Magnesium silicate hydroxides(MSHs)with granular,schistose,and tubular morphologies were separately incorporated to enhance the tribological properties of phosphate/MoS2 composite coatings.The nano-schistose MSH demon...Magnesium silicate hydroxides(MSHs)with granular,schistose,and tubular morphologies were separately incorporated to enhance the tribological properties of phosphate/MoS2 composite coatings.The nano-schistose MSH demonstrated superior tribological performance due to its effective interactions with the worn surface and frictional synergies with solid lubricants.Incorporation of nano-schistose MSH decreased the friction coefficient of composite coatings by about 34.7%and increased the anti-wear performance of composite coatings by about thirteen times.Nano-schistose MSH facilitated the formation of a friction-induced multi-layer heterogenous slipping structure with layered solid lubricants at the friction interface.Moreover,tribo-chemical reactions between nano-schistose MSH and worn surface promoted the in-situ formation of a cermet supporting film,and this also induced the gradual in-situ formation of a lubrication film on the top of worn surface.Consequently,the contact state between tribo-pairs was timely regulated and the invalidation of the nanocomposite slipping structure was effectively restrained during the friction process.As a result,the service life of the phosphate composite coatings was significantly extended and further abrasion on the worn surface was notably reduced.展开更多
This study demonstrates that magnetron-sputtered NbSe_(2)film can be used as a lubricant for space current-carrying sliding contact,which accommodates both metal-like conductivity and MoS_(2)-like lubricity.Deposition...This study demonstrates that magnetron-sputtered NbSe_(2)film can be used as a lubricant for space current-carrying sliding contact,which accommodates both metal-like conductivity and MoS_(2)-like lubricity.Deposition at low pressure and low energy is performed to avoid the generation of the interference phase of NbSe_(3).The composition,microstructure,and properties of the NbSe_(2)films are further tailored by controlling the sputtering current.At an appropriate current,the film changed from amorphous to crystalline,maintained a dense structure,and exhibited excellent comprehensive properties.Compared to the currently available electrical contact lubricating materials,the NbSe_(2)film exhibits a significant advantage under the combined vacuum and current-carrying conditions.The friction coefficient decreases from 0.25 to 0.02,the wear life increases more than seven times,and the electric noise reduces approximately 50%.展开更多
High-entropy oxides(HEOs)are widely researched as potential materials for thermal barrier coatings(TBCs).However,the relatively low thermal expansion coefficient(TEC)of those materials severely restricts their practic...High-entropy oxides(HEOs)are widely researched as potential materials for thermal barrier coatings(TBCs).However,the relatively low thermal expansion coefficient(TEC)of those materials severely restricts their practical application.In order to improve the poor thermal expansion property and further reduce the thermal conductivity,high-entropy(La_(0.2)Nd_(0.2)Sm_(0.2)Eu_(0.2)Gd_(0.2))_(2)Ce_(2)O_(7) is designed and synthesized in this work.The as-prepared multicomponent material is formed in a simple disordered fluorite structure due to the high-entropy stabilization effect.Notably,it exhibits a much higher TEC of approximately 12.0×10^(−6) K^(−1) compared with those of other high-entropy oxides reported in the field of TBCs.Besides,it presents prominent thermal insulation behavior with a low intrinsic thermal conductivity of 0.92 W·m^(−1)·K^(−1) at 1400℃,which can be explained by the existence of high concentration oxygen vacancies and highly disordered arrangement of multicomponent cations in the unique high-entropy configuration.Through high-temperature in-situ X-ray diffraction(XRD)measurement,this material shows excellent phase stability up to 1400℃.Benefiting from the solid solution strengthening effect,it shows a higher hardness of 8.72 GPa than the corresponding single component compounds.The superior thermo-physical performance above enables(La_(0.2)Nd_(0.2)Sm_(0.2)Eu_(0.2)Gd_(0.2))_(2)Ce_(2)O_(7) a promising TBC material.展开更多
