Search

In this work, a copper foam with surface oxidation and micro-nano structure was fabricated via a femtosecond laser ablation technique. The change of surface microscopic morphology and electronic structure was investigated by scanning electron microscope and X-ray photoelectron spectroscopy, respectively. Based on its rough surface, unique electronic state and oxygen defects, the laser-treated copper foam exhibited an excellent electrochemical sensing performance for glucose. The sensitivity and detection limit was determined to be 27.4517 mA cm−2 mM−1 and 1.5 μM, respectively. Furthermore, the good selectivity of present laser-treated copper foam was also demonstrated by the anti-interference experiment.

The detection of chemical samples having close dielectric response is a big challenge as the detection principle is driven by the variations in the dielectric parameters of the investigated samples. In the current work, a new metamaterial-based sensor is designed and fabricated in order to be used for the detection of liquid chemicals in the frequency range from 8 to 12 GHz. Several designs were tested using genetic algorithm, which is embedded in the CST microwave studio, in order to optimize the desired dimensions of the resonator. The simulation and experimental results showed that the proposed sensor is working well to detect various liquids, including (i) clean and waste transformer oils, (ii) corn, cotton and olive oils, (iii) branded and unbranded diesels and (iv) aniline doped ethyl-alcohol and benzene doped carbon tetrachloride. This was made possible through the occurrence of a shift in the resonant frequency of about 250 MHz, 200 MHz, 250 MHz, 150 MHz and 50 MHz for the aforementioned samples, respectively. The sensing mechanism was interpreted through the surface current and electric field distributions. We believe that the proposed sensor is viable to be used in various applications including liquid chemicals detection and industrial applications. © 2020 The Author(s). Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

Composites or structures with adequate infrared reflection and microwave transmission are favorable from practical point of view. In this paper, oriented flaky aluminum filled pyramidal-frustum shaped periodic coatings was developed, and the effect of area of flaky aluminum powder filled coating on the infrared emissivity as well as microwave transmission behavior was intensively studied combined experiments with simulation. Results shown that the increments of oriented flaky aluminum filled coating could effectively reduce infrared emissivity. After spraying flaky aluminum filled periodic structures on the microwave absorbing material, the frequency corresponding to minimal reflection loss is inclined to shift towards lower frequency. Numerical simulation results shown that reflection coefficient gradually increases with increasing in frequency and area ratio of flaky aluminum filled coating. Besides, there exists intrinsic attenuation of flaky aluminum filled pyramidal-frustum shaped periodic coating, which is probably attributed to the diffuse scattering within step edge region.

As the majority of real signals (e.g. the dynamic information obtained during bridge monitoring) are nonstationary and nonlinear, empirical mode decomposition (EMD) and its derivatives have become popular research topics in recent years worldwide. Existing methods, such as EMD, ensemble empirical mode decomposition (EEMD), complementary ensemble empirical mode decomposition (CEEMD), complete ensemble empirical mode decomposition with adaptive noise (CEEMDAN) and partly ensemble empirical mode decomposition (PEEMD), may generate modal aliasing. This condition exerts an adverse effect on the denoising and loss of high-frequency components during signal decomposition. A new method, which combines permutation entropy and spectral substitution with ensemble EMD, is proposed to solve this problem. Results of our analysis indicate that the method can extract multi-frequencies and effectively denoise signals. Advantages emerge with regard to practical signals collected via the global navigation satellite systems (GNSS) monitoring of the dynamic characteristics of a bridge in China. In conclusion, the natural vibration frequency in the x- and y-directions at each section is 0.2267 Hz, which demonstrates the health of the bridge.

