The challenges associated with inhomogeneous distribution, poor interfacial interaction, and agglomeration of graphene sheets in sintered metal composites restrict its effectiveness in improving mechanical and physical properties. This study devised a grafting protocol for attachment of metal oxides on graphene nanoplatelets (GNPs) to investigate its effect on dispersion and interaction with Cu matrix. GNPs were sonicated to enhance its functionalization without a considerable change in defect ratio followed by grafting of Cu2O nanoparticles on GNPs employing a co-precipitation protocol. XPS, Raman spectroscopy, XRD, FTIR, FESEM confirmed the successful growth of homogenously distributed Cu2O nanoparticles on GNPs. Subsequently, the interaction of Cu2O grafted GNPs with copper matrix was explored using powder injection molding (PIM). Microstructural analysis showed restricted agglomeration, improved distribution of GNPs in copper matrix, and most importantly, bridged interaction between bulk copper and graphene in sintered samples. Furthermore, the densification can still be improved by optimizing the sintering process.

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The Sigma Aldrich supplied GNPs with lateral size 15 µm, thickness 6-8 nm and less than 1% oxygen content. The morphology of the GNPs provided by the manufacturer is illustrated in Fig. 1. The solvents used in this study include: Ethanol 95% from HmbG Chemicals, Hydrazine monohydrate 80%, Copper sulfate pentahydrate (CuSO4.5H2O), Toluene (97%), 1-N-Methyl-2-pyrrolidone (NMP 99%), and Dimethylformamide (DMF 97%) are purchased from R & M chemicals Malaysia. Copper acetate monohydrate (C4H6CuO4.H2O) with more than 98% purity from Acros, Fisher Scientific, was used. Moreover, Millipore ultrapure water with resistivity =15 O.m was used during all experiments. Gas atomized copper powder with D90 of 17.19 µm, and 99.95% purity from Sandvik Osprey Ltd., UK, was used to prepare feedstock. The particles of copper powder are spherical, as shown in Fig. 1. The binder system consists of Stearic acid (SA) from HmbG Chemical, Germany. High-density polyethylene (HDPE) was obtained from Optimal Chemicals Sdn. Bhd. Moreover, Paraffin wax (PW) from Abby Chemicals Pvt. Ltd., India, was used for feedstock preparation.

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Advancement in Materials Science: It offers a comprehensive review of various processing routes and their effects on the mechanical and physical properties of graphene/Cu composites, thereby advancing the understanding of material behavior and performance.

Technical Innovations: The study introduces a grafting protocol using Cu2O nanoparticles to improve the interfacial bonding between graphene and the Cu matrix, which is a significant advancement in composite material fabrication.

Contribution to Research: The article synthesizes and builds upon existing research, presenting a holistic view of the current state and future directions for graphene-reinforced MMCs.

Industrial Applications: The research points to the potential use of graphene/Cu composites in a wide range of industries, including electronics, aerospace, automotive, and thermal management systems.

Economic and Environmental Benefits: The development of high-performance composites can lead to longer-lasting products, reducing the need for frequent replacements and thereby lowering overall costs.

Pathway for Future Research: The article identifies challenges and proposes solutions, such as the use of highly reducing atmospheres to achieve maximum densification of composites. This provides a clear pathway for future research to further optimize these materials.

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Likewise, the Vickers hardness, calculated Brinell hardness and calculated tensile strength of composite at different weight percentages of Cu2O-GNP are presented in Table 2. One possible reason for lower density, hardness and tensile strength can be the restricted interaction between bulk Cu particles due to the presence of Cu2O-GNP nanoparticles at the Cu grain boundaries, thus limiting particle growth and hence consolidation during sintering [55,56]. Another reason could be the hinderance in diffusion of bulk Cu particles caused by increased oxygen content due to grafted Cu2O nanoparticles on GNPs. The difference in the theoretical and sintered densities may be reduced by sintering in H2 environment to avoid possible oxidation of bulk Cu powder during sintering cycle which acts as a barrier to complete densification. Moreover, the reducing environment may aid in reduction of Cu2O to Cu nanoparticles grafted on GNPs and enhance the diffusion of bulk Cu particles with Cu nanoparticle attached to GNP to achieve higher mechanical and physical properties of the sintered composite compared to pure Cu. This study has identified that sintering atmosphere with 95%Ar-5%H2 is not giving the desired densification of Cu2O-GNP reinforced Cu matrix composites for property enhancement due to the presence of Cu2O nanoparticles attached to GNPs. Maximum densification and enhancement in mechanical properties can be achieved by sintering in highly reducing atmosphere i.e., 100% H2 atmosphere which minimizes the oxide formation. Thus, the potential of homogenously distributed Cu2O-GNP nanoparticles in Cu matrix can be explored by optimizing the sintering parameters, more specifically the reducing sintering atmosphere.

High-Performance Material Demand: The article emphasizes the enhanced mechanical and physical properties of graphene/Cu composites. Industries such as aerospace, automotive, and electronics are continuously seeking materials that offer high strength, lightweight, and excellent thermal and electrical conductivity.

Technological Advancements:The study details various advanced processing techniques like sonication, ball milling, and powder injection molding (PIM), which are crucial for achieving uniform dispersion of graphene in the Cu matrix and enhancing interfacial bonding. The development of these sophisticated methods can lead to scalable production of high-quality composites.

Innovation in Materials Science: The continuous research and development in the field of nanomaterials, as illustrated by the various studies cited in the article, indicate a strong innovation pipeline. This can lead to new applications and improved performance of existing products.

Market Growth and Trends: The global market for metal matrix composites is expected to grow, driven by the increasing adoption of lightweight and high-strength materials. The specific niche of graphene-reinforced composites is likely to benefit from this trend, given graphene's exceptional properties.