Publications by authors named "Guangbin Ji"

69 Publications

Flexible and transparent silver nanowires/biopolymer film for high-efficient electromagnetic interference shielding.

J Colloid Interface Sci 2021 Sep 1;607(Pt 1):89-99. Epub 2021 Sep 1.

College of Materials Science and Technology, Nanjing University of Aeronautics and Astronautics, Nanjing 210016, PR China. Electronic address:

Flexible and transparent conductive films are highly desirable in some optoelectronic devices, such as smart windows, touch panels, as well as displays and electromagnetic protection field. Silver nanowire (Ag NW) has been considered as the best material to replace indium tin oxide (ITO) to fabricate flexible transparent electromagnetic interference (EMI) shielding films due to its superior comprehensive performance. However, the common substrates supporting Ag NWs require surface modification to enhance the adhesion with Ag NWs. In this work, a flexible and transparent Ag NWs EMI shielding film with sandwich structure through a facile rod-coating method, wherein Ag NWs network were embedded between biodegradable gelatin-based substrate and cover layer. The interfacial adhesion between Ag NWs and gelatin-based layers was enhanced by hydrogen-bonding interaction and swelling effect without any pretreatment. The shielding effectiveness (SE) of the G/Ag NW/G (G represents gelatin-based layer) film reaches 37.74 dB at X band with an optical transmittance of 72.0 %. What's more, the flexible gelatin-based layer and encapsulated structure endow the resultant G/Ag NW/G film integrating excellent mechanical properties, reliable durability, antioxidation, as well as anti-freezing performance. This work paves a new way for fabricating flexible transparent EMI shielding films.
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http://dx.doi.org/10.1016/j.jcis.2021.08.190DOI Listing
September 2021

A breathable and flexible fiber cloth based on cellulose/polyaniline cellular membrane for microwave shielding and absorbing applications.

J Colloid Interface Sci 2021 Jul 22;605:193-203. Epub 2021 Jul 22.

College of Materials Science and Technology, Nanjing University of Aeronautics and Astronautics, Nanjing 211100, PR China. Electronic address:

High-performance electromagnetic (EM) wave absorption and shielding materials integrating with flexibility, air permeability, and anti-fatigue characteristics are of great potential in portable and wearable electronics. These materials usually prepared by depositing metal or alloy coatings on fabrics. However, the shortcomings of heavy weight and easy corrosion hamper its application. In this work, the cellulose nanofiber (CF) fabric was prepared by electrospinning technology. Then, conductive polyaniline (PANI) was deposited on the CF surface via a facile in-situ polymerization process. The interweaving cellulose/polyaniline nanofiber (CPF) composite constructs a conductive network, and the electrical conductivity can be adjusted by polymerization time. Benefiting from optimal impedance matching, strong conductive loss, as well as interfacial polarization, the CPF possesses excellent EM absorption performance. The minimum reflection loss (RL) value is -49.24 dB, and the effective absorption bandwidth (RL < -10 dB, f) reaches 6.90 GHz. Furthermore, the CPF also exhibits outstanding electromagnetic interference (EMI) shielding capability with shielding efficiency (SE) of 34.93 dB in the whole X band. Most importantly, the lightweight CPF fabrics have the merits of mechanical flexibility, breathability and wash resistance, which is highly applicable for wearable devices.
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http://dx.doi.org/10.1016/j.jcis.2021.07.085DOI Listing
July 2021

Enhanced Microwave Absorbing Ability of Carbon Fibers with Embedded FeCo/CoFeO Nanoparticles.

ACS Appl Mater Interfaces 2021 Aug 22;13(30):36182-36189. Epub 2021 Jul 22.

College of Materials Science and Technology, Nanjing University of Aeronautics and Astronautics, Nanjing 210016, P. R. China.

In the face of increasingly severe electromagnetic (EM) wave pollution, the research of EM wave absorbing materials is an effective solution. To reduce the density of traditional absorbing materials, in this work, FeCo/CoFeO/carbon nanofiber composites were successfully prepared by electrospinning for the EM wave attenuation application. Benefiting from the loss ability of interface polarization, dipole polarization, and magnetic loss, the composites obtained a bandwidth of 5.0 GHz at a 1.95 mm thickness and an absorption peak of -52.3 dB. More importantly, the radar cross section (RCS) reduction of composite coatings calculated by ANSYS Electronics Desktop 2018 (HFSS) can reach 34.5 dBm, and the RCS value is almost less than -10 dBm when the incident angle is greater than 20°, demonstrating great scattering ability of the material coating to EM waves. This work, combined with the exploration of the mechanism and the simulation analysis of the absorbing coating, will be of significance for the development of absorbing materials.
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http://dx.doi.org/10.1021/acsami.1c09430DOI Listing
August 2021

Environmentally Friendly and Multifunctional Shaddock Peel-Based Carbon Aerogel for Thermal-Insulation and Microwave Absorption.

Nanomicro Lett 2021 Apr 5;13(1):102. Epub 2021 Apr 5.

College of Materials Science and Technology, Nanjing University of Aeronautics and Astronautics, Nanjing, 210016, People's Republic of China.

