A high-performance electromagnetic wave absorbing composite based on graphene and polysiloxane-derived SiOC ceramic is realized via the polymer pyrolysis process. Hierarchical architecture consisting ...of two-dimensional graphene and one-dimensional SiC nanowire in ceramic matrix is achieved owing to the heterogeneous nucleation of SiC nanowires promoted by graphene at lower temperature. The dielectric and microwave absorption properties of the composites were studied at 293–673K. When graphene oxide loading is 3wt%, the composite attains a minimum reflection loss value of −69.3dB at 10.55GHz with a thickness of 2.35mm. With the increase of temperature, the composite exhibits better absorbing performance that the effective absorption bandwidth reaches 3.9GHz at 673K. The hierarchical networks with graphene/SiC nanowires achieved in SiOC matrix provide a feasible process for the realization of efficient electromagnetic wave absorption in ceramic-based composites at high temperature.
Free‐standing films that display high strength and high electrical conductivity are critical for flexible electronics, such as electromagnetic interference (EMI) shielding coatings and current ...collectors for batteries and supercapacitors. 2D Ti3C2Tx flakes are ideal candidates for making conductive films due to their high strength and metallic conductivity. It is, however, challenging to transfer those outstanding properties of single MXene flakes to macroscale films as a result of the small flake size and relatively poor flake alignment that occurs during solution‐based processing. Here, a scalable method is shown for the fabrication of strong and highly conducting pure MXene films containing highly aligned large MXene flakes. These films demonstrate record tensile strength up to ≈570 MPa for a 940 nm thick film and electrical conductivity of ≈15 100 S cm−1 for a 214 nm thick film, which are both the highest values compared to previously reported pure Ti3C2Tx films. These films also exhibit outstanding EMI shielding performance (≈50 dB for a 940 nm thick film) that exceeds other synthetic materials with comparable thickness. MXene films with aligned flakes provide an effective route for producing large‐area, high‐strength, and high‐electrical‐conductivity MXene‐based films for future electronic applications.
Strong and highly conductive binder‐free Ti3C2Tx MXene films with excellent electromagnetic interference shielding performance are fabricated by a blade‐coating method using high‐aspect‐ratio MXene flakes. Achieving such a combination of properties using a scalable fabrication process enables manufacturing of MXene‐based high‐performance devices and new applications.
Lightweight materials with high electrical conductivity and robust mechanical properties are highly desirable for electromagnetic interference (EMI) shielding in modern portable and highly integrated ...electronics. Herein, a three-dimensional (3D) porous Ti3C2T x /carbon nanotube (CNT) hybrid aerogel was fabricated via a bidirectional freezing method for lightweight EMI shielding application. The synergism of the lamellar and porous structure of the MXene/CNT hybrid aerogels contributed extensively to their excellent electrical conductivity (9.43 S cm–1) and superior electromagnetic shielding effectiveness (EMI SE) value of 103.9 dB at 3 mm thickness at the X-band frequency, the latter of which is the best value reported for synthetic porous nanomaterials. The CNT reinforcement in the MXene/CNT hybrid aerogels enhanced the mechanical robustness and increased the compressional modulus by 9661% relative to that of the pristine MXene aerogel. The hybrid aerogel with high electrical conductivity, good mechanical strength, and superior EMI shielding performance is a promising material for inhibiting EMI pollution.
Lightweight materials with high electrical conductivity and robust mechanical properties are highly desirable for electromagnetic interference (EMI) shielding in modern portable and highly integrated ...electronics. Herein, a three-dimensional (3D) porous Ti3C2Tx/carbon nanotube (CNT) hybrid aerogel was fabricated via a bidirectional freezing method for lightweight EMI shielding application. The synergism of the lamellar and porous structure of the MXene/CNT hybrid aerogels contributed extensively to their excellent electrical conductivity (943 S m-1) and superior electromagnetic shielding effectiveness (EMI SE) value of 103.9 dB at 3 mm thickness at the X-band frequency, the latter of which is the best value reported for synthetic porous nanomaterials. The CNT reinforcement in the MXene/CNT hybrid aerogels enhanced the mechanical robustness and increased the compressional modulus by 9661% relative to that of the pristine MXene aerogel. The hybrid aerogel with high electrical conductivity, good mechanical strength, and superior EMI shielding performance is a promising material for inhibiting EMI pollution.
