AZ31B magnesium alloy is widely used in transportation and aerospace fields due to its light weight and high strength,but it often causes structural failure due to fatigue fracture during service.Fatigue fracture is u...AZ31B magnesium alloy is widely used in transportation and aerospace fields due to its light weight and high strength,but it often causes structural failure due to fatigue fracture during service.Fatigue fracture is usually caused by the initiation of cracks on the surface of structural parts and the propagation of cracks to the interior of the specimen in the form of intergranular fracture.In order to improve the fatigue performance,this study proposes a method of pre-tension deformation and surface mechanical rolling treatment of AZ31B magnesium alloy,thereby changing the crack initiation area and increasing the crack propagation resistance.The experimental results show that:As the pre-tension deformation increases,the fatigue limit shows a trend of first rising and then decreasing.The 5PT specimen exhibits the optimal strengthening effect,with a fatigue limit of 115 MPa,which is a 27.78% improvement.Under surface mechanical rolling treatment,the fatigue limit reaches 140 MPa,which is a 55.56% improvement.When pre-tension deformation and surface mechanical rolling treatment are combined,the fatigue limit is further improved compared to individual strengthening methods.Among these,the 2PT+SMRT specimen shows the most significant strengthening effect,with a fatigue limit of 150 MPa,which is a 66.67% improvement.This study proposes a new strategy for improving the fatigue performance of AZ31B magnesium alloy,and reveals the synergistic strengthening mechanism of pre-tension deformation and surface mechanical rolling treatment of AZ31B magnesium alloy,which is of great significance for improving the fatigue performance of metal materials.展开更多
CdS/ZnS core-shell microparticles were prepared by a simple two-step method combining ultrasonic spray pyrolysis and chemical bath deposition.The core-shell structures showed enhanced photocatalytic properties compare...CdS/ZnS core-shell microparticles were prepared by a simple two-step method combining ultrasonic spray pyrolysis and chemical bath deposition.The core-shell structures showed enhanced photocatalytic properties compared with those of CdS or ZnS spherical particles.CdS/ZnS photocatalysts with different amount of ZnS loaded as shells were prepared by adjusting the concentrations of Zn and S precursors during synthesis.The optical properties and photocatalytic activity for hydrogen production were investigated and the amount of ZnS loaded as shell was optimized.Thermal annealing and hydrothermal sulfurization treatments were applied to the core-shell structure and both treatments enhanced the material＇s photocatalytic activity and stability by eliminating crystalline defects and surface states.The result showed that thermal annealing treatment improved the bulk crystallinity and hydrothermal sulfurization improved the surface properties.The sample subjected to both treatments showed the highest photocatalytic activity.These results indicate that CdS/ZnS core-shell microspheres are a simple structure that can be used as efficient photocatalysts.The hydrothermal sulfurization treatment may also be a useful surface treatment for metal sulfide photocatalysts.The simple two-step method provides a promising approach to the large-scale synthesis of core-shell microsphere catalysts.展开更多
The aim of this study was investigate the effects of heat treatment on the contact angle of Chinese fir, and the indicators affecting the change of contact an-gle change. It was determined that the duration of treatme...The aim of this study was investigate the effects of heat treatment on the contact angle of Chinese fir, and the indicators affecting the change of contact an-gle change. It was determined that the duration of treatment had significant effect on the change curves of contact angle of Chinese fir wood due to the change curves of contact angle became more centralized and orderly after the specimens heat treated at 180 ℃. Compared with the untreated wood, the contact angle in-creased from 51＆#176; to 124＆#176; after 4 h treatment, and hydroxyl absorbance of hy-drophilic functional groups decreased from 2.08 to 1.63, while carbonyl absorbance from 0.92 to 0.62. The surface roughness has not significant influence on the con-tact angle. Heat treatment of the Chinese fir caused surface morphological change, which produced hol owed-out phenomenon. The increased surface contact angle caused by heat treatment can be used for outdoor and sauna facilities.展开更多
The nanocrystalline microstructure of the surface of 316 stainless steel （316SS） induced by surface mechanical attrition treatment （SMAT） was determined by X-ray diffraction （XRD） and scanning electron microsco...The nanocrystalline microstructure of the surface of 316 stainless steel （316SS） induced by surface mechanical attrition treatment （SMAT） was determined by X-ray diffraction （XRD） and scanning electron microscopy （SEM）. The technique of hydrogen embrittlement was first used to obtain the information of the brittleness cleavage plane. The effects of SMAT and the following annealing process on the corrosion behavior of 316SS were investiga- ted by potentiodynamic polarization curves and potentiostatic critical pitting temperature measurements. The results demonstrated that the nanoerystalline layer with an average grain size of 19 nm was produced. However, there were lots of cracks on the surface, which led to the degradation in the corrosion resistance of 316SS after SMAT. Never- theless, after annealing treatment, the corrosion resistance of the nanocrystalline surface had been improved greatly. The higher the annealing temperature, the better was the corrosion resistance.展开更多
