This study presents a method for high temperature stabilization of amorphous alumina. The strain-induced stabilization is obtained by dispersion of rigid globular polycarbosilane macromolecules within an alumina matrix. The alumina matrix remains amorphous even at 1200 °C. This study confi rms the chemical composition of the coating with an advanced chemical depthprofi le analysis and shows its nanostructure by transmission electron microscopy. Based on this amorphous nanocomposite, a new facile and inexpensive coating for mechanical protection of glass surfaces is further developed. The nanocomposite coating is characterized by a full optical transparency and exceptional tribological characteristics. The wear resistance exceeds that of the current advanced ion-exchanged boroaluminosilicate glass by a factor of 25–35 whereas its scratch resistance is exceeded by more than an order of magnitude.
COBISS.SI-ID: 4427003
Information about the interactions between lubricants and DLC coatings is scarce, despite there having been many studies over the years. In this investigation we used ToF-SIMS, XPS and contact-angle analyses to examine the adsorption ability and mechanisms with respect to two oiliness additives, i.e., hexadecanol and hexadecanoic acid, on an a-C:H coating. In addition, we analyzed the resistance of the adsorbed films to external influences like solvent cleaning. The results show that both molecules adsorb onto surface oxides and hydroxides present on the initial DLC surface and shield these structures with their hydrocarbon tails. This makes the surfaces less polar, which is manifested in a smaller polar component of the surface energy. We also showed that ultrasonic cleaning in heptane has no significant effect on the quantity of adsorbed molecules or on their chemical state. This not only shows the relatively strong adsorption of these molecules, but also provides useful information for future experimental work. Of the two examined molecules, the acid showed a greater adsorption ability than the alcohol, which explains some of the previously reported better tribological properties in the case of the acid with respect to the alcohol.
COBISS.SI-ID: 14399003
This work focuses on the ZDDP concentration (1, 5 and 20 wt%) to form a ZDDP film on surfaces during static thermal tests at 150 °C. Silicon-doped and hydrogenated DLC coatings, as well as steel as reference, were studied using Attenuated Total Reflection-Fourier Transform Infrared (ATR-FTIR) spectroscopy and X-ray Photoelectron Spectroscopy (XPS). The results show that, on the three surfaces, the structure of the ZDDP thermal film consists of identical groups of pyrophosphate and zinc oxide, while the sulphuric groups are dissimilar. On the steel surface, the sulphuric part consists of a mixture of organic sulphide and sulphohydryl groups, but on H-DLC and Si-DLC only organic sulphide groups are found; there are no sulphohydryl groups. Moreover, both ATR-FTIR and XPS show that different concentrations of ZDDP do not affect the final chemical structure of the ZDDP thermal film on any of the studied surfaces. In addition, the XPS results show that the thickness of the thermal film is linear with the concentration for the whole range from 1 to 20 wt%, supporting also its uniform chemical structure. These thicknesses further show that the reactivity of the ZDDP film is higher on the steel surface than on the DLC coatings.
COBISS.SI-ID: 14627099
This paper presents a well-defined methodology for empirical modeling in tribology that was verified using the results from several tribometers. We propose a sequence of required statistical methods used to develop an empirical model and we discuss in detail why they are appropriate for use in tribology, in comparison with other possible solutions. A step-by-step guide for the generation of an empirical friction model, as a case study, is illustrated for steel-steel and steel-DLC contacts in the boundary lubrication regime lubricated with a commercial, fully formulated oil (5W30, EACEA A5/B5).
COBISS.SI-ID: 14591003
The evolution of the mechanical behaviour of zinc dialkyldithiophosphate (ZDDP) tribofilms on diamond-like carbon coatings during sliding contact has been studied by combining nano-indentation experimental data and finite element modelling. The nano-indentation data from the ZDDP tribofilms were obtained for two different sliding distances of the tribological tests after 15,000 and 216,000 cycles, which correspond to 25 min and 6 h, respectively. A non-homogeneous structure was found for the ZDDP tribofilms after both sliding distances, which were also verified by the local stiffness using the AFM force modulation mode. A dual structure is observed for the ZDDP tribofilms after 15,000 cycles, while three distinct components with different mechanical behaviours were found after 216,000 cycles. It was also found that the mechanical behaviour of the harder component of the ZDDP tribofilms remains almost unchanged for both sliding times, while the softer component tends to stiffen slightly over the sliding time. In addition, using the proposed algorithm with finite element simulations, the mechanical properties of the different components have been obtained, e.g. the elastic modulus E = 25.5 GPa and the yield stress Y = 1.585 GPa of the harder component for both sliding times. The softer component exhibits E = 1.65 GPa and Y = 0.144 GPa after 15,000 cycles and E = 3.5 GPa and Y = 0.17 GPa after 216,000 cycles. Finally, an intermediate component with E = 11.7 GPa and Y = 0.94 GPa has been only found at 216,000 cycles.
COBISS.SI-ID: 14585883