Precision medicine has become a cornerstone in modern therapeutic strategies, with nucleic acid aptamers emerging aspivotal tools due to their unique properties. These oligonucleotide fragments, selected through the S...Precision medicine has become a cornerstone in modern therapeutic strategies, with nucleic acid aptamers emerging aspivotal tools due to their unique properties. These oligonucleotide fragments, selected through the Systematic Evolution ofLigands by Exponential Enrichment process, exhibit high affinity and specificity toward their targets, such as DNA, RNA,proteins, and other biomolecules. Nucleic acid aptamers offer significant advantages over traditional therapeutic agents,including superior biological stability, minimal immunogenicity, and the capacity for universal chemical modifications thatenhance their in vivo performance and targeting precision. In the realm of osseous tissue repair and regeneration, a complexphysiological process essential for maintaining skeletal integrity, aptamers have shown remarkable potential in influencingmolecular pathways crucial for bone regeneration, promoting osteogenic differentiation and supporting osteoblast survival. Byengineering aptamers to regulate inflammatory responses and facilitate the proliferation and differentiation of fibroblasts,these oligonucleotides can be integrated into advanced drug delivery systems, significantly improving bone repair efficacywhile minimizing adverse effects. Aptamer-mediated strategies, including the use of siRNA and miRNA mimics or inhibitors,have shown efficacy in enhancing bone mass and microstructure. These approaches hold transformative potential for treatinga range of orthopedic conditions like osteoporosis, osteosarcoma, and osteoarthritis. This review synthesizes the molecularmechanisms and biological roles of aptamers in orthopedic diseases, emphasizing their potential to drive innovative andeffective therapeutic interventions.展开更多
Catalytic oxidation of biomass-derived 5-hydroxymethylfurfural(HMF)to 2,5-furandicarboxylic acid(FDCA,an alternative bioplastic monomer to petroleum-derived terephthalic acid),has been identified as an important bioma...Catalytic oxidation of biomass-derived 5-hydroxymethylfurfural(HMF)to 2,5-furandicarboxylic acid(FDCA,an alternative bioplastic monomer to petroleum-derived terephthalic acid),has been identified as an important biomass conversion reaction in bio-based polyester industry.However,it is still challenging to acquire a high FDCA yield from the selective oxidation of HMF at low temperatures.Herein,a ternary metal-based catalyst was prepared by loading AuPdPt noble metal nanoparticles on the oxygen-rich vacancy titanium dioxide layer deposited on natural clay mineral halloysite nanotubes(HNTs),and the catalytic activity was examined for air-oxidation of HMF to FDCA in water at ambient temperature(30℃).By adjusting the Au/Pd/Pt ratio,a 93.6%FDCA yield was achieved with the optimal Au_(0.5)Pd_(0.2)Pt_(0.3)/TiO_(2)@HNTs catalyst,which revealed an impressive FDCA formation rate of 67.58 mmol g^(-1)h^(-1)and an excellent TOF value of 17.54 h^(-1)under normal air pressure at 30℃,surpassing the performance of mono-and bimetallic-based catalysts.Theoretical calculation and catalytic performance study clarified the structure-activity relationship.It was found that the ternary metal and oxygen vacancies revealing synergistic enhancement of ambient temperature catalyzed HMF air-oxidation via electronic structure tuning and adsorption intensification.DFT and kinetics study demonstrated that the presence of ternary metal significantly improved the adsorption capacity of substrate and enhanced the rate-determining step of the key intermediate 5-hydroxymethyl-2-furanocarboxylic acid(HMFCA)oxidation when compared to mono-and bimetal.Additionally,the TiO_(2)@HNTs support with high oxygen vacancy concentration facilitated the adsorption of oxygen,synergistically working with the ternary metal to activate and low the energy barriers for the generation of superoxide radical,thus enhancing the FDCA formation.This work offers a novel strategy for designing ternary metal-based catalysts for low-energy catalytic oxidation reactions.展开更多
