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As a promising lubricate additive, the excellent lubrication performance of graphene oxide (GO) is attributed to the formation of GO tribofilm. However, the poor adsorption of GO on engineering materials surfaces limits the formation of tribofilm, resulting in losing the expected lubricating performance as a lubricant additive. In this study, to improve the adsorption of GO on bearing steel, the boronized functionalization layer was prepared on a bearing steel surface by an electrochemical boronizing process. Our experiment results indicate that an ultralow friction state with a friction coefficient (COF) of 0.03 was achieved on the boronized surface lubricated with 1 wt% GO nanosheets as water-based additives. Together with TEM, EDS and Raman analysis, we confirmed the formation of GO tribofilm with a thickness of 280 nm on the sliding surface due to the synergistic effect of the boronized surface and GO. Molecular dynamics (MD) simulation revealed that the high adhesion energy between the boronized surface and GO endows the preferential adsorption of GO on the sliding surface to form the tribofilm. The ultralow interlayer shear strength of GO tribofilm further contributed to the impressive synergistic lubrication performance. Our study expands the application scope of the ultralow friction behavior of GO by enhancing its adhesion energy on the engineering alloy surface. [Display omitted] • Synergistic lubrication effect of GO nanosheets and boronizing surface was proved. • The adhesion energy of GO on steel surface was enhanced by boronizing treatment. • The preferential adsorption of GO on the substrate was ensured during sliding. • A GO tribofilm with a thickness of 280 nm was formed on the sliding surface. • An ultralow friction state was achieved on the steel lubricated by GO solution. [ABSTRACT FROM AUTHOR]

Advanced high-strength steel is widely used in automobile production and manufacturing, for its advantages of light weight, high strength, and good formability. Compared with common steel plate, higher forming forces are required during the stamping forming process of advanced high-strength steel plate due to its continuous strength improvement. The higher forming forces directly result in a sharp increase in the reactive force on the stamping die, which easily cause inevitable fatigue deformation and damage fracture. In view of the above problems, the stamping forming process of an advanced high-strength steel anti-collision beam part and the loading bearing condition of the stamping die were explored. On basis of the theory of topology optimization, the structure of the stamping die was optimized to obtain the qualified stamping parts and the lesser quality punch. A method based on the node contact force conversion was proposed, and the reactive force on the stamping die during the forming process was obtained to function as the load boundary condition of topology optimization. Geometric reconstruction of the stamping die was implemented referring to the topology optimization results. The final result reveals that the lightweight punch and the qualified stamping part without fatigue deformation can be efficiently achieved through topology optimization. [ABSTRACT FROM AUTHOR]

Microemulsion eluents have been found to have excellent potential uses in high-performance liquid chromatography (HPLC). Here, a novel, environmentally benign and simple method using concentration/flow-rate double-gradient elution using a microemulsion eluent was used to separate water- and fat-soluble vitamins simultaneously and rapidly. Preliminary screening experiments were performed to determine the optimum column type, surfactant concentration, co-surfactant to surfactant ratio, oil, mobile phase pH and microemulsion concentration. The resolution and analysis time were simultaneously optimized using concentration/flow-rate double-gradient elution. The optimized method simultaneously separated water- and fat-soluble vitamins using a Venusil ASB C8 column and a combination of isocratic and linear gradient elution modes using a microemulsion mobile phase (solvent A) consisting of 3.5% (w/w) sodium dodecyl sulfate, 10.5% (w/w) n -butanol, 0.8% (w/w) n -octanol and 85.2% (w/w) water and water (solvent B) at pH 2.50. The optimum detection wavelength was 283 nm. The method was validated and used to analyze a solid pharmaceutical sample. [ABSTRACT FROM AUTHOR]

Mechanochemical reactions induced by external stress provide a unique approach for in situ synthesis of carbon tribofilms that can improve friction and wear performance. In this work, we studied how tribofilm formation and tribological performance might be related to the adsorption strength of three additives in polyalphaolefin (PAO4) as base oil, viz., cyclopropanecarboxylic acid (CPCa), cyclopropanemethanol (CPMA), and 1-cyclopropylethanol (CPEA) as characterized by two different surface-active groups –COOH and –OH. Tribo-testing results reveal that addition of 2.5 wt% CPCa to PAO4 gave the lowest friction coefficient and wear volume. FTIR and Raman analysis demonstrate substantial tribofilm formation only in the case when CPCa was used as the oil additive, not CPMA or CPEA, in spite of the fact that all three additives contain the same metastable cyclopropane ring. Thermogravimetric analysis and molecular dynamics simulations indicate the stronger adsorption of CPCa on the iron oxide surface compared with CPMA and CPEA. Weak adsorption of the latter molecules results in their desorption from the surface due to flash heating during tribotesting before they have the chance to participate in mechanochemical reactions required for tribofilm formation. The stronger binding of CPCa to the steel surface is a necessary condition for this type of surface mechanochemistry and appears critical to the efficient formation of carbon-containing tribofilms under our tribo-testing conditions. [ABSTRACT FROM AUTHOR]

The goal of the work is to investigate the flow pattern of MoS 2 nanoparticles, which influences the lubrication properties of the lubricant. The tribological behavior of MoS 2 nanoparticles was studied in unidirectional or reciprocating ball-on-disk sliding tribometer. Friction reduction of 0.25 wt% MoS 2 nanoparticles in reciprocating mode reached 53.1% compared with that of base oil; whereas the friction coefficient of 0.25 wt% MoS 2 nanoparticles in unidirectional mode was similar with that of base lubricant (about 0.18). Flow pattern results of MoS 2 nanoparticles around contact area show that particles piled up heavily in the inlet of contact zone in unidirectional mode, leading to starved lubrication. However, loose net-like aggregations were formed in reciprocating mode, benefiting to reduce friction and wear. [ABSTRACT FROM AUTHOR]

To reduce the dosage of zinc dialkyldithiophosphates (ZDDP) in engine oil, the synthesis and characterization of a novel borate ester containing a phenylboronic group (BDDP) was reported. The thermogravimetric analysis results showed that BDDP had a better thermo-stability compared with that of commercial additives ZDDP and F10A. The tribological properties of the PAO 6 base oils containing BDDP, ZDDP and F10A were studied using a four-ball tester and SRV tribo-meter. The oil with a BDDP concentration of 0.8% showed tribological properties superior to those of the ZDDP and F10-containing oil under varying applied loads and elevated temperature conditions. The elemental composition of the tribological film generated on the worn surfaces of the steel balls was detected by X-ray photoelectron spectroscopy (XPS), and the results indicated that the tribological film was composed of Fe 2 B and B 2 O 3 . Thus, BDDP could be a candidate to replace ZDDP or reduce the dosage of ZDDP in engine oil. [ABSTRACT FROM AUTHOR]