The effect of rare earths （RE） surface treatment of carbon fibers （CF） on tribological properties of CF reinforced polytetrafluoroethylene （PTFE） composites under oil-lubricated condition was investigated. Exper...The effect of rare earths （RE） surface treatment of carbon fibers （CF） on tribological properties of CF reinforced polytetrafluoroethylene （PTFE） composites under oil-lubricated condition was investigated. Experimental results revealed that RE treated CF reinforced PTFE （CF/PTFE） composite had the lowest friction coefficient and wear under various applied loads and sliding speeds compared with untreated and air-oxidated composites. X-ray photoelectron spectroscopy （XPS） study of carbon fiber surface showed that, after RE treatment, oxygen concentration increased obviously, and the amount of oxygen-containing groups on CF surfaces were largely increased. The increase in the amount of oxygen-containing groups enhanced interfacial adhesion between CF and PTFE matrix. With strong interfacial adhesion of the composite, stress could be effectively transmitted to carbon fibers; carbon fibers were strongly bonded with VITE matrix, and large scale rubbing-off of PTFE be prevented, therefore, tribological properties of the composite was improved.展开更多
The influence of cerium conversion coating（CeCC） modified by lanthanum in two forms of additive and post-treatment solution on the corrosion resistance, surface morphology and surface chemistry of the mild steel was...The influence of cerium conversion coating（CeCC） modified by lanthanum in two forms of additive and post-treatment solution on the corrosion resistance, surface morphology and surface chemistry of the mild steel was studied. Corrosion resistance was evaluated by electrochemical impedance spectroscopy,while the scanning electron microscopy, X-ray photoelectron spectroscopy and contact angle test were employed to investigate the surface characteristics. Results reveal that the CeCC post-treated by lanthanum containing solution gives rise to the deposition of a crack free and uniform conversion coating with enhanced corrosion resistance on the steel surface. Also, the surface free energy is increased after post-treatment.展开更多
This paper reports on a laboratory-based study carried out to evaluate the effectiveness of surface treatments on the durability of concrete and suggests a number of different evaluation methodologies for assessing th...This paper reports on a laboratory-based study carried out to evaluate the effectiveness of surface treatments on the durability of concrete and suggests a number of different evaluation methodologies for assessing the performance of various surface treatments. Durability of untreated and treated concrete specimens was evaluated by measuring chloride diffusion,charge passing capacity,air permeability and water absorption. A total of six concrete surface treatments were selected to represent different generic types,including coating,penetrant and mixed-use treatments. Results show that the concrete specimens with a coating procedure have a better long-term performance and effectiveness than the specimens with the penetrant treatments. This work also indicates that the wetting and drying cycles test can be used to assess the weatherability of the surface treatments. The ASTM C 1202 and the Autoclam air permeability test can be used to evaluate the effectiveness of surface treatments quantitatively. Further work is needed,however,to assess the longevity of the various surface treatments.展开更多
Mg-Li alloy,as a superlight metallic engineering material,shows great potential in the fields of aerospace and militarydue to its high specific strength,better formability,and excellent electromagnetic shielding perfo...Mg-Li alloy,as a superlight metallic engineering material,shows great potential in the fields of aerospace and militarydue to its high specific strength,better formability,and excellent electromagnetic shielding performance.The research process ofMg-Li alloys is reviewed and three main problems are pointed out.Aimed at the poor corrosion resistance of Mg-Li alloys,thecorrosion behavior is mainly summarized.The surface treatment technologies,including electroplating,electroless plating,plasmaspraying,molten salt replacement,conversion coating,anodizing,micro-arc oxidation,organic coating,and organic-inorganic hybridcoating,are introduced in detail.Finally,the future development of corrosion and protection of Mg?Li alloys is discussed.展开更多
Microarc oxidation was performed on Ti-6Al-4V in an electrolyte containing calcium and phosphate ions.Samples were hydrothermally treated in different solutions containing calcium and phosphate ions.Various hydroxyapa...Microarc oxidation was performed on Ti-6Al-4V in an electrolyte containing calcium and phosphate ions.Samples were hydrothermally treated in different solutions containing calcium and phosphate ions.Various hydroxyapatite coatings were formed.It was found that hydroxyapatite coating is improved by the addition of calcium and phosphate ions in hydrothermal solutions.The addition of phosphate ions promotes the nucleation and growth of hydroxyapatite.But the effect of single calcium ions is not obvious.The addition of calcium and phosphate ions increases the nucleation and growth of hydroxyapatite,but decreases the preferred growth trend in some extent.展开更多
The effect of high-energy electropulsing-ultrasonic surface treatment（EUST） on the surface properties and the microstructure evolution of C45 E4 steel was investigated. Refined microstructure and reduced surface rou...The effect of high-energy electropulsing-ultrasonic surface treatment（EUST） on the surface properties and the microstructure evolution of C45 E4 steel was investigated. Refined microstructure and reduced surface roughness were obtained owing to the surface nanocrystallization process. Compared with the ultrasonic surface treatment（UST）, the impact depth of the surface strengthened layer was increased by 40% to 700 μm after EUST. The average grain size of the surface nanocrystallization layer was reduced to 30-50 nm. The surface roughness of the C45 E4 steel was reduced to 0.25 μm, and the surface microhardness was dramatically enhanced to 460 HV. The improvement of microstructure and micro-hardness at ambient temperature was likely attributed to the acceleration of atomic diffusion and the enhancement of plastic deformation ability in the surface strengthened layer under the influence of electropulsing. Due to the electropulsing-assisted ultrasonic strengthening effect, the surface nanocrystallization in this ultrafast procedure was noticeably enhanced.展开更多
