and heat allows precise regulation of the reduction processes, enabling tailored control over the morphology, thickness, chemistry, and electrical properties of the MXene films. Accordingly, the EMI SE values are theoretically and experimentally determined. The treated MXene films exhibit significantly enhanced SE values compared to the pristine MXene film (≈ 52.2 dB), with ≈ 38% and ≈ 83% maximum improvements for the hydrazine and heat-treated samples, respectively. Particularly, heat treatment is more effective in terms of this enhancement such that an SE of 118.4 dB is achieved at 14.3 GHz, unprecedented for synthetic materials. Overall, the findings of this work hold significant practical implications for advancing high-performance, non-metallic EMI shielding materials.

Overcoming Ion Transport Barrier by Plasma Heterointerface Engineering: Epitaxial Titanium Carbonitride on Nitrogen-Doped TiO2 for High-Performance Sodium-Ion Batteries.

Anatase TiO2 is a promising anode material for lithium-ion batteries (LIBs) and sodium-ion batteries (SIBs) due to its high specific capacity, low cost, and excellent cycle stability. However, low electrical conductivity and poor Na+ ion transport in TiO2 limit its practical applications. Here, substantially boosted Na+ ion transport and charge transfer kinetics are demonstrated by constructing a near-ideal non-rectifying titanium carbonitride/nitrogen-doped TiO2 (TiCx N1- x /N-TiO2 ) heterostructure. Owing to the fast plasma effects and metastable hybrid phases, the TiCx N1- x is epitaxially grown on TiO2 . Energy band engineering at the interface induces high electron densities and a strong built-in electric field, which lowers the Na+ diffusion barrier by a factor of 1.7. As a result, the TiCx N1- x /N-TiO2 electrode exhibits excellent electrochemical performance. The reversible specific capacities at rates of 0.1 and 10 C reach 312.3 and 173.7 mAh g-1 , respectively. After 600 cycles of charge and discharge at 10 C, the capacity retention rate is 98.7%. This work discovers an effective non-equilibrium plasma-enabled process to construct heterointerfaces that can enhance Na+ ion transport and provides generic guidelines for the design of heterostructures for a broader range of energy storage, separation, and other devices that rely on controlled ionic transport.

MXsorption of mercury: Exceptional reductive behavior of titanium carbide/carbonitride MXenes.

Two-dimensional (2D) transition metal carbides and nitrides (MXenes) have drawn considerable attention for application in the field of environmental remediation. In this study, we report the simultaneous reductive-adsorption behavior of Ti3CNTx for toxic metal ion Hg2+ ion in the aqueous phase. 2D Ti3CNTx and Ti3C2Tx MXene nanosheets were synthesized by exfoliation of Ti3AlCN and Ti3AlC2 MAX phases, respectively. Various characteristics analysis confirmed the successful fabrication of MAX phases and their exfoliation into MXenes. The fabricated MXene nanosheets were used to investigate their Hg2+ removal, Hg2+ intercalation, and surface interaction mechanism efficiencies. Both MXenes were found to adsorb and reduce a large amount of Hg2+. Analytical techniques such as X-ray powder diffraction, field emission transmission electron microscopy, zeta-potential analyses, and X-ray photoelectron spectroscopy were used to investigate the material characteristics and structural changes after uptake of Hg2+. The quantitative investigation confirmed the interaction of bimetal and hydroxyl groups with Hg2+ using electrostatic interactions and adsorption-coupled reduction. In addition, both MXenes exhibited extraordinary Hg ion removal capabilities in terms of fast kinetics with an excellent distribution coefficient (KdHg) up to 1.36 × 10+9. Based on batch adsorption results, Ti3C2Tx and Ti3CNTx exhibited removal capacities of 5473.13 and 4606.04 mg/g, respectively, for Hg2+, which are higher than those of previous Hg adsorbents.

Strong Interaction between Titanium Carbonitride Embedded in Mesoporous Carbon Nanofibers and Pt Enables Durable Oxygen Reduction.