Extreme pressure (EP) lubricant additives form protective tribofilms at the site of contact using the heat and pressure of contact and relative motion. Common EP additives contain undesirable elements such as phosphorus and sulfur. A novel EP lubricant additive, which contains no phosphorus and sulfur, is presented for generating lubricious carbon films. The additive consists of a surface-active molecule with a metastable cycloalkane ring, which dissociates readily during tribological contact to form lubricious carbon films. Friction and wear performance of PAO4 with this additive under a range of loads and speeds were shown to be superior to that without the additive. Optical and scanning electron microscopy and Raman spectroscopy were used to analyze the tribofilms formed on post-test contact surfaces, providing direct evidence for the formation of carbon films. Quantitative kinetics for the carbon tribofilm formation was analyzed as a function of temperature and stress, from which the activation energy for carbon tribofilm formation was obtained. [ABSTRACT FROM AUTHOR]

The purpose of this work was to expand the applications of molybdenum disulfide (MoS 2 ) nanosheet additives by investigating their effectiveness and advantages for lubricating line contacts between bearing steel and medium carbon steel surfaces. The friction and wear effects of MoS 2 nanosheet additives were investigated using block-on-ring tests, and compared with those from zinc dialkyldithiphosphates (ZDDP). Both additives were combined with ISO VG 32 white oil as base fluid. Results suggest 0.25 wt% MoS 2 nanosheets exhibited similar friction coefficient, oil temperature and wear scar width with those of ZDDP at low loads; while the reductions of friction coefficient and wear scar width were 28.6% and 34.3%, respectively, compared to the behavior of ZDDP at high load (459 N). Furthermore, the wear scar widths of the ZDDP containing oil significantly increased in 2 h tests, while they remained constant with a smaller size for 0.25 wt% additives of MoS 2 nanosheets at a load of 326 N. Scanning electron microscope observations showed some pits on the wear scar lubricated with ZDDP, compared with spalls for 0.06 wt% MoS 2 nanosheets. The wear scar was smooth and had a patched film for tests using 0.25 wt% MoS 2 nanosheets. Energy-dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy analysis revealed that the patched surface film was composed of MoS 2 and phosphate, and that film reduced friction coefficient and wear. The results highlight how high concentration MoS 2 nanosheets exhibit significant advantages over ZDDP in reducing friction and wear in high load in line contact. [ABSTRACT FROM AUTHOR]

Surface texturing is one of the effective strategies to improve bioactivity of implantable materials. In this study, hierarchical micro and nano structure (HMN) were fabricated on Co–Cr–Mo alloy substrate by a movable picosecond laser irradiation. Respectively, microgrooves with nano ripples and islands were produced on Co–Cr–Mo alloy by low and high laser power density. X-ray diffraction apparatus (XRD) phase analysis illustrated that substrate was in the phase of γ- face-centered cubic structure (FCC) before laser treatment, while it was in ε-hexagonal closest packing structure (HCP) phase dominant after laser treatment. Cell adhesion and proliferation studies showed that the HMN surface exhibits enhanced adhesion of MC3TC-E1 osteoblast and promoted cell activity. Analyzing of the morphology of osteoblast cells indicated cells were in high ratio of elongation on the HMN surface, while they mainly kept in round shape on the polished surface. Results indicated the formation of hierarchical structure on Co–Cr–Mo alloy was able to improve biological performances, suggesting the potential application in cobalt based orthopedic implants. [ABSTRACT FROM AUTHOR]

Molybdenum disulfide (MoS) nanosheets are a promising lubricant additive for enhanced engine efficiency in cars. However, high-cost production methods and poor dispersion have limited their application in industry. In this study, the ball milling process is demonstrated as a low-cost and high-efficient method for fabrication of oil-dispersible MoS nanosheet, and the ball milling parameters are optimized. Moreover, the lubrication effectiveness of ball-milled MoS nanosheet was also evaluated. Results indicated that well-dispersed MoS nanosheets with a size of 250 nm can be manufactured with optimized surfactants of zinc dialkyldithiphosphates (ZDDP) and polyisobutylene succinimide (PIBS) after being ball milled for 36 h. Tribological results revealed that a friction coefficient of white oil with 0.25% MoS nanosheets reached 0.075, much lower than that of lubricant without nanosheets (0.16). The wear scar radius of 0.015% MoS nanosheets was similar with that of Hertz contact, and the wear scar radius reduction reached 20% compared with that of 1% ZDDP. In addition, EDS and XPS results indicated the formation of a MoS and FeS tribofilm on the wear surface. [ABSTRACT FROM AUTHOR]

Boronized alloys with high surface hardness has been revealed advance in enhancing the anti-wear performance of critical mechanic components. However, its application in industrial production is greatly limited due to the poor mechanical properties with crystallographic orientated brittle borides. In the present study, we demonstrated that high ductility and high strength were achieved for the boronized AlCoCrFeNi 2.1 eutectic high entropy alloy (EHEA) with the formation of nano-sized borides. The AlCoCrFeNi 2.1 EHEA was treated with electrochemical boronizing method, and its phase formation was studied by x-ray diffraction (XRD), electron back-scattered diffraction (EBSD) and focused ion beam-transmission electron microscope (FIB-TEM). Results show that the nano-grained of FeB, NiB and Cr 3 B 4 with size of about 135.5 nm were formed on the boronized layer with non-preferred crystallographic orientation of the phase. The surface hardness of boronized AlCoCrFeNi2.1 EHEA reached to about 18 GPa, being about 4 times higher than that of the original alloy. Further investigation by tensile testing shows that the tensile strength of boronized samples is about 1.2 GPa with a respectable ductility of about 16.04% (± 0.49) tensile ductility to failure. Meanwhile, extension test and digital image correlation (XTDIC) test shows that the boronized layer failed when the tensile ductility is about 5.1%. The disordered nano-grained in the boronized layer benefit in preventing the formation and propagation of cracks, which improved the ductility of the boronized AlCoCrFeNi 2.1 EHEAs. [Display omitted] • The nano-sized borides of FeB, NiB and Cr 3 B 4 with grain size about 135.5 nm was generated on the AlCoCrFeNi 2.1 EHEA surface. • The elongation and strength of boronized EHEA reach 16.04% and 1197 MPa, and the surface hardness reaches 21 GPa. • The fracture of the brittle boronized layer occurred at the strain of 5.1%. • The crystallographic non-oriented nano-sized borides significantly inhibition crack generation and propagation. [ABSTRACT FROM AUTHOR]

The goal of the work is to investigate the lubrication mechanism of MoS 2 nano sheet. Polyisobutyleneamine Succinimide (PIBS) provides the steric repulsion to disperse nanoparticles in oil due to its long carbon chain. In the present study, the tribological behavior of nano-MoS 2 sheet mixed with different percentages of PIBS was explored. The dispersed state and the mode of nano-MoS 2 sheet entering the contact point were studied. Ball-on-disk results illustrated that the COF of nano-MoS 2 in paraffin oil with free of PIBS was 26.2% compared with those containing 3 wt% PIBS, and the reduction of wear depth reached 41.9%. The nano-MoS 2 sheets with 3 wt% PIBS were in discrete state in paraffin oil, which moved with side flow and could not enter the contact area to cause poor lubrication. Aggregation of particles took place in the case of low PIBS concentration and without PIBS, it entered the contact area and formed well-distributed MoS 2 tribofilm to reduce friction and wear. [ABSTRACT FROM AUTHOR]

