Ni Chain Hybrid with Excellent

Research Article www.acsami.org

Cite This: ACS Appl. Mater. Interfaces 2019, 11, 25399−25409

Promising Ti3C2Tx MXene/Ni Chain Hybrid with Excellent Electromagnetic Wave Absorption and Shielding Capacity Luyang Liang,† Gaojie Han,† Yang Li,‡ Biao Zhao,§ Bing Zhou,† Yuezhan Feng,*,† Jianmin Ma,∥ Yaming Wang,*,† Rui Zhang,‡,§ and Chuntai Liu†

Downloaded via UNIV OF SOUTHERN INDIANA on July 21, 2019 at 00:32:43 (UTC). See https://pubs.acs.org/sharingguidelines for options on how to legitimately share published articles.

†

Key Laboratory of Advanced Materials Processing & Mold (Ministry of Education), National Engineering Research Center for Advanced Polymer Processing Technology, Zhengzhou University, Zhengzhou 450002, China ‡ School of Materials Science and Engineering, Zhengzhou University, Zhengzhou, Henan 450001, China § Henan Key Laboratory of Aeronautical Materials and Application Technology, School of Materials Science and Engineering, Zhengzhou University of Aeronautics, Zhengzhou, Henan 450046, China ∥ Key Laboratory for Micro-/Nano-Optoelectronic Devices, Ministry of Education, School of Physics and Electronics, Hunan University, Changsha 410022, China S Supporting Information *

ABSTRACT: Electromagnetic (EM) pollution affecting people’s normal lives and health has attracted considerable attention in the current society. In this work, a promising EM wave absorption and shielding material, MXene/Ni hybrid, composed of one-dimensional Ni nanochains and two-dimensional Ti3C2Tx nanosheets (MXene), is successfully designed and developed. As expected, excellent EM wave absorption and shielding properties are obtained and controlled by only adjusting the MXene content in the hybrid. A minimum reflection loss of −49.9 dB is obtained only with a thickness of 1.75 mm at 11.9 GHz when the MXene content is 10 wt %. Upon further increasing the MXene content to 50 wt %, the optimal EM shielding effectiveness (SE) reaches 66.4 dB with an absorption effectiveness (SEA) of 59.9 dB. Mechanism analysis reveals that the excellent EM wave absorption and shielding performances of the hybrid are contributed to the synergistic effect of conductive MXene and magnetic Ni chains, by which, the dielectric properties and electromagnetic loss can be easily controlled to obtain appropriate impedance matching conditions and good EM wave dissipation ability. This work provides a simple but effective route to develop MXene-based EM wave absorption and shielding materials. A universal guideline for designing the absorbing and shielding materials for the future is also proposed. KEYWORDS: Ti3C2Tx MXene, Ni nanochain, synergistic effect, electromagnetic wave absorption, electromagnetic interference shielding

1. INTRODUCTION In the current society, the rapidly expanding use of general electronic communication working in the gigahertz range and wearable electronic devices has inevitably led to increasingly severe electromagnetic (EM) pollution, which not only induced alarming EM interference that degraded the function of precision components, resulting in irreparable loss of valuable stored data, but also released the harmful leaked EM waves that deteriorated the health of living organisms.1,2 On the other hand, high-efficiency EM wave absorption materials for stealth equipment in the military field are also needed to avoid the detection of radar effectively, which has been believed to be one of the keys to ensure the survivability of weapons and equipment on the battlefield.3,4 Therefore, it is precisely desirable for scientists to design and develop the materials with efficient EM wave absorption and shielding capacities.5,6 © 2019 American Chemical Society

It is generally recognized that EM wave absorbing materials are characterized by small reflection and transmission. The permittivity, permeability, conductivity, and matching conditions of materials are usually deemed to be decisive factors for their EM wave absorption and shielding performance. Clearly, the impedance matching of absorbing materials can be regulated via tuning the EM parameters, resulting in more EM waves to be injected into the materials.7−10 Then, the absorbing EM waves are dissipated by dielectric loss or magnetic loss. In general, the absorbing materials with a single dielectric loss or magnetic loss mechanism is always limited to meet the requirements in terms of broadband, thin thickness, lightweight, and high-efficiency. Thus, incorporating two or Received: April 26, 2019 Accepted: June 19, 2019 Published: June 19, 2019 25399

DOI: 10.1021/acsami.9b07294 ACS Appl. Mater. Interfaces 2019, 11, 25399−25409

Research Article

ACS Applied Materials & Interfaces

Figure 1. Schematic illustration of the fabrication of MXene/Ni hybrids.

ratio can form electrical/magnetic conductive networks in composites more easily.28 Unfortunately, there is yet no report about mono or few-layered Ti3C2Tx, which has been widely used to prepare polymer-based EM shielding composites with devisable structures,29−31 combining with 1D magnetic substances to improve its EM wave absorption and shielding capacity. In this work, highly efficient EM wave absorption and shielding hybrids were successfully synthesized by combining 2D Ti3C2Tx MXene nanosheets and 1D Ni nanochains. The impedance matching and conductivity of the hybrid can be easily controlled by means of merely changing the MXene content. More importantly, it revealed that the excellent EM properties of MXene/Ni hybrids are mainly due to the synergistic effects induced by the permittivity of MXene sheets and the permeability of Ni chains. Furthermore, the related mechanisms of dipole polarization, interfacial polarization, natural resonance, and eddy current loss between hybrids and EM waves are expounded in detail. Based on the systematic comparison, a possible phase diagram of the relationship between conductor/magnet components and the EM wave absorption and shielding properties is proposed, which may provide a design principle to prepare EM wave absorption and shielding materials.

multiple materials with synergistic absorption effects of dielectric and magnetic losses has been widely accepted as an ideal approach to effectively regulate EM parameters. In this aspect, various composites composed of conductors and magnets have been successfully designed in previous reports, such as Fe3O4/C,11 Fe3O4/rGO,12 Co/TiO2,13 Ni@SnO2,14 Ni@void@SnO2,15 CNT-Fe/Co/Ni,16 and so on. However, unlike EM absorbing materials, strong surface EM wave reflection-induced impedance mismatching is equally important with internal EM absorption for the high EM shielding performance.17 Therefore, balancing the matching condition and conductivity by adjusting the conductor/magnet component ratio is the key to design high-performance EM wave absorption and shielding materials. Recently, two-dimensional (2D) MXenes, prepared by selectively etching the “A” element in the MAX phase with a general formula of Mn+1XnTx (n = 1, 2, 3), where M represents a transition metal (i.e., Ti, Mo, and V), X denotes C or N, Tx represents a terminal oxygen or fluorine-containing functional group,18−20 have been proven to be of great potential in the field of EM wave absorption and shielding materials because of the intrinsic superior conductivity, native defects, and surface chemical activity. However, pure MXene is unsatisfactory as the EM absorbing material due to its ultrahigh conductivity, although it has been reported.21 For this reason, MXene is often combined with other materials to improve its impedance matching. Typically, Qian et al. fabricated a novel urchin-like ZnO/Ti3C2Tx hybrid via a co-precipitation method, and its 75 wt % composite with paraffin exhibited a minimum reflection loss (RL) value of −26.3 dB at 17.4 GHz.22 Zhao et al. designed a novel 2D Ti3C2Tx MXenes/nanocarbon sphere hybrid, exhibiting an optimum RL of −54.67 dB at 3.97 GHz with a thickness of 4.8 mm.23 In the field of shielding material preparation, for example, the 100 wt % Ti3C2Tx (MXene) film exhibited an amazing shielding effectiveness (SE) value of 92 dB in the range of 8−12.4 GHz.5 Yin et al. reported that the 90 wt % paraffin/MXene composites showed a high SE value of 76.1 dB with a thickness of only 1 mm.20 In view of the significance of the synergy between permeability and magnetic loss in EM absorbing and shielding performance, combining the magnetic component into MXene is also supposed to be a feasible approach to overcome its drawback. In this respect, zero-dimensional (0D) Fe3O4 or Ni nanoparticles have been used to improve the EM absorbing capacity of multilayered MXene by in-situ intercalation synthesis.24 In contrast to 0D nanoparticles, the nanoparticles with a one-dimensional (1D) structure have been proven to have more excellent magnetic performance due to the magnetic enhancement effect caused by the anisotropic shape. 1D magnetic nanochains or nanowires are often expected to be the antenna to receive more EM waves and induce the point charge to dissipate the EM wave energy.25−27 Furthermore, compared to nanoparticles, metal nanochains or nanofibers with a high aspect