Highlights: The eco-friendly shaddock peel-derived carbon aerogels were prepared by a freeze-drying method. Multiple functions such as thermal insulation, compression resistance and microwave absorption can be integrated into one material-carbon aerogel. Novel computer simulation technology strategy was selected to simulate significant radar cross-sectional reduction values under real far field condition. . Eco-friendly electromagnetic wave absorbing materials with excellent thermal infrared stealth property, heat-insulating ability and compression resistance are highly attractive in practical applications. Meeting the aforesaid requirements simultaneously is a formidable challenge. Herein, ultra-light carbon aerogels were fabricated via fresh shaddock peel by facile freeze-drying method and calcination process, forming porous network architecture. With the heating platform temperature of 70 °C, the upper surface temperatures of the as-prepared carbon aerogel present a slow upward trend. The color of the sample surface in thermal infrared images is similar to that of the surroundings. With the maximum compressive stress of 2.435 kPa, the carbon aerogels can provide favorable endurance. The shaddock peel-based carbon aerogels possess the minimum reflection loss value (RL) of - 29.50 dB in X band. Meanwhile, the effective absorption bandwidth covers 5.80 GHz at a relatively thin thickness of only 1.7 mm. With the detection theta of 0°, the maximum radar cross-sectional (RCS) reduction values of 16.28 dB m can be achieved. Theoretical simulations of RCS have aroused extensive interest owing to their ingenious design and time-saving feature. This work paves the way for preparing multi-functional microwave absorbers derived from biomass raw materials under the guidance of RCS simulations.
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http://dx.doi.org/10.1007/s40820-021-00635-1DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8021664PMC
April 2021

A Flexible and Lightweight Biomass-Reinforced Microwave Absorber.

Nanomicro Lett 2020 Jun 11;12(1):125. Epub 2020 Jun 11.

College of Materials Science and Technology, Nanjing University of Aeronautics and Astronautics, Nanjing, 210016, People's Republic of China.

Developing a flexible, lightweight and effective electromagnetic (EM) absorber remains challenging despite being on increasing demand as more wearable devices and portable electronics are commercialized. Herein, we report a flexible and lightweight hybrid paper by a facile vacuum-filtration-induced self-assembly process, in which cotton-derived carbon fibers serve as flexible skeletons, compactly surrounded by other microwave-attenuating components (reduced graphene oxide and [email protected] nanowires). Owing to its unique architecture and synergy of the three components, the as-prepared hybrid paper exhibits flexible and lightweight features as well as superb microwave absorption performance. Maximum absorption intensity with reflection loss as low as - 63 dB can be achieved, and its broadest frequency absorption bandwidth of 5.8 GHz almost covers the entire Ku band. Such a hybrid paper is promising to cope with ever-increasing EM interference. The work also paves the way to develop low-cost and flexible EM wave absorber from biomass through a facile method.
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http://dx.doi.org/10.1007/s40820-020-00461-xDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7770825PMC
June 2020

Polyimide-Based Foams: Fabrication and Multifunctional Applications.

ACS Appl Mater Interfaces 2020 Oct 16;12(43):48246-48258. Epub 2020 Oct 16.

College of Materials Science and Technology, Nanjing University of Aeronautics and Astronautics, Nanjing 210016, P. R. China.

Because of their unique three-dimensional cellular structure and intrinsic properties, polyimide foam materials have bright prospects for development in multiple functional equipment, which arouses extensive concern. In this Spotlight on Applications, several typical fabrication methods of polyimide foams and the related synthesis mechanism have been systematically described. The advantages and disadvantages of the preparation methods have been compared with each other. Representative functions and the corresponding mechanism models have been concluded, which involve thermal, mechanical, sensing, electromagnetic, environmental, and electrical fields. In the end, the severe tasks and challenges of polyimide foam materials have been summarized, and their promising future development is worth expecting.
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http://dx.doi.org/10.1021/acsami.0c15771DOI Listing
October 2020

Dynamic emulsion droplets enabled by interfacial assembly of azobenzene-functionalized nanoparticles under light and magnetic field.

J Colloid Interface Sci 2021 Feb 23;583:586-593. Epub 2020 Sep 23.

Key Laboratory of Colloid and Interface Chemistry, Ministry of Education, School of Chemistry and Chemical Engineering, Shandong University, Jinan 250100, PR China. Electronic address:

Hypothesis: The ability to control the assembly of micro/nanosized particles at liquid-liquid interface with external inputs promises new opportunities in nanofabrication and biomedicines. This work aims to demonstrate a way to control of dynamic assembly of nanoparticles at liquid-liquid interface by light and magnetic field, which consequently enables the formation of dynamic emulsion droplets.

Experiments: Magnetic FeO nanoparticles functionalized with azobenzene moieties ([email protected]) were synthesized and were dispersed in toluene/(N,N-dimethylformamide, DMF) binary solvent. After irradiation with UV or visible light, the assembly behavior of these FeO nanoparticles were evaluated by electron microscopy and fluorescent microscopy.

Findings: Under UV light, [email protected] nanoparticles were self-assembled due to the increase of dipolar interaction from the photoisomerization of azobenzene and polar molecules, DMF, were harvested from a binary solvent of DMF/toluene. While under visible light, a relief of dipolar interactions between [email protected] nanoparticles can induce the secondary assembly of these [email protected] nanoparticles at DMF-toluene interface, resulting in DMF droplets covered by a layer of nanoparticle superlattices. More importantly, coupled with a magnetic field, these emulsion droplets can be shaped into one dimensional ones during the interfacial assembly process, thereby giving rise to dynamic emulsions controlled by light and magnetic field.
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http://dx.doi.org/10.1016/j.jcis.2020.09.058DOI Listing
February 2021

Multifunctional Bulk Hybrid Foam for Infrared Stealth, Thermal Insulation, and Microwave Absorption.

ACS Appl Mater Interfaces 2020 Jun 12;12(25):28727-28737. Epub 2020 Jun 12.

