Ke Bi

• Ph.D
• Professor at Beijing University of Posts and Telecommunications

A tunable dual-band ferrite-based metamaterial has been investigated by experiments and simulations. The negative permeability is realized around the ferromagnetic resonance (FMR) frequency which can be influenced by the dimension of the ferrites. Due to having two negative permeability frequency regions around the two FMR frequencies, the metamate...

All-dielectric metamaterials have emerged as a promising platform for low-loss and highly efficient terahertz devices. However, existing fabrication methods have difficulty in achieving a good balance between precision and cost. Here, inspired by the nano-template-assisted self-assembly method, we develop a micro-template-assisted self-assembly (MT...

Magnetically tunable wideband microwave filters have been designed and prepared by using ferrite-based metamaterial structures. The microwave properties of the filters have been investigated by experiments and simulations. The negative permeability appears around the ferromagnetic resonance frequency, which leads to a remarkable stopband for the ba...

In nature, most materials are composed of atoms with periodic structures. Hence, it's impossible to introduce topological structures into their lattice compose, because the atoms as basic blocks cannot be modulated. However, the lattice compose of metamaterials can be designed conveniently. In our work, we propose to introduce topological non-trivi...

Herein, the conception of 2.5D metamaterial is proposed. The basic idea of the 2.5D metamaterial is to build “3D” metamaterial by stacking 2D metasurfaces layer‐by‐layer. In this design, the trapezoidal prism units (3D) is built up by stacking a series of rectangle units (2D) together. This means, in the conception of 2.5D metamaterial, any kind of...

Nowadays, modern communication system relies on the designs of high-performance devices to enhance communication effect for high quality of life and smart city system. As a crucial signal processing step, microwave filter removes unwanted frequency components away from the received signal and enhances the useful ones. However, large loss, bulky siz...

Employing organo‐metal zinc acetylacetonate (Zn(acac)2) as the zincic source, various zinc oxide (ZnO) products with different morphologies have been synthesised via a typical solvothermal method in different polar organic solvents. Quasi‐spherical and rod‐like structures with diverse sizes are successfully fabricated in the methanol, ethanol, 1‐pr...

Dielectric metasurfaces provide the new freedom to implement information encoding and image hiding with monolayer of artificial atoms instead of bulky optical components to enable wavelength, phase and polarization modulations. We proposed an optical encryption scheme by integrating the Visual Cyptography (VC) with the phase-encoding technique for...

Topological insulator two-dimensional (2D) Bi 2 Se 3 hexagonal nanoplates, which are highly insulating in the bulk and have a conductive topological surface state, have been prepared via an “EG- (ethylene glycol-) sol” method and characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), and scanning electron microscopy (SEM)...

Photoelectrocatalytic CO2 reduction to CO was achieved on Cu2O/Cu2S nanoparticles which are immobilized in TiO2 nanocavity array. The Cu2S shell was obtained by ions exchange reaction of O²⁻ and S²⁻ on the surface of Cu2O by a chemical vapor deposition with Na2S precursor. This coating can protect the Cu2O nanoparticle from photocorrosion during ph...

In this paper, hierarchically porous MgMn2O4 microspheres, which assembled with average size of about 30 nm nanosheets, have been synthesized by a facile solvothermal process followed by calcination method. The electrocatalytic properties of the products towords oxygen reduction reaction (ORR) are further investigated. Benefitting from its unique s...

A simple and novel slot-coupled dielectric resonator-based filter (DRF) with wideband performance is proposed, and the designed geometric parameters of the filter are discussed in detail. The proposed filter comprises a substrate, a microstrip line, and three dielectric resonators (DRs), which are positioned on the center of the corresponding slots...

Plasmonic catalysis of solar water splitting has been extensively exploited these years for the fast-growing energy demands and environmental friendliness. However, most of the plasmonic systems are restricted on the noble metals and semiconductors, which limited the cost efficiency of the photocatalysts and further investigations of metal plasmons...

Recently, all-dielectric metasurfaces (AMs) have emerged as a promising platform for high-efficiency devices ranging from the terahertz to optical ranges. However, active and fast tuning of their properties, such as amplitude, phase and operating frequency, remains challenging. Here, a generic method is proposed for obtaining high-efficiency active...

