Search Results (277)

Polyimide, a class of high-performance polymers, is renowned for its exceptional thermal stability, mechanical strength, and chemical resistance. However, in the context of high-integration and high-frequency electronic packaging, polyimides face critical challenges including relatively high dielectric constants, inadequate thermal conductivity, and mechanical brittleness. Recent advances have focused on molecular design and composite engineering strategies to address these limitations. This review first summarizes the intrinsic properties of polyimides, followed by a systematic discussion of chemical synthesis, surface modification approaches, molecular design principles, and composite fabrication methods. We comprehensively examine both conventional polymerization synthetic routes and emerging techniques such as microwave-assisted thermal imidization and chemical vapor deposition. Special emphasis is placed on porous structure engineering via solid-template and liquid-template methods. Three key modification strategies are highlighted: (1) surface modifications for enhanced hydrophobicity, chemical stability, and tribological properties; (2) molecular design for optimized dielectric performance and thermal stability; and (3) composite engineering for developing high-thermal-conductivity materials with improved mechanical strength and electromagnetic interference (EMI) shielding capabilities. The dielectric constant of polyimide is reduced while chemical stability and wear resistance can be enhanced through the introduction of fluorine groups. Ultra-low dielectric constant and high-temperature resistance can be achieved by employing rigid monomers and porous structures. Furthermore, the incorporation of fillers such as graphene and boron nitride can endow the composite materials with high thermal conductivity, excellent EMI shielding efficiency, and improved mechanical properties. Finally, we discuss representative applications of polyimide and composites in electronic device packaging, EMI shielding, and thermal management systems, providing insights into future development directions. Full article

The development of lightweight composites with superior mechanical properties and electromagnetic interference (EMI) shielding performance is essential for various structural and functional applications. This study investigates the effect of hybrid nanocarbon (graphene nanosheet (GNS) and carbon nanotube (CNT)) reinforcements on the properties of magnesium (Mg) matrix composites. Specifically, the GNS-CNT hybrid, which forms a three-dimensional interconnected network structure, was analyzed and compared to composites reinforced with only GNSs or CNTs. The objective was to determine the benefits of hybrid reinforcements on the mechanical strength and EMI shielding capability of the composites. The results indicated that the GNS-CNT/Mg composite, at a nanocarbon content of 0.5 wt.% and a GNS-CNT ratio of 1:2, achieved optimal performance, with a 55% increase in tensile strength and an EMI shielding effectiveness of 70 dB. The observed enhancements can be attributed to several key mechanisms: effective load transfer, which promotes tensile twinning, along with improved impedance matching and multiple internal reflections within the GNS-CNT network, which enhance absorption loss. These significant improvements position the composite as a promising candidate for advanced applications requiring high strength, toughness, and efficient electromagnetic shielding, providing valuable insights into the design of high-performance lightweight materials. Full article

This study presents the first successful integration of Fe₃O₄ and Li_0.5Cr_0.5Fe₂O₄ into a well-defined core/shell nanostructure through a two-step synthesis that combines co-precipitation and sol–gel auto-combustion methods. Unlike conventional composites, the core/shell design effectively suppresses the magnetic dead layer and promotes exchange coupling at the interface, leading to enhanced saturation magnetization, superior magnetic heating (specific absorption rate; SAR), and improved dielectric properties. Our research introduces a novel interfacial engineering strategy that simultaneously optimizes both magnetic and dielectric performance, offering a multifunctional platform for applications in magnetic hyperthermia, electromagnetic interference (EMI) shielding, and microwave devices. Full article

Superparamagnetic magnetite nanoparticles (Fe₃O₄) have garnered considerable interest due to their unique magnetic properties and potential for integration into multifunctional biomaterials. In particular, their incorporation into bacterial cellulose (BC) matrices offers a promising route for developing sustainable and high-performance magnetic composites. Numerous studies have explored BC-magnetite systems; however, innovations combining ex situ coprecipitation synthesis within BC matrices, tailored reagent molar ratios, stirring protocols, and purification processes remain limited. This study aimed to optimize the ex situ coprecipitation method for synthesizing superparamagnetic magnetite nanoparticles embedded in BC membranes, focusing on enhancing particle stability and crystallinity. BC membranes containing varying concentrations of magnetite (40%, 50%, 60%, and 70%) were characterized using X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and vibrating sample magnetometry (VSM). The resulting magnetic BC membranes demonstrated homogenous dispersion of nanoparticles, improved crystallite size (6.96 nm), and enhanced magnetic saturation (Ms) (50.4 emu/g), compared to previously reported methods. The adoption and synergistic optimization of synthesis parameters—unique to this study—conferred greater control over the physicochemical and magnetic properties of the composites. These findings position the optimized BC-magnetite nanocomposites as highly promising candidates for advanced applications, including electromagnetic interference (EMI) shielding, electronic devices, gas sensors, MRI contrast agents, and targeted drug delivery systems. Full article