The effect of solution heat treatment （SHT） on mechanical properties, microstructure and surface quality of Al-1.2Mg-0.6Si-0.2Cu-0.6Zn alloy was investigated by tensile test, Erichsen test, surface topography, scann...The effect of solution heat treatment （SHT） on mechanical properties, microstructure and surface quality of Al-1.2Mg-0.6Si-0.2Cu-0.6Zn alloy was investigated by tensile test, Erichsen test, surface topography, scanning electron microscope （SEM） and electron back-scattered diffraction （EBSD）. The results indicate that with the increase in SHT temperature, yield strength and cupping test value （IE） of the sheets increase greatly and reach a peak value, then decrease. Meanwhile, intermetallic com- pounds dissolve into matrix gradually. The grains grow up as SHT temperature increases, and abnormal grain growth leads to the surface defects after solution-treated above 560 ~C. Considering mechanical properties, IE value, residual phases, grain size and surface quality of the sheets, SHT temperature for the alloy should not be higher than 550 ℃.展开更多
A nanostructured surface layer has been fabricated on an AISI H13 tool steel by means of surface mechanical attrition treatment （SMAT）.Strain-induced refinement processes of ferrite grains and carbide particles have...A nanostructured surface layer has been fabricated on an AISI H13 tool steel by means of surface mechanical attrition treatment （SMAT）.Strain-induced refinement processes of ferrite grains and carbide particles have been investigated by transmission electron microscopy （TEM） and scanning electron microscopy （SEM） in the SMAT surface layer.Grain refinement of ferrite is found to be dominated by dislocation activities and greatly facilitated by a large number of carbide particles at a depth 〉20 μm.The comparisons with microstructure refinement processes in other SMAT ferrite steels indicate that a larger volume fraction of carbide particles with a lower shear strength is expected to facilitate the refinement process of ferrite grains.展开更多
Surface modification is often performed using grit or shot blasting treatment for improving the performances of biomedical implants. The effects of blasting treatments using steel slag balls and spherical shots on the...Surface modification is often performed using grit or shot blasting treatment for improving the performances of biomedical implants. The effects of blasting treatments using steel slag balls and spherical shots on the surface and subsurface of titanium were studied in this paper. The treatments were conducted for 60-300 s using 2-5 mm steel slag bails and 3.18 mm spherical shots. The surface morphology, roughness, and elemental composition of titanium specimens were examined prior to and after the treatments. Irregular and rough titanium surfaces were formed after the treatment with the steel slag balls instead of the spherical shots. The former treatment also introduced some bioactive elements on the titanium surface, but the latter one yielded a harder surface layer. In conclusion, both steel slag ball and shot blasting treatment have their own specialization in modifying the surface of metallic biomaterials. Steel slag ball blasting is potential for improving the osseointegration quality of implants; but the shot blasting is more appropriate for improving the mechanical properties of temporary and load bearing implants, such as osteosynthesis plates.展开更多
Nanosecond-pulse diffuse discharges could provide high-density plasma and high-energy electrons at atmospheric pressure. In this paper, the surface treatment of Cu by nanosecond-pulse diffuse discharges is conducted i...Nanosecond-pulse diffuse discharges could provide high-density plasma and high-energy electrons at atmospheric pressure. In this paper, the surface treatment of Cu by nanosecond-pulse diffuse discharges is conducted in atmospheric air. Factors influencing the water contact angle （WCA）, chemical composition and microhardness, such as the gap spacing and treatment time, are investigated. The results show that after the plasma surface treatment, the WCA considerably decreases from 87~ to 42.3~, and the surface energy increases from 20.46 mJ m-2 to 66.28 mJ m-2. Results of energy dispersive x-ray analysis show that the concentration of carbon decreases, but the concentrations of oxygen and nitrogen increase significantly. Moreover, the microhardness increases by approximately 30% after the plasma treatment. The aforementioned changes on the Cu surface indicate the plasma surface treatment enhances the hydrophilicity and microhardness, and it cleans the carbon and achieves oxidization on the Cu surface. Furthermore, by increasing the gap spacing and treatment time, better treatment effects can be obtained. The micmhardness in the case of a 2.5 cm gap is higher than that in the case of a 3 cm gap. More oxygen and nitrogen species appear on the Cu surface for the 2.5 cm gap treatment than for the 3 cm gap treatment. The WCA significantly decreases with the treatment thne when it is no longer than 90 s, and then it reaches saturation. In addition, more oxygen-containing and nitrogen-containing groups appear after extended plasma treatment time. They contribute to the improvement of the hydrophilicity and oxidation on the Cu surface.展开更多
A nanocrystalline layer （NL） was fabricated on the surface of AZ31 magnesium （Mg） alloy sheet by surface mechanical attrition treatment （SMAT）. The microstructure of the Mg alloy was characterized by optical mic...A nanocrystalline layer （NL） was fabricated on the surface of AZ31 magnesium （Mg） alloy sheet by surface mechanical attrition treatment （SMAT）. The microstructure of the Mg alloy was characterized by optical microscopy, X-ray diffraction and microhardness test. The results showed that both the microstructure and microhardness of AZ31 Mg alloy sheet after SMAT revealed a gradient distribution along depth from surface to center. The thermal stability of the NL was investigated through characterizing the microstructure evolution during the post-isothermal annealing treatment within the temperature range from 150 to 250℃. The NL exhibits a certain degree of thermal stability below 150 ℃, while it disappears quickly when annealing at the temperature range of 200-250 ℃. The grain growth kinetics of the nanocrystalline of AZ31 Mg alloy induced by SMAT was investigated. The activation energy of nanocrystalline AZ31 Mg alloy was obtained with a value of 92.8 kJ/mol.展开更多