To clarify the densification behavior,deformation response and strengthening mechanisms of selective laser melted(SLM)Mg-RE alloys,this study systematically investigates a representative WE43 alloy via advanced materi...To clarify the densification behavior,deformation response and strengthening mechanisms of selective laser melted(SLM)Mg-RE alloys,this study systematically investigates a representative WE43 alloy via advanced material characterization techniques.A suitable laser output mode fell into the transition mode,allowing for the fabrication of nearly full-density samples(porosity=0.85±0.021%)with favorable mechanical properties(yield strength=351 MPa,ultimate tensile strength=417 MPa,the elongation at break=6.5%and microhardness=137.9±6.15 HV_(0.1))using optimal processing parameters(P=80 W,v=250 mm/s and d=50μm).Viscoplastic self-consistent analysis and transmission electron microscopy observations reveal that the plastic deformation response of the SLM Mg-RE alloys is primarily driven by basal and prismatic slips.Starting from a random texture before deformation(maximum multiple of ultimate density,Max.MUD=3.95),plastic stretching led the grains to align with the Z-axis,finally resulting in a{0001}<1010>texture orientation after fracture(Max.MUD=8.755).Main phases of the SLM state are mainly composed ofα-Mg,Mg_(24)Y_(5) andβ'-Mg_(41)Nd_(5),with an average grain size of only 4.27μm(about a quarter of that in the extruded state),resulting in a favorable strength-toughness ratio.Except for the nano-β'phase and semi-coherent Mg_(24)Y_(5) phase(mismatch=16.12%)around the grain boundaries,a small amount of nano-ZrO_(2) and Y_(2)O_(3) particles also play a role in dispersion strengthening.The high mechanical properties of the SLM state are chiefly attributed to precipitation hardening(44.41%),solid solution strengthening(34.06%)and grain boundary strengthening(21.53%),with precipitation hardening being predominantly driven by dislocation strengthening(67.77%).High-performance SLM Mg-RE alloy components were manufactured and showcased at TCT Asia 2024,receiving favorable attention.This work underscores the significant application potential of SLM Mg-RE alloys and establishes a strong foundation for advancing their use in the biomedical fields.展开更多
Selective laser melting(SLM)has attracted great attention in the fabrication of magnesium-based biodegradable implants.However,current SLMed magnesium alloys are generally suffered from rapid corrosion,which is deadly...Selective laser melting(SLM)has attracted great attention in the fabrication of magnesium-based biodegradable implants.However,current SLMed magnesium alloys are generally suffered from rapid corrosion,which is deadly detrimental to their use.Herein,we thoroughly revealed why they are so vulnerable to corrosion through a typical SLMed AZ91D material model.An abnormally spatiotemporal“bulk erosion”mechanism was found,not the well-known“surface corrosion”mode of traditionally plastic-deformed alloys.The unique microstructure derived from SLM possesses high chemical reactivity,which is favorable for interactional attacks of fast fluid penetration,severe local corrosion and intensive micro-galvanic corrosion.Thus,it brings two orders of magnitude in corrosion rates compared with its plastic-deformed counterparts.In vitro,such fast-corrosion induced apparent cytotoxicity,cell damage,and further apoptosis to rat and mouse derived mesenchymal stem cells.In vivo,the material disintegrates into small pieces in a short period,and results in unexpected bone destruction and long-lasting foreign body reactions in Sprague Dawley rats.Close attention should be paid to this issue before SLMed Mg-based implants being applied in patients.展开更多
High entropy alloys(HEAs) are of great interest in the community of materials science and engineering due to their unique phase structure. They are constructed with five or more principal alloying elements in equimola...High entropy alloys(HEAs) are of great interest in the community of materials science and engineering due to their unique phase structure. They are constructed with five or more principal alloying elements in equimolar or near-equimolar ratio. Therefore, HEAs can derive their performance from multiple principal elements rather than a single element. In this work, solid-state cold spraying(CS) was applied for the first time to produce FeCoNiCrMn HEA coating. The experimental results confirm that CS can be used to produce a thick HEA coating with low porosity. As a low-temperature deposition process, CS completely retained the HEA phase structure in the coating without any phase transformation. The characterization also reveals that the grains in the CSed HEA coating had experienced significant refinement as compared to those in the as-received HEA powder due the occurrence of dynamic recrystallization at the highly deformed interparticle region. Due to the increased dislocation density and grain boundaries,CSed HEA coating was much harder than the as-received powder. The tribological study shows that the CSed FeCoNiCrMn HEA coating resulted in lower wear rate than laser cladded HEA coatings.展开更多
