2D MXenes: Tunable Mechanical and Tribological Properties

Introduction

MXenes have rapidly emerged as one of the most exciting classes of advanced materials in tribology, offering a unique combination of tunable chemistry, excellent mechanical properties, and remarkable friction and wear performance. In a recent TriboNet webinar, Professor Andreas Rosenkranz from the University of Chile provided a comprehensive overview of these two-dimensional materials and discussed how they are shaping the future of lubrication and surface engineering.

The webinar, titled “2D MXenes – Tunable Mechanical and Tribological Properties,” explored the origins of MXenes, their tribological mechanisms, recent advances in material design, and the challenges that must be addressed before widespread industrial implementation becomes possible.

As interest in advanced tribological materials continues to grow, MXenes are increasingly being viewed as a promising alternative to conventional solid lubricants and coating technologies. Readers unfamiliar with the topic may find additional background in TriboNet’s article, MXenes in Tribology, which provides an overview of the material family and its growing role in friction and wear reduction.

What Are MXenes?

MXenes are a family of two-dimensional transition metal carbides, nitrides, and carbonitrides derived from layered ceramic compounds known as MAX phases. Through selective etching processes, specific atomic layers are removed, leaving behind atomically thin sheets with unique physical and chemical properties.

Since their discovery in 2011, MXenes have attracted enormous scientific interest because of their versatility. Unlike graphene, MXenes offer a wide range of compositional possibilities, allowing researchers to tailor their properties by varying transition metals, surface chemistry, and structural configurations.

Professor Rosenkranz explained that this tunability makes MXenes particularly attractive for applications ranging from energy storage and catalysis to biomedical technologies and tribology. Their layered structure provides low-shear characteristics similar to other well-known solid lubricants, while their rich surface chemistry creates opportunities for further performance optimization.

Why MXenes Matter for Tribology

One of the key themes throughout the webinar was the ability of MXenes to serve as more than simple solid lubricants.

Traditional lubricating materials often rely on low shear strength alone to reduce friction. MXenes, however, combine low-shear behavior with strong mechanical properties and active tribochemical responses during operation.

Professor Rosenkranz highlighted several features that contribute to their tribological performance:

• Layered crystal structures that facilitate sliding
• High mechanical strength
• Large specific surface area
• Strong adhesion to substrates
• Tunable surface chemistry
• Excellent tribofilm-forming capabilities

Together, these characteristics allow MXenes to reduce friction while simultaneously enhancing wear resistance and component durability.

Perhaps most importantly, MXenes actively participate in tribochemical processes during sliding contact. Rather than simply remaining unchanged during operation, they can transform and generate protective tribofilms that improve long-term performance.

Tribofilm Formation: The Key to Exceptional Performance

A major focus of the webinar involved the formation of tribofilms during sliding contact.

Professor Rosenkranz presented studies involving ultra-thin MXene coatings deposited onto stainless steel surfaces. Despite coating thicknesses of only around 100 nanometres, the materials demonstrated excellent durability during reciprocating sliding tests involving up to 100,000 cycles.

Microscopic characterization revealed that the coatings did not merely wear away. Instead, complex tribofilms formed at the contact interface. These tribofilms contained MXene fragments, oxide phases, and densified layered structures aligned with the sliding direction.

Interestingly, the tribofilms often exhibited superior mechanical properties compared to the original coating material. Increased hardness and improved load-bearing capability contributed significantly to wear protection.

Understanding exactly how these tribofilms form and evolve remains one of the most important research challenges facing the MXene community. TriboNet previously explored this topic in Challenges of MXenes in Tribology, which highlights several unanswered questions regarding tribofilm chemistry, durability, and performance mechanisms.

Beyond Titanium: Exploring New MXene Compositions

While titanium-based MXenes remain the most extensively studied systems, the webinar also highlighted exciting developments involving alternative compositions.

Particular attention was given to double transition metal MXenes, especially molybdenum-titanium systems. According to Professor Rosenkranz, these materials have demonstrated some of the most impressive tribological performance observed so far.

Experimental studies showed stable ultra-low friction behaviour over sliding distances approaching 86 kilometres. Researchers believe that tribocatalytic reactions occurring during sliding may promote the formation of highly ordered carbon structures, helping maintain exceptional lubrication performance over extended periods.