We consider light, high-absorbance, low-reflectance, electrically large layered sheet structures composed of thin carbon nanotube films. Such structures can be utilized in electromagnetic absorption and shielding applications in the X-band. They are of increasing interest in sensor-enabling technologies, stealth systems, and EMI shielding of electronic components. Especially in aerospace, this is crucial, as sensors are integral to aerospace engineering, enhancing the safety, efficiency, and performance of aircraft and spacecraft. To that end, sheets with carbon nanotube films embedded in a glass fiber polymer matrix are fabricated. The films have a thickness of around 70 μm. As shown, they cause a significant attenuation of the electromagnetic field. For shielding applications, a single-film sheet structure with total thickness of 1.65 mm presents an attenuation of around 25 dB in the transmission coefficient, while the attenuation can reach 37 dB for a two-film sheet structure with thickness of 1.8 mm. Shielding effectiveness performance is found to be greater than 35 dB for the two-film sheet structure. For applications requiring both high shielding and absorption, a two-layered structure with a thickness of 4.65 mm has been designed. The absorption, represented by the Loss Factor, is calculated to achieve values greater than 90%. The simulation results show good agreement with the measured data. The findings demonstrate a promising structure for materials suitable for sensor housings and smart electromagnetic environments where the suppression of electromagnetic interference is critical. In conclusion, the addition of carbon nanotube films, even at micrometer thicknesses, within a glass fiber polymer matrix significantly enhances both electromagnetic shielding and absorption performance. Full article

In this work, the critical properties of epoxy resin reinforced with carbon-based nanoparticles were examined in order to improve its performance in protective coating applications. Epoxy resin composites with commercial multi-walled carbon nanotubes (MWCNTs) and graphene (GP) nanoplates were prepared via solution mixing. In addition, hybrid composites with 50:50 w/w MWCNTs/GP were also examined. The characterization of the EMI shielding effectiveness revealed that epoxy resin composites reinforced with MWCNTs presented the best performance. Composites with the same content of graphene exhibited much lower shielding results. As confirmed by electrical conductivity measurements, this outcome can be explained by the fact that the electrical percolation threshold in the composites reinforced with MWCNTs was met (around 5 phr), while the conductive network in the composites with graphene was not completely developed. An analysis of the mechanisms that contributed to EMI shielding for each type of specimen showed that, in the case of MWCNT composites, the main mechanism that determined the response of the material was reflection rather than absorption. It was also observed that by increasing the MWCNT content, the shielding efficiency of the composites was enhanced. In the case of graphene composites, the absorption and reflection remained at low levels, resulting in high transmission and therefore poor shielding. Regarding the examined hybrid composites (MWCNTs:GP at 50:50 w/w), it seemed that the MWCNT content determined their shielding performance. Full article

With the growing integration of electronic systems into modern infrastructure, the need for effective electromagnetic interference (EMI) shielding materials has intensified. This study explores the development of electroless Ni-plated fiber composites and systematically investigates the effects of post-heat treatment on their electrical, structural, and interfacial performance. Both carbon fibers (CFs) and glass fibers (GFs) were employed as reinforcing substrates, chosen for their distinct mechanical and thermal characteristics. Ni plating enhanced the electrical conductivity of both fibers, and heat treatment facilitated phase transformations from amorphous to crystalline Ni₃P and Ni₂P, leading to improved EMI shielding effectiveness (EMI-SE). NGF-based composites achieved up to a 169% increase in conductivity and a 116% enhancement in EMI-SE after treatment at 400 °C, while NCF-based composites treated at 800 °C attained superior conductivity and shielding performance. However, thermal degradation and reduced interfacial shear strength (IFSS) were observed, particularly in GF-based systems. The findings highlight the importance of material-specific thermal processing to balance functional performance and structural reliability. This study provides critical insights for designing fiber-reinforced composites with optimized EMI shielding properties for application-driven use in next-generation construction materials and intelligent infrastructure. Full article

