Twinning for graphene-based composites in EMI shielding

In the era of intensive development of microelectronics, energy, and car industries along with Radio-Frequency (RF) telecommunications, the pollution caused by Electromagnetic Waves (EWs) is ever-present. EW interferences (Electromagnetic Interference-EMI) exhibit perturbation and negative impact on devices and systems including those used in everyday life as well as on the specialized, sensitive, and sophisticated instruments used in research laboratories. EMI could cause untrusted signals and RF noise. To prevent these issues, materials able to block or absorb the radiated EWs are urgently required. The GrInShield project is focused on developing new graphene-based shielding nano-materials and increasing researchers' expertise in EMI shielding measuring, protective materials, and possibilities to bring these new products to the market. INTRODUCTION: The GrInShield project uses graphene oxide (GO) obtained by Hummers' reaction and electrochemical exfoliation of graphite [1,2]. We have analysed the factors that affect the shielding efficiency of materials [3] and studied the reaction conditions that lead to obtaining graphene with different sizes and oxygen content [4]. RESULTS AND DISCUSSION: The GrInShield project aims to produce composites of GO with silver nanowires (AgNWs) to develop GO-AgNW composites for EMI shielding applications. To achieve these goals, the project gathers experts from the chemistry of nanomaterials, and polymer processing, along with specialists for near-field microscopy tools and radiofrequency (RF) characterization of materials. CONCLUSIONS: The GrInShield project is developing new nanomaterials for EMI shielding based on carbon nanomaterials, metallic nanomaterials, and polymers. The fabrication of low-cost, sustainable, eco-friendly, durable EMI shielding material should be achieved.Supplementary Issue - ExcellMater Conference 2024Innovative biomaterials for novel medical devices conference : AbstractsAvailable on-line at the Journal web address: [https://www.ache.org.rs/HI/

The morphology of pani/graphene composites prepared under isothermal conditions

This article investigates the morphology of polyaniline/electrochemically exfoliated graphene composites prepared by oxidative polymerization with ammonium persulfate at a constant temperature (15 °C). During the polymerization, the pH of the reaction mixture decreases, which was used to monitor the rate of the reaction. A granular morphology with the presence of large sheet-like structures is found to be predominant for the composite prepared without added acid, while rod-shaped and tubular morphology is characteristic for the composite prepared with the addition of glacial acetic acid. The nanotubular and nanorod morphology of the sample prepared with the addition of glacial acetic acid was also confirmed by the presence of prominent phenazine structural units in Raman spectra. The composite prepared with the addition of HCl has granular morphology with a small amount of rod-like structures

Graphene oxide-silver nanowires composites for protection against modern pollution - electromagnetic waves

With the development of the electronic industry, telecommunication, transportation, energy storage devices, and wireless technologies, the need for materials that are able to block electromagnetic waves (EMWs) in low-frequency regions of the spectrum is increasing. A new type of pollution named pollution by EMWs is an inevitable component of modern life. Although materials efficient in blocking the propagation of EMWs are developed, these materials show drawbacks regarding durability and mechanical properties, as well as a high production price and processability. Thus, new eco-friendly and durable materials are needed. Herein, we produced composites based on graphene oxide and silver nanowires to create an efficient shielding barrier for low frequencies (0-15 GHz) EMWs

A review on graphene and graphene composites for application in electromagnetic shielding

As wireless solutions for communication, information, and sensing in modern society, electromagnetic waves (EMWs) have contributed considerably to the increase in the quality of people’s everyday lives. At the same time, EMWs produce electromagnetic pollution, issues with electromagnetic interference (EMI), and radio frequency (RF) signal leakage. These circumstances lead to high demand for efficient EMI shielding materials. To design an EMI shielding product, a compromise must be achieved between the electromagnetic shielding efficiency, the thickness of shielding materials, durability, mechanical strength, reduced volume and weight, and elasticity. Due to its ability to block EMWs, flexibility, lightweight, and chemical resistivity, graphene has been identified as a promising candidate material for efficient EMI shielding. Herein, we reviewed the studies that investigated various graphene-based composites as potential EMI shielding materials, with a focus on the composites based on graphene and silver nanowires due to their high EMI shielding efficiency, low production price, and favorable mechanical properties