Ti3SiC2 particles encapsulated by Ni0.5Zn0.5Fe2O4 shell were in-situ synthesized via a facile sol-gel method. Effects of Ni0.5Zn0.5Fe2O4 shell on electromagnetic properties of Ti3SiC2 were investigated in 2–18 GHz. Moderated complex permittivity and desirable higher complex permeability presented for the Ni0.5Zn0.5Fe2O4/Ti3SiC2 composite, resulting in strong microwave attenuation ability and good impedance matching property. The measured effective absorbing bandwidth (RL

The GNSS (Global Navigation Satellite System) real-time compaction quality supervisory system realizes the on-site quality control and process control for the construction quality of the roller compaction for filling engineering. According to the need of the GNSS real-time supervisory system in how to calculate the rolling times quickly and accurately, as well as the characteristics of the rolling track in the construction, a new method is put forward as follows: keeping the real rolling track width information, superimposing the transparent band plotted at scale and calculating the rolling times of every pixel in the image by using the alpha blending algorithm in computer graphics. In this paper, the fast calculation method of rolling times based on alpha blending algorithm will be introduced in detail. Comparing with the conventional method of grid, experiment and application results show that the new method is simple, fast and precise, that the graph of rolling figure can be fine at pixel level, making the calculation of rolling times real-time and accurate.

MXene, especially Ti3C2Tx, is attracting extensive attention as an absorbing material owing to its strong dielectric loss and tunable structure. Nevertheless, extremely high conductivity and non-magnetic loss mechanism limit the absorbing intensity and effective absorption bandwidth (EAB). Herein, the magnetic ZnFe2O4 nanoparticles decorated Ti3C2Tx MXene composite is designed and synthesized by using a facile in-situ solvothermal method. The novel ZnFe2O4@Ti3C2Tx-2 (1:2) composite shows an optimal reflection loss of −60.94 dB and a wide EAB of 6.08 GHz at a matching thickness of only 1.75 mm. The mechanism analysis reveals that the synergetic electromagnetic loss effect, interfacial polarization, dipole polarization, and laminated structure contribute to improving the microwave absorption (MA) performance. Furthermore, to confirm the use capability of the ZnFe2O4@Ti3C2Tx sample coatings in practical applications, the radar cross-section (RCS) reduction performance has been proved through using computer simulation technology (CST). With the detection theta of 0°, the ZnFe2O4@Ti3C2Tx-2 sample coating possesses the largest RCS reduction value of 22.83 dB. This work lays the foundation for the rational design of high-performance absorbing materials.

The effects of Co2O3 addition on the electromagnetic properties of NiCuZn ferrite were investigated, by considering the variation of complex permeability, complex permittivity and quasi-microwave absorption property in the 1–1000 MHz frequency range. Results show that the introduction of Co3+ ions in NiCuZn ferrite leads to the marked shifting of magnetic resonance towards high-frequency and a slight increase of the permittivity. These Co-related effects enhance the maximum reflection loss in NiCuZn ferrite to reach −55.1 dB with its absorption bandwidth being tunable in the frequency range 480–1000 MHz, which provides a potential absorber for the anti-electromagnetic interference applications in electronic industry.

In this paper, we investigated the effect of magnetic grain size on magnetoelectric responses of particulate magnetoelectric 0.7(Bi 0.5 Na 0.5 TiO 3 -Bi 0.5 K 0.5 TiO 3 )−0.3(Ni 0.8 Zn 0.2 )Fe 2 O 4 (BNKT-NZFO) composites. The coexistence of two chemically separated phases was confirmed using x-ray diffraction analysis. The composites had homogeneous microstructure with controlled grain size. The magnetoelectric response of the BNKT-NZFO composites sensitively depended on the grain size of the NZFO phase and the magnetoelectric voltage coefficients presented a marked enhancement of 33% in the engineered grain size range. This result indicated that tailoring the magnetic grain size physically will provide a powerful mean of enhancing magnetoelectric coupling in a two-phase particulate composite, with large potential application in area of magnetic field sensor.