In the present work,selective laser melting(SLM)technology was utilized for manufacturing CX stainless steel samples under a series of laser parameters.The effect of laser linear energy density on the microstructure c...In the present work,selective laser melting(SLM)technology was utilized for manufacturing CX stainless steel samples under a series of laser parameters.The effect of laser linear energy density on the microstructure characteristics,phase distribution,crystallographic orientation and mechanical properties of these CX stainless steel samples were investigated theoretically and experimentally via scanning electron microscope(SEM),X-ray diffraction(XRD),electron backscatter diffraction(EBSD)and transmission electron microscope(TEM).Based on the systematic study,the SLM CX stainless steel sample with best surface roughness(Ra=4.05±1.8μm)and relative density(Rd=99.72%±0.22%)under the optimal linear density(η=245 J/m)can be obtained.SLM CX stainless steel was primarily constituted by a large number of fine martensite(α’phase)structures(i.e.,cell structures,cellular dendrites and blocky grains)and a small quantity of austenite(γphase)structures.The pre ferred crystallographic orientation(i.e.,<111>direction)can be determined in the XZ plane of the SLM CX sample.Furthermore,under the optimal linear energy density,the good combinations with the highest ultimate tensile strength(UTS=1068.0%±5.9%)and the best total elongation(TE=15.70%±0.26%)of the SLM CX sample can be attained.Dislocation strengthening dominates the strengthening mechanism of the SLM CX sample in as-built state.展开更多
Fabrication of the Mg–9Al–1Zn–0.5Mn alloy with excellent mechanical performance using selective laser melting(SLM)technology is quite difficult owing to the poor weldability and low boiling point.To address these ch...Fabrication of the Mg–9Al–1Zn–0.5Mn alloy with excellent mechanical performance using selective laser melting(SLM)technology is quite difficult owing to the poor weldability and low boiling point.To address these challenges and seek the optimal processing parameters,response surface methodology was systematically utilized to determine the appropriate SLM parameter combinations.Mg–9Al–1Zn–0.5Mn sample with high relative density(99.5±0.28%)and favorable mechanical properties(microhardness=95.6±5.28 HV_(0.1),UTS=370.2 MPa,and At=10.4%)was achieved using optimized SLM parameters(P=120 W,v=500 mm/s,and h=45μm).Sample is dominated by a random texture and microstructure is primarily constituted by quantities offine equiaxed grains(α-Mg phase),a small amount ofβ-Al_(12)Mg_(17) structures(4.96 vol%,including spherical:[2110]_(α)//[111]_(β)and long lath-like:[2110]_(α)//[115]_(β)or[1011]_(α)//[321]_(β)),and some short rod-shaped Al8Mn5 nanoparticles.Benefiting from grain boundary strengthening,solid solution strengthening,and precipitation hardening of various nanoparticles(β-Al12Mg17 and Al8Mn5),high-performance Mg–9Al–1Zn–0.5Mn alloy biomedical implants can be fabricated.Precipitation hardening dominates the strengthening mechanism of the SLM Mg–9Al–1Zn–0.5Mn alloy.展开更多
This work focuses on the structure and magnetic properties of Fe-50wt% Ni permalloy manufactured from the pre-alloyed powder by selective laser melting (SLM). The selective laser melted (SLMed) alloys were characteriz...This work focuses on the structure and magnetic properties of Fe-50wt% Ni permalloy manufactured from the pre-alloyed powder by selective laser melting (SLM). The selective laser melted (SLMed) alloys were characterized by a 3D profilometer,optical microscope, scanning electron microscope, X-ray diffraction, etc. The effects of the volume energy density of laser(LVED) on structure, and magnetic properties with coercivity ( H), remanence ( B), and power losses ( P), were evaluated and discussed systematically. The results show that the relative porosity rate and the surface roughness of the SLMed specimens decreased with the increase in LVED. Only the γ-(FeNi) phase was detected in the X-ray diffraction patterns of the SLMed permalloys fabricated from the different LVEDs. Statistical analysis of optical microscopy images indicated that the grain coarsened at higher LVED. Furthermore, the microstructure of the SLMed parts was a typical columnar structure with an oriented growth of building direction. The highest microhardness reached 198 HV. Besides, the magnetic properties including B, H, and Pof SLMed samples decreased when the LVED ranged from 33.3 to 60.0 J/mm ~3 firstly and then increased while LVED further up to 93.3 J/mm, which is related to the decrease in porosity and the increase in grain size, while the higher residual stress and microcracks presented in the samples manufactured using very high LVED. The observed evolution of magnetic properties and LVED provides a good compromise in terms of reduced porosity and crack formation for the fabrication of SLMed Fe-50 wt% Ni permalloy. The theoretical mechanism in this study can offer guidance to further investigate SLMed soft magnetic alloys.展开更多