As an increasing number of wireless devices are introduced to our daily lives, long-term environmentally stable conductive fabrics that can shield against electromagnetic radiation are increasingly ...desired. Herein, conventional cotton and linen fabrics were dip-coated in additive-free, aqueous Ti3C2Tx MXene dyes, which consist of only two-dimensional Ti3C2Tx flakes dispersed in water, to fabricate highly conductive fabrics for electromagnetic interference (EMI) shielding. Ti3C2Tx loading and electrical conductivity of the fabrics increased with the number of dip-coating cycles. After only 4 dip-coating cycles, EMI shielding effectiveness (SE) of Ti3C2Tx-coated (<15 wt%) cotton and linen fabrics reached ∼40 dB over the X-band range. After 24 dip-coating cycles, the total EMI SE increased to ∼80 dB for Ti3C2Tx-coated cotton (54 wt%) and linen (48 wt%) fabrics, which is higher than commercial metal-based conductive fabrics tested in this study. The average EMI SE performance of Ti3C2Tx-coated cotton and linen fabrics only decreased by ∼8% and ∼13%, respectively, after storage under ambient conditions for two years. This work suggests an attractive alternative to current metal-based conductive dyes and provides valuable insights into the development of environmentally stable wearable EMI shielding materials.
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MXenes are promising pseudocapacitive materials with ultrahigh specific capacitance. Currently, more than 30 stoichiometric MXene compositions and about 20 solid solutions have been experimentally ...synthesized. However, most studies focus on Ti3C2Tx or a few other single-M MXenes, and little is known about the electrochemical properties of solid-solution MXenes. Herein, two sets of niobium-based solid-solution MXenes (Ti2−yNbyTx and V2−yNbyTx; 0 ≤ y ≤ 2) were synthesized and the dependence of their electrochemical properties on the ratio of M elements in the structure was investigated. Relationships between the chemistry and charge storage ability, including capacitive properties and cycling stability in aqueous protic electrolyte, were determined. There is an inverse relationship between the prominence of the redox peaks and cycling stability; the latter increases with the niobium content. For instance, the capacitance retention after 20,000 cycles is less than 1% for Ti2CTx, but 78% for Ti0.4Nb1.6CTx. This study shows that electrochemical properties of MXenes can be controlled by tuning the ratio of transition metals in the MXene structure.
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•Double-metal solid-solution MXenes (Ti2−yNbyTx and V2−yNbyTx; 0 < y < 2) were synthesized and investigated.•The capacitive properties and cycling stability of solid-solution MXenes directly depend on their composition.•The redox peak intensity decreases while the cycling stability increases with the Nb content.•This study provides a guide for adjusting the electrochemical properties of MXenes by tuning the M-site chemistry.
Three-dimensional (3D) macroscopic covalently bonded carbon nanowires/graphene (CNWs/G) architectures can achieve the extraordinary properties based on theoretical work. A series of 3D structures ...have been recently fabricated. However, these architectures are far from theoretical model because CNWs are difficult to perfectly connect with the graphene substrate which has extremely low surface energy and complex internal structure. Here, we highlight a bioinspired approach based on polydopamine interface buffer for the fabrication of 3D macroscopic CNWs/G sponge composite. CNWs uniformly grow on graphene substrate through covalent CC bonding. The defects of CNWs and junction interface between CNWs with graphene greatly influence the electronic transport, leading to the strong polarization and electromagnetic wave attenuation under alternating electromagnetic field. Owing to this unique 3D architecture, the CNWs/G composite attains ultralight density and outstanding electromagnetic attenuation capability. CNWs/G/poly(dimethyl siloxane) composite exhibits the electromagnetic interference shielding effectiveness of 36 dB in X-band (8.2–12.4 GHz) and the composite density is 97.1 mg/cm3. The macroscopic 3D CNWs/G architecture overcomes the drawbacks of presently available 3D graphene products and opens up a wide horizon for structural, electronic, thermal transport, intramolecular junction, heterogeneous catalysis, electrochemical energy storage, and etc.
