Metallic Electrical Conductivity Research Articles

Electrochemical performance of MXene/Fe3O4 composite derived from recycled carbon for vanadium redox flow battery

MXenes are emerging 2D materials that have demonstrated excellent combined metallic electrical conductivity and hydrophilicity. They have been extensively studied in applications like energy storage, catalysis, optoelectronics, and so on. In this work, the carbon sourced from carbon soot extracted from fossil fuel combustion wastes was used to produce Ti3C2Tx MXene for the first time. The recyclable carbon-derived MXene/iron oxide (Fe3O4) composites with different concentrations of Fe3O4 were synthesized via a hydrothermal route. The successful synthesis of the MXene/Fe3O4 composites was confirmed by the SEM, HRTEM, EDX, UV–Vis, XRD, FTIR, and XPS analyses. Electron images morphologically revealed the existence of Fe3O4 within the as-synthesized composites, while UV–Vis spectra detected the surface plasmon resonance peaks of MXene and Fe3O4, respectively. The XRD spectra identified the crystalline structure of MXene at 5.7° (002) and 25.3° (006), as well as the magnetite Fe3O4 at 18.2° (111) and 38.2° (311), which aligned well with the presence of Ti-O and Fe-O bands observed in the FTIR data. The XPS study also confirmed the presence of the Fe element within the composites. The electrochemical performance of composite as electrode material towards the cathode VO2+/VO2+ redox reaction was investigated. The synergistic effect of both MXene and metal oxide improved the electrode kinetic activity towards the redox reaction, as evidenced by the voltage peak separation (ΔE) and the ratio of peak currents (IO/IR) values determined in cyclic voltammetry (CV), and the charge transfer process probed by electrochemical impedance spectroscopy (EIS). The specific capacity of the battery with the composites was increased along with the improvement of retention strength. The MXene/Fe3O4 5 wt% composite displayed the highest electrochemical catalytic activity with the lowest ΔE (124 mV), IO/IR of about 1, producing specific capacities of 10.2 Ah L-1 and energy efficiency of 70.1 %. The nature of MXene and Fe3O4, morphological features, and higher surface area of composites increased the kinetic activity of the electrode, enabling the composites to be potentially applied in the vanadium redox flow battery (VRFB) system.

Colossal conductivity anisotropy in 3D metallic carbon films

Harnessing the phenomena of quantum coherence and destructive interference, we have successfully engineered and synthesized a three-dimensional (3D) graphene-based film exhibiting remarkable properties, including metallic thermal conductivity (κ ≈ 150 Wm⁻1K⁻1) and electrical conductivity (σ ≈ 320 kSm⁻1) at room temperature. Notably, these films demonstrate colossal transport anisotropies, reaching approximately 103 for thermal and 105 for electrical conductivity. This places them among the conducting materials with the highest anisotropies known to date, surpassing even the performance of one-dimensional (1D) carbon nanotubes and two-dimensional (2D) materials like h-BN and MoS₂. These films are synthesized by self-assembly and cross-linking of edge-hydrolyzed graphene flakes. The electron transport between flakes is phonon mediated and at low temperatures the films present quantum critical behavior of a metal to Anderson insulator transition. We measure the electron transport properties in a Hall bar geometry and extract the critical exponents as a function of the sample mobility.

VOx anchored Ti3C2Tx MXene heterostructures for high-performance 2.2 V supercapacitors