2. EXPERIMENTAL SECTION 2.1. Materials. MAX parent phases, titanium aluminum carbide (Ti3AlC2, 400 mesh), were purchased from Jilin 11 Technology Co., Ltd. Lithium fluoride (LiF) was obtained from Aladdin Reagent Co., Ltd. Nickel chloride hexahydrate (NiCl2·6H2O), hydrazine hydrate (N2H4·H2O), hydrochloric acid (HCl), sodium hydroxide (NaOH), ethylene glycol (EG), ethanol, paraffin, and poly(vinylpyrrolidone) (PVP) were provided from Sinopharm Chemical Reagent Co., Ltd. (China). Deionized water used in all experiments was made in our laboratory. All chemical reagents were used directly from commercial suppliers without further processing. 2.2. Preparation of Ni Nanochains. Ni nanochains were prepared by a combination of a soft stencil and a magnetic field assist. Briefly, 0.3 g of NiCl2·6H2O was first dissolved into 50 mL of EG with magnetic stirring for 30 min. Then, 1 g of PVP and 0.04 g of NaOH were added into the NiCl2 solution with stirring for 30 min. Here, PVP mainly plays the role of a soft template. After complete dissolution, 1 mL of N2H4·H2O was injected into the system with stirring for 10 min. The reaction vessel was kept at 80 °C for 1 h under the action of a parallel magnetic field. The resulting products (Ni nanochains) were washed with deionized water and ethanol several times, respectively, and finally dried at 50 °C under vacuum. 2.3. Synthesis of Mono or Few-Layered Ti3C2Tx MXenes. Ti3C2Tx MXenes were synthesized based on the previous literature.29 Typically, 2 g of LiF powder was slowly added into 40 mL of 9 M HCl solution in a Teflon container and moderately stirred for 30 min until it was completely dissolved. Then, 2 g of Ti3AlC2 powder was tardily added to the mixture over 10 min. The reaction mixture was kept at 35 °C for 24 h with stirring, after which the obtained multilayer Ti3C2Tx (m-Ti3C2Tx) was washed with deionized water by centrifuged (3500 rpm) several times, until its pH reached 6. Then, 25400


Research Article


Figure 2. (a) XRD patterns of Ti3C2Tx MXene, Ni chain, and MXene/Ni hybrid. (b) High-resolution XPS spectra of Ti3C2Tx MXene at the Ti 2p region. (c) FTIR spectra of Ni-10% MXene and Ti3C2Tx MXenes. (d) Magnetic hysteresis loops of the Ni chain and Ni-10% MXene at room temperature. m-Ti3C2Tx was exfoliated to few-layered Ti3C2Tx (f-Ti3C2Tx) by sonication (180 W, 20 min). After that, the dark-green solution was centrifuged at 3500 rpm for 3 min to obtain f-Ti3C2Tx nanosheets. 2.4. Fabrication of Ti3C2Tx MXene/Ni Chain Hybrids. Ti3C2Tx MXene/Ni chain hybrids were fabricated by a one-step hydrothermal process. As shown in Figure 1, a certain amount of synthesized Ni chains were ultrasonically dispersed into f-Ti3C2Tx aqueous solution with different content ratios in a reaction vessel for 30 min. Subsequently, the mixture was transferred to a Teflon-lined autoclave and heated to 60 °C for 4 h to ensure good dispersion. Finally, the MXene/Ni hybrids were obtained by centrifugation, washing, and lyophilization. To study the effect of the Ti3C2Tx MXene content on the absorbing and shielding properties of hybrids, paraffin-based composites with hybrids were prepared with fixed 10 wt % Ni chains and various MXene contents. For convenience, the paraffin composite with x wt % MXene is marked as Ni-x % MXene. 2.5. Characterization. The microscopic morphologies of the MXene, Ni chain, and hybrids were characterized by a field emission scanning electron microscope (FE-SEM, JSM-7001F). Elemental composition was shown by an energy dispersive spectrometer (Oxford Instruments) associated with FE-SEM. The crystal structure was observed by X-ray diffraction (XRD, Rigaku Ultima IV) using Cu Kα radiation (λ = 0.154 nm). Magnetic properties were detected by a vibrating sample magnetometer (VSM, YPC7-VSM-130) at room temperature. X-ray photoelectron spectroscopy (XPS) measurements were carried out using a Thermo ESCALAB 250XI spectrometer using an Al Kα anode. Fourier transform infrared spectroscopy (FTIR) were recorded in the range of 400−4000 cm−1 using a Nicolet 6700 spectrometer. A semiconductor parameter analyzer (HRMS900, Partulab) and a four-point probe device (RTS-2, 4 PROBES TECH) were used to obtain the conductivity of samples. Paraffinbased composites containing MXene/Ni hybrids were pressed into a toroidal shape having an inner diameter of 3.04 mm and an outer diameter of 7.00 mm. The dielectric constant, magnetic permeability, and S-parameters were tested by a network vector analyzer (Agilent 5234A), which were used to simulate the EM wave absorption and shielding performances of hybrids.

Information) show the XRD patterns of the Ti3AlC2 MAX phase, Ti3C2Tx MXene, Ni chain, and Ni-10% MXene hybrid. The characteristic diffraction peaks at 2θ = 6.8, 13.9, 38.7, and 60.5° correspond to the (002), (004), (0010), and (110) crystal planes of Ti3C2Tx MXene, respectively. Compared to Ti3AlC2 (Figure S1a in the Supporting Information), the strong (104) diffraction peak at 39.1° is replaced by a broad peak with low strength due to the elimination of Al after etching. Meanwhile, the (002) peak moves to a lower angle of 6.9° compared to Ti3AlC2 (Figure S1b in the Supporting Information), which confirms the expansion of Ti3C2Tx MXene’s d-spacing.32,33 The diffraction peaks at 2θ = 44.5, 51.8 and 76.3° in the Ni chain spectrum are perfectly indexed to the cubic crystalloid structure (PDF #04-0850). For the MXene/Ni hybrid, the main diffraction peaks corresponding to both Ni chain and Ti3C2Tx MXene can be easily found, illustrating the successful preparation of the MXene/Ni hybrid without any crystal structure changes. The XPS spectrum was employed to confirm the chemical structure of the hybrid. The main peaks corresponding to the Ti, C, O, and F elements, respectively, are observed in Figure S2a in the Supporting Information, suggesting that O and F containing groups were captured onto MXene after LiF/HCl etching. The high-resolution Ti 2p XPS spectrum (Figure 2b) reveals four fitting peaks at ∼455.6, 459.6, 461.6, and 465.4 eV, corresponding to C−Ti−Tx (2p3/2), Ti−O (2p3/2), C−Ti−Tx (2p1/2), and Ti−O (2p1/2) bonds, respectively.34−36 Combining the high-resolution C 1s and O 1s XPS spectra (Figure S2b,c in the Supporting Information), it can be concluded that the abundant Ti−OH, Ti−O, and C−F groups were introduced onto MXene during the etching process, which endows Ti3C2Tx with high hydrophilicity and strong negative charges. The FTIR spectrum (Figure 2c) of Ti3C2Tx reveals the typical peaks at 3435, 1635, and 550 cm−1, corresponding to the terminal groups of −OH, Ti−O, and C−F, respectively, which is in agreement with the XPS results.37,38 After mixing with Ni chains, obvious weakening and shifting for hydroxyl are found in the FTIR spectrum of the MXene/Ni hybrid, which may be attributed to the hydrogen-bond interaction