In the context of the COVID-19 epidemic,a"double-hazard scenario"consisting of a natural disaster and a public health event simultaneously accurring is more likely to arise.However,compared with single-hazar...In the context of the COVID-19 epidemic,a"double-hazard scenario"consisting of a natural disaster and a public health event simultaneously accurring is more likely to arise.However,compared with single-hazard,multiple disasters confront the challenges of complexity,diversity,and demand urgency.To improve the efficiency of emergency material distribution under multiple disasters,this study first divided multiple disasters into three categoriles:independent scenario,sequential scenario,and coupling scenario.A set of evaluation index systems for multiple disasters was established to quantify the urgency of demand.The routing optimization model of emergency vehicles for multiple disasters was proposed by combining demand urgency and road damage,and the non-dominated sorting genetic algorithm II(NSGA-I)was used to simulate and validate the model.A coupling scenario considering two typical disasters of hurricanes and epidemics was selected as a validation example,and sensitivity analysis was also performed for different algorithms,scenarios,and constraints.The results demonstrated that the proposed model could effectively address the vehicle routing problem of emer-gency materials in the context of multiple disasters.Compared to the NSGA,the NSGA-II was used to reduce the total delivery time,cost,and penalty cost by 15.98%6,13.60%,and 16.14%,respectively.Compared with the independent scenario,the coupling scenario increased the total delivery time and cost by 186.28%and 132.48%during the epidemic.However,it reduced the total delivery time by 4.00%and increased the delivery cost by 23.55%compared with the hurricane.Compared with the model without consideration,the model considering demand urgency and road damage reduced the total delivery time and cost by 17.88%and 8.73%,respectively.The model constructed in this study addressed the vehicle routing problem considering the demand urgency and road damage in the optimization process,particularly in the context of multiple disasters.展开更多
基金Key research and development projects of Sichuan Science and Technology Plan Project(2024YFFK0135)Fujian Provincial Natural Science Foundation of China(2024J011450).
文摘Precision medicine has become a cornerstone in modern therapeutic strategies, with nucleic acid aptamers emerging aspivotal tools due to their unique properties. These oligonucleotide fragments, selected through the Systematic Evolution ofLigands by Exponential Enrichment process, exhibit high affinity and specificity toward their targets, such as DNA, RNA,proteins, and other biomolecules. Nucleic acid aptamers offer significant advantages over traditional therapeutic agents,including superior biological stability, minimal immunogenicity, and the capacity for universal chemical modifications thatenhance their in vivo performance and targeting precision. In the realm of osseous tissue repair and regeneration, a complexphysiological process essential for maintaining skeletal integrity, aptamers have shown remarkable potential in influencingmolecular pathways crucial for bone regeneration, promoting osteogenic differentiation and supporting osteoblast survival. Byengineering aptamers to regulate inflammatory responses and facilitate the proliferation and differentiation of fibroblasts,these oligonucleotides can be integrated into advanced drug delivery systems, significantly improving bone repair efficacywhile minimizing adverse effects. Aptamer-mediated strategies, including the use of siRNA and miRNA mimics or inhibitors,have shown efficacy in enhancing bone mass and microstructure. These approaches hold transformative potential for treatinga range of orthopedic conditions like osteoporosis, osteosarcoma, and osteoarthritis. This review synthesizes the molecularmechanisms and biological roles of aptamers in orthopedic diseases, emphasizing their potential to drive innovative andeffective therapeutic interventions.