Pseudocapacitive materials with superior electrochemical properties have attracted significant interest in developing high-performance supercapacitors. Herein, VOx anchored Ti3C2Tx MXene pseudocapacitive materials are synthesized via a solvothermal method to synergize metallic electrical conductivity and redox activity. Pure vanadium oxide synthesis results in VO2 formation, while in the presence of Ti3C2Tx, quasi-metallic V2O3 and VO2 (VOx) are observed due to the decomposition of surface functionalities of Ti3C2Tx. The growth of the V2O3 phase increases with an increase in the weight concentration of Ti3C2Tx. The optimal composition of heterostructure delivers a specific capacitance of 364 F g−1 in a stable potential window of −0.9 V–1 V, surpassing the specific capacitance of pure VO2 (245 F g−1) and Ti3C2Tx (140 F g−1) in 0.5 M K2SO4 electrolyte. Furthermore, the developed symmetric supercapacitor (SSC) delivers an energy density of 45.7 Wh kg−1 at a power density of 1.1 kW kg−1 with cyclic stability of 78 % for 10000 cycles with a self-discharge open circuit potential of 1.34 V. This work highlights a strategy to develop anodic and cathodic active pseudocapacitive material based SSC to improve energy density and mitigate self-discharge.

Eddy current nondestructive evaluation of metallic plates electrical conductivity using artificial neural networks based inverse problem

The most used method and extensively studied in the literature for conductors’ characterization is Eddy Current Nondestructive Evaluation (ECNDE) due to its significant advantages, such as its ability to preserve the integrity of the structures or materials to be examined during manufacturing or a regular in-service nondestructive testing. Various approaches are developed for the Eddy Current measurement of the electrical conductivity. In the present work, the evaluation of the electrical conductivity is treated as an inverse problem. In pursuit of this aim, a combination is established between Eddy currents evaluation and artificial neural networks (ANN) to evaluate the electrical conductivity of homogeneous metallic plates from eddy-current probe impedance measurements. For this purpose, an experimental setup is developed, including a bobbin-coil probe, metallic plates (target), data acquisition and signal processing systems. Finally, experimental conductivity values of various metallic plates using ANN are compared with those obtained using four-point measurements of direct current potential drop (DCPD) made on the same plates and very good agreement is obtained.

Kinetically controlled metal-elastomer nanophases for environmentally resilient stretchable electronics

Nanophase mixtures, leveraging the complementary strengths of each component, are vital for composites to overcome limitations posed by single elemental materials. Among these, metal-elastomer nanophases are particularly important, holding various practical applications for stretchable electronics. However, the methodology and understanding of nanophase mixing metals and elastomers are limited due to difficulties in blending caused by thermodynamic incompatibility. Here, we present a controlled method using kinetics to mix metal atoms with elastomeric chains on the nanoscale. We find that the chain migration flux and metal deposition rate are key factors, allowing the formation of reticular nanophases when kinetically in-phase. Moreover, we observe spontaneous structural evolution, resulting in gyrified structures akin to the human brain. The hybridized gyrified reticular nanophases exhibit strain-invariant metallic electrical conductivity up to 156% areal strain, unparalleled durability in organic solvents and aqueous environments with pH 2–13, and high mechanical robustness, a prerequisite for environmentally resilient devices.

Liquid metal based conductive textile via reactive wetting for stretchable electromagnetic shielding and electro-thermal conversion applications

Developing stretchable electromagnetic interference (EMI) shielding fabrics has long been fascinating, but remains challenging. Inspired by the fluidity of GaInSn based liquid metal (LM), a series of conductive and stretchable textiles was successfully fabricated here. Notably, the collaboration between Ag nanoparticles and flexible LM coating give rise to metallic electrical conductivity (5637 S/m) and distinguished EMI shielding effectiveness (112.8 dB), together with a remarkable shielding value (96.2 dB) even under stretching. Such a well-established conductive pathway can further yield favorable Joule heating performance that enables low-voltage driving warmth retention. Moreover, the LM coating deliver anti-fouling property and robust fastness on the textile substrate, with no discernible reduction in EMI SE observed even after repetitive strain or cyclic washing. These fascinating features, together with the easy processability, are believed to further drive the structure design of novel conductive textile toward wearable applications.