3. RESULTS AND DISCUSSION 3.1. Structure and Morphology of MXene/Ni Hybrid. Powder XRD measurements were employed to detect the crystal structure of the hybrid. Figures 2a and S1 (Supporting 25401


Research Article


Figure 3. SEM images of (a, b) Ni chains with different magnifications, (c) Ti3C2Tx MXenes, (d) Ni-10% MXene, (e) Ni-30% MXene, and (f) Ni50% MXene. (g1) SEM of the MXene/Ni hybrid and its corresponding elemental mapping images of (g2) Ni, (g3) Ti, and (g4) C elements.

thickness. The accurate thickness detected by an atomic force microscope (Figure S4b in the Supporting Information) is calculated to be only approximately 2−3 nm, which is very close to the thickness of a single layer Ti3C2Tx MXene. Figure 3d−f exhibits the morphologies of Ni-10% MXene, Ni-30% MXene, and Ni-50% MXene hybrids, respectively. Transparent and ultrathin Ti3C2Tx nanosheets with corrugated structures are observed in all hybrids, and Ni nanochains are closely and uniformly loaded or embedded in Ti3C2Tx sheets. With the increase of the MXene content, more uniform dispersion of Ni chains and stronger interaction between them are found due to increasing hydrogen bonds and steric hindrance effects. Moreover, the element mapping analysis corresponding to the MXene/Ni hybrid (Figure 3g1) further reveals the uniform distribution of Ni (Figure 3g2), Ti (Figure 3g3), and C (Figure 3g4) elements in the hybrid. To better represent the microstructure of the MXene/Ni hybrid, transmission electron microscopy (TEM) and high-resolution TEM characterization of the composite were adopted. As shown in Figure S5a (Supporting Information), Ni nanochains with interesting irregular structures are closely coated by wrinkled MXene sheets (an almost transparent structure). Such coating results in the huge increase of the interface, which is in favor of the interfacial polarization effect in an alternative electromagnetic field. From its high-resolution TEM image (Figure S5b, Supporting Information), the uniform and well-defined interplanar spacings of 0.353 and 0.206 nm, corresponding to the (002) plane of Ti3C2Tx sheets and the (111) plane of facecentered-cubic Ni crystals, are consistent with the XRD analysis. Moreover, the clear interfacial boundary between MXene and Ni also confirms their noncovalent linking without chemical interaction. 3.2. Dielectric Properties and Permeability of MXene/ Ni Hybrid. By and large, the EM wave absorption capability of a material is largely depended on the relative complex permittivity and complex permeability. Figure 4 displays the

between the terminal groups of MXene and residual PVP on Ni chains and shortens the distance between oxygen. The detailed reaction process between MXene and the Ni chain of hydroxyl migration in the FTIR spectrum as well as UV spectra are also shown in Figure S3a,b in the Supporting Information. Besides, the similar functional groups between the Ti3C2Tx and MXene/Ni hybrid confirm the stable chemical structure of the hybrid. Moreover, these functional groups are capable of forming more polarization centers by the application of an alternating EM field.39 The field dependence of magnetization of the Ni nanochain and the MXene/Ni hybrid is shown in Figure 2d. The magnetic performance parameters including saturation magnetization (Ms), coercive force (Hc), and residual magnetic induction (Mr) can be obtained from VSM curves. The Ni chain presents a standard S-shaped hysteresis loop with good coercivity and residual magnetic induction with Ms and Hc of 13.2 emu g−1 and 182 Oe, respectively, indicating its saturating reversible ferromagnetic behavior at room temperature. Its coercivity is greater than other 1D nanostructured materials reported in the literature, such as Ni nanofibers (124 Oe) and hollow Ni chains (45 and 31 Oe).40,41 In contrast, the saturation magnetization of Ni-10% MXene hybrid decreases significantly due to the introduction of nonferromagnetic Ti3C2Tx MXene. The magnetic loss capability is supported by the magnetic properties of the MXene/Ni hybrid, which promotes EM wave absorption and shielding performance. The morphologies of Ni nanochains, Ti3C2Tx nanosheets, and MXene/Ni hybrids are observed by an SEM technique. As presented in Figure 3a, a distinct chain-like structural Ni with a length of about 20 μm was easily obtained. High magnification SEM reveals (Figure 3b) that the Ni nanochains are composed of close connective Ni particles with a diameter of ∼300 nm. Figures 3c and S4a (Supporting Information) suggest that the exfoliated Ti3C2Tx nanosheets show a wrinkled and crumpled lamellar structure with large side length (>3 μm) and ultrathin 25402


Research Article


Figure 4. Frequency dependence of (a, c) real and (b, d) imaginary parts of relative (a, b) complex permittivity (ε′, ε″) and (c, d) complex permeability (μ′, μ″) of Ni-2.5% MXene, Ni-5% MXene, Ni-10% MXene, Ni-20% MXene, and Ni-30% MXene.

Figure 5. (a, b) Frequency dependence of tan δμ + tan δε and attenuation constant of Ni-2.5% MXene, Ni-5% MXene, Ni-10% MXene, Ni-20% MXene, and Ni-30% MXene.

real (ε′, μ′) and imaginary (ε″, μ″) parts of complex permittivity and complex permeability for MXene/Ni hybrids with different Ti3C2Tx contents in the frequency range of 2−18 GHz. It is well-known that the real parts (ε′, μ′) and the imaginary parts (ε″, μ″) represent the ability of storing and dissipating electrical and magnetic energies of EM waves, respectively. As exhibited in Figure 4a,b, the increase of the MXene content in hybrids results in continuous improvement in the values of both ε′ and ε″ during the whole frequency band due to the formation of more capacitor-like structures in the MXene/Ni hybrid. However, negative ε′ (Figure S6a in the Supporting Information) was found upon further increasing the Ti3C2Tx content more than 40 wt % because the intensity of the polarized EM field induced by accumulated charges exceeds that of the original EM field.42,43 As is well-known, the resonance behavior of dielectric materials is mainly related to ion polarization, interfacial polarization, electron polarization, dipole polarization, and space-charge polarization.44,45 Among them, electron and ion polarizations are usually generated in specific frequency bands, such as PHz and THz.46 In this case, the increased ε′ for the hybrid with a high MXene content is mainly ascribed to the reinforcement in the dipole polarization caused by the functional groups and defects of Ti3C2Tx sheets, and the interfacial polarization between Ti3C2Tx sheets and Ni chains and the space-charge polarization in the absorber. Under the excitation of EM waves, the polarization relaxation

behaviors caused by charge redistribution between Ti3C2Tx sheets and Ni chains result in the high ε″ shown in Figures 4b and S6b (Supporting Information). The ε″ value at whole tested frequency increases obviously by increasing the MXene content in hybrids. It is not difficult to understand that more Ti3C2Tx sheets will lead to more conductive paths in the hybrid due to their 2D large surface area and excellent electrical conductivity, further resulting in the conversion from weak jump migration loss of semiconductor to strong delay loss of conductor. Furthermore, the electronic theory (ε″ ≈ 1/ 2πε0ρf, where ρ is the resistivity, ε0 is the vacuum permittivity, f is applied frequency) explains this phenomenon more convincingly, i.e., ε″ is inversely proportional to resistivity ρ.47,48 In our system, the resistivity ρ of the hybrid decreases continuously upon increasing the conductive MXene content, further inducing the increase of ε″ (Figure 4b). Moreover, it should be pointed out that many fluctuation peaks with multiformants, during high-frequency bond (10−18 GHz), are observed on the ε′-f and ε″-f curves for the hybrids with high MXene content, which are mainly attributed to nonlinear dielectric resonances induced by different polarizations. During high-frequency bond (10−18 GHz), the polarization behaviors become less stable due to the relatively slow relaxation compared to the high frequency of electric field, leading to the interference and turbulence of microscopic polarizations, 25403