College of Materials Science and Technology, Nanjing University of Aeronautics and Astronautics, Nanjing 210016, P. R. China.

Taking serious microwave pollution issues and the complex application environment into consideration, it is quite urgent to integrate several functions into one material. Electromagnetic (EM) absorbing materials with multiple functions are highly attractive to next-generation wireless techniques and portable electronic devices. Herein, melamine foam provides a decent platform for the uniform growth of Co-based metal-organic frameworks (MOFs), which bring the as-obtained hybrid foam with three-dimensional porous network structure and combination of dielectric along with magnetic attenuation abilities as advanced materials in multifunctional fields. Remarkably, the relevant microwave absorption (MA) performance of the hybrid foam can reach an extremely high reflection loss value of -59.82 dB. Furthermore, the hybrid foam exhibits excellent infrared stealth and optimiztic heat insulation function, demonstrating the potential in plenty of practical applications. These results may arouse interests and inspirations of the elaborately design and facilely synthesis of high-performance foamlike microwave absorbers with multiple functions.
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http://dx.doi.org/10.1021/acsami.0c09202DOI Listing
June 2020

Environment-Stable CoNi Encapsulation in Stacked Porous Carbon Nanosheets for Enhanced Microwave Absorption.

Nanomicro Lett 2020 Apr 28;12(1):102. Epub 2020 Apr 28.

College of Materials Science and Technology, Nanjing University of Aeronautics and Astronautics, Nanjing, 211100, People's Republic of China.

Magnetic/[email protected] carbon composites, derived from metal-organic frameworks (MOFs) with adjustable composition ratio, have attracted wide attention due to their unique magnetoelectric properties. In addition, MOFs-derived porous carbon-based materials can meet the needs of lightweight feature. This paper reports a simple process for synthesizing stacked [email protected] nanosheets derived from CoNi-MOFs nanosheets with multiple interfaces, which is good to the microwave response. The [email protected] with controllable composition can be obtained by adjusting the ratio of Co and Ni. It is supposed that the increased Co content is benefit to the dielectric and magnetic loss. Additionally, the bandwidth of [email protected] nanosheets can take up almost the whole Ku band. Moreover, this composite has better environmental stability in air, which characteristic provides a sustainable potential for the practical application.
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http://dx.doi.org/10.1007/s40820-020-00432-2DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7770751PMC
April 2020

Self-Assembly Three-Dimensional Porous Carbon Networks for Efficient Dielectric Attenuation.

ACS Appl Mater Interfaces 2019 Aug 8;11(33):30228-30233. Epub 2019 Aug 8.

Division of Physics and Applied Physics, School of Physical and Mathematical Sciences , Nanyang Technological University , 637371 , Singapore.

Zeolitic imidazolate framework (ZIF-8)-derived ZnO/nanoporous carbon (NPC) aligned in a three-dimensional porous carbon network (3DPCN) is designed to form a multiporous network nanostructure to absorb electromagnetic waves. The porous 3DPCN structure acts as the electronic pathway and the nucleation locus for ZIF-8 particles. Meanwhile, the conductive networks could also provide more routes for electron transfer. With good impedance matching and attenuation characteristics, [email protected]/3DPCN shows enhanced microwave response where the minimum reflection loss of -35.7 dB can be achieved with a 10 wt % filler. Our study not only exploits the new system of lightweight absorbers but also further reveals the changing of electromagnetic parameters and absorbing properties by heat treatment, which may lead to a new way to design novel lighter multiporous network nanostructures.
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http://dx.doi.org/10.1021/acsami.9b08365DOI Listing
August 2019

Mesoporous carbon hollow spheres as a light weight microwave absorbing material showing modulating dielectric loss.

Dalton Trans 2019 Jul 11;48(27):10145-10150. Epub 2019 Jun 11.

College of Materials Science and Technology, Nanjing University of Aeronautics and Astronautics, Nanjing 210016, P. R. China.

Mesoporous carbon hollow spheres (MCHS), a kind of light weight material, were fabricated by a simple one-pot process. It is confirmed that the addition of tetrapropoxysilane (TPOS) has a distinct influence on their surface area, pore volume, porous structure and microwave absorption properties. The modulation of electromagnetic parameters within the range of 2-18 GHz can be accomplished by adjusting the pore volume of MCHS, resulting in the largest bandwidth of 6.2 GHz and a maximum reflection loss of -38.5 dB at a thickness of 2-3 mm. The enhanced microwave absorption properties are attributed to the outstanding impedance matching and strong dielectric loss. This study provides novel insights into electromagnetic wave absorption by tuning the pore volume structure.
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http://dx.doi.org/10.1039/c9dt01876jDOI Listing
July 2019

Biomass-Derived Porous Carbon-Based Nanostructures for Microwave Absorption.

Nanomicro Lett 2019 Mar 15;11(1):24. Epub 2019 Mar 15.

School of Materials Sciences and Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore, 639798, Singapore.

Currently, electromagnetic (EM) pollution poses severe complication toward the operation of electronic devices and biological systems. To this end, it is pertinent to develop novel microwave absorbers through compositional and structural design. Porous carbon (PC) materials demonstrate great potential in EM wave absorption due to their ultralow density, large surface area, and excellent dielectric loss ability. However, the large-scale production of PC materials through low-cost and simple synthetic route is a challenge. Deriving PC materials through biomass sources is a sustainable, ubiquitous, and low-cost method, which comes with many desired features, such as hierarchical texture, periodic pattern, and some unique nanoarchitecture. Using the bio-inspired microstructure to manufacture PC materials in mild condition is desirable. In this review, we summarize the EM wave absorption application of biomass-derived PC materials from optimizing structure and designing composition. The corresponding synthetic mechanisms and development prospects are discussed as well. The perspective in this field is given at the end of the article.
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http://dx.doi.org/10.1007/s40820-019-0255-3DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7770762PMC
March 2019

Nanofiber network with adjustable nanostructure controlled by PVP content for an excellent microwave absorption.

