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The development of devices for the in situ resource utilization (ISRU) of lunar surface powder (regolith) by means of microwaves needs regolith simulants with electromagnetic properties similar to the lunar regolith. This document deals with the measurement of complex permittivity and dielectric loss tangent of the aforementioned simulants at ambient temperature from 400 MHz to 20 GHz, performing measurements using two lunar dust simulants, EAC-1A and JSC-2A, resulting, on the one hand, in permittivity values of ε ′ = − 0.0432 f + 4.0397 for the EAC-1A lunar dust simulant and ε ′ = − 0.0432 f + 4.0397 for the JSC-2A simulant, and on the other hand, in loss tangent values of t a n δ e = − 0.0015 f + 0.0659 for the EAC-1A powder and t a n δ e = − 0.0039 f + 0.1429 for the JSC-2A powder. In addition, further studies are carried out taking into account the humidity of the samples and their densities at room temperature. The obtained results are applicable for comparing the measured values of EAC-1A and JSC-2A between them and with other previously measured simulants and real samples. The measurements are carried out by applying two different nonresonant techniques: Open-Ended Coaxial Probe (OECP) and transmission line. For this purpose, the DAK and EpsiMu commercial kits are used, respectively. [ABSTRACT FROM AUTHOR]

The analysis of the magnetic properties of alloys with low Curie temperature used in domestic induction heating is presented. These alloys allow the development of cookware with additional benefits with respect to regular cookware oriented to improve temperature control and the user's safety. Firstly, an experimental method to characterize the magnetic permeability with respect to the magnetic field strength and temperature in the material is presented. Secondly, a finite element simulation method is proposed which, considering the previous characterization, allows the calculation of the electrical equivalent of an inductor-load system as a function of temperature and magnetic field. This method makes possible the application of finite element simulation in the frequency domain with nonlinear materials, which is of interest for the design of electronics associated with domestic applications of induction heating. Simulation results are experimentally verified with various ferromagnetic alloys with low Curie temperature at different power, temperature, and operating frequency ranges. [ABSTRACT FROM AUTHOR]

The tendency over the last decades in the aerospace industry is to substitute classic metallic materials with new composite materials such as carbon fiber composites (CFC), fiber glass, etc., as well as adding electronic devices to ensure the safety and proper platform operation. Due to this, to protect the aircraft against the Electromagnetic Environmental Effects (E3), it is mandatory to develop accurate electromagnetic (EM) characterization measurement systems to analyze the behavior of new materials and electronic components. In this article, several measurement methods are described to assess the EM behavior of the samples under test: microstrip transmission line for a surface current analysis, free space to obtain intrinsic features of the materials and shielding effectiveness (SE) approaches to figure out how well they isolate from EM fields. The results presented in this work show how the different facilities from the National Institute of Aerospace Technology (INTA) are suitable for such purposes, being capable of measuring a wide variety of materials, depending on the type of test to be carried out. [ABSTRACT FROM AUTHOR]

The growth of the application of electronic devices has created a new form of pollution known as noise or radio frequency interference, electromagnetic radiation, or electromagnetic interference (EMI), which results in the malfunction of equipment. A new carbon-based polymer composite has been unlocked through the discovery of polymer composites. Carbon nanotubes (CNTs) have shown potential as reinforcement fillers in polymer to enhance an EMI shielding material owing to their large specific surface area, well-defined 3D networking structure, and unique electronic structure. The main focus of this review is the role of CNT as fillers in intrinsic conducting polymer and conducting polymer composite. The factors that influence EMI shielding performance are also included in this review. The roles of the size; shape; and electronic, mechanical, and chemical properties of nanomaterials in tuning the EMI shielding effectiveness of polymer hybrid are emphasized. The structural design of CNT polymer composite has been reviewed as well. Future research direction has been proposed to overcome the current technological limitations and realize the most advanced EMI shielding materials for future use. The composites have a potential to replace traditional shielding materials owing to their advantageous properties.