The performances of second harmonic gen eration (SHG) and optical parametric oscillator (OPO) in CdGeAs2 crystal are strongly influenced by surface quality. In this paper, the surfaces of samples were treated by mecha...The performances of second harmonic gen eration (SHG) and optical parametric oscillator (OPO) in CdGeAs2 crystal are strongly influenced by surface quality. In this paper, the surfaces of samples were treated by mechanical polishing (MP), chemical polishing (CP), chemical-mechanical polishing (CMP) and CP following CMP closely (CMP + CP). Then, the surface state was characterized by optical microscopy (OM), scanning electron microscopy (SEM), atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS). AFM measurements show that an ultra-smooth surface is achieved after CMP + CP treatment and the roughness value is 0.98 nm. Meanwhile, the roughness of the surfaces treated by MP, CP and CMP are 4.53, 2.83 and 1.38 nm, respectively. By XRD rocking curves, the diffraction peak which belongs to the wafer treated by CMP + CP is the highest in intensity and best symmetrical in shape. XPS analysis indicates that Ge4+ proportions of GeO2 in total Ge content of CdGeAs2 wafers' surface after MP, CP, CMP and CMP + CP treatment are 27.6%, 42.8%, 6.1% and 30.3%, respectively.展开更多
Nanocrystalline surface layers and gradient nanostructure in 5182 aluminum alloy have been produced through surface mechanical attrition treatment(SMAT). The results indicate that the gradient nanostructure can not on...Nanocrystalline surface layers and gradient nanostructure in 5182 aluminum alloy have been produced through surface mechanical attrition treatment(SMAT). The results indicate that the gradient nanostructure can not only improve the mechanical properties of 5182 Al alloy, but also has a certain effect on the Portevin-Le Chatelier(PLC) effect. The yield and ultimate tensile strength of 5182 Al alloy with SMAT are significantly improved combining with the decrease of fracture elongation compared with the as-received one. The PLC effect of 5182 Al alloy could be effectively postponed by the formation of gradient nanostructure after SMAT. It leads to the increase of critical strain of the PLC effect, more concentrated distribution of serrated strain, and increase of average stress amplitude in special strain range. The influence of grain size and gradient nanostructure on the PLC effect of 5182 Al alloy was also discussed in detail. Grain refinement could sharply increase the density of dislocations and hinder the movement of dislocations, which results in the decrease of moving speed of dislocations and the more concentrated distribution of solute atoms. The solute atoms would aggregate to form nano precipitates and further impede movement of dislocation. The stronger interaction between the dislocations and the nano precipitates is the main mechanism of postponed PLC effect.展开更多
Strong metal/non-polar plastic dissimilar joints are highly demanded for the lightweight design in many fields,which,however,are rather challenging to achieve directly via welding.In this study,we designed a laser pro...Strong metal/non-polar plastic dissimilar joints are highly demanded for the lightweight design in many fields,which,however,are rather challenging to achieve directly via welding.In this study,we designed a laser processing pretreatment on the Al alloy to create a deep porous Al surface structure,which was successfully joined to the polypropylene(PP) via friction spot welding.A maximum joint strength of29 MPa was achieved,the same as that of the base PP(i.e.the joint efficiency reached 100%),much larger than ever reported.The joining mechanism of the Al alloy and the PP was mainly attributed to the large mechanical interlocking effect between the laser processed Al porous structure and the re-solidified PP and the formation of chemical bond at the interface.The deep porous Al surface structure modified by laser processing largely changed the Al-PP reaction feature.The evidence of the C-O-Al chemical bond was first time found at the non-polar plastic/Al joint interface,which was the reaction result between the oxide on the Al alloy surface and thermal oxidization products of the PP during welding.This study provides a new way for enhancing metal-plastic joints via surface laser treatment techniques.展开更多
Non-thermal plasmas under atmospheric pressure are of great interest in polymer surface processing because of their convenience, effectiveness and low cost. In this paper, the treatment of Polyethylene terephthalate (...Non-thermal plasmas under atmospheric pressure are of great interest in polymer surface processing because of their convenience, effectiveness and low cost. In this paper, the treatment of Polyethylene terephthalate (PET) film surface for improving hydrophilicity using the non-thermal plasma generated by atmospheric pressure glow discharge (APGD) in air is conducted. The discharge characteristics of APGD are shown by measurement of their electrical discharge parameters and observation of light-emission phenomena, and the surface properties of PET before and after the APGD treatment are studied using contact angle measurement, x-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). It is found that the APGD is homogeneous and stable in the whole gas gap, which differs from the commonly filamentary dielectric barrier discharge (DBD). A short time (several seconds) APGD treatment can modify the surface characteristics of PET film markedly and uniformly. After 10 s APGD treatment, the展开更多
基金the generous support from natural Science Foundation of Shanxi Province(No.202203021221040 and No.201901D111106).
