To study the atmospheric aging of acrylic coatings,a two-year aging exposure experiment was conducted in 13 representative climatic environments in China.An atmospheric aging evaluation model of acrylic coatings was d...To study the atmospheric aging of acrylic coatings,a two-year aging exposure experiment was conducted in 13 representative climatic environments in China.An atmospheric aging evaluation model of acrylic coatings was developed based on aging data including11 environmental factors from 567 cities.A hybrid method of random forest and Spearman correlation analysis was used to reduce the redundancy and multicollinearity of the data set by dimensionality reduction.A semi-supervised collaborative trained regression model was developed with the environmental factors as input and the low-frequency impedance modulus values of the electrochemical impedance spectra of acrylic coatings in 3.5wt%NaCl solution as output.The model improves accuracy compared to supervised learning algorithms model(support vector machines model).The model provides a new method for the rapid evaluation of the aging performance of acrylic coatings,and may also serve as a reference to evaluate the aging performance of other organic coatings.展开更多
The safety and reliability of weapon systems would be significantly affected by changes in the performance of energetic materials due to ambient temperature and humidity.Nanothermites have promising applications due t...The safety and reliability of weapon systems would be significantly affected by changes in the performance of energetic materials due to ambient temperature and humidity.Nanothermites have promising applications due to their excellent reactivity.Therefore it becomes extremely important to understand their aging and failure process in the environment before using them.Here,the aging and failure process of Al/CuO in 71°C/60%RH were investigated,and showed that CuO nanoparticles negatively catalyze Al nanopowders,resulting in rapid hydration.The anti-aging effect of FAS-17-coated Al nanopowder was also examined.The aging process of Al,Al/CuO,and Al@FAS-17/CuO in high humidity and heat environment were revealed by quasi-in situ SEM and TEM methods.Compared with the aging of pure Al,the Al nanopowder in the nanothermites strongly agglomerated with the CuO nanopowder and hydrated earlier.This may be caused by CuO catalyzed hydration of Al nanopowder.The energy release experiments showed that the performance of Al/CuO decreased rapidly and failed to ignite after 4 h of aging.In contrast,the Al@FAS-17/CuO thermite can achieve long-term stability of up to 60 h in the same environment by simple cladding of FAS-17.It is found that FAS-17 coated Al nanopowder can prevent both particle agglomeration and water erosion,which is an effective means to make nanothermites application in high humidity and heat environment.展开更多
The multilayer gradient CrN/ZrN coatings were synthesized by a dual cathode DC magnetron sputtering.The influence of different species of reaction gases and partial pressures on structure and mechanical properties was...The multilayer gradient CrN/ZrN coatings were synthesized by a dual cathode DC magnetron sputtering.The influence of different species of reaction gases and partial pressures on structure and mechanical properties was investigated using XRD, AES, XPS, and nanoindentation. The results show that N2-NH3 mixture process gas is of benefit to the synthesis of superhard multilayered gradient CrN/ZrN coatings. The presence of the preferred orientations of CrN(111), (200) and ZrN (111), (220) in the structure is a main reason for superhardness of multilayered gradient coatings.展开更多
A Cr/Cr2N/CrN multilayer coating with a thickness of 24.4 μm was deposited by multi-arc ion plating. The coating was systematically characterized by field emission scanning electron microscopy(FESEM), X-ray photoelec...A Cr/Cr2N/CrN multilayer coating with a thickness of 24.4 μm was deposited by multi-arc ion plating. The coating was systematically characterized by field emission scanning electron microscopy(FESEM), X-ray photoelectron spectrometry(XPS), energy dispersive spectroscopy(EDS), X-ray diffraction(XRD) and transmission electron microscopy(TEM). Hardness and adhesion were tested by nanoindentation and scratch tester, respectively. The friction properties were investigated by a reciprocating UMT-3MT ball-on-disk tribometer in air and seawater. The results showed that the multilayer coating consisted of three different layers, with Cr,Cr2N and CrN phases, respectively. Compared with CrN single layer coating, the adhesion of the multilayer coating was improved significantly, the hardness of the multilayer coating was(21±2) GPa. The corrosion resistance of the multilayer coating was also improved in artificial seawater. The friction coefficient of multilayer coating was lower than that of CrN single layer coating both in air and seawater.展开更多