The compatibility and effectiveness of nanoparticles with the existing additives in formulated oil are still unclear. In the present study, some lubricant additives were selected to modify nanoparticles to obtain friendly capped nano-MoS2. Various polyisobutyleneamine succinimide (PIBS) concentrations were applied to investigate the lubrication effectiveness of capped nano-MoS2. The results showed that the reduction in COF and wear volume of friendly capped nanoparticles without PIBS reached about 35% and 75% in comparison with those of the base oil respectively. However, the average coefficient of friction and wear volume loss of nano oil increased with PIBS concentration in the range of 0.05%-1%. By scanning electron microscope, energy-dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy analysis, it is identified that (i) MoS2 tribofilm was formed on the wear track for the oil with nano-MoS2 and (ii) wear scar was smooth for nano-MoS2 with low PIBS concentration and without PIBS, while it showed plowing wear when containing high PIBS concentration. Copyright © 2016 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Boronizing has been considered as a promising strategy to enhance the surface hardness and corrosion resistance of the new emerged alloys, like CoCrNi medium-entropy alloy (MEA). However, recent studies showed that a brittle silicide layer was generated on the surface for Ni-containing alloys boronizied with the SiC-containing powder (SiC+KBF 4 +B 4 C). In this study, Si-free powder packing (900 °C 4 h) and electrochemical boronizing (900 °C 30 min) methods were explored to obtain the boronized layer for CoCrNi MEA. The morphology, element distributions and phases of the boronized layer were characterized by Scanning Electron Microscopy (SEM) and Energy Dispersive Spectrometer (EDS) and X-ray diffraction (XRD). The results show that the powder-pack boronizing method with 90 wt% B 4 C + 10 wt% NaBF 4 (B 4 C) and electrochemical (EC) methods have the thickest boronized layer (~70 μm) with hardness of about 22 GPa. The boronized layer is dominated by columnar CrB and Co 2 B with obvious preferred orientation and strong texture. In addition, CoB, Ni 2 B and Ni 3 B also exists in the boronized layer, and these two optimal boronizing processes avoid the influence of Si. This study shows that the B 4 C and EC boronizing methods can be considered as the viable alternative strategy for the preparation of strengthened layers. • The optimal boronizing methods were selected to obtain the strengthened layers. • Si-free boride layers were observed on the CoCrNi MEA surface. • The surface hardness reached to 17–22 GPa. • Borides in the boronized layer have obvious preferred orientation and strong texture. [ABSTRACT FROM AUTHOR]

Boronizing has been considered as a promising strategy to enhance the surface hardness and corrosion resistance of the new emerged alloys, like CoCrNi medium-entropy alloy (MEA). However, recent studies showed that a brittle silicide layer was generated on the surface for Ni-containing alloys boronizied with the SiC-containing powder (SiC+KBF 4 +B 4 C). In this study, Si-free powder packing (900 °C 4 h) and electrochemical boronizing (900 °C 30 min) methods were explored to obtain the boronized layer for CoCrNi MEA. The morphology, element distributions and phases of the boronized layer were characterized by Scanning Electron Microscopy (SEM) and Energy Dispersive Spectrometer (EDS) and X-ray diffraction (XRD). The results show that the powder-pack boronizing method with 90 wt% B 4 C + 10 wt% NaBF 4 (B 4 C) and electrochemical (EC) methods have the thickest boronized layer (~70 μm) with hardness of about 22 GPa. The boronized layer is dominated by columnar CrB and Co 2 B with obvious preferred orientation and strong texture. In addition, CoB, Ni 2 B and Ni 3 B also exists in the boronized layer, and these two optimal boronizing processes avoid the influence of Si. This study shows that the B 4 C and EC boronizing methods can be considered as the viable alternative strategy for the preparation of strengthened layers. • The optimal boronizing methods were selected to obtain the strengthened layers. • Si-free boride layers were observed on the CoCrNi MEA surface. • The surface hardness reached to 17–22 GPa. • Borides in the boronized layer have obvious preferred orientation and strong texture. [ABSTRACT FROM AUTHOR]

The as-cast AlCoCrFeNi 2.1 eutectic high-entropy alloy (EHEA) has high fracture strength and ductility, which displays an excellent application prospect in key structural materials. However, its low surface hardness and poor wear resistance at room temperature limit the actual applications in tribology. Here we showed the enhancement of surface strengthening and self-lubrication properties of AlCoCrFeNi 2.1 EHEA by a powder-pack boronizing treatment. SEM and XRD analysis indicate that a double affected layer with a thickness of about 42 μm was formed on the surface at 900 °C for 4 h, which were mainly consisted of Ni 2 Si and FeB. The surface hardness of the alloy was significantly increased from 396 HV to 1108 HV after the treatment. Tribological results show a remarkable self-lubrication property of the boronized EHEA. The friction coefficient of boronized EHEA under the water condition was reduced by 21%, and the corresponding wear volume was decreased by 65%. EDS and XPS analysis demonstrate the formation of silicon/boron-containing tribofilm on the wear scar, which benefits in the achievement of self-lubrication properties with friction and wear reduction under the water condition. Our research provides a general strategy with the powder-pack boronizing method to strengthen AlCoCrFeNi 2.1 EHEA and enhance self-lubrication properties, which would certainly boost its industry application. • An impressive enhancement of surface hardness was achieved after boronizing. • The affected layer showed a double-layer structure, which was mainly Ni 2 Si and FeB. • Boronized EHEA showed the remarkable self-lubrication property in water. • The formed silicon/boron lubrication film benefited in self-lubrication property. [ABSTRACT FROM AUTHOR]

The maintenance cost of a heavy truck increases due to the severe damage of thrust washer in the differential. The wear was usually related to the contact stress concentration. In the study, the finite element analysis (FEA) was performed for identifying the source of the abnormal wear of thrust washer. An improved approach of modifying the surface profile of spider gear back was proposed. FEA simulations were further conducted to investigate the effect of different spider gear back parameters on the tribological behavior of thrust washer. The FEA simulation results were verified by tribological experiments. Results showed that: (i) the abnormal wear of thrust washer pairing the original gear was caused by the local stress concentration; (ii) the local stress concentration could be eliminated by modifying the surface profile of spider gear back; (iii) using the modified spider gear back, the wear mass loss of the thrust washer was reduced significantly; (iv) the promising surface radius of spider gear back was 73.15 mm. [ABSTRACT FROM AUTHOR]

