The integration of dual-mesoporous structures,the construction of heterojunctions,and the incorporation of highly concentrated oxygen vacancies are pivotal for advancing metal oxide-based gas sensors.Nonetheless,achie...The integration of dual-mesoporous structures,the construction of heterojunctions,and the incorporation of highly concentrated oxygen vacancies are pivotal for advancing metal oxide-based gas sensors.Nonetheless,achieving an optimal design that simultaneously combines mesoporous structures,precise heterojunction modulation,and controlled oxygen vacancies through a one-step process remains challenging.This study proposes an innovative method for fabricating zinc stannate semiconductors featuring dual-mesoporous structures and tunable oxygen vacancies via a direct solution precursor plasma spray technique.As a proof of concept,the resulting zinc stannate-based coatings are applied to detect 2-undecanone,a key biomarker for rice aging.Remarkably,the zinc oxide/zinc stannate heterojunctions with a well-defined secondary pore structure exhibit exceptional gas-sensing performance for 2-undecanone at room temperature.Furthermore,practical experiments indicate that the developed sensor effectively identifies adulteration in various rice varieties.These results underscore the potential of this method for designing metal oxides with tailored properties for high-performance gas sensors.The enhanced adsorption capacity and dual-mesoporous features of this semiconductor make it a promising candidate for sensing applications in agricultural food safety inspections.展开更多
Intermetallic alloys offer exceptional high-temperature mechanical properties and low densities,thus rendering them suitable for a wide range of applications in aviation and spacecraft.However,their inherent brittlene...Intermetallic alloys offer exceptional high-temperature mechanical properties and low densities,thus rendering them suitable for a wide range of applications in aviation and spacecraft.However,their inherent brittleness at room temperature poses challenges in the manufacture of complex geometries.Hence,Laser additive manufacturing(LAM)has emerged as a promising approach to investigate the potential limitations of these materials.This review discusses the key findings and challenges associated with the LAM of intermetallic alloys,particu-larly NiAl,Ni_(3)Al,and TiAl,whose engineering applications are substantial.It provides an overview of typical defect morphologies,formation mechanisms,and strategies to prevent cracks and pores.Additionally,it presents an analysis of the microstructural characteristics of as-built and post-treated samples compared with those of samples prepared conventionally.Furthermore,the mechanical properties of the above-mentioned alloys at both room and high temperatures are reviewed,thus highlighting the effects of post-treatment processes.This review concludes with summary tables detailing the mechanical properties,which serve as useful references for researchers.展开更多
The understanding of the impact of high-velocity microparticles on human skin tissue is important for the ad-ministration of drugs during transdermal drug delivery.This paper aims to numerically investigate the dynami...The understanding of the impact of high-velocity microparticles on human skin tissue is important for the ad-ministration of drugs during transdermal drug delivery.This paper aims to numerically investigate the dynamic behavior of human skin tissue under micro-particle impact in transdermal drug delivery.The numerical model was developed based on a coupled smoothed particle hydrodynamics(SPH)and FEM method via commercial FE software RADIOSS.Analytical analysis was conducted applying the Poncelet model and was used as validation data.A hyperelastic one-term Ogden model with one pair of material parameters(μ,α)was implemented for the skin tissue.Sensitivity studies reveal that the effect of parameter α on the penetration process is much more significant than μ.Numerical results correlate well with the analytical curves with various particle diameters and impact velocities,its capability of predicting the penetration process of micro-particle impacts into skin tissues.This work can be further investigated to guide the design of transdermal drug delivery equipment.展开更多