Periodically nanoporous MoS2@TiO2 catalysts were designed to enhance the nonmetal plasmonic effect for solar H2 evolution. The phase transition from 2H‐ to 1T‐MoS2 coupled with the surface S vacancies is responsible for the enhanced localized surface plasmon resonance, leading to a superior H2 yield rate. The work by Ke Bi, Yanan Hao, Yang Yang and...

Ultrathin porous spinel structure ZnCo2O4 nanosheets (ZCONSs) are successfully prepared by a facile combination of hexamethylenetetramine‐assisted mild water bath reaction and a heat treatment process. The ultrathin film shape and porous of the as‐prepared ZCONSs were demonstrated by a transmission electron microscope. Such a specific nanostructure...

Orbital angular momentum (OAM) beams can be generated at many microwave frequencies by using antenna array. However, the complexity of system and inability to transmit over long distances limit the applications of OAM beams in radio domain. Here, a significantly simplified global positioning system (GPS) ceramic antenna array is employed to generat...

In this paper, we report a new and generic method for all-dielectric resonators operating at terahertz (THz) frequencies based on polymer/ceramic composite particles. In this method, the polymer solution is added into ceramic powders (strontium titanate) and prilling technology is employed to make them become polymer/ceramic composite micro particl...

Compact microstrip antennas based on split-ring resonator (SRR) structure are proposed and fabricated in this paper. The resonant frequency of the antennas is discussed upon different geometric structures. The influencing mechanism of the antenna parameters on resonant frequency is analyzed. The analytical and experimental analyses are carried out...

An optically controlled system for generating and continuously steering radio frequency (RF) signals with double orbital angular momentum (OAM) modes is proposed and experimentally demonstrated. The optical carrier’s utilization efficiency can be doubled through the distinct electro-optical modulation, which is based on two single-sideband modulati...

Phase and defect engineering of the heterostructured MoS2@TiO2 nanoporous film is investigated to achieve a broad solar spectrum light absorption and high solar water splitting efficiency. The phase transition from the semiconducting 2H‐MoS2 to the metallic 1T‐MoS2 is achieved by a hydrothermal exfoliation treatment. Experimental studies elucidate...

When a dielectric meta-atom is placed into a subwavelength metallic aperture, 20-fold enhanced electromagnetic transmission through the aperture is realized at the meta-atom’s resonant frequency. Additionally, when the incident electromagnetic power increases, thermal energy gathered by the meta-atom, which is converted from electromagnetic losses,...

Nanomaterials are playing more and more important roles in modern industry, while the large-scale fabrication and dispersibility still need to be addressed. This report explores the uniform fabrication and morphology control of ultrafine BaTiO 3 (BT) nanocrystals using a 'TEG-sol' method. By varying the reactant concentration, the obtained product...

Metasurface is emerging as an important platform to design various functional devices due to the superior capability in controlling amplitude, phase and polarization of light through its ultrathin engineering interface. A polarized-selective hologram of all-dielectric metasurface is proposed to reconstruct multiplexed holographic images on differen...

Microwave radomes exhibiting bandpass behavior are highly desirable for antenna systems. However, most of these radomes are not frequency switchable owing to their fixed structures. Here, a switchable metasurface based on complementary diamond-ring-shaped resonators is proposed for radomes. The microwave properties of the metasurface are investigat...

Microwave dielectric ceramics are the key materials in low-temperature co-fired ceramics (LTCC) technology. In the so many material systems, Mo-based microwave dielectric ceramics have attracted world-wide attention in recent years due to their low intrinsic sintering temperature and high quality factor (Q×f). In combination with its low dielectric...

CoS2 nanoparticles co‐doped with N and P are embedded in the periodic TiO2 nanocavities, which serve as bi‐functional electrocatalysts for oxygen reduction and evolution reactions. As described by Ke Bi, Xiaohui Wang, Yang Yang, and co‐workers in article number 1804540, the increased number of active sites results from N‐dopants and outstanding sta...

Ba (Zr0.2Ti0.8) O3-50% (Ba0.7Ca0.3) TiO3 (BZT-0.5BCT) ceramics with different doping contents of Pr³⁺ were prepared by the conventional solid-state reaction. The phase structure and crystallinity of the fabricated ceramics were investigated by X-ray diffraction, Raman spectroscopy, and scanning electron microscopy. Photoluminescence (PL) emission s...

