@article{c31afde147d84dd9b5fee15bb54b2fd3,
title = "Low percolation 3D Cu and Ag shell network composites for EMI shielding and thermal conduction",
abstract = "Metal-coated polymer bead based composites are promising as electromagnetic interference (EMI) shielding and thermally conductive materials because they form a percolation 3D metal shell network at very low filler content. Herein, we fabricated 3D Cu/Ag shell network composites through electroless plating of metal on polymer beads and a simple hot pressing technique. Cu and Ag shells provide a continuous network for electron and heat conduction; thus, yielding excellent EMI shielding effectiveness of 110 dB at a 0.5 mm thickness and a thermal conductivity of 16.1 W m−1K−1 at only 13 vol % of metal filler. The properties of composites depend on the size of polystyrene (PS) beads and large size metal-coated PS bead composites exhibit higher electrical conductivity, EMI shielding effectiveness, and thermal conductivity than small size bead composites. These results are ascribed to the reduction in the number of contact interfaces between metal-coated beads, which minimizes the interfacial resistance. This study is set to pave the way for designing advanced EMI shielding and thermal conductive materials by a scalable and efficient synthesis approach.",
keywords = "3D metal shell network, EMI shielding, Low percolation, Thermal conductivity",
author = "Lee, {Seung Hwan} and Seunggun Yu and Faisal Shahzad and Junpyo Hong and Noh, {Seok Jin} and Kim, {Woo Nyon} and Hong, {Soon Man} and Koo, {Chong Min}",
note = "Funding Information: Cu and Ag deposition was further confirmed using energy dispersive X-ray spectroscopy (EDS) analysis, (Fig. S2 and S3, Supporting Information). In addition, Cu was plated on different sizes of PS (10, 40, and 230??m) to investigate the effect of bead size on the properties of the composite. Furthermore, three different metal shell thicknesses were prepared by changing the volume of CuSO4 plating solution. Table 1 shows the physical properties of the metal-plated PS beads used in this study. Density and volume calculations of the composites were performed by considering the individual densities of Cu and Ag as 8.94 and 10.49?g?cm?3, respectively. Each PS bead has three different Cu shell content, which were calculated from the TGA analysis (Fig. S4, Supporting Information). The initial TGA mass (9.348?mg in the case of 10 PSCu1) was used to determine the actual mass of Cu (1.935?mg) and PS (7.4?mg), from TGA curves (20.7?wt % for Cu and 79.3?wt % for PS, Fig. S4). The metal volume content was then found from the respective densities. Same procedure was adopted to find the total metal content for all the composites except in the case of PSCuAg, where metal density was proportionated according to the loading level of each metal as determined from thickness information. The shell thickness of Cu/Ag in the hybrid-plated bead PSCuAg was acquired using the FIB technique (Fig. S5, Supporting Information). It is evident that PS beads have more Cu by volume when a high amount of CuSO4 solution is used. In addition, the density of 230PSCuAg is slightly higher than that of 230PSCu due to the higher density of Ag.Fig. 4b shows the EMI SE of metal-plated composites at a frequency of 10?GHz and shielding thickness of 0.5?mm. All the composites exhibited an increase in EMI SE when metal content (vol. %) of the composite was increased. Among the Cu-coated composites, 230PSCu shows the highest EMI SE values of 65, 83, and 100?dB?at 2.9, 7.3, and 12.6?vol %, respectively. It is worthy to mention that an EMI SE of 100?dB is equivalent to blocking 99.99999999% of incident EM wave energy by reflection or absorption. On the other hand, 10PSCu composites exhibited EMI SE values of 32, 48, and 75?dB?at 2.9, 6.2, and 11.7?vol %, respectively. The 230PSCuAg composites show EMI SE values of 86, 90, and 110?dB?at 6.0, 8.3, and 13.0?vol %, respectively. This 230PSCuAg composite maintains a good EMI SE of 78?dB even at very low thickness of 0.3?mm?at 6?vol %. (Fig. S6, Supporting Information). The excellent EMI shielding performance is ascribed to high electrical conductivity, originating from the well-organized 3D metal shell network structure [36]. To investigate the effect of SEA and SER, SET is further divided into SEA and SER. Fig. 4c displays the SET, SER, and SEA of 10PSCu3, 40PSCu3, 230PSCu3, and 230PSCuAg3 composites. The composites had larger SEA absorption contribution than SER reflection contribution. For example, the EMI SE of 230PSCuAg3 consists of 12 and 98?dB of SER and SEA, respectively. High EMI shielding originates from excellent electrical conductivity of the composite. When EMWs strike the surface of a polymer composite, a portion is reflected back due to impedance mismatching, whereas the remaining EMWs pass through the material, where they undergo absorption due to multiple internal reflections and eddy current losses, which dissipate the EMW energy in the form of heat [3,9]. The 3D architecture of polymer composites is beneficial in shielding the EMWs, as in this case there are more opportunities to face the conductive shielding surfaces (Fig. S7, Supporting Information) [37]. High electrical conductivity of the composite with low percolation threshold means that electrons can migrate quickly from one point to another, which increase the interaction with incoming EMWs and thus contribute to Ohmic and eddy current losses [38].This work was financially supported by a grant from the Basic Science Research Program (2017R1A2B3006469) through the National Research Foundation of Korea funded by the Ministry of Science, ICT and Future Planning; Fundamental R&D Program (10077545 and 10067102) for the Core Technology of Materials; Industrial Strategic Technology Development Program funded by the Ministry of Knowledge Economy; and Smart Civil Infrastructure Research Program (SCIP) (18SCIP-B146646-01) funded by Ministry of Land, Infrastructure and Transport, Republic of Korea. Partial funding was provided by the Materials Architecturing Research Center, Young Fellow, KU-KIST School Program of the Korea Institute of Science and Technology (KIST) and Korea University. One of the authors (F.S) would like to acknowledge the financial support from KIST School Partnership Project (RFP-2019). Funding Information: This work was financially supported by a grant from the Basic Science Research Program ( 2017R1A2B3006469 ) through the National Research Foundation of Korea funded by the Ministry of Science, ICT and Future Planning ; Fundamental R&D Program ( 10077545 and 10067102 ) for the Core Technology of Materials; Industrial Strategic Technology Development Program funded by the Ministry of Knowledge Economy ; and Smart Civil Infrastructure Research Program (SCIP) ( 18SCIP-B146646-01 ) funded by Ministry of Land, Infrastructure and Transport, Republic of Korea . Partial funding was provided by the Materials Architecturing Research Center , Young Fellow , KU-KIST School Program of the Korea Institute of Science and Technology (KIST) and Korea University . One of the authors (F.S) would like to acknowledge the financial support from KIST School Partnership Project ( RFP-2019 ). Publisher Copyright: {\textcopyright} 2019 Elsevier Ltd",
year = "2019",
month = sep,
day = "29",
doi = "10.1016/j.compscitech.2019.107778",
language = "English",
volume = "182",
journal = "Composites Science and Technology",
issn = "0266-3538",
publisher = "Elsevier BV",
}