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Dynamic control of electromagnetic wave jamming is a notable technological challenge for protecting electronic devices working at gigahertz frequencies. Foam materials can adjust the reflection and ...absorption of microwaves, enabling a tunable electromagnetic interference shielding capability, but their thickness of several millimetres hinders their application in integrated electronics. Here we show a method for modulating the reflection and absorption of incident electromagnetic waves using various submicrometre-thick MXene thin films. The reversible tunability of electromagnetic interference shielding effectiveness is realized by electrochemically driven ion intercalation and de-intercalation; this results in charge transfer efficiency with different electrolytes, accompanied by expansion and shrinkage of the MXene layer spacing. We finally demonstrate an irreversible electromagnetic interference shielding alertor through electrochemical oxidation of MXene films. In contrast with static electromagnetic interference shielding, our method offers opportunities to achieve active modulation that can adapt to demanding environments.
Two-dimensional transition metal carbides, nitrides and carbonitrides, popular by the name MXenes, are a promising class of materials as they exhibit intriguing optical, optoelectronic and ...electrochemical properties. Taking advantage of their metallic conductivity and hydrophilicity, titanium carbide MXenes (Ti
3
C
2
T
x
and others) are used to fabricate solution processable transparent conducting electrodes (TCEs) for the design of three-electrode electrochromic cells. However, the tunable electrochromic behavior of various titanium-based MXene compositions across the entire visible spectrum has not yet been demonstrated. Here, we investigate the intrinsic electrochromic properties of titanium-based MXenes, Ti
3
C
2
T
x
, Ti
3
CNT
x
, Ti
2
CT
x
, and Ti
1.6
Nb
0.4
CT
x
, where individual MXenes serve as a transparent conducting, electrochromic, and plasmonic material layer. Plasmonic extinction bands for Ti
3
C
2
T
x
, Ti
2
CT
x
and Ti
1.6
Nb
0.4
CT
x
are centered at 800, 550 and 480 nm, which are electrochemically tunable to 630, 470 and 410 nm, respectively, whereas Ti
3
CNT
x
shows a reversible change in transmittance in the wide visible range. Additionally, the switching rates of MXene electrodes with no additional transparent conductor electrodes are estimated and correlated with the respective electrical figure of merit values. This study demonstrates that MXene-based electrochromic cells are tunable in the entire visible spectrum and suggests the potential of the MXene family of materials in optoelectronic, plasmonic, and photonic applications, such as tunable visible optical filters and modulators, to name a few.
Two-dimensional transition metal carbides, nitrides and carbonitrides, popular by the name MXenes, are an emerging class of materials for tunable plasmonic electrochromic applications.
Carbon nanotube–ZnO composite powders, which act as high-temperature electromagnetic wave absorbents, are prepared by homogeneous precipitation. Carbon nanotube–ZnO/glass composites are fabricated by ...pressureless sintering. ZnO nanoparticles are assembled on the surface of carbon nanotubes, which produces heterostructure and enhances polarization at heterogeneous interface. Owing to the consumption of an amorphous carbon layer on the outer surface of carbon nanotubes and the generation of oxygen vacancies in ZnO during sintering, a higher concentration of charge carriers is produced in ZnO, which causes more relaxation polarization and dielectric loss in electromagnetic field. Owing to the shortened relaxation time, and the increase of relaxation polarization, permittivity and dielectric loss increases with the increase in testing temperature. Reflection coefficient of the obtained composite reaches −70dB. The special integration of multiwalled carbon nanotubes modified with some metal oxide semiconductor nanoparticles provides an effective approach to design high-temperature electromagnetic absorbing materials.
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