Russian scientists from National Research Nuclear University MEPhI and Immanuel Kant Baltic Federal University have found a way how to reduce friction and thus increase the durability of surfaces in mechanisms. This was done with the help of thin films - layers of various materials up to several micrometers thick. It could be an important discovery for many areas - from medicine to space technology. The study was supported by the Russian Science Foundation and was published in Nanomaterials journal.
“Thin films are layers of substances that can be several atomic layers thick. Moreover, their properties differ significantly from the properties of the original substances on a macroscale. The field of application such films is constantly expanding, especially when updating the problems of nanoelectronics, optoelectronics, spintronics, electro- and photocatalysis, — said Vyacheslav Fominsky, scientific director of the project from MEPhI. — It is also worth highlighting such important sectors of the economy as space and instrument engineering. A promising developing area is the development of micromodular mechanisms for spacecraft, medical technology, instrument making”.
To solve the problem related to decreasing the coefficient of friction scientists can use metal chalcogenides — compounds of transition metals with sulfur, selenium, and tellurium. First researches on obtaining thin films from such materials were conducted in the 80-s of the twentieth century: researchers were attracted by the ability to modify materials properties when changing the structure and thickness of the deposited layer. In the study, Russian scientists investigated films that consisted of four elements: molybdenum, sulfur, carbon, and hydrogen. Laser pulses of tens of nanoseconds directed at carbon and molybdenum targets and accordingly created plasma streams from these materials. After that, carbon and molybdenum in the gas phase reacted with hydrogen sulfide previously pumped into the experimental chamber, and the product was deposited on a steel substrate. Chemically active sulfur and hydrogen atoms also could penetrate the growing coating. Together, the atoms formed a thin film on the metal, the properties of which significantly depended on the components concentration and the modes of the laser-plasma flow.
This approach is called pulsed laser deposition. It allows scientists to create smoother and more indistinguishable layers and change many parameters under experimental conditions, which also affects the coating structure in the final version. This is a very powerful tool for creating unique nanostructures, which is actively developing in some research centers (including MEPhI and IKBFU).
As a result, scientists received coating with a thickness of about 0.5 micrometers which reduce the coefficient of friction by more than ten times: the coefficient of friction during sliding of a steel ball on a steel plate without the use of traditional liquid lubrication did not exceed 0.03 when tested under normal conditions and -100 ° C. Skates sliding on ice have the same parameters.
Source: Indicator