Bismuth-doped antimony tungstate(Bi-doped Sb_(2)WO_(6))microspheres were synthesized via a novel hydrothermal synthesis approach.These microspheres were then used as active layers in gas sensors for the detection of c...Bismuth-doped antimony tungstate(Bi-doped Sb_(2)WO_(6))microspheres were synthesized via a novel hydrothermal synthesis approach.These microspheres were then used as active layers in gas sensors for the detection of carbon dioxide(CO_(2)),a significant greenhouse gas and a critical parameter for evaluating air quality.The incorporation of bismuth significantly enhances the gas-sensing performance of the Sb_(2)WO_(6)microspheres,with the 4%Bidoped sensing active layer achieving a remarkable response value of 15 when exposed to 200 ppm of CO_(2),outperforming the undoped Sb_(2)WO_(6).Furthermore,the selectivity of the 4%Bi-Sb_(2)WO_(6)sensor toward CO_(2)gas was enhanced relative to the Sb_(2)WO_(6)sensor.The fundamental mechanisms of gas sensing and the factors contributing to the improved CO_(2)response of 4%Bi-Sb_(2)WO_(6)micro spheres were investigated using density functional theory.Bi-doped Sb_(2)WO_(6)materials exhibit significant advantages in gas-sensing applications,including improved conductivity,enhanced gas adsorption capacity,increased reaction rates,good chemical stability,excellent selectivity,and the ability to adjust electron density.These characteristics enable Bi-doped Sb_(2)WO_(6)to demonstrate higher sensitivity and rapid response capabilities in gas sensors,making it suitable for practical applications.展开更多
针对智能交通领域多车协同驾驶中存在的通信信息乱序、丢包问题,研究网联式自主驾驶车辆协同控制技术,建立基于零阶保持(Zero Order Hold,ZOH)信息处理机制的自主驾驶车队控制模型,通过非线性系统状态估计算法进行延迟补偿,使得车队控...针对智能交通领域多车协同驾驶中存在的通信信息乱序、丢包问题,研究网联式自主驾驶车辆协同控制技术,建立基于零阶保持(Zero Order Hold,ZOH)信息处理机制的自主驾驶车队控制模型,通过非线性系统状态估计算法进行延迟补偿,使得车队控制模型在复杂汽车行驶环境下保持有效。通过构建由多辆实车组成的网联式自主驾驶车队,在封闭道路环境下进行协同驾驶编队测试,结合网络传输及传感器数据进行模型仿真,验证了模型在实车编队环境下的稳定性、有效性和实用性。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
This work focused on the deposition characteristics and wear behavior of Ni-coated graphite mixed with40 vol.% Al（Ni-Gr/Al） composite coatings sprayed on an Al alloy and a steel substrate by cold spraying（CS）. The...This work focused on the deposition characteristics and wear behavior of Ni-coated graphite mixed with40 vol.% Al（Ni-Gr/Al） composite coatings sprayed on an Al alloy and a steel substrate by cold spraying（CS）. The morphology of the flattened Ni-Gr particles was examined by single-impact tests. Crosssectional microstructure and wear performance of the Ni-Gr/Al composite coatings were studied. Results showed that a larger number of Ni-Gr particles were finally bonded with the steel substrate, whereas many craters existed on the Al alloy substrate after the single-impact tests. The coating on the steel substrate had a high thickness, high graphite content and low coeficient of friction（COF） compared to those on the Al alloy substrate. In addition, the CS coatings presented a homogeneous distribution and uniform morphology of graphite, and a comparative COF to that of conventional thermal sprayed coatings. It was shown that CS could avoid the decomposition and transformation of graphite phase.展开更多
In this study, friction stir processing（FSP） was employed to modify cold-sprayed（CSed） AA2024/Al2 O3 metal matrix composites（MMCs）. Three different rotation speeds with a constant traverse speed were used for FS...In this study, friction stir processing（FSP） was employed to modify cold-sprayed（CSed） AA2024/Al2 O3 metal matrix composites（MMCs）. Three different rotation speeds with a constant traverse speed were used for FSP. Microstructural analysis of the FSPed specimens reveals significant Al2 O3 particle refinement and improved particle distribution over the as-sprayed deposits. After FSP, a microstructural and mechanical gradient MMC through the thickness direction was obtained. Therefore, a hybrid technique combining these two solid-state processes, i.e. CS and FSP, was proposed to produce functionally gradient deposits. The Guinier-Preston-Bagaryatskii zone was dissolved during FSP, while the amounts at different rotation speeds were approximately the same, which is possibly due to the excellent thermal conductivity of the used Cu substrate. Mechanical property tests confirm that FSP can effectively improve the tensile performance and Vickers hardness of CSed AA2024/Al2 O3 MMCs. The properties can be further enhanced with a larger rotation speed with a maximum increase of 25.9% in ultimate tensile strength and27.4% in elongation at 1500 rpm. Friction tests show that FSP decreases the wear resistance of CSed MMCs deposits due to the breakup of Al2 O3 particles. The average values and fluctuations of friction coefficients at different rotation speeds vary significantly.展开更多
