Silver Nanowires Coated Nitrocellulose Paper for High-Efficiency Electromagnetic Interference Shielding

A thin and conductive coating on an environmentally friendly polymer is imperative for protecting sensitive electronic devices. In this regard, a series of silver nanowires (AgNWs) coated nitrocellulose (NC) papers are fabricated by a simple and fast processed vacuum-assisted filtration method by varying filtrate volume to address electromagnetic interference. Their structural and EMI shielding performance is analyzed. The submicron thick and the lighter paper reveal the conductive AgNWs interwoven on the rough NC surface, making a 2D in-planar structure. Due to a strongly interconnected network, the coated paper displays an exceptional electrical conductivity of 8603 S/m. Despite having a minimum AgNW coating thickness of ∼0.69 μm and an area density of 0.041 mg/cm², an ultrahigh EMI shielding effectiveness (SE) of about 69.4 dB (a specific EMI SE (SE/t) of 1005797 dB/cm) in the entire X-band (8-12 GHz) region is achieved. The effective material parameters, extracted using plane-wave theory, indicate that AgNWs form closed current loops resulting in magnetic losses. These AgNWs coated NC papers synthesized by a simple procedure are promising EMI shielding materials for current emerging electronic devices.

Tuning the interface in epoxy-based composites and laminates through epoxy grafted graphene oxide enhances mechanical properties

Improved dispersion together with enhanced interfacial adhesion of the reinforcement is the key to superior structural properties in polymer nanocomposites. Herein, graphene oxide (GO) is employed to reinforce epoxy, and in order to improve the interfacial adhesion, epoxy chains were grafted directly onto GO prior to composite preparation. The functionalized GO sheets were systematically characterized using FTIR, TEM, Raman spectroscopy, XRD, and XPS. The epoxy composites with GO and epoxy grafted graphene oxide (Ep-g-GO) were prepared with the addition of only a small amount (0.5 wt%) of GO using a mechanical stirrer coupled to a bath sonicator. This strategy resulted in an impressive increase in mechanical properties, 40% in storage modulus, 70% in hardness, 39% in fracture toughness, and 8% in tensile strength, as compared to neat epoxy. In addition, the modified composites were thermally stable up to 300 °C as inferred from the thermogravimetric analysis. The enhanced properties of the composites further led to investigating the effect of Ep-g-GO on epoxy/carbon fiber (CF) laminates. Interestingly, incorporation of 0.5 wt% Ep-g-GO resulted in improved interfacial adhesion between GO and the epoxy matrix, which enhanced the tensile strength by 12% and inter-laminar shear strength by 9% as compared to neat epoxy/CF laminates. This study clearly demonstrates the positive effect of the tailored interface, offered by Ep-g-GO, on the mechanical properties of epoxy composites and epoxy/CF laminates.

Effect of MWCNTs Functionalization on Thermal, Electrical, and Ammonia-Sensing Properties of MWCNTs/PMMA and PHB/MWCNTs/PMMA Thin Films Nanocomposites