Biphase particulate magnetoelectric ceramics (1-x)Bi0.5Na0.5TiO3-xLa0.67Sr0.33MnO3 (x = 0.05, 0.15, 0.25 and 0.35) were prepared using the powder-in-sol precursor hybrid method. Effect of magnetic field on polarization response in composites was studied, by analyzing the magnetodielectric effect and ferroelectric loops under the applied magnetic field. The switching of magnetodielectric effect and the variation ferroelectric polarization is mainly determined by the competitive mechanisms of magnetoresistance and magnetostriction. Furthermore, the direct magnetoelectric output was carried out and the maximum ME voltage coefficient reached up to 19.1 mV/cm·Oe for the x = 0.15 composite.

Artificial multiferroics magnetoelectric (ME) polymer composite films exhibiting collective ferroelectric and magnetic orderings are gaining attractive for the use of flexible ME devices. Herein an anisotropic polymer-based ME composites films is developed, composed of magnetically oriented polycrystalline iron fiber (Fef) and poly(vinylidene fluoride-co-trifluoroethylene) P(VDF–TrFE). The structure, ferroelectric, piezoelectric, magnetic, and ME properties was systematically investigated. Both Fef fillers content and magnetic field direction determined the ME voltage coefficient, magnetical polarization and dielectric response in anisotropic P(VDF-TrFE)–Fef composites. Specifically, the composite with 16% filler loading delivers a peak ME value of 44.5 mV·cm−1·Oe−1 with magnetic field exerted along the fiber axial alignment direction. Such extracted results may encourage a way to optimize flexible composite in anisotropic contactless sensing and detecting applications.

Magnetic nitrogen-doped carbon nanotubes have been recognized as promising microstructures for electromagnetic wave absorption, benefiting from the internal hollow structure, excellent electrical conductivity and easy functionalization. Herein, a new composite composed of the thin-wall carbon nanotubes coated with the cobalt nanoparticles (hereafter labelled as: Co@NCNTs) on the tip was designed and synthesized through high temperature pyrolysis process. Revealed by scanning electron microscopy and X-ray photoelectron spectroscopy, the geometric and electronic structures of product were susceptible to the carbonization temperature. With the multiple dielectric polarization relaxations, higher magnetism and good impedance matching, the flammulina velutipes-like Co@NCNTs-700 exhibited the strongest dielectric loss, magnetic loss and electromagnetic wave absorption performance. The minimum reflection loss value and effective absorption bandwidth was determined to be −21.0 dB at 4.96 GHz and 5.28 GHz, respectively, superior to the previous reports. Furthermore, the thickness is at 2 mm and the filler mass loading is only 10%. Therefore, our present Co@NCNTs materials will be an ultralight material as potential high-efficiency EMW absorber.

Particulate magnetoelectric (ME) ceramics constituted by (1-x)(80Bi0.5Na0.5TiO3-20Bi0.5K0.5TiO3)-xCoFe2O4 [(1-x)BNKT-xCFO] (x = 0, 0.1, 0.2, 0.3, 0.4 and 1.0) were synthesized by an powder-in-sol precursor hybrid processing method and their structure, magnetic, ferroelectric, magnetodielectric (MD) and ME properties have been investigated. Results showed that the ceramics consisted of only two chemically separated phases and had homogeneous microstructure. The introduction of CFO into BNKT matrix led to the weakening of ferroelectric and dielectric properties whereas the strengthening magnetic and MD properties. The observation of the MD effect revealed the evidence of the strain-induced ME coupling and the MD value is well scaled with M2. A maximum value of ME output of 25.07 mV/cm·Oe was achieved for the 0.7BNKT-0.3CFO composite. The improved ME response together with the linear MD effect makes the ceramics promise for use in magnetic field controllable devices or magneto-electric transducers.

