Field Shielding Research Articles

Durable electromagnetic interference (EMI) shielding ramie fabric with excellent flame retardancy and Self-healing performance

Although more and more attention has been paid to electromagnetic interference (EMI) shielding fabric materials due to increasing electromagnetic waves pollution, little attention to their fire safety behavior and durability in practical use. Herein, durable EMI shielding ramie fabric with flame retardant and self-healing performance were fabricated by depositing ammonium polyphosphate (APP)/polyethyleneimine (PEI) layer, MXene sheets and polycaprolactone (PCL) layer. The resultant multifunctional fabric could self-extinguish and the peak heat release rate (pHRR) value reduced about 74.3% for the modified ramie fabric that contains about 12 wt% of PEI/APP bilayer compared with pure ramie fabric. Furthermore, the ramie fabric coated by a increasing amount of MXene sheets changed from insulating to conductive, thus gradually improving their EMI shielding performance, which exhibit a high electrical conductivity of 900.56 S/m with an outstanding SE value of 35 dB at a 1.2 mg/cm2 content in the X-band. Besides, When the multifunctional fabric was cut off under external force, it could achieve self-healing and the EMI shielding performance can recover to 34 dB due to the low melting point and good fluidity of PCL. Thus, this multifunctional fabric holds great promise for wearable intelligent cloth, EMI shielding and other fields.

Effect of moisture content on the electromagnetic shielding ability of non-conductive textile structures

Electromagnetically shielding textile materials, especially in professional or ordinary clothing, are used to protect an implanted pacemaker in the body. Alternatively, traditional textiles are known for their non-conductivity and transparency to an electromagnetic field. The main goal of this work was to determine whether the high moisture content (sweat) of the traditional textile structure significantly affects the resulting ability of the material to shield the electromagnetic field. Specifically, whether sufficient wetting of the traditional textile material can increase its electrical conductivity to match the electrically conductive textiles determined for shielding of the electromagnetic field. In this study, cotton and polyester knitted fabric samples were used, and two liquid medias were applied to the samples to simulate human sweating. The experiment was designed to analyse the factors that have a significant effect on the shielding effectiveness that was measured according to ASTM D4935. The following factors have a significant effect on the electromagnetic shielding effectiveness of moisturised fabric: squeezing pressure, drying time and type of liquid media. Additionally, the increase of electromagnetic shielding was up to 1 dB at 1.5 GHz frequency at the highest level of artificial sweat moisturised sample.

Enhancing the electromagnetic interference shielding of flexible films with reduced graphene oxide-based coatings

Herein, it was investigated the development of a low-cost conductive coating for application in the field of Electromagnetic Interference shielding (EMI shielding). The coating was produced with reduced graphene oxide (rGO), considered an excellent technological alternative for graphene applications, and styrene-ethylene/butylene-styrene (SEBS) block copolymer. The rGO was obtained by reduction of graphene oxide (GO) using ascorbic acid as a “green” and efficient reducing agent, and Raman spectroscopy results indicated that the reduction of GO was successfully reached. Firstly, polymeric substrates were covered with coatings containing 2% (v/v) of rGO to evaluate the electrical conductivity and electromagnetic shielding effectiveness of transmission (SET). With the best SET value achieved, the block copolymer SEBS was added to the rGO coating to improve its adhesion over the substrate. Electrical conductivity and SET of these samples were measured by Impedance Spectroscopy and EMI Shielding analysis, with the later performed within the 10 GHz frequency band (X band), required for radar, telecommunication and military applications. With attenuation of the electromagnetic waves around 20 dB, this new route/technique can be used to improve the shielding effectiveness of flexible films by rGO coating, for wide range technological sectors.

Fabrication of multi-nanocavity and multi-reflection interface in rGO for enhanced EMI absorption and reduced EMI reflection

Through inserting SiO2@Au into the reduced graphene oxide (rGO) layers, the rGO-SiO2@Au composites were prepared via the vacuum-assisted electrostatic self-assembly method. The obtained composites exhibit excellent electromagnetic interference (EMI) shielding effectiveness due to the successful construction of multi-nanocavities (spherical SiO2 cavities and layered air cavities between rGO), multi-reflection interfaces (rGO and Au shell) and continuous conductive network (rGO-Au-rGO). Among them, the total shielding effectiveness (SET) of the composites with 75.78 wt% SiO2 and 19.38 wt% rGO can reach 38.4 dB at 18 GHz. Thereinto, the shielding effectiveness absorption (SEA) is 36.4 dB, 1.3 and 13.5 times higher than that of rGO and SiO2@Au. And the shielding effectiveness reflection (SER) is always below 5 dB from 1 to 18 GHz, much lower than that of rGO (about 15 dB). Further studies found that the SEA values were enhanced at 12.6 GHz and 6.2 GHz due to the construction of cavities and location of Au nanoparticles between the rGO layers. This study provides a simple and mild method to prepare high-performance thin-layered materials with applications in the field of EMI absorption shielding.

