Hexagonal boron nitride (h-BN) nanosheets, spherical W nanoparticles, and their combinations were utilized as lubricant additives to synthetic PAO6 oil. The addition of W NPs led to a decrease in the ...coefficient of friction and wear rate. Molecular dynamics (MD) simulations and in situ TEM mechanical tests showed that the positive effect of adding spherical W NPs can be attributed to their rolling and sliding in the tribological contact zone. Adding BN nanosheets to PAO6 also improved the tribological performance of friction pairs: MD simulations suggest that the exfoliation and sliding of BN layers under tribological contact can contribute to the reduction of friction and wear. Moreover, a synergistic effect from the simultaneous addition of W and BN nanoparticles was observed: the CoF and wear reached minimum values among all tested suspensions. The formation of W/BN core/shell structures by wrapping of W nanoparticles by h-BN sheets provided superior macroscale lubricity.
•h-BN nanosheets and spherical W nanoparticles are studied as additives to PAO6 oil.•Adding W and BN NPs leads to a decrease in the friction coefficient and wear rate.•Exfoliation and sliding of h-BN NPs contribute to friction and wear reduction.•W NPs can withstand a high applied load and slide or rotate in the direction of applied load.•Formation of W/BN core/shell structures provides superior macroscale lubricity.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
The offshore and coastal infrastructure needs additional protection from wear, corrosion, and tribocorrosion. Herein, electrospark deposition (ESD) was employed to deposit composite TaC-(Fe,Mo,Ni) ...and (Ta,Zr)C-(Fe,Mo,Ni) coatings with a metallic matrix (similar in elemental composition to that of stainless steel) reinforced with carbide nanoparticles. The coatings were produced using TaC–Mo–Ni and TaC–ZrC–Mo–Ni electrodes under different energy regimes by varying frequency, voltage, and pulse duration to obtain different carbide contents. The obtained coatings have a bilayer composite structure: core-shell TaC–ZrC crystallites embedded in an Fe-based metal matrix with a (Ta,Zr)C network (zone 1) and approximately 5 nm Fe-based nanocrystallites surrounded by amorphous interlayers (zone 2). The tribological properties of TaC-(Fe,Mo,Ni) and (Ta,Zr)C-(Fe,Mo,Ni) coatings were superior to those of uncoated AISI 304 stainless steel, both in the 3.5% NaCl solution and in 3.5% NaCl + SiC suspension. The electrochemical characteristics of the best coatings were comparable to those of the stainless steel. Tribocorrosion tests indicated that when load is applied, the open-circuit potential values of steel reduce more significantly than those of the coatings.
Display omitted
•Composite Ta(Zr)C-(Fe,Mo,Ni) coatings obtained by electrospark deposition in vacuum.•Carbide grains with core-shell structure: Zr-rich core, Ta-rich shell.•Coatings with enhanced tribological properties in 3.5% NaCl and SiC suspension.•In stationary corrosion Ta(Zr)C carbides protect Fe-based matrix.•At polarization, corrosion is determined by dissolution of more active matrix phase.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Methods for targeting enzymes exhibiting anticancer properties, such as methionine γ-lyase (MGL), have not yet been sufficiently developed. Here, we present the data describing the physico-chemical ...properties and cytotoxic effect of fusion protein MGL-S3 - MGL from Clostridium sporogenes translationally fused to S3 domain of the viral growth factor of smallpox. MGL-S3 has methioninase activity comparable to native MGL. In solution, MGL-S3 protein primarily forms octamers, whereas native MGL, on the contrary, usually forms tetramers. MGL-S3 binds to the surface of the neuroblastoma SH-SY5Y and epidermoid carcinoma A431 cells and, unlike native MGL, remains there and retains its cytotoxic effect after media removal. In HEK293T cells lacking EGFRs, no adhesion was recorded. Confocal fluorescence microscopy confirms the preferential adhesion of MGL-S3 to tumor cells, while it avoids getting into lysosomes. Both MGL and MGL-S3 arrest cell cycle of SH-SY5Y cells mainly in the G1 phase, while only MGL-S3 retains this ability after washing the cells.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
The present paper gives a detailed description of structural changes in three types of MoCN–Ag coatings (Mo51C15N27Ag7, Mo40C31N23Ag6, and Mo43C14N40Ag3) during dynamic temperature ramp tribological ...tests with particular emphasis on the analysis of wear products to identify adaptive friction mechanisms in the temperature range between 250 and 550°C. Thorough structural characterization using high-temperature XRD, SEM, TEM, GDOES, and Raman spectroscopy provided evidence of various tribo-chemical reactions in the zone of tribological contact affecting lubrication. The coating lubrication in the temperature range between 100 and 400°C was observed to be different. Unlike Mo51C15N27Ag7 coating whose friction coefficient monotonously increased with increasing temperature from 25 to 250°C, the Mo40C31N23Ag6 coating demonstrated low values of friction coefficient up to 250°C due to the tribo-activated formation of carbon-based fibers normal to the sliding direction. The good lubrication of the Mo43C14N40Ag3 coating at elevated temperatures was attributed to almost no wear due to its high hardness and to the formation of a thin tribo-activated MoO3 film at 350°C. However, complete oxidation of the wear track at 400°C resulted in intensive abrasion wear and high friction. Above 400°C, all coatings demonstrated similar values of friction coefficient irrespective of phase composition (melt, Ag6Mo10O33, or MoO3+Ag).
