CoCrNi medium-entropy alloy has demonstrated remarkable mechanical properties,suggesting its potential as a structural material.Nevertheless,the challenge lies in achieving an elusive combination of high hardness and ...CoCrNi medium-entropy alloy has demonstrated remarkable mechanical properties,suggesting its potential as a structural material.Nevertheless,the challenge lies in achieving an elusive combination of high hardness and inherent self-lubrication on the worn surface,which is crucial for attaining exceptional tribological performance in medium-entropy alloy(MEA).This study reports the preparation of a novel CoCrNi-based self-lubricating composite by powder metallurgy,which is reinforced simultaneously with Ag solid lubricating phase and SiC ceramic particles.During the sintering process,SiC decomposes to form high hardness in situ Cr_(23)C_(6),enabling the composite to achieve high load-bearing capacity.During the sliding process,thick and dense Ag self-lubricating film is successfully achieved due to the mechanical and thermal effects.The protective tribo-layer effectively mitigates surface stress concentration induced by wear,thereby inhibiting surface coarsening and substantially enhancing the tribological performance.The results showed that compared with CoCrNi MEA,the wear rate and friction coefficient of CoCrNi/SiC/Ag composite are reduced by 88.1%and 32.8%,respectively,showing superior tribological properties over most MEA-based self-lubrication composites.This study further elucidates the wear mechanism of CoCrNi/SiC/Ag composite,providing a new strategy for developing self-lubricating materials with excellent comprehensive performance,which overcomes the inherent trade-off between wear resistance and lubrication.展开更多
With the global oil and gas industry increasingly targeting ultra-deep well development,the demand for wear resistance in polycrystalline diamond compact(PDC)bits is increasing.However,further improvement of the mecha...With the global oil and gas industry increasingly targeting ultra-deep well development,the demand for wear resistance in polycrystalline diamond compact(PDC)bits is increasing.However,further improvement of the mechanical properties of PDC incurs prohibitively elevated costs and stringent technological challenges.Here,we present a two-stage high-pressure infiltration(HPI)methodology involving cobalt removal pretreatment followed by lubricant infiltration.The successful infiltration of lubricants into diamond micropores has been systematically verified,and the effects of lubricant phase composition,infiltration pressure,and temperature on infiltration depth have been thoroughly investigated.Fractal dimension analysis characterizes the pore structure of cobalt-removed diamonds,revealing a strong correlation between the fractal dimension and friction coefficient reduction.Tribological testing confirms the formation of lubricating films at friction interfaces,achieving a 71.5%reduction in the coefficient of friction for lubricant-containing diamond materials.This straightforward strategy opens a gate to developing the next generation of self-lubricating diamond materials.展开更多
[Objective] This study aimed to investigate the effects of different padding on ammonia concentration in broiler house and growth performance and blood indi- cators of broilers. [Method] A total of 480 one-day-old 817...[Objective] This study aimed to investigate the effects of different padding on ammonia concentration in broiler house and growth performance and blood indi- cators of broilers. [Method] A total of 480 one-day-old 817 broilers were selected. They were randomly divided into four groups with different paddings, and each group was in triplicate. The weights of broilers and feed were weighed weekly. The growth performance of broilers was determined. On day 30, the ammonia concentra- tions in broiler houses were determined. On day 35, 6 broilers were randomly se- lected from each group, and their vein blood was sampled. In the sampled vein blood, the concentrations of ammonia, glucose, globulin, serum total protein and urea nitrogen were determined. [Result] There were significant differences in ammo- nia concentration among broiler houses laid with different paddings （P〈0.05）. The ammonia concentration in group 1 was significantly lower than those in group 3 and group 4 （P〈0.05）. No significant difference was found in ammonia concentrations in broiler houses between group 2 and group 3 （P〉0.05）. The ammonia concentration in group 4 was significantly higher than those in group1, group 2 and group 3 （,0〈 0.05）. There were also significant differences in blood indicators among different groups （P〈0.05）. The blood ammonia, blood glucose and serum urea nitrogen con- centrations in group 1 were significantly lower than those in other groups （P〈0.05）, the serum total protein concentration was significantly higher than those in group 3 and group 4 （P〈0.05）, and the serum globulin concentration was significantly higher than those in group 2, group 3 and group 4 （P〈0.05）. Significant differences were observed in feed intake, body weight gain and slaughter weight between different groups （P〈0.05）, but there were no significant differences in feed to grain ratio （P〉 0.05）. [Conclusion] Under the experimental conditions, the padding of Chinese medicine residue showed better effect on reducing ammonia concentration in broiler house, which was conducive to play of production potential of broilers.展开更多