The magnetic insulator Fe 3 O 4 -modified flaky Fe 85 Si 9.5 Al 5.5 (FeSiAl) powders with significantly enhanced electromagnetic wave absorption properties in the frequency range of 2–8 GHz were prepared by chemical co-precipitation. X-ray diffraction (XRD) and scanning electron microscopy (SEM) have confirmed the formation of nanoparticles Fe 3 O 4 precipitated on the flake-shaped FeSiAl. The electromagnetic measurements of the modified flakes presents a nearly invariable complex permeability and decreased complex permittivity in the 2–8 GHz, as well as improved impedance matching performance. More importantly, an excellent microwave absorbing performance with the bandwidth (RL

The single-phase Bi 1- x Nd x FeO 3 ( x =0, 0.05, 0.10, 0.15, 0.20) were synthesized by the sol-gel method. Their crystal structure and microwave electromagnetic property in the frequency range of 2–18 GHz were investigated. The XRD patterns and Raman spectra showed that structural transition from rhombohedral ( x =0, 0.05, 0.1) to triclinic ( x =0.15) and tetragonal structure ( x =0.20) appeared in the Bi 1- x Nd x FeO 3 . Electromagnetic measurement suggested that both microwave permeability μ′ and magnetic loss tanδ m increased remarkably over 2–18 GHz by doping Nd. Strong dielectric loss peak was observed on the samples of Bi 1- x Nd x FeO 3 ( x =0.15) and Bi 1- x Nd x FeO 3 ( x =0.2). Results show that Nd substitution is an effective way to push BiFeO 3 to become microwave absorbing materials with high performance.

Surface functionalization on novel transition metal carbides Ti3C2 MXene has been demonstrated to be effective strategy to broaden potential application. Herein, the effect of surface decoration of transition magnetic metals (Fe-, Co-, Ni-) on the electronic structure and optical properties of Ti3C2 MXene is studied using first principle calculations. Energy band structures and corresponding density of electronic states investigations have shown that interlamellar spacing between Ti-layer and C-layer, as well as specific surface area, is inclined to expand after surface decoration. Besides, obvious peaks of d orbit have been observed, and demonstrated to play a dominant role in electronic states in Fe-, Co-, Ni–Ti3C2 composite. More importantly, surface decoration of transition magnetic metal Fe-, Co-, and Ni-could greatly promote optical absorption coefficient of Ti3C2 nanomaterials, covering ultraviolet region, visible region and infrared region. The increment rate reaches 50% within visible and ultraviolet region for Ni–Ti3C2 composite, while the increment rate of Fe-substituted Ti3C2 exhibits even greater than 100%. The remarkable enhanced optical absorbing properties over wide spectral region may be associated with interlamellar space expansion accompanied with more active sites and increased electronic mobility. All these findings are considered to broaden practical application of low-dimensional Ti3C2 nanomaterial towards photoelectric devices.

The cost-effective copper (Cu) nanoparticles and core/shell derived architectures with novel physicochemical properties have received tremendous attention in recent years. Herein, the effect of nanoparticle geometry (including diameter and core/shell ratio) on optical scattering and absorption of Cu@C core/shell nanoparticles has been investigated through a combination of DDA-based simulation and experimental validation. Simulated results have shown that the localized surface plasmon resonance (LSPR) peaks of Cu@C core-shell nanoparticles present slightly blue-shift with the increase of core/shell ratio, the core/shell ratio play the dominant role in the shift of the LSPR peak. Moreover, scattering efficiencies factors are inclined to be increasing faster with particle size and core/shell ratio increase, corresponding to enhanced surface electric field intensity which originated from excessive electron concentration on the interface between Cu core and C shell. Finally, experimental optical absorption performance has been performed with the aim at confirmation of size-sensitive light scattering behaviors of Cu@C core-shell nanoparticles via metal organic chemical vapor deposition technology. Results have found that the light absorption coefficient of up to 99.4% could be achieved for nanoparticles with an average particle diameter of 10 nm, while 98.9% for 23 nm. Further decrease in diameter on the nanometer scale is demonstrated to promote optical absorption to a certain extent, which agrees well with simulated results. All these findings have demonstrated ultra-small Cu@C core-shell nanoparticle to be a promising candidate for efficient optical absorption, and are beneficial for design and development of Cu@C core-shell nanoparticles enabled optical-based devices.