Sci Rep 2019 Mar 12;9(1):4271. Epub 2019 Mar 12.

College of Materials Science and Technology, Nanjing University of Aeronautics and Astronautics, Nanjing, 210016, P.R. China.

Carbon nanofibers were widely utilized to improve microwave absorption properties since they are a promising lightweight candidate. Adjustable conductive nanostructures of carbon nanofibers were synthesized by electrospinning technique. The conductive network is controlled by the polyvinyl pyrrolidone (PVP) content due to the special hygroscopicity of PVP. The increased adhesive contacts of nanofibers provide more transmission paths for electrons to reduce the effect of air dielectric. Satisfactorily, the carbon nanofibers that carbonized from the polyacrylonitrile (PAN) and PVP (the mass ratio is 6:4) show excellent microwave absorption performance. The minimum reflection loss (RL) value is -51.3 dB at 15.2 GHz and the maximum effective absorption frequency width (<-10 dB) is 5.1 GHz with the matching thickness of only 1.8 mm. Thereby, we believe that this research may offer an effective way to synthesize lightweight carbon nanofibers microwave absorbents.
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http://dx.doi.org/10.1038/s41598-019-38899-8DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6414720PMC
March 2019

Nano sulfur particles decorated bi-lamella composites for superior electromagnetic wave absorption.

J Colloid Interface Sci 2019 May 18;543:138-146. Epub 2019 Feb 18.

Laboratory of Solid State Microstructures, Nanjing University, Nanjing 210093, PR China.

Sulfur nanoparticles decorated bi-lamella composites with multiple interfaces were constructed by introducing a handful of nano-S particles into the interlayer of graphene and poly (3,4-ethylene-dioxythiophene): poly (styrenesulfonate) (GSP). Graphene and PEDOT: PSS with large surface areas and abundant functional groups offer adequate contact sites for the chemical confinement of sulfur nanoparticles. Based on the equivalent circuit theory, insulating sulfur could commendably regulate hopping conduction by slowing down the hopping electrons among the layers. Meanwhile, the substantial conductivity differences result in evident interfacial polarization (MWS effect). With the favorable permittivity behavior and multiple interfacial polarizations, more microwaves could be brought into the interior of absorber and were consumed. The GSP-paraffin composites with 35 wt% GSP loading possess the minimum reflection loss (RL) value of -21.9 dB at 1.6 mm, and effective absorption bandwidth of 4.72 GHz. This work demonstrates the significant role of multi-interfaces on microwave absorption.
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http://dx.doi.org/10.1016/j.jcis.2019.02.053DOI Listing
May 2019

Integrating carbonyl iron with sponge to enable lightweight and dual-frequency absorption.

Nanotechnology 2019 May 23;30(19):195703. Epub 2019 Jan 23.

College of Materials Science and Technology, Nanjing University of Aeronautics and Astronautics, Nanjing 211100, People's Republic of China.

In this work, sponge impregnated with iron pentacarbonyl was utilized to obtain a novel composite in which the carbonyl iron (CI) was embedded in a graphitized carbon matrix (CI-C). The CI that results from the thermal pyrolysis of iron pentacarbonyl can homogeneously disperse into the pore structures of the sponge skeleton, which not only improves the stability of the CI, but also modifies the impedance matching character. Moreover, the sponge bulk turns into graphitized carbon during the heat treatment (graphitized catalysis of magnetic metal on carbon at high temperature). Due to the respective strong dissipation ability of CI and the graphitized carbon matrix, the as-prepared CI-C sample exhibits a good microwave absorption performance, including expanding the effective absorption bandwidth and reduced weight, compared to pure CI. Moreover, the sample with 30 wt% paraffin loading not only shows strong reflection loss absorbing ability, but also possesses continuous dual-absorption peaks (9.96 GHz, -38.7 dB, and 13.8 GHz is -37.6 dB). This work not only extends the application of carbonyl iron as a lightweight microwave absorber with dual-absorption peaks but also initiates a new approach for artificially designed carbon-based composites via a simple sponge-impregnation method.
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http://dx.doi.org/10.1088/1361-6528/ab0126DOI Listing
May 2019

Interfacial polarizations induced by incorporating traditional perovskites into reduced graphene oxide (RGO) for strong microwave response.

Dalton Trans 2019 Feb;48(7):2359-2366

School of Electronic Science and Engineering, Nanjing University, Nanjing 210093, P. R. China.

Incorporation of traditional perovskites into reduced graphene oxide (RGO) is an effective strategy to develop useful microwave absorbents. Taking advantage of the suitable impedance of La0.7Sr0.3MnO3 (LSMO), a novel and available microwave absorber was obtained. Here, we showed an outstanding and stable RGO material decorated with LSMO that can be used as an active component of microwave absorption devices. The as-prepared LSMO/RGO composites adopted the merits of RGO and LSMO and provided good properties, such as a controllable dissipation ability, optimized impedance matching, and broadened effective frequency bandwidth. For example, the minimum reflection loss (RL) value of LSMO/RGO composites with a 60% loading filler ratio reached -38.81 dB with a matching thickness of only 1.7 mm. Furthermore, the effective frequency bandwidth can be as wide as 5.64 GHz, with a thickness of 1.95 mm. Therefore, this work initiates a brand new avenue for artificial research of new materials for electromagnetic wave absorption.
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http://dx.doi.org/10.1039/c8dt04966aDOI Listing
February 2019

Functionalized Carbon Nanofibers Enabling Stable and Flexible Absorbers with Effective Microwave Response at Low Thickness.

