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This study aims to find out friction and wear characteristics of graphene and graphene coating deposited by the Chemical Vapor Deposition (CVD) process on Honda GX270 engine (nodular cast iron) piston rings experimentally investigated under boundary lubricated conditions.

This study consists of two stages: tribotest and engine tests. First test was conducted through a reciprocating tribotest machine and second test was conducted through an engine bench with a duration of 75h. Engine piston ring was coated with graphene by two different methods: transfer method and direct CVD method.

Graphene has been demonstrated to be a potential and promising candidate for wear- and scratch-resistant coating because it is the thinnest, lightest and strongest known nanomaterial. In this case, the ability of a mono-layer graphene film to withstand high pressure differences (6 atm) indicates its mechanical robustness. It can effectively prevent or reduce mechanical failure by strengthening and toughening the loaded surface as well as by transferring the stress throughout the structure. The positive tribological outcomes of the graphene reinforced material under various dynamic loads revealed the potential of graphene-based coatings in macro - and micro-tribology.

This study fulfils an identified need to study for automotive industry a coating which is wear and scratch resistant.

Zinc dialkyldithiophosphate (ZDDP) is the most common anti-wear and anti-oxidant additive. ZDDP is the primary origin of zinc, sulfur and phosphorus, which are well-known poisonous elements for commercial after-treatment systems. The aim of this study is to investigate the optimum oil drain interval of non-phosphorus and non-ash (NPNA) engine oil that was developed as a prospective alternative to commercial phosphorus-containing (PC) engine lubricants.

The results of a fleet test wear debris analysis were used to optimize the oil drain intervals from the perspective of cost.

Drain intervals of 32,000 and 28,000 km were computed as the optimum values for NPNA and PC engine oils, respectively. Extending the oil drain intervals up to the obtained mileage may go to a total saving of €43,045,084.2 for PC engine oil and €49,253,998.6 for NPNA engine oil with respect to the total sales figures of test vehicles in Turkey.

Maximizing the lubricant life has environmental benefits and is the easiest way to reduce the maintenance cost of a vehicle. The protection of after-treatment systems against lubricant-induced poisoning is a great challenge. The most important result of this investigation is the lower operation costs of catalyst-friendly lubricants in spite of their low anti-wear additive performance.

This paper aims to investigate the wear mechanisms, formations and effectiveness of tribofilms of new developed, antiwear additive which is called mercapthocarboxylate. The mercapthocarboxylate is a sulphur-based and non-phosphorus additive.

The effectiveness of the additive was examined through a set of laboratory endurance tests that applied with single cylinder spark ignition engine. Two types of lubricants were used to compare the engine tests which were thiophosphate (ZDDP) containing engine lubricant (phosphorus containing) and mercapthocarboxylate containing non-phosphorus and non-ash crankcase oil. Lubricants were tested under identical operating conditions for 100 hrs. The surfaces of cylinder liner and piston rings were inspected through optical microscopy, scanning electron microscopy and energy dispersive X-ray spectroscopy techniques.

Catalysis-friendly and sulphur-based mercapthocarboxylate additive can be an alternative antiwear additive package for lubrication oil due to better wear performance when compared to ZDDP.

Sulphur-based mercapthocarboxylate is a new developed antiwear additive and was applied to lubrication oil in this study. This lubrication oil was tested in the real engine environment by using 100-hr engine bench tests.

This longitudinal study assesses whether higher education has the same impact on the entrepreneurial intentions of women and men with regard to their propensity to risk-taking in particular.

A self-administrated survey instrument was used to collect data from students studying business and engineering at five selected universities in Turkey. The survey was carried out in two intervals: first year and fourth year of studies. A total of 215 student participated in both waves.

The findings indicate that the impact of education is stronger for women than for men as the relationship between gender and entrepreneurial intention is moderated by education and risk-taking propensity in that the entrepreneurial intention of women with high or low risk-taking propensity increases when they acquire higher education. In particular, the boost is more noticeable for women with low risk-taking propensity. On the contrary, the effect of education is negative for men with both high risk-taking propensity and low risk-taking propensity.

This study has identified that the impact of education is different for women and men. Based on these findings, Turkey could offer gender-specific entrepreneurship education in higher education for individuals who could then exploit their entrepreneurial capacity and thus contribute to the social and economic well-being of the country.

This paper makes two distinct contributions. First, this is one of the few longitudinal studies in the literature which demonstrates the differences between females and males in terms of their entrepreneurial intention and shows how risk-taking and education influence entrepreneurial intention. Second, it offers new insights into entrepreneurship research from a developing-country but emerging-economy context.