Low-Cost Carbothermal Reduction Preparation of Monodisperse Fe₃O₄/C Core–Shell Nanosheets for Improved Microwave Absorption

Abstract

This paper demonstrates a facile and low-cost carbothermal reduction preparation of monodisperse FeO/C core-shell nanosheets (NSs) for greatly improved microwave absorption. In this protocol, the redox reaction between sheet-like hematite (α-FeO) precursors and acetone under inert atmosphere and elevated temperature generates FeO/C core-shell NSs with the morphology inheriting from α-FeO. Thus, FeO/C core-shell NSs of different sizes ( a) and FeO/C core-shell nanopolyhedrons are obtained by using different precursors. Benefited from the high crystallinity of the FeO core and the thin carbon layer, the resultant NSs exhibit high specific saturation magnetization larger than 82.51 emu·g. Simultaneously, the coercivity enhances with the increase of a, suggesting a strong shape anisotropy effect. Furthermore, because of the anisotropy structure and the complementary behavior between FeO and C, the as-obtained FeO/C core-shell NSs exhibit strong natural magnetic resonance at a high frequency, enhanced interfacial polarization, and improved impedance matching, ensuring the enhancement of the microwave absorption. The 250 nm NSs-paraffin composites exhibit reflection loss (RL) lower than -20 dB (corresponding to 99% absorption) in a large frequency ( f) range of 2.08-16.40 GHz with a minimum RL of -43.95 dB at f = 3.92 GHz when the thickness is tuned from 7.0 to 1.4 mm, indicating that the FeO/C core-shell NSs are a good candidate to manufacture high-performance microwave absorbers. Moreover, the as-developed carbothermal reduction method could be applied for the fabrication of other composites based on ferrites and carbon.

Multifunctional Organic–Inorganic Hybrid Aerogel for Self‐Cleaning, Heat‐Insulating, and Highly Efficient Microwave Absorbing Material

“…Generally, dielectric loss of a material associates with polarization relaxation and/or conductive loss . The obvious resonant peaks in ε″ curves indicate the presence of multiple polarization relaxation behaviors, which could be further confirmed by plotting the ε′ versus ε″ curve according to the Debye relaxation theory: (ε′ − ε ∞ ) 2 + (ε′′) 2 = (ε s − ε ∞ ) 2 . As observed in Figure S5 (Supporting Information), the ε′–ε″ curves for PCF‐2, PCF‐3, and PCF‐4 exhibit overlapped Cole–Cole semicircles, each of which represents one Debye relaxation process .…”

High‐Performance Microwave Absorption of MOF‐Derived Core‐Shell Co@N‐doped Carbon Anchored on Reduced Graphene Oxide

“…According to quarter-wavelength theory, with the thickness increasing, the maximum absorption peaks shift towards a lower frequency. Tuning the thickness from 1 to 5 mm, the range of effective absorption bandwidth of Co@NC@RGO-1 and Co@NC@RGO-2 could reach up to as wide as 13.9 GHz (from 4.1 to 18 GHz), while the Co@NC@RGO-3 could cover 14.3 GHz (from 3.7 to 18 GHz), covering 89.4% of the whole microwave band (2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18) (Figure 6a-c). Figure 6d gives the effective bandwidth of more than 3 GHz with optimized respective thickness (from 2.0 to 3.0 nm).…”

“…In fact, many researchers have proved that the absorbents with single composition and structure were unable to meet the application demand. Recently, dielectric and magnetic nanohybrids, such as, Co/C composites, [4][5][6][7][8] Fe 3 O 4 / C coreÀ shell nanosheets, [9][10] CoÀ C/MWCNTs composites, [11] RGO-MnFe 2 O 4 nanocomposites [12] and NiO/RGO [13] have been applied in electromagnetic wave loss field.…”

Synergetic dielectric loss and magnetic loss towards superior microwave absorption through hybridization of few-layer WS2 nanosheets with NiO nanoparticles

“…However, ''big data" level EM pollution is not merely limiting the application of electronic devices, but also endangering human health [1][2][3][4][5][6]. The key problem in reducing and controlling EM pollution is the development of EM absorbing (EMA) materials [7,8], which, in a rapidly developing society, should have the characteristics of light weight, strong absorption ability, wide absorption frequencies, and small thickness [9][10][11][12].…”