Key Takeaways & Executive Findings
- •• Hierarchical melamine foam/polypyrrole nanowire arrays (MF@PPy) were fabricated via one-step electrochemical polymerization, achieving a 3D porous PPy micro-skeleton with ordered 1D PPy nanowire arrays. • The MF@PPy foams exhibited exceptional EMI shielding performance of 55.77 dB and a specific shielding effectiveness of 19,928.57 dB cm2 g−1, attributed to multiple attenuation mechanisms. • The PPy nanowire arrays imparted multifunctionality including hydrophobicity (water contact angle 142°), thermal insulation, and rapid Joule heating for dynamic infrared stealth and thermal camouflage. • This work provides a novel strategy for developing advanced multifunctional EMI shielding foams with potential applications in military and civilian fields.
Abstract
As modern communication and detection technologies advance at a swift pace, multifunctional electromagnetic interference (EMI) shielding materials with active/positive infrared stealth, hydrophobicity, and electric-thermal conversion ability have received extensive attention. Meeting the aforesaid requirements simultaneously remains a huge challenge. In this research, the melamine foam (MF)/polypyrrole (PPy) nanowire arrays (MF@PPy) were fabricated via one-step electrochemical polymerization. The hierarchical MF@PPy foam was composed of three-dimensional PPy micro-skeleton and ordered PPy nanowire arrays. Due to the upwardly grown PPy nanowire arrays, the MF@PPy foam possessed good hydrophobicity ability with a water contact angle of 142.00° and outstanding stability under various harsh environments. Meanwhile, the MF@PPy foam showed excellent thermal insulation property on account of the low thermal conductivity and elongated ligament characteristic of PPy nanowire arrays. Furthermore, taking advantage of the high conductivity (128.2 S m−1), the MF@PPy foam exhibited rapid Joule heating under 3 V, resulting in dynamic infrared stealth and thermal camouflage effects. More importantly, the MF@PPy foam exhibited remarkable EMI shielding effectiveness values of 55.77 dB and 19,928.57 dB cm2 g−1. Strong EMI shielding was put down to the hierarchically porous PPy structure, which offered outstanding impedance matching, conduction loss, and multiple attenuations. This innovative approach provides significant insights to the development of advanced multifunctional EMI shielding foams by constructing PPy nanowire arrays, showing great applications in both military and civilian fields.
1. Introduction
The vigorous evolution of the fifth-generation information technology and the proliferation of electromagnetic devices have significantly enhanced societal productivity and living standards. However, this advancement has also led to an increase in electromagnetic pollution [1, 2]. This pervasive issue has generated detrimental effects on human health and system failure. Therefore, the innovation of advanced electromagnetic interference (EMI) shielding materials has become an essential approach to address the escalating concerns associated with electromagnetic pollution [3, 4]. Conductive polymer composites (CPCs) have garnered considerable attention as exemplary EMI shielding materials, owing to lightweight, low cost, good chemical stability, and convenient processing [5–7]. Compared to conventional dense bulk EMI shielding materials, porous foams with three-dimensional (3D) skeleton can provide multiple interfaces and achieve better impedance matching, thus enabling to more effectively absorb and attenuate incident electromagnetic waves (EMWs) [8, 9].
It is well known that melamine foam (MF) has the characteristics of high porosity, lightweight, excellent resilience, and environmental friendliness, making it an excellent substrate for EMI shielding materials [10, 11]. Its inherent 3D network framework serves as an ideal template for constructing a continuous conductive pathway with low filler content [12, 13]. Some researchers have been actively exploring the fabrication of MF-based EMI shielding materials by binding/depositing electrically conductive fillers (such as MXene, graphene, silver nanowire arrays, metal–organic frameworks, etc.) onto the framework of foam [14–16]. Benefiting from the well-established 3D conductive network and inner porous structure, the MF-based materials exhibit high EMI shielding performance by multiple absorption. Furthermore, the future application of EMI shielding materials may extend into more intricate and diverse practical scenarios and fields, requiring more functions to meet the growing demand simultaneously. For instance, flexible and superhydrophobic EMI shielding materials are urgently desirable for protecting sensitive electronic devices or human health. Meanwhile, infrared stealth is an important method to hide the features of covered objects in the infrared frequencies of the EM spectrum. This puts forward higher requirements for material function integration in fields such as flexible sensing, water repellence, thermal management, and infrared stealth [7, 17, 18].
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Yu-long Liu, Ting-yu Zhu, Qin Wang, Zi-jie Huang, De-xiang Sun, Jing-hui Yang, Xiao-dong Qi, Yong Wang (2024). Hierarchically Porous Polypyrrole Foams Contained Ordered Polypyrrole Nanowire Arrays for Multifunctional Electromagnetic Interference Shielding and Dynamic Infrared Stealth. Nano-Micro Letters. https://doi.org/10.1007/s40820-024-01588-x
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Frequently Asked Questions
What is the main innovation of this research?
The main innovation is the fabrication of hierarchical melamine foam/polypyrrole (MF@PPy) foams with ordered PPy nanowire arrays via one-step electrochemical polymerization, achieving multifunctional properties including EMI shielding, hydrophobicity, thermal insulation, and dynamic infrared stealth.
How does the MF@PPy foam achieve high EMI shielding performance?
The MF@PPy foam achieves high EMI shielding effectiveness (55.77 dB) and specific shielding effectiveness (19,928.57 dB cm2 g−1) through multiple attenuation mechanisms, including impedance matching, conduction loss, and multiple internal reflections within the hierarchically porous structure.
What are the key multifunctional properties of the MF@PPy foam?
The MF@PPy foam exhibits hydrophobicity (water contact angle of 142°), excellent thermal insulation, rapid Joule heating under low voltage (3 V), and dynamic infrared stealth and thermal camouflage capabilities.
What are the potential applications of this material?
The material shows great potential in both military and civilian fields, such as protecting sensitive electronic devices, electromagnetic pollution shielding, thermal management, and infrared stealth applications.
How was the MF@PPy foam fabricated?
The MF@PPy foam was fabricated via a one-step electrochemical polymerization method, where melamine foam served as a template for the growth of polypyrrole nanowire arrays, forming a hierarchical structure with a 3D PPy micro-skeleton and 1D PPy nanowire arrays.
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