Diamond-like carbon (DLC) coatings are, nowadays, used in various mechanical systems, including highly stressed and lubricated applications. However, a lot is still unknown about the interactions between lubricants and DLC coatings. For example, what is the role of base oil in DLC contact? Do base oils adsorb to the DLC surface, or are they only a passive element in the contact? In this study, self-mated DLC-DLC contacts were employed, and steel-steel contacts were used as a reference for the expected lubrication mechanisms, which are well known for steel. In tribological experiments, low velocity boundary lubrication conditions were applied to eliminate any velocity related effects. Low viscosity polyalphaolefin base oil was used as a lubricant, and some tests were made also without the use of the lubricant in the contact. Results showed that the friction of boundary lubricated DLC contacts is always lower than the friction of steel contacts. However, in the low speed boundary lubrication regime, the friction of the lubricated DLC contacts increased in comparison with the non-lubricated conditions, which is the opposite of steel behaviour. Nevertheless, oil was required to stabilise the friction behaviour and to prevent high wear and removal of the DLC coating.
COBISS.SI-ID: 11910683
We studied the friction properties of the MoS2 nanotubes and commercially accessible MoS2 and graphite crystals. On atomic level we compared these materials under ambient air conditions and in ultra-high vacuum (UHV). In bothcases we acquired the measurements with an atomic force microscope (AFM) in lateral force microscopy mode without application of any lubricant. In macroscopic conditions we used a conventional tribological tester and analysed friction properties of the three materials used as additives in base synthetic PAO oil. The AFM results show much higher friction in UHV conditionsthan in air with MoS2 nanoparticles providing the lowest friction inboth environments. MoS2 nanoparticles and micro-crystals provided similarly low friction in base PAO oil in initial stages of sliding, with nanoparticles assuring even slightly lower values. But as the sliding continued, the friction in experiments with oil containing micro-crystals decreased, while itincreased in the case of nanoparticles. These results are discussed on the basis of the friction and wear data and the surface analyses, which we performed using a scanning electron microscope.
COBISS.SI-ID: 12103707
The co-axial MoS2 nanotubes represent a unique family of nanomaterials and are presented in this study. Growth mechanism is discussed based on atomic probe electron microscopy, x-ray diffraction and high-resolution transmission electron microscopy. This report then focuses on the application potentials of these unique nanotubes. The authors observed exfoliation phenomena of these nano-layered materials and found that the exfoliation of MoScan lead to the synthesis of many new materials in combination for example, with organic molecules. It was discovered that MoS2 photoluminescence holds promise for new nanophotonic applications, and the new material was also proposed to design a field-effect transistor, which can be applied in new areas of optoelectronics. These inorganic nanotubes were furthermore studied as host materials for electrodes of rechargeable batteries. MoS2is also known as a solid lubricant which has been used in the industry for the last 60 years. The problem of edge oxidation and preservation of the flakes in parallel orientation with the surface with a low degree of restacking can be minimized with the reduction of thickness. So it is desired to obtain the thinnest flakes possible, which can be achieved by exfoliating MoS2 coaxial nanotubes. The beneficial tribological properties of the MoS2 nanotubes in various systems are also presented.
COBISS.SI-ID: 24823591