Aluminum-based composite abradable seal coatings are pivotal to improving the efficiency of aero engines or gas turbines.However,the adhesive transfer frequently occurs between metallic blade tips and aluminum-based c...Aluminum-based composite abradable seal coatings are pivotal to improving the efficiency of aero engines or gas turbines.However,the adhesive transfer frequently occurs between metallic blade tips and aluminum-based composite coatings,resulting in engine vibration and even jam.Many past studies had tried to solve this problem by reducing coating hardness,improving lubrication,or strengthening blade tips,but all had failed.In this paper,we proposed a novel epoxy-based composite abradable seal coating,eliminating adhesive transfer by changing metal-to-metal scraping pair to metal-to-polymer scraping pair.The coating was developed via a hierarchical structure design.Large spherical pores were uniformly distributed in the continuous epoxy matrix with fine graphite dispersion.By adding 20 vol.%graphite and 50 vol.%hollow microspheres,a self-lubricating epoxy-based coating of 0.26 friction coefficient with thermal conductivity of 0.28 W/(m·K),coating HR15 Y hardness at 54.8,and bonding strength at 18.7 MPa can be reached.When the metallic blades scrape the epoxy-based composite coating,no adhesive transfer occurs.Besides,a smooth scraped surface is formed by pseudoplastic deformation.This epoxy-based composite abradable seal coating opens a new way to improve the efficiency and reliable operations of air engine compressors.展开更多
A test method based on the condition simulation and a friction and wear test machine featuring in oscillatory movement were set up for self-lubricating spherical plain bearings (SPB). In the machine the condition para...A test method based on the condition simulation and a friction and wear test machine featuring in oscillatory movement were set up for self-lubricating spherical plain bearings (SPB). In the machine the condition parameters such as load, angle and frequency of oscillation and number of test cycles can be properly controlled. The data relating to the tribological properties of the bearing, in terms of friction coefficient, linear wear amount, temperature near friction surface and applied load, can be monitored and recorded simultaneously during test process by a computerized measuring system of the machine. Efforts were made to improve the measurement technology of the friction coefficient in oscillating motion. In result, a well-designed bearing torque mechanism was developed, which could reveal the relation between the friction coefficient and the displacement of oscillating angle in any defined cycle while the curve of friction coefficient vs number of testing cycles was continuously plotted. The tribological properties and service life of four kinds of the bearings, i.e, the sampleⅠ-Ⅳ with different self-lubricating composite liners, including three kinds of polytetrafluoroethylene (PTFE) fiber weave/epoxy resin composite liners and a PTFE plastic/copper grid composite liner, were evaluated by testing, and the wear mechanisms of the liner materials were analyzed.展开更多
In the dry-sliding process of the woven self-lubricating liner which is used in the self-lubricating spherical plain bearing, the friction heat plays an important role in the tribological performances of the liner. It...In the dry-sliding process of the woven self-lubricating liner which is used in the self-lubricating spherical plain bearing, the friction heat plays an important role in the tribological performances of the liner. It has important value to study on the relationship between tribological performances of the liner and the friction heat. Unforttmately, up to now, published work on this relationship is quite scarce. Therefore, the effect of friction heat on the tribological performances of the liner was investigated in the present work. The tribological behaviors of the liner were evaluated by using the high temperature end surface wear tester. Scanning electron microscopy （SEM） was utilized to examine the morphologies of worn surfaces of the liner and study the failure modes. Differential scanning calorimetry （DSC） measurement and X-ray diffraction （XRD） analysis were performed to study the behaviors of the wear debris. The temperature rise on the worn surface was calculated according to classical models. SEM observation shows that the dominating wear mechanism for the liner is mainly affected by friction shear force, contact pressure and friction heat. Higher fusion heat for the wear debris than that for the pure polytetrafluroethylene （PTFE） indicates that the PTFE is the main portion of the wear debris, and, the PTFE in the wear debris shows a higher crystallisation degree owing to the effects of friction shear force and the friction heat. Combining the calculated temperature rise results with the wear rate of the liner, it can be concluded that the effects of temperature rise o n the tribological performances of the liner become more obvious when the temperature rise exceeds the glass transition temperature （Tg） of the PTFE. The wear resistance of the liner deteriorates dramatically when the temperature rise approaches to the melting point （Ton） of the PTFE. The tribological performances of the liner can be improved when the temperature rise exceeds Tg but is far lower than Ton- The present study on the relationship between the temperature rise and the tribological performances of the liner may provide the basis for further understanding of the wear mechanisms of the liner as well as the relationship between the formation of the PTFE transfer film and the friction heat during the dry-sliding of the Finer.展开更多
基金supported by the Natural Science Foundation of China(Nos.52175188 and 52274367)the Key Research and Development Program of Shaanxi Province(No.2023-YBGY-434)+2 种基金he Open Fund of Liaoning Provincial Key Laboratory of Aero-engine Materials Tribology(No.LKLAMTF202301)Guangdong Basic and Applied Basic Research Foundation(No.2024A1515012378)the Science and Technology on Reactor System Design Technology Laboratory.