Cr/CrN multilayer coatings with bilayer periods in the range from 1351 to 260 nm were prepared on 304 stainless steel substrates by arc ion plating to study the microstructure and properties of multilayer coatings and...Cr/CrN multilayer coatings with bilayer periods in the range from 1351 to 260 nm were prepared on 304 stainless steel substrates by arc ion plating to study the microstructure and properties of multilayer coatings and stimulate their application.SEM results confirm the clear periodicity of the Cr/CrN multilayer coatings and the clear interface between individual layers.XRD patterns reveal that these multilayer coatings contain Cr,CrN and Cr_2N phases.Because Cr layer is softer than its nitride layer,the hardness decreases with the shortening of the bilayer period(or increasing volume fraction of Cr layer).The Cr/CrN multilayer coating with 862 nm period possesses the highest indentation toughness due to a proper individual Cr and nitride layer thickness.However,for the Cr/CrN multilayer with the bilayer period of 1351 nm,it possesses the lowest toughness due to more nitride phase.The indentation toughness of Cr/CrN multilayer coatings is related with their bilayer period.A coating with a proper individual Cr and nitride layer thickness possesses the highest indentation toughness.展开更多
With advantages of high specific strength, low elastic module, good damping property et al., the magnesium alloys exhibit great potential applications in aerospace. But poor wear behavior results in limited use of mag...With advantages of high specific strength, low elastic module, good damping property et al., the magnesium alloys exhibit great potential applications in aerospace. But poor wear behavior results in limited use of magnesium alloy to static components. In this study, a 2 μm thick coating with 12 sub-layers of CrN and TiN is deposited alternately on the surface of magnesium alloy AZ91 by a novel method of arc-glow plasma depositing to improve its wear resistance. The composition and microstructure of the coating layer are analyzed by means of SEM, XRD and GDS. The friction coefficient is measured by ball on disc rubbing test, and the wear rates are also calculated. The results indicate that the friction coefficient is increased, but the wear rate is dropped sharply as compared with bare metal. The surface hardness is about HK0.01 1400.展开更多
The heterogeneous multilayer interface of VN/Ag coatings and transition multilayer interface of VN/Ag coatings were prepared on Inconel 781 and Si(100),and the microstructures,mechanical and tribological properties we...The heterogeneous multilayer interface of VN/Ag coatings and transition multilayer interface of VN/Ag coatings were prepared on Inconel 781 and Si(100),and the microstructures,mechanical and tribological properties were investigated from 25 to 700℃.The results showed that the surface roughness and average grain size of VN/Ag coatings with transition multilayer interface are obviously larger than those of VN/Ag coatings with heterogeneous multilayer interface.The coatings with transition multilayer interface have higher adhesion force and hardness than the coatings with heterogeneous multilayer interface,and both coatings can effectively restrict the initiation and propagation of microcracks.Both coatings have excellent self-adaptive lubricating properties with a decrease of friction coefficient as the temperature increases,but their wear rates reveal a drastic increase.The phase composition of the worn area of both coatings was investigated,which indicates that a smooth Ag,Magnéli phase(V2O5)and bimetallic oxides(Ag3VO4 and AgVO3)can be responsible to the excellent lubricity of both coatings.To sum up,the coatings with transition multilayer interface have excellent adaptive lubricating properties and can properly control the diffusion rate and release rate of the lubricating phase,indicating that they have great potential in solving the problem of friction and wear of mechanical parts.展开更多
In order to predict the storage life of a certain type of HTPB(hydroyl-terminated polybutadiene)coating at 25℃ and analyze the influence of pre-strain on the storage life,the accelerated aging tests of HTPB coating a...In order to predict the storage life of a certain type of HTPB(hydroyl-terminated polybutadiene)coating at 25℃ and analyze the influence of pre-strain on the storage life,the accelerated aging tests of HTPB coating at 40℃,50℃,60℃,70℃ with the pre-strain of 0%,3%,6%,9%,respectively were carried out.The variation regularity of the change of crosslinking density was analyzed and the aging model of HTPB coating under pre-strained thermally-accelerated aging was proposed.The storage life of HTPB coating at 25℃ was estimated by using the Berthelot equation as the end point of the aging life with a 30% decrease in maximum elongation.The results showed that the change of crosslinking density of HTPB coating increased with the increase of aging temperature and aging time,and decreased with the increase of pre-strain.Under 0% prestrain,the relationship between the change of crosslinking density of HTPB coating and the aging time can be described by the logarithmic model with the confidence probability greater than 99%.The stress relaxation phenomenon existed under 3%,6%and 9%pre-strained aging.The aging model considering chemical aging and pre-strain was established with the confidence probability greater than 90%.The storage life of HTPB coating was 15.2935 years at 25C under 0% prestrain,which was reduced by 13.9007%,75.6949% and 89.7859% under 3%,6% and 9% pre-strain,respectively.The existence of pre-strain has a serious impact on the storage life of HTPB coating,therefore,the pre-strain should be avoided as much as possible during the actual storage.展开更多
