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    Öğe
    Contribution of galvanic coupling with TiN, TiAlN, and CrN to the corrosion of steel in neutral and acidic chloride solutions
    (Wiley-V C H Verlag Gmbh, 2023) Avci, Burcak; Kazmanli, Kursat; Evren, Burak; Urgen, Mustafa
    The inherent defective morphology of the physical vapor deposition (PVD) hard coatings limits their corrosion protective ability. We examined the impact of nitride-based PVD coatings, including TiN, TiAlN, and CrN deposited on inert substrates by cathodic arc PVD method (CA-PVD), on the galvanic corrosion of carbon steel. Their contribution was evaluated by zero-resistance ammeter (ZRA) and electrochemical impedance spectroscopy (EIS) in 3.5 wt.% NaCl at pH 2 and 6, with and without aeration. The results indicated the prominent role of the coating type and the coupling environment on the generated galvanic currents. Immersion tests for the TiN-, TiAlN-, and CrN-coated steel cross-sections visually verified these results. The galvanic current contribution was distinct in environments where oxygen reduction is the dominant cathodic reaction. However, the layers' contribution to galvanic corrosion was minimal in deaerated acidic solutions, which is attributed to the high bonding strength of adsorbed intermediates to the coating surfaces.
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    Öğe
    Enhanced interface structure of electroformed copper/diamond composites for thermal management applications
    (Walter De Gruyter Gmbh, 2024) Evren, Burak; Evren, Gokce; Kincal, Cem; Solak, Nuri; Urgen, Mustafa
    As the power density of electronic devices increases, the requirement for heat sinks with enhanced thermal properties becomes imperative for advanced heat dissipation. Copper/diamond composites are next-generation heat dissipators with high thermal conductivities, yet fabrication of these composites requires high energy and complex instruments. In this study, copper/diamond composites are fabricated by electroforming. The sediment co-deposition process is modified to obtain uniform diamond particle distribution with tailorable volume fraction. Diamond particles were initially settled on the cathode surface outside the electrolyte, and then the setup was immersed in an acidic copper sulfate electroforming bath. Varying amounts (0-100 mg l(-1)) of thiourea are introduced to the electrolyte to enhance the matrix-particle interface. The gaps between diamond particles are filled with electrodeposited copper using optimized deposition conditions. The composite structure detaches from the cathode by itself after the production with desired shape and dimensions. The effect of operating conditions on cathodic polarization, composite microstructure, and thermal properties are investigated. Thermal conductivity of 49 vol.% diamond containing sample fabricated with optimized parameters exceeds 667 W m(-1) K-1. The increase in thermal conductivity and enhanced interface structure is attributed to the excellent void-filling ability of the optimized electrolyte.