China's economic growth and economic development has entered a new stage,and the optimization and upgrading of industrial structure is the core driving force for China to achieve high-quality economic development ...China's economic growth and economic development has entered a new stage,and the optimization and upgrading of industrial structure is the core driving force for China to achieve high-quality economic development during the"14 th Five-Year Plan"period.Property tax has a conductive effect on the upgrading of industrial structure.Therefore,from the perspective of property tax and industrial structure adjustment and the relationship between them,this study summarizes the relevant research of domestic and foreign scholars.On the basis of the research,the paper puts forward some relevant policy suggestions on improving China's property tax and promoting the optimization and upgrading of China's industrial structure.展开更多
Carbonated recycled powder as cementitious auxiliary material can reduce carbon emissions and realize high-quality recycling of recycled concrete.In this paper,microscopic property of recycled powder with three carbon...Carbonated recycled powder as cementitious auxiliary material can reduce carbon emissions and realize high-quality recycling of recycled concrete.In this paper,microscopic property of recycled powder with three carbonation methods was tested through XRD and SEM,the mechanical property and microstructure of recycled powder mortar with three replacement rates were studied by ISO method and SEM,and the strengthening mechanism was analyzed.The results showed that the mechanical property of recycled powder mortar decreased with the increasing of replacement rate.It is suggested that the replacement rate of recycled powder should not exceed 20%.The strength index and activity index of carbonated recycled powder mortar were improved,in which the flexural strength was increased by 27.85%and compressive strength was increased by 20%at the maximum.Recycled powder can be quickly and completely carbonated,and the improvement effect of CH pre-soaking carbonation was the best.The activity index of carbonated recycled powder can meet the requirements of Grade II technical standard for recycled powder.Microscopic results revealed the activation mechanism of carbonated recycled powder such as surplus calcium source effect,alkaline polycondensation effect and carbonation enhancement effect.展开更多
Cryogenic treatment was used to improve the tribological properties of Ti6Al4V artificial hip joint implants.Cryogenic treatment at-196℃with different holding time were carried out on Ti6Al4V specimens fabricated usi...Cryogenic treatment was used to improve the tribological properties of Ti6Al4V artificial hip joint implants.Cryogenic treatment at-196℃with different holding time were carried out on Ti6Al4V specimens fabricated using electron beam melting(EBM),and their microstructure and tribological properties evolution were systematically analyzed by scanning electron microscopy(SEM),vickers hardness,and wear tests.The experimental results show that the as-fabricated specimen consists of lamellarαphase andβcolumnar crystal.While,the thickness of lamellarαphase decreased after cryogenic treatment.In addition,it can be found that the fineαphase was precipitated and dispersed between the lamellarαphase with the holding time increase.Vickers hardness shows a trend of first increasing and then decreasing.The wear rate of the specimen cryogenic treated for 24 h is the minimum and the average friction coefficient is 0.50,which is reduced by 14.61%compared with the as-fabricated.The wear mechanism of the as-fabricated specimen is severe exfoliation,adhesive,abrasive,and slight fatigue wear.However,the specimen cryogenic treated for 24 h shows slight adhesive and abrasive wear.It can be concluded that it is feasibility of utilizing cryogenic treatment to reduce the wear of EBMed Ti6Al4V.展开更多
The band structure,DOSs,and optical properties of(Y_(0.75)Ca_(0.25))(Cu_(0.75)Mn_(0.25))SO,including dielectric function,absorption function,reflection function,and energy loss spectrum were studied by using the first...The band structure,DOSs,and optical properties of(Y_(0.75)Ca_(0.25))(Cu_(0.75)Mn_(0.25))SO,including dielectric function,absorption function,reflection function,and energy loss spectrum were studied by using the first-principles calculation.The calculation results indicate that(Y_(0.75)Ca_(0.25))(Cu_(0.75)Mn_(0.25))SO is a direct bandgap semiconductor with a bandgap of 1.1 eV.The Fermi surface is asymmetric and exhibits spin splitting phenomenon.The new type of dilute magnetic semiconductor(Y_(0.75)Ca_(0.25))(Cu_(0.75)Mn_(0.25))SO exhibits significant light loss around 70 eV,with light reflection gradually increasing after 30 eV,and light absorption mainly occurring around 8-30 eV.These results also provide a basis for the discovery of more types of 1111 phase new dilute magnetic semiconductors in the future.展开更多
In the reform process of the rural land property rights system,the incentive mechanism of the rural land property rights system has a crucial impact on the production activities of rural economic entities.Due to the d...In the reform process of the rural land property rights system,the incentive mechanism of the rural land property rights system has a crucial impact on the production activities of rural economic entities.Due to the different rights structures of the property rights system in different social and economic development stages,the land rights and interests enjoyed by rural economic subjects are different,and the degree of incentives for farmers is also different.This difference in incentives affects farmers investment in agricultural production factors,which in turn affects agricultural performance.This paper analyzes the incentive impacts of the structure of rural land property rights on the changes of farmers land rights and agricultural performance since the founding of the People s Republic of China,in order to further deepen the reform of the land system,protect the rights and interests of farmers,promote the modernization of agriculture and rural areas,and explore the realization form and operation mechanism of the rural collective land system in the new era.展开更多