By using complementary rhombus resonator (CRR), a small-size and low-profile microstrip patch antenna (MPA) with broad bandwidth has been proposed. Parametric studies were conducted to illustrate the working principle of the proposed antenna. An additional resonance is introduced by the CRR to broaden the bandwidth. Compared with the MPA without th...

Perovskite oxides doped with rare earth elements are promising multifunctional materials. In this paper, Pr³⁺-doped (Na0.52K0.4415Li0.0385)(Nb0.8735Ta0.064Sb0.0625)O3 ceramics, abbreviated as KNN-Pr, are prepared by traditional solid-state method. Compared to previous reports, the KNN matrix is optimized by Li, Ta and Sb elements, which shows outst...

SrTiO3(STO):Pr³⁺ nanopowders are synthesized because of their excellent photoluminescence (PL) performance. The PL intensity is enhanced by morphological control and oxygen vacancy. The “TEG-sol” method is used to prepare STO:Pr³⁺ nanopowders with a size lower than 10 nm. Abundant oxygen vacancies are formed in the nanopowders without any further p...

A porous SrTiO3 (STO) three-dimensional (3D) hierarchical structure is fabricated by a rapid “TEG-sol” method under atmospheric pressure. The STO architecture is characterized by the hollow-sphere assemblies of well-crystallized sub-10 nm cubes. The formation kinetics of the STO hierarchical structure reveals that alkalinity of the reaction solvent...

Herein, AuxCu alloy nanoparticles (NPs) embedded into TiO2 nanocavity arrays (NCAs) were synthesized by e-Beam deposition and thermal dewetting. The periodically dispersed AuxCu NPs displayed strong ultraviolet-visible light absorption through plasmonic resonance, especially after forming an AuxCu-CuS core-shell heterostructure by sulfurization. Wh...

Polymer composite films with high energy density as well as high efficiency are promising dielectric materials in pulsed power systems. In improving the energy discharged efficiency, poly vinylidene fluoride-hexafluoropropylene [P(VDF-HFP)] film blended with 20 vol.% poly(methylmethacrylate) (PMMA), which has a much slimmer ferroelectric hysteresis...

A simple dielectric resonator filter with thermally tunable performance is investigated. The ceramic dielectric resonator (DR) has a dielectric constant that decreases with the increase of the temperature, which plays a critical role in the proposed filter. The electromagnetic field distribution reveals the electric resonance and magnetic resonance...

Recently, the rapid development of advanced communication systems increasingly strongly demands high-performance microwave dielectric ceramics in microwave circuits. Among them, Li2ZnTi3O8 ceramics have been one of the most widely investigated species, due to its high quality factor, moderate firing conditions and low cost. However, the dielectric...

BiIO4/Bi2O2(BO2OH) heterostructure is successfully synthesised by the method of one-step hydrothermal treatment. Characterisation of BiIO4/Bi2O2(BO2OH) heterostructure is performed by X-ray diffraction, scanning electron microscope, transmission electron microscopy and ultraviolet (UV)-visible diffuse reflectance. The photocatalytic activity is mea...

A flexible all-dielectric metamaterials composed of single-layer ceramic microspheres embedded in elastomeric medium is proposed and experimentally demonstrated in terahertz (THz) range. The THz waves are strongly confined in the high-permittivity and low-loss ceramic (ZrO2) microspheres resulting in remarkable Mie magnetic resonances, which can be...

A terahertz metasurface perfect absorber with multi-band performance is demonstrated. The absorber is composed of a ground plane and four split-ring resonators (SRRs) with different dimensions, separated by a dielectric spacer. The numerical simulation results illustrate that the proposed absorber has four distinct absorption peaks at resonance fre...

Terahertz absorber has attracted much attention. However, most of them have complex structures and narrow bandwidth. Here, a wideband terahertz metasurface absorber based on Mie resonance is demonstrated. The metasurface absorber is prepared by combining four dielectric resonators with different permittivity values into a single unit cell. The abso...

