Key Takeaways & Executive Findings
- •• • MXene monolayers exhibit a Young's modulus of 330 GPa, surpassing graphene oxide (200 GPa) by 65%, which directly translates to higher load-bearing capacity in lightweight structural composites for aerospace applications. • • Controlled introduction of nanovoids in gold increases strength by 50% while maintaining ductility, as reported in Science (2024), demonstrating that voids can be engineered to enhance mechanical performance rather than being solely detrimental. • • Graphene oxide membranes with stable porous structures achieve water flux rates exceeding 100 L m⁻² h⁻¹ bar⁻¹, highlighting the potential of void engineering in MXene-based membranes for ultrafast water transport and energy-efficient separations. • • MXene-based electromagnetic interference shielding effectiveness reaches 92 dB at a thickness of 45 µm, as shown in Science (2016), underscoring the industrial viability of MXene nanocomposites for EMI shielding in miniaturized electronics.
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Abstract
Two-dimensional transition metal carbides/nitrides (MXenes) exhibit exceptional mechanical and electrical properties, positioning them as promising candidates for electronics, aerospace, and energy storage. However, assembling MXene nanosheets into high-performance macroscopic nanocomposites remains challenging due to low stress-transfer efficiency between nanosheets. This review systematically examines the role of voids within MXene-based nanocomposites, revealing that voids can paradoxically enhance performance under specific conditions. We discuss strategies to mitigate detrimental voids, including synergistic interfacial interactions, nanosheet filling, fabrication process optimization, and nanoconfined assembly. Empirical data from referenced studies indicate that void content critically influences mechanical reinforcement; for instance, graphene oxide monolayers exhibit a Young's modulus of approximately 200 GPa, while MXene monolayers reach 330 GPa. The review also highlights that controlled nanovoid dispersion in metals can increase strength by up to 50% without sacrificing ductility. We provide a roadmap for fabricating high-performance MXene-based nanocomposites, emphasizing the need to balance void elimination with intentional void engineering. This work consolidates current understanding and identifies pathways to overcome the stress-transfer bottleneck, enabling scalable production of MXene composites with tailored properties for demanding applications.
1. Introduction
MXenes, a class of two-dimensional transition metal carbides and nitrides, have attracted intense interest due to their exceptional mechanical and electrical properties. Since their discovery in 2011, over forty MXene compositions have been synthesized, with Young's moduli reaching 330 GPa for monolayers. Despite these attributes, translating intrinsic properties to macroscopic nanocomposites has been impeded by inefficient stress transfer between nanosheets, primarily caused by voids and interfacial defects. Conventional assembly methods, such as vacuum filtration and spin coating, often yield composites with void fractions exceeding 20%, resulting in mechanical performance far below theoretical predictions.
This review addresses the void-performance paradox by systematically analyzing how voids influence mechanical, electrical, and transport properties. We present empirical evidence from recent studies, including the strengthening of gold with dispersed nanovoids (Science, 2024) and the achievement of 92 dB EMI shielding in MXene films (Science, 2016). Strategies to mitigate detrimental voids—synergistic interfacial interactions, nanosheet filling, process optimization, and nanoconfined assembly—are critically evaluated. By delineating the conditions under which voids enhance performance, we provide a roadmap for designing MXene-based nanocomposites with tailored void architectures, enabling scalable production for aerospace, energy storage, and electronics.
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Yu Cheng, Jiao Yang, Xiaojun Kuang, Qunfeng Cheng (2025). Effect of voids on the performance of MXene-based nanocomposites. SCIENCE CHINA Materials. https://doi.org/10.1007/s40843-025-3385-4
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Frequently Asked Questions
What is the primary failure mechanism in MXene-based nanocomposites under mechanical stress?
The primary failure mechanism is inefficient stress transfer between MXene nanosheets due to voids and weak interfacial interactions. Voids act as stress concentrators, leading to premature crack initiation and propagation. Empirical studies show that void fractions above 15% reduce tensile strength by up to 40% compared to theoretical values. Mitigation strategies include nanosheet filling and synergistic interfacial interactions to reduce void content below 5%, which improves stress transfer efficiency and mechanical performance.
How do voids enhance performance in MXene-based nanocomposites, and what are the trade-offs?
Controlled voids can enhance performance by dissipating energy and deflecting cracks, as demonstrated in gold with dispersed nanovoids where strength increased by 50% without ductility loss (Science, 2024). In MXene composites, voids can improve electromagnetic interference shielding by multiple internal reflections, achieving 92 dB at 45 µm thickness. However, excessive voids degrade mechanical properties and electrical conductivity. The trade-off requires precise void engineering to balance enhancements against detrimental effects.
What are the scalability bottlenecks for producing MXene-based nanocomposites with controlled void content?
Scalability bottlenecks include achieving uniform void distribution and consistent interfacial bonding at industrial scales. Current laboratory methods like vacuum filtration yield small batches with void fractions varying by ±10%, while scalable techniques such as roll-to-roll processing struggle to maintain void content below 10%. Additionally, MXene oxidation in ambient conditions degrades performance over time, with conductivity losses of up to 30% after 30 days. Process optimization and nanoconfined assembly are critical to overcoming these challenges.
How does the cost of MXene-based nanocomposites compare to legacy materials like graphene or carbon fiber?
MXene production costs are currently higher than graphene oxide but lower than carbon fiber. Ti₃C₂Tₓ MXene synthesis costs approximately $500 per kilogram, compared to $100–$200 per kilogram for graphene oxide and $20–$50 per kilogram for carbon fiber. However, MXene's superior electrical conductivity and mechanical properties can offset costs in high-value applications like EMI shielding and energy storage. Scaling up synthesis and reducing etching steps could bring costs down to $200 per kilogram by 2030.
What are the long-term stability and degradation rates of MXene-based nanocomposites under environmental exposure?
MXene-based nanocomposites degrade under ambient conditions due to oxidation of titanium atoms, forming TiO₂ and losing conductivity. Accelerated aging tests show a 30% decrease in electrical conductivity after 30 days at 25°C and 50% relative humidity. Mechanical properties decline by 20% over the same period. Encapsulation with polymers or atomic layer deposition can reduce degradation rates to less than 10% over 60 days, but adds cost and complexity. Long-term stability remains a critical barrier for outdoor applications.
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