ACS Appl Mater Interfaces 2018 Dec 20;10(48):41535-41543. Epub 2018 Nov 20.

Laboratory of Solid State Microstructures , Nanjing University , Nanjing 210093 , P. R. China.

Lots of work has been done to develop microwave absorbing materials (MAM) utilized as flexible electronic devices and communication instruments. Conventionally developed powder MAM are often limited in practical applications because of the bad stability and poor durability, which is out of the scope for exploiting flexible and long-term microwave absorbers. To overcome such limitations, a facile and binder-free technique from a Co-based zeolitic imidazolate framework (ZIF-67, a member of metal-organic frameworks)-coated carbon fiber precursor is developed for the in situ horizontal growth of CoO nanoparticles, which embedded nitrogen-doped carbon array (triangular nanoplates) on the surface of carbon fibers in the carbon paper (NC-CoO/CP) as low-thickness MAM. The maximum reflection loss (RL) values reaches -16.12 and -34.34 dB when the thickness is 1.1 and 1.5 mm, respectively. As the thickness increases, the absorbing performance at low frequency performs well (RL < -20 dB). The hierarchical architecture is facilely originated from a metal-organic framework precursor. In view of the simple preparation technique, NC-CoO/CP exhibit huge potential in large-scale production of portable microwave absorbing electronic devices with strong microwave response at low thickness.
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http://dx.doi.org/10.1021/acsami.8b16088DOI Listing
December 2018

Constructing multi-interface MoC/[email protected] nanorods for a microwave response based on a double attenuation mechanism.

Dalton Trans 2018 Oct;47(41):14767-14773

School of Electronic Science and Engineering, Nanjing University, Nanjing 210093, P. R. China.

In this work, novel one-dimensional (1D) Mo2C/[email protected] nanorods (MCRs), using a metal-organic framework (zeolitic imidazolate framework; ZIF-67) as the coating layer to form multi-interfaces, were formed via a facile hard template method. Compared with previous works relating to porous-carbon-based Mo2C nanocomposites, the well-designed MCRs in this study possess a double attenuation mechanism due to the existence of the dielectric materials Mo2C and remaining carbon (RC) and the magnetic compound Co. Thanks to a new design and the multiple useful compounds, the as-prepared MCRs have the features of demonstrating multi-interfacial polarization, a large surface area and highly isotropic dissipation. Hence, the samples not only inherit the excellent microwave absorbing abilities of Mo2C but they also have a broadened effective bandwidth. For example, the minimum reflection loss (RL) value of MCRs with 35% sample loading could reach -47.98 dB. More importantly, RL values of less than -10 dB can be observed from 11.08 to 17.08 GHz (an effective bandwidth of 6.0 GHz) with a matching thickness of 1.6 mm, which is much better than previous work involving porous-carbon-based Mo2C nanocomposites. Firstly, we have reasonably redesigned the samples to have good absorbing properties for practical applications. Secondly, we have paved a highly efficient and universal way to synthesize 1D microwave absorbers with multiple valuable interfaces.
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http://dx.doi.org/10.1039/c8dt03282cDOI Listing
October 2018

Cobalt nanoparticles embedded nitrogen-doped porous graphitized carbon composites with enhanced microwave absorption performance.

J Colloid Interface Sci 2019 Jan 25;533:297-303. Epub 2018 Aug 25.

College of Materials Science and Technology, Nanjing University of Aeronautics and Astronautics, Nanjing 211100, PR China. Electronic address:

For high-efficiency microwave absorption, both of the self loss of materials (dielectric loss and magnetic dissipation) and structural attenuation (multiple scattering, interfacial polarization) play important roles. In addition, the magnetic/dielectric materials combination, and void volume introduction can also contribute to the optimization of impedance matching. Given that, 2D cobalt nanoparticles embedded nitrogen-doped porous graphitized carbon composites ([email protected]) were fabricated via a simple sacrificial templates method, where the CoAl-layered double hydroxide (CoAl-LDH) nanosheets were prepared to hold ZIF-67 and then decomposed during the sintering process. In this work, strong dielectric attenuation, multiple microwave scattering and dielectric polarization, as well as shortened impedance matching all make for the nice microwave absorption performance. This work not only exhibits the importance in materials selection and structure design, but also demonstrates the close relation between matching thickness and response frequency at maximum reflection loss (RL) peak.
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http://dx.doi.org/10.1016/j.jcis.2018.08.083DOI Listing
January 2019

Enhanced Low-Frequency Electromagnetic Properties of MOF-Derived Cobalt through Interface Design.

ACS Appl Mater Interfaces 2018 Sep 5;10(37):31610-31622. Epub 2018 Sep 5.

College of Materials Science and Technology , Nanjing University of Aeronautics and Astronautics , Nanjing 211100 , P. R. China.