The CoCrNi medium-entropy alloy (MEA) exhibits an impressive ductility, but its low hardness (∼352 HV) and poor wear resistance limit its engineering applications. In this study, a significant increase of surface hardness and enhancement of self-lubrication were achieved for the CoCrNi MEA using powder-pack boronizing. Results indicate that dual reaction layers with a total thickness of about 50 μm were formed on the surface. These two strengthened layers are mainly consisted of silicide (Ni 2 Si) and borides (CoB, Cr 5 B 3). The hardness of the affected region reaches to 11–21 GPa dependence on the cross-sectional depth, being about 6 times higher than that of untreated MEA. In the deionized water condition, the friction and wear rate reductions of the boronizing treated specimen reach to about 25% and 63%, respectively. Energy Dispersive Spectrometer (EDS) and X-ray Photoelectron Spectroscopy (XPS) analysis on the wear scars showed that a silicon/boron-containing tribofilm was formed under the water environment, which reduces the friction coefficient and enhances the wear resistance. Our study demonstrates that powder-pack boronizing is a powerful way to enhance surface hardness and self-lubrication properties of CoCrNi MEA. • Double-strengthened layers were observed on the boronized CoCrNi alloy surface. • An obvious improvement of surface hardness was obtained. • The self-lubrication performance of boronized CoCrNi MEAs in the water is excellent. • The self-lubrication enhancement was due to the formation of silicon-boron based tribofilm. [ABSTRACT FROM AUTHOR]

The boronizing treatment has been an effective way to strengthen and enhance the lubrication performance of alloys. However, the traditional power-pack boronizing method has been limited due to its time-consuming. Improving the boronizing efficiency is highly demanded for the strengthening and industry application of the high-entropy alloys (HEAs). In this study, the electrochemical boronizing strategy was applied to improve the surface hardness and self-lubrication performance of AlCoCrFeNi 2.1 eutectic HEA (EHEA). The microstructure, phase formation and hardness of boronized alloys were studied. Results confirm the high efficiency of electrochemical boronizing to form a boronized layer with a thickness of about 35 μm in 30 min. The surface hardness of the boronized AlCoCrFeNi 2.1 HEA reached to about 18 GPa due to the presence of NiB, FeB and Cr 3 B 4 in the boronized layer. Tribological tests reveal that the self-lubrication property of AlCoCrFeNi 2.1 HEA in water condition was significantly enhanced by the electrochemical boronizing treatment, e.g., the friction and wear reductions reach to about 25% and 80%, respectively. Lubrication mechanism investigation by X-ray photoelectron spectroscopy (XPS) analysis showed the formation of a H 3 BO 3 tribofilm on the sliding surface during the friction process, which effectively reduce friction and wear. This study provided a novel and fast approach for surface hardening and self-lubrication enhancement of HEA systems using the electrochemical boronizing strategy. • A boronized layer was obtained on the AlCoCrFeNi 2.1 alloy surface in 30 min. • The surface hardness was about 4 times higher than that of the original EHEA. • The self-lubrication performance of boronized EHEAs in the water is excellent. • The lubrication enhancement was due to the in-situ formation of H 3 BO 3 tribofilm. [ABSTRACT FROM AUTHOR]

Layered boric acid (BA) nanoparticle was considered as a promising 'green' lubricant additive due to its bio-degradable. However, its unclear lubrication mechanism and poor dispersion stability cause serious concerns for practical applications. Here, highly oil-dispersed alkyl-functionalized BA nanoparticles with size of about 100 nm were fabricated using a scalable strategy. The friction coefficient reached to around 0.11 with the addition of BA nanoparticles, about 30% lower than that of base oil (0.16). Tribological tests show that the wear reduction reached 40%, and the scuffing load capacity was improved by about 3 times. Lubrication mechanism investigation by molecular dynamics (MD) simulation shows that BA molecules preferentially adsorbed on the friction interface through hydrogen bond. A compact net-like adsorption layer from the decomposed nanoparticles, as well as boron-containing tribofilm, was formed on the rubbing surface to enhance lubrication performance. These solid evidences make BA nanoparticle to be a very promising candidate in practical applications as high performance green additive. Image 1 • MD simulation demonstrates the key role of hydrogen bond at friction interface. • Boric acid (BA) molecule preferentially adsorbed on the sliding surface. • Alkyl-functionalized BA nanoparticles were fabricated using a simple strategy. • The oil suspension with BA nanoparticles remains stable for more than 2 months. • Scuffing load capacity was improved by 3 times with the addition of BA nanoparticles. [ABSTRACT FROM AUTHOR]

The commonly accepted interlayer shear mechanism for layered materials as oil additives remains a challenge with the emergence of two-dimensional materials. In this work, the lubrication effectiveness of MoS 2 and BN nanosheets with a similar size was investigated as oil additives using block-on-ring tests. BN nanosheets reveal remarkable anti-wear performance and a reduction of wear depth of about 50%, whereas, the expected friction and wear reduction were not found for MoS 2 nanosheets. X-ray photoelectron spectroscopy (XPS) investigation indicates the generation of boron-based tribofilm for BN nanosheets and MoS 2 -complex tribofilm for MoS 2 nanosheets. Together with the thermal stability analysis, we found that it is the high strength tribofilm with high oxidation resistance, but not the layer structure, that plays a critical role in lubrication enhancement. This study highlights the advance of 'depositing tribofilm' mechanism in novel additive design. Image 1 • Layered materials with similar size and shape were selected. • Expected friction and wear reduction was not found for MoS 2 nanosheets in this study. • BN nanosheets reveal the remarkable anti-wear property with strong tribofilm strength. • It is a challenge to explain the results by using interlayer shear mechanism. • Depositing tribofilm mechanism would be preferable for novel particle additive design. [ABSTRACT FROM AUTHOR]

Alzheimer's disease (AD) is a neurodegenerative disorder characterized by progressive cognitive decline and currently there are no available treatments. Alongside the conventional Aβ and tau hypotheses, neuroinflammation and metabolism disruption have also been regarded as crucial hallmarks of AD. In this study, a novel Chinese formula Nao Tan Qing (NTQ) was developed and shown to improve AD. In vivo experiments showed that NTQ significantly mitigated cognitive impairment, Aβ burden and neuroinflammation in a transgenic AD mouse model (5×FAD). Network pharmacology results revealed that the active components of NTQ could target inflammatory and metabolic pathways. In addition, hippocampal transcriptomics suggested that NTQ regulated signaling pathways related to inflammation and lipid metabolism. Consistently, serum metabolomics further indicated that NTQ could modulate glycolipid metabolism. In summary, a combination of systems pharmacology analysis and biological validation study demonstrates that NTQ could alleviate behavioral abnormality and pathological alterations of AD by targeting glycolipid metabolism and neuroinflammation, and is accordingly a potential therapeutic agent for AD. [Display omitted] [ABSTRACT FROM AUTHOR]