Laser powder bed fusion(LPBF)is a widely recognized additive manufacturing technology that can fabricate complex components rapidly through layer-by-layer formation.However,there is a paucity of research on the effect...Laser powder bed fusion(LPBF)is a widely recognized additive manufacturing technology that can fabricate complex components rapidly through layer-by-layer formation.However,there is a paucity of research on the effect of laser scanning speed on the cellular microstructure and mechanical properties of martensitic stainless steel.This study systematically investigated the influence of laser scanning speed on the cellular microstructure and mechanical properties of a developed Fe11Cr8Ni5Co3Mo martensitic stainless steel produced by LPBF.The results show that increasing the laser scanning speed from 400 to 1000 mm/s does not lead to a noticeable change in the phase fraction,but it reduces the average size of the cellular microstructure from 0.60 to 0.35μm.The scanning speeds of 400 and 1000 mm/s both had adverse effects on performances of sample,resulting in inadequate fusion and keyhole defects respectively.The optimal scanning speed for fabricating samples was determined to be 800 mm/s,which obtained the highest room temperature tensile strength and elongation,with the ultimate tensile strength measured at(1088.3±2.0)MPa and the elongation of(16.76±0.10)%.Furthermore,the mechanism of the evolution of surface morphology,defects,and energy input were clarified,and the relationship between cellular microstructure size and mechanical properties was also established.展开更多
Magnesium alloys are emerging as promising alternatives to traditional orthopedic implant materials thanks to their biodegradability,biocompatibility,and impressive mechanical characteristics.However,their rapid in-vi...Magnesium alloys are emerging as promising alternatives to traditional orthopedic implant materials thanks to their biodegradability,biocompatibility,and impressive mechanical characteristics.However,their rapid in-vivo degradation presents challenges,notably in upholding mechanical integrity over time.This study investigates the impact of high-temperature thermal processing on the mechanical and degradation attributes of a lean Mg-Zn-Ca-Mn alloy,ZX10.Utilizing rapid,cost-efficient characterization methods like X-ray diffraction and optical microscopy,we swiftly examine microstructural changes post-thermal treatment.Employing Pearson correlation coefficient analysis,we unveil the relationship between microstructural properties and critical targets(properties):hardness and corrosion resistance.Additionally,leveraging the least absolute shrinkage and selection operator(LASSO),we pinpoint the dominant microstructural factors among closely correlated variables.Our findings underscore the significant role of grain size refinement in strengthening and the predominance of the ternary Ca_(2)Mg_(6)Zn_(3)phase in corrosion behavior.This suggests that achieving an optimal blend of strength and corrosion resistance is attainable through fine grains and reduced concentration of ternary phases.This thorough investigation furnishes valuable insights into the intricate interplay of processing,structure,and properties in magnesium alloys,thereby advancing the development of superior biodegradable implant materials.展开更多
In this study,HEA/AI composite interlayer was used to fabricate Ti/Mg bimetal composites by solidliquid compound casting process.The Al layer was prepared on the surface of TC4 alloy by hot dipping,and the FeCoNiCr HE...In this study,HEA/AI composite interlayer was used to fabricate Ti/Mg bimetal composites by solidliquid compound casting process.The Al layer was prepared on the surface of TC4 alloy by hot dipping,and the FeCoNiCr HEA layer was prepared by magnetron sputtering onto the Al layer.The influence of the HEA layer thickness and pouring temperature on interface evolution was investigated based on SEM observation and thermodynamic analysis.Results indicate that the sluggish diffusion effect of HEA can effectively inhibit the interfacial diffusion between Al and Mg,which is conducive to the formation of solid solution,especially when the thickness of HEA is 800 nm.With the increase of casting temperature from 720 ℃ to 730 ℃,740℃,and 750 ℃,α-Al(Mg),α-Al(Mg)+Al3Mg2,Al3Mg2+Al12Mg17,and Al12Mg17+δ-Mg are formed at the interface of Ti/Mg bimetal,respectively.When the thickness of the HEA layer is 800 nm and the pouring temperature is 720 ℃,the bonding strength of the Ti/Mg bimetal can reach the maximum of 93.6 MPa.展开更多
Face-centered cubic (f.c.c.) high entropy alloys (HEAs) are attracting more and more attention owing to their excellent strength and ductility synergy, irradiation resistance, etc. However, the yield strength of f.c.c...Face-centered cubic (f.c.c.) high entropy alloys (HEAs) are attracting more and more attention owing to their excellent strength and ductility synergy, irradiation resistance, etc. However, the yield strength of f.c.c. HEAs is generally low, significantly limiting their practical applications. Recently, the alloying of W has been evidenced to be able to remarkably improve the mechanical properties of f.c.c. HEAs and is becoming a hot topic in the community of HEAs. To date, when W is introduced, multiple strengthening mechanisms, including solid-solution strengthening, precipitation strengthening (μphase,σphase, and b.c.c. phase), and grain-refinement strengthening, have been discovered to be activated or enhanced. Apart from mechanical properties, the addition of W improves corrosion resistance as W helps to form a dense WO_(3) film on the alloy surface. Until now, despite the extensive studies in the literature, there is no available review paper focusing on the W doping of the f.c.c. HEAs. In that context, the effects of W doping on f.c.c. HEAs were reviewed in this work from three aspects, i.e., microstructure,mechanical property, and corrosion resistance. We expect this work can advance the application of the W alloying strategy in the f.c.c. HEAs.展开更多