The investigate about the effect of the microstructure of Ti6Al4V alloy on its cavitation erosion and corrosion properties in marine can provide the key basis for the application.On the basis of as-received Ti6Al4V(TC...The investigate about the effect of the microstructure of Ti6Al4V alloy on its cavitation erosion and corrosion properties in marine can provide the key basis for the application.On the basis of as-received Ti6Al4V(TC4)alloy,FC-TC4 and AC-TC4 alloys were prepared by heat treatment with the cooling method of a furnace and atmospheric environment,respectively.Then the microstructure evolutions of three samples were scrutinized and the effect of microstructure on their cavitation erosion and corrosion resistance was explored.The results showed that more recrystallized grains formed as well as its content of α grains and high-angle grain boundaries increased in AC-TC4 alloy.To FC-TC4 alloy,there was obvious grain growth apart from recrystallization.Moreover,many nanotwins of Ti V and Ti Al_(3)were formed separately in FC-TC4 and AC-TC4 alloys due to the dislocation migration during heat treatment.The microstructure evolution led the hardness and elastic modulus of AC-TC4 alloy were the best,followed by FC-TC4 alloy,that of TC4 were the worst.Similarly,passivating ability of AC-TC4 alloy was the best among three samples because of its microstructure.Although cracks extended along the grain boundaries under the action of continual cavitation erosion,the passivation film formed by TiO_(2) and Al_(2)O_(3) would enhance their resistance to further corrosion and cavitation erosion in artificial seawater.展开更多
The mechanical parts serving in the marine environment are up against the dual damage of corrosion and cavitation erosion,so the Ni Co Cr Al YTa coating with excellent corrosion resistance is successfully prepared by ...The mechanical parts serving in the marine environment are up against the dual damage of corrosion and cavitation erosion,so the Ni Co Cr Al YTa coating with excellent corrosion resistance is successfully prepared by high velocity oxy-fuel(HVOF)sprayed technology to protect the equipment from deterioration.The chemical composition and mechanical properties as well as the microstructure evolution of the coating before and after annealing treatment are studied.At the same time,the influence of annealing treatment on the corrosion and cavitation erosion behaviors of the coating is investigated,as well.The NiCoCrAlYTa coating mainly containsγ-Ni,β-Ni Al,andγ’-Ni3Al phases.During the deposition,the microcrystals or incomplete crystals generate in the interior of the coating because of the large temperature difference and impact force.Meanwhile,there is twin crystal structure in the as-spayed coating.After annealing treatment,the growth of grains and the segregation of reactive elements improve interface strength and inhibit the formation of micro-defects in the coating.The annealing temperature is of significance to the microstructure,mechanical properties,anti-corrosion and cavitation erosion resistance of the coating.This study provides a combined approach toward improving the corrosion and cavitation erosion resistance of NiCoCrAlYTa coatings.展开更多
Recent studies have reported that adding nanoparticles to graphene enables macroscale superlubricity to be achieved.This study focuses on the role of nanoparticles in achieving superlubricity.First,because graphene na...Recent studies have reported that adding nanoparticles to graphene enables macroscale superlubricity to be achieved.This study focuses on the role of nanoparticles in achieving superlubricity.First,because graphene nanoscrolls can be formed with nanoparticles as seeds under shear force,the applied load(or shear force)is adjusted to manipulate the formation of graphene nanoscrolls and to reveal the relationship between graphene-nanoscroll formation and superlubricating performance.Second,the load-carrying role of spherical nano-SiO_(2)particles during the friction process is verified by comparison with an elaborately designed fullerene that possesses a hollow-structured graphene nanoscroll.Results indicate that the incorporated nano-SiO_(2)particles have two roles in promoting the formation of graphene nanoscrolls and exhibiting load-carrying capacity to support macroscale forces for achieving macroscale superlubricity.Finally,macroscale superlubricity(friction coefficient:0.006–0.008)can be achieved under a properly tuned applied load(2.0 N)using a simple material system in which a graphene/nano-SiO_(2)particle composite coating slides against a steel counterpart ball without a decorated diamond-like carbon film.The approach described in this study could be of significance in engineering.展开更多
The in-situ formation of oxides on alloy surface induced by high temperature can effectively reduce wear and resist oxidation.In consideration of the solid solution strengthening effect and great oxidation resistance ...The in-situ formation of oxides on alloy surface induced by high temperature can effectively reduce wear and resist oxidation.In consideration of the solid solution strengthening effect and great oxidation resistance of additional elements at elevated temperature,the NiCrWMoCuCBFe coating was prepared by high velocity oxygen flame(HVOF)spraying technology,and its tribological behavior was scrutinized from 25 to 800°C.By means of high temperature Vickers hardness tester and high temperature X-ray diffractometer,the mechanical properties and microstructures of NiCrWMoCuCBFe coating were measured.And the effect of the mechanical properties and microstructures of the coating on tribological performance was discussed in detail.The results showed both its friction coefficient(0.37)and wear rate(5.067×10^(−6)mm^(3)·N^(−1)·m^(−1))at 800℃ were the lowest,which was mainly related to the formation of“glaze”layer on the coating surface at high temperature.The glaze layer consisted of two parts,which were NiCr_(2)O_(4)oxide film with the ability of interlaminar slip formed in the outer layer and nano-grains existed in the inner layer.Worth mentioning,these nano-grains provided bearing capability while the oxide film was vital to reduce wear rate and friction coefficient.As the ambient temperature increased,many hard oxides were produced on the wear scars,including NiO,Cr_(2)O_(3),MoO_(3),and Mo_(2)C.They can improve tribological and mechanical properties of NiCrWMoCuCBFe coating at a wide temperature range.