We propose a simple and accurate microwave extraction procedure for full electromagnetic characterization of $\Omega $ -class bianisotropic metamaterial (MM) slabs from normal incidence scattering (S-) parameters using TE1, TE2, and TE3 modes. Its closed-form nature (no need for any numerical analysis and optimization toolbox) and less requirement (a total of seven S-parameters) demonstrate the advantage of our method over other methods in the literature. Our approach was validated and its accuracy was verified by S-parameters, through a full electromagnetic simulation program—CST Microwave Studio, of an edge-coupled $\Omega $ -class split-ring-resonator MM slab. [ABSTRACT FROM AUTHOR]

In this paper, a new measurement method is proposed to estimate simultaneously the complex permittivity and the complex permeability for a magneto-dielectric sample, which may contain several layers, using a X-band rectangular waveguide WR90. The Sij-parameters at the reference planes in the rectangular waveguide loaded by a material sample are measured as a function of frequency using the E8634A Vector Network Analyzer. Also, by applying the two-dimensional finite difference in time domain (2D-FDTD), the expressions for these parameters as a function of complex permittivity and complex permeability are calculated even if the sample do not cover all the section of the waveguide. The Nelder-Mead algorithm is then used to estimate the complex permittivity and complex permeability by matching the measured and calculated Sijparameters. This method has been validated by estimating, at the X-band, the complex permittivity and complex permeability of two materials such as FR4 Epoxy and Titanium Carbide powder (TiC). [ABSTRACT FROM AUTHOR]

This paper deals with near magnetic field characterization of power electronic modules. The purpose is to relate near-field (NF) measurement to switching behavioral characteristics. An elementary magnetic sensor is presented and its characterization is detailed. Isolated antenna simulations are computed, thanks to an equivalent lumped parameter model of the antenna. Experimental characterizations are also provided to be compared to simulations. Following that, the characterized antenna is integrated into a specific power electronic device. NF measurements allow us to compute magnetic field mappings of the device under test. Time and frequency analyses of the sensor output data are discussed based on current measurements and magnetic simulation of the power electronic device. Finally, NF measurement enables access to switching details, disturbance propagation paths, and radiation distribution of a power electronic module. [ABSTRACT FROM AUTHOR]

• Nanoparticles (NPs) and electromagnetic design, modelling and simulation for drug delivery (DD) in nanomedicine. • New IEEE IMS TC34 "Nanotechnology in Instrumentation and Measurements" guidelines for in vitro characterization of NPS-DD. • Workflow describing the main steps of the measurement guidelines. • Image processing approaches supporting NPS characterization. Nanomedicine, in particular the use nanoparticles for drug delivery (DD), is an increasing field of development and advancement. The influence and the interference of magnetic field about delivery action is an important field of investigation. Vaccines and specific drugs for known and rare pathologies can get benefits from this approach. The main goal of the work is to provide a modelling that can support the know-how of the impact of a magnetic field about the delivery of drug allocated on Nanoparticles (NPs), thus defining guidelines to measure the delivery function for generic biocompatible NPs. In particular, by means of Finite Element Method (FEM) approach, the impact magnetic field, on gold nanoparticle (GN), used in nanomedicine for DD process, is analysed to facilitate the knowledge of the delivery mechanisms. The study is addressed to the estimation of the magnetic field distribution on the GNs interface, supporting the efficacy of the magnetic field stimulation. The paper is concluded by discussing measurement approaches useful to define guidelines. The main goal of the paper is to provide a methodology to understand DD phenomena in nanotechnology using a magnetic field as stimuli, by defining at the same time tools and approaches tailoring a measurement protocol in nanotechnology. [ABSTRACT FROM AUTHOR]

