In–situ growth of carbon nanotubes on two–dimensional titanium carbide for enhanced electrochemical performance

Correction of Range-Variant Motion Error and Residual RCM in Sparse Regularization SAR Imaging

Lq (0 < q ≤ 1) regularization has been confirmed effective when applied to sparse SAR imaging. However, the inaccuracies caused by motion errors in the observation model will lead to various degradations and defocus in the reconstructed image. For high-resolution and light-small SAR systems, the range-variant motion errors will decrease the accuracy of range cell migration correction (RCMC), and residual range cell migration (RCM) will exceed multiple range resolution cells and degrade the image quality substantially. Aiming at this problem, in this paper, a novel azimuth-range decoupled sparse SAR imaging method with coarse-to-fine range-variant motion errors and residual RCM correction method is proposed. First, a one-step motion compensation (MOCO) operator is proposed using the inertial navigation systems (INS)/global positioning systems (GPS) information, which can significantly reduce the residual RCM and improve the reconstruction accuracy. Second, a fine high-order phase-error correction method is performed to correct the range and cross-range-varying phase errors using a joint imaging and phase-error estimation scheme, which will further improve the image focusing quality. Experimental results indicate the effectiveness of the proposed method.

Three-Dimensional MXenes for Supercapacitors: A Review

Supercapacitors have the characteristics of high power density and long cycle life, but the low energy density limits their further development. The 2D transitional metal carbides/nitrides (MXenes) show great application prospects in the field of supercapacitors due to their superior volumetric capacitance, metallic-like conductivity, tunable surface terminations, and structural advantages. However, like other 2D materials, MXenes suffer from the inevitable problem of nanosheet restacking and aggregation, which reduces the overall active surface sites and blocks the accessibility of the electrolyte ions. The transformation of 2D MXene nanosheets into 3D architectures is proven effective to overcome the restacking problem. The review briefly summarizes the preparation strategies of 3D MXene materials, including template-assisted method, framework-assisted method, chemical assembly method, foaming method, and other methods with the discussion centered on the performances of 3D MXenes in supercapacitors. Finally, an outlook on the current progress and opportunities is given to highlight the increasing popularity of 3D MXenes in supercapacitors.

MXene/Carbon Nanotube Hybrids: Synthesis, Structures, Properties, and Applications

Since the successful preparation of few-layer transition metal carbides from three-dimensional MAX phases in 2011, MXenes (known as a family of layered transition metal carbides, nitrides, and carbonitrides) have been intensively studied. Though MXenes have been adopted as active materials in many applications, issues including aggregation and restacking are likely to hamper their potential applications. In order to address these prevailing challenges, the concept of MXene/carbon nanotube (CNT) hybrids was proposed initially in 2015, where CNTs were incorporated as the spacers and conductive additives. Ever since, MXene/CNT hybrids with different architectures have been synthesized by a number of methods and applied in numerous fields. Herein, after the discussion about general synthesis approaches, architectures, and properties of the hybrids, this Review summarized the recent advances in the application of MXene/CNT hybrids in energy storage devices, sensors, electrocatalysis, electromagnetic interference shielding, and water treatment, in which the function of individual components was clarified. In the end, the current research trend in this field were discussed and several technical issues were highlighted along with some suggestions on future research directions.

Composite Fe3O4-MXene-Carbon Nanotube Electrodes for Supercapacitors Prepared Using the New Colloidal Method

MXenes, such as Ti3C2Tx, are promising materials for electrodes of supercapacitors (SCs). Colloidal techniques have potential for the fabrication of advanced Ti3C2Tx composites with high areal capacitance (CS). This paper reports the fabrication of Ti3C2TX-Fe3O4-multiwalled carbon nanotube (CNT) electrodes, which show CS of 5.52 F cm-2 in the negative potential range in 0.5 M Na2SO4 electrolyte. Good capacitive performance is achieved at a mass loading of 35 mg cm-2 due to the use of Celestine blue (CB) as a co-dispersant for individual materials. The mechanisms of CB adsorption on Ti3C2TX, Fe3O4, and CNTs and their electrostatic co-dispersion are discussed. The comparison of the capacitive behavior of Ti3C2TX-Fe3O4-CNT electrodes with Ti3C2TX-CNT and Fe3O4-CNT electrodes for the same active mass, electrode thickness and CNT content reveals a synergistic effect of the individual capacitive materials, which is observed due to the use of CB. The high CS of Ti3C2TX-Fe3O4-CNT composites makes them promising materials for application in negative electrodes of asymmetric SC devices.