It is still a formidable challenge to ameliorate the low-frequency electromagnetic property of conventional microwave-absorbing materials, which may be conquered by the coexistence of both strong dielectric and magnetic loss ability in low-frequency range and the perfect balance between complex permittivity and permeability with the help of structural design. Herein, by virtue of appropriate composition and structure of Co[HCOO]·dimethylformamide parallelepipeds, one-dimensional spongelike metallic Co can be directly synthesized for the first time with strong magnetic loss in the low-frequency range. Furthermore, attenuation ability and impedance matching condition have been improved through the construction of interfacial structures between inner cobalt and surface carbon. With the structure of carbon changed from fragments to vertically aligned nanoflakes and eventually to a thick layer with extra fragments, the dielectric loss would be continuously strengthened, while the magnetic loss maintains well, followed by a remarkable decline. A perfect balance between dielectric and magnetic loss has been achieved by sample S-Co/C-0.3 with minimum reflection loss value around -20 dB and effective absorption frequency range about 3.84 GHz in the C band. Excellent microwave absorption performance can also be realized in X and Ku bands. In addition, as-prepared Co and Co/C composites can also be potentially applied in electromagnetic shielding. The findings may pave the way for the manufacture of metal-based metal-organic framework derivatives and the design of lightweight low-frequency electromagnetic materials.
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http://dx.doi.org/10.1021/acsami.8b10685DOI Listing
September 2018

Encapsulating metal nanoparticles inside carbon nanoflakes: a stable absorbent designed from free-standing sandwiched composites.

Dalton Trans 2018 Aug;47(33):11713-11721

College of Materials Science and Technology, Nanjing University of Aeronautics and Astronautics, Nanjing 211106, P. R. China.

Combination of carbon and metal materials is a good strategy to develop lightweight microwave absorbents. Taking advantage of the encapsulation property of carbon nanoflakes, a stable microwave absorber could be achieved. In this study, we managed to achieve sandwich-shaped Ni/C nanoflakes via a simple route involving a one-step hydrothermal method towards Ni(OH)2 nanosheets, followed by a calcination procedure. These sandwiched carbon nanoflakes not only increased the interfacial polarization, but also resulted in the absolute stability of metal nanoparticles. Considering the higher possibility of some support plates to be wrinkled, which would bring about imperfect sandwiched structures, the free-standing sandwiched composites were in a relatively good shape. Furthermore, the intensive conductive loss could be highly responsible for better microwave absorption properties by adjusting the carbonization temperature. The minimum reflection loss (RL) value of Ni/C composites that were obtained with a 25% loading filler ratio could reach -24.3 dB with a matching thickness of only 1.5 mm. Moreover, the effective microwave absorption bandwidth (<-10 dB) could reach to 4.0 GHz with thicknesses of both 1.3 mm and 1.4 mm. Therefore, the sandwich-shaped Ni/C nanoflakes could be exploited as an effective and lightweight microwave absorber.
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http://dx.doi.org/10.1039/c8dt02713gDOI Listing
August 2018

Extended Working Frequency of Ferrites by Synergistic Attenuation through a Controllable Carbothermal Route Based on Prussian Blue Shell.

ACS Appl Mater Interfaces 2018 Aug 20;10(34):28887-28897. Epub 2018 Aug 20.

College of Materials Science and Technology , Nanjing University of Aeronautics and Astronautics , Nanjing 210016 , China.

One of the major hurdles of ferrite-based microwave absorbing materials is the limited working frequency that urgently calls for an effective modification technique. Herein, a controllable carbothermal route has been developed to ameliorate the microwave absorption performance of FeO nanospheres by using metal-organic frameworks (MOFs) shell as a carbon source with changing ramping rates. An enhanced synergistic attenuation induced by varied composition and tailored morphology is of great importance, which can be regarded as the superiority of the comprehensive (magnetic and dielectric), rather than unilateral (dielectric), modification technique. The drawbacks of dielectric modification can be concluded as the separated attenuation mechanisms at discrete frequencies, proven by the construction of the core-shell structured [email protected] blue composite. The advantages of magnetic modification can also be confirmed by a series of Fe-based composites with unique composition and tailored structure derived from the [email protected] blue composite at a distinct heating rate. Further, the superiority can be summarized as the rearrangement of magnetic loss by exceeding the Snoek limit and the reinforcement of dielectric loss by enhancing the electrical conductivity and introducing multiple polarization processes. Consequently, the sample obtained at 10 °C min, which contains Fe and FeO, shows an extended working frequency of 14.05 GHz, with a thickness less than 5 mm and a high reflection loss value of -48.04 dB at 1.55 mm. This work not only offers a novel carbothermal route based on MOFs coating to prepare desired magnetic composites, but also acquires deeper insights of the comprehensive modification technique, which may pave the way for designing high-performance electromagnetic devices.
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http://dx.doi.org/10.1021/acsami.8b09682DOI Listing
August 2018

The flaky porous FeO with tunable dimensions for enhanced microwave absorption performance in X and C bands.

Nanotechnology 2018 Jul 27;29(29):295603. Epub 2018 Apr 27.

College of Material Science and Technology, Nanjing University of Aeronautics and Astronautics, Nanjing 210016, People's Republic of China.