TiN/CrN multilayered hard coatings with TiCrN interlayer were deposited onhigh speed steel substrates by using a filtered cathodic vacuum arc technique. The structure andcomposition of the coatings were characterized ...TiN/CrN multilayered hard coatings with TiCrN interlayer were deposited onhigh speed steel substrates by using a filtered cathodic vacuum arc technique. The structure andcomposition of the coatings were characterized by scanning electron microscopy (SEM) and Augerelectron spectroscopy (AES). A high adhesion of up to 80 N was demonstrated by scratching tests forthe multi-layered coatings. Nanoindentation tests were performed to determine the hardness andelastic modulus of the coatings as a function of the multiplayer modulation period. It was observedthat the hardness of the multilayered coatings is higher than those of either TiN or CrN singlecoatings, and it increases with decreasing modulation periods, which is consistent with predictionsfrom the Hall-Petch type strengthening mechanism, though at small modulation periods, deviation fromthe Hall-Petch relation has been observed for the multilayered coatings. The life-span of drillscoated with TiN/CrN multilayered is triple as long as that coated with TiN layer.展开更多
Fracture behavior of CrN coatings deposited on the surface of silicon and AISI52100 steel by different energy ion beam assisted magnetron sputtering technique （IBAMS） was studied using indentation and dynamic cycle ...Fracture behavior of CrN coatings deposited on the surface of silicon and AISI52100 steel by different energy ion beam assisted magnetron sputtering technique （IBAMS） was studied using indentation and dynamic cycle impact. It is found that, for the coatings on silicon substrate, the cracks form in the indentation corners and then propagate outward under Vickers indentation. The coating prepared using ion assisted energy of 800 eV shows the highest fracture resistance due to its compact structure. Under Rockwell indentation, only finer radial cracks are found in the CrN coating on AISI 52100 steel without ion assisting while in the condition of ion assisting energy of 800 eV, radial, lateral cracks and spalling appear in the vicinity of indentation. The fracture of CrN coatings under dynamic cycle impact is similar to fatigue. The impact fracture resistance of CrN coatings increases with the increase of ion assisting energy.展开更多
基金the National Key R&D Program of China(2023YFB3812901)the Postdoctoral Fellowship Program of CPSF(No.GZC20230239)+1 种基金the China Postdoctoral Science Foundation(No.2023M740219)the National Natural Science Foundation of China(No.22209094)。
文摘To study the atmospheric aging of acrylic coatings,a two-year aging exposure experiment was conducted in 13 representative climatic environments in China.An atmospheric aging evaluation model of acrylic coatings was developed based on aging data including11 environmental factors from 567 cities.A hybrid method of random forest and Spearman correlation analysis was used to reduce the redundancy and multicollinearity of the data set by dimensionality reduction.A semi-supervised collaborative trained regression model was developed with the environmental factors as input and the low-frequency impedance modulus values of the electrochemical impedance spectra of acrylic coatings in 3.5wt%NaCl solution as output.The model improves accuracy compared to supervised learning algorithms model(support vector machines model).The model provides a new method for the rapid evaluation of the aging performance of acrylic coatings,and may also serve as a reference to evaluate the aging performance of other organic coatings.
基金supported by the National Natural Science Foundation of China(Grant No.22275092)。
文摘The safety and reliability of weapon systems would be significantly affected by changes in the performance of energetic materials due to ambient temperature and humidity.Nanothermites have promising applications due to their excellent reactivity.Therefore it becomes extremely important to understand their aging and failure process in the environment before using them.Here,the aging and failure process of Al/CuO in 71°C/60%RH were investigated,and showed that CuO nanoparticles negatively catalyze Al nanopowders,resulting in rapid hydration.The anti-aging effect of FAS-17-coated Al nanopowder was also examined.The aging process of Al,Al/CuO,and Al@FAS-17/CuO in high humidity and heat environment were revealed by quasi-in situ SEM and TEM methods.Compared with the aging of pure Al,the Al nanopowder in the nanothermites strongly agglomerated with the CuO nanopowder and hydrated earlier.This may be caused by CuO catalyzed hydration of Al nanopowder.The energy release experiments showed that the performance of Al/CuO decreased rapidly and failed to ignite after 4 h of aging.In contrast,the Al@FAS-17/CuO thermite can achieve long-term stability of up to 60 h in the same environment by simple cladding of FAS-17.It is found that FAS-17 coated Al nanopowder can prevent both particle agglomeration and water erosion,which is an effective means to make nanothermites application in high humidity and heat environment.