文摘AZ31B magnesium alloy is widely used in transportation and aerospace fields due to its light weight and high strength,but it often causes structural failure due to fatigue fracture during service.Fatigue fracture is usually caused by the initiation of cracks on the surface of structural parts and the propagation of cracks to the interior of the specimen in the form of intergranular fracture.In order to improve the fatigue performance,this study proposes a method of pre-tension deformation and surface mechanical rolling treatment of AZ31B magnesium alloy,thereby changing the crack initiation area and increasing the crack propagation resistance.The experimental results show that:As the pre-tension deformation increases,the fatigue limit shows a trend of first rising and then decreasing.The 5PT specimen exhibits the optimal strengthening effect,with a fatigue limit of 115 MPa,which is a 27.78% improvement.Under surface mechanical rolling treatment,the fatigue limit reaches 140 MPa,which is a 55.56% improvement.When pre-tension deformation and surface mechanical rolling treatment are combined,the fatigue limit is further improved compared to individual strengthening methods.Among these,the 2PT+SMRT specimen shows the most significant strengthening effect,with a fatigue limit of 150 MPa,which is a 66.67% improvement.This study proposes a new strategy for improving the fatigue performance of AZ31B magnesium alloy,and reveals the synergistic strengthening mechanism of pre-tension deformation and surface mechanical rolling treatment of AZ31B magnesium alloy,which is of great significance for improving the fatigue performance of metal materials.
基金supported by the National Natural Science Foundation of China(51202186,51323011)the Fundamental Research Funds for the Central University(xjj2016039)~~
文摘CdS/ZnS core-shell microparticles were prepared by a simple two-step method combining ultrasonic spray pyrolysis and chemical bath deposition.The core-shell structures showed enhanced photocatalytic properties compared with those of CdS or ZnS spherical particles.CdS/ZnS photocatalysts with different amount of ZnS loaded as shells were prepared by adjusting the concentrations of Zn and S precursors during synthesis.The optical properties and photocatalytic activity for hydrogen production were investigated and the amount of ZnS loaded as shell was optimized.Thermal annealing and hydrothermal sulfurization treatments were applied to the core-shell structure and both treatments enhanced the material＇s photocatalytic activity and stability by eliminating crystalline defects and surface states.The result showed that thermal annealing treatment improved the bulk crystallinity and hydrothermal sulfurization improved the surface properties.The sample subjected to both treatments showed the highest photocatalytic activity.These results indicate that CdS/ZnS core-shell microspheres are a simple structure that can be used as efficient photocatalysts.The hydrothermal sulfurization treatment may also be a useful surface treatment for metal sulfide photocatalysts.The simple two-step method provides a promising approach to the large-scale synthesis of core-shell microsphere catalysts.
基金Supported by Science and Technology Programs of Liangqing District of Nanning City(201304A)Science and Technology Program of Guangxi University(XJZ120270)~~
文摘The aim of this study was investigate the effects of heat treatment on the contact angle of Chinese fir, and the indicators affecting the change of contact an-gle change. It was determined that the duration of treatment had significant effect on the change curves of contact angle of Chinese fir wood due to the change curves of contact angle became more centralized and orderly after the specimens heat treated at 180 ℃. Compared with the untreated wood, the contact angle in-creased from 51＆#176; to 124＆#176; after 4 h treatment, and hydroxyl absorbance of hy-drophilic functional groups decreased from 2.08 to 1.63, while carbonyl absorbance from 0.92 to 0.62. The surface roughness has not significant influence on the con-tact angle. Heat treatment of the Chinese fir caused surface morphological change, which produced hol owed-out phenomenon. The increased surface contact angle caused by heat treatment can be used for outdoor and sauna facilities.
基金Item Sponsored by National Natural Science Foundation of China (50571027)
文摘The nanocrystalline microstructure of the surface of 316 stainless steel （316SS） induced by surface mechanical attrition treatment （SMAT） was determined by X-ray diffraction （XRD） and scanning electron microscopy （SEM）. The technique of hydrogen embrittlement was first used to obtain the information of the brittleness cleavage plane. The effects of SMAT and the following annealing process on the corrosion behavior of 316SS were investiga- ted by potentiodynamic polarization curves and potentiostatic critical pitting temperature measurements. The results demonstrated that the nanoerystalline layer with an average grain size of 19 nm was produced. However, there were lots of cracks on the surface, which led to the degradation in the corrosion resistance of 316SS after SMAT. Never- theless, after annealing treatment, the corrosion resistance of the nanocrystalline surface had been improved greatly. The higher the annealing temperature, the better was the corrosion resistance.