文摘CoCrNi medium-entropy alloy has demonstrated remarkable mechanical properties,suggesting its potential as a structural material.Nevertheless,the challenge lies in achieving an elusive combination of high hardness and inherent self-lubrication on the worn surface,which is crucial for attaining exceptional tribological performance in medium-entropy alloy(MEA).This study reports the preparation of a novel CoCrNi-based self-lubricating composite by powder metallurgy,which is reinforced simultaneously with Ag solid lubricating phase and SiC ceramic particles.During the sintering process,SiC decomposes to form high hardness in situ Cr_(23)C_(6),enabling the composite to achieve high load-bearing capacity.During the sliding process,thick and dense Ag self-lubricating film is successfully achieved due to the mechanical and thermal effects.The protective tribo-layer effectively mitigates surface stress concentration induced by wear,thereby inhibiting surface coarsening and substantially enhancing the tribological performance.The results showed that compared with CoCrNi MEA,the wear rate and friction coefficient of CoCrNi/SiC/Ag composite are reduced by 88.1%and 32.8%,respectively,showing superior tribological properties over most MEA-based self-lubrication composites.This study further elucidates the wear mechanism of CoCrNi/SiC/Ag composite,providing a new strategy for developing self-lubricating materials with excellent comprehensive performance,which overcomes the inherent trade-off between wear resistance and lubrication.
基金supported by the National Natural Science Foundation of China(grant number:52203375 and 52073254)。
文摘With the global oil and gas industry increasingly targeting ultra-deep well development,the demand for wear resistance in polycrystalline diamond compact(PDC)bits is increasing.However,further improvement of the mechanical properties of PDC incurs prohibitively elevated costs and stringent technological challenges.Here,we present a two-stage high-pressure infiltration(HPI)methodology involving cobalt removal pretreatment followed by lubricant infiltration.The successful infiltration of lubricants into diamond micropores has been systematically verified,and the effects of lubricant phase composition,infiltration pressure,and temperature on infiltration depth have been thoroughly investigated.Fractal dimension analysis characterizes the pore structure of cobalt-removed diamonds,revealing a strong correlation between the fractal dimension and friction coefficient reduction.Tribological testing confirms the formation of lubricating films at friction interfaces,achieving a 71.5%reduction in the coefficient of friction for lubricant-containing diamond materials.This straightforward strategy opens a gate to developing the next generation of self-lubricating diamond materials.
基金Supported by Innovation Project for Universities and Research Institutes in Jinan City(201303053)Shandong Provincial Science and Technology Plan Project(2014GGH210001)Program of Animal Husbandry and Veterinary Bureau of Shandong Province~~
文摘[Objective] This study aimed to investigate the effects of different padding on ammonia concentration in broiler house and growth performance and blood indi- cators of broilers. [Method] A total of 480 one-day-old 817 broilers were selected. They were randomly divided into four groups with different paddings, and each group was in triplicate. The weights of broilers and feed were weighed weekly. The growth performance of broilers was determined. On day 30, the ammonia concentra- tions in broiler houses were determined. On day 35, 6 broilers were randomly se- lected from each group, and their vein blood was sampled. In the sampled vein blood, the concentrations of ammonia, glucose, globulin, serum total protein and urea nitrogen were determined. [Result] There were significant differences in ammo- nia concentration among broiler houses laid with different paddings （P〈0.05）. The ammonia concentration in group 1 was significantly lower than those in group 3 and group 4 （P〈0.05）. No significant difference was found in ammonia concentrations in broiler houses between group 2 and group 3 （P〉0.05）. The ammonia concentration in group 4 was significantly higher than those in group1, group 2 and group 3 （,0〈 0.05）. There were also significant differences in blood indicators among different groups （P〈0.05）. The blood ammonia, blood glucose and serum urea nitrogen con- centrations in group 1 were significantly lower than those in other groups （P〈0.05）, the serum total protein concentration was significantly higher than those in group 3 and group 4 （P〈0.05）, and the serum globulin concentration was significantly higher than those in group 2, group 3 and group 4 （P〈0.05）. Significant differences were observed in feed intake, body weight gain and slaughter weight between different groups （P〈0.05）, but there were no significant differences in feed to grain ratio （P〉 0.05）. [Conclusion] Under the experimental conditions, the padding of Chinese medicine residue showed better effect on reducing ammonia concentration in broiler house, which was conducive to play of production potential of broilers.
