查看更多>>摘要：Black phosphorus(BP)is a new class of two-dimensional(2D)layered material,which shows the unanticipated characteristics in many aspects including electronics,transistors,sensors,energy storage,batteries,photocatalysis,and other applications due to its high charge carrier mobility,tunable direct bandgap,and unique in-plane anisotropic structure.In addition,BP has drawn tremendous attention in the field of tribology due to the low shear strength,the layered structure,and the weak connected force between the layers by van der Waals interaction.In recent years,many significant progresses have been made in experimental studies on BP materials as solid lubricants or lubrication additives.This work offers a review of researching regarding the tribological properties of BP.Moreover,the lubrication mechanisms of BP as the lubrication additive including the formation of the tribo-film,micro-bearing effect,and self-repair performance are also summarized.Finally,the current challenges and prospects of BP material as lubricant are proposed.
查看更多>>摘要：To explore the research status on mechanism of the skid-resistance for asphalt pavement,the related achievements of the rubber friction,the tire-road contact,and the influence factors were reviewed.The rubber friction was reviewed from the mechanism and rubber friction model.The tire-road contact was studied from the modeling methods,the evaluation methods,and the skid-resistance mechanisms at different conditions.The influence factors of skid-resistance were summarized from different designing processes.This review showed that the appropriate contact or evaluation model should be selected according to the required parameters.Although the finite element method is widely used,the accuracy of the model,the boundary conditions,and the load cases need to be further improved.The optimized aggregates and asphalt binders,reasonable gradation,reasonable geometric design,and strict construction quality control are necessary for good initial skid-resistance.Pavement texture as an important factor affecting skid-resistance should be considered in pavement gradation design,especially for wearing layer technology.
查看更多>>摘要：1-(4-ethylphenyl)-nonane-1,3-dione(0206)is an oil-soluble liquid molecule with rod-like structure.In this study,the chelate(0206-Fe)with octahedral structure was prepared by the reaction of ferric chloride and 1,3-diketone.The experimental results show that when using 0206 and a mixed solution containing 60%0206-Fe and 40%0206(0206-Fe(60%))as lubricants of the steel friction pairs,superlubricity can be achieved(0.007,0.006).But their wear scar diameters(WSD)were very large(532 μm,370 μm),which resulted in the pressure of only 44.3 and 61.8 MPa in the contact areas of the friction pairs.When 0206-Fe(60%)was mixed with PAO6,it was found that the friction coefficient(COF)decreased with increase of 0206-Fe(60%)in the solution.When the ratio of 0206-Fe(60%)to PAO6 was 8:2(PAO6(20%)),it exhibited better comprehensive tribological properties(232.3 MPa).Subsequent studies have shown that reducing the viscosity of the base oil in the mixed solution helped to reduce COF and increased WSD.Considering the COF,contact pressure,and running-in time,it was found that the mixed lubricant(Oil3(20%))prepared by the base oil with a viscosity of 19.7 mPa·s(Oil3)and 0206-Fe(60%)exhibited the best tribological properties(0.007,161.4 MPa,3,100 s).
查看更多>>摘要：Developing functional additive resistant to space atomic oxygen(AO)irradiation through simple molecular design and chemical synthesis to enhance the lubricating performance of multialkylated cyclopentanes(MACs)oil is a significant challenge.Herein,sulfur-containing polyhedral oligomere silsesquioxane(POSS)were synthesize via a click-chemistry reaction of octavinyl polyhedral oligomeric with alkyl sulfide.The reduce-friction(RF),anti-wear(AW)properties and anti-AO irradiation of POSS-S-R as MACs base oil additives in atmospheric and simulated space environments were systematically investigated for the first time.Results demonstrate that POSS-S-R not only possesses outstanding anti-AO irradiation capacity but also effectively improves the RF and AW of MACs in atmospheric or simulated space surroundings.This improvement is due to the excellent anti-AO irradiation properties of the POSS structure itself and the high load-carrying ability of silicon-containing and sulfur-containing compounds generated by tribo-chemical reactions,which effectively separates the direct contact of the friction interface.We believe that this synthesized POSS-S-R is a promising additive for space lubricants.
查看更多>>摘要：With the rapid development of semiconductors,the number of materials needed to be polished sharply increases.The material properties vary significantly,posing challenges to chemical mechanical polishing(CMP).Accordingly,the study aimed to classify the material removal mechanism.Based on the CMP and atomic force microscopy results,the six representative metals can be preliminarily classified into two groups,presumably due to different material removal modes.From the tribology perspective,the first group of Cu,Co,and Ni may mainly rely on the mechanical plowing effect.After adding H2O2,corrosion can be first enhanced and then suppressed,affecting the surface mechanical strength.Consequently,the material removal rate(MRR)and the surface roughness increase and decrease.By comparison,the second group of Ta,Ru,and Ti may primarily depend on the chemical bonding effect.Adding H2O2 can promote oxidation,increasing interfacial chemical bonds.Therefore,the MRR increases,and the surface roughness decreases and levels off.In addition,CMP can be regulated by tuning the synergistic effect of oxidation,complexation,and dissolution for mechanical plowing,while tuning the synergistic effect of oxidation and ionic strength for chemical bonding.The findings provide mechanistic insight into the material removal mechanism in CMP.
