Atomic Layer Tailoring Titanium Carbide MXene To Tune Transport and Polarization for Utilization of Electromagnetic Energy beyond Solar and Chemical Energy

Broadband microwave absorber constructed by reduced graphene oxide/La0.7Sr0.3MnO3 composites

High-performance microwave absorbing materials require optimized impedance matching and high attenuation ability. Here we meet the challenge by incorporating electric loss with magnetic loss materials to prepare carbon-based/magnetic hybrids. The reduced graphene oxide (rGO)/La0.7Sr0.3MnO3 (LSMO) composites were prepared by dispersing the LSMO powders into 4.25, 6.25, 8.16, and 10 wt% of the graphene oxide aqueous solution, then the rGO/LSMO composites were formed by hydrothermal method. The pure rGO, LSMO, and rGO/LSMO composites were studied using X-ray diffraction and SEM. Microwave absorption properties were investigated by using coin method. Simulation studies show that 6.25 wt% of rGO/LSMO in a wax matrix exhibits the strongest reflection loss of -47.9 dB @ 10.7 GHz at a thickness of 2.5 mm. Moreover, the effective absorption bandwidth with the reflection loss below -10 dB is up to 14.5 GHz, ranged from 3.5 to 18 GHz for the composites with a thickness of 1.5-5.5 mm, due to a synergism between dielectric loss of rGO and magnetic loss of magnetic LSMO, which is an interesting exploration in the applications of rGO and LSMO. This method can be extended to design and fabricate hybrid absorbers with effective microwave absorption.

An investigation of microstructural, magnetic and microwave absorption properties of multi-walled carbon nanotubes/Ni0.5Zn0.5Fe2O4

The enhancement of microwave absorbing properties in nickel zinc ferrite (Ni_0.5Zn_0.5Fe₂O₄) via multiwall carbon nanotubes (MWCNT) growth is studied in this research work. Ni_0.5Zn_0.5Fe₂O₄ was initially synthesized by mechanical alloying followed by sintering at 1200 °C and the microstructural, electromagnetic and microwave characteristics have been scrutinized thoroughly. The sintered powder was then used as a catalyst to grow MWCNT derived from chemical vapor deposition (CVD) method. The sample was mixed with epoxy resin and a hardener for preparation of composites. The composite of multi-walled carbon nanotubes/Ni_0.5Zn_0.5Fe₂O₄ shown a maximum reflection loss (RL) of −19.34 dB at the frequency and bandwidth of 8.46 GHz and 1.24 GHz for an absorber thickness of 3 mm for losses less than −10 dB. This acquired result indicates that multi-walled carbon nanotubes/Ni_0.5Zn_0.5Fe₂O₄ could be used as a microwave absorber application in X-band.

Large-Scale Synthesis of Three-Dimensional Reduced Graphene Oxide/Nitrogen-Doped Carbon Nanotube Heteronanostructures as Highly Efficient Electromagnetic Wave Absorbing Materials

Herein, we use reduced graphene oxide as a substrate and NiFe as a catalyst to fabricate three-dimensional (3D) nitrogen-doped carbon nanotube (NCNT)/reduced graphene oxide heteronanostructures (3D NiFe/N-GCTs). The 3D NiFe/N-GCTs are composed of two-dimensional (2D) reduced graphene oxide-supported one-dimensional (1D) NiFe nanoparticle-encapsulated NCNT arrays. The NCNTs exhibit bamboo-like shapes with the length and diameter of 3-10 μm and 15-45 nm, respectively. Besides integration of advantages of 1D and 2D nanomaterials, the 3D NiFe/N-GCT heteronanostructure possesses interconnected network structures, sufficient interfaces, numerous defects, hundreds of void spaces enclosed by bamboo joints and the walls of the NCNT in an individual carbon nanotube, and large surface areas, which can improve their dielectric losses toward electromagnetic wave. Thus, the 3D NiFe/N-GCTs show satisfied property toward electromagnetic wave absorption. Typically, the optimized 3D NiFe/N-GCT displays excellent minimal reflection loss (-40.3 dB) and outstanding efficient absorption bandwidth (4.5 GHz), outperforming most of the reported absorbers. Remarkably, the synthesis of 3D NiFe/N-GCTs only involves vacuum freeze-drying and subsequent thermal treatment process at a high temperature, and thus, the large-scale production of 3D NiFe/N-GCTs can be achieved in each batch, affording the possibility of the practical applications of the 3D NiFe/N-GCTs.