基金Project(043801011) supported by Applied Basic Key Project of Tianjin Project(50472026) supported by the National Natural Science Foundation of China Project(GJDF01) also supported partly by Joint Project of Tianjin Municipal University and Nankai University and Tianjin University, State Education Ministry
文摘The multilayer gradient CrN/ZrN coatings were synthesized by a dual cathode DC magnetron sputtering.The influence of different species of reaction gases and partial pressures on structure and mechanical properties was investigated using XRD, AES, XPS, and nanoindentation. The results show that N2-NH3 mixture process gas is of benefit to the synthesis of superhard multilayered gradient CrN/ZrN coatings. The presence of the preferred orientations of CrN(111), (200) and ZrN (111), (220) in the structure is a main reason for superhardness of multilayered gradient coatings.
基金Project(51475449)supported by the National Natural Science Foundation of China
文摘A Cr/Cr2N/CrN multilayer coating with a thickness of 24.4 μm was deposited by multi-arc ion plating. The coating was systematically characterized by field emission scanning electron microscopy(FESEM), X-ray photoelectron spectrometry(XPS), energy dispersive spectroscopy(EDS), X-ray diffraction(XRD) and transmission electron microscopy(TEM). Hardness and adhesion were tested by nanoindentation and scratch tester, respectively. The friction properties were investigated by a reciprocating UMT-3MT ball-on-disk tribometer in air and seawater. The results showed that the multilayer coating consisted of three different layers, with Cr,Cr2N and CrN phases, respectively. Compared with CrN single layer coating, the adhesion of the multilayer coating was improved significantly, the hardness of the multilayer coating was(21±2) GPa. The corrosion resistance of the multilayer coating was also improved in artificial seawater. The friction coefficient of multilayer coating was lower than that of CrN single layer coating both in air and seawater.
基金Project(51171118)supported by the National Natural Science Foundation of ChinaProject(2012-4)supported by the Liaoning Provincial Key Laboratory of Advanced Materials,Shenyang University,China
文摘Cr/CrN multilayer coatings with bilayer periods in the range from 1351 to 260 nm were prepared on 304 stainless steel substrates by arc ion plating to study the microstructure and properties of multilayer coatings and stimulate their application.SEM results confirm the clear periodicity of the Cr/CrN multilayer coatings and the clear interface between individual layers.XRD patterns reveal that these multilayer coatings contain Cr,CrN and Cr_2N phases.Because Cr layer is softer than its nitride layer,the hardness decreases with the shortening of the bilayer period(or increasing volume fraction of Cr layer).The Cr/CrN multilayer coating with 862 nm period possesses the highest indentation toughness due to a proper individual Cr and nitride layer thickness.However,for the Cr/CrN multilayer with the bilayer period of 1351 nm,it possesses the lowest toughness due to more nitride phase.The indentation toughness of Cr/CrN multilayer coatings is related with their bilayer period.A coating with a proper individual Cr and nitride layer thickness possesses the highest indentation toughness.
基金Science foundation of Shanxi province, China (20041065)
文摘With advantages of high specific strength, low elastic module, good damping property et al., the magnesium alloys exhibit great potential applications in aerospace. But poor wear behavior results in limited use of magnesium alloy to static components. In this study, a 2 μm thick coating with 12 sub-layers of CrN and TiN is deposited alternately on the surface of magnesium alloy AZ91 by a novel method of arc-glow plasma depositing to improve its wear resistance. The composition and microstructure of the coating layer are analyzed by means of SEM, XRD and GDS. The friction coefficient is measured by ball on disc rubbing test, and the wear rates are also calculated. The results indicate that the friction coefficient is increased, but the wear rate is dropped sharply as compared with bare metal. The surface hardness is about HK0.01 1400.
