Owing to MXenes’ tunable mechanical properties induced by their structural and chemical diversity, MXenes are believed to compete with state-of-the-art 2D nanomaterials such as graphene regarding their tribological performance. Their nanolaminate structure offers weak interlayer interactions and an easy-to-shear ability to render them excellent candidates for solid lubrication. However, the acting friction and wear mechanisms are yet to be explored. To elucidate these mechanisms, 100-nm-thick homogeneous multilayer Ti3C2T x coatings are deposited on technologically relevant stainless steel by electrospraying. Using ball-on-disk tribometry (Si3N4 counterbody) with acting contact pressures of about 300 MPa, their long-term friction and wear performance under dry conditions are studied. MXene-coated specimens demonstrate a 6-fold friction reduction and an ultralow wear rate (4 × 10–9 mm3 N–1 m–1) over 100 000 sliding cycles, outperforming state-of-the-art 2D nanomaterials by at least 200% regarding their wear life. High-resolution characterization verified the formation of a beneficial tribolayer consisting of thermally/mechanically degraded MXenes and amorphous/nanocrystalline iron oxides. The transfer of this tribolayer to the counterbody transforms the initial steel/Si3N4 contact to tribolayer/tribolayer contact with low shear resistance. MXene pileups at the wear track’s reversal points continuously supply the tribological contact with fresh, lubricious nanosheets, thus enabling an ultra-wear-resistant and low-friction performance.

Low aspect ratios and sp3 hybridization of carbon nanoparticles benefit both, small agglomerate sizes in ethylene glycol and nickel composites.

The use of lubricants (solid or liquid) is a well-known and suitable approach to reduce friction and wear of moving machine components. Another possibility to influence the tribological behaviour is the formation of well-defined surface topographies such as dimples, bumps or lattice-like pattern geometries by laser surface texturing. However, both methods are limited in their effect: surface textures may be gradually destroyed by plastic deformation and lubricants may be removed from the contact area, therefore no longer properly protecting the contacting surfaces. The present study focuses on the combination of both methods as an integral solution, overcoming individual limitations of each method. Multiwall carbon nanotubes (MWCNT), a known solid lubricant, are deposited onto laser surface textured samples by electrophoretic deposition. The frictional behaviour is recorded by a tribometer and resulting wear tracks are analysed by scanning electron microscopy and Raman spectroscopy in order to reveal the acting tribological mechanisms. The combined approach shows an extended, minimum fivefold longevity of the lubrication and a significantly reduced degradation of the laser textures. Raman spectroscopy proves decelerated MWCNT degradation and oxide formation in the contact. Finally, a lubricant entrapping model based on surface texturing is proposed and demonstrated.

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Lactose-derived non-digestible oligosaccharides are prominent components of functional foods. Among them, galacto-oligosaccharides (GOS) outstand for being prebiotics whose health-promoting effects are supported on strong scientific evidences, having unique properties as substitutes of human milk oligosaccharides in formulas for newborns and infants. GOS are currently produced enzymatically in a kinetically-controlled reaction of lactose transgalactosylation catalyzed by β-galactosidases from different microbial strains. The enzymatic synthesis of GOS, although being an established technology, still offers many technological challenges and opportunities for further development that has to be considered within the framework of functional foods which is the most rapidly expanding market within the food sector. This paper presents the current technological status of GOS production, its main achievements and challenges. Most of the problems yet to be solved refer to the rather low GOS yields attainable that rarely exceed 40 %, corresponding to lactose conversions around 60 %. This means that the product or reaction (raw GOS) contains significant amounts of residual lactose and monosaccharides (glucose and galactose). Efforts to increase such yields have been for the most part unsuccessful, even though improvements by genetic and protein engineering strategies are to be expected in the near future. Low yields impose a burden on downstream processing to obtain a GOS product of the required purity. Different strategies for raw GOS purification are reviewed and their technological significance is appraised.

Surface structures in the micro-and nanometre length scale exert a major influence on performance and functionality for many specialized applications in surface engineering. However, they are often limited to certain pattern scales and materials, depending on which processing technique is used. Likewise, the morphology of the topography is in complex relation to the utilized processing methodology. in this study, the generation of hierarchical surface structures in the micro-as well as the sub-micrometre scale was achieved on ceramic, polymer and metallic materials by utilizing Ultrashort pulsed Direct Laser interference patterning (USp-DLip). the morphologies of the generated patterns where examined in relation to the unique physical interaction of each material with ultrashort pulsed laser irradiation. In this context, the pattern formation on copper, CuZn37 brass and AISI 304 stainless steel was investigated in detail by means of a combination of experiment and simulation to understand the individual thermal interactions involved in USp-DLip processing. thereby, the pattern's hierarchical topography could be tailored besides achieving higher process control in the production of patterns in the sub-µm range by USp-DLip. Highly specific surface properties in nature, like the well-known lotus and shark skin effects, are closely related to surface structures in the micrometre and nanometre length scale, often involving hierarchical patterns 1. In fact, such biomimetic surface patterns have already proven to provide unique properties in several technical systems including the manipulation of contact mechanics and optical properties like light diffraction and absorption 2-4. Patterns on the threshold between the micro-and the nanometre scale also showed to provide promising surface properties for medical products, as they can tailor the adhesion of both, cells and germs 5-7. In this context, current research projects investigate the intricacies to prevent biofilm formation by surface patterning of different solid materials on the International Space Station (ISS), which endanger its crew in terms of both, health and damage to critical components 8. The predominant impact on the unique properties of patterned surfaces is defined by the scale and morphology of the surface features also including sub-patterns, which have to be adjusted specifically for each application. For instance, in antibacterial applications, feature sizes in the sub-µm length scale showed to be most effective against bacterial adhesion 7-10. The processing methodology, dealing with such delicate surface modification, needs to ensure high machining precision as well as processing speeds and costs, which are able to compete with the classical methods of surface engineering. Besides lithographic methods, laser interference-based techniques have proven their worth in generating precise surface patterns, as they provide high processing speeds with little to no need for preparation and post-processing 11. Direct Laser Interference Patterning (DLIP) usi...

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