Ceramic coating incorporated with nano-SiC was obtained on AZ91D magnesium alloy during MAO by adding nano-SiC into the silicate-aluminate-based composite electrolyte. The microstructure, thickness, phase analysis, el...Ceramic coating incorporated with nano-SiC was obtained on AZ91D magnesium alloy during MAO by adding nano-SiC into the silicate-aluminate-based composite electrolyte. The microstructure, thickness, phase analysis, element composition and hardness of the coatings were respectively investigated by scanning electron microscopy(SEM), film thickness meter, X-ray diffraction (XRD), energy disperse spectroscopy(EDS) and Vickers hardness tester. The wear resistance of Mg alloy and coatings were evaluated by friction and wear apparatus, while the corrosion resistance of Mg alloy and coatings were evaluated by potentiodynamic polarization test and electrochemical impedance spectroscopy (EIS). The results show that after adding nano-SiC into the electrolyte, both the striking voltage and final voltage decrease, the size and number of the micropore on the surface of the coating decrease, the thickness and hardness of the coating increase, both the wear resistance and corrosion resistance of the coating raise.展开更多
Ferritin,as an iron storage protein,has been considered to be a well-utilized iron supplement.However,the typical thermal processing of food rich in ferritin may affect the structure and function of ferritin as an iro...Ferritin,as an iron storage protein,has been considered to be a well-utilized iron supplement.However,the typical thermal processing of food rich in ferritin may affect the structure and function of ferritin as an iron supplement.Here,a plant ferritin(soybean seed ferritin,SSF)and an animal ferritin(donkey spleen ferritin,DSF)were used to analyze the changes in fundamental structure and iron content after thermal treatments(68°C for 30 min,100°C for 10 min).Then,SSF and DSF after thermal treatment were administered intragastrically to mice to further evaluate its digestive stability and absorptivity after thermal processing.Results showed the secondary structure,oligomeric states,iron content,and digestive stability of DSF were maintained better than that of SSF after thermal treatments,indicating that DSF has a higher thermostability than SSF.Both SSF and DSF after thermal treatment exhibited higher absorptivity than untreated ferritins.SSF showed higher absorptivity than DSF whether heated or not.展开更多
The stress aging behavior of Al-Cu alloy under various applied stresses, i.e., elastic stress, yield stress and plasticdeformation stress, was investigated using single crystals. The resulting microstructures and the ...The stress aging behavior of Al-Cu alloy under various applied stresses, i.e., elastic stress, yield stress and plasticdeformation stress, was investigated using single crystals. The resulting microstructures and the yield strength were examined bytransmission electron microscopy (TEM) and compression tests, respectively. The results indicate that an elastic stress of 15 MPa ishigh enough to influence the precipitation distribution of θ′ during aging at 180℃. The applied stress loading along [116]Aldirection results in increased number density of θ′ on (001)Al habit planes. This result becomes more significant with increasingapplied stress and leads to lower yield strength of Al-Cu single crystals during aging. Moreover, the generation of the preferentialorientation of θ′ was discussed by the effect of the dislocation induced by applied stress as well as the role of the misfit between theθ′-precipitate and Al matrix. The results are in agreement with the effect of the latter one.展开更多
Microstructures and phase compositions of as-cast and extruded ZK60-xGd (x=0-4) alloys were investigated. Meanwhile, the tensile mechanical property was tested. With increasing the Gd content, as-cast microstructure...Microstructures and phase compositions of as-cast and extruded ZK60-xGd (x=0-4) alloys were investigated. Meanwhile, the tensile mechanical property was tested. With increasing the Gd content, as-cast microstructure is refined gradually. Mg-Zn-Gd new phase increases gradually, while MgZn2 phase decreases gradually to disappear. The second phase tends to distribute along grain boundary by continuous network. As-cast tensile mechanical property is reduced slightly at ambient temperature when the Gd content does not exceed 2.98%. After extrusion by extrusion ratio of 40 and extrusion temperature of 593 K, microstructure is refined further with decreasing the average grain size to 2 μm for ZK60-2.98Gd alloy. Broken second phase distributes along the extrusion direction by zonal shape. Extruded tensile mechanical property is enhanced significantly. Tensile strength values at 298 and 473 K increase gradually from 355 and 120 MPa for ZK60 alloy to 380 and 164 MPa for ZK60-2.98Gd alloy, respectively. Extruded tensile fractures exhibit a typical character of ductile fracture.展开更多
Antofloxacin free base is prepared from antofloxacin hydrochloride by removing hydrogen chloride. Its crystal is obtained by slow evaporation of an acetonitrile-methanol mixed solution. Single-crystal X-ray diffractio...Antofloxacin free base is prepared from antofloxacin hydrochloride by removing hydrogen chloride. Its crystal is obtained by slow evaporation of an acetonitrile-methanol mixed solution. Single-crystal X-ray diffraction reveals that the crystallography belongs to a triclinic PI space group with cell parameters: a = 0. 663 07(13) nm, b = 0. 898 39(18) nm, c = 1. 569 0(3) nm, α = 75.12(3)°,β = 87.92(3)°, γ = 77.57 (3)°. Antofloxacin shows no fluorescence in solution, but the crystalline state emits strong green light at 510 nm under the excitation of 360 nm, indicating a fluorescence enhancement induced by aggregation. It demonstrates that intermolecular packing and interaction in the crystal lead to the improved fluorescence quantum yield. These results provide important intbrmation for the further exploration of the structure-activity relationship of antofloxacin and the development of new drugs.展开更多
X-ray crystal structures of 2,2',3,3'-and 3, 3',4,4'-biphenyltetracarboxylic dianhydride (2,2',3,3'- and 3,3',4,4'-BPDA) were determined. The dianhydride isomers have different symmetr...X-ray crystal structures of 2,2',3,3'-and 3, 3',4,4'-biphenyltetracarboxylic dianhydride (2,2',3,3'- and 3,3',4,4'-BPDA) were determined. The dianhydride isomers have different symmetry caused by difference in two anhydride group positions and the dihedral angles between the two phenyl rings are 62.9°for 2,2',3,3',-BPDA and 0°for 3,3',4,4'-BPDA respectively. The polyimides from 2,2',3,3'-BPDA exhibit enhanced solubility, higher thermal stability, and higher glasstransition temperature (Tg) compared with those from 3,3',4,4'-BPDA.展开更多