Partially biodegradable polymer nanocomposites Poly(3-Hydroxybutyrate) (PHB)/MultiwalledCarbon Nanotubes (MWCNTs)/Poly(Methyl Methacrylate) (PMMA)and non-biodegradable nanocomposites (MWCNTs/PMMA) were synthesized, and their thermal, electrical, and ammonia-sensing properties were compared. MWCNTs were chemically modified to ensure effective dispersion in the polymeric matrix. Pristine MWCNTs (p-MWCNTs) were functionalized with –COOH (a-MWCNTs) and amine groups (f-MWCNTs). Then, PHB grafted multiwalled carbon nanotubes (g-MWNTs) were prepared by a ‘grafting to’ technique. The p-MWCNTs, a-MWCNTs, f-MWCNTs, and g-MWCNTs were incorporated into the PMMA matrix and PMMA/PHB blend system by solution mixing. The PHB/f-MWCNTs/PMMA blend system showed good thermal properties among all synthesized nanocomposites. Results from TGA and dTGA analysis for PHB/f-MWCNTs/PMMA showed delay in T₅ (about 127 °C), T₅₀ (up to 126 °C), and T_max (up to 65 °C) as compared to neat PMMA. Higher values of frequency capacitance were observed in nanocomposites containing f-MWCNTs and g-MWCNTs as compared to nanocomposites containing p-MWCNTs and a-MWCNTs. This may be attributed to their excellent interaction and good dispersion in the polymeric blend. Analysis of ammonia gas-sensing data showed that PHB/g-MWCNTs/PMMA nanocomposites exhibited good sensitivity (≈100%) and excellent repeatability with a constant response. The calculated limit of detection (LOD) is 0.129 ppm for PHB/g-MWCNTs/PMMA, while that of all other nanocomposites is above 40 ppm.

Graphene templated growth of copper sulphide 'flowers' can suppress electromagnetic interference

With increasing usage of electronic gadgets in various fields, the problem of electromagnetic interference (EMI) has become eminent. To suppress this interference, lightweight materials that are non-corrosive in nature and easy to fabricate, design, integrate and process are in great demand. In the present study, we have grown copper sulphide 'flowers' on graphene oxide by a facile one pot hydrothermal technique. The growth time of the "flower-like" structure was optimised based on structural (XRD) and morphological analysis (SEM). Then, the as-prepared structures were dispersed in a PVDF matrix using melt blending. The bulk AC electrical conductivity and EMI shielding ability of the prepared composite were assessed, and it was observed that the nanocomposites exhibited an EMI shielding effectiveness up to -25 dB manifesting in 86% absorption of the incoming EM waves at a thickness of only 1 mm. Moreover, it was also observed that addition of hybrid nanoparticles has a better effect on the electromagnetic (EM) shielding performance compared to when the nanoparticles are added separately in terms of both total shielding effectiveness as well as absorption performance. A minimum skin depth of 0.38 mm was observed in the case of the hybrid nanostructure.

The journey of self-healing and shape memory polyurethanes from bench to translational research

In this critical review, we have enlisted a comprehensive summary of different approaches that have been used over the past decade to synthesize self-healing polyurethanes including “close then heal” and “shape memory assisted self-healing” concept.

Poly(ether ether ketone)-Grafted Graphene Oxide "Interconnects" Enhance Mechanical, Dynamic Mechanical, and Flame-Retardant Properties in Epoxy Laminates

Herein, the interface of epoxy and graphene oxide (GO) is tailored through hydroxylated poly(ether ether ketone) (HPEEK). The resultant modification (HPEEK-g-GO) improved the interfacial adhesion between epoxy and carbon fiber (CF) in the laminates. This strategy resulted in improved tensile strength, modulus, and storage modulus by 8, 10, and 26%, respectively, with respect to control samples (epoxy/CF laminates). The HPEEK-g-GO was thoroughly characterized using spectroscopic techniques and was infused using vacuum-enhanced resin infusion technology into the epoxy/CF laminates. To address the challenges involved with primary agglomeration, the composite formulation was subjected to mechanical stirring coupled with bath sonication throughout the mixing process. The improved structural properties in epoxy/CF laminates were attributed to HPEEK-g-GO "interconnects", which provided the necessary reinforcement owing to better interfacial adhesion with the CF mat as inferred from the fracture surface morphology assessed using SEM. In addition, the epoxy laminates containing HPEEK-g-GO also showed flame-retardant properties along with good thermal stability. The electromagnetic interference shielding capability of the modified laminates was also evaluated in the frequency range of 12-18 GHz. It was observed that the laminates exhibited a shielding effectiveness of -50 dB. Thus, this strategy offers some promise in fabricating epoxy/CF laminates with multifunctional properties through HPEEK-g-GO "interconnects".