The excessive concentration of NO_(2) in the atmosphere has gained considerable attention due to its damage to the environment and human health. Gas sensor technology has important application prospects in detecting a...The excessive concentration of NO_(2) in the atmosphere has gained considerable attention due to its damage to the environment and human health. Gas sensor technology has important application prospects in detecting atmospheric NO_(2) concentration. Restricted by its wide bandgap, pristine ZnO needs additional energy to power the electronic transition as a gas sensing material.展开更多
A fully dense carbon nanotubes (CNTs) reinforced AlSi matrix composite with the multiscale nacre-like architecture was designed and successfully realized by flake powder metallurgy followed by cold spraying (CS). The ...A fully dense carbon nanotubes (CNTs) reinforced AlSi matrix composite with the multiscale nacre-like architecture was designed and successfully realized by flake powder metallurgy followed by cold spraying (CS). The nanolaminated and ultrafine-grained structure initially created in the CNT/AlSi flaky powder was perfectly conserved, due to the typical ‘cold’ feature of CS. As discussed based on finite element analysis and single splat observation, self-alignment behavior of the flaky powders during impact also allowed the formation of the microlaminated structure. Hence, the scalable CS technique opens a new avenue for bioinspired material design and fabrication with complex shape.展开更多
In this work,the Invar 36 alloys were manufactured using cold spray(CS)additive manufacturing technique.The systematic investigations were made on the microstructural evolution,thermal expansion and mechanical propert...In this work,the Invar 36 alloys were manufactured using cold spray(CS)additive manufacturing technique.The systematic investigations were made on the microstructural evolution,thermal expansion and mechanical properties under as-sprayed(AS)and heat-treated(HT)conditions.XRD(X-ray diffraction)and ICP-AES(inductively coupled plasma atomic emission spectroscopy)analyses show that no phase transformation,oxidation,nor element content change have occurred.The X-ray computed tomography(XCT)exhibited a near fully dense structure with a porosity of 0.025%in the helium-produced sample under as-sprayed condition,whereas the nitrogen-produced samples produced at 5 MPa and 800℃show more irregular pore defects.He-AS sample shows a more prominent grain refinement than that of nitrogen samples due to the more extensive plastic deformation.The post heat-treatment exhibited a promoted grain growth,inter-particle diffusion,as well as the formation of annealing twins.Between25℃and 200℃,the nitrogen samples possessed lower CTE(coefficient of thermal expansion)values(1.53×10^(-6)/℃)compared with those produced by casting and laser additive manufacturing.The He-AS samples exhibited a noticeable negative CTE value between 25℃and 200℃,which may due to the significant compressive residual stress(-272 MPa)compensating its displacement with temperature increase during CTE test.The N2-HT and He-HT Invar 36 samples present a notable balance between strength and ductility.In conclusion,the CS technique can be considered as a potential method to produce the Invar36 component with high thermal and mechanical performance.展开更多
Increasing the recrystallization temperature to achieve better high-temperature performance is critical in the development of molybdenum alloys for ultrahightemperature applications,such as the newest generation of mu...Increasing the recrystallization temperature to achieve better high-temperature performance is critical in the development of molybdenum alloys for ultrahightemperature applications,such as the newest generation of multitype high-temperature nuclear reactors.In this study,an innovative strategy was proposed to improve the performance of molybdenum alloys at high temperature by using the two-dimensional MAX(where M is an early transition metal,A is an A-group element and X is C or N)ceramic material Ti_(3)AlC_(2).The relationships between flow stress,strain rate and temperature were studied.The microstructure,distribution of misorientation and evolution of dislocations in the Mo-Ti_(3)AlC_(2) alloy were analyzed.The microscopic mechanism of the Ti_(3)AlC_(2) phase in the molybdenum alloy at high temperatures was clarified.The experimental results showed that the peak flow stress of Mo-Ti_(3)AlC_(2) at 1600℃ reached 155 MPa,which was161.8% greater than that of pure Mo.The activation energy of thermal deformation of Mo-Ti_(3)AlC_(2) was as large as537 kJ·mol~(-1),which was 17.6% more than that of pure Mo.The recrystallization temperature reached 1600℃ or even higher.The topological reaction of the Ti_(3)AlC_(2) phase consumed a large amount of energy at high temperatures,resulting in increases in the deformation activation energy.Nanolayer structures of AlTi_3 and Ti-O Magneli-phase oxides(Ti_nO_(2n-1)) were formed in-situ,which relied on kink bands and interlayer slip,resulting in many dislocations during deformation.Therefore,the special two-dimensional of the structure Ti_(3)AlC_(2) ceramic inhibited the recrystallization behavior of the Mo alloy.The results of this study can provide theoretical guidance for the development of a new generation of molybdenum alloys for use in ultrahigh-temperature environments.展开更多