基金the National Natural Science Foundation of China (50275093)
文摘The effect of rare earths （RE） surface treatment of carbon fibers （CF） on tribological properties of CF reinforced polytetrafluoroethylene （PTFE） composites under oil-lubricated condition was investigated. Experimental results revealed that RE treated CF reinforced PTFE （CF/PTFE） composite had the lowest friction coefficient and wear under various applied loads and sliding speeds compared with untreated and air-oxidated composites. X-ray photoelectron spectroscopy （XPS） study of carbon fiber surface showed that, after RE treatment, oxygen concentration increased obviously, and the amount of oxygen-containing groups on CF surfaces were largely increased. The increase in the amount of oxygen-containing groups enhanced interfacial adhesion between CF and PTFE matrix. With strong interfacial adhesion of the composite, stress could be effectively transmitted to carbon fibers; carbon fibers were strongly bonded with VITE matrix, and large scale rubbing-off of PTFE be prevented, therefore, tribological properties of the composite was improved.
文摘The influence of cerium conversion coating（CeCC） modified by lanthanum in two forms of additive and post-treatment solution on the corrosion resistance, surface morphology and surface chemistry of the mild steel was studied. Corrosion resistance was evaluated by electrochemical impedance spectroscopy,while the scanning electron microscopy, X-ray photoelectron spectroscopy and contact angle test were employed to investigate the surface characteristics. Results reveal that the CeCC post-treated by lanthanum containing solution gives rise to the deposition of a crack free and uniform conversion coating with enhanced corrosion resistance on the steel surface. Also, the surface free energy is increased after post-treatment.
基金Project (Nos. 50920105806, 50538070 and 50808157) supported by the National Natural Science Foundation of China
文摘This paper reports on a laboratory-based study carried out to evaluate the effectiveness of surface treatments on the durability of concrete and suggests a number of different evaluation methodologies for assessing the performance of various surface treatments. Durability of untreated and treated concrete specimens was evaluated by measuring chloride diffusion,charge passing capacity,air permeability and water absorption. A total of six concrete surface treatments were selected to represent different generic types,including coating,penetrant and mixed-use treatments. Results show that the concrete specimens with a coating procedure have a better long-term performance and effectiveness than the specimens with the penetrant treatments. This work also indicates that the wetting and drying cycles test can be used to assess the weatherability of the surface treatments. The ASTM C 1202 and the Autoclam air permeability test can be used to evaluate the effectiveness of surface treatments quantitatively. Further work is needed,however,to assess the longevity of the various surface treatments.
基金Project(2017zzts005) supported by the Fundamental Research Funds for the Central Universities of Central South University
文摘Mg-Li alloy,as a superlight metallic engineering material,shows great potential in the fields of aerospace and militarydue to its high specific strength,better formability,and excellent electromagnetic shielding performance.The research process ofMg-Li alloys is reviewed and three main problems are pointed out.Aimed at the poor corrosion resistance of Mg-Li alloys,thecorrosion behavior is mainly summarized.The surface treatment technologies,including electroplating,electroless plating,plasmaspraying,molten salt replacement,conversion coating,anodizing,micro-arc oxidation,organic coating,and organic-inorganic hybridcoating,are introduced in detail.Finally,the future development of corrosion and protection of Mg?Li alloys is discussed.
基金Shanghai Leading Academic Discipline Project(J50503)Shanghai National Research Fund(09ZR1422100)Innovation Research Fund of Education of Shanghai Municipality(10YZ94)
文摘Microarc oxidation was performed on Ti-6Al-4V in an electrolyte containing calcium and phosphate ions.Samples were hydrothermally treated in different solutions containing calcium and phosphate ions.Various hydroxyapatite coatings were formed.It was found that hydroxyapatite coating is improved by the addition of calcium and phosphate ions in hydrothermal solutions.The addition of phosphate ions promotes the nucleation and growth of hydroxyapatite.But the effect of single calcium ions is not obvious.The addition of calcium and phosphate ions increases the nucleation and growth of hydroxyapatite,but decreases the preferred growth trend in some extent.
基金Funded by the Natural Science Foundation of China(No.50571048)the Research & Development Funding Project of Shenzhen(No.JCYJ20120619152539900)
文摘The effect of high-energy electropulsing-ultrasonic surface treatment（EUST） on the surface properties and the microstructure evolution of C45 E4 steel was investigated. Refined microstructure and reduced surface roughness were obtained owing to the surface nanocrystallization process. Compared with the ultrasonic surface treatment（UST）, the impact depth of the surface strengthened layer was increased by 40% to 700 μm after EUST. The average grain size of the surface nanocrystallization layer was reduced to 30-50 nm. The surface roughness of the C45 E4 steel was reduced to 0.25 μm, and the surface microhardness was dramatically enhanced to 460 HV. The improvement of microstructure and micro-hardness at ambient temperature was likely attributed to the acceleration of atomic diffusion and the enhancement of plastic deformation ability in the surface strengthened layer under the influence of electropulsing. Due to the electropulsing-assisted ultrasonic strengthening effect, the surface nanocrystallization in this ultrafast procedure was noticeably enhanced.