Research Article


Figure 6. (a) EM RL curves of Ni-2.5% MXene, Ni-5% MXene, Ni-10% MXene, Ni-20% MXene, and Ni-30% MXene hybrids, (b) corresponding impedance matching at a thickness of 2 mm, (c) reflection loss curves of Ni-10% MXene with different thicknesses, and (d) its corresponding three-dimensional (3D) plots.

further resulting in the fluctuation changes shown in ε′-f and ε″-f curves. The μ′ and μ″ values of hybrids (Figures 4 and S6c,d in the Supporting Information) fluctuating within the range of 0.8− 1.4 and −0.8−0.4, respectively, show a slight downward trend with increasing frequency. This is mainly ascribed to the stronger eddy current loss produced by the conductive magnetic material in alternating the EM field at high frequency. Furthermore, multiple resonance peaks appear on the μ′-f and μ″-f curves during 2−18 GHz, which may be caused by exchange resonance, eddy current and natural resonance of conductive and magnetic MXene/Ni hybrid.49,50 The above analysis can conclude that the EM parameter size of the hybrid can be adjusted by changing the content of MXene. More importantly, thanks to the meticulous design of the MXene/Ni hybrid, polarization and resonance can be generated under the action of alternating EM fields, which would result in the dissipation of incident EM wave as much as possible. In general, dielectric loss tangent (tan δε = ε″/ε′) and magnetic loss tangent (tan δμ = μ″/μ′) represent the capacity of consuming electric and magnetic energy, respectively. For conductive and magnetic hybrids, the sum of tan δμ and tan δε (tan δμ + tan δε) is positively correlated with their EM wave loss capability.51 Our result (Figure 5a) reveals importantly that the values of (tan δμ + tan δε) show a continuous increase with the increasing MXene content in the MXene/Ni hybrid, indicating the stronger dielectric and magnetic loss capability of the hybrid with a higher MXene content. Moreover, attenuation constant α determines the attenuation capacity for entered EM wave of the material, which can be expressed as52 α= ×

whole range increase continuously with the increasing MXene content from 2.5 to 50%, exhibiting a similar change trend to (tan δμ + tan δε). Thus, both the results of dielectric/magnetic loss tangent and attenuation constant reveal that the EM wave loss capability can be improved dramatically by increasing the MXene content. Based on the results of permittivity and permeability (Figure 4), the improved EM wave loss capability is mainly ascribed to the increased permittivity induced by the additional interfaces and charge carriers of Ti3C2Tx nanosheets. 3.3. Electromagnetic Absorption Performance of MXene/Ni Hybrids. The EM wave absorption performance of the MXene/Ni hybrids is confirmed by the reflection loss (RL) value according to the transmission line theory, which can be calculated by the correlation of complex permittivity and complex permeability as follows53,54 RL = 20 log10|(Zin − Z0)/(Zin + Z0)|

Zin = Z0

μr

(3)

where Zin is the input characteristic impedance, Z0 is the impedance of free space, d is the thickness of the hybrid composite, εr is the complex permittivity, μr is the complex permeability, c is the speed of light, and f is the frequency. When RL < −10 dB, it means that 90% EM wave is successfully absorbed, and the corresponding frequency band is called the effective frequency band. Figures 6a and S8 (Supporting Information) exhibit the EM wave absorption capability of MXene/Ni hybrids at a thickness of 2 mm. Unexpectedly, it can be seen that the Ni-10% MXene composite exhibits the best EM absorbing performance with an optimal minimum reflection loss of −16.9 dB at 9.8 GHz when compared to other samples (−10.3 dB for Ni-5% MXene; −8.7 dB for Ni-20% MXene). But this result is not consistent with the above-mentioned EM wave loss capability of hybrids. To better understand the EM absorbing performance of MXene/Ni hybrids, their impedance matching, deciding how much of EM waves enter into the hybrids, is

2 πf c (μ″ε″ − μ′ε′) +

ij 2πfd με yz r r z zz tanhjjjj j z c εr k {

(2)

(μ″ε″ − μ′ε′)2 + (μ′ε″ + μ″ε′)2 (1)

where f is the frequency of the EM wave and c is the speed of light. As shown in Figures 5b and S7a (Supporting Information), the attenuation constants α of hybrids at the 25404


Research Article


Figure 7. (a) Shielding performance of MXene/Ni hybrids with different Ti3C2Tx contents ranging from 10 to 50 wt % and (b) the corresponding average value of SEtotal, SEA, and SER of 2−18 GHz, (c) the SEtotal curve of Ni-50% MXene with different thicknesses, and (d) the corresponding average value of SEtotal, SEA, and SER.

expressed by |Zin/Z0|, where Zin represents the impedance of the material interface and Z0 represents the impedance of free space, 48 shown in Figures 6b and S7b (Supporting Information). Very interestingly, the frequencies of the minimum RL value for all MXene/Ni hybrids are just consistent with the impedance matching band closest to 1, which means that the EM waves almost enter into the interior of materials with very few reflected waves.55 Such consistency reveals that the impedance matching between the MXene/Ni hybrid and free space is the first influence factor for the EM absorption performance, which decides the amount of EM wave propagating into hybrids. Then, the propagated EM waves can be dissipated via dielectric loss and magnetic loss caused by conductive and magnetic MXene/Ni hybrids. Therefore, both the impedance matching and dissipation capacity of materials codetermine their final EM wave absorbing properties. In our system, the Ni-10% MXene hybrid with the best impedance matching and appropriate dissipation capacity exhibits the optimal EM absorbing ability. According to eq 2, the thickness of the absorber is considered to be the other key factor affecting its absorbing performance. Figures 6c,d and S9 (Supporting Information) show the reflection loss and the corresponding 3D plots of MXene/Ni hybrid samples under different sample thicknesses. As shown in Figure S10 in the Supporting Information, it is easily found that the RL peaks of all hybrids shift to the lower frequency region with the increase of sample thickness, which can be well explained by the quarter-wavelength (λ/4) cancellation theory. i.e., when the included angle of the incident wave and reflected wave is 1807̅ out of phase, the EM wave is eliminated at the receiving end.56,57 The Ni-10% MXene hybrid sample exhibits the minimum RL values of −49.9 dB at 11.9 GHz with a sample thickness of 1.75 mm and an effective bandwidth (RL ≤ −10 dB) of 2.1 GHz. By adjusting the sample thickness from 1.5 to 5.0 mm, the effective absorbing band could be easily regulated between 3.3 and 18 GHz. To highlight the advantage of the excellent EM absorption properties of our hybrid, some representative

absorbing materials reported in the previous literature are listed in Table S1 in the Supporting Information. Based on the sample thickness, the RL value, filler loading, and other indicators, it can be concluded that our Ni-10% MXene hybrid has the advantages of lightweight, strong absorption capacity, and thin thickness as an EM wave absorber. 3.4. Electromagnetic Shielding Performance of MXene/Ni Hybrids. Benefiting from the unparalleled conductivity, MXene nanosheets have been widely employed to design and prepare high-performance electromagnetic interference (EMI) shielding materials and devices. On the other hand, due to the nature of EM waves, both high permittivity and high permeability are required to design the ideal EMI shielding materials. Therefore, our MXene/Ni hybrids containing both dielectric and magnetic components are expected as highly effective EMI shielding materials. In this work, the EMI shielding effectiveness (SE) of MXene/Ni hybrids can be calculated using S-parameters. The total EMI SE (SEtotal), consisting of reflection efficiency (SER), multiple reflection efficiency (SEMR), and absorption efficiency (SEA), can be described as follows58−60 SEtotal (dB) = SE R + SEA + SEMR ≈ SE R + SEA