In this study, cold spraying（CS） was used to deposit a mixture of nickel-coated graphite and 40 vol.% Al powder（Ni-Gr/Al） on a steel substrate aiming to effectively preserve a certain volume fraction of graphite i...In this study, cold spraying（CS） was used to deposit a mixture of nickel-coated graphite and 40 vol.% Al powder（Ni-Gr/Al） on a steel substrate aiming to effectively preserve a certain volume fraction of graphite in the deposited Ni-Gr/Al composite coating. The microstructure of the as-sprayed coating and the effect of post-spray heat-treatment（PSHT） temperatures on the in-situ formation of Ni-Al intermetallic phases in coating were studied. The tribological behaviors of the as-sprayed coating and the PSHTed coating under 450？C were tested at 25？C, while the as-sprayed coating was tested at 450？C for comparison.As a result, the Ni-Gr particles showed a homogenous distribution in the coating. The multilayer Ni-Al intermetallics-coated graphite/Al composite coating was achieved in situ after the PSHT of 450？C, where the graphite did decompose at 550？C leaving big pores in the coating. The coefficients of friction（COF）of the CSed coating and the PSHTed coating were measured at 450？C as well as 25？C, which showed a similar tendency, much higher than that of the CSed coating tested at 25？C. The lubrication phase（graphite） improved the formation of a graphite film during sliding friction and decreased the COF, while the hard Ni-Al intermetallic phases contributed to the increase of COF.展开更多
This paper proposes a simple solution for the stabilization of a mini-quadcopter carrying a 3DoF（degrees of freedom） manipulator robot in order to enhance its achievable workspace and application profile. Since the ...This paper proposes a simple solution for the stabilization of a mini-quadcopter carrying a 3DoF（degrees of freedom） manipulator robot in order to enhance its achievable workspace and application profile. Since the motion of the arm induces torques which degrade the stability of the system, in the present work, we consider the stabilization of both subsystems： the quadcopter and the robotic arm. The mathematical model of the system is based on quaternions. Likewise, an attitude control law consisting of a bounded quaternion-based feedback stabilizes the quadcopter to a desired attitude while the arm is evolving. The next stage is the translational dynamics which is simplified for control（nonlinear） design purposes. The aforementioned controllers are based on saturation functions whose stability is explicitly proved in the Lyapunov sense. Finally, experimental results and a statistical study validate the proposed control strategy.展开更多
基金supported by the Outstanding Youth Foundation of Jiangsu Province of China(Grant No.BK20211548)the Yangzhou Science and Technology Plan Project(Grant No.YZ2023246)。
文摘The integration of dual-mesoporous structures,the construction of heterojunctions,and the incorporation of highly concentrated oxygen vacancies are pivotal for advancing metal oxide-based gas sensors.Nonetheless,achieving an optimal design that simultaneously combines mesoporous structures,precise heterojunction modulation,and controlled oxygen vacancies through a one-step process remains challenging.This study proposes an innovative method for fabricating zinc stannate semiconductors featuring dual-mesoporous structures and tunable oxygen vacancies via a direct solution precursor plasma spray technique.As a proof of concept,the resulting zinc stannate-based coatings are applied to detect 2-undecanone,a key biomarker for rice aging.Remarkably,the zinc oxide/zinc stannate heterojunctions with a well-defined secondary pore structure exhibit exceptional gas-sensing performance for 2-undecanone at room temperature.Furthermore,practical experiments indicate that the developed sensor effectively identifies adulteration in various rice varieties.These results underscore the potential of this method for designing metal oxides with tailored properties for high-performance gas sensors.The enhanced adsorption capacity and dual-mesoporous features of this semiconductor make it a promising candidate for sensing applications in agricultural food safety inspections.