L‐Cysteine‐Encapsulated MXene Nanosheet Possessing Ultra‐Antioxidation in Aqueous Suspension for Electrophoretic Deposition Assisted Carbon‐Fiber‐Surface Modification

AbstractWith recent progress in 2D materials, Ti3C2Tx MXene featured high metallic electrical conductivity, high electromagnetic interference shielding effectiveness, and super in‐plane stiffness, exhibits unique advantages in many fields, but is rarely applied as a sizing agent in long‐time continuous processing of carbon fiber sizing because of its poor ambient stability in aqueous suspension. Herein, a new strategy to chemically encapsulate the reactive sites of MXene nanosheet with l‐cysteine for restricting the attacking of water and/or oxygen in aqueous suspension is proposed. Based on the ultra‐antioxidation, polarity, and electrical properties of l‐cysteine‐encapsulated Ti3C2Tx MXene (LC‐MX) nanosheet, the LC‐MX, even if aging for weeks in aqueous suspension, can be deposited on the surface of high‐modulus carbon fiber (HMCF) uniformly via the electrophoretic deposition assisted sizing. Benefiting from the enhanced surface energy, wettability, and roughness of LC‐MX‐sized HMCF (HMCF‐LCMX) relative to that of unsized one (U‐HMCF), the interfacial property of HMCF‐LCMX/epoxy (EP) composites is also improved, for which the interlayer shear strength (ILSS) of the composite reached 88.5 MPa, 52.8% higher than that of U‐HMCF/EP composite (57.9 MPa). This work makes an essential step toward the application of ultra‐stable MXene nanosheet suspension in large‐scale continuous carbon fiber sizing.

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 ≈ 100µm-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 (≈ 52.2dB), 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 118.4dB is achieved at 14.3GHz, unprecedented for synthetic materials. Overall, the findings of this work hold significant practical implications for advancing high-performance, non-metallic EMI shielding materials.

Super-flexible and highly conductive H-Ti3C2Tx MXene composite films with 3D macro-assemblies for electromagnetic interference shielding

2D MXene are showing great prospects for EMI shielding by virtue of abundant surface functional groups and outstanding metallic electrical conductivity. However, it remains a great challenge to simultaneously achieve flexible, lightweight and high stability in MXene shielding materials due to inferior mechanical strength and poor oxidation stability. Gelation paves up an effective and facile strategy to develop highly stable and conductive 3D porous Ti3C2Tx architectures. Herein, super-flexible and highly conductive H-Ti3C2Tx MXene composite films with 3D macro-assemblies for EMI shielding were fabricated through a gelation-densification process initiated by hydrochloric acids, and two-step vacuum-assisted filtration followed by freeze-casting approach. The obtained nanocomposite films manifest satisfactory mechanical properties with a tensile strength of 116.51 MPa, excellent EMI SE of 55.14 dB, superior SSE/t and high EMI SE retention after 5000 cycles of bending deformation. In addition, the as-prepared nanocomposite papers demonstrate outstanding thermal management performances such as rapid response time, high Joule heating temperature (118 °C) at low applied voltage (2.5 V) and eminent working stability (4000 s).

Controllable Flow and Manipulation of Liquid Metals

AbstractThis review summarizes the controllable flow and manipulation of gallium‐based liquid metals (e.g., eutectic gallium indium, EGaIn). There are generally only a few ways to handle fluids, but liquid metals offer versatile control due to their properties: 1) excellent fluidity, 2) adjustable surface tension, 3) electrically and chemically controllable surface oxides, 4) metallic electrical and thermal conductivity, and 5) the ability to alloy with other metals (e.g., magnetic particles). These all‐in‐one properties empower liquid metals to exhibit controllable flow in confined microchannels (steerable flow) and from nozzles (printable flow), and make liquid metals susceptible to various energy fields, including electric, magnetic, electromagnetic, wave, and light fields. Consequently, the flow and manipulation of liquid metals enable intriguing morphological changes (e.g., formation of droplets/plugs, jets, fibers) and controllable motion (e.g., jumping, bouncing, directional locomotion, rotation) of liquid metals with new fluidic phenomena and practical applications such as soft electronics and robotics. This review aims to present a selective framework and provide an insightful understanding for controlling and shaping liquid metals, thereby stimulating further research and generating increased interest in this topic.