基金supported by the National Natural Science Foundation of China(22478167,22278419)the College Students Innovative Practice Plan of Jiangsu University(202410299160Y)+2 种基金the Youth Talent Cultivation Plan of Jiangsu Universitythe Key Core Technology Research(Social Development)Foundation of Suzhou(2023ss06)Collaborative Innovation Center for Water Treatment Technology and Materials and the Special Fund of Henan Key Laboratory of Water Pollution Control and Rehabilitation Technology(CJSZ2024010).
文摘Catalytic oxidation of biomass-derived 5-hydroxymethylfurfural(HMF)to 2,5-furandicarboxylic acid(FDCA,an alternative bioplastic monomer to petroleum-derived terephthalic acid),has been identified as an important biomass conversion reaction in bio-based polyester industry.However,it is still challenging to acquire a high FDCA yield from the selective oxidation of HMF at low temperatures.Herein,a ternary metal-based catalyst was prepared by loading AuPdPt noble metal nanoparticles on the oxygen-rich vacancy titanium dioxide layer deposited on natural clay mineral halloysite nanotubes(HNTs),and the catalytic activity was examined for air-oxidation of HMF to FDCA in water at ambient temperature(30℃).By adjusting the Au/Pd/Pt ratio,a 93.6%FDCA yield was achieved with the optimal Au_(0.5)Pd_(0.2)Pt_(0.3)/TiO_(2)@HNTs catalyst,which revealed an impressive FDCA formation rate of 67.58 mmol g^(-1)h^(-1)and an excellent TOF value of 17.54 h^(-1)under normal air pressure at 30℃,surpassing the performance of mono-and bimetallic-based catalysts.Theoretical calculation and catalytic performance study clarified the structure-activity relationship.It was found that the ternary metal and oxygen vacancies revealing synergistic enhancement of ambient temperature catalyzed HMF air-oxidation via electronic structure tuning and adsorption intensification.DFT and kinetics study demonstrated that the presence of ternary metal significantly improved the adsorption capacity of substrate and enhanced the rate-determining step of the key intermediate 5-hydroxymethyl-2-furanocarboxylic acid(HMFCA)oxidation when compared to mono-and bimetal.Additionally,the TiO_(2)@HNTs support with high oxygen vacancy concentration facilitated the adsorption of oxygen,synergistically working with the ternary metal to activate and low the energy barriers for the generation of superoxide radical,thus enhancing the FDCA formation.This work offers a novel strategy for designing ternary metal-based catalysts for low-energy catalytic oxidation reactions.
基金supported by the National Key Research and Development Program of China(No.2022YFC2406000)the Guangdong Basic and Applied Basic Research Foundation(2024A1515011024)+5 种基金the Guangzhou Science and Technology Project(2024A04J4943)the Guangdong Academy of Sciences Development Special Fund Project(2022GDASZH-2022010107)the Guangdong province Science and Technology Plan Projects(2023B1212120008,2023B1212060045)the GDAS Projects of International cooperation platform of Science and Technology(2022GDASZH-2022010203-003)Special Support Foundation of Guangdong Province(2023TQ07Z559)Shenzhen Basic Research Project(JCYJ20210324120001003 and JCYJ20220531091802006)。
文摘To clarify the densification behavior,deformation response and strengthening mechanisms of selective laser melted(SLM)Mg-RE alloys,this study systematically investigates a representative WE43 alloy via advanced material characterization techniques.A suitable laser output mode fell into the transition mode,allowing for the fabrication of nearly full-density samples(porosity=0.85±0.021%)with favorable mechanical properties(yield strength=351 MPa,ultimate tensile strength=417 MPa,the elongation at break=6.5%and microhardness=137.9±6.15 HV_(0.1))using optimal processing parameters(P=80 W,v=250 mm/s and d=50μm).Viscoplastic self-consistent analysis and transmission electron microscopy observations reveal that the plastic deformation response of the SLM Mg-RE alloys is primarily driven by basal and prismatic slips.Starting from a random texture before deformation(maximum multiple of ultimate density,Max.MUD=3.95),plastic stretching led the grains to align with the Z-axis,finally resulting in a{0001}<1010>texture orientation after fracture(Max.MUD=8.755).Main phases of the SLM state are mainly composed ofα-Mg,Mg_(24)Y_(5) andβ'-Mg_(41)Nd_(5),with an average grain size of only 4.27μm(about a quarter of that in the extruded state),resulting in a favorable strength-toughness ratio.Except for the nano-β'phase and semi-coherent Mg_(24)Y_(5) phase(mismatch=16.12%)around the grain boundaries,a small amount of nano-ZrO_(2) and Y_(2)O_(3) particles also play a role in dispersion strengthening.The high mechanical properties of the SLM state are chiefly attributed to precipitation hardening(44.41%),solid solution strengthening(34.06%)and grain boundary strengthening(21.53%),with precipitation hardening being predominantly driven by dislocation strengthening(67.77%).High-performance SLM Mg-RE alloy components were manufactured and showcased at TCT Asia 2024,receiving favorable attention.This work underscores the significant application potential of SLM Mg-RE alloys and establishes a strong foundation for advancing their use in the biomedical fields.