基金supported by National Key Research and Development Program of China(Grant No.2021YFB3702502)National Natural Science Foundation of China(Grant Nos.52271035,and 52474412)+1 种基金Natural Science Foundation of Shanghai,China(Grant No.23ZR1421500)the SPMI Project from Shanghai Academy of Spaceflight Technology(Grant No.SPMI2022-06).
文摘Intermetallic alloys offer exceptional high-temperature mechanical properties and low densities,thus rendering them suitable for a wide range of applications in aviation and spacecraft.However,their inherent brittleness at room temperature poses challenges in the manufacture of complex geometries.Hence,Laser additive manufacturing(LAM)has emerged as a promising approach to investigate the potential limitations of these materials.This review discusses the key findings and challenges associated with the LAM of intermetallic alloys,particu-larly NiAl,Ni_(3)Al,and TiAl,whose engineering applications are substantial.It provides an overview of typical defect morphologies,formation mechanisms,and strategies to prevent cracks and pores.Additionally,it presents an analysis of the microstructural characteristics of as-built and post-treated samples compared with those of samples prepared conventionally.Furthermore,the mechanical properties of the above-mentioned alloys at both room and high temperatures are reviewed,thus highlighting the effects of post-treatment processes.This review concludes with summary tables detailing the mechanical properties,which serve as useful references for researchers.
基金supported by the Nanjing Institute of Technology(Grant No.YKJ202301).
文摘The understanding of the impact of high-velocity microparticles on human skin tissue is important for the ad-ministration of drugs during transdermal drug delivery.This paper aims to numerically investigate the dynamic behavior of human skin tissue under micro-particle impact in transdermal drug delivery.The numerical model was developed based on a coupled smoothed particle hydrodynamics(SPH)and FEM method via commercial FE software RADIOSS.Analytical analysis was conducted applying the Poncelet model and was used as validation data.A hyperelastic one-term Ogden model with one pair of material parameters(μ,α)was implemented for the skin tissue.Sensitivity studies reveal that the effect of parameter α on the penetration process is much more significant than μ.Numerical results correlate well with the analytical curves with various particle diameters and impact velocities,its capability of predicting the penetration process of micro-particle impacts into skin tissues.This work can be further investigated to guide the design of transdermal drug delivery equipment.