Titanium Carbide (Ti3C2Tx) MXene as Efficient Electron/Hole Transport Material for Perovskite Solar Cells and Electrode Material for Electrochemical Biosensors/Non-Biosensors Applications.

Recently, two-dimensional (2D) MXenes materials have received enormous attention because of their excellent physiochemical properties such as high carrier mobility, metallic electrical conductivity, mechanical properties, transparency, and tunable work function. MXenes play a significant role as additives, charge transfer layers, and conductive electrodes for optoelectronic applications. Particularly, titanium carbide (Ti3C2Tx) MXene demonstrates excellent optoelectronic features, tunable work function, good electron affinity, and high conductivity. The Ti3C2Tx has been widely used as electron transport (ETL) or hole transport layers (HTL) in the development of perovskite solar cells (PSCs). Additionally, Ti3C2Tx has excellent electrochemical properties and has been widely explored as sensing material for the development of electrochemical biosensors. In this review article, we have summarized the recent advances in the development of the PSCs using Ti3C2Tx MXene as ETL and HTL. We have also compiled the recent progress in the fabrication of biosensors using Ti3C2Tx-based electrode materials. We believed that the present mini review article would be useful to provide a deep understanding, and comprehensive insight into the research status.

Lattice modification of ZrO2-δ and formation of rocksalt structure ZrO and Zr(O,N) after DC electrical loading of 3YSZ

It is widely acknowledged that electrochemical reduction occurs during DC flash sintering (FS) of YSZ. In situ experiments have shown the emergence of new phases during FS that disappear again when the current is switched off. In addition, it has recently been reported that YSZ flash sintered in the absence of oxygen has a high electrical conductivity at room temperature. In this investigation electrical loading of YSZ was conducted in Ar and N2 and maintained as the furnace cooled down such that on removing the current, the sample was rapidly quenched, avoiding reoxidation or other diffusion-limited phase transformations. XRD showed that the tetragonality of the ZrO2-δ phase was diminished and the volume of the unit cell increased, the effect of the electrochemical reduction being similar to an increase in Y2O3 content. In addition, rocksalt structure Zr(O,N) with a lattice constant of 0.4580 nm was formed at the surface and retained at room temperature. This phase had a metallic lustre and electrical conductivity approaching those of metals. The results enable several recent results in the literature to be reconciled and the implications for flash sintering are briefly discussed.

Research Advances on 2D Mxenes for Photovoltaic Applications

MXene, a two-dimensional nanomaterial, has an impressive range of properties that make it a perfect choice for a variety of applications, including energy systems, high-tech sensors, optics, medical devices, and electromagnetic interference shielding. Its high carrier mobility, metallic electrical conductivity, superior transparency, excellent mechanical characteristics, and tunable work function have drawn much attention. This review examines the utilization of MXene in solar technology, highlighting its potential as an electrode, charge carrier, and additive in quantum dot-sensitized, perovskite, silicon wafer-based, and organic solar cells. Additionally, a summary table is provided that briefly outlines the different methods of synthesizing MXene and their respective etching chemicals and precursors. This review’s latter part looks at the challenges associated with MXene and offers potential solutions and prospects.

Continuous Metal-Insulator Transition and Scale Laws in Metallic n-Type InP

We have studied the transport properties in metallic n-type InP semiconductor. We show that the dependence on temperature of metallic electrical conductivity obey to the law 𝜎 = 𝜎(𝑇 = 0) + 𝑚𝑇1/2. We highlight the absence of a minimum electrical conductivity 𝜎𝑚𝑖𝑛 proposed by Mott at the metal-insulator transition. We show that the conductivity at temperature T = 0 K, 𝜎(𝑇 = 0) , follows a scaling law as a function of the effective parallel and perpendicular Bohr radii 𝑎∥ and 𝑎⊥.

