Core‐shell structured iron‐containing ceramic nanoparticles: Facile fabrication and excellent electromagnetic absorption properties

Abstract

In this work, novel core‐shell structured Fe3Si@C/SiC/Fe3O4/SiO2 nanoparticles were fabricated via a polymer‐derived ceramic approach, starting from sol‐like polycarbosilane‐encapsulated polynuclear carbonyl iron nanoparticles and with pitch as an isolator to avoid aggregation during polymer‐to‐ceramic transformation. Elemental analysis, X‐ray photoelectron spectroscopy, X‐ray diffraction, transmission electron microscope, vibrating sample magnetometer and vector network analyzer were employed to investigate the composition, nano/microstructure, morphology, and dielectric/magnetic properties. The results show that the size of obtained Fe3Si@C/SiC/Fe3O4/SiO2 nanoparticles is in the range of 2‐200 nm. And the unique core‐shell structure with the hetero‐interface combined with simultaneous dielectric and magnetic loss endow Fe3Si@C/SiC/Fe3O4/SiO2 nanoparticles outstanding electromagnetic (EM) wave absorbing performance. With a sample thickness of 4.5 mm, the minimum reflection coefficient (RC) of the composites Fe3Si@C/SiC/Fe3O4/SiO2 mixed with paraffin wax reaches −44.7 dB, indicating that more than 99.99% EM waves can be attenuated by the composites. By adjusting the sample thicknesses, the effective bandwidth (the bandwidth of RC values lower than −10 dB) amounts 9.5 GHz (from 2.5 to 12.0 GHz), covering the whole C and X bands.

Polymer‐derived Co2Si@SiC/C/SiOC/SiO2/Co3O4 nanoparticles: Microstructural evolution and enhanced EM absorbing properties

“…Due to the unique core-shell structure, complex phase composition in the shell and in situ formed mesopores, the obtained Co 2 Si@SiC/C/SiOC/SiO 2 /Co 3 O 4 nanoparticles-paraffin composites possess outstanding EMW absorption properties as follows: (a) In the X-band, the lowest RC min reaches −60.9 dB with a sample thickness 1.73 mm and the widest EAB is 3.50GHz with a sample thickness 1.85 mm; (b) With a ultra-small thickness 1.25mm, the EAB can cover 4.8 GHz in the high-frequency range (13.2-18 GHz); (c) by adjusting the matching thickness, the EAB amounts 15.5 GHz (from 2.5 to 18 GHz), showing enhanced EMW absorbing performance in the whole-frequency range compared with the recently reported Fe 3 Si@C/SiC/Fe 3 O 4 /SiO 2 nanoparticles. 22 In summary, our novel core-shell structured Co 2 Si@SiC/C/ SiOC/SiO 2 /Co 3 O 4 ceramic nanoparticles not only possess advanced functional properties, but also meet a series of requirements such as high-temperature resistance, light weight, and thin thickness, which provide a feasible scheme for designing EMW absorption materials applied in harsh environments.…”

“…Finally, Co‐containing ceramic nanoparticles were successfully synthesized by the decarburization treatment (eg, oxidation at in an air atmosphere at 500°C). As reported in our previous work, 21‐22 the formation mechanism of the Co‐containing sol is briefly explained as follows: (a) At first, carbonyl cobalt decomposes into active intermediates, such as [Co(CO) 4 ] or [Co(CO) 3 ], and simultaneously releases CO. (b) During the preparation of the Co‐colloid, Si–H bonds in the polycarbosilane (PCS) will be preferentially catalyzed by active Co‐containing intermediates to form Si–CH 2 –Si and Si–O–Si bonds, which can effectively cross‐link the PCS. (c) Finally, nanosized carbonyl particles (the “core”) are encapsulated by cross‐linked PCS (the “shell”), thus forming the colloid with PCS‐bounded Co particles.…”

“…In the present work, we explore a cobalt‐containing sol as polymeric precursors, similar to the previous work, 22 carbon‐rich cobalt‐containing ceramic nanoparticles with both nanoporous and core‐shell structure were successfully synthesized by ingenious utilizing the mechanism of high‐temperature carbothermal reduction reaction and oxidation in the carbon‐rich system 23 . In addition, the composition and structural evolution of ceramic nanoparticles before and after carbon removal were systematically studied, and the relationship based on structure‐property of obtained Co‐containing ceramic nanoparticles was established.…”

“…19 Recently, we have developed a novel sollike precursor which can be used not only to synthesize EMA SiC fibers, but also to fabricate core-shell nanoparticles. [20][21][22] Using iron-containing sol as the raw material and pitch as the isolator, the unique core-shell structured Fe 3 Si@C/SiC/Fe 3 O 4 / SiO 2 nanoparticles were prepared, which preliminarily proves the feasibility of PDC approach combined with pitch as the isolator for the fabrication of core-shell nanoparticles. 22 In the present work, we explore a cobalt-containing sol as polymeric precursors, similar to the previous work, 22 carbon-rich cobalt-containing ceramic nanoparticles with both nanoporous and core-shell structure were successfully synthesized by ingenious utilizing the mechanism of high-temperature carbothermal reduction reaction and oxidation in the carbon-rich system.…”

“…[20][21][22] Using iron-containing sol as the raw material and pitch as the isolator, the unique core-shell structured Fe 3 Si@C/SiC/Fe 3 O 4 / SiO 2 nanoparticles were prepared, which preliminarily proves the feasibility of PDC approach combined with pitch as the isolator for the fabrication of core-shell nanoparticles. 22 In the present work, we explore a cobalt-containing sol as polymeric precursors, similar to the previous work, 22 carbon-rich cobalt-containing ceramic nanoparticles with both nanoporous and core-shell structure were successfully synthesized by ingenious utilizing the mechanism of high-temperature carbothermal reduction reaction and oxidation in the carbon-rich system. 23 In addition, the composition and structural evolution of ceramic nanoparticles before and after carbon removal were systematically studied, and the relationship based on structure-property of obtained Co-containing ceramic nanoparticles was established.…”