Display omitted
•Low-friction coatings for broad temperature range•Various tribo-chemical reactions in the tribological contact zones at elevated temperatures•Low friction coefficients due to tribo-activated formation of carbon-based fibers•Good lubrication of MoCN–Ag coatings at elevated temperatures due to almost no wear•Tribo-activated formation of silver molybdate rods with turbostratic structure at 550°C
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
Al-based composites with enhanced thermomechanical properties are in high demand. However, obtaining a uniform distribution of the strengthening phase in the metal matrix and achieving a strong ...metal/ceramic interface is still a great challenge. In this work, nanoAl/nanoSiC powder mixtures after high-energy ball milling were treated with Ar microwave plasma. Plasma processing was designed to remove the initial oxide film covering Al nanoparticles (NPs) and adsorbed impurities from the surface of SiC NPs, improve the wetting of SiC with Al melt, prevent SiC nanoparticle agglomeration, and ensure their uniform distribution in the metal matrix. During plasma treatment, Al/SiC composite particles were obtained, which were subsequently utilized as ready-made structural blocks with uniformly distributed reinforcing SiC NPs to obtain Al/SiC composites with 5, 10, and 30 wt% of SiC. Spark plasma sintered Al/SiC composites using plasma-treated powder mixtures showed approximately 20% higher tensile strength. The addition of 10% SiC led to an increase in hardness by 480% (145 HV), tensile strength by 70% (317 MPa) and 95% (238 MPa) at 25 °C and 500 °C, respectively, compressive strength by 135% (578 MPa), and wear resistance by 35–50%. The effect of point defects at the Al/SiC interface, such as impurity oxygen atoms and Si monovacancies, on the binding energy and temperature-dependent critical shear stress at the interface was assessed using molecular dynamics simulations with machine learning interatomic potentials. Our study demonstrated that the plasma-chemical treatment of Al/SiC powder mixtures is a promising approach for improving the thermomechanical properties of the Al/SiC composites.
•Al/SiC composites obtained by high-energy ball-milling and spark plasma sintering.•Microwave Ar plasma treatment of nanoAl/nanoSiC powder mixtures prevents SiC agglomeration.•Plasma processing leads to uniform distribution of SiC nanoparticles in Al matrix.•Adding 10% SiC significantly increases composite strength at room and elevated temperatures.•Silicon vacancies and oxygen atom impurities at Al/SiC interface increase critical shear stress.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Powders based on tantalum disilicide and silicon carbide were fabricated by mechanical activation-assisted SHS of reaction mixtures, with SiC concentration varied from 10 to 70%. The single- and ...double-layer composite targets were produced by hot pressing and further utilized for deposition of Si-Ta-C-(N) coatings by magnetron sputtering. The optimal hot pressing regimes, which allowed the production of dense ceramics with a hierarchical structure at 10 and 30% SiC, were determined. These ceramics were characterized by a relative density of 96–97%, hardness of ~19 GPa, and fracture toughness of 6.5–6.7 MPa × m1/2. The nanocomposite Si-Ta-C-N coatings consisted of fcc Ta(Si,C,N) solid solution (TaSi2–30%SiC target) and Ta5Si3 compound (TaSi2–10%SiC target) embedded in an amorphous matrix. Depending on the elemental composition, hardness and Young's modulus of the coatings were 16–26 GPa and 155–268 GPa, respectively. The coatings are characterized by high thermal stability and oxidation resistance at temperatures up to 800 °C. Tribological tests demonstrated the decrease of the coefficient of friction (CoF) of the coatings with increasing temperature: from 0.38 (25 °C) to 0.28 (600 °C) and 0.23 (800 °C). The low wear rate and CoF of the Si-Ta-C-N coatings at elevated temperatures are explained by the formation of a thin (~100 nm) oxide layer and TaSixOy microfibers on the coating surfaces.