Measurement of EMI shielding performance of graphene oxide and electrochemically exfoliated graphene thin films

Graphene and its derivatives have become the scientific community's focus due to their remarkable electronic, mechanical, and optical properties. In this work, we prepared two graphene-based materials, graphene oxide (GO) and electrochemically exfoliated graphene (EEG), and performed morphological and structural analysis. Both materials showed good dispersibility in water. GO is composed of mainly single- and few-layer graphene sheets, while EEG is predominately multi-layer graphene. EEG showed better thermal stability under nitrogen flow compared to GO. We also performed ElectroMagnetic Interference (EMI) shielding performance measurements of these materials

The Influence of Reaction Conditions on the Properties of Graphene Oxide

The present study focuses on correlations between three parameters: (1) graphite particle size, (2) the ratio of graphite to oxidizing agent (KMnO4 ), and (3) the ratio of graphite to acid (H2SO4 and H3PO4 ), with the reaction yield, structure, and properties of graphene oxide (GO). The correlations are a challenge, as these three parameters can hardly be separated from each other due to the variations in the viscosity of the system. The larger the graphite particles, the higher the viscosity of GO. Decreasing the ratio of graphite to KMnO4 from 1:4 to 1:6 generally leads to a higher degree of oxidation and a higher reaction yield. However, the differences are very small. Increasing the graphite-to-acid-volume ratio from 1 g/60 mL to 1 g/80 mL, except for the smallest particles, reduced the degree of oxidation and slightly reduced the reaction yield. However, the reaction yield mainly depends on the extent of purification of GO by water, not on the reaction conditions. The large differences in the thermal decomposition of GO are mainly due to the bulk particle size and less to other parameter

The Morphology of Pani/Graphene Composites Prepared Under Isothermal Conditions

This article investigates the morphology of polyaniline/electrochemically exfoliated graphene composites prepared by oxidative polymerization with ammonium persulfate at a constant temperature (15 °C). During the polymerization, the pH of the reaction mixture decreases, which was used to monitor the rate of the reaction. A granular morphology with the presence of large sheet-like structures is found to be predominant for the composite prepared without added acid, while rod-shaped and tubular morphology is characteristic for the composite prepared with the addition of glacial acetic acid. The nanotubular and nanorod morphology of the sample prepared with the addition of glacial acetic acid was also confirmed by the presence of prominent phenazine structural units in Raman spectra. The composite prepared with the addition of HCl has granular morphology with a small amount of rod-like structures

DEPOLYMERISATION OF POST-CONSUMER PET BOTTLES WITH AMINOLYSIS IN THE PRESENCE OF ORGANOCATALYST

<p>Polyethylene terephthalate (PET) is a saturated polyester synthesized by the esterification of a dibasic acid (terephthalic acid) and a diol (ethylene glycol) and is used for fibres, bottles, films, and other moulded products. PET is recycled by both physical and chemical routes. The physical route generally consists of remelting and forming new products with the help of suitable additives. PET can be chemically reprocessed by complete depolymerisation into oligomers, monomers, and other by-products. In this way, a wide range of terephthalamide monomers can be produced, which can serve as building blocks for high-performance materials with desired mechanical and thermal properties. In this study, different amines (ethylenediamine - EDA, 1,4-diaminobutane - DAB, 1,6-diaminohexane - DAH) were used to depolymerise post-consumer PET beverage bottles. The bottles were cut into pieces with an edge length of less than 2 cm. Aminolysis of PET was carried out in the presence of organocatalyst (1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD)) and with an excess of amine (ethylenediamine, 1,4-diaminobutane, 1,6-diaminohexane; 1.5 and 3 eq.). After completion of the reaction the product was isolated, washed with organic solvents and dried. The products bearing amino functional groups were characterised by Fourier transform infrared spectroscopy (FTIR) and differential scanning calorimetry (DSC).</p&gt