A new improved investment casting technology (IC) has been presented and compared with the existing IC technology such as lost foam casting (LFC). The effect of thermophysical property and coating thickness on cas...A new improved investment casting technology (IC) has been presented and compared with the existing IC technology such as lost foam casting (LFC). The effect of thermophysical property and coating thickness on casting solidification temperature field, microstructure and hardness has been investigated. The results show that the solidification rate decreases inversely with the coating thickness when the coating contains silica sol, zircon powder, mullite powder and defoaming agent. In contrast, the solid cooling rate increases as the coating thickness increases. However, the solidification rate and solid cooling rate of the casting produced by the existing IC and the improved IC are very similar when the coating thickness is 5 mm, so the microstructure and hardness of a container corner fitting produced by the improved IC and the existing IC are similar. The linear regression equation for the grain size (d) and cooling rate (v) of the castings is d= -0.41v+206.1. The linear regression equation for the content of pearlite (w) and solid cooling rate (t) is w=1.79t + 6.71. The new improved IC can greatly simplify the process and decrease the cost of production compared with the existing IC. Contrasting with LI=C, container corner fittings produced by the new improved IC have fewer defects and better properties. It was also found that the desired microstructure and properties can be obtained by changing the thermophysical property and thickness of the coating.展开更多
GF/Pb compositeswerefabricated by the method of powder metallurgy, and the density, microstructure and tensile propertywerecharacterized considering the size and content ofglass fibre (GF). The results show that rel...GF/Pb compositeswerefabricated by the method of powder metallurgy, and the density, microstructure and tensile propertywerecharacterized considering the size and content ofglass fibre (GF). The results show that relative densities decrease with increasing GF fraction, and the 50μm-GF reinforced specimens exhibit a better densification than the 300μm-GF reinforced ones. The GF particles distribute quite uniformly inPb matrix, and the composites fabricated at low sintering temperature (〈200℃) possess fine-grain microstructure. The addition of GF significantly improves the strength of the Pb composites, and the ultimate tensile strength of the Pb composite reinforcedwith the addition of 50μm-0.5% GF(mass fraction)is about 30MPa higher than that of GF-free sample. For all composites groups, increasing the reinforcement content from 0.5%to 2%(mass fraction)results in a decrease in both tensile strength and ductility.展开更多
The effect of micro--phase separation and location of sulfoalkyl pendantgroups on the properties of biomedical segmented polyetherurethanes (SPEU) were studied.Two series of SPEUs containing sulfooctyl pendant groups ...The effect of micro--phase separation and location of sulfoalkyl pendantgroups on the properties of biomedical segmented polyetherurethanes (SPEU) were studied.Two series of SPEUs containing sulfooctyl pendant groups exactly located at the hard segments or sort segments with well defined fine structures were synthesized. The fine structuresof all samples were verified by FTIR,TEM and dynamic mechanical analysis. The anticoagulant properties or such ion - containing SPEUs were improved,and its relationships to thefine structures were discussed.展开更多
The mixed grain structure and mechanical property anisotropy of AZ40 magnesium alloy bar with a diameter of 160 mm manufactured by "multi-direction forging(MDF) + extrusion + online cooling" technique were inves...The mixed grain structure and mechanical property anisotropy of AZ40 magnesium alloy bar with a diameter of 160 mm manufactured by "multi-direction forging(MDF) + extrusion + online cooling" technique were investigated by optical microscopy(OM), scanning electron microscopy(SEM), X-ray diffraction macro-texture measurement and room temperature(RT) tensile test. The results show that mixed grain structure is caused by the micro-segregation of Al in semi-continuous casting ingot. Homogenization of(380 °C, 8 h) +(410 °C, 12 h) cannot totally eliminate such micro-segregation. During MDF and extrusion, the dendrite interiors with 3%-4% Al(mass fraction) transform to fine grain zones, yet the dendrite edges with about 6% Al transform to coarse grain zones. XRD macro-textures of the outer, R/2 and center show typical fiber texture characteristics and the intensity of [0001]//Ra D orientation in the outer(11.245) is about twice as big as those in the R/2(6.026) and center(6.979). The as-extruded AZ40 magnesium alloy bar has high elongation(A) and moderate ultimate tensile strength(Rm) in both extrusion direction(ED) and radius direction(Ra D), i.e., A of 19%-25% and Rm of 256-264 MPa; however, yield strength(Rp0.2) shows anisotropy and heterogeneity, i.e., 103 MPa in Ra D, 137 MPa in ED-C(the center) and 161 MPa in ED-O(the outer), which are mainly caused by the texture.(155 °C, 7 h) +(170 °C, 24 h) aging has no influence on strength and elongation of AZ40 magnesium bar.展开更多
The nominal Ti44Al6Nb1.0Cr2.0V alloy was newly designed and prepared by vacuum consumable melting technique with the ingot sizes of d225 mm×320 mm. The results show that the average lamella colony size is 780-18...The nominal Ti44Al6Nb1.0Cr2.0V alloy was newly designed and prepared by vacuum consumable melting technique with the ingot sizes of d225 mm×320 mm. The results show that the average lamella colony size is 780-1830 μm. This as-cast alloy has a modified near lamellar(M-NL) structure that is composed of mainly larger(α2+γ) lamella colonies and smaller(B2+equiaxed γ) blocky morphology. It exhibits the moderate tensile properties at room temperature, in which the Region(5) yields the ultimate tensile strength(UTS) about 499 MPa and the elongation about 0.53%. The obvious brittle fracture characteristics and trans-granular interlamellar fracture are the predominant modes. After room temperature tensile testing, there are some <101] and a few 1/2<112] superdislocations in the γ phase. The as-cast microcrack is the main factor to deteriorate the tensile property, which results in the premature fracture, poor ductility and few dislocations. The addition of Nb, Cr and V can decrease stacking fault energy(SFE) obviously, which is helpful to enhancing the ductility of the alloy.展开更多
基金Supported by 2023 Jiangxi Provincial Innovation and Entrepreneurship Training Project(202310414021).