The temporal transmission properties of an N-layer structure under planar wave incidence are investigated by the method of subregions via the wave matrix approach. The transmission coefficient expression is first expressed in the frequency-domain by reduced transmission coefficients and then transformed into the time domain, which includes unit step functions with different effective time periods and weightings. The analysis is validated by numerical computations and three-dimensional electromagnetic simulations at gigahertz frequencies. [ABSTRACT FROM AUTHOR]

Abstract The nickel-carbon nanofibers (Ni-C NFs) were fabricated by the electrospinning of poly(vinyl alcohol) (PVA) and nickel acetate tetrahydrate (NiAc) solution precursor with succedent PVA pyrolyzation and calcination process. The microwave absorption performance and electromagnetic (EM) parameters of the NFs were researched over the frequency range of 2.0–18.0 GHz. Both the impedance matching and EM wave absorption properties of the Ni-C NFs were improved by changing the carbonization temperature. The effect of graphitization degree on reflection loss (RL) and the possible loss mechanisms were directly displayed in the comparative study of each sample. The optimal RL value of − 44.9 dB and an effective frequency bandwidth of 3.0 GHz under a thickness of 3.0 mm can be reached by a sample calcined at 650 °C. These lightweight Ni-C NFs composites can be promising candidates for EM wave absorbers due to the combination of multiple loss mechanisms, nano-size effect and good impedance matching between Ni nanoparticles and CNFs. [ABSTRACT FROM AUTHOR]

The electromagnetic performance of aerial platforms, which are composed mostly of nonmetallic materials, is a subject of great interest at present time. The behavior of this type of composite structure against electromagnetic environmental effects (E3), such as lightning, is not well-studied as in the case of metalic structures. The purpose of this article is to characterize the joints present in aerial platforms constructed mainly of nonmetallic composite materials. The study of these joints is fundamental because electrical discontinuities or preferential routes can produce changes in the electromagnetic behavior of an aircraft. The proposed measurement system for the characterization of these joints is a microstrip line. The flexibility of the test setup allows for evaluation of different joints in carbon fiber composite (CFC) samples with a different number of plies. Additionally, approximated models of the behavior of the joints as well as the detection of possible defects in the joining process are reported.

Electromagnetic absorption materials have drawn increasing attention owing to their wide applications in military, aerospace, communication and the electronic industry. Efficient microwave absorption with tunable bandwidth and thermal stability is a great challenge. Herein, we fabricate a novel 3D hierarchical Co 3 O 4 -rGO hybrid-architecture by a facile, green and highly tunable strategy. The porous Co 3 O 4 flower is assembled uniformly, introducing great amount of interfaces. Tailoring Co 3 O 4 flowers could improve interfacial polarization and dipole polarization as well as conductive network, highly tuning the hybrid-architectures and electromagnetic properties. The reflection loss (RL) reaches −61 dB at Co 3 O 4 /rGO ratio of 2:1, as well as frequency-selective absorption. Furthermore, the RL are relatively stable and the bandwidth is broadened almost covering the whole investigated frequency at elevated temperature of 353–473 K. The result is ascribed to utilizing multi-interface magnetic micro-flowers to tune impedance matching, which is accompanied with strong relaxation loss and electrical loss, as well as magnetic loss. Our work confirms that 3D hierarchical Co 3 O 4 -rGO hybrids as a potential candidate for high-efficiency microwave absorbers in harsh environment, and provide a novel pathway for designing microwave absorber in the future. [ABSTRACT FROM AUTHOR]