Heterostructure Composites of CoS Nanoparticles Decorated on Ti3C2Tx Nanosheets and Their Enhanced Electromagnetic Wave Absorption Performance

As a typical two-dimensional material, MXene possesses excellent conductivity and tunable interlayer space, which makes it have an impressive development potential in the field of electromagnetic (EM) waves absorbing materials. In this work, we fabricated a sandwich structure CoS@Ti₃C₂T_x composite using a simple solvothermal process. The CoS nanoparticles are anchored on the Ti₃C₂T_x MXene sheets, forming a heterolayered structure. The results demonstrate that the CoS@Ti₃C₂T_x composites with the sandwich-like architecture showed excellent EM absorbing performance due to the synergistic effects of the conductivity loss, interface polarization, and dipole polarization. When the doping ratio was 40 wt %, the maximum reflection loss value of CoS@Ti₃C₂T_x was up to –59.2 dB at 14.6 GHz, and the corresponding effective absorption bandwidth (below –10 dB) reached 5.0 GHz when the thickness was only 2.0 mm. This work endows a new candidate for the design of MXene-based absorption materials with optimal performance.

Enhanced Antistatic and Self-Heatable Wearable Coating with Self-Tiered Structure Caused by Amphiphilic MXene in Waterborne Polymer

The antistatic and self-heatable flexible coating is highly desired for next-generation multifunctional clothing. MXene is a promising filler that possesses an excellent conductivity, an efficient photothermal conversion, and an outstanding compatibility with the waterborne polymer. In this study, MXene was integrated with waterborne polyacrylate by a solution-blending method. The polyacrylate/MXene composites display a self-tiered structure, and the composite coated leather possesses a surface resistivity of 7.85 × 10⁹ Ω with 2 wt % loading, satisfying the B-level of the antistatic standard. The polyacrylate/MXene-0.5 wt % shows a higher temperature increase of 46.9 °C than that of pure polyacrylate after being irradiated by a 275 W IR light for 5 min, and the surface temperature of polyacrylate/MXene-0.5 wt % composite coated leather is 5.4 °C higher than that of polyacrylate coated leather after being irradiated by sunlight for 30 min. The tensile strength of the polyacrylate/MXene-1 wt % composite is increased by 28.3% compared with that of pure polyacrylate. All of the results prove its promising application in the multifunctional coating. Moreover, amphiphilic MXene was produced by changing the etching degree, which resulted in a self-tiered structure of the polyacrylate/MXene composite owing to the improved interfacial activity of MXene. The amphiphilic MXene possesses a decreased surface tension and can serve as a stabilizer for a Pickering emulsion, which suggests novel routes for constructing a multifunctional polymer/MXene composite.

Recent progress and advances in the environmental applications of MXene related materials

MXenes are a new type of two-dimensional (2D) transition metal carbide or carbonitride material with a 2D structure similar to graphene. The general formula of MXenes is M_n+1X_nT_x, in which M is an early transition metal element, X represents carbon, nitrogen and boron, and T is a surface oxygen-containing or fluorine-containing group. These novel 2D materials possess a unique 2D layered structure, large specific surface area, good conductivity, stability, and mechanical properties. Benefitting from these properties, MXenes have received increasing attention and emerged as new substrate materials for exploration of various applications including, energy storage and conversion, photothermal treatment, drug delivery, environmental adsorption and catalytic degradation. The progress on various applications of MXene-based materials has been reviewed; while only a few of them covered environmental remediation, surface modification of MXenes has never been highlighted. In this review, we highlight recent advances and achievements in surface modification and environmental applications (such as environmental adsorption and catalytic degradation) of MXene-based materials. The current studies on the biocompatibility and toxicity of MXenes and related materials are summarized in the following sections. The challenges and future directions of the environmental applications of MXene-based materials are also discussed and highlighted.