Ultrathin and Flexible CNTs/MXene/Cellulose Nanofibrils Composite Paper for Electromagnetic Interference Shielding

As the rapid development of portable and wearable devices, different electromagnetic interference (EMI) shielding materials with high efficiency have been desired to eliminate the resulting radiation pollution. However, limited EMI shielding materials are successfully used in practical applications, due to the heavy thickness and absence of sufficient strength or flexibility. Herein, an ultrathin and flexible carbon nanotubes/MXene/cellulose nanofibrils composite paper with gradient and sandwich structure is constructed for EMI shielding application via a facile alternating vacuum-assisted filtration process. The composite paper exhibits outstanding mechanical properties with a tensile strength of 97.9 ± 5.0 MPa and a fracture strain of 4.6 ± 0.2%. Particularly, the paper shows a high electrical conductivity of 2506.6 S m^-1 and EMI shielding effectiveness (EMI SE) of 38.4 dB due to the sandwich structure in improving EMI SE, and the gradient structure on regulating the contributions from reflection and absorption. This strategy is of great significance in fabricating ultrathin and flexible composite paper for highly efficient EMI shielding performance and in broadening the practical applications of MXene-based composite materials.

The Synthesis, Structure, Morphology Characterizations and Evolution Mechanisms of Nanosized Titanium Carbides and Their Further Applications

It is widely known that the special performances and extensive applications of the nanoscale materials are determined by their as-synthesized structures, especially their growth sizes and morphologies. Hereinto, titanium carbides, which show brilliant comprehensive properties, have attracted considerable attention from researchers. How to give full play to their potentials in the light-weight manufacture, microwave absorption, electromagnetic protection, energy conversion and catalyst areas has been widely studied. In this summarized article, the synthesis methods and mechanisms, corresponding growth morphologies of titanium carbides and their further applications were briefly reviewed and analyzed according to their different morphological dimensions, including one-dimensional nanostructures, two-dimensional nanosheets and three-dimensional nanoparticles. It is believed that through the investigation of the crystal structures, synthesis methods, growth mechanisms, and morphology characterizations of those titanium carbides, new lights could be shed on the regulation and control of the ceramic phase specific morphologies to meet with their excellent properties and applications. In addition, the corresponding development prospects and challenges of titanium carbides with various growth morphologies were also summarized.

Self-Assembly Construction of WS2-rGO Architecture with Green EMI Shielding

Accurately tailoring electromagnetic (EM) materials for achieving high-performance EM interference (EMI) shielding is significantly imperative with increasing EM pollution worldwide. Green EMI shielding materials are attracting extensive attention because of the less additional environmental hazard caused by the lower secondary reflection. However, the conflict between high efficiency and eco-friendly nature makes green EMI shielding still challenging. In this work, a new strategy of turning a guest into a host is developed for the first time, and a unique WS₂-rGO architecture of mountain-like wall is constructed successfully achieving efficient and green EMI shielding. The shielding efficiency (SE) is over 20 dB in the investigated frequency range (2-18 GHz) and the maximum was 32 dB with an endearing green index (g_s ≈ 1.0). The efficient and green EMI SE is ascribed to the multilevel structure and intrinsic dielectric properties of the WS₂-rGO architecture, including the synergy of relaxation and conduction, multi-scattering between the interface and void, and the equivalent wedge effect. These results demonstrate that the WS₂-rGO architecture is a promising candidate in EM transducers, microwave imaging, EM protection, and energy devices.

Fabrication of Flexible, Lightweight, Magnetic Mushroom Gills and Coral-Like MXene⁻Carbon Nanotube Nanocomposites for EMI Shielding Application

MXenes, carbon nanotubes, and nanoparticles are attractive candidates for electromagnetic interference (EMI) shielding. The composites were prepared through a filtration technique and spray coating process. The functionalization of non-woven carbon fabric is an attractive strategy. The prepared composite was characterized using X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), scanning electron microscope (SEM), energy-dispersive X-ray spectroscopy (EDX), and Raman spectroscopy. The MXene-oxidized carbon nanotube-sodium dodecyl sulfate composite (MXCS) exhibited 50.5 dB (99.999%), and the whole nanoparticle-based composite blocked 99.99% of the electromagnetic radiation. The functionalization increased the shielding by 15.4%. The composite possessed good thermal stability, and the maximum electric conductivity achieved was 12.5 Scm-1. Thus, the composite shows excellent potential applications towards the areas such as aeronautics, mobile phones, radars, and military.