Vladimir An

Study of tribological properties of nanolamellar WS 2 and MoS 2 as additives to lubricants

This work was aimed at studying the tribological properties of nanolamellar tungsten and molybdenum disulfides produced from nanosized W and Mo nanopowders by self-propagating high-temperature synthesis. The prepared WS2 and MoS2 powders were examined by scanning electron microscopy (SEM), X-ray diffraction (XRD), and differential thermal analysis (DTA). For tribological tests, oil-based lubricants added with nanolamellar tungsten and molybdenum disulfides were prepared. The tribological tests show that the friction coefficient of the nanolamellar powders is lower than that of commercial powder (µmin = 0.024 and 0.064, resp.). It is also found that the oil-based lubricants with nanolamellar disulfide additives display higher antifriction and antiwear properties compared to commercial powder.

Tribological properties of nanolamellar MoS 2 doped with copper nanoparticles

This study aimed at examining the tribological properties of nanolamellar molybdenum disulfide doped with copper nanoparticles. Nanolamellar molybdenum disulfide was produced using self-propagating high-temperature synthesis via the reaction between elementary sulfur and nanosized molybdenum powder prepared by electrical explosion of wires. Copper nanoparticles were also prepared by electrical explosion of copper wires. Comparative tribological tests were carried out for nanolamellar and commercial molybdenum disulfides doped with 7wt.% of copper nanoparticles. It was demonstrated that doping copper nanoparticles additives reduce wear of the friction body when using both commercial and nanolamellar molybdenum disulfide.

Properties of copper and molybdenum sulfide powders produced by self-propagating high-temperature synthesis

Copper and molybdenum sulfide nanopowders were prepared by self-propagating high-temperature synthesis in argon. The initial copper powder and molybdenum powder were produced by electric spark dispersion in hexane and by electrical explosion of wires (EEW) in argon, respectively. The powders were studied by electron microscopy, X-ray diffraction and Raman spectroscopy. The copper sulfide main phase is hexagonal 2H-CuS, whereas hexagonal 2H-MoS2 and rhombohedral 3R-MoS2 are characteristic for molybdenum disulfide. The lattice parameters of copper and molybdenum sulfides were calculated. The average particle size of copper sulfide and molybdenum disulfide powders was about 50 nm and 80 nm, respectively.

Study of tribological behavior of Cu–MoS2 and Ag–MoS2 nanocomposite lubricants

Tribological behavior of Cu–MoS2 and Ag–MoS2 nanocomposite lubricant was studied. Cu nanoparticles produced by electrical explosion of copper wires and Ag nanoparticles prepared by electrospark erosion were employed as metal cladding modifiers of MoS2 nanolamellar particles. The tribological tests showed Cu–MoS2 and Ag–MoS2 nanocomposite lubricants changed the friction coefficient of the initial grease and essentially improved its wear resistance.

Study of nanostructured metal sulfides produced by self-propagating high-temperature synthesis

In this work results of a study of nanostructured metal sulfides obtained by self-propagating high-temperature synthesis from metal nanopowder and elementary sulphur are presented. The initial iron, copper, tungsten and molybdenum nanopowders were produced by electrical explosion of wires in argon at operating voltage 24-29 kV. Stoichiometric mixtures of metal nanopowders and sulphur were pressed into cylindrical samples which were then placed into the reactor - a constant pressure chamber. Synthesis was carried out in argon at 30 atm. The initial metal nanopowders and synthesized metal sulfides were characterized by XRD, SEM, DTA-TGA methods. According to the XRD analysis the main phases in the obtained powders were FeS, CuS, WS2 and MoS2. The mean size of coherent scattering regions was 35 nm for FeS, 49 nm for CuS, 58 nm for WS2 and 78 nm for MoS2. According to the SEM results particles of tungsten and molybdenum disulfides were agglomerated and had a nanolamellar structure. As DTA-TGA shows synthesized nanolamellar WS2 and MoS2 are thermostable up to 400°C.

Formation of WS2/MoS2 Particles with Nanoscale Layers for Multipurpose Application

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.

Colloid stability of iron compounds in groundwater of Western Siberia

The paper reports on experimental modeling of the colloid system composition in natural groundwater. Iron hydroxide is found to be the main component of natural colloid systems. It is shown that silicon compounds and dissolved organic substances (DOS) stabilize iron hydroxide (III), forming a stable colloid system, and preclude coagulation. The presented results suggest that CaCl2 and AlCl3 electrolytes affect the coagulation stability of synthesized model colloid solutions.

Properties of WS 2 films prepared by magnetron sputtering from a nanostructured target

Tungsten disulfide films were prepared by magnetron sputtering from a laboratory and a nanostructured targets. The nanostructured target was produced from WS2 nanolamellar particles prepared by self-propagating high-temperature synthesis in argon. The main phase in the films was 2H-WS2. According to the X-ray analysis, the films sputtered from the laboratory target and from the nanostructured one reveal different planes of film growth orientation.

Composition and Band Gap Tailoring of Crystalline (GaN)1–x(ZnO)x Solid Solution Nanowires for Enhanced Photoelectrochemical Performance

Photoelectrochemical water splitting has emerged as an effective artificial photosynthesis technology to generate clean energy of H2 from sunlight. The core issue in this reaction system is to develop a highly efficient photoanode with a large fraction of solar light absorption and greater active surface area. In this work, we take advantage of energy band engineering to synthesize (GaN)1- x(ZnO) x solid solution nanowires with ZnO contents ranging from 10.3% to 47.6% and corresponding band gap tailoring from 3.08 to 2.77 eV on the basis of the Au-assisted VLS mechanism. The morphology of nanowires directly grown on the conductive substrate facilitates the charge transfer and simultaneously improves the surface reaction sites. As a result, a photocurrent approximately 10 times larger than that for a conventional powder-based photoanode is obtained, which indicates the potential of (GaN)1- x(ZnO) x nanowires in the preparation of superior photoanodes for enhanced water splitting. It is anticipated that the water-splitting capability of (GaN)1- x(ZnO) x nanowire can be further increased through alignment control for enhanced visible light absorption and reduction of charge transfer resistance.

Use of Zinc Oxide Nanopowder as an Additive in a Tribotechnical Composite Based on Refractory Metal Disulfide

Tribological properties of a composite mixture based on zinc oxide nanoparticles and nanolamellar tungsten and molybdenum disulfide powders have been studied. XRD and TEM of ZnO nanoparticles produced by electric discharge of metallic granules in an H2O2 solution were analyzed. The tribological tests showed ZnO nanoparticles additive in metal disulfide powders did not practically change the friction coefficient in comparison with pure WS2 and MoS2 powders at 25 °C in air. At 400 °C zinc oxide nanoparticles in composite lubricants positively affect the wear resistance.