The webinar also addressed questions regarding other transition metals such as niobium and vanadium. While promising results have been reported in some situations, oxide formation remains a significant challenge that can negatively affect tribological performance.

These findings suggest that careful compositional engineering will play a critical role in the future development of MXene-based lubrication technologies.

Performance Under Extreme Conditions

Several audience questions focused on the ability of MXenes to operate under realistic engineering loads.

Professor Rosenkranz explained that MXene-based systems have demonstrated excellent performance under contact pressures approaching one gigapascal, with some applications reaching approximately 1.2 gigapascals.

Such pressures are representative of highly loaded mechanical components commonly found in industrial equipment and bearing systems.

The ability to maintain low friction and wear resistance under these demanding conditions represents a significant advantage for practical engineering applications. While many advanced materials perform well under laboratory conditions, fewer materials retain their effectiveness when subjected to the severe contact stresses encountered in real-world machinery.

MXenes in Bearings and Mechanical Components

One of the most compelling examples presented during the webinar involved rolling-element bearings.

Unlike many tribology studies that focus exclusively on simplified laboratory testing, these investigations examined how MXenes behave within complete mechanical systems.

Researchers observed that MXene coatings applied to a single raceway gradually transferred throughout the bearing assembly during operation. This process allowed protective tribofilms to form on balls, cages, opposing raceways, and other contact surfaces.

As a result, the beneficial effects of the MXene material extended beyond the originally coated area, effectively protecting the entire tribological system.

In some cases, the performance exceeded that of established solid lubricant technologies such as molybdenum disulfide and diamond-like carbon coatings, highlighting the considerable potential of MXenes for industrial applications.

Environmental Considerations and Safer Synthesis Methods

As MXene research progresses toward commercialization, environmental and safety considerations are becoming increasingly important.

Professor Rosenkranz acknowledged that traditional MXene synthesis often relies on hydrofluoric acid, which presents significant handling and safety challenges. However, considerable effort is being devoted to developing safer production routes.

Emerging alternatives include molten salt etching, electrochemical synthesis, and other approaches that reduce or eliminate the need for highly hazardous chemicals.

Readers interested in recent developments in this area may find TriboNet’s article on Direct Synthesis of MXenes particularly informative, as it explores new pathways that could simplify production and improve scalability.

Questions regarding toxicity and environmental impact were also raised during the discussion session. While research remains ongoing, Professor Rosenkranz noted that MXenes have demonstrated promising biological properties in several studies, including antibacterial and antiviral behaviour. Nevertheless, comprehensive life-cycle assessments and long-term environmental studies remain important areas for future investigation.

Future Research Directions

The webinar concluded with a discussion of future opportunities and remaining challenges.

Despite impressive progress, several obstacles still need to be addressed before MXenes achieve widespread commercial adoption. These include manufacturing costs, oxidation resistance, environmental stability, large-scale production, and long-term durability.

Many of these challenges are discussed in greater detail in TriboNet’s article Challenges of MXene-Based Nanomaterials for Tribological Applications, which outlines key research priorities for the field.

Professor Rosenkranz highlighted chemical functionalization as one of the most promising future directions. By modifying surface chemistry, researchers can tailor hydrophilicity, oxidation resistance, adhesion characteristics, and compatibility with various lubricants and polymers.

Additional research areas include defect engineering, hybrid MXene structures, and high-entropy MXenes, all of which offer exciting opportunities for further performance enhancement.

Conclusion

The TriboNet webinar “2D MXenes – Tunable Mechanical and Tribological Properties” provided a fascinating insight into one of the most rapidly evolving areas of tribology research.

From ultra-thin coatings and protective tribofilms to highly loaded bearing systems and chemically engineered lubrication materials, MXenes continue to demonstrate remarkable versatility and potential. Their combination of tunable chemistry, strong mechanical performance, and unique tribochemical behaviour positions them as serious contenders for next-generation tribological technologies.

While challenges related to manufacturing, stability, and commercialization remain, the progress highlighted throughout the webinar suggests that MXenes are steadily moving from laboratory research toward practical engineering implementation. As research continues to advance, these materials may play an increasingly important role in improving efficiency, durability, and sustainability across a wide range of mechanical systems.