基金financially supported by the Outstanding Youth Foundation of Jiangsu Province of China(No.BK20211548)Yangzhou Science and Technology Plan Project(No.YZ2023246)+1 种基金China Scholarship Council(No.202308320445)the Postgraduate Research and Practice Innovation Program of Jiangsu Province of China(No.KYCX23_3551)
文摘Bismuth-doped antimony tungstate(Bi-doped Sb_(2)WO_(6))microspheres were synthesized via a novel hydrothermal synthesis approach.These microspheres were then used as active layers in gas sensors for the detection of carbon dioxide(CO_(2)),a significant greenhouse gas and a critical parameter for evaluating air quality.The incorporation of bismuth significantly enhances the gas-sensing performance of the Sb_(2)WO_(6)microspheres,with the 4%Bidoped sensing active layer achieving a remarkable response value of 15 when exposed to 200 ppm of CO_(2),outperforming the undoped Sb_(2)WO_(6).Furthermore,the selectivity of the 4%Bi-Sb_(2)WO_(6)sensor toward CO_(2)gas was enhanced relative to the Sb_(2)WO_(6)sensor.The fundamental mechanisms of gas sensing and the factors contributing to the improved CO_(2)response of 4%Bi-Sb_(2)WO_(6)micro spheres were investigated using density functional theory.Bi-doped Sb_(2)WO_(6)materials exhibit significant advantages in gas-sensing applications,including improved conductivity,enhanced gas adsorption capacity,increased reaction rates,good chemical stability,excellent selectivity,and the ability to adjust electron density.These characteristics enable Bi-doped Sb_(2)WO_(6)to demonstrate higher sensitivity and rapid response capabilities in gas sensors,making it suitable for practical applications.
文摘针对智能交通领域多车协同驾驶中存在的通信信息乱序、丢包问题,研究网联式自主驾驶车辆协同控制技术,建立基于零阶保持(Zero Order Hold,ZOH)信息处理机制的自主驾驶车队控制模型,通过非线性系统状态估计算法进行延迟补偿,使得车队控制模型在复杂汽车行驶环境下保持有效。通过构建由多辆实车组成的网联式自主驾驶车队,在封闭道路环境下进行协同驾驶编队测试,结合网络传输及传感器数据进行模型仿真,验证了模型在实车编队环境下的稳定性、有效性和实用性。
基金supported by the Technical Project of Guangdong Province, China (Nos. 2020B090923002, 2021A1515011756)GDAS’ Project of Science and Technology Development, China (No. 2021GDASYL20210302006)+3 种基金Sciences Platform Environment and Capacity Building Projects of GDAS, China (No. 2021GDASYL-20210102005)Key R&D Program of Guangdong Province, China (No. 2020B090923002)Guangdong Special Support Program, China (No. 2019BT02C629)Guangdong Basic and Applied Basic Research Fund, China (Nos. 2020A1515111031, 2021A1515010939)。
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financially supported by the National Natural Science Foundation of China(No.51574196)the 111 Project(No.B08040)+1 种基金the support from programs of China Scholarship Council(No.201404490058)Marie-Curie(No.268696)
文摘This work focused on the deposition characteristics and wear behavior of Ni-coated graphite mixed with40 vol.% Al（Ni-Gr/Al） composite coatings sprayed on an Al alloy and a steel substrate by cold spraying（CS）. The morphology of the flattened Ni-Gr particles was examined by single-impact tests. Crosssectional microstructure and wear performance of the Ni-Gr/Al composite coatings were studied. Results showed that a larger number of Ni-Gr particles were finally bonded with the steel substrate, whereas many craters existed on the Al alloy substrate after the single-impact tests. The coating on the steel substrate had a high thickness, high graphite content and low coeficient of friction（COF） compared to those on the Al alloy substrate. In addition, the CS coatings presented a homogeneous distribution and uniform morphology of graphite, and a comparative COF to that of conventional thermal sprayed coatings. It was shown that CS could avoid the decomposition and transformation of graphite phase.
基金financially by the National Key Research and Development Program of China (No. 2016YFB1100104)the Fund of SAST (No. SAST2016043)the 111 Project (No. B08040)
文摘In this study, friction stir processing（FSP） was employed to modify cold-sprayed（CSed） AA2024/Al2 O3 metal matrix composites（MMCs）. Three different rotation speeds with a constant traverse speed were used for FSP. Microstructural analysis of the FSPed specimens reveals significant Al2 O3 particle refinement and improved particle distribution over the as-sprayed deposits. After FSP, a microstructural and mechanical gradient MMC through the thickness direction was obtained. Therefore, a hybrid technique combining these two solid-state processes, i.e. CS and FSP, was proposed to produce functionally gradient deposits. The Guinier-Preston-Bagaryatskii zone was dissolved during FSP, while the amounts at different rotation speeds were approximately the same, which is possibly due to the excellent thermal conductivity of the used Cu substrate. Mechanical property tests confirm that FSP can effectively improve the tensile performance and Vickers hardness of CSed AA2024/Al2 O3 MMCs. The properties can be further enhanced with a larger rotation speed with a maximum increase of 25.9% in ultimate tensile strength and27.4% in elongation at 1500 rpm. Friction tests show that FSP decreases the wear resistance of CSed MMCs deposits due to the breakup of Al2 O3 particles. The average values and fluctuations of friction coefficients at different rotation speeds vary significantly.