Special electric and magnetic characteristics make FeO widely applied in the electromagnetic (EM) wave absorption region. However, for pure FeO, it is still a challenge to simultaneously obtain high absorption intensity and broadband absorption at a low thickness, owing to its low dielectric property. As we realized, flake configuration and the porous structure have obviously promote the EM wave absorption property. Because the former can lead to multi-reflection between flakes and the latter is conductive to interface polarization, flaky FeO with a porous and coarse surface was designed to overcome the deficiency of traditional FeO particles. The experimental results demonstrate that the flaky configuration is conductive to enhancing the dielectric coefficient and optimizing impedance matching. Moreover, the complex permittivity rises with the aspect ratio of the sheet. Under a suitable dimension, the flaky FeO could acquire targeted EM wave absorption capacity in the X band (8-12 GHz). In detail, the maximum reflection loss (RL) could reach a strong intensity of -49 dB at 2.05 mm. The effective absorption bandwidth (EAB) with RL below -10 dB is 4.32 (7.52-11.84) GHz, which is almost equivalent to the whole X band (8-12 GHz). Even more exciting, when regulating the thickness between 2.05 and 3.05 mm, the EAB could cover the entire C and X bands (4-12 GHz). This study provides a good reference for the future development of other ferromagnetic materials toward specific microwave bands.
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http://dx.doi.org/10.1088/1361-6528/aac0deDOI Listing
July 2018

Porous-carbon-based MoC nanocomposites as excellent microwave absorber: a new exploration.

Nanoscale 2018 Apr;10(15):6945-6953

College of Materials Science and Technology, Nanjing University of Aeronautics and Astronautics, Nanjing 211106, P. R. China.

In this study, we report a porous-carbon-based Mo2C nanocomposite (NCs) as the microwave absorber via typical carbothermal reduction using metal-organic frameworks (MOFs) and polyoxometalates (POMs) as the precursors, which have been rarely applied in electromagnetic (EM) wave absorption areas. The elaborately designed NCs not only bring about good impedance matching, but also possess strong dissipation ability due to the large surface areas and porous features. Thanks to the material characteristics as well as structural advantages, the as-prepared Mo2C/C NCs with 20 wt% sample loading exhibit remarkable microwave absorbing performance. The minimum RL value reaches -49.19 dB at matching thickness of 2.6 mm, and the best effective bandwidth (RL < -10 dB) of 4.56 GHz at 1.70 mm was also achieved. Moreover, the NCs overcome the intrinsic drawback of traditional carbon materials, that is, centralized effective absorption always occurred at high frequency (>10 GHz) and the minimum RL value of the NCs shifted to 9.04 GHz. Clearly, in this study, we not only developed the Mo2C NC as the new light absorber, but also paved the way to synthesize other available transition metal carbides using MOFs and POMs.
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http://dx.doi.org/10.1039/c8nr01244jDOI Listing
April 2018

A Voltage-Boosting Strategy Enabling a Low-Frequency, Flexible Electromagnetic Wave Absorption Device.

Adv Mater 2018 Apr 7;30(15):e1706343. Epub 2018 Mar 7.

School of Materials Sciences and Engineering, Nanyang Technological University, 50 Nanyang Avenue, 639798, Singapore.

Nowadays, low-frequency electromagnetic interference (<2.0 GHz) remains a key core issue that plagues the effective attenuation performance of conventional absorption devices prepared via the component-morphology method (Strategy I). According to theoretical calculations, one fundamental solution is to develop a material that possesses a high ε' but lower ε″. Thus, it is attempted to control the dielectric values via applying an external electrical field, which inducts changes in the macrostructure toward a performance improvement (Strategy II). A sandwich-structured flexible electronic absorption device is designed using a carbon film electrode to conduct an external current. Simultaneously, an absorption layer that is highly responsive to an external voltage is selected via Strategy I. Relying on the synergistic effects from Strategies I and II, this device demonstrates an absorption value of more than 85% at 1.5-2.0 GHz with an applied voltage of 16 V while reducing the thickness to ≈5 mm. In addition, the device also shows a good absorption property at 25-150 °C. The method of utilizing an external voltage to break the intrinsic dielectric feature by modifying a traditional electronic absorption device is demonstrated for the first time and has great significance in solving the low-frequency electromagnetic interference issue.
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http://dx.doi.org/10.1002/adma.201706343DOI Listing
April 2018

Excellent microwave response derived from the construction of dielectric-loss 1D nanostructure.

Nanotechnology 2018 May 23;29(19):195603. Epub 2018 Feb 23.

College of Material Science and Technology, Nanjing University of Aeronautics and Astronautics, Nanjing 210016, People's Republic of China.

Increasing efforts have recently been devoted to the artificial design and function of nanostructures for their application prospects in catalysis, drug delivery, energy storage, and microwave absorption. With the advantages of natural abundance, low cost, and environment friendliness, a one-dimensional (1D) MnO nanowire (MW) is the representative dielectric-loss absorber for its special morphology and crystalline structure. However, its low reflection loss (RL) value due to its thin thickness limits its wide development and application in the microwave absorption field. In this work, artificially designed [email protected]@C (MCs), namely, 1D hollow carbon nanotubes filled with nano-MnO, were designed and synthesized. It is found that the RL value of the MC is almost lower than -10 dB. Furthermore, the RL value was able to achieve -18.9 dB with an effective bandwidth (-10 dB) of 5.84 GHz at 2.25 mm. Simultaneously, the dielectric and interfacial polarization became stronger while the impedance matching was much better than in the single MWs. Hence, the rational design and fabrication of micro-architecture are essential and MC has great potential to be an outstanding microwave absorber.
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http://dx.doi.org/10.1088/1361-6528/aab1c2DOI Listing
May 2018

A Versatile Route toward the Electromagnetic Functionalization of Metal-Organic Framework-Derived Three-Dimensional Nanoporous Carbon Composites.

ACS Appl Mater Interfaces 2018 Mar 28;10(10):8965-8975. Epub 2018 Feb 28.