Simulation Study of Magnetic Shielding to Address Heat Generation in Rollers for Clamping Aluminum Rod Heated by HTS DC Induction Heater

The roller is the connect structure between the gripper and main or auxiliary gearbox, which rotates simultaneously with the aluminum billet. When preheating short aluminum billet, a part of the roller is in the air-gap, which will be heated during preheating the aluminum billet, and the increase in the temperature of the roller can affect the gearbox. To address the roller heat, a magnetic shielding method has been proposed. And the effect of the magnetic shielding of the magnetic field in the roller and the air-gap has been analyzed. The weakening effect of the magnetic shielding on the heating power also has been evaluated. At the same time, the electromagnetic force of the magnetic shielding is also been carried out. The results show that the magnetic shielding can effectively reduce the heating power of the roller. Evidently, adding a magnetic shielding around the roller is feasible to alleviate or solve the problem of roller and gripper heat.

Analysis of Shielding Performance of Radiation-Shielding Materials According to Particle Size and Clustering Effects

In the field of medical radiation shielding, there is an extensive body of research on process technologies for ecofriendly shielding materials that could replace lead. In particular, the particle size and arrangement of the shielding material when blended with a polymer material affect shielding performance. In this study, we observed how the particle size of the shielding material affects shielding performance. Performance and particle structure were observed for every shielding sheet, which were fabricated by mixing microparticles and nanoparticles with a polymer material using the same process. We observed that the smaller the particle size was, the higher both the clustering and shielding effects in the high-energy region. Thus, shielding performance can be improved. In the low-dose region, the effect of particle size on shielding performance was insignificant. Moreover, the shielding sheet in which nanoparticles and microsized particles were mixed showed similar performance to that of the shielding sheet containing only microsized particles. Findings indicate that, when fabricating a shielding sheet using a polymer material, the smaller the particles in the high-energy region are, the better the shielding performance is. However, in the low-energy region, the effect of the particles is insignificant.

A Comparative Study on the Phase Structure, Optical and NIR Reflectivity of BaFe<sub>12</sub>O<sub>19</sub> Nano-Pigments by the Traditional and Modified Polyacrylamide Gel Method

Barium hexaferrite (BaFe12O19) nano- pigment is a pigment with high near infrared reflection in the wavelength range of 1400-2500 nm. The BaFe12O19 nano- pigments were synthesized by the traditional and modified polyacrylamide gel method and characterized by thermogravimetric and differential scanning calorimetry (TG-DSC) analyses, X-ray powder diffraction (XRD), fourier transform infrared (FTIR), transmission electron microscopy (TEM), and UV-Visible spectrophotometer. The physicochemical properties of BaFe12O19 nanopigments are strongly dependent on the synthesis route. The introduction of carbon particles into the BaFe12O19 precursor accelerates the formation of BaFe12O19 phase, reduces its particle diameter and changes its color properties. The modified polyacrylamide gel method makes it possible to obtain a high efficient near infrared reflection BaFe12O19 nano- pigments with a solar reflectance SR>90%. The high near infrared reflection makes BaFe12O19 nano- pigments have potential applications in the field of heat shielding.

