Lalan Vidhya, Puthiyedath Narayanan Aparna, Surendran Kuzhichalil Peethambharan, Ganesanpotti Subodh
Department of Physics, University of Kerala, Thiruvananthapuram 695581, Kerala, India.
Materials Science and Technology Division, CSIR-National Institute for Interdisciplinary Science and Technology (NIIST), Thiruvananthapuram 695019, India.
ACS Omega. 2019 May 6;4(5):8196-8206. doi: 10.1021/acsomega.9b00454. eCollection 2019 May 31.
In this study, we fabricated composites of conducting carbon black (CB), room-temperature ferromagnetic SrYCoO (SYCO) and polyvinylidenefluoride (PVDF) by the solution mixing and coagulation method for the first time. During the nucleation process of PVDF, the presence of SYCO and CB individually facilitates the crystallization of polar β and semipolar γ phases along with the nonpolar α phase in PVDF. The dc electrical conductivity of PVDF raised from 1.54 × 10 to 9.97 S/m with the addition of 30 wt % of CB, and it is nearly constant with respect to the SYCO content. The PVDF/CB/SYCO composites (PCS) possess high permittivity and its variation is in accordance with the content of polar phases in PVDF. Moreover, the complex permittivity and permeability spectra from 10 MHz to 1 GHz indicate that the dielectric loss dictates over magnetic loss in these composites. The electromagnetic interference shielding effectiveness (EMI SE) of PCS composites is higher than that of PVDF/CB and PVDF/SYCO composites in the 8.2-18 GHz region. Addition of SYCO in the PVDF/CB matrix enhances shielding by dominated absorption with minimal reflection. The analysis of the shielding mechanism suggests that in addition to conducting and magnetic losses due to CB and SYCO, respectively, the synergy among CB, SYCO, and PVDF promotes shielding by matching the input impedance to that of free space, enhancing multiple internal reflections from SYCO and subsequent absorption by CB, eddy current losses, dielectric damping losses, interfacial polarization losses, and so forth. These different mechanisms result in an enhanced EMI SE of 50.2 dB for the PCS-40 composite for a thickness of 2.5 mm.
在本研究中，我们首次通过溶液混合和凝固法制备了导电炭黑（CB）、室温铁磁体SrYCoO（SYCO）和聚偏二氟乙烯（PVDF）的复合材料。在PVDF的成核过程中，SYCO和CB的存在分别促进了PVDF中极性β相和半极性γ相以及非极性α相的结晶。随着30 wt%的CB加入，PVDF的直流电导率从1.54×10提升至9.97 S/m，并且其相对于SYCO含量几乎保持不变。PVDF/CB/SYCO复合材料（PCS）具有高介电常数，其变化与PVDF中极性相的含量一致。此外，从10 MHz到1 GHz的复介电常数和磁导率谱表明，在这些复合材料中，介电损耗占主导地位，超过磁损耗。在8.2 - 18 GHz区域，PCS复合材料的电磁干扰屏蔽效能（EMI SE）高于PVDF/CB和PVDF/SYCO复合材料。在PVDF/CB基体中添加SYCO通过以最小反射为主的吸收增强了屏蔽效果。屏蔽机制分析表明，除了分别由CB和SYCO引起的传导损耗和磁损耗外，CB、SYCO和PVDF之间的协同作用通过使输入阻抗与自由空间的阻抗匹配、增强来自SYCO的多次内部反射以及随后被CB吸收、涡流损耗、介电阻尼损耗、界面极化损耗等促进了屏蔽。这些不同的机制使得厚度为2.5 mm的PCS - 40复合材料的EMI SE增强至50.2 dB。