文摘China's economic growth and economic development has entered a new stage,and the optimization and upgrading of industrial structure is the core driving force for China to achieve high-quality economic development during the"14 th Five-Year Plan"period.Property tax has a conductive effect on the upgrading of industrial structure.Therefore,from the perspective of property tax and industrial structure adjustment and the relationship between them,this study summarizes the relevant research of domestic and foreign scholars.On the basis of the research,the paper puts forward some relevant policy suggestions on improving China's property tax and promoting the optimization and upgrading of China's industrial structure.
基金Funded by Joint Funds of the National Natural Science Foundation of China(No.U1904188)Jiangxi Provincial Department of Education Science and Technology Project(Nos.GJJ171079,GJJ181023 and GJJ181022)。
文摘Carbonated recycled powder as cementitious auxiliary material can reduce carbon emissions and realize high-quality recycling of recycled concrete.In this paper,microscopic property of recycled powder with three carbonation methods was tested through XRD and SEM,the mechanical property and microstructure of recycled powder mortar with three replacement rates were studied by ISO method and SEM,and the strengthening mechanism was analyzed.The results showed that the mechanical property of recycled powder mortar decreased with the increasing of replacement rate.It is suggested that the replacement rate of recycled powder should not exceed 20%.The strength index and activity index of carbonated recycled powder mortar were improved,in which the flexural strength was increased by 27.85%and compressive strength was increased by 20%at the maximum.Recycled powder can be quickly and completely carbonated,and the improvement effect of CH pre-soaking carbonation was the best.The activity index of carbonated recycled powder can meet the requirements of Grade II technical standard for recycled powder.Microscopic results revealed the activation mechanism of carbonated recycled powder such as surplus calcium source effect,alkaline polycondensation effect and carbonation enhancement effect.
基金Funded by the National Natural Science Foundation of China(No.42102345)the Fundamental Research Funds for the Central Universities(No.2023ZKPYJD03)。
文摘Cryogenic treatment was used to improve the tribological properties of Ti6Al4V artificial hip joint implants.Cryogenic treatment at-196℃with different holding time were carried out on Ti6Al4V specimens fabricated using electron beam melting(EBM),and their microstructure and tribological properties evolution were systematically analyzed by scanning electron microscopy(SEM),vickers hardness,and wear tests.The experimental results show that the as-fabricated specimen consists of lamellarαphase andβcolumnar crystal.While,the thickness of lamellarαphase decreased after cryogenic treatment.In addition,it can be found that the fineαphase was precipitated and dispersed between the lamellarαphase with the holding time increase.Vickers hardness shows a trend of first increasing and then decreasing.The wear rate of the specimen cryogenic treated for 24 h is the minimum and the average friction coefficient is 0.50,which is reduced by 14.61%compared with the as-fabricated.The wear mechanism of the as-fabricated specimen is severe exfoliation,adhesive,abrasive,and slight fatigue wear.However,the specimen cryogenic treated for 24 h shows slight adhesive and abrasive wear.It can be concluded that it is feasibility of utilizing cryogenic treatment to reduce the wear of EBMed Ti6Al4V.
文摘The band structure,DOSs,and optical properties of(Y_(0.75)Ca_(0.25))(Cu_(0.75)Mn_(0.25))SO,including dielectric function,absorption function,reflection function,and energy loss spectrum were studied by using the first-principles calculation.The calculation results indicate that(Y_(0.75)Ca_(0.25))(Cu_(0.75)Mn_(0.25))SO is a direct bandgap semiconductor with a bandgap of 1.1 eV.The Fermi surface is asymmetric and exhibits spin splitting phenomenon.The new type of dilute magnetic semiconductor(Y_(0.75)Ca_(0.25))(Cu_(0.75)Mn_(0.25))SO exhibits significant light loss around 70 eV,with light reflection gradually increasing after 30 eV,and light absorption mainly occurring around 8-30 eV.These results also provide a basis for the discovery of more types of 1111 phase new dilute magnetic semiconductors in the future.
基金Supported by National Natural Science Foundation of China(41771565)Henan Provincial Government Decision-Making Research Bidding Project(2017B189).
文摘In the reform process of the rural land property rights system,the incentive mechanism of the rural land property rights system has a crucial impact on the production activities of rural economic entities.Due to the different rights structures of the property rights system in different social and economic development stages,the land rights and interests enjoyed by rural economic subjects are different,and the degree of incentives for farmers is also different.This difference in incentives affects farmers investment in agricultural production factors,which in turn affects agricultural performance.This paper analyzes the incentive impacts of the structure of rural land property rights on the changes of farmers land rights and agricultural performance since the founding of the People s Republic of China,in order to further deepen the reform of the land system,protect the rights and interests of farmers,promote the modernization of agriculture and rural areas,and explore the realization form and operation mechanism of the rural collective land system in the new era.