The effective dispersion of carbonaceous soot has a critical effect on the friction and wear properties and thus decreases energy waste and equipment trouble. Molecular dynamics (MD) simulation and experimental study are performed to unravel the dispersion behavior and mechanism of soot agglomerate in lubricating system with effect of dispersant concentration at various pressures and temperatures. The static, confinement and shear models were created with dispersant polyisobutylsuccinimide polyamine (pib). At static conditions, pib molecules could approach and then self-assemble on soot fragments to disperse soot agglomerate. Under confinement conditions with an external pressure imposed, soot dispersion was better than that under static conditions, and the effect of pressure was not remarkable. The best dispersion characteristic was obtained as dispersant increased to 10 wt% exceeding that the dispersants were excessive and induced their self-aggregation. Under shear conditions, 10 wt% pib molecules showed the best dispersion at both 300 K and 373 K, which is considered as a critical value for soot dispersion from the perspective of MD simulations. Finally, the tribological experiments provided a prime validation for MD simulations. The most effective lubrication occurred in 12.5 wt% sample with friction and wear reduction by 51% and 80% compared to 10 wt% sample, respectively, due to the well soot dispersion and possible friction modification of dispersants. [Display omitted] • Dispersion of carbonaceous soot is studied by MD simulation and experiment. • Dispersive and interactive mechanisms are revealed in different models. • Good soot dispersion benefits the reduction in friction and wear. [ABSTRACT FROM AUTHOR]

In high-speed and heavy-load mechanical operations, gears are susceptible to pitting, adhesion, and wear, which resulting tooth breakage and wear failure. In this paper, failed gears are subjected to repair experiments through the integration of laser cladding and boriding, and the tribological performances and post-repair vibration characteristics are also systematically investigated. In comparison to the base material, the average hardness of the boride surface exhibited an increase of up to 8.37 times, while the wear resistance increased to 15.60 times. The wear resistance of the repaired gear is 2.62 times that of the normal gear, and its vibration parameters are commensurate with that of the normal gear, which offers empirical substantiation for the enhancement of gear repair and remanufacturing strategies. • The hardness and wear resistance were increased at least 8 times after situ-boriding laser cladding treatment. • After situ-boriding laser cladding, the vibration and impact of the repaired gear were weakened. • Compared with the normal gear, the wear resistance of the repaired gear increased by 2.62 times. [ABSTRACT FROM AUTHOR]

To simulate the variational working conditions of the titanium fastener in the aero-engine, variable cycle fretting wear tests were carried out for normal loading (80/40 N), frequency (100/30 Hz), displacement amplitude (80/40 µm) and operating temperature (500/350 °C) in a self-lubricating composite coating on TC21 titanium alloy substrate, and the fretting wear behavior and wear mechanism were thoroughly investigated. The results shows that the coefficient of friction (COF) and the wear volume present a significant difference under variable cycle fretting conditions. The specimen exhibits a relatively stable COF under variable operating temperature. Whereas for the specimen under variable displacement amplitude presents a lowest wear volume. The adhesive wear is mainly found in the specimens under variable normal loading and frequency. Whereas for the specimens under variable displacement amplitude and operating temperature, abrasive wear and oxidation wear is mainly dominated, respectively. The dissipated energy calculation results demonstrate that the variable displacement amplitude and operating temperature have greater impact on the fretting wear behavior. The microstructure analysis in the cross-section of specimens reveals that the sub-surface is composed of amorphous-nano crystalline layer, plastic deformation layer and the origin coating. Additionally, the wear mechanism of the specimens under variable fretting conditions were deeply revealed. This work can provide essential information on fretting behavior and mechanism under the variational working conditions. • The fretting wear behavior and mechanism of a composite coating were investigated under variable cycle fretting conditions. • The variation of displacement amplitude has a significant effect on fretting wear. • The amorphous-nano crystalline layer provides a protective role and suppresses wear effectively. • This work can provide essential information on fretting behavior and mechanism under the variational working conditions. [ABSTRACT FROM AUTHOR]

Fretting wear is one of the main factors restricting the fastener service reliability for the high-temperature titanium alloys. Enhancing the high-temperature fretting wear resistance of titanium alloys with laser cladding coatings is an effective method. Thus, in this work, a self-lubricating composite coating was designed and fabricated on the surface of TC21 titanium alloy with laser cladding. Special attentions were made to the effect of the fractions of the hard and self-lubricating phases on high-temperature fretting resistance. In addition, the contribution of laser cladding power was also concerned. The primary phases of the self-lubricating composite coatings are α-Co, CaF 2 , WC, TiC and Cr 23 C 6 , and the reasons for the formation of TiC and Cr 23 C 6 are investigated from a thermodynamic point. The prepared composite coatings are dense and uniform. The crystallographic characteristics and the volume fractions of the hard phases (WC, TiC and Cr 23 C 6) and self-lubricating phase (CaF 2) were revealed, and the effect of grain size on the coating properties was analyzed. The hardness of the coatings were all maintained around 700 HV 0.2 , which was significantly higher than that of the substrate. The composite coating significantly improves the friction and wear resistance at 500 ℃. The hard phase was also found to be the most resistant to friction and wear. The frictional performance of the coating gets better when the hard phase and the self-lubricating phase increase. However, the hard phase contributes more to the high-temperature friction and wear resistance than the self-lubricating phase and the wear volume is 1/40 that of substrate. For the laser cladding power, the higher power can lead to a higher fraction of CaF 2 but a lower fraction of hard phase, causing a decline in COF but an increase in wear volume. The wear mechanisms of the coating and the substrate were analyzed, the subsurface stress distribution state of the wear scars were further analyzed. The current results present new insights on the anti-wear design strategy to the composite coatings consist of hard and self-lubricating phase. [Display omitted] • The high-temperature fretting wear volume is reduced about 40 times. • The strategy to the addition of the hard and lubricating phase were revealed. • The hard phase has a greater impact on the high-temperature fretting wear. • This work guide for the protection of the titanium alloys. [ABSTRACT FROM AUTHOR]

Abstract: Permanent magnetic linear synchronous machines (PMLSMs) are playing a more important role either in transportation systems or magnetic launch systems, for the excellent advantages. It is indispensable to high performance controllers that some machine parameters are known such as the direct axis (d-axis) and quadrature axis (q-axis) inductances. In this paper, self and mutual inductances of the three-phase winding are deduced by basic electric machinery theory, and the measured inductances are analyzed since the mutual inductances and the corresponding terminals among three-phase windings are changing as different phase winding is concerned. The d- and q-axis inductances are measured with the designed circuit, and the experimental measurement method is validated by the comparison between the experimental and finite element method (FEM) results. [Copyright &y& Elsevier]

The technical solution of Unmanned Aerial Vehicle (UAV) has the following features: good controllability; simple thrust control; high precision; long operating life; low cost; strong adaptability, repeatability, maneuverability, and imperceptibility. So the UAV has widespread application prospects. The position sensor of the mover of UAV linear electromagnetic ejection is the key component of control system. It has a direct influence on performance, structure, and reliability of the system. As the sensors such as linear photoelectric encoder and magnetic encoder are not able to meet the demand of high speed control, the paper develops the research on the detection methods of the mover position. First, the paper presents a detection method of mover position based on sliding mode observer. Due to the flicker problem of sliding mode observer, the paper then proposes a detection method based on state observer, and the method can result in smooth detected position of the mover. Finally, the simulated results of the ejection verify the validity of the proposed method. [ABSTRACT FROM AUTHOR]

