Papers by Keyword: Molybdenum Disulfide

Abstract: Steel 1.7220 is widely used in mechanical engineering for heavily loaded components operating at temperatures up to 450 °C. Femtosecond laser processing enables the formation of controlled microstructures without overheating or deformation, reducing the contact area and serving as reservoirs for lubricants. This study aims to evaluate the effect of laser microstructuring (Mesh and LIPSS types) on the tribological properties of steel, particularly under dry lubrication with powder. Micro- and nanostructures were analyzed using optical and scanning electron microscopy. Tribological tests were conducted using the ball-on-plate reciprocating method, with a load of 200 g, a frequency of 2 Hz, and a stroke amplitude of 1 cm for 30 minutes. For LIPSS structures, the influence of the friction direction relative to the orientation of the surface structures was investigated. The change in surface morphology after laser texturing was investigated. The effects of lubrication and surface structuring on tribological properties were analyzed, and the role of periodic structures in enhancing tribofilm stability was demonstrated.

Abstract: In this study, a novel reduced graphene oxide, indium (III) oxide, and molybdenum disulfide (rGO/In₂O₃/MoS₂) ternary composite for supercapacitor electrode application was developed via green hydrothermal synthesis. The topography, surface morphology, crystalline structure, phase identification and molecular structure of the composites were examined by applying Scanning Electron Microscopy (SEM), Energy Dispersive Spectroscopy (EDX), Transmission Electron Microscopy (TEM), X-ray Diffraction Spectroscopy (XRD), X-Ray Photoelectron Spectroscopy (XPS), and Raman Spectroscopy. SEM and TEM reveal the uniform dispersion of In₂O₃ nanoparticles on the rGO and MoS₂ sheets. EDX, XRD, and XPS analysis confirm the coexistences of rGO, In₂O₃, and MoS₂, and hence the composite formation. The electrochemical performances of rGO/In₂O₃/MoS₂ ternary composite were evaluated by cyclic voltammetry (CV) in two-electrode configuration in 1 M sodium sulfite (Na₂SO₃) aqueous electrolyte. The electrochemical results show that the rGO/In₂O₃/MoS₂ composite electrodes possess improved specific capacitance of 77 F/g at a scan rate of 25 mV/s, a modest 29% enhancement over pure In₂O₃ and In₂O₃/MoS₂ binary composite.

Abstract: Recently, molybdenum disulfide (MoS₂), have been explored as photothermal materials for solar evaporation. However, the optimum phase for photothermal material, 1T-MoS₂ or 2H-MoS_2, is still debatable. In this work, we observed the morphological and structural properties of MoS₂ prepared by a simple hydrothermal process at 200 °C in three different growth times (16, 20, and 24 hours) using Na₂MoO₄·2H₂O (sodium molybdate) as a Mo precursor, and CS(NH₂)₂ (thiourea) as S precursor. MoS₂ nanoflowers were successfully prepared with nanosheets petals and its diameter increased from 0.4 to 2.8 and 4.5 as the growth time increased from 16 to 20 and 24 hours. The increase in growth time also led to improve the Mo:S ratio from 1:8 to 1:5 and facilitate the phase transformation from 1T to 2H as indicated by the shifting of (002) diffraction peak from 9.25° to higher degrees (12.98°, and 14.12°).

Abstract: Molybdenum disulfide (MoS₂) is one of the promising 2D materials thanks to its outstanding physicochemical properties and therefore is predicted to play a key role in optoelectronics devices and energy applications. MoS₂ exhibits three phases with distinctive crystal structure depending on its stacking order: 1T (metallic), 2H (semiconducting), and 3R (semiconducting). Among all of them, 1T-MoS₂ has become the center of interest due to its e.g., high catalytic activity. However, most of the methods to obtain 1T-MoS₂ are complex and costly, for example strain engineering, electron beam treatment, and plasmonic hot electron injection. As response, we here demonstrate a facile and cost-efficient hydrothermal route at 200 °C to synthesize MoS₂ with high content of 1T phase. MoS₂-200 °C nanoflowers has an average diameter of 2.96 µm with the S/Mo atomic ratio of 1.50 and the band gap of 1.39 eV. It has an additional diffraction peak at 2θ = 9.22^o_, indicating the transformation of semiconducting 2H into metallic 1T. Higher concentration of 1T phase in MoS₂-200 °C is also indicated by high intensity of the E_1g Raman peak.