Multi-frequency measurement of a dispersive electromagnetic (EM) property, such as electrical conductivity, dielectric permittivity, or magnetic permeability, is commonly analyzed for purposes of material characterization. Such an analysis requires inversion of the multi-frequency measurement based on a specific relaxation model, such as Cole-Cole model or Pelton's model. We develop a unified inversion scheme that can be coupled to various type of relaxation models to independently process multi-frequency measurement of varied EM properties for purposes of improved EM-based geomaterial characterization. The proposed inversion scheme is firstly tested in few synthetic cases in which different relaxation models are coupled into the inversion scheme and then applied to multi-frequency complex conductivity, complex resistivity, complex permittivity, and complex impedance measurements. The method estimates up to seven relaxation-model parameters exhibiting convergence and accuracy for random initializations of the relaxation-model parameters within up to 3-orders of magnitude variation around the true parameter values. The proposed inversion method implements a bounded Levenberg algorithm with tuning initial values of damping parameter and its iterative adjustment factor, which are fixed in all the cases shown in this paper and irrespective of the type of measured EM property and the type of relaxation model. Notably, jump-out step and jump-back-in step are implemented as automated methods in the inversion scheme to prevent the inversion from getting trapped around local minima and to honor physical bounds of model parameters. The proposed inversion scheme can be easily used to process various types of EM measurements without major changes to the inversion scheme. [ABSTRACT FROM AUTHOR]

Radar Absorbing Materials (RAM) are compounds that absorb incidental electromagnetic radiation in tuned frequencies and dissipate it as heat. Its preparation involves the adequate processing of polymeric matrices filled with compounds that act as radar absorbing centers in the microwave range. This work shows the electromagnetic evaluation of RAM based on CoTi and La doped Ca hexaferrite. Vibrating Sample Magnetization analyses show that ion substitution promoted low values for the parameters of saturation magnetization (123.65 Am2/kg) and coercive field (0.07 T) indicating ferrite softening. RAM samples obtained using different hexaferrite concentrations (40-80 per cent, w/w) show variations in complex permeability and permittivity parameters and also in the performance of incidental radiation attenuation. Microwave attenuation values between 40 and 98 per cent were obtained.

We present a general methodology for electromagnetic homogenization and characterization of bianisotropic metasurfaces formed by regular or random arrangements of small arbitrary inclusions at interfaces of two different isotropic media. The approach unites and generalizes the earlier theories developed independently by two joint research groups: that of profs. Holloway and Kuester and that of profs. Simovski and Tretyakov. We analyze the features of both formalisms and discuss their peculiarities in several example cases. Our theory can be used in the analysis and synthesis of a wide spectrum of metasurfaces. [ABSTRACT FROM AUTHOR]

A new method for corrosion monitoring based on the change of the radiofrequency (RF) wave propagation in a microstrip line during its corrosion is presented. For that purpose, the microstrip line is produced in the same metal as the mechanical structure under monitoring. Zinc material is considered in the study since it allows an investigation of uniform as well as localized corrosion when chloride is used. Experimental data and simulations results provide fundamental basis on the sensing mechanisms of the method and evidence the possibility to detect the created corrosion species and to distinguish between localized and uniform corrosion processes. As the consequence, the proposed method should be considered as promising and reliable tool for corrosion monitoring of several materials exposed to various environments. [ABSTRACT FROM AUTHOR]

In order to develop a fast, sensitive and easy-to-produce biosensor, a high-quality microwave split-ring resonator is going to be developed. In the final sensing device, a blood sample will be placed as a droplet on the sensitive area of the sensor. In case of specific target biomolecules binding a shift in resonance frequency will be induced due to the effective permittivity change. This shift in resonance frequency depends on the concentration of biomolecules and is therefore quantitative. The aim of this work is to find a position for the bio-functionalization that providesa measurable frequency shift when the analyte is added. Different areas are tested experimentally and via simulations. Two buffer solutions are used which have to be characterized in terms of its electromagnetic properties in advance. This preliminary study should pave the way for the measurements in real human samples such as serum or plasma.