The critical failure factor and damage mechanism of 316 stainless steel during fretting corrosion under the molten lead-bismuth eutectic (LBE) are specially investigated. Representative F τ - D -cycle curves are shown to reflect the changing process and characteristics of different cycles for each parameter during fretting corrosion tests. The fretting operation regime is the mixed fretting regime (MFR) with minor stroke. The increase in stroke and temperature convert the fretting operation regime from MFR to the gross sliding regime (GSR). According to the dissipated energy and wear volume among all the samples, the results demonstrate more information as follows: the change of dissipated energy and wear volume is positively correlated with stroke, cycle number and temperature. The most serious damage occurred at 450 ℃− 80 µm-2 × 106 cycles. Multivariate linear regression model was established for 18 groups of data, and it was concluded that temperature was the key failure factor within the parameter range of this experiment. The first effect of temperature increase is to increase the rate of diffusion of Ni element into LBE, and the inevitable dissolution corrosion will occur. The problem is that a large number of vacancy defects are generated. The second effect of temperature increase is that the austenite substrate is transformed into ferrite, which cannot resist damage caused by fretting, due to the dissolution of large amounts of Ni. • The degree of wear damage is positively correlated with the stroke, cycle number and temperature. • The contribution of the temperature to the material damage is about 2 times of the stroke and cycle number. • The damage is the most serious at 450 ℃− 80 µm − 2 × 106 cycles. • The dissolution of Ni will transform the substrate from austenite to ferrite which cannot resist damage caused by fretting. [ABSTRACT FROM AUTHOR]

• The Co-based alloy/WC/CaF 2 composite coating is fabricated by laser cladding to improve the fretting wear resistance. • The surface microhardness of the composite coating can reach to 600 HV. • The fretting wear resistance are significantly improved, which can lead to the decrease of the COF and the wear loss. • This work guide for the protection of heat transfer tube in nuclear power plants. The coating fabricated by laser cladding on the surface has been an effective way to strengthen and enhance the wear resistance of alloys. However, the traditional Co-based alloy coatings rarely pay attention to the addition of self-lubrication constituents to form the composite coating. In addition, the effects of the Co-based composite coating on fretting wear resistance were few addressed. In this study, a Co-based alloy/WC/CaF 2 composite coating was fabricated by laser cladding on the surface of 316 stainless steel to improve the surface hardness and self-lubrication performance. The microstructure, phase constituents and fretting wear resistance at both room temperature (RT) and 500 °C were investigated. Results confirm that the composite coating is consisting of α-Co, Cr 23 C 6 and WC phases. And the F element is effectively dissolved into the α-Co phase. The fabricated composite coating is dense and uniform. The microhardness of the composite coating can reach to 600 HV 0.2 due to the presence of WC and Cr 23 C 6 phase. In addition, the grain refinement is another reason resulting in the higher microhardness. Fretting tests demonstrate that the fretting wear resistance at both RT and 500 °C are significantly improved by the composite coating, which can lead to the decrease of the COF and the wear loss. The lower COF can be ascribed to the dissolved F element in α-Co phase, especially at high fretting temperature. Additionally, the composite coating can effectively prevent the oxidation during fretting both at RT and 500 °C. This work provides an excellent method for the metallic materials to improve fretting wear resistance at both RT and high temperature. [ABSTRACT FROM AUTHOR]

Diamond-like carbon (DLC) is a class of amorphous carbon materials used as wear-resistant coatings in tribo-components. The chemical inertness of DLC surfaces, while important in many applications, makes them incompatible with additives in commercial lubricants. Specifically, DLC surfaces do not permit strong adsorption of friction modifier molecules. This study aims at improving the adsorption of these friction modifier molecules on DLC surfaces through an acid treatment. Water contact angle measurements show that such a treatment results in improved hydrophilicity of the DLC. XPS analysis demonstrates 50% increase in the uptake of ArmeenT, an organic friction modifier, on DLC after the acid treatment. This increased ArmeenT adsorption is accompanied by marked decrease in friction in micro-scale friction experiments. [ABSTRACT FROM AUTHOR]

The synergistic effect of lead-bismuth eutectic (LBE) corrosion and fretting on the damage of a 316 stainless steel was thoroughly investigated. The interaction between the LBE corrosion and fretting plays a key role in materials damage. The dissolution of Ni element leads to a large number of vacancies, lattice defects and built-in internal strain, making the material itself more prone to damage during the wear. Additionally, the shear strain induced by fretting can break the oxide layer formed during friction, leading to the exposure of new materials. This study can provide essential information on damage of heat transfer tubes. [Display omitted] • The dissolution of Ni results in the transformation of the substrate from austenite to ferrite, accelerating the fretting. • Shear strain breaks the oxide layer leading to the exposure of new materials to LBE, accelerating the corrosion. • The synergistic effect between LBE corrosion and fretting accelerates the damage of materials. • This work can rich the data of the investigation on the damage of the heat-transfer tubes in nuclear power plants. [ABSTRACT FROM AUTHOR]

TiZrHfTa 0.5 refractory high-entropy alloy (RHEA) shows great strength and ductility trade-off at ambient temperature, and has a lot of potential for use at elevated temperature. In this work, the effect of B element addition on the wear properties at different temperatures was thoroughly investigated. The results revealed that 1 at% B addition sample presents the best tribological properties at elevated temperatures, and borides exhibit a morphology evolution from blocky to acicular with the increasing B content. The wear rates at ambient and elevated temperatures successfully decrease with the increasing B content, which is ascribed to the increasing hardness, the solution strengthening, and the pinning effect at the grain boundaries induced by the second phase. In addition to the B content, the wear test temperature also significantly affects wear properties. With the analysis of the wear behavior and worn surface, it is demonstrated that the lowest wear rate at 600 ℃ is attributed to the continuous and densified oxide layer, while the serious wear at 400 ℃ results from the uncovered matrix and loose oxide layer. This work offers a new method to improve the wear properties of RHEAs at ambient and elevated temperatures. • The addition of B element for TiZrHfTa 0.5 RHEA results in the preferable wear performance at RT, 400 ℃ and 600 ℃. • The wear performance at 600 ℃ for four types of samples present the lowest wear rate. • The continuous and densified oxide layer formed at 600 ℃ contributes to the lowest wear rate. • The loose oxide layer formed in 400 ℃ leads to more metal fragments and more serious wear. [ABSTRACT FROM AUTHOR]

