Carbon foams with low thermal conductivity and high EMI shielding effectiveness from sawdust

Chithra, A.; Wilson, Praveen; Vijayan, Sujith; Ramanan, Rajeev; Prabhakaran, K.

doi:10.1016/j.indcrop.2019.112076

Cited by 41 publications

(19 citation statements)

References 48 publications

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“…The EMI shields work by a combination of reflection and absorption mechanisms. − EMI shielding materials in the porous form are preferred over their dense counterparts as the pores improve the impedance matching leading to the easy penetration of EM waves into the material and enhances the EM absorption due to the availability of more surface. The waves that penetrate the shielding material undergo multiple internal reflections within the pores leading to enhanced absorption. ,, Recently, carbon-based foams are attracting renewed interest as EMI shields over their metallic counterparts because they are lightweight, noncorroding, inexpensive, and easy to fabricate. A typical graph showing the shielding effectiveness as a function of the frequency of a carbon foam produced from vermicelli and a 90 vol % PF solution measured in the X band region of microwave spectra is shown in Figure a.…”

Section: Resultsmentioning

confidence: 99%

Carbon Foams by Solid State Foaming of Short Vermicelli Bonded by Phenol-Formaldehyde for Thermal Insulation and Electromagnetic Interference Shielding

Saraswathy

Sharma

Prabhakaran

2023

ACS Appl. Eng. Mater.

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A simple method of production of carbon foams by randomly assembling short vermicelli rods and bonding them using phenol-formaldehyde (PF) followed by foaming in the solid state during carbonization has been reported. The brittle vermicelli becomes ductile in the range of 200−250 °C during carbonization, which facilitates the nucleation and growth of bubbles in the solid state due to the water vapor generated by the -OH condensation of starch. The dense PF coating on the vermicelli surface facilitates the enlargement of cells by restricting the escape of water vapor during the solid state foaming. The dense carbon produced from the PF binds the carbonized vermicelli rods, affording structural integrity and mechanical strength. The foam body consists of open intervermicelli void space and closed cellular pores in the carbonized vermicelli rods. A broad cell size range of 4−142 μm with an average value of 29.2 μm is observed. The density, compressive strength, and thermal conductivity of the carbon foam are modulated in the ranges of 0.30−0.34 g cm −3 , 0.63−1.6 MPa, and 0.162−0.222 W m −1 K −1 , respectively, by changing the PF solution concentration in the range of 50−90 vol %. The carbon foams exhibit absorption-dominated electromagnetic interference shielding with total shielding effectiveness and specific shielding effectiveness in the ranges of 47.5−65.6 dB and 155.2−192.9 dB cm 3 g −1 , respectively, for the X band (8.2−12.4 GHz).

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Section: Resultsmentioning

confidence: 99%

Carbon Foams by Solid State Foaming of Short Vermicelli Bonded by Phenol-Formaldehyde for Thermal Insulation and Electromagnetic Interference Shielding

Saraswathy

Sharma

Prabhakaran

2023

ACS Appl. Eng. Mater.

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“…Multiple reflections of the incident EMWs to the channel walls will be enhanced if the EMWs propagate perpendicular to the aligned pore channels [25,88]. Meanwhile, the anisotropic pore structures afford [89][90][91] stronger compressive properties in the specific direction [92][93][94][95].…”

Section: Porous Architectures With Biomimetic Ordered Pores For High-...mentioning

confidence: 99%

Hydrogel-based composites beyond the porous architectures for electromagnetic interference shielding

et al. 2022

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With the rapid development of the electronic industry and wireless communication technology, electromagnetic interference (EMI) or pollution has been increasingly serious. This not only severely endangers the normal operation of electronic equipment but also threatens human health. Therefore, it is urgent to develop high-performance EMI shielding materials. The advent of hydrogel-based materials has given EMI shields a novel option. Hydrogels combined with conductive functional materials have good mechanical flexibility, fatigue durability, and even high stretchability, which are beneficial for a wide range of applications, especially in EMI shielding and some flexible functional devices. Herein, the current progress of hydrogel-based EMI shields was reviewed, in the meanwhile, some novel studies about pore structure design that we believe will help advance the development of hydrogel-based EMI shielding materials were also included. In the outlook, we suggested some promising development directions for the hydrogel-based EMI shields, by which we hope to provide a reference for designing hydrogels with excellent EMI shielding performance and multifunctionalities.

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“…Figure 9 shows the electromagnetic wave shielding effectiveness of PU foam composite planks. When electromagnetic waves enter a shield, they are absorbed, reflected, and multi-reflected by the surface and interior or penetrate the shield via different loss mechanisms [35][36][37][38][39]. In this case, the electromagnetic energy is consumed by the shield, thereby attaining electromagnetic wave shielding effectiveness.…”

Section: Electromagnetic Wave Shielding Effectiveness Of Pu Foam Composite Planksmentioning

confidence: 99%

Novel Composite Planks Made of Shape Memory Polyurethane Foaming Material with Two-Step Foaming Process

Lin

Shiu

et al. 2022

Polymers

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In this study, shape memory polyurethane (SMP) foaming material is used as the main material that is incorporated with carbon fiber woven fabrics via two-step foaming method, forming sandwich-structured composite planks. The process is simple and efficient and facilitates any composition as required. The emphasis of this study is protection performances, involving puncture resistance, buffer absorption, and electromagnetic wave shielding effectiveness. The proposed soft PU foam composite planks consist of the top and bottom PU foam layers and an interlayer of carbon fiber woven fabric. Meanwhile, PU foam is incorporated with carbon staple fibers and an aluminized PET film for reinforcement requirements and electromagnetic wave shielding effectiveness, respectively. Based on the test results, the two-step foaming process can provide the PU foam composite planks with excellent buffer absorption, puncture resistance, and electromagnetic wave shielding effectiveness; therefore, the proposed composite planks contribute a novel structure composition to SMP, enabling it to be used as a protective composite. In addition, the composites contain conductive material and thus exhibit a greater diversity of functions.

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Carbon foams with low thermal conductivity and high EMI shielding effectiveness from sawdust

Cited by 41 publications

References 48 publications

Carbon Foams by Solid State Foaming of Short Vermicelli Bonded by Phenol-Formaldehyde for Thermal Insulation and Electromagnetic Interference Shielding

Carbon Foams by Solid State Foaming of Short Vermicelli Bonded by Phenol-Formaldehyde for Thermal Insulation and Electromagnetic Interference Shielding

Hydrogel-based composites beyond the porous architectures for electromagnetic interference shielding

Novel Composite Planks Made of Shape Memory Polyurethane Foaming Material with Two-Step Foaming Process

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