This paper presents a detailed study about the characterization of electromagnetic near-fields emitted from power electronic circuits. The approach proposed here provides a radiation model, which verifies the uniqueness of the solution using an inverse problem-based resolution method. For this purpose, the characterization method has been combined with an experimental mapping realized at the switching time scale. This mapping is based on a Fourier analysis applied on the measurements acquired from the device under study. It allowed us to trace a prior radiations map over the device under study. This radiation map is then exploited in order to validate the uniqueness of the final result, a result that has been obtained by solving the inverse problem using a genetic algorithm (GA) to optimize the highly nonlinear fitness function. The precision and the accuracy of the method have been validated by the superposition of the obtained radiation models over the circuit topology. The correlation between the sources parameters (position, orientation, geometrical parameters and currents) and the parameters corresponding to the components located at the regions defined by the radiation map has been successfully performed. This allowed us to confirm that the physical reality is respected, and to assume that we have reached the uniqueness of the solution. [ABSTRACT FROM PUBLISHER]

The electromagnetic properties of carbon nanotube powder reinforced concretes are numerically and experimentally characterized. This typology of composite material is built by following the simple procedure usually adopted for the on-site concrete production. The dielectric parameters are investigated by means of waveguide measurements in the frequency band 0.75-1.12 GHz that is currently exploited in mobile phone radio access networks. The obtained results are used to compute the electromagnetic shielding effectiveness of large wall-shaped concrete structures. A shielding effectiveness up to 50 dB is obtained for a 15 cm thick wall when the carbon nanotube inclusion is raised up to 3 wt%. [ABSTRACT FROM AUTHOR]

Abstract: Knowing the electromagnetic characteristics of different materials has become a major topic with the growing of wireless communications. The actual tools to perform this characterization have some limits, either in terms of limited frequency band, or in terms of inconstancy according to the different kinds of materials. On the basis of well-known procedures in the microwave domain, we present a new measurement cell equipped with a sample holder that can contain any kind of materials: solids, semi-solids (granular or powder materials), liquids. This technique can also characterize materials of thin thickness that are also more and more used in the RFID domain or in the realization of antennas on flexible substrates. [Copyright &y& Elsevier]

The electromagnetic characterization method based on the state space approach, which has been proposed for parameter retrieval of uniaxial chiral composites is extended in order to extract the electromagnetic parameters of biaxial bianisotropic media as well. The properties of state transition matrix of a biaxial bianisotropic layer are presented as two theorems, and the formulation of the proposed electromagnetic characterization method is then provided. The proposed approach reduces nonlinearity and complexity of the problem by considering properties of the state transition matrix. The validity of the method is verified using analysis of a bianisotropic specimen. The results show that the proposed technique allows for a characterization at oblique incidences. [ABSTRACT FROM PUBLISHER]

Radar Absorbing Materials (RAM) are compounds that absorb incidental electromagnetic radiation in tuned frequencies and dissipate it as heat. Its preparation involves the adequate processing of polymeric matrices filled with compounds that act as radar absorbing centers in the microwave range. This work shows the electromagnetic evaluation of RAM based on CoTi and La doped Ca hexaferrite. Vibrating Sample Magnetization analyses show that ion substitution promoted low values for the parameters of saturation magnetization (123.65 Am²/kg) and coercive field (0.07 T) indicating ferrite softening. RAM samples obtained using different hexaferrite concentrations (40-80 per cent, w/w) show variations in complex permeability and permittivity parameters and also in the performance of incidental radiation attenuation. Microwave attenuation values between 40 and 98 per cent were obtained.

Highlights: [•] Analytical solution for eccentrically placed line current problem. [•] Investigation of electromagnetic fields inside a multilayered cylinder load. [•] Characterization of RF E, B 1, fields and SAR, from low to ultra high field MR. [•] Separation of the primordial solution and the composite one. [•] Characterization of dielectric resonance, standing wave, multi-source interference. [ABSTRACT FROM AUTHOR]