•TaSi2-SiC powders were fabricated by mechanical activation-assisted combustion synthesis.•TaSi2-xSiC targets (x = 10, 30) had high relative density, hardness, and fracture toughnes.•Si-Ta-C-(N) coatings consisted of small (<3 nm) Ta(Si,C,N) or Ta5Si3 crystallites embedded in an amorphous matrix.•Si-Ta-C-(N) coatings showed high thermal stability and oxidation resistance at temperatures up to 800 °C.•Si-Ta-C-(N) coatings demonstrated low friction and wear rate at elevated temperatures.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
•TiAlSiCN/MoSeC coatings for tribological applications.•Doping with MoSeC reduces friction coefficient in humid air from 0.8–0.9 to 0.05.•Doping with MoSeC increases wear resistance by one-two orders ...of magnitude.•TiAlSiCN/MoSeC coatings demonstrated low friction coefficient in distilled water.•TiAlSiCN/MoSeC coatings showed superior tribological properties at moderate temperatures.
The present paper is focused on the development of hard tribological coatings with low friction coefficient (CoF) in different environments (humid air, distilled water) and at elevated temperatures. TiAlSiCN/MoSeC coatings were deposited by magnetron sputtering of four-segment targets consisting of quarter circle TiAlSiCN segments, obtained by self-propagating high-temperature synthesis, and one or two cold pressed segments made of MoSe2 and C powders in a ratio 1:1 wt%. The structure and phase composition of coatings were investigated by means of X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy, and Raman spectroscopy. The coatings were characterized in terms of their hardness, elastic modulus, and elastic recovery. The tribological properties of coatings were investigated first at room temperature against Al2O3 and WC–Co balls, after which studied in distilled water and during continuous heating in air in the temperature range of 25–400°C against Al2O3 counterpart material. To evaluate their electrochemical characteristics, the coatings were tested in 1N H2SO4 solution. The obtained results show that the coating hardness depends on the amount of MoSeC additives and decreased from 40 to 28 (one MoSeC segment) and 12GPa (two MoSeC segments). Doping with MoSeC resulted in a significant reduction of CoF values measured in humid air (RH 60±5%) from 0.8–0.9 to 0.05 and an increase of wear resistance by one or two orders of magnitude depending on counterpart material. This was attributed to the presence of MoSe2 and free carbon-based phases in the tribological contact. The TiAlSiCN/MoSeC coating with a maximal amount of MoSeC also demonstrated superior tribological characteristics in distilled water (CoF∼0.1) and at moderate temperatures up to 300°C (CoF<0.1). The electrochemical tests showed that, in general, doping with MoSeC did not negatively affect the coating electrochemical behavior. On the contrary, the MoSeC phase demonstrated small positive effect on the anti-corrosive properties of TiAlSiCN coatings under small polarizations.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
ABSTRACT
Baikal-GVD has recently published its first measurement of the diffuse astrophysical neutrino flux, performed using high-energy cascade-like events. We further explore the Baikal-GVD cascade ...data set collected in 2018–2022, with the aim to identify possible associations between the Baikal-GVD neutrinos and known astrophysical sources. We leverage the relatively high angular resolution of the Baikal-GVD neutrino telescope (2–3 deg.), made possible by the use of liquid water as the detection medium, enabling the study of astrophysical point sources even with cascade events. We estimate the telescope’s sensitivity in the cascade channel for high-energy astrophysical sources and refine our analysis prescriptions using Monte-Carlo simulations. We primarily focus on cascades with energies exceeding 100 TeV, which we employ to search for correlation with radio-bright blazars. Although the currently limited neutrino sample size provides no statistically significant effects, our analysis suggests a number of possible associations with both extragalactic and Galactic sources. Specifically, we present an analysis of an observed triplet of neutrino candidate events in the Galactic plane, focusing on its potential connection with certain Galactic sources, and discuss the coincidence of cascades with several bright and flaring blazars.