An optically transparent metamaterial absorber (MMA) operated in the C-band (4–8 GHz) is optimally designed based on the second-order cross fractal structure. The experimental results show that the reflection loss of the proposed MMA is lower than −10 dB from 3.98 GHz to 8.68 GHz. Two overlapped resonances located at 4.77 GHz and 7.33 GHz, respectively, are caused by the second-order cross fractal structure. Distributions of surface current, electromagnetic field and power loss density are investigated to illustrate the absorptive characteristics and electromagnetic loss mechanisms of the proposed MMA. Moreover, the average optical transmittance of the MMA is close to 75% from 390 nm to 780 nm. The MMA possesses simultaneously strong absorptive capacity in the C-band and high transmittance in the visible light range, showing potential application in special environment.

In this paper, pixel circuit using mirroring structure with Indium-Gallium-Zinc oxide (IGZO) thin film transistors (TFTs) for active matrix organic light emitting diode (AMOLED) display is proposed. This pixel circuit consists of only four TFTs, and one capacitor. Due to the mirroring structure, characteristic of the driving TFT can be precisely sensed by the sensing TFT, which is deployed in a discharging path for gate electrode of the driving TFT. This discharging process is strongly dependent on threshold voltage (VT) and effective mobility of the sensing TFT. Circuit operating details are discussed, and compensation effects for threshold voltage shift and mobility variations are verified through numerical derivation and SPICE simulations. Furthermore, compared with conventional schematics, the proposed pixel circuit might have much simplified external driving circuits, and it is a promising alternative solution of high performance AMOLED display.

La 1− x Ag x MnO 3 perovskites with different doping Ag-content were prepared by the sol–gel method. The electromagnetic characteristics and microwave loss behavior of these ion-doped rare-earth manganites were studied in the 2–18 GHz frequency range. The microstructure and morphology of the samples were characterized by X-ray diffraction (XRD), and scanning electron microscopy (SEM) techniques. The complex permittivity spectra, the complex permeability spectra and microwave reflection loss were measured by a microwave vector network analyzer system. The XRD patterns show that the crystalline perovskite main phase ABO 3 is formed and impurity phases disappear when calcined at 1100 °C, and Ag metal as an impurity phase appears when excessive Ag + is doped. The SEM image indicates that many of the La 0.85 Ag 0.15 MnO 3 particles are fiber-like or ellipsoidal. Magnetic loss and dielectric loss coexist and cooperate in microwave attenuation by moderate substitution of Ag + for La 3+ . The microwave absorption property of the La 0.85 Ag 0.15 MnO 3 sample is enhanced with the bandwidth below −10 dB at about 6 GHz and the peak value of reflection loss is near −25.0 dB at the layer thickness of 2 mm.

W-type barium hexaferrites with compositions of Ba 1 Co 0.9 Zn 1.1 Fe 16 O 27 and Ba 0.8 La 0.2 Co 0.9 Zn 1.1 Fe 16 O 27 were synthesized by the sol–gel method. The electromagnetic properties and microwave absorption behavior of these two ferrites were studied in the 2–18 GHz frequency range. The microstructure and morphology of the ferrites were characterized by X-ray diffraction (XRD), and scanning electron microscopy (SEM) techniques. The complex permittivity spectra, the complex permeability spectra and microwave reflection loss were measured by a microwave vector network analyzer. The XRD patterns show that the main phase of the Co 2 W ferrite forms without other intermediate phases when calcined at 1200 °C. The SEM images indicate that flake-like hexagonal crystals distribute uniformly in the materials. Both the magnetic and dielectric losses are significantly enhanced by partial substitution of La 3+ for Ba 2+ in the W-type barium hexaferrites. The microwave absorption property of the La 3+ doping W-type hexaferrite sample is enhanced with the bandwidth below −10 dB around 8 GHz and the peak value of reflection loss about −39.6 dB at the layer thickness of 2 mm.