基金supported by the National Natural Science Foundation of China(Nos.52101283 and U22A20121)the National Key R&D Program of China(Nos.2021YFC2400700 and 2022YFC2406000)+6 种基金the Science and Technology Planning Project of Guangzhou(No.202201011454)the NSFC Incubation Program of GDPH(No.KY012021165)the High-level Hospital Construction Project(No.KJ012019520)the Special Fund Project of Guangdong Academy of Sciences(Nos.2022GDASZH-2022010107 and 2021GDASYL-20210102005)the GDAS Projects of International Cooperation Platform of Science and Technology(No.2022GDASZH-2022010203-003)the Guangdong Basic and Applied Basic Research Foundation(No.2022B1515250004)the Young Elite Scientist Sponsorship Program by China Association for Science and Technology(CAST)(No.YESS20210269).
文摘Selective laser melting(SLM)has attracted great attention in the fabrication of magnesium-based biodegradable implants.However,current SLMed magnesium alloys are generally suffered from rapid corrosion,which is deadly detrimental to their use.Herein,we thoroughly revealed why they are so vulnerable to corrosion through a typical SLMed AZ91D material model.An abnormally spatiotemporal“bulk erosion”mechanism was found,not the well-known“surface corrosion”mode of traditionally plastic-deformed alloys.The unique microstructure derived from SLM possesses high chemical reactivity,which is favorable for interactional attacks of fast fluid penetration,severe local corrosion and intensive micro-galvanic corrosion.Thus,it brings two orders of magnitude in corrosion rates compared with its plastic-deformed counterparts.In vitro,such fast-corrosion induced apparent cytotoxicity,cell damage,and further apoptosis to rat and mouse derived mesenchymal stem cells.In vivo,the material disintegrates into small pieces in a short period,and results in unexpected bone destruction and long-lasting foreign body reactions in Sprague Dawley rats.Close attention should be paid to this issue before SLMed Mg-based implants being applied in patients.
基金the financial support from Irish Research Council Project(GOIPD-2017-912)European Space Agency(4000112844/14/NL/FE)
文摘High entropy alloys(HEAs) are of great interest in the community of materials science and engineering due to their unique phase structure. They are constructed with five or more principal alloying elements in equimolar or near-equimolar ratio. Therefore, HEAs can derive their performance from multiple principal elements rather than a single element. In this work, solid-state cold spraying(CS) was applied for the first time to produce FeCoNiCrMn HEA coating. The experimental results confirm that CS can be used to produce a thick HEA coating with low porosity. As a low-temperature deposition process, CS completely retained the HEA phase structure in the coating without any phase transformation. The characterization also reveals that the grains in the CSed HEA coating had experienced significant refinement as compared to those in the as-received HEA powder due the occurrence of dynamic recrystallization at the highly deformed interparticle region. Due to the increased dislocation density and grain boundaries,CSed HEA coating was much harder than the as-received powder. The tribological study shows that the CSed FeCoNiCrMn HEA coating resulted in lower wear rate than laser cladded HEA coatings.