2D/2D BiOIO3/Ti3C2 MXene nanocomposite with efficient charge separation for degradation of multiple pollutants

Co-catalysts can achieve efficient separation of photogenerated carriers and are considered as a promising strategy for solar photocatalytic removal of pollutants. Herein, we reported the synthesis of nanocomposite of BiOIO3/Ti3C2 MXene combining two dimensional 2D BiOIO3 with 2D Ti3C2 MXene co-catalyst. The few-layered 2D Ti3C2 MXene provided more adsorption and reaction sites. Furthermore, the synergism of intimate interfacial contact between the two 2D nanosheets and robust metallic electrical conductivity of Ti3C2 MXene significantly accelerated the separation and migration of photogenerated charge carriers. A variety of organic pollutants were proved to be effectively degraded by 2D/2D BiOIO3/Ti3C2 MXene composites. The degradation efficiencies followed the order tetracycline hydrochloride (93.4 %) > diclofenac sodium (87.6 %) > levofloxacin hydrochloride (77.4 %) > 4-nitrophenol (43.3%). Besides, the satisfactory recycling and stability of BiOIO3/Ti3C2 MXene for the degradation of organic pollutants in water under solar irradiation predicted its good prospect for practical applications.

2D MXene/ 1D GaN van der Waals heterojunction for self-powered UV photodetector

MXene's two-dimensional (2D) morphology, metallic electrical conductivity, and optical transparency characteristics have been widely utilized to uplift the performance of diverse optoelectronic devices. In this study, we demonstrate a simple spin-coating of 2D MXene nanosheets on 1D GaN nanorods (NRs) to establish a van der Waals (vdW) Schottky junction, which is efficient to detect UV radiation (λ = 382 nm) without requiring the external power supply. The built-in electric field developed through vdW Schottky junction formation stimulates the separation of electron–hole pairs and thereby facilitates the MXene/GaN NRs device to exhibit better UV detection performance than the pristine GaN NRs device. The performance of both pristine GaN and MXene/GaN NRs devices is compared by tuning the UV radiation power density in the range of 0.33–1.35 mW/cm2. Notably, the self-powered MXene/GaN NRs photodetector demonstrated the characteristics of high photoresponsivity (48.6 mA/W), detectivity (5.9 × 1012 Jones), and external quantum efficiency (543%). These characteristics signify the suitability of MXene/GaN self-powered photodetectors for various applications, including imaging, sensing networks, and energy-saving communication.

Graphene Oxide‐Assisted Multiple Cross‐Linking of MXene for Large‐Area, High‐Strength, Oxidation‐Resistant, and Multifunctional Films

AbstractTransition metal carbides/nitrides (MXenes) with metallic electrical conductivity and excellent processability attract increasing attention for assembling multifunctional macrostructures. However, the challenges, involving poor mechanical strength, inferior oxidation stability, and limited scalable manufacturing, impede their wide applications. Herein, the large‐area, high‐strength, ultra‐flexible hybrid films are developed through the multiple physical and chemical cross‐linking of MXene/cellulose films facilitated by graphene oxide. The MXene‐based films manifest significantly improved hydrophobicity, water/solvent resistance, and oxidation stability, and meanwhile, maintain excellent conductivity and electromagnetic interference shielding performance. The X‐band surface‐specific shielding effectiveness (SE) of 18,837.5 dB cm2 g−1 and an SE over 60 dB in an ultra‐broadband frequency range are achieved, comparable to the best shields ever reported. Furthermore, the wearable films demonstrate excellent photothermal antibacterial and electrothermal deicing applications. Thus, such high‐performance MXene‐based films developed through a facile and scalable manufacturing method have substantial application prospects in flexible electronics, thermotherapy, electromagnetic compatibility, and aerospace.

