Synergetic effect of Fe3O4 nanoparticles and carbon on flexible poly (vinylidence fluoride) based films with higher heat dissipation to improve electromagnetic shielding
Introduction
In recent decades, with the increasing development and application of electronic devices, the electromagnetic interference (EMI) pollution becomes an unavoidable and urgent issue that need to be addressed [1], [2], [3], [4], [5], [6], [7]. Generally, the EMI can not only interrupt the normal operation and performance of the nearby devices, but can also damage the service time and stored information of those highly sensitive electronic components [8], [9], [10]. Furthermore, it can threaten the health of living beings. The presence of EMI pollution has significantly stimulated the current developments in efficient EMI shielding materials, which usually have comprehensive demands in protecting electronic devices and human biological systems [11], [12], [13], [14], [15].
The key requirements for a typical EMI shielding material are low density, high electrical conductivity, and excellent thermal stability [16], [17], [18]. Among the various EMI shielding materials, conductive polymer based composites (CPCs) are the predominant candidate to replace their metal counterparts, mainly due to their light weight, excellent shaping capability, outstanding chemical stability, and preponderant design flexibility advantages [19], [20], [21], [22]. CPCs usually consist of polymer matrixes and conductive fillers. In particular, CPCs containing carbon materials like CNTs and GNPs can offer some merits, such as controllable aspect ratio, light weight, excellent electrical conductivity, and flexibility, which have been widely used in EMI shielding materials [23], [24], [25].
It is well known that EMI shielding primarily consists of absorption and reflection aspects. The CPCs, which contain carbon materials, exhibit superior EMI shielding properties. However, a large part of EMI shielding materials stem from reflection, which may result in the secondary EMI pollution. Thus, development of high-efficiency EMI shielding materials possessing of good absorption is definitely needed. Based on the microwave absorption mechanism, electromagnetic (EM) radiation absorption materials can be generally classified into two types: dielectric loss and magnetic loss materials [7], [26], [27]. Because pure single-phase carbon filled nanocomposites can’t offer effective magnetic hysteresis loss effect, they also have limitations in EM wave absorption. To overcome this drawback, two phase hybrid of CNTs and ferromagnetic nanoparticles have been applied in EMI shielding composites [28], [29], [30]. Composites combining dielectric and magnetic losses present preeminent absorbing of electromagnetic waves. Relatively extensive studies have been conducted around the improved electromagnetic waves absorbing through employing both dielectric and magnetic losses. Menon et al., [31] reported a 23 dB EMI shielding result, with an impressive 92% absorption proportion of the incident EM radiation, using a strategy of blending magnetic FeNi alloy particles and CNTs into the PVDF matrix, coupling of the hysteresis loss, conduction loss, and the multiple scattering effects in this composites resulted in the improved shielding property. The above mentioned investigations confirmed that materials possessing both magnetic loss and dielectric loss could significantly enhance the absorption in EMI shielding application. Fe3O4 is one of the most widely used metallic oxide materials, it has some advantages such as cheap, less toxicity, better biocompatibility. More important, it can provide magnetic loss in the EMI composites. However, the application of Fe3O4 in CPCs is not extensively studied.
In this study, we prepared the PVDF/Fe3O4/MWCNTs and PVDF/Fe3O4/GNPs composites with various MWCNTs or GNPs contents. Their related electrical conductivity and EMI shielding properties were investigated. The tested results reveal that the EM absorption occupied the preponderance in the totally EMI shielding effects of the manufactured PVDF-based composites. Furthermore, these CPCs had higher thermal conductivities, which can quickly dissipate heat energy from the absorbing microwave energy. This heat transfer phenomenon can effectively protect the sensitive electronic instruments from the overheated damage.
Section snippets
Materials
The MWCNTs (Multiple Wall Carbon Nanotubes, trade No. XFM24) were purchased from XFNANO company, China. The graphene nanoplates and Fe3O4 nanoparticles were supplied by Aladdin Company (Shanghai, China). N, N-Dimethylformamide (DMF) were supplied by Tianjin Fuyu Chemicals Corporation, China. The PVDF was supplied by Solvay Company, America.
Fabrication of the PVDF/Fe3O4/Carbon composite films
The conductive flexible PVDF/Fe3O4/Carbon composite films (Fig. S1) were prepared by solution processing, and by the further compression molding, illustrated
Characterization of the PVDF/Fe3O4/CNTs composites
The as obtained Fe3O4 Nanoparticles were characterized using XRD and TEM instruments. As shown in Fig. S3, all of the diffraction peaks were well assigned to the face-centered cubic phase of the Fe3O4 Nanoparticles (JCPDS file no. 19-0629) with no other characteristic impurity peaks were found, which were indicated to the pure phase of the synthesized Fe3O4 Nanoparticles sample. Fig. S4 shows the TEM image of the Fe3O4 Nanoparticles, which are spherical particles, with a mean diameter of
Conclusion
In summary, we prepared various flexible PVDF/Fe3O4-CNTs and PVDF/Fe3O4-GNPs films. Their electrical conductivity, EMI shielding properties, and thermal conductivity were investigated in this study. Electrical conductivity and the EMI shielding properties of the PVDF/Fe3O4/CNTs and PVDF/Fe3O4/GNPs composites were increased obviously with the increasing of carbon material contents. For the PVDF/Fe3O4-8CNTs and the PVDF/Fe3O4-8GNPs composites with a same 0.7 mm thickness, the calculated SET
Acknowledgements
The authors sincerely appreciate Dr. Xianhu Liu for his useful discussion and suggestion to this article. The authors also thank the National Natural Science Foundation of China (11872338), and the Henan Province Natural Science Project of China (17A430005, 19B430011), for their kind financial supports.
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