Investigation of Graphene Reinforced Polymer Composite Materials for Electromagnetic Interference Shielding Applications

Abstract

We have seen a sharp increase in the development of innovative electronic gadgets and a subsequent drive towards the miniaturization of electronic interfaces. Electromagnetic interference (EMI), which adversely affects the functionality of any electronic equipment that transmits, distributes, or consumes electrical energy, is produced by all electronic devices. If adequate shielding is not provided, this rise in unrestrained EM pollution could also impact people's health and the environment around them. In recent decades, several EM absorbers have been developed; these include ferritic paints, ferrite pads, metals, metallic architectures, and more. While each is effective in specific ways, they have significant flaws, including corrosion, heavy structures, reflection-driven mechanisms, and others. Because they overcome all the shortcomings of the earlier listed materials, polymer nanocomposites have quickly emerged as potential EM absorbers. For EMI shielding applications requiring various fillers, Acrylobutryo nitrile styrene (ABS) based nanocomposites have been researched among numerous nanocomposites. Microwave radiation is synergistically absorbed in these systems because of the heterogeneous dispersion of conducting and magnetic nanoparticles in the polymer matrix. However, materials made from these nanocomposites frequently need fixing, like a high filler loading and a large thickness, which prevents them from being used in sophisticated, high-end applications. Because of their unique characteristics of thermal stability, chemical resistance, thermal endurance, electrical conductivity, and low weight, graphene-reinforced composites are prospective candidates for various applications. Composites are crucial for business because of these advantages. There are several studies have been reported on the EMI shielding property of graphene composites, but still, we have room to explore the EMI shielding property by varying the different materials, thickness and by surface modification, etc. This thesis, "Investigation of graphene reinforced polymer composite materials for electromagnetic interference shielding applications” is explored and features systematic studies of fundamental requirement properties to sort out the challenges. Additionally, carbonaceous nanomaterials like graphene oxide (GO) and multiwalled carbon nanotubes (MWCNT) have been employed as interconnects to improve the electrical, mechanical, and thermal behavior of rGO/ABS composite to target the main qualities necessary for successful shielding. There are seven chapters in this thesis. Chapter 1 covers all the essentials of EMI shielding (mechanisms, factors), particularly on thermoplastic polymer composite materials, which have a sizable market for EM absorbers. This chapter covers the different carbonaceous inclusions that serve as interconnects, and highlights GO surface modification's essential role and the many inclusions that improve interfacial adhesion. This chapter divided the case study into several systems depending on the filler materials used, including carbonaceous materials, ferrites, metal oxides, dielectric and semiconducting nanostructured materials combined with carbonaceous materials, as well as metallic nanowire and nanosphere-based thermoplastic polymer nanocomposites. We have covered the most recent cutting-edge multi-layer/sandwich manufacturing processes, which have drawn much interest because of their improved shielding qualities. Chapter 2 covers the preliminary material-matrix characteristics, experimental setup, technique used to conduct the tests, and some preliminary optimizations. It also explains the apparent scientific rationale for selecting polymethyl methacrylate (PMMA), acrylonitrile butadiene styrene (ABS), and multiwall carbon nanotube for the EM shield design used throughout this thesis. Chapter 3 describes the effect of MWCNT on polymer composites electrical conductivity was established, this chapter discusses how GO can be functionalized in different ways to increase electrical conductivity and interfacial adhesion. It summarizes the essential role of GO, which has been explored due to the several functional groups, such as carbonyl, hydroxy, ether, epoxy, etc., present on the surface of GO. The composite materials of thermal, functional, morphological, and shielding performance were carried out. MWCNT composite shows higher SE due to their high conducting property, and rGO shows higher SE than GO due to the effective removal of functional groups in the reduction process, indicating that materials with high conductivity show higher SE relative to lower conducting materials. On the other hand, composite degradation was seen with increasing filler in PMMA composites beyond 5 wt% loading. This resulted in a drawback to introducing different fillers in PMMA simultaneously. Hence, we changed the polymer matrix from PMMA to ABS since ABS is a high-density polymer with excellent dispersing ability, wide processing temperature, and good thermal resistance. Due to high density, we can disperse higher weight percent of fillers without affecting the polymer nature so that we can explore different aspects and designs of shield materials in polymer composites and keep the rGO and effective functionalization of GO with different materials such as magnetic semiconducting and dielectric materials. In Chapter 4, we synthesized the magnetic materials barium and strontium hexaferrites using the nitrate-citrate gel combustion method, followed by in situ polymerization with PANI to form PANI-coated hexaferrites. Structural and morphological properties of the prepared compounds were studied using XRD and SEM characterization techniques. rGO synthesized from modified Hummer's method, these materials were incorporated in the ABS matrix, and their EMI shielding efficiency was analyzed. The addition of rGO resulted in an increased SET value for both BaFe12O19-PANI and SrFe12O19-PANI composites by eddy loss, which arises from the interaction of the conducting rGO, PANI-coated hexaferrites and MWCNT with the magnetic component of EM waves. Increased SET value of both the rGO/BaFe12O19-PANI and rGO/SrFe12O19-PANI composites is also aided by interfacial polarization and multiple reflections within the network formed in the composites. Chapter 5 deals with the ferromagnetic rGO-Fe3O4 and metallic La4BaCu5O13.10. GO layers are functionalized by ferrite nanoparticles using the one-pot hydrothermal method. The prepared nanomaterials were incorporated into an ABS polymer matrix with different weight ratios and uniform thickness. Prepared polymer films were further analyzed for their shielding ability, and their shielding mechanism was studied; the understanding of the mechanism of shielding provides an ability to choose different fillers for different EM applications, and it also provides an insight into designing shielding materials to achieve maximum shielding ability by blending different filler materials. In Chapter 6, the essential character of GO was explored by the effective functionalization of barium titanate and zinc oxide nanoparticles on functional groups such as carboxylic, hydroxy, and epoxide groups. We developed polymer composite sheets embedded with rGO-BaTiO3 and rGO-ZnO coupled to a conductive MWCNT network. By varying the weight ratio and thickness, SET was calculated. The maximum SE obtained for the developed composites is 59.8 dB for rGO-BaTiO3 composites and 57.9 dB for rGO-ZnO composites. The attenuation of many electromagnetic wave reflections was made possible by multicomponent composites. The composite films showed excellent compatibility and a synergetic augmenting effect from the multicomponent conductive network of rGO sheets and nanoparticles that benefited from impedance matching, showing the potential for use in electronics, electromagnetic countermeasures, and stealth materials. Chapter 7 presents the outcome of current work and summarizes the key outcomes of several studies performed. Future direction and extension of this work are also discussed in this chapter.