Influence of structural depth of laser-patterned steel surfaces on the solid lubricity of carbon nanoparticle coatings

Carbon nanoparticle coatings on laser-patterned stainless-steel surfaces present a solid lubrication system where the pattern’s recessions act as lubricant-retaining reservoirs. This study investigates the influence of the structural depth of line patterns coated with multi-walled carbon nanotubes (CNTs) and carbon onions (COs) on their respective potential to reduce friction and wear. Direct laser interference patterning (DLIP) with a pulse duration of 12 ps is used to create line patterns with three different structural depths at a periodicity of 3.5 µm on AISI 304 steel platelets. Subsequently, electrophoretic deposition (EPD) is applied to form homogeneous carbon nanoparticle coatings on the patterned platelets. Tribological ball-on-disc experiments are conducted on the as-described surfaces with an alumina counter body at a load of 100 mN. The results show that the shallower the coated structure, the lower its coefficient of friction (COF), regardless of the particle type. Thereby, with a minimum of just below 0.20, CNTs reach lower COF values than COs over most of the testing period. The resulting wear tracks are characterized by scanning electron microscopy, transmission electron microscopy, and energy-dispersive X-ray spectroscopy. During friction testing, the CNTs remain in contact, and the immediate proximity, whereas the CO coating is largely removed. Regardless of structural depth, no oxidation occurs on CNT-coated surfaces, whereas minor oxidation is detected on CO-coated wear tracks. [Figure not available: see fulltext.]

The Cold Angular Rolling Process of Copper Sheets: Unraveling Plastic Deformation Behavior and Unveiling Microstructural Transformations

The cold angular rolling process (CARP) is being developed as a continuous severe plastic deformation technique, which can process metal sheets without any length limitations at room temperature. CARP contains cold rolling and equal-channel angular process components. The sheet thickness is kept consistent before and after CARP, allowing multiple passes of the sheet. The desired microstructure and mechanical properties can be achieved in the processed metallic sheets. The current study is aimed to evaluate the capability of CARP by processing copper sheets with different sheet widths for repetitive passes. The CARP-treated sheets are examined by lab-scale X-ray and high-energy synchrotron X-ray diffraction to investigate the evolution in dislocation density, texture, and strain anisotropy, and by tensile testing to identify the bulk mechanical properties. The digital image correlation method is applied to tensile testing so that strain localization within the sample gauge is visualized and deformation behavior is evaluated after yielding till postnecking by estimating the hardening exponent and strain hardening rate of the CARP-treated sheet. Comparing the reported continuous and multiple-step processes on Cu and its alloys, the present study confirms that the CARP is potentially a useful sheet process for strengthening ductile metals

Na⁺/K⁺-pump and neurotransmitter membrane receptors

Na+/K+-pump is an electrogenic transmembrane ATPase located in the outer plasma membrane of cells. The Na+/K+-ATPase pumps 3 sodium ions out of cells while pumping 2 potassium ions into cells. Both cations move against their concentration gradients. This enzyme’s electrogenic nature means that it has a chronic role in stabilizing the resting membrane potential of the cell, in regulating the cell volume and in the signal transduction of the cell. This review will mainly consider the role of the Na+/K+-pump in neurons, with an emphasis on its role in modulating neurotransmitter receptor. Most of the literature on the modulation of neurotransmitter receptors refers to the situation in the mammalian nervous system, but the position is likely to be similar in most, if not all, invertebrate nervous systems.</p