Display omitted
•Si-Ta-C-(N) consists of fcc Ta(C,N) grains and amorphous a-Si and a-SiC(N) phases.•Ion implantation improved thermal shock resistance of the coatings.•Si-Ta-C-(N) coatings are ...resistant to oxidation at 800 °C.•The formation of TaSiOx fibers results in a low coefficient of friction, 0.23, at 800 °C.•Excellent wear resistance was achieved due to high ductility of the N-doped coatings.
Challenges related to the application of wear resistant coatings at high temperatures require the development of novel materials with an exceptional combination of mechanical, chemical and tribological properties. The present paper is focused on understanding of relationships between structure, composition and high-temperature performance of the Si-Ta-C-(N) coatings. The coatings were produced using combined magnetron sputtering (MS) and ion implantation (CMSII) technique. It was found that ion implanted coatings demonstrated better thermal shock resistance compared to MS Si-Ta-C-(N) coatings. The Si-Ta-C-(N) coatings revealed a nanocomposite structure consisting of 2–3 nm fcc TaC(N) grains and amorphous a-Si and a-SiC(N) phases. The composition and structure of amorphous matrix and nanocrystallites strongly affected tribological performance of the Si-Ta-C-(N) coatings. The N-doped coatings exhibited exceptionally good tribological performance due to a higher ductility of N-rich amorphous a-SiCN and a-SiNx matrix, and fcc Ta(C,N)-based crystallites compared with the a-Si + a-SiC, and fcc TaC-based phases in N-free coating. The Si-Ta-C-(N) coatings easily withstood oxidation annealing at 800 °C due to the formation of a 200 nm protective TaSiOx amorphous layer. Oxidation annealings revealed that under thin protective TaSiOx layer crystalline components of coatings did not change when Si and C from the amorphous matrix started to diffuse towards the substrate at 800 °C but even after redistribution of elements and formation of oxide scale the coatings demonstrated reasonably high hardness – 13–16 GPa. Triboactivated formation of TaSiOx fibers which could slide/roll against the same TaSiOx tribolayer during high-temperature tribotests resulted in low coefficient of friction values (0.23 at 800 °C) and absence of wear.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
High-entropy coatings (HECs) are of a great interest for the protection of structural steels and alloys used in the costal and offshore areas. Here, thick, dense, and uniform Fe-Cr-Ni-Co-(Cu) ...coatings with a crack-free surface have been successfully deposited on AISI 420S steel by vacuum electro-spark deposition using CrNiCo and CrNiCoCu electrodes. The coatings consist of columnar grains (approximately 300 nm in diameter) and subgrains (10–50 nm thick) of an fcc phase and spherical inclusions of mixed SiO2 + (Cr,Ti)2O3 oxide, 30–50 nm in size. Although Cu is an element prone to segregation, the experimental results show that Cu does not form its own phase and is in the metal solid solution. Molecular dynamics simulation shows that Cu has a slight tendency to self-clustering and form Cu-rich clusters in FeCrNiCo-Cu HECs. However, several regions enriched in Cu are observed in the FeCrNiCo-Cu samples. FeCrNiCo coatings tested in artificial seawater and the Black Sea exhibited enhanced corrosion resistance. In tribocorrosion tests, FeCrNiCo-(Cu) coatings performed better than steel substrate due to faster recovery of a passive film. The addition of Cu has a positive effect on the antibacterial activity of FeCrNiCo coatings against Gram-positive B. cereus Arc30 and B. cereus F strains.
Display omitted
•High-entropy FeCrNiCo-(Cu) coatings prepared by vacuum electrospark deposition•Single-phase fcc structure with columnar subgrain morphology and oxide inclusions•Superior corrosion and tribocorrosion resistance in seawater•Cu doping led to enhanced antibacterial activity against B. cereus strains.•Molecular dynamics simulation results correspond to experimental data.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