展开更多
Cu-Ni bimetallic nanoparticles surface-capped with dodecanethiol were prepared via the controlled reduction of nickel nitrate and copper nitrate in the presence of dodecanethiol as ligand and hydrazine hydrate as redu...Cu-Ni bimetallic nanoparticles surface-capped with dodecanethiol were prepared via the controlled reduction of nickel nitrate and copper nitrate in the presence of dodecanethiol as ligand and hydrazine hydrate as reductant. The morphology and structure of the Cu-Ni nanoparticles were analyzed by trans- mission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, Fourier transform infrared spectrometry, and thermal gravimetric analysis. Furthermore, the tribological properties of the Cu-Ni nanoparticles as a lubricant additive in liquid paraffin were evaluated with a four-ball machine, and the morphology and elemental composition of the worn surfaces were analyzed by three-dimensional non-contact surface profilometry and X-ray photoelectron spectroscopy, respectively, The results indi- cated that Cu-Ni nanoparticles prepared at a sufficient dodecanethiol concentration showed almost no signs of aggregation, and exhibited good dispersibility in various apolar solvents. The addition of the Cu-Ni nanoparticles improved the load-carrying capacity as well as friction-reducing and anti-wear abilities of liquid paraffin, attributed to the roiling effect of agglomerated Cu-Ni nanocores released by the Cu-Ni nanoparticles during sliding, and the formation of a boundary lubricating film containing tribochemical reaction products such as iron oxides and iron sulfate.展开更多
基金Financial assistances of the National Key R&D Program of China(No.2022YFB3809000)the National Natural Science Foundation of China(No.52105228)the Defense Industrial Technology Development Program(No.JCKY2021130B038)were greatly appreciated.
文摘Magnesium silicate hydroxides(MSHs)with granular,schistose,and tubular morphologies were separately incorporated to enhance the tribological properties of phosphate/MoS2 composite coatings.The nano-schistose MSH demonstrated superior tribological performance due to its effective interactions with the worn surface and frictional synergies with solid lubricants.Incorporation of nano-schistose MSH decreased the friction coefficient of composite coatings by about 34.7%and increased the anti-wear performance of composite coatings by about thirteen times.Nano-schistose MSH facilitated the formation of a friction-induced multi-layer heterogenous slipping structure with layered solid lubricants at the friction interface.Moreover,tribo-chemical reactions between nano-schistose MSH and worn surface promoted the in-situ formation of a cermet supporting film,and this also induced the gradual in-situ formation of a lubrication film on the top of worn surface.Consequently,the contact state between tribo-pairs was timely regulated and the invalidation of the nanocomposite slipping structure was effectively restrained during the friction process.As a result,the service life of the phosphate composite coatings was significantly extended and further abrasion on the worn surface was notably reduced.
基金The authors are grateful to the National Natural Science Foundation of China(Grant No.51775537)Youth Innovation Promotion Association of Chinese Academy of Sciences(Grant No.Y202084)for financial support.
文摘This study demonstrates that magnetron-sputtered NbSe_(2)film can be used as a lubricant for space current-carrying sliding contact,which accommodates both metal-like conductivity and MoS_(2)-like lubricity.Deposition at low pressure and low energy is performed to avoid the generation of the interference phase of NbSe_(3).The composition,microstructure,and properties of the NbSe_(2)films are further tailored by controlling the sputtering current.At an appropriate current,the film changed from amorphous to crystalline,maintained a dense structure,and exhibited excellent comprehensive properties.Compared to the currently available electrical contact lubricating materials,the NbSe_(2)film exhibits a significant advantage under the combined vacuum and current-carrying conditions.The friction coefficient decreases from 0.25 to 0.02,the wear life increases more than seven times,and the electric noise reduces approximately 50%.
