Multifunctional hybrids for electromagnetic absorption

Huynen, Isabelle; Quiévy, Nicolas; Bailly, Christian; Bollen, Pierre; Detrembleur, Christophe; Eggermont, Stéphanie; Molenberg, Isabel; Thomassin, Jean‐Michel; Urbanczyk, Laetitia; Pardoen, Thomas

doi:10.1016/j.actamat.2011.01.065

Cited by 116 publications

(53 citation statements)

References 17 publications

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“…From the Debye theory of dielectrics, it is known that the permittivity of a dielectric material increases with increasing electrical conductivity. 17,18 The relationship between the imaginary part of permittivity and electrical conductivity was very consistent with the theory in this study. The imaginary part of permittivity represents the dielectric loss ability of materials.…”

Section: Effect Of Concentration On Electrical Conductivitysupporting

confidence: 77%

Concentration-related microwave heating processes: electromagnetic interference of Maillard reaction substrates (glucose and lysine)

et al. 2017

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a Glucose and lysine are important substrates involved in the Maillard reaction. The lack of studies on their electromagnetic properties has made it impossible to understand the influence of electromagnetic properties on the microwave heating process, and has hindered the application of the Maillard reaction in the microwave field. In this study, the electromagnetic properties of glucose, lysine solution and their 1 : 1 mixture were determined at frequencies of 1.7-2.6 GHz. The results show that the dielectric loss factors gradually increased. Reflection loss gradually decreased with concentration in the order of glucose > mixture > lysine. The heating rates gradually increased at low concentrations (#5%) and slowly changed at high concentrations ($10%). These results indicate that the effect of electromagnetic properties on the heating rate is related to concentration. The heating rates depended on the dielectric properties at low concentrations (#5%), whereas microwave-absorption properties dominated at high concentrations ($10%).

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Section: Effect Of Concentration On Electrical Conductivitysupporting

confidence: 77%

Concentration-related microwave heating processes: electromagnetic interference of Maillard reaction substrates (glucose and lysine)

et al. 2017

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“…When increasing the concentration of conductive inclu sions in polymer composites, although several authors have reported absorption being the main internal shielding mech anism, as is the case herein presented, they do not commonly take into account that this discussion is assessed to the EM power that has not been reflected at the input interface of the slab [58,59]. Thus, evaluating the power balance of the in put EM wave is of primary importance when trying to deter mine whether the composite may be considered as a real EMI absorber, since reflection occurs before absorption.…”

Section: Electromagnetic Shieldingmentioning

confidence: 98%

Synergistic effect of magnetite nanoparticles and carbon nanofibres in electromagnetic absorbing composites

Crespo

Méndez

González

et al. 2014

Carbon

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Epoxy composites with different amounts of magnetite nanoparticles, carbon nanofibres (CNF) and magnetite decorated CNF were prepared and characterized. A simple method for the magnetite CNF decoration was developed by adsorbing preformed oleic acid capped magnetite nanoparticles over the CNF surface. A synergy between magnetite nano particles and CNF was found to have crucial effects in the electromagnetic shielding effi ciency of the prepared materials. This effect has been analysed by their electrical conductivity in terms of percolation theory and complex permittivity at high frequencies. Electromagnetic shielding mechanisms (reflection, absorption and transmission) were individually studied in the 1 18 GHz range. Results show that decoration of CNF with mag netite, notably increases permittivity and high frequency AC conductivity and enhances the electromagnetic shielding efficiency up to around 20 dB at high frequencies. It is pro posed that interfacial polarization adds an additional dissipation mechanism that may be responsible for the observed electromagnetic shielding enhancement. IntroductionAn electronic device is considered compatible with the envi ronment when its emissions do not affect other devices and is not affected itself by external emissions. Thus, any effort for minimizing interferences and protecting electronic de vices is of prime importance. Electromagnetic interferences (EMI) in many cases are minimized through the circuit design or using filters, while protection of devices is generally im proved with the use of metallic coatings [1 3], metal casings or polymer conductive composites [4 23]. The shielding mechanism in the two former cases is mainly related with radiation reflection processes while radiation absorption is the main mechanism in the latter. The choice of a material for shielding depends strongly on the final application: for example, low reflection losses and high absorption losses are required for military radar shielding materials whilst lightweight materials are a must for aerospace shielding applications; polymer matrix composites are thus promising materials that may fulfil a variety of requirements in all the above emerging fields. Three mechanisms for electromagnetic shielding are com monly accepted: reflection, absorption and multiple reflec tions [22]. In good conductors (i.e.: metals), the most important contribution is reflection, where losses are related with the ratio between conductivity and permeability (r/l). When considering composites, absorption, which depends on the product (rAEl) and on the thickness of the material, is * Corresponding author: Fax: +34 91 6249430. E mail address: jpozue@ing.uc3m.es (J. Pozuelo).1 the main mechanism. The third mechanism (multiple reflec tions) is related to the conductor skin thickness and for high frequencies, in the GHz range, is negligible [23]. For the pro tection of electronic devices towards external radiation, the most important mechanism should be reflection, so high con ductivity and low permeability is requir...

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“…The losses of incident EM waves into pores are simply caused by the dissipation of electric current in the pore walls. It has been revealed that the materials with high absorption require a low real part of permittivity and an appropriately higher electrical conductivity [54]. In case of IPAg1.5, the imaginary part was slightly higher than that of the real part.…”

Section: Emi Shielding Effectiveness Of Carbon Foammentioning

confidence: 98%

Carbon foam decorated with silver particles and in situ grown nanowires for effective electromagnetic interference shielding

Farhan

Wang

2016

J Mater Sci

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Carbon foam filled with silver particles was fabricated by a powder molding process using polyurethane as pore former, novolac resin as binder, coal-tar pitch as densification additive, and silver foils as a filler. High-temperature treatment at 1200°C, transformed the silver into spherical particles covered with in situ grown Ag nanowires. Their microstructure, electromagnetic interference (EMI) shielding effectiveness (SE), and shielding mechanism was investigated. It was found that the micron-sized silver foils converted into particles during heat treatment and strongly bonded in carbon matrix. The addition of silver significantly enhanced both conductivity and SE. Carbon foam containing 1.5 wt% silver exhibited very impressive total SE and dielectric loss tangent owing to the more conductive network of silver particles providing fast electron-transport channels. A maximum specific EMI SE value of 58.21 dB g -1 cm 3 at 12 GHz was achieved in the carbon foam at 1.5 wt% Ag loading. The dominant mechanism was absorption with only 6-10 % reflectance, resulting from the multiple reflections at interfaces inside the foam. Due to controlled attachment of silver particles and in situ reactions, this novel substrate has unique opportunities for future surface tailoring required in various commercial and aerospace fields.

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Multifunctional hybrids for electromagnetic absorption

Cited by 116 publications

References 17 publications

Concentration-related microwave heating processes: electromagnetic interference of Maillard reaction substrates (glucose and lysine)

Concentration-related microwave heating processes: electromagnetic interference of Maillard reaction substrates (glucose and lysine)

Synergistic effect of magnetite nanoparticles and carbon nanofibres in electromagnetic absorbing composites

Carbon foam decorated with silver particles and in situ grown nanowires for effective electromagnetic interference shielding

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