基金financially supported by the National Science and Technology Major Project(No.2017-VII-0012-0107)the National Program for Support of Top-notch Young Professionals。
文摘Aluminum-based composite abradable seal coatings are pivotal to improving the efficiency of aero engines or gas turbines.However,the adhesive transfer frequently occurs between metallic blade tips and aluminum-based composite coatings,resulting in engine vibration and even jam.Many past studies had tried to solve this problem by reducing coating hardness,improving lubrication,or strengthening blade tips,but all had failed.In this paper,we proposed a novel epoxy-based composite abradable seal coating,eliminating adhesive transfer by changing metal-to-metal scraping pair to metal-to-polymer scraping pair.The coating was developed via a hierarchical structure design.Large spherical pores were uniformly distributed in the continuous epoxy matrix with fine graphite dispersion.By adding 20 vol.%graphite and 50 vol.%hollow microspheres,a self-lubricating epoxy-based coating of 0.26 friction coefficient with thermal conductivity of 0.28 W/(m·K),coating HR15 Y hardness at 54.8,and bonding strength at 18.7 MPa can be reached.When the metallic blades scrape the epoxy-based composite coating,no adhesive transfer occurs.Besides,a smooth scraped surface is formed by pseudoplastic deformation.This epoxy-based composite abradable seal coating opens a new way to improve the efficiency and reliable operations of air engine compressors.
文摘A test method based on the condition simulation and a friction and wear test machine featuring in oscillatory movement were set up for self-lubricating spherical plain bearings (SPB). In the machine the condition parameters such as load, angle and frequency of oscillation and number of test cycles can be properly controlled. The data relating to the tribological properties of the bearing, in terms of friction coefficient, linear wear amount, temperature near friction surface and applied load, can be monitored and recorded simultaneously during test process by a computerized measuring system of the machine. Efforts were made to improve the measurement technology of the friction coefficient in oscillating motion. In result, a well-designed bearing torque mechanism was developed, which could reveal the relation between the friction coefficient and the displacement of oscillating angle in any defined cycle while the curve of friction coefficient vs number of testing cycles was continuously plotted. The tribological properties and service life of four kinds of the bearings, i.e, the sampleⅠ-Ⅳ with different self-lubricating composite liners, including three kinds of polytetrafluoroethylene (PTFE) fiber weave/epoxy resin composite liners and a PTFE plastic/copper grid composite liner, were evaluated by testing, and the wear mechanisms of the liner materials were analyzed.
文摘In the dry-sliding process of the woven self-lubricating liner which is used in the self-lubricating spherical plain bearing, the friction heat plays an important role in the tribological performances of the liner. It has important value to study on the relationship between tribological performances of the liner and the friction heat. Unforttmately, up to now, published work on this relationship is quite scarce. Therefore, the effect of friction heat on the tribological performances of the liner was investigated in the present work. The tribological behaviors of the liner were evaluated by using the high temperature end surface wear tester. Scanning electron microscopy （SEM） was utilized to examine the morphologies of worn surfaces of the liner and study the failure modes. Differential scanning calorimetry （DSC） measurement and X-ray diffraction （XRD） analysis were performed to study the behaviors of the wear debris. The temperature rise on the worn surface was calculated according to classical models. SEM observation shows that the dominating wear mechanism for the liner is mainly affected by friction shear force, contact pressure and friction heat. Higher fusion heat for the wear debris than that for the pure polytetrafluroethylene （PTFE） indicates that the PTFE is the main portion of the wear debris, and, the PTFE in the wear debris shows a higher crystallisation degree owing to the effects of friction shear force and the friction heat. Combining the calculated temperature rise results with the wear rate of the liner, it can be concluded that the effects of temperature rise o n the tribological performances of the liner become more obvious when the temperature rise exceeds the glass transition temperature （Tg） of the PTFE. The wear resistance of the liner deteriorates dramatically when the temperature rise approaches to the melting point （Ton） of the PTFE. The tribological performances of the liner can be improved when the temperature rise exceeds Tg but is far lower than Ton- The present study on the relationship between the temperature rise and the tribological performances of the liner may provide the basis for further understanding of the wear mechanisms of the liner as well as the relationship between the formation of the PTFE transfer film and the friction heat during the dry-sliding of the Finer.