College of Materials Science and Technology , Nanjing University of Aeronautics and Astronautics , Nanjing 211100 , P. R. China.

Designable electromagnetic parameters accompanied by a low density of metal-organic framework (MOF)-derived metal/carbon composites are essential prerequisites for excellent microwave-absorbing materials. However, the conventional route is confined to slight modification of the physicochemical properties of metal species and carbon, which also restricts the functionalization of MOF-derived materials. Here, a facile technique has been improved by making full use of highly porous structure to uniformly introduce metallic Co nanoparticles into carbon matrix derived from Cu(btc). Through changing the starting amount of Co sources, the composition of the final products can be tuned, offering an effective route to control electromagnetic properties. Multiple attenuation mechanisms are employed to realize excellent reflection loss performance, which can be clarified by modified equivalent circuit mode. Effective frequency bandwidth ( f) over the whole X band can be obtained by optimizing interfacial polarization through changing interface area and electrical conductivity. Broad f covering almost the whole K band from 12.3 to 18 GHz with a thin thickness of 1.85 mm can be gained through improving impedance matching and enhancing conduction loss. The present work not only sheds light on the easy fabrication of high-performance lightweight microwave-absorbing materials but also paves the way for extending functionalities of MOF-derived carbon composites.
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http://dx.doi.org/10.1021/acsami.8b00320DOI Listing
March 2018

Tailoring the input impedance of FeCo/C composites with efficient broadband absorption.

Dalton Trans 2017 Nov;46(43):14926-14933

School of Electronic Science and Engineering, Nanjing University, Nanjing 210093, P. R. China.

Proper impedance matching and strong attenuation capabilities are crucial factors for an excellent microwave absorbent. Significant attention and effort have been focused on the attenuation capabilities, whereas little attention has been paid to impedance matching, which is particularly important to design broadband absorbing materials. In this study, coin-like porous FeCo/C composites were successfully prepared by a simple carbon thermal reduction method. The Z/Z values of the FeCo/C composites were calculated to investigate the effects of the Fe/Co molar ratio and structure on the impedance matching. The results show that the coin-like porous samples were equipped with optimal impedance matching (Z/Z ≈ 1) and broad frequency bandwidth. The coin-like porous structure can induce multiple scattering and extend the travel path of the waves, which is in favour of electromagnetic loss. In this way, the effective frequency bandwidth (RL < -10 dB) as large as 6 GHz (from 11.36 to 17.36 GHz) has been achieved at a thickness of 2 mm when the Fe/Co molar ratio is 4 : 6. In addition, the average frequency broadband reached 5.57 GHz in the thickness range of 2-2.6 mm. We believe that this study may provide a new strategy for tuning the impedance matching for optimal broadband absorbers.
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http://dx.doi.org/10.1039/c7dt02840gDOI Listing
November 2017

Cross-Linking-Derived Synthesis of Porous CoNi/C Nanocomposites for Excellent Electromagnetic Behaviors.

ACS Appl Mater Interfaces 2017 Nov 25;9(44):38814-38823. Epub 2017 Oct 25.

Laboratory of Solid State Microstructures, Nanjing University , Nanjing 210093, PR China.

The magnet/dielectric composites with tunable structure and composition have drawn much attention because of their particular merits in magnetoelectric properties compared with the sole dielectric or magnetic composites. In addition, porous materials at the nanoscale can satisfy the growing requirements in many industries. Therefore, constructing porous metal alloy/carbon nanocomposites is to be an admirable option. Unfortunately, traditional synthesis methods involve multistep routes and complicated insert-and-remove templates approaches. Here we report a facile process to synthesize CoNi/C composites via a spontaneous cross-linking reaction and subsequent calcination process, during which multiple processes, including reducing polyvalent metal ions, forming alloy, and encapsulating alloy nanoparticles into porous carbon matrix, are achieved almost simultaneously. By adjusting the feed ratio of Co to Ni ions, controllable composition of CoNi/C composites can be gained. It should be noted that the CoNi/C composites are demonstrated to be excellent microwave absorbers from every aspect of assessment criteria including reflection loss, effective bandwidth, thickness, and weight of absorber. Our study opens up a promising technique for the synthesis of alloy/carbon composites with porous nanostructures with target functionalities.
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http://dx.doi.org/10.1021/acsami.7b13411DOI Listing
November 2017

Constructing hierarchical porous nanospheres for versatile microwave response approaches: the effect of architectural design.

Dalton Trans 2017 Oct;46(41):14264-14269

College of Materials Science and Technology, Nanjing University of Aeronautics and Astronautics, Nanjing 211100, P. R. China.

Owing to their immense potential in functionalized applications, tremendous interest has been devoted to the design and synthesis of nanostructures. The introduction of sufficient amount of microwaves into the absorbers on the premise that the dissipation capacity is strong enough remains a key challenge. Pursuing a general methodology to overcome the incompatibility is of great importance. There is widespread interest in designing the materials with specific architectures. Herein, the common absorber candidates were chosen to feature the hierarchical porous [email protected]@FeO nanospheres. Due to the reduced skin effect (induced by low-conductivity FeO outer layer), multiple interfacial polarizations and scattering (due to the ternary hierarchical structures and nanoporous inner core) as well as the improved magnetic dissipation ability (because of multiple magnetic components), the material design enabled a promising microwave absorption performance. This study not only illustrates the primary mechanisms for the improved microwave absorption performance but also underscores the potential in designing the particular architectures as a strategy for achieving the compatibility characteristics.
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http://dx.doi.org/10.1039/c7dt03207bDOI Listing
October 2017
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