基金supported financially by the Sciences Platform Environment and Capacity Building Projects of GDAS(No.2019GDASYL-0502006)the Key R&D Program of Guangdong Province(No.2020B090923002)+3 种基金the Guangdong Academy of Science Projects(No.2021GDASYL-20210102005)the Guangdong Province Science and Technology Plan Projects(No.2020A1515011096)the Guangzhou Project of Science&Technology(Nos.202007020008 and 201807010030)the support from the Program of CSC(No.201801810106)。
文摘In the present work,selective laser melting(SLM)technology was utilized for manufacturing CX stainless steel samples under a series of laser parameters.The effect of laser linear energy density on the microstructure characteristics,phase distribution,crystallographic orientation and mechanical properties of these CX stainless steel samples were investigated theoretically and experimentally via scanning electron microscope(SEM),X-ray diffraction(XRD),electron backscatter diffraction(EBSD)and transmission electron microscope(TEM).Based on the systematic study,the SLM CX stainless steel sample with best surface roughness(Ra=4.05±1.8μm)and relative density(Rd=99.72%±0.22%)under the optimal linear density(η=245 J/m)can be obtained.SLM CX stainless steel was primarily constituted by a large number of fine martensite(α’phase)structures(i.e.,cell structures,cellular dendrites and blocky grains)and a small quantity of austenite(γphase)structures.The pre ferred crystallographic orientation(i.e.,<111>direction)can be determined in the XZ plane of the SLM CX sample.Furthermore,under the optimal linear energy density,the good combinations with the highest ultimate tensile strength(UTS=1068.0%±5.9%)and the best total elongation(TE=15.70%±0.26%)of the SLM CX sample can be attained.Dislocation strengthening dominates the strengthening mechanism of the SLM CX sample in as-built state.
基金supported by the Sciences Platform Environment and Capacity Building Projects of GDAS(2021GDASYL-20210102005)the Guangdong Basic and Applied Basic Research Fund(2020A1515111031,2021A1515010939)+4 种基金the Young Elite Scientist Sponsorship Program by China Association for Science and Technology(CAST)(YESS20210269)Guangdong Provincial Special Support Program(2019BT02C629)Guangdong Academy of Sciences Development Special Fund Project(2022GDASZH-2022010107)Guangdong Academy of Sciences International Science and Technology Cooperation Platform Construction Project(2022GDASZH-2022010203-003)Guangzhou Key Field R&D Program(20200702008)。
文摘Fabrication of the Mg–9Al–1Zn–0.5Mn alloy with excellent mechanical performance using selective laser melting(SLM)technology is quite difficult owing to the poor weldability and low boiling point.To address these challenges and seek the optimal processing parameters,response surface methodology was systematically utilized to determine the appropriate SLM parameter combinations.Mg–9Al–1Zn–0.5Mn sample with high relative density(99.5±0.28%)and favorable mechanical properties(microhardness=95.6±5.28 HV_(0.1),UTS=370.2 MPa,and At=10.4%)was achieved using optimized SLM parameters(P=120 W,v=500 mm/s,and h=45μm).Sample is dominated by a random texture and microstructure is primarily constituted by quantities offine equiaxed grains(α-Mg phase),a small amount ofβ-Al_(12)Mg_(17) structures(4.96 vol%,including spherical:[2110]_(α)//[111]_(β)and long lath-like:[2110]_(α)//[115]_(β)or[1011]_(α)//[321]_(β)),and some short rod-shaped Al8Mn5 nanoparticles.Benefiting from grain boundary strengthening,solid solution strengthening,and precipitation hardening of various nanoparticles(β-Al12Mg17 and Al8Mn5),high-performance Mg–9Al–1Zn–0.5Mn alloy biomedical implants can be fabricated.Precipitation hardening dominates the strengthening mechanism of the SLM Mg–9Al–1Zn–0.5Mn alloy.