基金This research was financially supported by Youth Innovation Promotion Association(No.2014378)for Chinese Academy of Sciences.The authors are grateful to the constructive comments of the reviewers.
文摘High-entropy oxides(HEOs)are widely researched as potential materials for thermal barrier coatings(TBCs).However,the relatively low thermal expansion coefficient(TEC)of those materials severely restricts their practical application.In order to improve the poor thermal expansion property and further reduce the thermal conductivity,high-entropy(La_(0.2)Nd_(0.2)Sm_(0.2)Eu_(0.2)Gd_(0.2))_(2)Ce_(2)O_(7) is designed and synthesized in this work.The as-prepared multicomponent material is formed in a simple disordered fluorite structure due to the high-entropy stabilization effect.Notably,it exhibits a much higher TEC of approximately 12.0×10^(−6) K^(−1) compared with those of other high-entropy oxides reported in the field of TBCs.Besides,it presents prominent thermal insulation behavior with a low intrinsic thermal conductivity of 0.92 W·m^(−1)·K^(−1) at 1400℃,which can be explained by the existence of high concentration oxygen vacancies and highly disordered arrangement of multicomponent cations in the unique high-entropy configuration.Through high-temperature in-situ X-ray diffraction(XRD)measurement,this material shows excellent phase stability up to 1400℃.Benefiting from the solid solution strengthening effect,it shows a higher hardness of 8.72 GPa than the corresponding single component compounds.The superior thermo-physical performance above enables(La_(0.2)Nd_(0.2)Sm_(0.2)Eu_(0.2)Gd_(0.2))_(2)Ce_(2)O_(7) a promising TBC material.
基金financially supported by the Youth Innovation Promotion Association(No.2014378)for Chinese Academy of Sciences。
文摘The investigate about the effect of the microstructure of Ti6Al4V alloy on its cavitation erosion and corrosion properties in marine can provide the key basis for the application.On the basis of as-received Ti6Al4V(TC4)alloy,FC-TC4 and AC-TC4 alloys were prepared by heat treatment with the cooling method of a furnace and atmospheric environment,respectively.Then the microstructure evolutions of three samples were scrutinized and the effect of microstructure on their cavitation erosion and corrosion resistance was explored.The results showed that more recrystallized grains formed as well as its content of α grains and high-angle grain boundaries increased in AC-TC4 alloy.To FC-TC4 alloy,there was obvious grain growth apart from recrystallization.Moreover,many nanotwins of Ti V and Ti Al_(3)were formed separately in FC-TC4 and AC-TC4 alloys due to the dislocation migration during heat treatment.The microstructure evolution led the hardness and elastic modulus of AC-TC4 alloy were the best,followed by FC-TC4 alloy,that of TC4 were the worst.Similarly,passivating ability of AC-TC4 alloy was the best among three samples because of its microstructure.Although cracks extended along the grain boundaries under the action of continual cavitation erosion,the passivation film formed by TiO_(2) and Al_(2)O_(3) would enhance their resistance to further corrosion and cavitation erosion in artificial seawater.
基金finically supported by the Youth Innovation Promotion Association(No.2014378)for Chinese Academy of Sciences and Sciencethe National Natural Science Foundation of China(No.51771214)。
文摘The mechanical parts serving in the marine environment are up against the dual damage of corrosion and cavitation erosion,so the Ni Co Cr Al YTa coating with excellent corrosion resistance is successfully prepared by high velocity oxy-fuel(HVOF)sprayed technology to protect the equipment from deterioration.The chemical composition and mechanical properties as well as the microstructure evolution of the coating before and after annealing treatment are studied.At the same time,the influence of annealing treatment on the corrosion and cavitation erosion behaviors of the coating is investigated,as well.The NiCoCrAlYTa coating mainly containsγ-Ni,β-Ni Al,andγ’-Ni3Al phases.During the deposition,the microcrystals or incomplete crystals generate in the interior of the coating because of the large temperature difference and impact force.Meanwhile,there is twin crystal structure in the as-spayed coating.After annealing treatment,the growth of grains and the segregation of reactive elements improve interface strength and inhibit the formation of micro-defects in the coating.The annealing temperature is of significance to the microstructure,mechanical properties,anti-corrosion and cavitation erosion resistance of the coating.This study provides a combined approach toward improving the corrosion and cavitation erosion resistance of NiCoCrAlYTa coatings.