基金supported by the National Program on Key Basic Research Project of China(No. 2012CB619504)the National Natural Science Foundation of China(No.51271037)
文摘The effect of solution heat treatment （SHT） on mechanical properties, microstructure and surface quality of Al-1.2Mg-0.6Si-0.2Cu-0.6Zn alloy was investigated by tensile test, Erichsen test, surface topography, scanning electron microscope （SEM） and electron back-scattered diffraction （EBSD）. The results indicate that with the increase in SHT temperature, yield strength and cupping test value （IE） of the sheets increase greatly and reach a peak value, then decrease. Meanwhile, intermetallic com- pounds dissolve into matrix gradually. The grains grow up as SHT temperature increases, and abnormal grain growth leads to the surface defects after solution-treated above 560 ~C. Considering mechanical properties, IE value, residual phases, grain size and surface quality of the sheets, SHT temperature for the alloy should not be higher than 550 ℃.
基金supported by the National Natural Science Foundation of China (Nos. 50621091,50701044and 50890171)the Ministry of Science and Technology(No. 2005CB623604)the National High Technology Research and Development Program of China (No.2007AA03Z352)
文摘A nanostructured surface layer has been fabricated on an AISI H13 tool steel by means of surface mechanical attrition treatment （SMAT）.Strain-induced refinement processes of ferrite grains and carbide particles have been investigated by transmission electron microscopy （TEM） and scanning electron microscopy （SEM） in the SMAT surface layer.Grain refinement of ferrite is found to be dominated by dislocation activities and greatly facilitated by a large number of carbide particles at a depth 〉20 μm.The comparisons with microstructure refinement processes in other SMAT ferrite steels indicate that a larger volume fraction of carbide particles with a lower shear strength is expected to facilitate the refinement process of ferrite grains.
基金financially funded by the Institute for Research and Community Service,Gadjah Mada University,Indonesia,through Research Grant for Junior Lecturer 2012 (Grant No. LPPM-UGM/315/BID.I/2012)
文摘Surface modification is often performed using grit or shot blasting treatment for improving the performances of biomedical implants. The effects of blasting treatments using steel slag balls and spherical shots on the surface and subsurface of titanium were studied in this paper. The treatments were conducted for 60-300 s using 2-5 mm steel slag bails and 3.18 mm spherical shots. The surface morphology, roughness, and elemental composition of titanium specimens were examined prior to and after the treatments. Irregular and rough titanium surfaces were formed after the treatment with the steel slag balls instead of the spherical shots. The former treatment also introduced some bioactive elements on the titanium surface, but the latter one yielded a harder surface layer. In conclusion, both steel slag ball and shot blasting treatment have their own specialization in modifying the surface of metallic biomaterials. Steel slag ball blasting is potential for improving the osseointegration quality of implants; but the shot blasting is more appropriate for improving the mechanical properties of temporary and load bearing implants, such as osteosynthesis plates.
基金partly supported by National Natural Science Foundation of China under Grant No. 51477164the National Basic Research Program of China under Grant No. 2014CB239505-03+1 种基金the State Key Laboratory of Alternate Electrical Power System with Renewable Energy Sources under Grant No. LAPS16013the Science and Technology Project of State Grid Corporation of China
文摘Nanosecond-pulse diffuse discharges could provide high-density plasma and high-energy electrons at atmospheric pressure. In this paper, the surface treatment of Cu by nanosecond-pulse diffuse discharges is conducted in atmospheric air. Factors influencing the water contact angle （WCA）, chemical composition and microhardness, such as the gap spacing and treatment time, are investigated. The results show that after the plasma surface treatment, the WCA considerably decreases from 87~ to 42.3~, and the surface energy increases from 20.46 mJ m-2 to 66.28 mJ m-2. Results of energy dispersive x-ray analysis show that the concentration of carbon decreases, but the concentrations of oxygen and nitrogen increase significantly. Moreover, the microhardness increases by approximately 30% after the plasma treatment. The aforementioned changes on the Cu surface indicate the plasma surface treatment enhances the hydrophilicity and microhardness, and it cleans the carbon and achieves oxidization on the Cu surface. Furthermore, by increasing the gap spacing and treatment time, better treatment effects can be obtained. The micmhardness in the case of a 2.5 cm gap is higher than that in the case of a 3 cm gap. More oxygen and nitrogen species appear on the Cu surface for the 2.5 cm gap treatment than for the 3 cm gap treatment. The WCA significantly decreases with the treatment thne when it is no longer than 90 s, and then it reaches saturation. In addition, more oxygen-containing and nitrogen-containing groups appear after extended plasma treatment time. They contribute to the improvement of the hydrophilicity and oxidation on the Cu surface.
基金provided by the Grant 2012CB932203 of the National Key Basic Research Program of the Chinese Ministry of Science and Technology and Technologythe Croucher Foundation (No. 9500006)+4 种基金Hong Kong Collaborative Research Fund (CRF) Scheme (No. C402814G)the National Natural Science Foundation of China (No. 51464034)the Hong Kong Scholars Program (No. XJ2012025)the China Postdoctoral Science Foundation funded project (Nos. 2012T50594, 2014M551866)the Jiangxi Postdoctoral Science Foundation (No. 2014KY11)
文摘A nanocrystalline layer （NL） was fabricated on the surface of AZ31 magnesium （Mg） alloy sheet by surface mechanical attrition treatment （SMAT）. The microstructure of the Mg alloy was characterized by optical microscopy, X-ray diffraction and microhardness test. The results showed that both the microstructure and microhardness of AZ31 Mg alloy sheet after SMAT revealed a gradient distribution along depth from surface to center. The thermal stability of the NL was investigated through characterizing the microstructure evolution during the post-isothermal annealing treatment within the temperature range from 150 to 250℃. The NL exhibits a certain degree of thermal stability below 150 ℃, while it disappears quickly when annealing at the temperature range of 200-250 ℃. The grain growth kinetics of the nanocrystalline of AZ31 Mg alloy induced by SMAT was investigated. The activation energy of nanocrystalline AZ31 Mg alloy was obtained with a value of 92.8 kJ/mol.
