Alongside research partners from Saarbrücken University in Germany, Purdue University in the USA and the University of Chile, the team at TU Wien has published its findings in the journal ACS Nano.
The study highlights the potential for MXene to perform as a highly durable lubricant, able to withstand difficult conditions such as extreme heat or the vacuum of space. Like the carbon material graphene, MXenes are 2D materials whose properties are essentially determined by the fact that they are ultra-thin layers without strong bonds between them.
“You first start with so-called MAX phases, which are special layer systems consisting of titanium, aluminium and carbon,” said Professor Carsten Gachot, head of Tribology Group at the Institute of Engineering Design and Product Development at TU Wien. “The crucial trick is to etch out the aluminium with hydrofluoric acid.”
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By doing this, a stack of atomically thin layers of titanium and carbon that lie loosely on top of each other like pieces of paper remains. The layers are relatively stable on their own but can easily be shifted against each other — this is key to the material’s success as a lubricant, the team said, as ‘extremely low-resistance’ sliding is made possible without generating abrasion.
According to researchers, friction between steel surfaces could be significantly reduced with ‘exceptionally high’ wear resistance and the MXene still functioning well after 100,000 movement cycles. In the form of fine powder, the team said MXene could be used in a vacuum during space missions where an oil would evaporate.
“Similar things have been tried with other thin-film materials, such as graphene or molybdenum disulphide,” said Gachot. “But they react sensitively to moisture in the atmosphere. Water molecules can change the bonding forces between the individual layers.”
Gachot added that heat resistance is another advantage, as many lubricants oxidise at high temperatures and will lose lubricity. MXenes are more stable and could be used in the steel industry where mechanically moving parts can sometimes reach temperatures of several hundred degrees Celcius, he explained.
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