This study was aimed at fabricating composites of polylactic acid (PLA) matrix-reinforced oil palm empty fruit bunch (OPEFB) fiber filled with chemically reduced graphene oxide (rGO). A total of 2-8 wt.% rGO/OPEFB/PLA composites were characterized for their complex permittivity using an open-ended coaxial probe (OEC) technique. The shielding efficiency properties were calculated using the measured transmission (S) and the reflection (S) coefficient results. All the measurements and calculations were performed in the 8-12 GHz frequency range. The morphological and microstructural study included X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), and Fourier transform infrared spectroscopy (FTIR). The results indicated that the incorporation of rGO as filler into the composites enhanced their complex permittivity properties. The composites showed a total shielding efficiency (SE) of about 31.2 dB at a frequency range of 8-12 GHz, which suggests their usefulness for microwave absorption.
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http://dx.doi.org/10.3390/ma13204602 | DOI Listing |
ACS Appl Mater Interfaces
January 2025
Frontier Research Institute for Interdisciplinary Sciences, Tohoku University, Sendai 980-8578, Japan.
Spin-dependent charge tunneling transport of magnetic nanocomposites under alternating current or direct current has revolutionized the understanding of the quantum-mechanical phenomenon in complex granular solids. The tunnel magnetodielectric (TMD) and tunnel magnetoresistance (TMR) effects are two critical functionalities in this context, where dielectric permittivity and electrical resistance, respectively, change in response to an applied magnetic field due to charge tunneling. However, the structural correlation between TMD and TMR, as well as the mechanisms, remains poorly understood, largely due to the challenges in directly characterizing nanoscale intergranular interactions.
View Article and Find Full Text PDFBiotechnol Prog
December 2024
Department of Electrical and Computer Engineering, University of Manitoba, Winnipeg, Manitoba, Canada.
Bulk electrical impedance spectroscopy (bio-capacitance) probes, hold significant promise for real-time cell monitoring in bioprocesses. Focusing on Chinese hamster ovary (CHO) cells, we present a sensitivity analysis framework to assess the impact of cell and culture properties on the complex permittivity spectrum, ε, and its associated parameters, permittivity increment, Δε, critical frequency, f, and Cole-Cole parameter, α, measured by bio-capacitance probes. Our sensitivity analysis showed that Δε is highly sensitive to cell size and concentration, making it suitable for estimating biovolume during the exponential growth phase, whereas f provides information about cumulative changes in cell size, membrane permittivity, and cytoplasm conductivity during the transition to death phase.
View Article and Find Full Text PDFSoft Matter
December 2024
South China Advanced Institute for Soft Matter Science and Technology, School of Emergent Soft Matter, South China University of Technology, Guangzhou 510640, China.
Understanding the interplay among the mechanical behavior, ionic conductivity and chain dynamics of ionogels is essential for designing flexible conductors that exhibit both high conductivity and excellent mechanical properties. In this study, ionogels were synthesized the radical polymerization of ,'-dimethylacrylamide (DMAA) and methacrylic acid (MAAc) monomers in the presence of ionic liquid 1-ethyl-3-methylimidazolium trifluoromethane sulfonate ([EMIM][OTf]). By varying the mass content of ionic liquid within ionogels, we investigated the mechanical behavior and ionic conductivity at the macroscopic scale using tensile, rheological testing and electrochemical impedance spectroscopy, as well as the dynamic behavior of chain segments and ions within the network at the microscopic scale using broadband dielectric relaxation spectroscopy (BDS) over a broad temperature range.
View Article and Find Full Text PDFAppl Phys Lett
January 2024
Communications Technology Laboratory, National Institute of Standards and Technology, 325 Broadway, Boulder, Colorado 80305, USA.
Fused silica has become an interesting alternative to silicon for millimeter-wave (mmWave) applications. Unfortunately, there are a few reports on the measurement of fused silica's permittivity above 110 GHz that use electrical rather than optical methods. Given that mmWave applications use electrical circuits, additional electrical data would be useful to industry.
View Article and Find Full Text PDFMaterials (Basel)
December 2024
Physics Faculty, West University of Timisoara, Bd. V. Parvan, No. 4, 300223 Timisoara, Romania.
Three elastomer samples were prepared using GS530SP01K1 silicone rubber (ProChima). The samples included pure silicone rubber (SR), a silicone rubber-graphene composite (SR-GR), and a silicone rubber-magnetite composite (SR-FeO). The magnetite was synthesized via chemical precipitation but was not washed to remove residual ions.
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