(4)

SE R (dB) = −10 log(1 − S112 )

(5)

SEA (dB) = −10 log[S212 /(1 − S112 )]

(6)

Among them, SEMR is often negligible when SEtotal > 15 dB. Figure 7 presents the EMI shielding properties of MXene/Ni hybrids with different Ti3C2Tx MXene contents under different sample thicknesses during 2−18 GHz. Figure S11 in the Supporting Information shows the effect of the amount of different Ti3C2Tx and MXene/Ni hybrid fillers in paraffin on the percolation threshold. It is easily understood that the dramatic increase of the electrical conductivity (from 7.1 × 10−12 to 4.0 S m−1, Figure S11 in the Supporting Information) with the increasing Ti3C2Tx MXene content when above the percolation threshold results in a significant improvement in 25405


Research Article


Figure 8. Schematic illustration of EM wave loss mechanisms of the MXene/Ni hybrid.

more MXene/Ni hybrid participates in the dissipation for EM waves, resulting in the continuous increase of SEA. 3.5. Mechanisms of EM Wave Absorption and Shielding of MXene/Ni Hybrids. The above results reveal that the EM absorption and EMI shielding performances of MXene/Ni hybrids can be easily adjusted by balancing the ratio of conductive Ti3C2Tx nanosheets and magnetic Ni nanochains. It is very interesting that the percolation threshold (10−20 wt %) is just corresponding to the boundary of the MXene/Ni hybrid used as the absorbing material or the shielding material. Below the percolation threshold, the EM wave absorbing performance of hybrid improves with the increase of MXene loading due to the introduction of various polarization effects, where the Ni-10% MXene hybrid exhibits a best absorbing performance. Once beyond the percolation threshold, the absorbing capacity weakens sharply because of the increased impedance matching and weakened polarization effects. Above the percolation threshold, the hybrid shows the effective EMI shielding properties, which present a continuous increasing trend in keeping with conductivity. This result suggests that the electrical conductivity is one of the main influencing factors for improving the EMI shielding performance of the MXene/Ni hybrid. Except for the impedance matching related to the electrical conductivity, the EM wave loss caused by the hybrid plays an important role for both EM absorbing materials and absorption-dominated EMI shielding materials. The possible mechanisms, by which the MXene/Ni hybrids interact with EM waves in the paraffin matrix, are proposed in Figure 8. First, the few-layered Ti3C2Tx nanosheets with a high aspect ratio can form more conductive paths in the hybrid, and then enhance its conductivity loss in an EM field. Moreover, the flexible and corrugated Ti3C2Tx nanosheets can induce the multiple scattering of the EM wave and increase its propagation path in the hybrid, leading to further attenuation of the EM wave.39 Second, 1D magnetic Ni nanochains with antenna-like structures are capable of receiving more EM waves, causing orientation polarization attenuation and forming a dissipated microcurrent to absorb the EM wave energy.61 Under the action of alternating EM waves, the Ni chain can exhibit magnetic loss effects induced by natural resonance, exchange resonance, eddy current, etc. Third, the dipole polarization can be caused by the surface functional groups, localized defects, and dangling bonds of Ti3C2Tx sheets that act as polarization centers under an EM field, meanwhile,

the EMI shielding properties (SEtotal values) during the whole testing frequency range (Figures 7a and S12 in the Supporting Information). The Ni-50% MXene sample with the highest conductivity (4.0 S m−1) shows the best EMI shielding properties with an average SE value of 33.8 dB at only 1.3 mm sample thickness. These results demonstrate that an effective EMI shielding MXene/Ni hybrid with shielding efficiency more than 99.9% can be obtained by only adjusting the MXene content. To understand the EMI shielding mechanism, the average SEtotal, SEA, and SER of MXene/Ni hybrids are calculated based on eqs 4−6, and are shown in Figure 7b. It is found that the hybrids exhibit higher SEA values than SER, which demonstrates an absorption dominant shielding mechanism in the effective EMI shielding MXene/Ni hybrids. Meanwhile, both SER and SEA values increase gradually with the increasing MXene content. On the one hand, the increasing SER values mean that more EM waves are reflected at the surface of the hybrid due to the increasing impedance mismatch caused by conductive MXene. On the other hand, the improving electrical conductivity and more MXene sheets with abundant functional groups mean that more electron transport/transition and polarization occur in the alternative EM field, further resulting in more EM energy loss in hybrids. Accordingly, the EMI SE is dependent on not only the intrinsic electrical conductivity but also on the thickness of samples. The relationship between the sample thickness and their EMI shield properties is shown in Figure 7c. By increasing the sample thickness from 0.7 to 2.8 mm, the EMI SE of the Ni-50% MXene hybrid shows a continuous and prominent improvement with increased average SEtotal values from 20.6 to 57.4 dB (Figure 7d). The maximum EMI SE value of the MXene/Ni hybrid can reach 66.4 dB at 18 GHz, which is higher than the most reported results at the same or higher MXene content (Table S2 in the Supporting Information). The enhancement mechanism of the hybrid with increasing sample thickness is also discussed by estimating the proportion of SER and SEA in SEtotal. As shown in Figure 7d, the SEA values exhibit the same increasing trend with SEtotal as the increase of sample thickness, while the change of SER can be almost negligible. This result suggests that increasing absorption is the main reason for the EMI SE enhancement caused by increased sample thickness. Surely, the unchanged conductivity means the similar impedance mismatch of the hybrid samples with different thicknesses, which leads to the unchanged SER. But the increased sample thickness means that 25406


Research Article


GHz under 2.8 mm sample thickness. This work explored the EM absorption and EMI shielding performances of MXene/Ni hybrids by adjusting only the MXene component. The possible phase diagram of the relationship between conductor/magnet components and EM wave absorption and shielding properties was proposed, which may provide a reference for the development of high-performance EM wave absorbing and shielding materials in the future.

space-charge polarization and interfacial polarization can be also induced by the space-charge accumulation between the interfaces of MXene sheets/Ni chains, MXene sheets/paraffin, and Ni chains/paraffin.62 The above polarizations play an identical role as micro capacitors to contribute the dielectric loss for EM waves. Finally, most of the EM energy can be attenuated and converted into thermal or other forms of energy by the synergistic loss mechanism between dielectric loss of Ti3C2Tx sheets and magnetic loss of Ni nanochains. Strictly, good EM energy attenuation and excellent impedance matching are usually considered to design the EM absorption materials, whereas high electrical conductivity causing high impedance mismatching is required for improving the EMI shielding performance of the material. Meanwhile, the synergistic effect of dielectric properties and magnetic loss is critical to the loss of EM energy. In view of these points, balancing the dielectric properties, permeability, as well as electrical conductivity is the key to design the high-performance EM wave absorption and shielding materials. For this reason, a possible phase diagram of the relationship between the conductor/magnet components ratio and the EM wave absorption and shielding properties is given based on our results and is shown in Figure 9. In short, the MXene/Ni

■

ASSOCIATED CONTENT

S Supporting Information *

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acsami.9b07294.