Abstract: The purpose of the investigations carried out is the formation of qualitative nanostructured coatings and development of methods for their application on product surfaces. The principle of a staged study of regularities in the formation of vibration mechanical-chemical coatings from “top to bottom” and “bottom-up” formed a basis of a methodological approach to investigation carrying out. Experimental researches were carried out with the use of specially developed working chambers installed upon vibration machines. As an indenter there were used metal balls 2-5 mm in diameter and made of steel of ShH15 type, samples material – steel 45. The assessment of coating characteristics was carried out with the use of optical, raster scanning probe microscopy. It is determined through the result in the investigations of the impact-pulse interaction of a working environment part under conditions of vibration impact that there are grindings and changes in particles dimensions up to 100 nm and lesser in coating material which allows them to penetrate into micro-and nanocavities of basic metal and, in such a way, to form coating with high antifriction properties. The influence of amplitude-frequency properties of vibro-wave activation upon quality and performance attributes of coating surfaces and also process duration is determined.

Abstract: For estimating effectiveness of adding solid fillers for composites with ultra-high molecular weight polyethylene matrix tribotechnical characteristics of UHMWPE mixture with graphite, molybdenum disulfide and polytetrafluoroethylene were investigated under dry friction, boundary lubrication and abrasion. The optimum filler weight fraction was determined in terms of increasing wear resistance. Permolecular structure and surface topography of wear tracks for UHMWPE composites with different weight fraction of the fillers was studied. The mechanisms of wear of polymeric composites “UHMWPE-graphite”, “UHMWPE-PTFE” and “UHMWPE-MoS₂” under dry sliding friction and abrasive wear are discussed.

Abstract: Efficient two-step technique of tungsten and molybdenum disulfides obtaining from metal nanopowders produced by EEW and elementary sulphur is described. Tungsten and molybdenum nanopowders surface area dependence on wire length is studied. Features of metal and sulphur combustion process are discussed. It is determined sulphur excess in reagents 15 wt.% results in mono-phase metal disulfide formation with small free sulphur concentration in reaction products.

Abstract: An attempt has been made to develop and characterize the Al2219 reinforced with Boron carbide (B₄C) and Molybdenum disulfide (MoS₂) hybridcomposites. The hybrid composites were prepared by using stir casting technique. Theexperimentalresult evaluates the density,micro hardness test & tensiletest.Themicrostructure shows existence of randomly dispersed reinforcement particles andfine reinforcement particles in prepared hybrid composites.X-Ray powder diffraction (XRD) analysis were conducted this confirms the physical content of constituents present in prepared composites. SEM is used to examine fracture surface of tensile specimens for hybrid composites & this consists of ductile& brittle fracture of mixed mode.The test results revels that, themicro hardness and density is minimum for Al2219 and maximum for Al+3%B₄C+5%MoS_2. The tensile properties of the material vary according to the percentage of reinforcing material added.

Abstract: Multipurpose tungsten and molybdenum disulfides with nanoscale layered structure formation are studied. Morphology and particle size distribution of initial tungsten and molybdenum nanopowders produced by electrical explosion of wire and used in metal disulfides synthesis are presented. Mechanism of metal nanopowder and elementary sulphur interaction in SHS condition with WS₂/MoS₂ nanoscale layered particles formation is considered.

Abstract: X-ray and transmission electron microscopy results of initial tungsten and molybdenum nanopowders produced by electrical explosion of wire and used in metal sulfides synthesis is presented. Sulphur excess effect on metal nanopowders combustion with elementary sulphur and phase composition of products is studied. Tungsten and molybdenum disulfides obtained by self-propagating high-temperature synthesis under argon pressure 3 MPa and sulphur excess 15 wt. % in initial mixture are crystallized in layered aggregates with layer thickness 20-30 nm.