A new two-dimensional nanomaterial, MXene, can also act as a lubricant in extreme temperatures or the vacuum of space

You can lubricate bicycle chains with oil, but what about hot conveyor belts in the steel industry or on Mars rovers? The Vienna University of Technology has now studied very special nanomaterials together with research groups from Saarbrucken (Germany), Purdue University in the United States and the University of Chile (Santiago, Chile).

In recent years, MXenes' material category (pronounced "maxene") has caused a stir in connection with new battery technologies. But now they are also proving to be an excellent solid lubricant, extremely durable and capable of performing their tasks even in the most difficult conditions. These superior properties of MXenes have now been published in the prestigious ACS Nano journal.

ust like the carbon material graphene, MXene falls into the category of so-called 2D materials: they are ultra-thin layers of single atoms and have no strong bonds to the upper or lower layers.



Professor Carsten Gachot, head of the tribology group at TU's Institute of Engineering Design and Product Development, says you first start with the so-called MAX stage, which is a system of special layers made up of titanium, aluminium and carbon. The key trick is to etch aluminum with hydrofluoric acid.



Then what's left is a bunch of atoms and thin layers of titanium and carbon that are loosely stacked together like pieces of paper. Each layer is relatively stable on its own, but the layers can easily move relative to each other.

This portability between atomic layers makes the material an excellent dry lubricant: sliding with very low resistance can be achieved without causing wear. As a result, the friction between the steel surfaces can be reduced to one-sixth, and the wear resistance is extremely high: the MXene lubrication layer still works properly even after 100,000 movement cycles.



This is ideal for use in difficult conditions: in space flight, for example, lubricating oil evaporates immediately in a vacuum, but MXene in fine powder form can also be used there.



It has nothing to do with atmosphere or temperature



Carsten Gachot says similar approaches have been tried for other thin film materials, such as graphene or molybdenum disulfide. But they respond sensitively to moisture in the atmosphere. Water molecules can change the bonding force between the layers. For MXene, on the other hand, it has less effect.



Another decisive advantage is the heat resistance of MXenes, as many lubricants oxidize and lose their lubricity at high temperatures. MXenes, on the other hand, is more stable and can even be used in the steel industry, where parts that sometimes move mechanically sometimes reach temperatures of several hundred degrees Celsius.



Dr Philip Grutzmacher of Professor Gachot's research group, together with the University of Saarbruken in Saarbruken and Purdue University in the US, studied the powder lubricant in several experiments at TU Wien. On the other side of the world, Professor Andreas Rosenkranz in Chile was instrumental in initiating and designing this work.



Carsten Gachot says there has also been significant interest in the materials from industry. We think this MXene can be mass-produced very quickly.