Inspired by the classic hole-cavity blackbody model, we propose an open metasurface blackbody operating at microwave frequencies, whose unit cell is a dielectric resonator lying on an opaque metal plate. The resonator has a high temperature coefficient of dielectric constant, thus the blackbody can be thermally tunable. Furthermore, when the resona...

Polymer nanocomposite is a promising substitute for the energy-storage dielectric material in pulsed power systems. Barium titanate/polyvinylidenefluoride(BT/PVDF) nanocomposite is one of the mostly studied composite systems due to its comprehensive excellent dielectric properties. As the dielectric response of nanocomposite depends strongly on the...

Correction for ‘Interface structure, precursor rheology and dielectric properties of BaTiO 3 /PVDF–hfp nanocomposite films prepared from colloidal perovskite nanoparticles’ by Y. N. Hao et al. , RSC Adv. , 2017, 7 , 32886–32892.

Silicon-based all-dielectric metamaterials (SAMs), with advantages like low loss and simple structure, are attracting more and more attention. However, SAMs usually suffer from narrow bandwidth and low tunability, and thereby their applications are seriously impeded. In this work, we propose and experimentally demonstrate a tunable SAMs in terahert...

Super-aligned conductive material is a hotspot in the research of flexible and transparent conductive films. This work introduces a facile and rapid ‘TEG-sol’ method to synthesise Ag nanoparticles and their orientational alignment. Pure, well-crystallised Ag nanoparticles with polyhedron morphology are fabricated by reducing silver nitrate in TEG (...

A wideband metasurface filter based on complementary split-ring resonators (CSRR) has been prepared. The frequency and transmission bandwidth of the metasurface filters with different split widths are discussed. After analyzing the mechanism of the metasurface, the proposed metasurface filters are fabricated. The electromagnetic properties of the m...

A broadband terahertz antenna based on complementary ring-resonator is designed. The complementary ring-resonator is etched in the ground plane to stimulate the generation of a new resonant frequency. After loading the resonator, the bandwidth of the antenna can increase by 111% compared with the one without complementary ring. The cavity resonance...

An ultra-wideband polarization conversion metasurface based on S-shaped metallic structure is designed and prepared. The simulation results show that the polarization conversion bandwidth is 14 GHz for linearly polarized normally incident electromagnetic waves and the cross-polarized reflectance is more than 99% in the range of 10.3 GHz–20.5 GHz. O...

Nanocomposite materials with uniform microstructure and high permittivity have attracted extensive interest in modern electronics. The compatibility between the filler phase and the polymer matrix is crucial in preparing high-performance composites. As an alternative to conventional surface modification treatment methodologies, hydroxylated colloid...

The development of nonprecious catalysts with high electrocatalytic activities for the oxygen reduction reaction (ORR) has attracted considerable attention. In this work, we report a facile route for the synthesis of electrocatalytic manganese vanadium oxide (Mn2V2O7) with a typical thortveitite (A2B2O7) structure for the ORR. Hollow Mn2V2O7 micros...

In recent years, numerous researchers have focused on the synthesis of well-defined structure and morphology of zinc ferrite (ZnFe2O4) due to their excellent electric and ferromagnetic properties. However, the electro-catalytic properties of ZnFe2O4 have not been attached importance in nanoenergy field. In this work, monodispersed ZnFe2O4 nanoparti...

Two-dimensional materials have already become the focus of many researches due to their innovation potential in various fields related to their special structure. Particularly, more and more two-dimensional electrocatalysts are being developed for the oxygen reduction reaction (ORR). In this work, novel two-dimensional NiCo2O4 nanoflowers/reduced g...

In this work, we propose an electrostatic field concentrator using electrostatic metamaterial. Specifically, a shell with anisotropic dielectric constant is employed to concentrate the electrostatic field into core region to achieve an enhanced electrostatic field (192% of the applied electrostatic field intensity) and keep the external field undis...

Bismuth oxychloride (BiOCl) is well known for its photocatalytic activity and many methods are reported to prepare this layered-structure material. In this study, bismuth hexafluoroacetylacetonate Bi(C5HF6O2)3 was chosen as Bi source in the synthesis of BiOCl. Uniform BiOCl nanoplates were fabricated without any organic additive to control the morp...