基金financially supported by the National Natural Science Foundation of China(Nos.U2141205,52371002,and 52374366)the Fundamental Research Funds for the Central Universities(Nos.06109125 and 06930007)Fundamental Research Funds for the Central Universities(No.FRF-BD-23-02).
文摘Laser powder bed fusion(LPBF)is a widely recognized additive manufacturing technology that can fabricate complex components rapidly through layer-by-layer formation.However,there is a paucity of research on the effect of laser scanning speed on the cellular microstructure and mechanical properties of martensitic stainless steel.This study systematically investigated the influence of laser scanning speed on the cellular microstructure and mechanical properties of a developed Fe11Cr8Ni5Co3Mo martensitic stainless steel produced by LPBF.The results show that increasing the laser scanning speed from 400 to 1000 mm/s does not lead to a noticeable change in the phase fraction,but it reduces the average size of the cellular microstructure from 0.60 to 0.35μm.The scanning speeds of 400 and 1000 mm/s both had adverse effects on performances of sample,resulting in inadequate fusion and keyhole defects respectively.The optimal scanning speed for fabricating samples was determined to be 800 mm/s,which obtained the highest room temperature tensile strength and elongation,with the ultimate tensile strength measured at(1088.3±2.0)MPa and the elongation of(16.76±0.10)%.Furthermore,the mechanism of the evolution of surface morphology,defects,and energy input were clarified,and the relationship between cellular microstructure size and mechanical properties was also established.
基金supported by the National Science Foundation under grant DMR#2320355supported by the Department of Energy,Office of Science,Basic Energy Sciences,under Award#DESC0022305(formulation engineering of energy materials via multiscale learning spirals)Computing resources were provided by the ARCH high-performance computing(HPC)facility,which is supported by National Science Foundation(NSF)grant number OAC 1920103。
文摘Magnesium alloys are emerging as promising alternatives to traditional orthopedic implant materials thanks to their biodegradability,biocompatibility,and impressive mechanical characteristics.However,their rapid in-vivo degradation presents challenges,notably in upholding mechanical integrity over time.This study investigates the impact of high-temperature thermal processing on the mechanical and degradation attributes of a lean Mg-Zn-Ca-Mn alloy,ZX10.Utilizing rapid,cost-efficient characterization methods like X-ray diffraction and optical microscopy,we swiftly examine microstructural changes post-thermal treatment.Employing Pearson correlation coefficient analysis,we unveil the relationship between microstructural properties and critical targets(properties):hardness and corrosion resistance.Additionally,leveraging the least absolute shrinkage and selection operator(LASSO),we pinpoint the dominant microstructural factors among closely correlated variables.Our findings underscore the significant role of grain size refinement in strengthening and the predominance of the ternary Ca_(2)Mg_(6)Zn_(3)phase in corrosion behavior.This suggests that achieving an optimal blend of strength and corrosion resistance is attainable through fine grains and reduced concentration of ternary phases.This thorough investigation furnishes valuable insights into the intricate interplay of processing,structure,and properties in magnesium alloys,thereby advancing the development of superior biodegradable implant materials.
基金financial supports from the National Natural Science Foundation of China (No. 51875062)China Postdoctoral Science Foundation (No. 2021M700567)。
文摘In this study,HEA/AI composite interlayer was used to fabricate Ti/Mg bimetal composites by solidliquid compound casting process.The Al layer was prepared on the surface of TC4 alloy by hot dipping,and the FeCoNiCr HEA layer was prepared by magnetron sputtering onto the Al layer.The influence of the HEA layer thickness and pouring temperature on interface evolution was investigated based on SEM observation and thermodynamic analysis.Results indicate that the sluggish diffusion effect of HEA can effectively inhibit the interfacial diffusion between Al and Mg,which is conducive to the formation of solid solution,especially when the thickness of HEA is 800 nm.With the increase of casting temperature from 720 ℃ to 730 ℃,740℃,and 750 ℃,α-Al(Mg),α-Al(Mg)+Al3Mg2,Al3Mg2+Al12Mg17,and Al12Mg17+δ-Mg are formed at the interface of Ti/Mg bimetal,respectively.When the thickness of the HEA layer is 800 nm and the pouring temperature is 720 ℃,the bonding strength of the Ti/Mg bimetal can reach the maximum of 93.6 MPa.
基金financially supported by the National Key R&D Program of China (No.2021YFA1200203)the National Natural Science Foundation of China (Nos.51922026 and 51975111)+1 种基金the Fundamental Research Funds for the Central Universities (No.N2202015,N2002005,and N2105001)the 111 Project of China (No.BP0719037 and B20029)。
文摘Face-centered cubic (f.c.c.) high entropy alloys (HEAs) are attracting more and more attention owing to their excellent strength and ductility synergy, irradiation resistance, etc. However, the yield strength of f.c.c. HEAs is generally low, significantly limiting their practical applications. Recently, the alloying of W has been evidenced to be able to remarkably improve the mechanical properties of f.c.c. HEAs and is becoming a hot topic in the community of HEAs. To date, when W is introduced, multiple strengthening mechanisms, including solid-solution strengthening, precipitation strengthening (μphase,σphase, and b.c.c. phase), and grain-refinement strengthening, have been discovered to be activated or enhanced. Apart from mechanical properties, the addition of W improves corrosion resistance as W helps to form a dense WO_(3) film on the alloy surface. Until now, despite the extensive studies in the literature, there is no available review paper focusing on the W doping of the f.c.c. HEAs. In that context, the effects of W doping on f.c.c. HEAs were reviewed in this work from three aspects, i.e., microstructure,mechanical property, and corrosion resistance. We expect this work can advance the application of the W alloying strategy in the f.c.c. HEAs.