The rapid proliferation of electronic devices has heightened the demand for efficient electromagnetic interference (EMI) shielding materials, as conventional alternatives increasingly fall short in mitigating harmful electromagnetic radiation. In this study, we report the fabrication of acrylonitrile butadiene styrene (ABS) nanocomposite films reinforced with graphene nanoplatelets (GNPs), offering a promising solution to this growing challenge. A persistent issue in incorporating GNPs into the ABS matrix is their poor wettability, which impedes uniform dispersion. To overcome this, a sonication-assisted casting technique was employed, enabling effective integration of GNPs at loadings of 1, 3, and 5 wt%. The resulting nanocomposite films exhibit uniform dispersion and enhanced functional properties. Comprehensive characterization using FESEM, UV-Vis spectroscopy, TGA, DSC, FTIR, and dielectric/EMI analyses revealed significant improvements in thermal stability, UV absorption, and dielectric behavior. Notably, the films demonstrated moderate EMI shielding effectiveness, reaching 0.0064 dB at 4 MHz. These findings position the developed GNP-reinforced ABS nanocomposites as promising candidates for advanced applications in the automotive, aerospace, and electronics industries. Full article

The expected outstanding performance of GaN-based transistors in power applications, characterized by high switching frequency, efficiency, and compactness, requires that the design rules of converter layout optimization, filtering, and shielding need to be reexamined. Addressing the above topics, this paper reviews commercial GaN power transistors and specifies their integration techniques, including printed circuit board (PCB) embedded solutions. Then, referring to the optimization results of a half-bridge inverter leg, design techniques are presented that reduce the harmful effect of inductive and capacitive internal converter couplings, thus mitigating the electromagnetic interference (EMI) conducted emissions. Full article

Electromagnetic interference (EMI) shielding is critical for maintaining signal integrity in high-speed electronic packaging. However, conventional shielding approaches face limitations in process complexity and spatial efficiency. In this study, an EMI shielding film based on trimodal silver (Ag) ink and low-dielectric polyimide (PI) resin was developed and comprehensively evaluated. The fabricated film exhibited an average shielding effectiveness (SE) of −99.7 dB in the 6–18 GHz frequency range and demonstrated a 50% increase in electrical conductivity after lamination (from 0.752 × 10⁵ S/m to 1.13 × 10⁵ S/m). The horizontal thermal conductivity reached 34.614 W/m·K, which was 3.4 times higher than the vertical value (10.249 W/m·K). Signal integrity simulations showed significant reductions in near-end crosstalk (NEXT, 77.8%) and far-end crosstalk (FEXT, 65%). Moreover, cyclic bending tests confirmed excellent mechanical durability, with a normalized resistance change below 0.6 after 1000 cycles at a bending radius of 4 mm. Notably, the film enabled a 50% reduction in signal line spacing while maintaining signal integrity, even without strict compliance with the 3W Rule. These results demonstrate the potential of the proposed EMI shielding film as a high-performance solution for advanced packaging applications requiring high-frequency operation, thermal management, and mechanical flexibility. Full article

This review presents our band-selective frequency technology of Electromagnetic Interference (EMI) noise spread spectrum in the DC–DC switching converter for communication devices. The DC–DC switching converter generates electromagnetic interference (EMI) noise. To comply with EMI regulations and reduce the need for bulky filters and shielding, noise spread spectrum technology is commonly employed. However, conventional methods may allow noise to encroach upon the signal band. To address this issue, selective notch frequency technology has been developed. This technology creates notch characteristic spectrum bands, ensuring a low noise level within the received frequency range. It detects the received frequency and generates a notch band there using a switching pulse control technology. This technology employs pulse coding techniques, including pulse width coding, pulse phase coding, and a combination of pulse width and phase coding. Then, we demonstrate a technique that tunes the notch band frequency to the received signal one automatically. We review their underlying principles, theoretical analyses, and experimental results, which validate the effectiveness of the selective notch frequency technology. Also, possible applications of this technology to sensor systems are discussed. Full article

