Surfaces, Volume 5, Issue 3 (September 2022) – 5 articles

Counter-surfaces for radial shaft seals are usually finished by infeed grinding to avoid macro twist structures on the surface since they can impose a conveying action on the lubricant. This can lead to either leakage or starved lubrication and subsequent thermal damage depending on the direction of said conveying action. Turning processes can offer a more cost-effective surface finish, but conventional methods cause twist structures, which can impair the leakage prevention of the sealing system. An approach for the production of twist-free surfaces was developed based on new kinematics for turning. However, the surfaces produced with this approach using case hardened specimens made from the steel 16MnCr5 show deviating structural characteristics compared to the kinematic simulation. The causes of this and the resulting influence on the conveying value are the subjects of the research work. For this purpose, in addition to hardened steel, two other materials are considered: the steel 16MnCr5 in the unhardened hot rolled delivery condition and brass as a material with good machinability. The results clearly show that there is a deviation in the machining behavior of the steel materials compared to the kinematic surface simulations, especially in the repeatedly turned areas. This is mainly due to elastic–plastic deformation effects. Despite the actually twist-free surface profile, certain characteristics result in an anisotropic structure, which partially has an influence on the conveying value. Full article

Microfouling is the deposition of inorganic and organic material on surfaces and can cause economic losses. This deposition affects the performance of vessels, causes corrosion, clogging of equipment and contaminates the surfaces of medical items and the surface of machinery that handles food; it is controlled by cleaning products that contain synthetic surfactants in their formulations. Biobased products provide a promising basis to produce sustainable chemicals such as surfactants. In the present study, the biobased surfactants glyceryl laurate and hydroxystearic acid were synthesized and evaluated for stability at different pH values, salinity and temperatures. In addition, bioactivity tests against Pseudomonas aeruginosa (UCP 0992) and Bacillus cereus (UCP 1516) were also performed. Biobased surfactants glyceryl laurate and hydroxystearic acid showed excellent stability against temperature, pH, salinity and emulsifying activities for different kinds of oils; prevented bacterial adhesion by almost 100%; and affected the production of EPS by both bacteria and their consortium when compared to a synthetic surfactant SDS. The results showed the potential of these substances for application as an alternative antifouling non-biocide. Full article

Poly(2-methoxyethyl acrylate) (PMEA) is a US FDA-approved biocompatible polymer, although there is insufficient work on human umbilical vein endothelial cells (HUVECs) and platelet interaction analysis on PMEA-analogous polymers. In this study, we extensively investigated HUVEC–polymer and platelet–polymer interaction behavior by measuring the adhesion strength using single-cell force spectroscopy. Furthermore, the hydration layer of the polymer interface was observed using frequency-modulation atomic force microscopy. We found that endothelial cells can attach and spread on the PMEA surface with strong adhesion strength compared to other analogous polymers. We found that the hydration layers on the PMEA-analogous polymers were closely related to their weak platelet adhesion behavior. Based on our results, it can be concluded that PMEA is a promising candidate for the construction of artificial small-diameter blood vessels owing to the presence of IW and a hydration layer on the interface. Full article

Owing to the light weight and high energy, the “All-aluminum engine” can reduce fuel consumption and pollutant emissions, showing a great significance in saving resources and protecting the environment, and becoming a research hotspot. However, the aluminum alloy cylinder liners have difficulty withstanding extremely harsh working conditions, such as strong friction and wear, making the engine extremely easy to damage. In this work, Al-25Si wear-resistant coating was deposited by inner hole supersonic plasma spraying technique to improve the wear resistance of the aluminum alloy cylinder liner. The microstructure, phase composition, mechanical properties and tribological properties were tested by SEM, XRD, tribological machine, etc. The results indicated that the coating exhibited an excellent bonding strength of 44.1 MPa, and the average hardness and average friction coefficient of the coating are 267.09 ± 14.85 HV_0.2, and 0.20, respectively. The total wear amount, the wear scar width and the wear scar depth of the coating are 2.77 × 10⁻³ mm³, 654.3 μm and 8.95 μm, respectively, which showed that the coating can significantly improve the tribological properties of the “All-aluminum engine”. The wear mechanism of the coating was mainly interpreted by furrow cutting, extrusion and spalling in two-body abrasive wear, three-body abrasive wear and a small amount of oxidative wear. Full article

Supercapacitors have played an important role in electrochemical energy storage. Recently, researchers have found many effective methods to improve electrode materials with more robust performances through the increasing volume of scientific publications in this field. Though nickel cobaltite (NiCo₂O₄), as a promising electrode material, has substantially demonstrated potential properties for supercapacitors, its composites usually show much better performances than the pristine NiCo₂O₄. The combination of carbon-based materials and NiCo₂O₄ has been implemented recently due to the dual mechanisms for energy storage and the unique advantages of carbon materials. In this paper, we review the recent research on the hybrids of NiCo₂O₄ and carbon nanomaterials for supercapacitors. Typically, we focused on the reports related to the composites containing graphene (or reduced graphene oxide), carbon nanotubes, and amorphous carbon, as well as the major synthesis routes and electrochemical performances. Finally, the prospect for the future work is also discussed. Full article