Interfused core-shell heterogeneous graphene/MXene fiber aerogel for high-performance and durable electromagnetic interference shielding.

Flexible, lightweight, and durable electromagnetic interference (EMI) shielding materials are urgently required to solve the increasingly serious electromagnetic radiation pollution. Transition metal carbides/nitrides (MXenes) are promising candidates for EMI shielding materials because of their excellent metallic electrical conductivity. However, MXenes are highly susceptible to oxidization when exposed to wet environments, leading to the loss of their functional properties and degradation of reliability and stability. Herein, an interfused core-shell heterogeneous reduced graphene oxide (rGO)/MXene aerogel (GMA) is designed for the first time via coaxial wet spinning and freeze-drying. The fabricated GMAs exhibit excellent EMI shielding performance, and the EMI shielding effectiveness (SE) and specific EMI SE can be up to 83.3dB and 3119dB·cm3/g, respectively, which is higher than most carbon-based and MXene-based aerogels and foams. More importantly, GMAs have only a 17.4% degradation in EMI shielding performance after 120days due to the protection of hydrophobic graphene sheath, exhibiting superior EMI shielding durability to its MXene film counterpart. Moreover, the hydrophobic GMAs exhibit good oil/water separation and thermal insulation performance. The interfused core-shell GMAs are highly promising for applications in durable EMI shielding, thermal insulation, oil/water separation and sensors, etc.

Superhydrophobic hollow magnetized Fe3O4 nanospheres/MXene fabrics for electromagnetic interference shielding

The development of high-performance electromagnetic interference (EMI) shielding materials is urgently needed to mitigate electromagnetic radiation pollution. Two-dimensional transition metal carbides (MXenes) are promising EMI shielding materials because of their high metallic electrical conductivity. However, tuning the EMI shielding performance of MXene composites remains challenging via the structure engineering strategy. Herein, we develop a layer-by-layer assembling strategy to construct multilayer sandwiched hollow magnetic Fe3O4 nanospheres (HFO)/MXene on flexible nonwoven fabrics. The fabricated Fe3O4/MXene composite fabrics (HFMs) exhibit low sheet resistance (4.6 Ω/□), super-hydrophobicity, self-cleaning, and good EMI shielding performance (EMI shielding effectiveness of 33.28 dB). More importantly, the EMI shielding mechanism of HFMs is tunable according to the loaded active materials. Thus, the mechanism can alternate from absorption to reflection. Moreover, the HFMs exhibit good electrothermal performance and can be used as a wearable heater for personal thermal management. This work provides a new approach for the structural design of high EMI shielding materials, and paves the way for the development of wearable electronics.

Electrocatalysis in Li–O2 battery over single-atom catalyst based on g-C3N4 substrate

The development of Li–O2 battery is severely hindered by the sluggish reaction kinetics of the oxygen electrode. Herein, we perform a first-principles study of single transition metal atom supported on g-C3N4 substrate (TM/g-C3N4) as potential single-atom catalyst (SAC) in Li–O2 batteries. Combined electronic analysis and thermodynamic calculations, the electrocatalytic mechanism of TM/g-C3N4 SACs in Li–O2 batteries is elucidated. Due to strong metal-substrate interactions, the TM atom is durably anchored at the unsaturated pyridine N site in the holey g-C3N4 substrate, thereby enabling long cycling stability of the oxygen electrode. Among the fifteen candidates studied, Ru/g-C3N4 SAC exhibits the lowest discharge and charge overpotentials. This behavior can be attributed to the synergistic effect of the moveable d electrons of Ru and electron-rich N coordinators, which results in significant interfacial charges, metallic electrical conductivity, and large spin magnetic moments of the RuN2 active center. This study provides in-depth atomic and electronic insights into the catalytic mechanism of TM/g-C3N4 SACs in Li-O2 batteries.