Abstract: In this paper we present a macroscopic model of a metasurface—optically dense grids of resonant scatterers located on a refracting interface. Similar models were previously built for the case when the scatterers are non-resonant electric dipoles and for the case when there is no substrate. In the present case scatterers are resonant, can have magnetic response, and for substrates with large refraction index acquire also substrate-induced bianisotropic properties. Representing the homogenized response of a metasurface to incident electric and magnetic fields through surface susceptibilities we derive the reflection and transmission formulas for semi-infinite and finite-thickness substrates. We develop a robust algorithm of the retrieval of the characteristic surface parameters from the reflection and transmission coefficients measured or exactly calculated for three different incidence angles. With numerical examples we show that the retrieved susceptibilities of metasurfaces are independent on the incidence angle and can be really called characteristic parameters. [Copyright &y& Elsevier]

We propose a novel algorithm based on the matrix pencil method to estimate the parameters of a class of signals modeled as damped power-law phase signals. This class arises primarily from the electromagnetic probing of dispersive geological and civil engineering materials as a consequence of the universal dielectric response. When stratified media are considered, direct application of conventional matrix-shifting methods is hindered not only by the nonlinear frequency dependency which destroys the desired shift-invariance property of the data matrix, but also by the stratified structure of the medium which introduces a cumulative effect. In this regard, the proposed algorithm restores recursively the Vandermonde structure of one mode vector at a time by means of a spline-interpolation technique and then orthogonally projects it to filter out its contribution before passing to another. The algorithm is tested on simulated and experimental data resulting from the probing of a stratified dispersive medium, and its performance is assessed against the Cramér-Rao lower bound. For the example of experimental data, collected from concrete cores by means of a cylindrical transition line, the permittivities at the reference frequency and the dispersion indices are determined using the new algorithm and compared with those of a nonlinear optimization scheme. [ABSTRACT FROM PUBLISHER]

Abstract: In this paper we discuss effective material parameter description of new nanostructures designed to perform as artificial magnetic materials for visible light. Among these structures there are various split-ring resonators, dual-bar structures, fishnet layers and other geometries. Artificial magnetic response in these structures appears due to weak spatial dispersion effects, and it is important to study the conditions under which the magnetic response can be adequately measured with effective permeability tensor. On the examples of dual bars and split rings we show that this is possible only under some quite restrictive conditions. In the general case, more complicated constitutive relations with more effective material parameters need to be developed. [ABSTRACT FROM AUTHOR]

The emergence of wearable antennas to be integrated into garments has revealed the need for a careful electromagnetic characterization of textile materials. Therefore, we propose in this paper a new matrix-pencil two-line method that removes perturbations in the calculated effective permittivity and loss tangent which are caused by imperfect deembedding and inhomogeneities of the textile microstrip line structure. The approach has been rigorously validated for high-frequency laminates by comparing measured and simulated data for the resonance frequency of antennas designed using the calculated parameters. The method has been successfully applied to characterize the permittivity and loss tangent of a variety of textile materials and up to a frequency of 10 GHz. Furthermore it is shown that the use of electrotextiles in antenna design influences the effective substrate permittivity. [ABSTRACT FROM PUBLISHER]

Abstract: The load assembly of RFX-mod consists of three toroidal conducting structures whose eddy currents affect the plasma equilibrium magnetic configuration. The high number of electromagnetic probes mounted on the components of the load assembly allowed to analyse the response of each structure to a variation of the magnetic field vertical component. The capability of evaluating the axisymmetric toroidal currents in the passive structures and therefore their contribution to the equilibrium configuration by a 2D FE MHD equilibrium code was validated. The design and implementation of a feedback control system of the magnetic field vertical component before the gas ionization allowed meeting the requirement of an accurate control of this quantity in view of operation at higher plasma current and independently of the magnetizing winding programming. [Copyright &y& Elsevier]

Abstract: During the last year different saddle coil set-ups were tested on EXTRAP T2R performing experiments of plasma MHD modes active control. In particular, a series of shots both without and with plasma were aimed at the electromagnetic characterization of the open loop system and to the validation of a model developed for the design of a digital control system. A very good agreement was observed between model and experiment both in terms of single coil electromagnetic parameters and in terms of harmonic distribution at different frequencies. The quality of the harmonic content as a function of the number of active coils was also analysed. Finally, encouraging results were obtained comparing theoretical and experimental growth rates of unstable modes after applying static perturbations of different toroidal order n. [Copyright &y& Elsevier]