■

XRD diffraction patterns, XPS, FTIR, UV−vis spectra, and SEM, AFM, TEM images of Ti3C2Tx sheets and MXene/Ni hybrid; supplementary permittivity, permeability, electrical conductivity, EM wave absorbing, and EMI shielding performance of hybrid composite; comprehensive comparison with previous literature (PDF)

AUTHOR INFORMATION

Corresponding Authors

*E-mail: [email protected] (Y.F.). *E-mail: [email protected] (Y.W.). ORCID

Biao Zhao: 0000-0003-3538-2195 Yuezhan Feng: 0000-0002-5874-6062 Yaming Wang: 0000-0001-9621-0261 Chuntai Liu: 0000-0001-9751-6270 Author Contributions

This manuscript was written through contributions of all authors. All authors have given approval to the final version of the manuscript.

Figure 9. Relationship between impedance match and conductivity of the design guidance of the EM absorbing and shielding materials.

Notes

The authors declare no competing financial interest.

■

hybrid with a moderate Ti2C3Tx content showing a high dielectric loss, magnetic loss, and excellent impedance matching, can be used as an EM wave absorber, further increasing the MXene content, improving the electrical conductivity above the percolation threshold, would make the composite a great EMI shielding material.

ACKNOWLEDGMENTS The authors gratefully acknowledge the financial support for this work by the National Science Foundation of China (Grant nos. 51573170 and U1704162), the China Postdoctoral Science Foundation (Grant no. 2018M642781), and the analytical and testing assistance from the Modern Analysis and Computing Center of Zhengzhou University and Shiyanjia Lab (www.shiyanjia.com).

4. CONCLUSIONS In summary, the MXene/Ni hybrids were prepared by simply mixing Ni chains and Ti3C2Tx nanosheets using a hydrothermal process. Excellent EM wave absorption and EMI shielding performances were obtained in MXene/Ni hybrids by only adjusting the Ti3C2Tx content, which was believed to come from the synergistic effects of dielectric loss of MXene and magnetic loss of Ni chain. With a suitable impedance matching, dielectric loss, and magnetic loss, the minimum RL value of −49.9 dB for the Ni-10% MXene sample was obtained at 11.9 GHz with a sample thickness of 1.75 mm. By adjusting between 1.5 and 5.0 mm, the effective absorbing band could be easily regulated between 3.3 and 18 GHz. Moreover, the desired shielding performance can be obtained via augmenting the content of Ti3C2Tx nanosheets to 50 wt % due to the increase of the electrical conductivity, which also shows a striking dependence on the sample thickness. The maximum EMI SE value of the MXene/Ni hybrid can reach 66.4 dB at 18

■

REFERENCES

(1) Cao, M.; Cai, Y.; He, P.; Shu, J.; Cao, W.; Yuan, J. 2D MXenes: Electromagnetic Property for Microwave Absorption and Electromagnetic Interference Shielding. Chem. Eng. J. 2019, 359, 1265−1302. (2) Qin, F.; Brosseau, C. A Review and Analysis of Microwave Absorption in Polymer Composites Filled with Carbonaceous Particles. J. Appl. Phys. 2012, 111, 061301−061324. (3) Zhao, G.; Lv, H.; Zhou, Y.; Zheng, X.; Wu, C.; Xu, C. SelfAssembled Sandwich-like MXene-Derived Nanocomposites for Enhanced Electromagnetic Wave Absorption. ACS Appl. Mater. Interfaces 2018, 10, 42925−42932. (4) Zhao, B.; Zhao, W.; Shao, G.; Fan, B.; Zhang, R. MorphologyControl Synthesis of a Core−Shell Structured NiCu Alloy with Tunable Electromagnetic-Wave Absorption Capabilities. ACS Appl. Mater. Interfaces 2015, 7, 12951−12960. 25407


Research Article

ACS Applied Materials & Interfaces (5) Shahzad, F.; Alhabeb, M.; Hatter, C. B.; Anasori, B.; Man Hong, S.; Koo, C. M.; Gogotsi, Y. Electromagnetic Interference Shielding with 2D Transition Metal Carbides (MXenes). Science 2016, 353, 1137−1140. (6) Lv, H.; Yang, Z.; Wang, P. L.; Ji, G.; Song, J.; Zheng, L.; Zeng, H.; Xu, Z. J. A Voltage-Boosting Strategy Enabling a Low-Frequency, Flexible Electromagnetic Wave Absorption Device. Adv. Mater. 2018, 30, No. 1706343. (7) Song, C.; Yin, X.; Han, M.; Li, X.; Hou, Z.; Zhang, L.; Cheng, L. Three-dimensional Reduced Graphene Oxide Foam Modified with ZnO Nanowires for Enhanced Microwave Absorption Properties. Carbon 2017, 116, 50−58. (8) Biswas, S.; Arief, I.; Panja, S. S.; Bose, S. Absorption-Dominated Electromagnetic Wave Suppressor Derived from Ferrite-Doped Cross-Linked Graphene Framework and Conducting Carbon. ACS Appl. Mater. Interfaces 2017, 9, 3030−3039. (9) Wang, X.; Ma, T.; Shu, J.; Cao, M. Confinedly Tailoring Fe3O4 Clusters-NG to Tune Electromagnetic Parameters and Microwave Absorption with Broadened Bandwidth. Chem. Eng. J. 2018, 332, 321−330. (10) Wang, C.; Murugadoss, V.; Kong, J.; He, Z.; Mai, X.; Shao, Q.; Chen, Y.; Guo, L.; Liu, C.; Angaiah, S.; Guo, Z. Overview of Carbon Nanostructures and Nanocomposites for Electromagnetic Wave Shielding. Carbon 2018, 140, 696−733. (11) Liu, Y.; Fu, Y.; Liu, L.; Li, W.; Guan, J.; Tong, G. Low-Cost Carbothermal Reduction Preparation of Monodisperse Fe3O4/C Core-Shell Nanosheets for Improved Microwave Absorption. ACS Appl. Mater. Interfaces 2018, 10, 16511−16520. (12) Zong, M.; Huang, Y.; Zhao, Y.; Sun, X.; Qu, C.; Luo, D.; Zheng, J. Facile Preparation, High Microwave Absorption and Microwave Absorbing Mechanism of RGO-Fe3O4 Composites. RSC Adv. 2013, 3, 23638−23648. (13) Zhang, X.; Ji, G.; Liu, W.; Zhang, X.; Gao, Q.; Li, Y.; Du, Y. A Novel Co/TiO2 Nanocomposite Derived from a Metal-organic Framework: Synthesis and Efficient Microwave Absorption. J. Mater. Chem. C 2016, 4, 1860−1870. (14) Zhao, B.; Guo, X.; Zhao, W.; Deng, J.; Shao, G.; Fan, B.; Bai, Z.; Zhang, R. Yolk−Shell Ni@SnO2 Composites with a Designable Interspace To Improve the Electromagnetic Wave Absorption Properties. ACS Appl. Mater. Interfaces 2016, 8, 28917−28925. (15) Zhao, B.; Guo, X.; Zhao, W.; Deng, J.; Fan, B.; Shao, G.; Bai, Z.; Zhang, R. Facile Synthesis of Yolk−shell Ni@void@SnO2(Ni3Sn2) Ternary Composites via Galvanic Replacement/Kirkendall Effect and Their Enhanced Microwave Absorption Properties. Nano Res. 2017, 10, 331−343. (16) Wen, F.; Zhang, F.; Liu, Z. Investigation on Microwave Absorption Properties for Multiwalled Carbon Nanotubes/Fe/Co/Ni Nanopowders as Lightweight Absorbers. J. Phys. Chem. C 2011, 115, 14025−14030. (17) Cao, M.; Han, C.; Wang, X.; Zhang, M.; Zhang, Y.; Shu, J.; Yang, H.; Fang, X.; Yuan, J. Graphene Nanohybrids: Excellent Electromagnetic Properties for the Absorbing and Shielding of Electromagnetic Waves. J. Mater. Chem. C 2018, 6, 4586−4602. (18) Lukatskaya, M.; Mashtalir, O.; Ren, C.; Dall’Agnese, Y.; Rozier, P.; Taberna, P.; Naguib, M.; Simon, P.; Barsoum, M.; Gogotsi, Y. Cation Intercalation and High Volumetric Capacitance of TwoDimensional Titanium Carbide. Science 2013, 341, 1502−1505. (19) Zhao, M.; Ren, C.; Ling, Z.; Lukatskaya, M.; Zhang, C.; Van Aken, K.; Barsoum, M.; Gogotsi, Y. Flexible MXene/Carbon Nanotube Composite Paper with High Volumetric Capacitance. Adv. Mater. 2015, 27, 339−345. (20) Han, M.; Yin, X.; Wu, H.; Hou, Z.; Song, C.; Li, X.; Zhang, L.; Cheng, L. Ti3C2 MXenes with Modified Surface for High-Performance Electromagnetic Absorption and Shielding in the X-Band. ACS Appl. Mater. Interfaces 2016, 8, 21011−21019. (21) Qing, Y.; Zhou, W.; Luo, F.; Zhu, D. Titanium Carbide (MXene) Nanosheets as Promising Microwave Absorbers. Ceram. Int. 2016, 42, 16412−16416.