The precise location of the Dirac-like point of a finite photonic crystal array with a triangular lattice can be identified easily from the transmittance spectrum of any output interface with the characteristic of a sharp cusp embedded in the extremum spectrum near the Dirac-like point. The transmission properties of the finite triangular lattice p...

Tungsten disulphide (WS2), which exhibits excellent saturable absorption properties, has attracted much attention in the applications of photonic devices. In this paper, WS2 is applied for the preparation of a saturable absorber (SA). Using the pulsed laser deposition (PLD) method, WS2 is deposited on the side surface of the tapered fiber. In order...

Bi2-xPbxO2(BO2OH) nanospheres are synthesised by means of one-step hydrothermal route by embedding Pb²⁺ to Bi2O²⁺2 layers. The obtained materials are characterised by X-ray diffraction, ultraviolet (UV)-vis diffuse reflectance, scanning electron microscope, transmission electron microscopy and X-ray photoelectron spectroscopy. Photocatalytic activi...

A thermally tunable slot-coupled dielectricresonatorantenna (DRA) has been designed and prepared by placing a thermosensitive ceramicresonator onto the slot. Typical magnetic resonance occurs in the resonator, which is closely related to its dielectric constant. Because the dielectric constant of the ceramicresonator decreases as the temperature in...

A frequency tunable slot-coupled dielectric resonators antenna (DRA) is investigated. Three dielectric resonators (DRs) that placed onto a rectangular coupling slot are fed through the slot. CST Microwave Studio is used to simulate the electromagnetic properties of the proposed antenna. Base on the simulated results, the magnetic resonance mode can...

Using metamaterials or transformation optics to manipulate Laplace fields, such as magnetic, electric and thermal fields, has become a research highlight. These studies, however, are usually limited to a bulk material system and to single field manipulation. In this paper, we focus on a film system and propose a general practical method applicable...

Microwave bandpass filter structure has been designed and fabricated by filling the periodically metallic apertures with dielectric particles. The microwave cannot transmit through the metallic subwavelength apertures. By filling the metallic apertures with dielectric particles, a transmission passband with insertion loss 2 dB appears at the freque...

Data file of the microwave bandpass filter. Figure A. Simulated transmission data file of metallic aperture unit cell. Figure B. Simulated transmission data file of single dielectric particle. Figure C. Simulated transmission data file for the unit cell with a series of length l Figure D. Simulated transmission data file for the unit cell with a se...

Novel strontium titanate nanocubes/reduced graphene oxide (STO/rGO) nanocomposites were successfully synthesized via a two-step route, including a rapid sol-precipitation process and a subsequent hydrothermal process. TEM images indicate that the nanocomposites are composed of rGO-supported monodispersed 5–10 nm STO nanocubes. Compared with pure ST...

In this study, a simple and delicate approach to realizing manipulation of multi-physics field simultaneously through combination of passive and active schemes is proposed. In the design, one physical field is manipulated with passive scheme while the other with active scheme. As a proof of this concept, a bifunctional device is designed and fabric...

In recent years, researchers have been exploring various Pt-free electrocatalysts to optimize the performance of regenerative fuel cell and rechargeable metal-air battery. However, similar studies in ceramic fields are still stalled. In this work, as an efficient oxygen reduction reaction (ORR) catalyst, carbon-niobium nitride (C-NbN) nanostructure...

In this work, multilayer sandwich-like LiV 3O 8 nanosheets-graphene (LiV 3O 8-G) composites were initially developed by a facile solution-based assembly followed by a thermal reduction process using graphene oxide sheets, V 2O 5 nanobelts and LiOH (aq) as raw materials. The resultant nanocomposites were further determined to be of a unique hierarch...

In this work, we numerically designed and then experimentally verified a metamaterial perfect absorber based on artificial dielectric “atoms”. This metamaterial absorber is composed of dielectric ceramic material (SrTiO3) “atoms” embedded in a background matrix on a metal plate. The dielectric “atoms” couple strongly to the incident electric and ma...

In this paper, we propose a wideband F-shaped microstrip antenna. The proposed antenna is compact with a dimension of 18×22×1 mm3, which is a benefit for the miniaturization of the antenna system. The electromagnetic properties of the antenna are analyzed with the software CST microwave studio and the measurements are performed by using a vector ne...