查看更多>>摘要：Sliding-induced subsurface microstructure evolution is believed to be decisive for determining the friction and wear performance of metallic contacts as well as the development of tribo-magnetization.This expects to develop a new prediction method of wear state by elucidating the correlation between subsurface microstructure evolution and corresponding magnetic domain changes.Herein,subsurface microstructure evolution including crystal and magnetic domain under tribological action is investigated experimentally.Our results demonstrate that dislocation mediated plastic deformation decisively influences microstructural changes during tribological contact,further determining the magnetic domain structure.Specifically,sliding-induced plastic deformation causes an increase in the width of magnetic domains,but depth-dependent derived microstructure formed under severe plastic deformation such as the refined grains and sub-grains,in turn,promoted the refinement of magnetic domains and their discontinuity,forming depth-dependent magnetic domain structure.These results are helpful to clarify the evolution of tribo-magnetization and the pinning effect of dislocations on magnetic domains.
查看更多>>摘要：Silicon carbide fiber reinforced silicon carbide matrix(SiCf/SiC)composite is the key cladding material of nuclear fuel,which determines the safety and reliability of nuclear fuel storage and transportation.The replacement of its storage and transportation scenario needs to be completed by the manipulator,but the application of SiCf/SiC wear,fracture,and nuclear leakage in the snatching process of brittle-flexible-rigid contact in the irradiation environment has been seriously restricted due to unclear understanding of the damage mechanism.Therefore,the effects of irradiation dose and clamping load on the friction characteristics of the contact interface between SiCf/SiC clad tube are studied in this paper,and the effects of irradiation parameters and clamping force on the static friction coefficient of the contact interface between the clad tube and flexible nitrile are obtained.Based on the Greenwood-Williamson tribological model,a numerical model of the shape and structure of the contact micro-convex at the micro-scale of the clamping interface is constructed by introducing the multi-surface integral,and finally verified by experiments.The research results show that there is a unique"irradiation suppression zone"under the clamping condition of SiCf/SiC cladding tube under the nuclear irradiation environment,and the growth of static friction coefficient slows down until stagnates after irradiation reaches a certain extent(600 kGy),and there will be a decline when the irradiation dose continues to increase,among which the clamping force of 15.2 N within the irradiation interval of 1,000 kGy can meet the safety of nuclear environment operation.The results of this paper can provide an important theoretical basis and application guidance for the safe operation of SiCf/SiC cladding tubes in the storage and transportation clamping process.
查看更多>>摘要：The formation of tribolayers may play significant influences on fretting wear.At elevated temperature,the adhesion among wear debris and the increased diffusion rate facilitate the formation of tribolayers.However,the intensification of oxidation at elevated temperature and the low diffusion rate in oxides may play an adverse role.The present study aims to investigate the role of temperature in tribolayers in fretting wear using a γ-TiAl alloy.Scanning electron microscope,energy dispersive spectrometer,Raman spectrometer,transmission electron microscope and nanoindentation were utilized to investigate the wear debris,tribolayers,and wear scars.The fretting tests showed that,compared with that at room temperature(RT)and 350 ℃,significant reduction in wear rate and decrease in the fluctuation of friction coefficient occurred at 550 and 750 ℃.It was further revealed that when temperature raised from room temperature(RT)to 750 ℃,the oxidation of the wear debris increased slightly and the diffusion coefficients increased prominently,which facilities the formation of well tribo-sintered tribolayers.The well tribo-sintered tribolayers presented homogenous structure,nanocrystalline grains with excellent mechanical properties,and resulted in the improvement in the fretting wear resistance of the γ-TiAl alloy at 550 and 750 ℃.
查看更多>>摘要：Lyotropic liquid crystals have lubricating properties due to their ordered assembly and fluidity,whose mesogens are often characterized by amphiphilic properties.Despite the attention that graphene oxide(GO)has been studied as a novel amphiphilic lyotropic mesogen this decade,and GO applied as a lubrication additive has been demonstrated in both oil and water-based systems,little research reveals the interfacial lubrication of GO liquid crystals yet.This work reports that GO aqueous dispersion can form lyotropic liquid crystals above a specific critical concentration of 5.00 mg/mL,providing a form of stable water-based lubricant,which can keep stable for several months and can reduce friction by 37.3%and wear by 25.24%.The liquid crystal phase was verified by polarizing microscope and synchrotron radiation small-angle X-ray scattering,and its rheological properties and viscoelasticity were studied by interfacial rheometer.The formation of lyotropic liquid crystals can enhance the stability of GO aqueous dispersions at high density,simultaneously ensuring friction decrease and anti-wear effect.It is attributed to the stable nematic network by the ordered GO sheets.The ordered assembly structure bears vertical shear force,therefore,reducing the wear.It is also assumed that the wide lateral size of graphene oxide promotes the nematic phase thus smoothes the graphene oxide film composed spontaneously under the coincidence of lamellar liquid crystal and 2D layered material.Through this work,the interlayer lubrication of GO was optimized,and the problem of GO dispersion sedimentation was solved by self-assembly.The range of interfacial lubrication of GO aqueous dispersion has been expanded and the synergistic effect is conducive to the environmentally friendly lubricants.
查看更多>>摘要：Artificial biomaterials with dynamic mechano-responsive behaviors similar to those of biological tissues have been drawing great attention.In this study,we report a TiO2-based nanowire(TiO2NWs)scaffolds,which exhibit dynamic mechano-responsive behaviors varying with the number and amplitude of nano-deformation cycles.It is found that the elastic and adhesive forces in the TiO2NWs scaffolds can increase significantly after multiple cycles of nano-deformation.Further nanofriction experiments show the triboelectric effect of increasing elastic and adhesive forces during the nano-deformation cycles of TiO2NWs scaffolds.These properties allow the TiO2NW scaffolds to be designed and applied as intelligent artificial biomaterials to simulate biological tissues in the future.
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