基金Project(12504230006) supported by the Priority Academic Program Development of Jiangsu Higher Education Institutions,China
文摘Ceramic coating incorporated with nano-SiC was obtained on AZ91D magnesium alloy during MAO by adding nano-SiC into the silicate-aluminate-based composite electrolyte. The microstructure, thickness, phase analysis, element composition and hardness of the coatings were respectively investigated by scanning electron microscopy(SEM), film thickness meter, X-ray diffraction (XRD), energy disperse spectroscopy(EDS) and Vickers hardness tester. The wear resistance of Mg alloy and coatings were evaluated by friction and wear apparatus, while the corrosion resistance of Mg alloy and coatings were evaluated by potentiodynamic polarization test and electrochemical impedance spectroscopy (EIS). The results show that after adding nano-SiC into the electrolyte, both the striking voltage and final voltage decrease, the size and number of the micropore on the surface of the coating decrease, the thickness and hardness of the coating increase, both the wear resistance and corrosion resistance of the coating raise.
基金funded by National Natural Science Foundation of China(No.31730069).
文摘Ferritin,as an iron storage protein,has been considered to be a well-utilized iron supplement.However,the typical thermal processing of food rich in ferritin may affect the structure and function of ferritin as an iron supplement.Here,a plant ferritin(soybean seed ferritin,SSF)and an animal ferritin(donkey spleen ferritin,DSF)were used to analyze the changes in fundamental structure and iron content after thermal treatments(68°C for 30 min,100°C for 10 min).Then,SSF and DSF after thermal treatment were administered intragastrically to mice to further evaluate its digestive stability and absorptivity after thermal processing.Results showed the secondary structure,oligomeric states,iron content,and digestive stability of DSF were maintained better than that of SSF after thermal treatments,indicating that DSF has a higher thermostability than SSF.Both SSF and DSF after thermal treatment exhibited higher absorptivity than untreated ferritins.SSF showed higher absorptivity than DSF whether heated or not.
基金Project(51375503)supported by the National Natural Science Foundation of China
文摘The stress aging behavior of Al-Cu alloy under various applied stresses, i.e., elastic stress, yield stress and plasticdeformation stress, was investigated using single crystals. The resulting microstructures and the yield strength were examined bytransmission electron microscopy (TEM) and compression tests, respectively. The results indicate that an elastic stress of 15 MPa ishigh enough to influence the precipitation distribution of θ′ during aging at 180℃. The applied stress loading along [116]Aldirection results in increased number density of θ′ on (001)Al habit planes. This result becomes more significant with increasingapplied stress and leads to lower yield strength of Al-Cu single crystals during aging. Moreover, the generation of the preferentialorientation of θ′ was discussed by the effect of the dislocation induced by applied stress as well as the role of the misfit between theθ′-precipitate and Al matrix. The results are in agreement with the effect of the latter one.
基金Projects(2010A090200078,2011A080403008)supported by the Major Science and Technology Project of Guangdong Province,China
文摘Microstructures and phase compositions of as-cast and extruded ZK60-xGd (x=0-4) alloys were investigated. Meanwhile, the tensile mechanical property was tested. With increasing the Gd content, as-cast microstructure is refined gradually. Mg-Zn-Gd new phase increases gradually, while MgZn2 phase decreases gradually to disappear. The second phase tends to distribute along grain boundary by continuous network. As-cast tensile mechanical property is reduced slightly at ambient temperature when the Gd content does not exceed 2.98%. After extrusion by extrusion ratio of 40 and extrusion temperature of 593 K, microstructure is refined further with decreasing the average grain size to 2 μm for ZK60-2.98Gd alloy. Broken second phase distributes along the extrusion direction by zonal shape. Extruded tensile mechanical property is enhanced significantly. Tensile strength values at 298 and 473 K increase gradually from 355 and 120 MPa for ZK60 alloy to 380 and 164 MPa for ZK60-2.98Gd alloy, respectively. Extruded tensile fractures exhibit a typical character of ductile fracture.
文摘Antofloxacin free base is prepared from antofloxacin hydrochloride by removing hydrogen chloride. Its crystal is obtained by slow evaporation of an acetonitrile-methanol mixed solution. Single-crystal X-ray diffraction reveals that the crystallography belongs to a triclinic PI space group with cell parameters: a = 0. 663 07(13) nm, b = 0. 898 39(18) nm, c = 1. 569 0(3) nm, α = 75.12(3)°,β = 87.92(3)°, γ = 77.57 (3)°. Antofloxacin shows no fluorescence in solution, but the crystalline state emits strong green light at 510 nm under the excitation of 360 nm, indicating a fluorescence enhancement induced by aggregation. It demonstrates that intermolecular packing and interaction in the crystal lead to the improved fluorescence quantum yield. These results provide important intbrmation for the further exploration of the structure-activity relationship of antofloxacin and the development of new drugs.
文摘X-ray crystal structures of 2,2',3,3'-and 3, 3',4,4'-biphenyltetracarboxylic dianhydride (2,2',3,3'- and 3,3',4,4'-BPDA) were determined. The dianhydride isomers have different symmetry caused by difference in two anhydride group positions and the dihedral angles between the two phenyl rings are 62.9°for 2,2',3,3',-BPDA and 0°for 3,3',4,4'-BPDA respectively. The polyimides from 2,2',3,3'-BPDA exhibit enhanced solubility, higher thermal stability, and higher glasstransition temperature (Tg) compared with those from 3,3',4,4'-BPDA.