Under the assumptions of weak magnetic fields and temperatures well below the critical temperature of the superconductors, the propagation characteristics of a set of N coupled superconducting strips are calculated using an integral equation approach. The proposed theory provides accurate results of frequencies up to a few GHz. Magnetic field calculations allow us to predict acceptable values for the currents in the strips. Comparison with the propagation characteristics of aluminum strips demonstrates the major advantages of superconducting transmission lines, namely, negligible losses and dispersion, and higher phase velocities. Such properties are highly desirable in the engineering of fast interconnects for modern high-speed integrated circuits. [ABSTRACT FROM AUTHOR]

Electromagnetic (EM) characterization of metamaterials and metasurfaces is crucial for theoretical modeling and also efficient design of state-of-the-art applications. Thus far, the widely used parameter retrieval methods have been provided unphysical artifacts in modeling of metasurfaces. In this work, we develop a new parameter retrieval method which is based on dipole approximation and Ewald lattice summation. This technique can be used to efficiently characterize metasurfaces that support simultaneous electric and magnetic dipole resonances, when illuminated by a plane-wave at an arbitrary angle of incidence. We retrieve the effective parameters of a high-index metasurface composed of silicon nanospheres and demonstrate that in contrast to the conventional methods, the proposed model successfully describes its optical responses. Based on our results, it is demonstrated that even in metasurfaces composed of isotropic structures, bianisotropic terms can be excited at oblique angles of incidence. The developed parameter retrieval method is much more efficient compared to conventional methods, and it is certainly useful in precise modeling and proper designing of even more complex optical metasurfaces. [ABSTRACT FROM AUTHOR]

The electromagnetic performance of aerial platforms, which are composed mostly of nonmetallic materials, is a subject of great interest at present time. The behavior of this type of composite structure against electromagnetic environmental effects (E3), such as lightning, is not well-studied as in the case of metalic structures. The purpose of this article is to characterize the joints present in aerial platforms constructed mainly of nonmetallic composite materials. The study of these joints is fundamental because electrical discontinuities or preferential routes can produce changes in the electromagnetic behavior of an aircraft. The proposed measurement system for the characterization of these joints is a microstrip line. The flexibility of the test setup allows for evaluation of different joints in carbon fiber composite (CFC) samples with a different number of plies. Additionally, approximated models of the behavior of the joints as well as the detection of possible defects in the joining process are reported. [ABSTRACT FROM AUTHOR]

To enhance microwave loss abilities, constructing composites with one-dimensional (1D) structure is an excellent scheme. In this work, a high-efficiency microwave absorber of MnO nanograins decorated vanadium nitride/carbon nanofibers (MnO-VN/C NFs) was successfully prepared for the first time via co-electrospinning technology and subsequent nitriding treatment. Studying in detail the specific relationship between nitriding time and the morphology of the as-prepared NFs, the precipitations of MnO nanoparticles with tailored structures were attached on the surface of VN/C NFs to optimize their electromagnetic parameters. When the nitriding time was 2.0 h at 600 °C, the MnO-VN/C NFs displayed good microwave absorption performances: the minimum reflection loss (RL) value was -63.2 dB at 8.8 GHz, and the bandwidth of RL < -10 dB was up to 6.4 GHz from 11.6 to 18 GHz at the thickness of 2.8 mm. Meanwhile, the absorption bandwidth (RL< -10 dB) could cover the whole X and Ku band by adjusting the thickness, respectively. The outstanding performances could be attributed to the good impedance matching and various loss pathways including conductive loss and interfacial and dipole polarizations. In these regards, MnO-VN/C NFs are likely to be utilized as a high-efficiency microwave absorber. And the strategy in this work can provide great help to design other 1D structural microwave absorbers with a broader absorbing band.