An extensive review on bibliometric analysis of carbon nanostructure reinforced composites M.A. Shadab Siddiqui , M.A. Mowazzem Hossain * , Ramisa Ferdous , M.S. Rabbi , S.M. Samin Yeasar Abid Department of Mechanical Engineering, Chittagong University of Engineering and Technology, Chattogram, 4349, Bangladesh A R T I C L E INFO Keywords: Metal matrix composites (MMCs) Carbon nanostructures (CNTs/Graphene) Reinforcement materials Bio-composites ABSTRACT The rapid evolution of the mechanical industry necessitates reliable and innovative materials. Metal matrix composites (MMCs) have emerged as a leading contender for performing vital roles in this field. Carbon nano- structures, such as graphene and carbon nanotubes (CNTs), are particularly well-suited as reinforcement ma- terials in MMCs. It has been found by recent experimental studies that incorporating CNTs and graphene as reinforcements into metal matrix composites, such as aluminum, magnesium, titanium, nickel, and copper matrices, can significantly enhance the mechanical, thermal, and tribological properties of these materials. This is achieved through various mechanisms, including the restriction of grain growth, hindrance of dislocations, load transfer at interfaces, and mitigation of thermal expansion mismatch. The precise reinforcement and optimization of fabrication techniques have opened up new avenues for achieving uniform nanostructure dispersion and strong interfacial bonding, leading to substantial improvements in quantitative properties. Such advancements in material science hold great promise for the development of high-performance materials with enhanced properties that are vital for various applications, including aerospace, automotive, biomedical, and beyond. The addition of low-carbon nanostructures to polymer matrix, ceramic, and biocomposite systems has also been observed to elicit noteworthy multifunctional improvements. Reinforcing collagen with CNT fibers leads to better mechanical and electrical performance compared to using collagen alone. This critical review provides an insightful and data-driven analysis of the current state of carbon nanostructure (CNTs/graphene)- reinforced metal matrix and biocomposites based on an extensive literature evaluation. The review includes an in-depth examination of the optimized synthesis and processing techniques for CNTs and graphene MMCs, highlighting the impact of reinforcement on their mechanical, thermal conductivity, electrical conductivity, and functional properties. Continued work refining fabrication methods fully leverages their potent multi-functional enhancement capabilities. 1. Introduction Carbon, with its diverse allotropes, including diamond, graphite, fullerenes, carbon nanotubes (CNTs), and graphene, offers a wide range of properties suitable for various applications. The characteristics of various reinforcements utilized in MMCs are outlined in Table 1 [1]. Among them, CNTs and graphene possess exceptional mechanical, electrical, and thermal properties, making them a promising choice for reinforcement in nanocomposites [2]. CNTs were discovered in the 1990s and come in two forms: single-walled and multi-walled varieties, depending on the number of concentric graphene tubes [3]. Both have unique characteristics, including high flexibility and strength superior to carbon fibers. CNTs can carry molecules through pi-pi stacking, making them promising for applications in electronics, optics, and beyond [4]. Multi-walled carbon nanotubes (MWCNT), in particular, demonstrate enhanced thermal and electrical conductivity, improving aluminum alloy matrices through a synergistic strengthening mechanism [5]. This results in greater hardness, ductility, and resistance to fatigue and creep. The demand for lightweight, high-strength materials is increasing with applications in the automotive and aerospace industries. Traditional lightweight alloys, such as aluminum and magnesium, exhibit poor mechanical properties that nano-reinforcements can address [6–9]. CNTs exhibit extraordinary properties as they can reach hardness over * Corresponding author. E-mail addresses: mashadab002@gmail.com (M.A.S. Siddiqui), mowazzem@cuet.ac.bd (M.A.M. Hossain), ramisaferdousme@gmail.com (R. Ferdous), rabbi@ cuet.ac.bd (M.S. Rabbi), saminyeasar4@gmail.com (S.M.S. Yeasar Abid). Contents lists available at ScienceDirect Results in Materials journal homepage: www.sciencedirect.com/journal/results-in-materials https://doi.org/10.1016/j.rinma.2024.100655 Received 22 May 2024; Received in revised form 11 November 2024; Accepted 20 December 2024 Results in Materials 25 (2025) 100655 Available online 22 December 2024 2590-048X/© 2024 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).