(22) Qian, Y.; Wei, H.; Dong, J.; Du, Y.; Fang, X.; Zheng, W.; Sun, Y.; Jiang, Z. Fabrication of Urchin-like ZnO-MXene Nanocomposites for High-performance Electromagnetic Absorption. Ceram. Int. 2017, 43, 10757−10762. (23) Dai, B.; Zhao, B.; Xie, X.; Su, T.; Fan, B.; Zhang, R.; Yang, R. Novel Two-dimensional Ti3C2Tx MXenes/nano-carbon Sphere Hybrids for High-performance Microwave Absorption. J. Mater. Chem. C 2018, 6, 5690−5697. (24) Liu, P.; Ng, V. M. H.; Yao, Z.; Zhou, J.; Kong, L. B. Ultrasmall Fe3O4 Nanoparticles on MXenes with High Microwave Absorption Performance. Mater. Lett. 2018, 229, 286−289. (25) Zhu, H.; Bai, Y.; Liu, R.; Lun, N.; Qi, Y.; Han, F.; Bi, J. In Situ Synthesis of One-dimensional MWCNT/SiC Porous Nanocomposites with Excellent Microwave Absorption Properties. J. Mater. Chem. 2011, 21, 13581−13587. (26) Yang, J.; Zhang, J.; Liang, C.; Wang, M.; Zhao, P.; Liu, M.; Liu, J.; Che, R. Ultrathin BaTiO3 Nanowires with High Aspect Ratio: A Simple One-Step Hydrothermal Synthesis and Their Strong Microwave Absorption. ACS Appl. Mater. Interfaces 2013, 5, 7146−7151. (27) Liang, L.; Guo, X.; Bai, Z.; Zhao, B.; Zhang, R. Synthesis of Core-shell Fishbone-like Cu@Ni Composites and Their Electromagnetic Wave Absorption Properties. Powder Technol. 2017, 319, 245−252. (28) Sankaran, S.; Deshmukh, K.; Ahamed, M.; Khadheer Pasha, S. Recent Advances in Electromagnetic Interference Shielding Properties of Metal and Carbon Filler Reinforced Flexible Polymer Composites: A Review. Composites, Part A 2018, 114, 49−71. (29) Sun, R.; Zhang, H.; Liu, J.; Xie, X.; Yang, R.; Li, Y.; Hong, S.; Yu, Z. Highly Conductive Transition Metal Carbide/Carbonitride(MXene)@polystyrene Nanocomposites Fabricated by Electrostatic Assembly for Highly Efficient Electromagnetic Interference Shielding. Adv. Funct. Mater. 2017, 27, No. 1702807. (30) Liu, R.; Miao, M.; Li, Y.; Zhang, J.; Cao, S.; Feng, X. Ultrathin Biomimetic Polymeric Ti3C2Tx MXene Composite Films for Electromagnetic Interference Shielding. ACS Appl. Mater. Interfaces 2018, 10, 44787−44795. (31) Xu, H.; Yin, X.; Li, X.; Li, M.; Liang, S.; Zhang, L.; Cheng, L. Lightweight Ti2CTx MXene/Poly(vinyl alcohol) Composite Foams for Electromagnetic Wave Shielding with Absorption-Dominated Feature. ACS Appl. Mater. Interfaces 2019, 11, 10198−10207. (32) Naguib, M.; Kurtoglu, M.; Presser, V.; Lu, J.; Niu, J.; Heon, M.; Hultman, L.; Gogotsi, Y.; Barsoum, M. Two-Dimensional Nanocrystals Produced by Exfoliation of Ti3AlC2. Adv. Mater. 2011, 23, 4248− 4253. (33) Li, Y.; Zhou, X.; Wang, J.; Deng, Q.; Li, M.; Du, S.; Han, Y.; Lee, J.; Huang, Q. Facile Preparation of In Situ Coated Ti3C2Tx/ Ni0.5Zn0.5Fe2O4 Composites and Their Electromagnetic Performance. RSC Adv. 2017, 7, 24698−24708. (34) Wang, X.; Shen, X.; Gao, Y.; Wang, Z.; Yu, R.; Chen, L. Atomic-Scale Recognition of Surface Structure and Intercalation Mechanism of Ti3C2X. J. Am. Chem. Soc. 2015, 137, 2715−2721. (35) Lipatov, A.; Alhabeb, M.; Lukatskaya, M.; Boson, A.; Gogotsi, Y.; Sinitskii, A. Effect of Synthesis on Quality, Electronic Properties and Environmental Stability of Individual Monolayer Ti3C2 MXene Flakes. Adv. Electron. Mater. 2016, 2, No. 1600255. (36) Feng, Y.; Wang, B.; Li, X.; Ye, Y.; Ma, J.; Liu, C.; Zhou, X.; Xie, X. Enhancing Thermal Oxidation and Fire Resistance for Reduced Graphene Oxide by Phosphorus and Nitrogen Co-doping: Mechanism and Kinetic Analysis. Carbon 2019, 146, 650−659. (37) Peng, J.; Chen, X.; Ong, W.; Zhao, X.; Li, N. Surface and Heterointerface Engineering of 2D MXenes and Their Nanocomposites: Insights into Electro- and Photocatalysis. Chem 2019, 5, 18−50. (38) Feng, Y.; Li, X.; Zhao, X.; Ye, Y.; Zhou, X.; Liu, H.; Liu, C.; Xie, X. Synergetic Improvement in Thermal Conductivity and Flame Retardancy of Epoxy/Silver Nanowires Composites by Incorporating “Branch-Like” Flame-Retardant Functionalized Graphene. ACS Appl. Mater. Interfaces 2018, 10, 21628−21641. 25408