基金The authors thank the National Natural Science Foundation of China(Grant No.51775537)Youth Innovation Promotion Association of Chinese Academy of Sciences(Grant No.Y202084)for financial support.
文摘Recent studies have reported that adding nanoparticles to graphene enables macroscale superlubricity to be achieved.This study focuses on the role of nanoparticles in achieving superlubricity.First,because graphene nanoscrolls can be formed with nanoparticles as seeds under shear force,the applied load(or shear force)is adjusted to manipulate the formation of graphene nanoscrolls and to reveal the relationship between graphene-nanoscroll formation and superlubricating performance.Second,the load-carrying role of spherical nano-SiO_(2)particles during the friction process is verified by comparison with an elaborately designed fullerene that possesses a hollow-structured graphene nanoscroll.Results indicate that the incorporated nano-SiO_(2)particles have two roles in promoting the formation of graphene nanoscrolls and exhibiting load-carrying capacity to support macroscale forces for achieving macroscale superlubricity.Finally,macroscale superlubricity(friction coefficient:0.006–0.008)can be achieved under a properly tuned applied load(2.0 N)using a simple material system in which a graphene/nano-SiO_(2)particle composite coating slides against a steel counterpart ball without a decorated diamond-like carbon film.The approach described in this study could be of significance in engineering.
基金This work was supported by the National Natural Science Foundation of China(No.51771214)the Youth Innovation Promotion Association of Chinese Academy of Sciences(No.2014378).
文摘The in-situ formation of oxides on alloy surface induced by high temperature can effectively reduce wear and resist oxidation.In consideration of the solid solution strengthening effect and great oxidation resistance of additional elements at elevated temperature,the NiCrWMoCuCBFe coating was prepared by high velocity oxygen flame(HVOF)spraying technology,and its tribological behavior was scrutinized from 25 to 800°C.By means of high temperature Vickers hardness tester and high temperature X-ray diffractometer,the mechanical properties and microstructures of NiCrWMoCuCBFe coating were measured.And the effect of the mechanical properties and microstructures of the coating on tribological performance was discussed in detail.The results showed both its friction coefficient(0.37)and wear rate(5.067×10^(−6)mm^(3)·N^(−1)·m^(−1))at 800℃ were the lowest,which was mainly related to the formation of“glaze”layer on the coating surface at high temperature.The glaze layer consisted of two parts,which were NiCr_(2)O_(4)oxide film with the ability of interlaminar slip formed in the outer layer and nano-grains existed in the inner layer.Worth mentioning,these nano-grains provided bearing capability while the oxide film was vital to reduce wear rate and friction coefficient.As the ambient temperature increased,many hard oxides were produced on the wear scars,including NiO,Cr_(2)O_(3),MoO_(3),and Mo_(2)C.They can improve tribological and mechanical properties of NiCrWMoCuCBFe coating at a wide temperature range.
文摘Cu-Ni bimetallic nanoparticles surface-capped with dodecanethiol were prepared via the controlled reduction of nickel nitrate and copper nitrate in the presence of dodecanethiol as ligand and hydrazine hydrate as reductant. The morphology and structure of the Cu-Ni nanoparticles were analyzed by trans- mission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, Fourier transform infrared spectrometry, and thermal gravimetric analysis. Furthermore, the tribological properties of the Cu-Ni nanoparticles as a lubricant additive in liquid paraffin were evaluated with a four-ball machine, and the morphology and elemental composition of the worn surfaces were analyzed by three-dimensional non-contact surface profilometry and X-ray photoelectron spectroscopy, respectively, The results indi- cated that Cu-Ni nanoparticles prepared at a sufficient dodecanethiol concentration showed almost no signs of aggregation, and exhibited good dispersibility in various apolar solvents. The addition of the Cu-Ni nanoparticles improved the load-carrying capacity as well as friction-reducing and anti-wear abilities of liquid paraffin, attributed to the roiling effect of agglomerated Cu-Ni nanocores released by the Cu-Ni nanoparticles during sliding, and the formation of a boundary lubricating film containing tribochemical reaction products such as iron oxides and iron sulfate.
