Tribological properties of Cr/a-C coatings in aqueous solutions

The Cr/a-C coatings were deposited using unbalanced magnetron sputtering. The influence of Cr content and salinity on the water-lubricated tribological properties of Cr/a-C coatings was investigated. The low Cr containing Cr/a-C coatings (?4.9at.%) exhibited low friction and wear, but the high Cr content would worsen their tribological properties in water. The lowest friction coefficient was obtained at 32.27‰, but the lowest wear rates of tribomaterials were acquired at 29.84‰

The influence of Ni concentration on the structure, mechanical and tribological properties of Ni-CrSiN coatings in seawater

The impact of Ni content on the microstructure, hardness, fracture toughness and tribological properties of Ni-CrSiN coatings in seawater was investigated by using X-ray diffraction, dynamic ultra micro hardness tester and ball-on-disk tribometer. The structural analyses indicated that the Ni existed in the form of amorphous phase regardless of concentrations. The hardness of Ni-CrSiN coating maintained around 28.1 GPa at low Ni incorporation but decreased to 20.1 GPa at 10.8 at% Ni concentration. Then, owing to grain refinement, the hardness increased to 24.5 GPa at 13.9 at% Ni concentration. All coatings presented compressive stress that led to the formation of circular cracks around indentation impression. The Ni incorporation especially at high concentration was able to improve coatings toughness against circular cracks. Although the Ni incorporation had no effect in reducing the friction coefficient of CrSiN coatings in seawater, but the moderate Ni incorporation (5.2 at%) could enhance the wear resistance of CrSiN coatings in seawater due to the favorable combination of hardness and toughness. (C) 2019 Elsevier B.V. All rights reserved

Progress in Preparation and Modification of LiNi0.6Mn0.2Co0.2O2 Cathode Material for High Energy Density Li-Ion Batteries

Due to the advantages of high specific capacity, various temperatures, and low cost, layered LiNi0.6Co0.2Mn0.2O2 has become one of the potential cathode materials for lithium-ion battery. However, its application was limited by the high cation mixing degree and poor electric conductivity. In this paper, the influences of synthesis methods and modification such surface coating and doping materials on the electrochemical properties such as capacity, cycle stability, rate capability, and impedance of LiNi0.6Co0.2Mn0.2O2 cathode materials are reviewed and discussed. The confronting issues of LiNi0.6Co0.2Mn0.2O2 cathode materials have been pointed out, and the future development of its application is also prospected

Excitonic Evolution in WS₂/MoS₂ van der Waals Heterostructures Turned by Out-of-Plane Localized Pressure

In this study, we explore the exciton dynamics in a WS2/MoS2 van der Waals (vdW) heterostructure under varying pressures by integrating a laser-confocal photoluminescence (PL) spectroscope and an atomic force microscope (AFM). For the WS2/MoS2 heterostructure, the exciton emission belonging to MoS2 is too weak to be distinguished from the PL spectra. However, upon contact with a Si probe, the emission intensity of WS2 excitons significantly decreases from 34,234 to 6560, thereby matching the intensity level of MoS2. This alteration substantially facilitates the exploration of interlayer excitonic properties within the heterostructures using PL spectroscopy. Furthermore, the Si probe can apply out-of-plane localized pressure to the heterostructure. With increasing pressure, the emission intensity of the WS2 trions decreases at a rate twice that of other excitons, and the exciton energy increases at a rate of 0.1 meV nN−1. These results elucidate that the WS2 trions are particularly sensitive to the out-of-plane pressure within a WS2/MoS2 vdW heterostructure