Research Article

ACS Applied Materials & Interfaces (39) Wen, B.; Wang, X.; Cao, W.; Shi, H.; Lu, M.; Wang, G.; Jin, H.; Wang, W.; Yuan, J.; Cao, M. Reduced Graphene Oxides: The Thinnest and Most Lightweight Materials with Highly Efficient Microwave Attenuation Performances of the Carbon World. Nanoscale 2014, 6, 5754−5761. (40) Wu, H.; Zhang, R.; Liu, X.; Lin, D.; Pan, W. Electrospinning of Fe, Co, and Ni Nanofibers: Synthesis, Assembly, and Magnetic Properties. Chem. Mater. 2007, 19, 3506−3511. (41) Wang, N.; Cao, X.; Kong, D.; Chen, W.; Guo, L.; Chen, C. Nickel Chains Assembled by Hollow Microspheres and Their Magnetic Properties. J. Phys. Chem. C 2008, 112, 6613−6619. (42) Zhao, B.; Park, C. B. Tunable Electromagnetic Shielding Properties of Conductive Poly(vinylidene fluoride)/Ni Chain Composite Films with Negative Permittivity. J. Mater. Chem. C 2017, 5, 6954−6961. (43) Yao, X.; Kou, X.; Qiu, J.; Moloney, M. The Generation Mechanism of Negative Permittivity in Multi-walled Carbon Nanotubes/Polyaniline Composites. RSC Adv. 2016, 6, 35378−35386. (44) Zhao, B.; Liu, J.; Guo, X.; Zhao, W.; Liang, L.; Ma, C.; Zhang, R. Hierarchical Porous Ni@boehmite/Nickel Aluminum Oxide Flakes with Enhanced Microwave Absorption Ability. Phys. Chem. Chem. Phys. 2017, 19, 9128−9136. (45) Shi, X.; Cao, M.; Yuan, J.; Fang, X. Dual Nonlinear Dielectric Resonance and Nesting Microwave Absorption Peaks of Hollow Cobalt Nano-chains Composites with Negative Permeability. Appl. Phys. Lett. 2009, 95, 163108−163110. (46) Cao, W.; Wang, X.; Yuan, J.; Wang, W.; Cao, M. Temperature Dependent Microwave Absorption of Ultrathin Graphene Composites. J. Mater. Chem. C 2015, 3, 10017−10022. (47) Liu, X.; Geng, D.; Meng, H.; Shang, P.; Zhang, Z. Microwaveabsorption Properties of ZnO-coated Iron Nanocapsules. Appl. Phys. Lett. 2008, 92, 173117−173119. (48) Zhao, B.; Zhang, X.; Deng, J.; Bai, Z.; Liang, L.; Li, Y.; Zhang, R. A novel Sponge-like 2D Ni/Derivative Heterostructure to Strengthen Microwave Absorption Performance. Phys. Chem. Chem. Phys. 2018, 20, 28623−28633. (49) Liu, T.; Xie, X.; Pang, Y.; Kobayashi, S. Co/C Nanoparticles with Low Graphitization Degree: A High Performance Microwaveabsorbing Material. J. Mater. Chem. C 2016, 4, 1727−1735. (50) Li, N.; Huang, G.; Li, Y.; Xiao, H.; Feng, Q.; Hu, N.; Fu, S. Enhanced Microwave Absorption Performance of Coated Carbon Nanotubes by Optimizing the Fe3O4 Nanocoating Structure. ACS Appl. Mater. Interfaces 2017, 9, 2973−2983. (51) Luo, C.; Duan, W.; Yin, X.; Kong, J. Microwave-Absorbing Polymer-Derived Ceramics from Cobalt-Coordinated Poly(dimethylsilylene)diacetylenes. J. Phys. Chem. C 2016, 120, 18721− 18732. (52) Xu, W.; Wang, G.; Yin, P. Designed Fabrication of Reduced Graphene Oxides/Ni Hybrids for Effective Electromagnetic Absorption and Shielding. Carbon 2018, 139, 759−767. (53) Wang, Z.; Wei, R.; Gu, J.; Liu, H.; Liu, C.; Luo, C.; Kong, J.; Shao, Q.; Wang, N.; Guo, Z.; Liu, X. Ultralight, Highly Compressible and Fire-retardant Graphene Aerogel with Self-adjustable Electromagnetic Wave absorption. Carbon 2018, 139, 1126−1135. (54) Guo, J.; Song, H.; Liu, H.; Luo, C.; Ren, Y.; Ding, T.; Khan, M. A.; Young, D. P.; Liu, X.; Zhang, X.; Kong, J.; Guo, Z. Polypyrroleinterface-functionalized Nano-magnetite Epoxy Nanocomposites as Electromagnetic Wave Absorbers with Enhanced Flame Retardancy. J. Mater. Chem. C 2017, 5, 5334−5344. (55) Wu, H.; Wu, G.; Ren, Y.; Yang, L.; Wang, L.; Li, X. Co2+/Co3+ Ratio Dependence of Electromagnetic Wave Absorption in Hierarchical NiCo2O4−CoNiO2 Hybrids. J. Mater. Chem. C 2015, 3, 7677−7690. (56) Yan, L.; Wang, X.; Zhao, S.; Li, Y.; Gao, Z.; Zhang, B.; Cao, M.; Qin, Y. Highly Efficient Microwave Absorption of Magnetic Nanospindle−Conductive Polymer Hybrids by Molecular Layer Deposition. ACS Appl. Mater. Interfaces 2017, 9, 11116−11125.

(57) Jia, Z.; Lan, D.; Lin, K.; Qin, M.; Kou, K.; Wu, G.; Wu, H. Progress in Low-frequency Microwave Absorbing Materials. J. Mater. Sci.: Mater. Electron. 2018, 29, 17122−17136. (58) Chen, Y.; Zhang, H.; Yang, Y.; Wang, M.; Cao, A.; Yu, Z. HighPerformance Epoxy Nanocomposites Reinforced with Three-Dimensional Carbon Nanotube Sponge for Electromagnetic Interference Shielding. Adv. Funct. Mater. 2016, 26, 447−455. (59) Kumaran, R.; Kumar, S.; Balasubramanian, N.; Alagar, M.; Subramanian, V.; Dinakaran, K. Enhanced Electromagnetic Interference Shielding in a Au-MWCNT Composite Nanostructure Dispersed PVDF Thin Films. J. Phys. Chem. C 2016, 120, 13771− 13778. (60) Zeng, Z.; Jin, H.; Chen, M.; Li, W.; Zhou, L.; Zhang, Z. Lightweight and Anisotropic Porous MWCNT/WPU Composites for Ultrahigh Performance Electromagnetic Interference Shielding. Adv. Funct. Mater. 2016, 26, 303−310. (61) Zhao, B.; Deng, J.; Liang, L.; Zuo, C.; Bai, Z.; Guo, X.; Zhang, R. Lightweight Porous Co3O4 and Co/CoO Nanofibers with Tunable Impedance Match and Configuration-dependent Microwave Absorption Properties. CrystEngComm 2017, 19, 6095−6106. (62) Luo, C.; Jiao, T.; Gu, J.; Tang, Y.; Kong, J. Graphene Shield by SiBCN Ceramic: A Promising High-Temperature Electromagnetic Wave-Absorbing Material with Oxidation Resistance. ACS Appl. Mater. Interfaces 2018, 10, 39307−39318.

25409


Ni Chain Hybrid with Excellent

Recommend Documents