Heat transfer tubes in nuclear power plants are easily damaged by fretting wear. The fretting behaviour of the heat transfer tube related to the lead-bismuth eutectic (LBE) alloys needs to be investigated. In this work, the effect of pre-immersion corrosion in LBE of AISI 316 stainless steel on fretting behaviour is explored in detail. Following short-duration corrosion (specimens denoted C0 and PC1), no significant change occurred during corrosion, and after the fretting test, the wear scars were shallow, with adhesive wear being the dominant wear mechanism. Following long-duration corrosion (specimens denoted PC2 and PC3), the dissolution of Ni and the formation of an oxide layer were the main corrosion mechanisms. After the fretting tests, the wear scars were deep, demonstrating a degraded anti-wear property, and fretting fatigue wear was dominant. The degradation of the fretting wear resistance in specimens PC2 and PC3 can be attributed to the absence of the protection of NiO in the tribolayer, the large grain size, and the weak plastic deformation accommodation ability. The underlying mechanism is the dissolution of Ni induced by pre-immersion corrosion in the LBE. The present work provides useful information on the fretting behaviour of heat-transfer tubes in nuclear power plants related to the LBE environment. • The dissolution of Ni element and the formation of oxide layer are main corrosion mechanisms in LBE. • The pre-immersion corrosion behaviour results in a larger wear loss in the fretting behaviour. • The effect of pre-immersion corrosion on fretting wear mechanisms are illustrated systematically. • This work guide for the protection of heat transfer tube in nuclear power plants. [ABSTRACT FROM AUTHOR]

The influence of anti-oxidation property of nanoparticles on the tribological properties is rarely reported. In this study, the alkyl-functionalized graphene oxide (FGO) and alkyl-functionalized boric acid (FBA) were fabricated as oil additives to explore their lubrication effectiveness. FBA exhibited remarkable lubricating properties which reduced friction coefficient by approximately 24 % and the wear depth by about 94 %. However, the friction coefficient and wear depth of FGO were reduced by only 9.5 % and 44 %, respectively. Worn surface analysis shows a bunch of deep-plowing on rubbing surface in the case of FGO, while the wear scar was smooth and almost wear-free for FBA. Lubrication mechanism analysis by X-ray Photoelectron Spectroscopy revealed the formation of carbon-based tribofilm for FGO and boron-based tribofilm for FBA during rubbing. In the thermal behavior analysis, graphene oxide (GO) nanoparticles were completely decomposed at 650 °C, whereas, B 2 O 3 nanoparticles remained stable. It indicated that the excellent thermal stability and anti-oxidation property of boron-based tribofilm benefited to the lubrication enhancement. This study highlights the importance of oxidation resistance in designing novel nanoparticle additives, and the enhancement of oxidation resistance of GO will be a promising way to further application as oil additives. [Display omitted] [ABSTRACT FROM AUTHOR]

• Enhanced wear-resistance were achieved by reducing the content of Nb in TiZrHfNb. • The wear loss is related to the subsurface instabilities during friction. • Deformation-induced grain refinement and phase transformation enhance wear-resistance. A sliding enhanced wear-resistance can be significantly achieved by reducing the content of Nb element in TiZrHfNb refractory high entropy alloys (RHEAs). The wear loss reduced by half from TiZrHfNb to TiZrHfNb 0.4. The wear loss is directly related to the subsurface instabilities induced by plastic deformation during friction. The origins can be attributed to two factors: i) plastic deformation induced grain refinement; ii) deformation-induced BCC to HCP phase transformation. [ABSTRACT FROM AUTHOR]

Abstract: Potent nicotinamide phosphoribosyltransferase (NAMPT) inhibitors containing 2,3-dihydro-1H-pyrrolo[3,4-c]pyridine-derived ureas were identified using structure-based design techniques. The new compounds displayed improved aqueous solubilities, determined using a high-throughput solubility assessment, relative to previously disclosed urea and amide-containing NAMPT inhibitors. An optimized 2,3-dihydro-1H-pyrrolo[3,4-c]pyridine-derived compound exhibited potent anti-NAMPT activity (18; BC NAMPT IC50 =11nM; PC-3 antiproliferative IC50 =36nM), satisfactory mouse PK properties, and was efficacious in a PC-3 mouse xenograft model. The crystal structure of another optimized compound (29; NAMPT IC50 =10nM; A2780 antiproliferative IC50 =7nM) in complex with the NAMPT protein was also determined. [Copyright &y& Elsevier]

A series of TiZrV 0.5 Nb 0.5 Al x refractory high entropy alloys were prepared by arc-metling, aiming to solve the problems of high density, poor oxidation and wear resistance of refractory high entropy alloys at elevated temperature. The microstructure, mechanical and tribological properties were investigated. The results indicate that the increase in Al addition could promote precipitation of Laves phase in the BCC matrix, thus regulation the mechanical properties. The tribology behavior is strongly dependent on the temperature. Below 400 °C, the wear mechanism is dominated by mechanical wear. In this case, the TiZrV 0.5 Nb 0.5 Al 0.25 alloy with high strength and good ductility at the same time, exhibits optimal wear resistance. When the temperature increases above to 600 °C, the coefficient of friction and the corresponding wear rate dramatically decrease with Al addition, which could be attributed to the preformed formation of dense and stable oxide glazed-layer before wear. Accordingly, the main wear mechanism changes from mechanical wear to oxidation wear. This study provides an effective strategy for improving wear resistance and oxidation resistance of refractory high entropy alloys in a wide temperature range. • Al-containing alloys hardly wear at 600 °C and 800 °C. • The high temperature worn surface of Al-containing alloy has a dense oxide layer. • The Al0.25 alloy has unique needle-like Laves phase and the best wear resistance. [ABSTRACT FROM AUTHOR]

The fretting behaviors of a metastable β titanium alloy with three kinds of microstructures were studied. Special attentions have been paid to the underlying wear mechanism mediated by fretting conditions and microstructural features. The wear volume is more sensitive to the stroke amplitude rather than the normal loading. The mixed abrasive-adhesive wear is dominated in all fretting samples. The microstructural features make a significant contribution to the difference in the wear resistance and subsurface microstructure stability. Due to a large difference in the grain size and the ability of plastic deformation in adjacent grains, the SM (single-phase microstructure) sample is more favorable to initiation and propagation of cracks. The DM (duplex microstructure) and BM (basketweave microstructure) samples, however, have a high resistance ability to fretting wear and subsurface microstructure stability. This can be attributed to the large amounts of the β/α interfaces and the dispersed orientation distribution of α precipitates. The present work offers valuable experimental data for the prediction of fatigue life after fretting. • The fretting behaviors are evidenced to connect with coupling effect of microstructural features and fretting conditions. • The fretting wear volume is more sensitive to the stroke amplitude rather than the normal loading. • The microstructural origins of fretting wear mechanisms are illustrated systematically. • Microstructure features dependence on the subsurface microstructure stability is revealed in detail. [ABSTRACT FROM AUTHOR]