基金Project(51505100)supported by the National Natural Science Foundation of China
文摘The heterogeneous multilayer interface of VN/Ag coatings and transition multilayer interface of VN/Ag coatings were prepared on Inconel 781 and Si(100),and the microstructures,mechanical and tribological properties were investigated from 25 to 700℃.The results showed that the surface roughness and average grain size of VN/Ag coatings with transition multilayer interface are obviously larger than those of VN/Ag coatings with heterogeneous multilayer interface.The coatings with transition multilayer interface have higher adhesion force and hardness than the coatings with heterogeneous multilayer interface,and both coatings can effectively restrict the initiation and propagation of microcracks.Both coatings have excellent self-adaptive lubricating properties with a decrease of friction coefficient as the temperature increases,but their wear rates reveal a drastic increase.The phase composition of the worn area of both coatings was investigated,which indicates that a smooth Ag,Magnéli phase(V2O5)and bimetallic oxides(Ag3VO4 and AgVO3)can be responsible to the excellent lubricity of both coatings.To sum up,the coatings with transition multilayer interface have excellent adaptive lubricating properties and can properly control the diffusion rate and release rate of the lubricating phase,indicating that they have great potential in solving the problem of friction and wear of mechanical parts.
基金This work was supported by the National Defense Pre-Research Projects[grant number ZS2015070132A12002].
文摘In order to predict the storage life of a certain type of HTPB(hydroyl-terminated polybutadiene)coating at 25℃ and analyze the influence of pre-strain on the storage life,the accelerated aging tests of HTPB coating at 40℃,50℃,60℃,70℃ with the pre-strain of 0%,3%,6%,9%,respectively were carried out.The variation regularity of the change of crosslinking density was analyzed and the aging model of HTPB coating under pre-strained thermally-accelerated aging was proposed.The storage life of HTPB coating at 25℃ was estimated by using the Berthelot equation as the end point of the aging life with a 30% decrease in maximum elongation.The results showed that the change of crosslinking density of HTPB coating increased with the increase of aging temperature and aging time,and decreased with the increase of pre-strain.Under 0% prestrain,the relationship between the change of crosslinking density of HTPB coating and the aging time can be described by the logarithmic model with the confidence probability greater than 99%.The stress relaxation phenomenon existed under 3%,6%and 9%pre-strained aging.The aging model considering chemical aging and pre-strain was established with the confidence probability greater than 90%.The storage life of HTPB coating was 15.2935 years at 25C under 0% prestrain,which was reduced by 13.9007%,75.6949% and 89.7859% under 3%,6% and 9% pre-strain,respectively.The existence of pre-strain has a serious impact on the storage life of HTPB coating,therefore,the pre-strain should be avoided as much as possible during the actual storage.
基金This work was financially supported by the Science Foundation of Lanzhou Institute Chemistry and Physics, Chinese Academy of Science (No.01-03).
文摘TiN/CrN multilayered hard coatings with TiCrN interlayer were deposited onhigh speed steel substrates by using a filtered cathodic vacuum arc technique. The structure andcomposition of the coatings were characterized by scanning electron microscopy (SEM) and Augerelectron spectroscopy (AES). A high adhesion of up to 80 N was demonstrated by scratching tests forthe multi-layered coatings. Nanoindentation tests were performed to determine the hardness andelastic modulus of the coatings as a function of the multiplayer modulation period. It was observedthat the hardness of the multilayered coatings is higher than those of either TiN or CrN singlecoatings, and it increases with decreasing modulation periods, which is consistent with predictionsfrom the Hall-Petch type strengthening mechanism, though at small modulation periods, deviation fromthe Hall-Petch relation has been observed for the multilayered coatings. The life-span of drillscoated with TiN/CrN multilayered is triple as long as that coated with TiN layer.
基金Funded by the National Natural Science Foundation of China(No. 50771070)Shanxi Province Science and Technology Key Projects (No. 20100321078-02)
文摘Fracture behavior of CrN coatings deposited on the surface of silicon and AISI52100 steel by different energy ion beam assisted magnetron sputtering technique （IBAMS） was studied using indentation and dynamic cycle impact. It is found that, for the coatings on silicon substrate, the cracks form in the indentation corners and then propagate outward under Vickers indentation. The coating prepared using ion assisted energy of 800 eV shows the highest fracture resistance due to its compact structure. Under Rockwell indentation, only finer radial cracks are found in the CrN coating on AISI 52100 steel without ion assisting while in the condition of ion assisting energy of 800 eV, radial, lateral cracks and spalling appear in the vicinity of indentation. The fracture of CrN coatings under dynamic cycle impact is similar to fatigue. The impact fracture resistance of CrN coatings increases with the increase of ion assisting energy.