Overhead power lines magnetic field reducing in multi-story building by active shielding means

Aim. Reducing of magnetic flux density of magnetic field in multi-storey building, generated by overhead power lines to the sanitary standards level by active shielding means. The tasks of the work are the synthesis, computer simulation and experimental research of three-circuits system of active shielding, which includes three shielding coils. Methodology. When synthesizing the system of active shielding of magnetic field, are determined their number, configuration, spatial arrangement and of shielding coils as well as the shielding coils currents and resulting magnetic flux density value in the shielding space. The synthesis is based on the multi-criteria game decision, in which the payoff vector is calculated on the basis on quasi-stationary approximation solutions of the Maxwell equations. The game decision is based on the stochastic particles multiswarm optimization algorithms. Results. Computer simulation and experimental research of three-circuit system of active shielding of magnetic field, generated by overhead power lines with phase conductors triangle arrangements in multi-storey building are given. The possibility of initial magnetic flux density level reducing in multi-storey building to the sanitary standards level is shown. Originality. For the first time to reducing of magnetic flux density of magnetic field in multi-storey building the synthesis, computer simulation and experimental research of three-circuit system of active shielding of magnetic field generated by single-circuit overhead power line with phase conductors triangular arrangements carried out. Practical value. Practical recommendations from the point of view of the practical implementation on reasonable choice of the spatial arrangement of three shielding coils of three-circuit system of active shielding of the magnetic field generated by single-circuit overhead power line with phase conductors triangular arrangements in multi-storey building are given.

Pyroelectric drift of integrated-optical LiNbO3 modulators

The pyroelectric response has been studied for electro-optic modulators utilizing X-cut LiNbO3 integrated-optical chips. Since this response induces the modulator drift that appears only at fast change of a chip temperature, it causes the temperature and temporal instabilities of integrated-optical devices utilizing these chips. This drift was significantly reduced with the aid of extra electrodes providing the significant shielding of the pyroelectric field.

Electron Interference in a Quantum Ring with a Tunable Magnetic Field Shield

Electron Interference in a Quantum Ring with a Tunable Magnetic Field Shield

Characterization of High-Temperature Superconductor Bulks for Electrical Machine Application.

High-temperature superconducting (HTS) bulks can be used in electrical applications. Experimental characterization of large-size HTS bulks is a tricky issue. The relevant parameters for their application were directly measured in this study. This paper has three main aims. Firstly, features of YBaCuO bulks are presented. Secondly, an electrical motor application is developed using magnetic field shielding and trapping. Thirdly, the HTS bulks are characterized. Several classical methods were used, which are mainly magnetic methods only available for small samples. The complete penetration magnetic field and the critical current density were found to be the main parameters relevant for applications. An innovative entire HTS bulk characterization method is presented. This characterization method is useful for end users and engineers to better implement HTS bulks.

Design of Magnetic Cloak for an Alternating Magnetic Field With Multilayer ReBCO Insert

Use of superconductors for the shielding of the magnetic field is a common solution nowadays. In case when the magnetic signature of the shielding device matters, forming a magnetic cloak by combining superconductor with ferromagnetic material is a viable option. When considering the operation in alternating magnetic fields the AC loss linked to the delay in phase of the shielding currents represents an important topic. It is well known that the coated conductor (CC) tapes represent a valid alternative to bulk superconducting material when an AC loss reduction appears as a significant requirement. However, the commercially available coated conductors are usually limited to 12 mm width, therefore finding a suitable arrangement of tapes plays a significant role in the magnetic cloak design. We made a set of experiments on two possible arrangements in the superconducting part (helically wound tapes or straight pieces of the tape) and with the total number of layers up to six. For understanding the mechanism of magnetic field penetration inside the cloak the 2D and 3D numerical models were built. Presented numerical models helped in the localization of the cloak component with high energy dissipation. Analysis of the experimental and computation results allow us to formulate some recommendations for the construction of the superconducting part of the magnetic cloak.

Yoke Design for Heavy Ion Rotating Gantry HTS Combined Function Magnet

Heavy ion rotating gantries comprise large magnets to meet the requirement of high magnetic field. High-temperature superconductors (HTSs) are able to achieve notably higher current densities compared to copper conductors, and enable significant mass and size reduction. However, large yokes for magnetic field enhancement and shielding still make these gantries heavy and bulky. These yokes are made from ferromagnetic materials, and usually the field densities inside are controlled to be within a linear B-H range to avoid saturation. In this article, we found that following this design algorithm, the majority of these yokes are not effectively used with very low field densities. To achieve further mass and size reduction of these gantries, we proposed a new design method that considers partial saturation in the yokes. Detailed electromagnetic modeling has been completed to compare the new method and the conventional algorithm. Results show that the yoke size can be substantially reduced by applying the new design method. This outcome is useful for the design of more compact HTS magnets.