Inductive power transfer (IPT) systems are transforming railway infrastructure by enabling efficient, wireless energy transmission for electric locomotives equipped with Li-ion batteries. This technology eliminates the need for overhead power lines and third rails, offering financial and operational advantages over conventional electric propulsion systems. Despite its potential, IPT deployment in rail applications faces significant challenges, including the fragility of materials (i.e., ferrite and Litz wires), thermal management during high-power transfers, and electromagnetic interference (EMI) on the transmitter side. This study discusses several factors affecting IPT efficiency and introduces magnetic concrete as a durable and cost-effective material solution for IPT systems. Magnetic concrete combines soft ferrite powder with water and coarse aggregates to enhance magnetic functionality while maintaining structural strength comparable to conventional concrete. Its durability and optimized magnetic properties promote consistent power transfer efficiency, making it a viable alternative to traditional ferrite cores. A comparative study has been performed on non-magnetic and magnetic concrete (with 33% ferrite powder) using both permeability tests and finite element analysis (FEA). The FEA includes both thermal and electromagnetic simulations using Ansys Maxwell (v.16), revealing that magnetic concrete can improve temperature management and EMI mitigation, and the findings underscore its potential to revolutionize IPT technology by overcoming the limitations of traditional materials and enhancing durability, cost-efficiency, and power transfer efficiency. By addressing the challenges of fragility, thermal management, and shielding of the unique coil topology design presented, this study lays the groundwork for improving IPT infrastructure in sustainable and efficient rail transport systems. Full article

Ti-based MXenes such as Ti₃C₂T_X and Ti₂CT_X have attracted considerable attention because of their superior electromagnetic interference (EMI) shielding effectiveness compared to other EMI shielding materials, especially for high electromagnetic (EM) wave absorption. In this study, we investigated the microstructural changes produced by heat treatment and their effect on the EMI shielding properties of Ti-based MXenes. Ti₃C₂T_X and Ti₂CT_X films were prepared using vacuum filtration and annealed at temperatures up to 300 °C. The microstructures and chemical bonding properties of these heat-treated Ti₃C₂T_X and Ti₂CT_X films were analyzed, and the EMI shielding effectiveness was measured in the X-band and THz frequency range. The porous Ti₃C₂T_X film showed higher EM absorption than that calculated using the transfer matrix method. On the other hand, the Ti₂CT_X films had a more densely stacked structure and lower EM absorption. As the heat treatment temperature increased, Ti₃C₂T_X developed a more porous structure without significant changes in its chemical bonding. Its EM absorption per unit of thickness increased up to 6 dB/μm, while the reflectance remained constant at less than 1 dB/μm after heat treatment. This suggested that the heat treatment of Ti-based MXenes can increase the porosity of the film by removing residual organics without changing the chemical bonds, thereby increasing electromagnetic shielding through absorption. Full article

MXenes, a family of two-dimensional (2D) transition metal carbides, carbonitrides, and nitrides, have emerged as a promising class of nanomaterials for interdisciplinary applications due to their unique physiochemical properties. The large surface area, excellent electrical conductivity, superior mechanical properties, and abundant possible functional groups make this layered nanomaterial an ideal candidate for multifunctional hybrid materials for electronic applications. This review highlights recent progress in MXene-based hybrid materials, focusing on their electrical, dielectric, and electromagnetic interference (EMI) shielding properties, with an emphasis on the development of multifunctionality required for advanced electronic devices. The review explores the multifunctional nature of MXene-based polymer nanocomposites and hybrid materials, covering the coexistence of a diverse range of properties, including sensory capabilities, electromagnetic interference shielding, energy storage, and the Joule heating phenomenon. Finally, the future outlook and key challenges are summarized, offering insights to guide future research aimed at improving the performance and functionality of MXene–polymer nanocomposites. Full article

This paper presents a novel ultrathin frequency selective surface (FSS) bandpass filter with an extraordinary wideband tailored for operating within the S-C bands. The filter structure entails a double-layer FSS structure with mutually perpendicular unit cells etched on the top and bottom sides of a 0.003${\lambda }_L$ thick FR4 dielectric substrate, where ${\lambda }_L$ is the free space wavelength at the lowest operating frequency. Thus, both TE and TM polarizations can be covered, ensuring the polarization insensitivity of the structure. The two FSS layers are loaded with resistors to implement the harmonic suppression principle. The overall periodicity is extremely compact, measuring 0.16${\lambda }_L$× 0.16${\lambda }_L$. An equivalent circuit analysis was conducted to comprehensively evaluate the structure and provide design guidelines. Numerical simulations and experimental measurements demonstrated that the proposed filter achieved a −3 dB transmission band spanning from 2 to 6.76 GHz (fractional bandwidth equal to 108.7%) under normal incidence. Moreover, aside from excellent wideband performance, the filter showcased a flat bandpass and stable responses up to 40° of incidence angle. These remarkable capabilities position the proposed filter as a valuable asset in advancing the development of radomes and applications relevant to electromagnetic interference (EMI) shielding, promising significant contributions to the field. Full article