Marine engineering structures are simultaneously exposed to chloride-rich corrosive atmospheres and mechanical wear. Although multi-principal element alloy (MPEA) coatings are attractive protective candidates, combining high wear resistance with long-term corrosion stability remains challenging. Here, three non-equiatomic FeNiCoCr MPEA coatings with distinct distributions of Cr-rich precipitates are comparatively investigated by dry sliding tests and 60-day acetic acid salt spray exposure. The Fe5Ni2Co2Cr coating, containing discrete nanoscale Cr-rich precipitates, exhibits the lowest wear rate (approximately 2.0 × 10−5 mm3 N−1 m−1) and only isolated shallow pits after 60 days, with its surface evolving towards a Cr-rich, Fe-lean near-surface layer. In contrast, an interconnected precipitate network provides brittle intergranular paths for wear-induced delamination and Cr-lean anodic paths for localized corrosion. Controlling precipitate continuity and Cr distribution is therefore an effective microstructural design strategy for durable MPEA coatings in marine environments.
Refractory high-entropy alloys offer high-temperature strength but degrade rapidly in oxidizing environments. This Review examines halide-activated pack cementation as a surface-design strategy for controlling oxidation-driven degradation. We connect coating growth, silicide and aluminide formation, protective-scale chemistry and failure modes, and propose design criteria for coating architectures that retain protective reservoirs while avoiding brittle reaction zones.
Abstract In the present work, mechanical embossing with microstamps is used to support biodegradation of PLA/PBAT blends. Films of PLA/PBAT are modified by a microembossing process, using metallic stamps with different surfaces. Subsequently, biodegradation is carried out by incubation with Bacillus subtilis DSM 10. The biodegradation efficiency is evaluated through comparative LSM, WLI, mass loss measurements, as well as ATR-FTIR, Raman microscopy, XRD, REM, DSC and EDX before and after the bioegradation process. Results show that the structuring process leads to a significant increase in the degradation rate of the investigated PLA/PBAT blend. The results can be explained by a relative enrichment of PBAT in the near-surface region after degradation, indicating that the PLA component is preferentially degraded through enzymatic cleavage and subsequent microbial metabolization. The findings further demonstrate that the structure-modified surface enables a deliberately tunable PLA/PBAT film interaction with water: the surface exhibits hydrophobic static wettability alongside a controllable pinning effect during use, while a marked improvement in biodegradation is achieved when brought in contact with microorganisms. Mechanical structuring thus represents a simple, chemical-free, and industrially scalable approach to controlling this dual behavior.
Driven by surging power densities in data centres, immersion cooling is critical for high-heat-flux dissipation. However, despite their widespread use in data centres, there remains a lack of research into the compatibility of surface-mount aluminium electrolytic capacitors with coolants. This study evaluates the reliability of conductive polymer capacitors in synthetic oil through accelerated ageing tests at 70 °C, 80 °C, and 100 °C. Results identify butyl rubber swelling as the primary failure mode, causing structural deformation that precludes circuit assembly, rather than electrical drift. This degradation is driven by coolant molecules infiltrating the rubber matrix, inducing chain extension and reduced thermal stability. Simultaneously, poly(3,4-ethylenedioxythiophene) (PEDOT) de-doping increases the equivalent series resistance. Based on the Arrhenius model, the swelling-induced failure yields an activation energy of 43.7 kJ/mol, predicting a time to structural failure of approximately 492 days at 50 °C. These findings elucidate the physicochemical interactions between components and coolants, providing a theoretical framework for reliability design in immersion-cooled systems.
Yttria-stabilized zirconia (YSZ) is the benchmark thermal barrier topcoat, but its sintering response to water vapor is unclear. YSZ pellets of three initial porosities and free-standing plasma-sprayed coatings were heat-treated at 1300 °C in dry air, steam, or dry nitrogen. Contrary to reported promotion in simple oxides, steam retarded microstructural evolution. After 100 h the most porous pellet showed a 31% smaller grain size in steam, with apparent rate constants lower by factors of 2.8–4.2. A dry-nitrogen control in the same furnace changed the grain size by only 5.5%, isolating water vapor. Coatings likewise retained higher porosity and, at intermediate exposures, lower thermal conductivity. DFT calculations showed preferential OH binding at a grain-boundary Y3+ site (−2.73 eV); a defect-equilibrium sensitivity analysis predicted 8–22% oxygen-vacancy depletion. These results support a mechanism in which OH-mediated grain-boundary stabilization through Y3+ anchoring and vacancy-related defect modification leads to the retardation of sintering.
