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The wear resistance and tribological characteristics of alumina/graphene layered and fiber-reinforced composites were investigated under dry sliding conditions at applied loads of 10 N and 50 N in the air. The experimental materials were prepared by a combination of electrospinning-calcination-chemical vapor deposition and spark plasma sintering. Graphene-coated Al2O3 microfibers were used to form layers in layered monolithic alumina/graphene-coated Al2O3 microfibers composite, and as reinforcements for the alumina matrix in the fiber-reinforced composite. The microstructure, deformation, and damage characteristics were studied. Both composites show a lower coefficient of friction in comparison to alumina with the lowest value of 0.42 for the fiber-reinforced composite measured at a load of 10 N. At the load of 10 N the composites exhibit very high wear resistance with values of wear rate 2.78 × 10−8mm3/(N·m) for the layered and 1.74 × 10−8mm3/(N·m) for the fiber-reinforced composite, in comparison to the wear rate of Al2O3 with a value of 5.35 × 10−6mm3/(N·m). The significant improvement in the wear resistance of the composites was associated with the improved mechanical properties and formation of a protective tribofilm on the wear tracks by the multilayered graphene present on the surface of Al2O3 microfibers and alumina debris, which provided the lubricating effect for the composites.

Electrospinning is a versatile and flexible technique for the preparation of ultrafine fibers. The present study aims to provide a comprehensive overview of electrospinning, as a complex technique, its evolution toward the high-throughput techniques, including the basic principles, parameters influencing the fibers production process, methods applied to solve the alignment difficulties, commonly used polymers and solvents, and the applications of the electrospun materials. We begin with an insight into the history of electrospinning, followed by its theoretical background and typical apparatus. Then, its renaissance over the past two decades as a powerful technology for the production of nanofibers suitable for industrial scale is presented. Afterward, we briefly discuss the applications of electrospun fibers, including use in different fields of industry, energy harvesting/conversion/storage, photonic and electronic devices, as well as biomedical applications. In the end, we also offer perspectives on the challenges and new directions for developments in electrospinning.

Deep eutectic solvents (DES) are formed by an acceptor and a donor of hydrogen bonds. They are generally considered as a possible alternative to hazardous organic solvents in various fields. Very recently they have also appeared in analytical chemistry, used mainly for the separation of analytes before instrumental quantification. For the development of new extraction procedures, it is important, among other things, to understand the mechanism of the extraction process itself. In this study we present NMR, IR and Raman spectroscopy studies of TBAB-Gly-based DESs at various HBA:HBD molar ratios for the neat DES as well as the DES mixed with various amounts of added water to better understand the mechanism of DES formation, intermolecular interactions in DES and the interaction of the DES with water, which have not yet been studied in detail. The obtained results indicate that hydrogen bonds between TBAB and Gly exist in the DESs at all molar ratios (1:2; 1:3; 1:4). A small amount of water added to the DES structure provides the establishment of an H-bond network, which does not weaken the existing H-bonds between the HBA and HBD, thus creating a stable supramolecular structure. However, further increasing of water amount provide to weakened of hydrogen bonds between TBAB and Gly.