RESUMO
The aim of this article is to experimentally determine the role of the environment, consisting of a base oil (PAO), carbon nanomaterials, and optional other additives, as well as the kind of metal in contact with the lubrication film, in the stimulation of zinc dialkyldithiophosphate (ZDDP) additives' effectiveness during protective film formation. This paper focuses on the role of carbon nanostructures in energy transportation and conversion during tribological processes. An antistatic additive (ASA) (not used in lubricating oils) for jet fuels was added to disturb the process of energy conduction (electric charges) through the lubricant film and thus determine how this disturbance affects the kinetics of the ZDDP triboreaction and, consequently, the linear wear. To achieve this research goal, two types of tribological testing devices were used: an Anton Paar tribometer (TRB) and a triboelectric tribometer (TET). The novelty of the present research is in the use of the method for disturbing the flow of charge/energy through the lubricant film with an antistatic additive for jet fuels, ASA, to influence the impact of this energy on the antiwear properties of ZDDP. The following conclusions were drawn: (1) carbon-based nanostructures, i.e., CNTs, AuCNTs, graphene, and fullerenes, are able to change the rate of chemical reactions of ZDDP during tribological processes; (2) CNTs have the ability to catalyze tribochemical reactions of ZDDP, while graphene and fullerenes are not able to perform this effectively; (3) AuCNT takes the role of an inhibitor during ZDDP's triboreaction; and (4) by discharging electric charge/energy, ASA, in cooperation with CNT and AuCNT significantly reduces the rate of the ZDDP reaction.
RESUMO
Clinical trials conducted in many centres worldwide indicate that, despite advances made in the use of biomaterials for medical applications, tribocorrosive wear remains a significant issue. The release of wear residue into body fluids can cause inflammation and, as a result, implant failure. Surface modification is one of the methods used to improve the mechanical, tribological, and fatigue properties of biomaterials. In this article, the authors investigated the impact of ion implantation on improving the functional properties of implant surfaces. This paper presents morphology, geometric surface structure, hardness, and tribological test results for layers obtained by ion implantation with nitrogen and oxygen ions on alloy 316L. The surface morphology and thickness of the implanted layer were examined using scanning microscopy. Atomic force microscopy was used to evaluate the geometric structure of the surface. Instrumented indentation was used to measure nanohardness. Model tribo tests were carried out for reciprocating motion under conditions of dry friction and lubricated friction with Ringer's solution. The tribological tests showed that the implanted samples had a lower wear than the reference samples. Nitrogen ion implantation increased the hardness of 316L steel by about 45% and increased it by about 15% when oxygen ions were used.
RESUMO
If a lubricant contains structures capable of conducting energy, reactions involving zinc dialkyldithiophosphate (ZDDP) may take place both very close to and away from the solid surfaces, with this indicating that ZDDP can be a highly effective anti-wear (AW) additive. The central thesis of this article is that the tribocatalytic effect is observed only when the energy emitted by the solids is transmitted by ordered molecular structures present in the lubricant, e.g., graphene. The friction tests were carried out for 100Cr6 steel balls in a sliding contact with uncoated or W-DLC-coated HS6-5-2C steel discs in the presence of polyalphaolefin 8 (PAO 8) as the lubricant, which was enhanced with graphene and/or ZDDP. There is sufficient evidence of the interactions occurring between ZDDP and graphene and their effects on the tribological performance of the system. It was also found that the higher the concentration of zinc in the wear area, the lower the wear. This was probably due to the energy transfer resulting from the catalytic decomposition of ZDDP molecules. Graphene, playing the role of the catalyst, contributed to that energy transfer.
RESUMO
The data from the authors' earlier investigations show that molecules of zinc dithiophosphate (ZDDP) added to a lubricant can absorb energy emitted by a solid surface, which is where triboreactions occur. If the lubricant contains structures able to conduct energy, the ZDDP reactions can occur even at a relatively large distance from the solid surface, which should increase the effectiveness of ZDDP as an antiwear additive. The purpose of this paper was to verify the thesis that the tribocatalytic effect depends on the ability of the solid surface to emit electrons/energy and the ability of ordered molecular structures, such as carbon nanotubes (CNTs), to conduct energy and, most likely, to enhance the energy transfer. The tribological tests were performed using a TRB3 tribotester for 100Cr6 steel balls and uncoated or a-C:H coated HS6-5-2C steel discs. Polyalphaolefin 8 (PAO8) and PAO8 mixed with ZDDP and CNTs were used as lubricants. The results of the tribological tests suggested that: (a) the effect of the interactions between ZDDP and CNTs was clearly visible; (b) the structure and properties of the solid surface layer had a significant influence on the antiwear action of the ZDDP additive.