We numerically and experimentally demonstrated a polarization insensitive dual-band metamaterial perfect absorber working in wide incident angles based on the two magnetic Mie resonances of a single dielectric “atom” with simple structure. Two absorption bands with simulated absorptivity of 99% and 96%, experimental absorptivity of 97% and 94% at 8...

The use of various advanced functional ceramics has been widely implemented in various fields, yet still limited in energy-based fields, such as regenerative fuel cells. Here, a two graphite covered metal nitride nanoparticle ceramic (graphite-tungsten nitride and graphite-molybdenum nitride nanocomposites) was synthesized via a one-step solid phas...

A magnetically tunable metamaterial perfect absorber (MPA) based on ferromagnetic resonance is experimentally and numerically demonstrated. The ferrite-based MPA is composed of an array of ferrite rods and a metallic ground plane. Frequency dependent absorption of the ferrite-based MPA under a series of applied magnetic fields is discussed. An abso...

Hollow porous ZnCo2O4 microspheres have been successfully prepared by a simple solution-based assembly followed by calcination under an air atmosphere using zinc acetylacetonate Zn(C5H7O2)2 and cobalt acetylacetonate Co(C5H7O2)3 as raw materials. Scanning electron microscopy (SEM) and Transmission electron microscope (TEM) are used to reveal the sy...

Enhanced transmission, and specifically tunable enhanced transmission, of microwaves through a subwavelength metal aperture is of major significance for a variety of microwave applications. In this study, by placing a metamaterialresonator into a subwavelength aperture, we experimentally and numerically demonstrated a transmission enhancement of 20...

Magnetoelectric (ME) Ni/PZT/TbFe2 and TbFe2/PZT composites with two semiringstructures are prepared. The dependence between ME coupling and magnetostrictive property of the composite is discussed. Because Ni possesses negative magnetostrictive property and TbFe2 shows positive magnetostrictive property, the ME voltage coefficient of Ni/PZT/TbFe2sem...

In this study, we report the experimental demonstration of hyperbolic property in a conventional material - ferrite. The hyperbolic permeability dispersion originates from ferromagnetic resonance. Using 2D-Field mapping system, the negative refraction with a broad bandwidth of 1.5 GHz was observed in a bulk Ba-Ferrite with no magnetic field applied...

Novel nanocomposites of carbon nanotubes supported porous VOxNy nonoribbons (VOxNy-CNTs) have been synthesized by the annealing of the sol-gel mixture of CNTs and V2O5 under NH3 atmosphere as well as the ageing process in air. Besides the morphological and structural characterizations revealed by TEM, SEAD, EDS, XRD and XPS measurements, typical el...

Novel sandwich-like nanocomposites of alternative stacked ultrathin Li3VO4 nanoribbons and graphene sheets (LVO-G) were successfully developed by a facile intercalation assembly method with a post heating treatment. The characterization results demonstrate that the average size of the Li3VO4 nanoribbons with a non-layered crystal structure is a few...

Bismuth oxychloride (BiOCl) is well known for its photocatalytic activity and many methods are reported to prepare this layered-structure material. In this study, bismuth hexafluoroacetylacetonate Bi(C5HF6O2�3 was chosen as Bi source in the synthesis of BiOCl. Uniform BiOCl nanoplates were fabricated without any organic additive to control the morp...

Novel graphite-molybdenum carbide nanocomposites (G-Mo2C) are synthesized by a typical solid state reaction with melamine and MoO3 as precursors under inert atmosphere. The characterization results indicate that G-Mo2C composites are composed of high crystallization and purity of Mo2C and few layers of graphite carbon. Mo2C nanoparticles with sizes...

Magnetically tunable microwave bandpass filter structure have been designed and prepared by filling the ferrite rods into the metallic slits. The electromagnetic wave cannot propagate through the metallic slits. By filling the ferrite rods into the metallic slits, an enhanced optical transmission is obtained, which can be ascribed to the ferromagne...

A simple precipitation route has been developed to synthesize BaMoO4 with different morphologies, such as flower-like spheres, spindle-like and octahedron crystals, by using a novel organic compounds poly-(styrene-alt-maleic acid) (PSMA) as crystal growth modifier. The concentrations of PSMA and reactants have significant influences on the morpholo...