基金financially supported by the National Natural Science Foundation of China (No. 50732005)the National High Technology Research and Development Program of China (No. 007AA03Z443)
文摘The performances of second harmonic gen eration (SHG) and optical parametric oscillator (OPO) in CdGeAs2 crystal are strongly influenced by surface quality. In this paper, the surfaces of samples were treated by mechanical polishing (MP), chemical polishing (CP), chemical-mechanical polishing (CMP) and CP following CMP closely (CMP + CP). Then, the surface state was characterized by optical microscopy (OM), scanning electron microscopy (SEM), atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS). AFM measurements show that an ultra-smooth surface is achieved after CMP + CP treatment and the roughness value is 0.98 nm. Meanwhile, the roughness of the surfaces treated by MP, CP and CMP are 4.53, 2.83 and 1.38 nm, respectively. By XRD rocking curves, the diffraction peak which belongs to the wafer treated by CMP + CP is the highest in intensity and best symmetrical in shape. XPS analysis indicates that Ge4+ proportions of GeO2 in total Ge content of CdGeAs2 wafers' surface after MP, CP, CMP and CMP + CP treatment are 27.6%, 42.8%, 6.1% and 30.3%, respectively.
基金financially supported by the National Key Research and Development Plan(No.2017YFB1103700)the Natural Science Foundation of China(Nos.51671101 and51464034)+1 种基金the Natural Science foundation of Jiangxi Province(Nos.20172BCB22002,20171BCD40003,20161ACB21003,20162BCB23013)the Science and Technology Key Research Plan in Jiangxi Educational Department(No.GJJ150010)
文摘Nanocrystalline surface layers and gradient nanostructure in 5182 aluminum alloy have been produced through surface mechanical attrition treatment(SMAT). The results indicate that the gradient nanostructure can not only improve the mechanical properties of 5182 Al alloy, but also has a certain effect on the Portevin-Le Chatelier(PLC) effect. The yield and ultimate tensile strength of 5182 Al alloy with SMAT are significantly improved combining with the decrease of fracture elongation compared with the as-received one. The PLC effect of 5182 Al alloy could be effectively postponed by the formation of gradient nanostructure after SMAT. It leads to the increase of critical strain of the PLC effect, more concentrated distribution of serrated strain, and increase of average stress amplitude in special strain range. The influence of grain size and gradient nanostructure on the PLC effect of 5182 Al alloy was also discussed in detail. Grain refinement could sharply increase the density of dislocations and hinder the movement of dislocations, which results in the decrease of moving speed of dislocations and the more concentrated distribution of solute atoms. The solute atoms would aggregate to form nano precipitates and further impede movement of dislocation. The stronger interaction between the dislocations and the nano precipitates is the main mechanism of postponed PLC effect.
基金supported by the National Natural Science Foundation of China (Nos. 51975553 and 51931009)IMR SYNL-T.S. Kê Research Fellowship。
文摘Strong metal/non-polar plastic dissimilar joints are highly demanded for the lightweight design in many fields,which,however,are rather challenging to achieve directly via welding.In this study,we designed a laser processing pretreatment on the Al alloy to create a deep porous Al surface structure,which was successfully joined to the polypropylene(PP) via friction spot welding.A maximum joint strength of29 MPa was achieved,the same as that of the base PP(i.e.the joint efficiency reached 100%),much larger than ever reported.The joining mechanism of the Al alloy and the PP was mainly attributed to the large mechanical interlocking effect between the laser processed Al porous structure and the re-solidified PP and the formation of chemical bond at the interface.The deep porous Al surface structure modified by laser processing largely changed the Al-PP reaction feature.The evidence of the C-O-Al chemical bond was first time found at the non-polar plastic/Al joint interface,which was the reaction result between the oxide on the Al alloy surface and thermal oxidization products of the PP during welding.This study provides a new way for enhancing metal-plastic joints via surface laser treatment techniques.
文摘Non-thermal plasmas under atmospheric pressure are of great interest in polymer surface processing because of their convenience, effectiveness and low cost. In this paper, the treatment of Polyethylene terephthalate (PET) film surface for improving hydrophilicity using the non-thermal plasma generated by atmospheric pressure glow discharge (APGD) in air is conducted. The discharge characteristics of APGD are shown by measurement of their electrical discharge parameters and observation of light-emission phenomena, and the surface properties of PET before and after the APGD treatment are studied using contact angle measurement, x-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). It is found that the APGD is homogeneous and stable in the whole gas gap, which differs from the commonly filamentary dielectric barrier discharge (DBD). A short time (several seconds) APGD treatment can modify the surface characteristics of PET film markedly and uniformly. After 10 s APGD treatment, the
