Metal matrix nanocomposites reinforced with graphene have emerged as a promising class of materials due to their exceptional mechanical, thermal, and electrical properties. These composites combine the ductility and processability of metals with the high strength and conductivity of graphene, making them suitable for demanding applications in aerospace, automotive, and electronics. The fabrication of these materials involves several key techniques, each with advantages and limitations, while the interfacial interaction between graphene and the metal matrix remains a critical factor in determining performance.

Fabrication techniques for graphene-reinforced metal matrix nanocomposites primarily include powder metallurgy and stir casting. Powder metallurgy involves blending metal powders with graphene, followed by compaction and sintering. This method allows for uniform dispersion of graphene within the matrix, which is essential for maximizing reinforcement efficiency. Mechanical alloying is often employed to achieve a homogeneous mixture before consolidation. Hot pressing or spark plasma sintering enhances densification, reducing porosity and improving interfacial bonding. For example, aluminum-graphene composites produced via powder metallurgy have demonstrated a 50% increase in tensile strength compared to unreinforced aluminum, attributed to effective load transfer from the matrix to graphene.

Stir casting is another widely used method, particularly for light metals such as aluminum and magnesium. In this process, graphene is dispersed into the molten metal using mechanical stirring, followed by solidification. The challenge lies in preventing graphene agglomeration due to poor wettability between graphene and molten metals. To address this, surface modification of graphene or the use of surfactants improves dispersion. Magnesium-graphene composites fabricated via stir casting exhibit enhanced thermal conductivity, reaching up to 120 W/mK, a 30% improvement over pure magnesium, due to the high intrinsic thermal conductivity of graphene.

The role of graphene in enhancing tensile strength is primarily due to its high elastic modulus and large surface area. Graphene acts as a barrier to dislocation movement, strengthening the metal matrix through Orowan strengthening and load transfer mechanisms. Studies on copper-graphene composites reveal a yield strength increase of up to 60% with only 0.5 vol% graphene addition. The two-dimensional structure of graphene provides more efficient reinforcement compared to particulate or fiber reinforcements, as it restricts deformation across multiple planes.

Thermal conductivity improvements are another significant benefit of graphene reinforcement. Graphene’s high thermal conductivity, exceeding 3000 W/mK, facilitates efficient heat dissipation in metal matrices. Aluminum-graphene composites show thermal conductivity enhancements of up to 35%, making them ideal for thermal management applications such as heat sinks and electronic packaging. The percolation network formed by graphene platelets within the matrix enables rapid phonon transport, reducing thermal resistance at interfaces.

Despite these advantages, challenges persist in the development of graphene-reinforced metal matrix nanocomposites. Interfacial wettability between graphene and metals is a major issue, as poor adhesion limits load transfer efficiency. Oxidation of graphene during high-temperature processing further degrades performance. To mitigate these problems, researchers employ techniques such as in-situ reduction of graphene oxide within the metal matrix or the use of metallic coatings on graphene to improve compatibility. For instance, nickel-coated graphene exhibits better interfacial bonding with copper matrices, leading to a 20% higher tensile strength compared to uncoated graphene composites.

Applications of these nanocomposites are broad, particularly in thermal management and structural components. In electronics, copper-graphene composites are used for heat spreaders due to their high thermal conductivity and low coefficient of thermal expansion. Aerospace components benefit from the lightweight and high-strength properties of aluminum-graphene composites, which reduce fuel consumption while maintaining structural integrity. Automotive brake systems utilize graphene-reinforced metal matrices for improved wear resistance and heat dissipation.

Another critical application is in energy storage systems, where graphene-aluminum composites serve as current collectors in batteries, enhancing electrical conductivity and mechanical stability. The high surface area of graphene also promotes better electrode-electrolyte interaction, improving charge-discharge cycles. In addition, these composites are being explored for use in high-power electronics, where efficient thermal management is essential to prevent overheating and ensure device reliability.

Future developments in graphene-reinforced metal matrix nanocomposites will likely focus on optimizing fabrication processes to achieve scalable production while maintaining consistent quality. Advances in interfacial engineering, such as the development of novel coating techniques or alloying elements to enhance graphene-metal bonding, will further improve mechanical and thermal properties. Research into hybrid methods combining powder metallurgy and additive manufacturing may open new possibilities for complex geometries with tailored reinforcement distributions.

In summary, graphene-reinforced metal matrix nanocomposites offer a unique combination of strength, conductivity, and lightweight properties, making them highly attractive for advanced engineering applications. While challenges related to interfacial bonding and processing remain, ongoing research continues to address these limitations, paving the way for broader adoption in industries requiring high-performance materials. The successful integration of graphene into metal matrices represents a significant step forward in the development of next-generation composites.