文摘A new improved investment casting technology (IC) has been presented and compared with the existing IC technology such as lost foam casting (LFC). The effect of thermophysical property and coating thickness on casting solidification temperature field, microstructure and hardness has been investigated. The results show that the solidification rate decreases inversely with the coating thickness when the coating contains silica sol, zircon powder, mullite powder and defoaming agent. In contrast, the solid cooling rate increases as the coating thickness increases. However, the solidification rate and solid cooling rate of the casting produced by the existing IC and the improved IC are very similar when the coating thickness is 5 mm, so the microstructure and hardness of a container corner fitting produced by the improved IC and the existing IC are similar. The linear regression equation for the grain size (d) and cooling rate (v) of the castings is d= -0.41v+206.1. The linear regression equation for the content of pearlite (w) and solid cooling rate (t) is w=1.79t + 6.71. The new improved IC can greatly simplify the process and decrease the cost of production compared with the existing IC. Contrasting with LI=C, container corner fittings produced by the new improved IC have fewer defects and better properties. It was also found that the desired microstructure and properties can be obtained by changing the thermophysical property and thickness of the coating.
文摘GF/Pb compositeswerefabricated by the method of powder metallurgy, and the density, microstructure and tensile propertywerecharacterized considering the size and content ofglass fibre (GF). The results show that relative densities decrease with increasing GF fraction, and the 50μm-GF reinforced specimens exhibit a better densification than the 300μm-GF reinforced ones. The GF particles distribute quite uniformly inPb matrix, and the composites fabricated at low sintering temperature (〈200℃) possess fine-grain microstructure. The addition of GF significantly improves the strength of the Pb composites, and the ultimate tensile strength of the Pb composite reinforcedwith the addition of 50μm-0.5% GF(mass fraction)is about 30MPa higher than that of GF-free sample. For all composites groups, increasing the reinforcement content from 0.5%to 2%(mass fraction)results in a decrease in both tensile strength and ductility.
文摘The effect of micro--phase separation and location of sulfoalkyl pendantgroups on the properties of biomedical segmented polyetherurethanes (SPEU) were studied.Two series of SPEUs containing sulfooctyl pendant groups exactly located at the hard segments or sort segments with well defined fine structures were synthesized. The fine structuresof all samples were verified by FTIR,TEM and dynamic mechanical analysis. The anticoagulant properties or such ion - containing SPEUs were improved,and its relationships to thefine structures were discussed.
基金Project(2013CB632202)supported by the National Basic Research Program of China
文摘The mixed grain structure and mechanical property anisotropy of AZ40 magnesium alloy bar with a diameter of 160 mm manufactured by "multi-direction forging(MDF) + extrusion + online cooling" technique were investigated by optical microscopy(OM), scanning electron microscopy(SEM), X-ray diffraction macro-texture measurement and room temperature(RT) tensile test. The results show that mixed grain structure is caused by the micro-segregation of Al in semi-continuous casting ingot. Homogenization of(380 °C, 8 h) +(410 °C, 12 h) cannot totally eliminate such micro-segregation. During MDF and extrusion, the dendrite interiors with 3%-4% Al(mass fraction) transform to fine grain zones, yet the dendrite edges with about 6% Al transform to coarse grain zones. XRD macro-textures of the outer, R/2 and center show typical fiber texture characteristics and the intensity of [0001]//Ra D orientation in the outer(11.245) is about twice as big as those in the R/2(6.026) and center(6.979). The as-extruded AZ40 magnesium alloy bar has high elongation(A) and moderate ultimate tensile strength(Rm) in both extrusion direction(ED) and radius direction(Ra D), i.e., A of 19%-25% and Rm of 256-264 MPa; however, yield strength(Rp0.2) shows anisotropy and heterogeneity, i.e., 103 MPa in Ra D, 137 MPa in ED-C(the center) and 161 MPa in ED-O(the outer), which are mainly caused by the texture.(155 °C, 7 h) +(170 °C, 24 h) aging has no influence on strength and elongation of AZ40 magnesium bar.
基金Project(2011CB605504)supported by the National Basic Research Program of ChinaProject(NCET-12-0153)supported by the Program of New Century Excellent Talents in UniversityProject(51274076)supported by the National Natural Science Foundation of China
文摘The nominal Ti44Al6Nb1.0Cr2.0V alloy was newly designed and prepared by vacuum consumable melting technique with the ingot sizes of d225 mm×320 mm. The results show that the average lamella colony size is 780-1830 μm. This as-cast alloy has a modified near lamellar(M-NL) structure that is composed of mainly larger(α2+γ) lamella colonies and smaller(B2+equiaxed γ) blocky morphology. It exhibits the moderate tensile properties at room temperature, in which the Region(5) yields the ultimate tensile strength(UTS) about 499 MPa and the elongation about 0.53%. The obvious brittle fracture characteristics and trans-granular interlamellar fracture are the predominant modes. After room temperature tensile testing, there are some <101] and a few 1/2<112] superdislocations in the γ phase. The as-cast microcrack is the main factor to deteriorate the tensile property, which results in the premature fracture, poor ductility and few dislocations. The addition of Nb, Cr and V can decrease stacking fault energy(SFE) obviously, which is helpful to enhancing the ductility of the alloy.