The wear behaviors of γ-TiAl alloy with two typical microstructures, i.e., the lamellar colony microstructure (denoted as the HIPed sample) and the fine equiaxed microstructure (denoted as the heat-treated sample), were thoroughly studied during dry sliding test to resolve the microstructural feature dependence of wear mechanisms. Special efforts have been made to the subsurface stability during sliding by using electron backscatter diffraction (EBSD) techniques. It is demonstrated that both cases present a similarity in the friction coefficients but a disparity in the wear loss. The lower wear loss was achieved in the case of HIPed sample. This can be attributed to the various directions in the local strain induced by plastic deformation during sliding, the crystallographic structure and the coherent interface in the lamellar colony, leading to high resistance ability to the wear. For the case of heat-treated sample, the high plastic deformation ability in the α 2 grains along the surface and the equiaxed morphology generate to high ability to plastic deformation and sliding during friction, contributing to the high wear loss. However, the heat-treated sample presents a high subsurface structure stability according to the local misorientation analysis. The present results provide new information on wear mechanisms of γ-TiAl alloy and may offer a method to enhance its wear resistance by tailoring the microstructural features. • The wear loss in a dry sliding of a γ-TiAl alloy is evidenced to connect with microstructural feature. • Special efforts have been made to the subsurface stability during sliding by using EBSD techniques. • The lower wear loss was achieved in the case of the lamellar colony microstructure. • The fine globular microstructure presents a high subsurface structure stability. [ABSTRACT FROM AUTHOR]

Hot deformation is an important procedure of metastable β titanium alloy for manufacturing. And it is essential to improve the homogeneity of deformation microstructure in titanium alloy. In this work, the stress relaxation processing accompanied by hot compression in a metastable β titanium alloy is designed to resolve the related mechanisms of stress relaxation by examining the microstructure evolution and improve the wear-resistance. The results demonstrated that the stress relaxation processing leads to the modification and evolution in morphology, size, and volume fraction of α precipitates. The α precipitates distribute randomly in β matrix in a fine and equiaxed shape after stress relaxation. The elimination of deformation bands and formation of sub-grains are the mediated mechanism in the β phase during stress relaxation. The stress relaxation makes a significant contribution to reduce the wear loss and improve the microstructure stability during friction. The lower wear loss can be attributed to the formation of fine β sub-grains and the dispersed crystallographic orientations of α precipitates. This work provides an effective method to microstructure refinement and a valuable solution to enhance the wear-resistance by tailoring the microstructural features. • Stress relaxation results in modifications in morphology, size, and volume fraction of α precipitates. • The elimination of deformation bands and formation of sub-grains is stress relaxation mechanism. • The stress relaxation process makes a significant contribution to wear reduction. • This work contributes to microstructure refinement and enhanced wear-resistance. [ABSTRACT FROM AUTHOR]

The chelate ligand 2,9-di(6′-α-phenol-n-2′,5′-diazahexyl)-1,10-phenanthroline (L) was synthesized and fully characterized. This ligand formed six protonated species in the solution. The bindings of the ligand to the nucleotide anions ATP, ADP and AMP were described in detail, with equilibrium constants given for each species formed. The strength of binding increased with the number of protons, corresponding to an increase in the number of hydrogen bonds and an increase in the coulombic attractive forces. At the same time, the coordination properties of the ternary complexes formed from the chelate ligand above, M (M=Zn2+, Cd2+) and adenosine-5′-triphosphate (ATP) were studied. The metal complexes of the chelate recognize the nucleotides via multiple interactions similar to those occurring in the center of enzymes. The hydrolysis of ATP was studied with the mononuclear and trinuclear chelate complexes. [Copyright &y& Elsevier]

The CoNi, CoFeNi and CoCr x FeNi (x = 0.2, 0.6, 1) alloys were undercooled and in-situ observed. Sluggish dendrite growth was found for the CoCrFeNi alloy, e.g., the maximum dendrite growth velocity decreases by nearly two orders from the CoNi (78 m s−1) to the CoCrFeNi (0.83 m s−1) alloy. It was shown that it is the Cr element and its adding amount but not the number of components that plays a more decisive role in sluggish dendrite growth. The current work might be helpful for understanding rapid solidification, thereby further controlling the microstructures and modulating the mechanical properties of high entropy alloys. Image 1 • A metastable BCC phase was identified in the undercooled CoCrFeNi alloy. • Sluggish dendrite growth was found with the increase of the number of components for the equiatomic alloy melt. • It is not the components number but the properties and its adding amount that play important roles in sluggish growth. • The sluggish dendrite growth could be ascribed to the interaction between the interface and component atoms. [ABSTRACT FROM AUTHOR]

The CoNi equiatomic alloy was undercooled and spontaneously solidified using the glass fluxing method. The dendrite growth behaviors were recorded by a high-speed high-resolution camera. Three dendrite growth stages (i.e., the power law growth stage when undercooling Δ T <120 K, the plateau growth stage when 120 K<Δ T <135 K and the linear law growth stage when Δ T >135 K) were found and well predicted by a dendrite growth model. For the as-solidified microstructures, the average grain size increases with undercooling, indicating that unique grain "coarsening" instead of common spontaneous grain refinement occurs. Such a grain "coarsening" phenomenon was ascribed to stress accumulation upon rapid solidification. Furthermore, a plenty of sub-grains were observed within the abnormal coarse grains. From the electron back-scattering diffraction results, the angle difference between neighbouring sub-grains was less than 6°. The current work might be helpful for not only theoretically understanding dendrite growth but also practically controlling the non-equilibrium microstructures. • Rapid solidification of CoNi equiatomic alloy was studied using the glass fluxing method. • Three growth stages were observed and well predicted by the dendrite growth model. • Sub-grains within the coarse grains were identified by electron back-scattering diffraction. • A unique grain "coarsening" phenomenon for the as-solidified microstructures was reported. [ABSTRACT FROM AUTHOR]

Bulk metallic glasses (BMGs) are potential candidate materials for numerous structural applications. However, this class of materials has a major limitation for engineering applications due to their inferior resistance to fatigue wear. In present work, a novel micro-scale repetitive impact test was utilized for fatigue testing of ZrCu-based BMGs (Zr 63.6- x Cu 18 Ni 10.4 Al 8 Fe x , x = 0, 3, 5 at.%), and specific attention was paid to the micro-alloying effect on wear resistance. Transmission electron microscopy of as-cast Zr 58.6 Cu 18 Ni 10.4 Al 8 Fe 5 revealed amorphous structure with the formation of a second glassy phase of few nanometers in diameter. Although these structural changes have minor effects on hardness and modulus, they have a substantial influence on fatigue wear resistance. Phase separation was found to promote numerous shear bands, which induced strain hardening, and improved the crack resistance. Consequently, all these features are considered to contribute the improved wear resistance. On the contrary, a monolithic glass without Fe addition lacks any microstructural features that can provide means for the local arrest of shear bands and incipient fatigue cracks. These findings improve the understanding of the impact fatigue mechanisms and provide suggestions for the future design of BMGs with excellent wear performance. • A micro-scale repetitive impact test has been exploited to explore the fatigue and wear behavior of BMGs. • Minor Fe substitution for Zr leads to the formation of second glassy phase. • Phase separation can have a dramatic effect on the wear resistance. [ABSTRACT FROM AUTHOR]