Platinum (Pt) supported on high surface area carbon has been the most widely used electrocatalyst in proton exchange membrane fuel cell (PEMFC). However, conventional carbon supports are susceptible to corrosion at high potentials, leading to severe degradation of electrochemical performance. In this work, titanium carbonitride embedded in mesoporous carbon nanofibers (m-TiCN NFs) are reported as a promising alternative to address this issue. Benefiting from the interpenetrating conductive pathways inside the one-dimensional (1D) nanostructures and the embedded TiCN nanoparticles (NPs), m-TiCN NFs exhibit excellent stability at high potentials and interact strongly with Pt NPs. Subsequently, m-TiCN NFs-supported Pt NPs deliver remarkably enhanced oxygen reduction reaction (ORR) activity and durability, with negligible activity decay and less than 5% loss of electrochemical surface area（ECSA） after 50 000 cycles. Moreover, the fuel cell assembled by this catalyst delivers a maximum power density of 1.22 W cm-2 and merely 3% loss after 30 000 cycles of accelerated durability tests under U.S. Department of Energy (DOE) protocols. The improved ORR activity and durability are attributed to the superior corrosion resistance of the m-TiCN NF support and the strong interaction between Pt and m-TiCN NFs.

Hybrid Core-Shell TiCN@SiO2 Nanoparticles in Percolation-Based Polyvinylidene Fluoride Dielectrics for Improved High-Voltage Capacitive Energy Storage.

Solid-state polymer dielectrics offer an exceptional dielectric breakdown, but require an enhanced energy density to be competitive with alternative electrolyte-based energy storage technologies. Therefore, this research introduces conductive titanium carbonitride (TiCN) nanoparticles in a polyvinylidene fluoride (PVDF) matrix to obtain flexible percolation-based nanodielectrics by ultrasonication-based suspension processing and hot pressing. Well-dispersed TiCN nanoparticles in PVDF were obtained for a wide range of filler volume fractions, and an exceptional peak in the dielectric constant equal to 1130 (0.1 Hz) and 29 (10 kHz) was observed near the percolation threshold (9.2 vol %). The enhanced dielectric constant was ascribed to massive interfacial polarization occurring, resulting from Maxwell-Wagner-Sillars (MWS) polarization and a nanocapacitor mechanism that are dominant at low and high frequencies, respectively. An improvement by 30% in the energy density (0.042 Wh kg-1) compared with the neat PVDF matrix was achieved for the PVDF/TiCN nanodielectrics. The first successful uniform deposition of a nanometer-thin (3 nm) silica (SiO2) shell via the Stöber process on TiCN nanoparticles significantly suppressed the dielectric losses near percolation for the PVDF/TiCN@SiO2 nanodielectrics by more than 1 order of magnitude while offering dielectric constants of 34 (0.1 Hz) and 10 (10 kHz). This study demonstrates the potential of hybrid (core-shell) percolation-based dielectrics for an improved capacitive dielectric performance by an integrated dielectric characterization approach that simultaneously optimizes the dielectric constant, loss tangent, breakdown strength, and energy density.

Enhancement of bioactivity of titanium carbonitride nanocomposite thin films on steels with biosynthesized hydroxyapatite.

Thin films of titanium carbonitride (TiCN) were fabricated by DC magnetron sputtering on medical grade steel. The biocompatibility of the coating was further enhanced by growing hydroxyapatite crystals over the TiCN-coated substrates using biologically activated ammonia from synthetic urine. The coatings were characterized using X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy (SEM)-energy dispersive spectroscopy, and Raman spectroscopy. The electrochemical behavior of the coatings was determined in simulated body fluid. In addition, hemocompatibility was assessed by monitoring the attachment of platelets on the coating using SEM. The wettability of the coatings was measured in order to correlate with biocompatibility results. Formation of a coating with granular morphology and the preferred orientation was confirmed by SEM and X-ray diffraction results. The hydroxyapatite coating led to a decrease in thrombogenicity, resulting in controlled blood clot formation, hence demonstrating the hemocompatibility of the coating.