Enhanced photocatalytic overall water splitting via MOF-derived tetragonal BiVO4-based solid solution

In this work, BiVO4-based solid solutions, Bi0.5Y0.5VO4, were prepared via the MOF-derived method initially. The physical and chemical properties of the Bi0.5Y0.5VO4 samples were characterized by XRD, Raman spectra, XPS, HRTEM, element mapping, UV–vis DRS spectrum, TRPL and electrochemical analysis. The results showed that Y sources will be beneficial for the generation of tetragonal phase BiVO4, which made Bi0.5Y0.5VO4 samples constructed by tetragonal Bi0.5Y0.5VO4 and amorphous Bi0.5Y0.5VO4. The ratio of the tetragonal Bi0.5Y0.5VO4 was changed if the variation of the calcined time increased, which could be ascribed to the conversion of the amorphous Bi0.5Y0.5VO4. Consequently, photocatalytic overall water splitting property was enhanced and the results exhibited that Bi0.5Y0.5VO4-10 h samples exhibited the best performance with a rate of 124.2 μmol H2 and 61.7 μmol O2 per hour. The reason could be attributed to the variation of twisting degree, which thus influencing the internal electric field of the materials. More importantly, after metallic Pt particles as co-catalysts deposited, the ratio of H2:O2 was decreased. It could be proposed that the electric field shield effect will emerge to regulate the interfacial internal electric field further, which could play an essential role in the procedure of photocatalytic water splitting, especially for the reduction procedure.

Electromagnetic Field Shielding in Incubators

Purpose: Cell experiments are vitally dependent on CO2 incubators. The heating system of usual incubators result in undesirable induction of Electromagnetic (EM) fields on cells that result in decreased accuracy in bio-electromagnetic tests. EM shields can cause a considerable decrease in the stray fields and eliminate the undesirable induction. Materials and Methods: CST-2019 is used for simulations. five different shielding systems have been examined in this paper. We try to modify shape and material used for shielding to achieve better result. (Iron, Mu-Metal, steel). Results: We introduce a simple practical design, together with variations of previously reported ones, and numerical evaluation of their magnetic field attenuation. Conclusion: The targeted design decreases the field within the shield to about 0.03 times of the incident magnetic field, while having holes for air and CO2 exchange.

Tolerance of two anhydrobiotic tardigrades Echiniscus testudo and Milnesium inceptum to hypomagnetic conditions.

The open space is a hostile environment for all lifeforms not only due to vacuum, high radiation, low atmospheric pressure, and extremely low temperature, but also the absence of the geomagnetic field. The geomagnetic field protects Earth mainly from corpuscular radiation, that is, solar wind and cosmic radiation, but above all it influences organisms, including their cells, tissues and organs. Moreover, numerous studies conducted on plants and animals confirmed that hypomagnetic conditions (the term referring to all situations when the magnetic field is weaker than the typical geomagnetic field) have significant influence on the metabolism of living organisms. Although many studies dealt with a variety of aspects related mainly to the influence of hypomagnetic conditions on human health. Very few studies have considered the influence of hypomagnetic conditions on extremophiles. Astrobiologists have long been testing different extremofiles to find out if any multicellular organisms are able to survive in extreme conditions of open space. Among all multicellular extremophiles fit for such research, water bears (Tardigrada) are the most interesting. Not only are they one of the most resistant organisms on Earth, but results obtained from studies on these invertebrates can be extrapolated or applied to vertebrates (including humans). Despite this, studies on the influence of hypomagnetic conditions on tardigrades are rare, so far. In the present study, to test the influence of hypomagnetic conditions on the process of anhydrobiosis while entering and returning from anhydrobiosis, we used two terrestrial anhydrobiotic species that are Echiniscus testudo and Milnesium inceptum. To exclude the ambient magnetic field, experiments were carried out in a special magnetic field shielding chamber. In total, three experiments were conducted: (a) tardigrades in anhydrobiosis, (b) tardigrades entering anhydrobiosis and (c) tardigrades returning to active life. The obtained results clearly showed that even partial isolation from the geomagnetic field, that is, hypomagnetic conditions, has negative influence on anhydrobiotic abilities of both tested tardigrade species. In both species we observed lower survivability rate while entering anhydrobiosis, in anhydrobiotic state and returning to the active state. What is more, we observed a higher mortality rate in Ech. testudo than Mil. inceptum which suggest that different species response to the hypomagnetic conditions in different way. In conclusion, while current knowledge on the influence of hypomagnetic conditions on mortality of invertebrates is very limited, our results suggest that the presence of the magnetic field is a very important factor which should be considered in further research focused on potential survival of Earth organisms in outer space, spacecrafts or different planets and moons.

