Engineering of the Core–Shell Boron Nitride@Nitrogen-Doped Carbon Heterogeneous Interface for Efficient Heat Dissipation and Electromagnetic Wave Absorption

Abstract

The effective integration of multiple functions into electromagnetic waveabsorbing (EWA) materials is the future development direction but remains a huge challenge. A rational selection of components and the design of structures can make the material have excellent EWA performance and heat dissipation. Herein, the core−shell structured boron nitride@nitrogen-doped carbon (BN@NC) is prepared by using waterborne polyurethane (WPU) as the carbon source via a facile pyrolysis treatment process, where NC is used as the conductive loss shell, and BN serves as an impedance matching core and dominant heat transfer media. As a result, the BN@NC-900 filled with paraffin wax yields a minimum reflection loss of −42.2 dB at 2.2 mm and an effective absorbing bandwidth of 4.48 GHz at 1.8 mm, and its thermal conductivity reaches up to 0.92 W/m•K in epoxy resin. Most importantly, flexible BN@NC/WPU films are prepared and simultaneously achieve the dual-functional capability of efficiently dissipating heat and electromagnetic waves (−50.0 dB). Besides, an attractive multiband absorption feature (>99%) from C to Ku bands is realized and a strong absorbing over −27.0 dB at the S band (2.88 GHz) is even achieved. This study may pave a new route for the rational design of multifunctional EWA materials.

Flexible, Stretchable, and Lightweight Hierarchical Carbon-Nanotube-Decorated Carbon Fiber Structures for Microwave Absorption

“…The reflection was measured from the simulation at different thicknesses, which are shown in Figure 8. The shifting of the minimum R L peak toward the lower frequency is observed when the nanocomposite thickness increases from 2.1 to 2.5 mm, which can be understood by the eq 3 of the quarter wavelength 20,23,26,61,65…”

“…The reflection was measured from the simulation at different thicknesses, which are shown in Figure . The shifting of the minimum R L peak toward the lower frequency is observed when the nanocomposite thickness increases from 2.1 to 2.5 mm, which can be understood by the eq of the quarter wavelength ,,,, t normalm = italicnc 4 f m ε normalr μ normalr 0.25em ( n = 1 , 3 , 5 , ··· ) where ε r and μ r are permittivity and permeability, respectively, matching thickness and frequency are t m and f m , respectively, and c is the speed of light. The best result is obtained for CFCNT0.35 at a 2.4 mm thickness, showing a minimum R L value of 52.53 dB covering 100% X band below 10 dB, i.e., an EAB of 4.2 GHz varying from 8.2 to 12.4 GHz and the EAB 20 dB bandwidth of 1.93 GHz is observed from the frequency ranging from 8.58 to 10.51 GHz (∼46% of the X band).…”

“…For this purpose, several high-performing EMA’s have been created in which carbon-based polymer composites are regarded as advantageous and promising candidates for highly efficient EMA with excellent thermal management capacities, lightweight, cost-effective, enhanced electric and heat conductivity, high dielectric loss, high mechanical stability, and excellent corrosion resistance. − However, the ability of the carbon nanofillers to agglomerate in the form of bundles results from the presence of powerful intermolecular van der Waals interaction, deteriorates the capabilities of carbon nanofillers for EM absorption, and restricts their applicability in industrial applications. , For this purpose, various techniques have recently been used to construct carbon-decorated hybrid morphologies consisting of magnetic or dielectric particles. − For example, Bao et al synthesized the bifunctional hollow Fe@C microsphere and fabricated the nanocomposite microwave absorber by mixing Fe@C (60 wt %) in paraffin, displaying a wide EAB of 7.52 GHz (10.48–18 GHz) at a 1.75 mm thickness . Gou et al made a 2.5 mm thickness nanocomposite consisting of polydimethylsiloxane (PDMS)/CeFe 2 O 4 /graphene oxide (GO) (60 wt %) in paraffin (40 wt %) and achieved the minimum R L value of −52 dB with an EAB of 2.1 GHz (Ku band) .…”

“…23) as compared to CF0.05 (tan δ 0.15). The nanocomposites are cut into a dimension of 22.86 × 10.16 mm 2 and backed by metal using copper tape.…”

FeMnC complex derived from hollow FeMn PBA precursor for highly efficient microwave absorption

“…Li Yongfeng et al prepared a core–shell structured boron nitride@nitrogen-doped carbon with an EAB value of 4.48 GHz at 1.8 mm. 27 Meanwhile, multiple interfaces of core–shell provide abundant polarization sites and enhance the multiple reflection loss in microwave absorbents. For example, Yang Zhihong et al fabricated a core–shell SiO 2 @HCS sphere with rich interfaces, which shows an EAB value of 4.8 GHz at 1.5 mm.…”