Chemical Ni–C Bonding in Ni–Carbon Nanotube Composite by a Microwave Welding Method and Its Induced High-Frequency Radar Frequency Electromagnetic Wave Absorption

Abstract

In this work, a microwave welding method has been used for the construction of chemical Ni-C bonding at the interface between carbon nanotubes (CNTs) and metal Ni to provide a different surface electron distribution, which determined the electromagnetic (EM) wave absorption properties based on a surface plasmon resonance mechanism. Through a serial of detailed examinations, such as X-ray diffraction, scanning electron microscopy, transmission electron microscopy, high-resolution transmission electron microscopy, X-ray photoelectron spectroscopy, and Raman spectrum, the as-expected chemical Ni-C bonding between CNTs and metal Ni has been confirmed. And the Brunauer-Emmett-Teller and surface zeta potential measurements uncovered the great evolution of structure and electronic density compared with CNTs, metal Ni, and Ni-CNT composite without Ni-C bonding. Correspondingly, except the EM absorption due to CNTs and metal Ni in the composite, another wide and strong EM absorption band ranging from 10 to 18 GHz was found, which was induced by the Ni-C bonded interface. With a thinner thickness and more exposed Ni-C interfaces, the Ni-CNT composite displayed less reflection loss.

Dopamine-derived cavities/Fe3O4 nanoparticles-encapsulated carbonaceous composites with self-generated three-dimensional network structure as an excellent microwave absorber

“…As is known, the relative complex permittivity (3 r ¼ 3 0 À j3 00 ) and permeability (m r ¼ m 0 À jm 00 ) determine the microwave absorption performance. 40 Usually, the real parts of the complex permittivity (3 0 ) and permeability (m 0 ) correspond to the storage capability of electric and magnetic energy, while the imaginary parts (3 00 and m 00 ) represent the dissipation capability of electric and magnetic energy. 41 Fig.…”

Fabrication of 3D Hierarchical Byttneria Aspera‐Like Ni@Graphitic Carbon Yolk–Shell Microspheres as Bifunctional Catalysts for Ultraefficient Oxidation/Reduction of Organic Contaminants

“…According to the above experimental results and analysis, a possible MW‐driven reaction mechanism is put forward to account for the superior catalytic activity over Ni@GC ( Scheme a). It was proposed that LSPR can occur due to a good matching between frequency of exciting electromagnetic wave and that of surface free electron cloud oscillating to resist the restoring force of positive nuclei, which can markedly improve the MW‐harvesting capability of nanosized plasmonic metallic Ni . Thus, upon MW irradiation, through the LSPR excitation of plasmonic Ni NPs, the energetic electrons (hot electrons) are redistributed to the surface plasmon (SP) states above the Fermi level ( E f ), thereby leaving positively charged h + below E f .…”

“…It was proposed that LSPR can occur due to a good matching between frequency of exciting electromagnetic wave and that of surface free electron cloud oscillating to resist the restoring force of positive nuclei, which can markedly improve the MW-harvesting capability of nanosized plasmonic metallic Ni. [13] Thus, upon MW irradiation, through the LSPR excitation of plasmonic Ni NPs, the energetic electrons (hot electrons) are redistributed to the surface plasmon (SP) states above the Fermi level (E f ), thereby leaving positively charged h + below E f . [58] Meanwhile, the plasmon-excited hot electrons can rapidly migrate to the surface of contiguous carbon matrix, and subsequently transfer to e − acceptors such as O 2 to form •O 2 − which can directly oxidize organic pollutants or turn into reactive •OH.…”

“…[7] Therefore, seeking for suitable and efficient catalysts has become intensively pursued.In terms of MW-driven catalysis, various MW-absorbing materials, including activated carbon, [8] carbon nanotubes (CNTs), [9] polymers, [10] metal nanoparticles (NPs), [11] as well as metal oxides [12] have been exploited for the elimination of organic pollutants. As a sort of significant MW-absorbing material, transition metal NPs, [13] especially Ni, Co, and Fe NPs, are expected to be extensively applied owing to their high surface reactivity, low cost, abundant reserve, and facile magnetic recovery, whose MW-absorbing ability is even higher than that of their corresponding oxides. [14] Nevertheless, several major drawbacks of bare transition metal NPs, namely, the fast oxidation deactivation in air, [15] magnetically induced aggregation and rapid recombination of the localized surface plasmon resonance (LSPR)-generated electrons (e − )-hole (h + ) pairs, [16] seriously restrain their catalytic activity and reusability, therefore their practical applications.Likewise, transition metal NPs instead of noble metals demonstrated excellent catalytic reduction activities for the hydrogenation, reduction of oxygen, as well as hydrogen evolution, [17][18][19] while the use alone also suffers from the similar constraints.…”

Solid and macroporous Fe3C/N-C nanofibers with enhanced electromagnetic wave absorbability

“…In recent years, with the increasing attention on the prevention and control of electromagnetic pollution and the increasing requirements of military weapons, microwave absorbing samples with a low thickness, light density, high reflection loss at a wide frequency range and corresponding stealth technology are urgently needed 7 – 9 . And a number of studies have endeavored to the development of such materials 10 , 11 . For example, the flower-like CuS hollow materials were successfully prepared by a simple solvothermal procedure.…”