Deniz Harp Okulu

The maritime transportation sector globally depends on fossil resources while this option is both diminishing and causing serious environmental and air pollution issues.Recently, hydrogen energy becomes one of the key alternatives addressing these concerns under the increasing press effect of the international community.The use of hydrogen as an energy source in ships is provided by fuel cell technologies.Although there are many types of fuel cells, Proton Exchange Membrane Fuel Cell (PEMFC) is the most widely used fuel cell type in the maritime industry.The most important handicap for the use of hydrogen in ships seems to be the production and storage of it.For this reason, fuel cell technol. and hydrogen production and storage systems must be developed to use hydrogen as the main propulsion system in long-distance transportation in the maritime sector.In this study, Reference Energy System (RES) is established for a chem. tanker ship to determine the current energy flow from various resources to demands.Then the appropriate parameters are assigned and this framework is specified by the resp. data.Following this phase; the current situation was developed as the base scenario and analyzed by using the Low Emission Anal. Program (LEAP) energy modeling platform.Addnl., two alternative scenarios including the hydrogen-based were applied against the base scenario to compare the environmental results in the 2017-2050 time period.When the results are evaluated, although it is not sufficient for IMO and EMSA targets, implementation of hydrogen contributes to the carbon emission reduction pos. and it will be more beneficial to apply to the main drive system with the technol. developments to be made in the near future.

In this study, the wear and friction behavior of cathodic arc phys. vapor deposited AlTiSiN+TiSiN coatings on H13 tool steels were investigated by using CrN, TiN and AlCrN interlayers with tribometer tests both under unlubricated and boundary lubricated conditions. 6 mm alumina balls were used as counter surfaces to test ceramic hard coatings.Surface coatings were characterized through nanoindentation, SEM coupled with an energy-dispersive X-ray spectrometer (SEM/EDXS), optical profilometry, and at. force microscopy (AFM) techniques.The results showed that especially AlTiSiN+TiSiN coating with TiN interlayer resulted in a much more enhanced tribol. performance of the tool steels at both unlubricated and the boundary lubricated conditions even at elevated contact pressures.

Corrosion and wear protection of metals are crucial for all industrial applications.Graphene oxide (GO) is a chem. modified form of graphene and is highly promising for corrosion inhibition.Although corrosion protection of metal surfaces by the use of graphene oxide has been well investigated, anti-wear reduction of graphene oxide has not been studied especially under lubricated condition.In this work, Cr coated steel ring was coated with GO by atm. pressure chem. vapor deposition that hasn't been reported in the literature yet.The corrosion resistance of the coatings was evaluated by potentiodynamic polarization, immersion tests and the wear behavior of the coatings was investigated under lubricated conditions.Here we show that GO coated piston rings showed excellent corrosion resistance at extreme corrosive media.Our results also show that GO reacts with ZDDP and forms tribofilm that provides addnl. wear resistance to the ring, which resulted in very effective wear protection because of no wear scar observation on the ring surface.