基金financially supported by the Sciences Platform Environment and Capacity Building Projects of GDAS(No.2021GDASYL-20210102005)the Guangdong Special Support Program(No.2019BT02C629)+2 种基金the GuangDong Basic and Applied Basic Research Foundation(Nos.2020A1515111031 and 2021A515010939)the Guangzhou Major Projects of Industry University-Research(IUR)Collaborative Innovation“Surface Treatment and Repair for Key Components of Industrial Gas Turbine(IGT).”support from the program of CSC(No.201801810066)support from the program of CSC(No.201801810106)。
文摘This work focuses on the structure and magnetic properties of Fe-50wt% Ni permalloy manufactured from the pre-alloyed powder by selective laser melting (SLM). The selective laser melted (SLMed) alloys were characterized by a 3D profilometer,optical microscope, scanning electron microscope, X-ray diffraction, etc. The effects of the volume energy density of laser(LVED) on structure, and magnetic properties with coercivity ( H), remanence ( B), and power losses ( P), were evaluated and discussed systematically. The results show that the relative porosity rate and the surface roughness of the SLMed specimens decreased with the increase in LVED. Only the γ-(FeNi) phase was detected in the X-ray diffraction patterns of the SLMed permalloys fabricated from the different LVEDs. Statistical analysis of optical microscopy images indicated that the grain coarsened at higher LVED. Furthermore, the microstructure of the SLMed parts was a typical columnar structure with an oriented growth of building direction. The highest microhardness reached 198 HV. Besides, the magnetic properties including B, H, and Pof SLMed samples decreased when the LVED ranged from 33.3 to 60.0 J/mm ~3 firstly and then increased while LVED further up to 93.3 J/mm, which is related to the decrease in porosity and the increase in grain size, while the higher residual stress and microcracks presented in the samples manufactured using very high LVED. The observed evolution of magnetic properties and LVED provides a good compromise in terms of reduced porosity and crack formation for the fabrication of SLMed Fe-50 wt% Ni permalloy. The theoretical mechanism in this study can offer guidance to further investigate SLMed soft magnetic alloys.
基金funded by the Natural Science Foundation of Zhejiang Province,China(No.MS25E080023)the Natural Science Foundation of Ningbo City,China(No.2024J130)+6 种基金the Fundamental Research Funds for the Provincial Universities of Zhejiang(No.SJLY2023009)the National"111"Center on Safety and Intelligent Operation of Sea Bridge(D21013)National Natural Science Foundation of China(Nos.71971059,52262047,52302388,52272334,and 61963011)the Natural Science Foundation of Jiangsu Province,China(No.BK20230853)the Specific Research Project of Guangxi for Research Bases and Talents(No.AD20159035)the Guilin Key R&D Program[No.20210214-1]the Liuzhou Key R&D Program(No.2022AAA0103).
文摘In the context of the COVID-19 epidemic,a"double-hazard scenario"consisting of a natural disaster and a public health event simultaneously accurring is more likely to arise.However,compared with single-hazard,multiple disasters confront the challenges of complexity,diversity,and demand urgency.To improve the efficiency of emergency material distribution under multiple disasters,this study first divided multiple disasters into three categoriles:independent scenario,sequential scenario,and coupling scenario.A set of evaluation index systems for multiple disasters was established to quantify the urgency of demand.The routing optimization model of emergency vehicles for multiple disasters was proposed by combining demand urgency and road damage,and the non-dominated sorting genetic algorithm II(NSGA-I)was used to simulate and validate the model.A coupling scenario considering two typical disasters of hurricanes and epidemics was selected as a validation example,and sensitivity analysis was also performed for different algorithms,scenarios,and constraints.The results demonstrated that the proposed model could effectively address the vehicle routing problem of emer-gency materials in the context of multiple disasters.Compared to the NSGA,the NSGA-II was used to reduce the total delivery time,cost,and penalty cost by 15.98%6,13.60%,and 16.14%,respectively.Compared with the independent scenario,the coupling scenario increased the total delivery time and cost by 186.28%and 132.48%during the epidemic.However,it reduced the total delivery time by 4.00%and increased the delivery cost by 23.55%compared with the hurricane.Compared with the model without consideration,the model considering demand urgency and road damage reduced the total delivery time and cost by 17.88%and 8.73%,respectively.The model constructed in this study addressed the vehicle routing problem considering the demand urgency and road damage in the optimization process,particularly in the context of multiple disasters.
