Ultralightweight silver nanowires hybrid polyimide composite foams for high-performance electromagnetic interference...

Area of Science:

• Materials Science
• Nanotechnology
• Polymer Composites

Background:

• Developing lightweight materials with effective electromagnetic interference (EMI) shielding is crucial for advanced electronic applications.
• Existing composite materials often face limitations in achieving high shielding effectiveness at low densities.
• Silver nanowires (AgNWs) are promising conductive fillers, but their uniform dispersion and network formation in polymer matrices remain challenging.

Purpose of the Study:

• To fabricate ultralightweight silver nanowire (AgNW) hybrid polyimide (PI) composite foams with microcellular structures.
• To investigate the influence of AgNW loading and aspect ratio on the electromagnetic interference (EMI) shielding effectiveness (SE).
• To explore the role of surface treatment in enhancing the EMI shielding performance of the composite foams.

Main Methods:

• Fabrication of AgNW/PI composite foams using a facile one-pot liquid foaming process.
• Characterization of microcellular structure, density, and AgNW dispersion within the polyimide matrix.
• Evaluation of electromagnetic interference (EMI) shielding effectiveness (SE) across a range of frequencies.
• Surface treatment (etching or spraying) applied to composite foams to optimize AgNW network formation.

Main Results:

• Ultralightweight foams with densities ranging from 0.014-0.022 g/cm³ were successfully fabricated.
• Uniform dispersion of AgNWs within the cell walls was achieved due to tension flow during cell growth.
• Interconnected AgNW networks, both within cell walls and in a 3D foam structure, provided efficient electron transport channels.
• Maximum specific EMI SE values of 1210 dB·g⁻¹·cm³ (at 200 MHz), 957 dB·g⁻¹·cm³ (at 600 MHz), and 772 dB·g⁻¹·cm³ (at 800-1500 MHz) were achieved with sprayed foams containing <0.044 vol % AgNWs.
• Shielding effectiveness increased with AgNW loading and aspect ratio, attributed to enhanced conduction network connectivity.

Conclusions:

• The developed AgNW/PI composite foams exhibit outstanding specific EMI shielding effectiveness, surpassing existing composite materials.
• The combination of uniform AgNW dispersion, interconnected 2D/3D networks, and surface treatments is key to achieving high EMI shielding performance.
• These ultralightweight foams represent a promising solution for advanced electromagnetic shielding applications.