Investigadores de la Missouri University of Sc & Tech, junto a otras instituciones, han realizado ensayos con Carburo de Titanio MXene, el que demostr\u00f3 poseer propiedades \u201csuperlubricantes\u201d, especialmente aptas para su empleo en ambientes sin ox\u00edgeno y libres de humedad.\u00a0 El descubrimiento\u00a0 permitir\u00eda, seg\u00fan los investigadores, la utilizaci\u00f3n de esos materiales en estado s\u00f3lido como lubricante, con la finalidad de reducir el desgaste de los veh\u00edculos empleados en la superficie del planeta Marte y multiplicidad de futuras aplicaciones.<\/p>\n
Titanium carbide MXene exhibits superlubricant properties on the macroscale in oxygen- and humidity-free environments, US researchers have found. The finding, the team said, means the material could be a new solid lubricant to reduce wear and tear on future Mars rovers.<\/p>\n
First described in 2011, MXenes \u2013 pronounced \u2018maxines\u2019 \u2013 are a class of two-dimensional, layered metal carbide materials that have attracted attention for their conductive properties \u2013 and have been proposed for applications in energy storage and harvesting, sensor design and optoelectronics. Recent studies, however, have found that MXenes also have potential for use as solid lubricants \u2013 however, until now, none had demonstrated superlubricity on the macroscale.<\/p>\n
Chemist Vadym Mochalin<\/a> of the Missouri University of Science & Technology and colleagues in collaboration with the Center for Nanoscale Materials at Argonne National Laboratory\u00a0created the materials by depositing a titanium carbide MXene onto a silicon substrate coated with a thin layer of silica. They then tested friction and wear resistance of the material by sliding it against a diamond-like carbon-coated steel ball.<\/p>\n The tests were all undertaken in a dry nitrogen environment, to reduce humidity. This was necessary because \u2013 unlike bulk transition metal carbides, which are typically inert \u2013 their two-dimensional forms are, as Mochalin explained, \u2018quite reactive and susceptible to hydrolysis, reactions with oxygen and potentially with other reagents\u2019.<\/p>\n The team found that adding graphene to the titanium carbide MXene \u2018further reduced the friction by 37.3% and wear by the factor of two\u2019. Such a combination, the team said, is \u2018substantially\u2019 better than oil-based lubricants.<\/p>\n \u2018When I watched the landing of the rover on Mars, I thought: \u201cWhat if the lubricant in one of its wheels fails?\u201d Then I made the connection with our work on MXenes, because it came to mind that we have just found that MXenes demonstrate superlubricity in an atmosphere devoid of oxygen and humidity, close to what is there on Mars,\u2019 Mochalin says.<\/p>\n Alongside reducing friction in the final frontier \u2013 from exploratory rovers to future asteroid mining machinery \u2013 MXenes could also find terrestrial applications.<\/p>\n \u2018As long as MXenes are protected in one way or another from direct contact with wet air \u2013 for example by applying a coating made of graphene, as we have demonstrated in our research, or of other similar materials \u2013 they should work,\u2019 Mochalin explains. Unlike oil-based alternatives, he adds, MXene lubricants have an added advantage in that they do not rely on non-renewable resources like crude oil.<\/p>\n Why MXene has super-lubricating properties, however, remains an open question. \u2018We hypothesised about a few mechanisms, which can be related to functional groups on MXene surfaces and intercalated species, as well as the nature of the material itself, but at this stage there is little we can say with certainty,\u2019 Mochalin says.<\/p>\n \u2018MXenes have shown many marvelous properties and brought many surprises in the past decade, and here the authors show the ability to greatly decrease the friction by using two-dimensional flakes of MXene,\u2019 comments Drexel University materials scientist Yury Gogotsi<\/a>, whose team discovered MXenes. The finding, he adds, is \u2018scientifically interesting and technologically important\u2019.<\/p>\n \u2018While the reported friction mitigation capabilities are impressive, much work needs to be done to evaluate the suitability of MXenes for actual space missions, in particular with regards to their robustness against changes in environmental conditions,\u2019 adds Mehmet Baykara<\/a>, a mechanical engineer from the University of California, Merced who was also not involved in the present study.<\/p>\n