Synthesis, characterization and dielectric properties of one-step pyrolyzed / activated resorcinol-formaldehyde based carbon aerogels for electromagnetic interference shielding applications

• Published in: Materials chemistry and physics Vol. 213; pp. 492 - 501
• Main Authors: Abolghasemi Mahani, A., Motahari, S., Nayyeri, V.
• Format: Journal Article
• Language: English
• Published: Lausanne Elsevier B.V 01-07-2018; Elsevier BV
• Subjects: Activated carbon; Activation; Aerogels; Aldehydes; Carbon; Carbon aerogel; Carbonization; Chemical synthesis; Dielectric properties; Electromagnetic shielding; Electromagnetism; EMI shielding; Epoxy resins; Formaldehyde; Numerical controls; Pressure; Pyrolysis; Resorcinol-formaldehyde gel; Sol-gel method; Sol-gel processes; Synthetic products; Resorcinol-formaldehyde gel; Carbon aerogel; Sol-gel method; EMI shielding
• ISSN: 0254-0584; 1879-3312
• DOI: 10.1016/j.matchemphys.2018.04.047

The present study is an attempt to investigate the effects of simultaneous pyrolysis/activation processes and 3D network characteristic on structural, dielectric and electromagnetic interference (EMI) shielding properties of one-step activated carbon foam (CAs) filled in epoxy resin. Samples were synthesized via sol-gel process of resorcinol and formaldehyde followed by ambient pressure drying. To investigate the effect of pyrolysis process on structural properties and EMI shielding performance of samples, carbonization and activation processes were carried out simultaneously under CO2 atmosphere at varied residence time. To investigate the influence of 3D network characteristic on the dielectric and EMI shielding performance of the synthesized CAs, samples were ground down to two different particle sizes of 44 and 1 μm. The former (samples with 44 μm in size) preserved carbons with network characteristic (CNC) and the latter turned into pulverized carbon (PCA) with no 3D network characteristic. The results revealed that the pyrolysis residence time had a meaningful effect on both structural and dielectric characteristics of the synthesized CAs. It was also shown that owing to the 3D network structure, the CNC samples provided several times higher shielding efficiency compared to their corresponding PCA. EMI shielding performance of CNC based composites containing 5 wt% exceeded 20 dB at a very thin thickness of 2 mm. Finally, it has been demonstrated that compared to the similar recent works, the prepared carbons exhibited a more efficient shielding performance at a lower loading fraction, indicating that these materials present advantages as microwave shielding.
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•Time of pyrolysis has a critical effect on the structural and EMI shielding characteristics of the prepared samples.•EMI shielding characteristics of CNC composites improves significantly when the time of pyrolysis varies from 0.5 to 2 h.•Compared with pulverized form, carbon in a cluster form shows a higher level of dielectric constant and dielectric loss.•An effective SET of 88 dB is obtained by using 5% wt of the porous CNC in an 11 mm thickness composite.•Pyrolysis under CO2 atmosphere leads to the formation of the CAs with a broader PSD and higher EMI shielding effectiveness.