Investigation of the Mass Attenuation Coefficients, Effective Atomic Numbers and Electron Densities for Compounds of Painkiller

In this study the effects of gamma radiations with compounds are an important subject in the field of medicine, radiation shielding and radiation physics. With technological advances the using of radiation has increased in the medicine in the last century. The mass absorpsion coefficient (µ/ρ) is the fundamental a quantity characterizing gamma ray and is of major importance in radiation shielding. In this study, the mass absorption coefficient of painkillers named Ketoprofen, Flurbiprofen, Etodolac, Ibuprofen, Meloxicam, Diclofenac and Aspirin were calculated at energy range from 4.65 keV to 59.543 keV using the WinXCom data programme. In addition total atomic (σta), moleculer (σtm), electronic cross-section (σte), effective atomic number (Zeff), effective electron density (Neff) were calculated.

Parameter Modeling Analysis of a Cylindrical Ferrite Magnetic Shield to Reduce Magnetic Noise

Magnetic field shields are important for electronic equipment, ultrahigh-sensitivity sensors, and electrical instruments. For ultrahigh-sensitivity atomic sensors, in particular, ferrite shields with low intrinsic magnetic noise are widely used. In this article, the calculation methods of longitudinal and transverse magnetic noise, which are calculated by loss, are analyzed. The experimental results confirm the feasibility of the model. Using the loss separation method, it is proved that the loss of ferrite magnetic shielding is mainly hysteresis loss, which is below 100 Hz. To effectively reduce the magnetic noise, we analyze the effect of structure parameters on the longitudinal and transverse magnetic noise, and the optimized parameters are obtained. The results show that the longitudinal magnetic noise decreases with the increasing aspect ratio and stabilize eventually. When the aspect ratio exceeds 1, the transverse magnetic noise remains practically unchanged. When the external diameter is fixed, by optimizing the thickness of the magnetic shield, the optimal solution for the longitudinal and transverse magnetic noise is obtained.

Preparation of highly conductive and flexible Ag-coated single fiberglass via dopamine functionalization and electroless depositing

Flexible conductive glass fibers had widespread acquired attention in the field of electromagnetic interference shielding, sensor, and intelligent wearable devices. However, commercial fiberglass (FG) were insulators that greatly limit their application fields. Herein, flexible single FG with diameter of nearly 25 µm was manufactured by a home-made equipment. Then the surface of FG was further functionalized by dopamine self-polymerization and formed a polydopamine linker layer to chelate Ag(I) ion. Finally, the consecutive silver nanoparticles were coated on PDM/FG (polydopamine/fiberglass) via electroless plating method (Ag-PDM/FG). The SEM, XPS, and XRD results demonstrated that the silver layer on the FG surface was compact, uniform, continuous, and in a metallic crystal state. The Ag-PDM/FG exhibited excellent electrical conductivity as high as 2.49 × 106 S m−1 and could easily operate as a conductive wire for a LED device. Furthermore, the Ag-PDM/FG maintained its original conductivity even under various bending angles due to the stable Ag-coated layer. This work opens a new avenue for preparing flexible, continuous, and conductive FG with easy operation for wearable devices.

Surface modification of tungsten fillers for application in polymer matrix composites

In this research, a new class of treated metal fillers that can be used as reinforcements in polymer matrix composites have been developed. Surface modification of the tungsten metal particles is carried out using a suitable silane coupling agent. These composites are a modern type of alternative material to conventionally filled polymers. The peculiar properties of tungsten such as the highest melting point, highest tensile strength, and radiation resistance find application especially in the field of radiation shielding. Initially, the tungsten metal powder of 2 μm is treated with suitable silane i.e. 3-GlycidyloxyPropyl Tri Methoxy Silane (GPTMS) for improving the wettability of the tungsten metal fillers. Fourier Transform Infrared Spectroscopy (FTIR) and Thermo Gravimetric Analysis (TGA) was carried out to test GPTMS grafting on particles of tungsten. FTIR confirms the grafting of the silane coupling agent on tungsten particles. It also shows the reaction between these agents. TGA reveals the uniform coating of the silane coupling agent on the tungsten particles.