基金financially supported by the National Natural Science Foundation of China (No. 51872254)the National Key Research & Development Program of China (No. 2017YFE0115900)the Outstanding Youth Foundation of Jiangsu Province of China (No. BK20210027)。
文摘The excessive concentration of NO_(2) in the atmosphere has gained considerable attention due to its damage to the environment and human health. Gas sensor technology has important application prospects in detecting atmospheric NO_(2) concentration. Restricted by its wide bandgap, pristine ZnO needs additional energy to power the electronic transition as a gas sensing material.
基金financial support from China Scholarship Council for his Ph.D. projectThe TEM facility in Lille, France, is supported by the Conseil Regional du Nord-Pas de Calais and the European Regional Development Fund
文摘A fully dense carbon nanotubes (CNTs) reinforced AlSi matrix composite with the multiscale nacre-like architecture was designed and successfully realized by flake powder metallurgy followed by cold spraying (CS). The nanolaminated and ultrafine-grained structure initially created in the CNT/AlSi flaky powder was perfectly conserved, due to the typical ‘cold’ feature of CS. As discussed based on finite element analysis and single splat observation, self-alignment behavior of the flaky powders during impact also allowed the formation of the microlaminated structure. Hence, the scalable CS technique opens a new avenue for bioinspired material design and fabrication with complex shape.
基金supported financially by the National Key Research and Development Program of China(No.2019YFA0705300)the Guangdong Special Support Program(No.2019BT02C629)+6 种基金the National Natural Science Foundation of China(No.51690160)the Shanghai Science and Technology Committee(No.19DZ1100704)the Shanghai Sailing Program(No.19YF1415900)Golden Apple Project of Baosteel Co.,Ltd(No.A19EC13500)the Guangdong Basic and Applied Basic Research Foundation(No.2019B1515120016)the Guangzhou Science and Technology Program(Nos.202002030290 and 202007020008)the GDAS’Project of Science and Technology Development(Nos.2019GDASYL-0503006 and 2020GDASYL-20200302011)。
文摘In this work,the Invar 36 alloys were manufactured using cold spray(CS)additive manufacturing technique.The systematic investigations were made on the microstructural evolution,thermal expansion and mechanical properties under as-sprayed(AS)and heat-treated(HT)conditions.XRD(X-ray diffraction)and ICP-AES(inductively coupled plasma atomic emission spectroscopy)analyses show that no phase transformation,oxidation,nor element content change have occurred.The X-ray computed tomography(XCT)exhibited a near fully dense structure with a porosity of 0.025%in the helium-produced sample under as-sprayed condition,whereas the nitrogen-produced samples produced at 5 MPa and 800℃show more irregular pore defects.He-AS sample shows a more prominent grain refinement than that of nitrogen samples due to the more extensive plastic deformation.The post heat-treatment exhibited a promoted grain growth,inter-particle diffusion,as well as the formation of annealing twins.Between25℃and 200℃,the nitrogen samples possessed lower CTE(coefficient of thermal expansion)values(1.53×10^(-6)/℃)compared with those produced by casting and laser additive manufacturing.The He-AS samples exhibited a noticeable negative CTE value between 25℃and 200℃,which may due to the significant compressive residual stress(-272 MPa)compensating its displacement with temperature increase during CTE test.The N2-HT and He-HT Invar 36 samples present a notable balance between strength and ductility.In conclusion,the CS technique can be considered as a potential method to produce the Invar36 component with high thermal and mechanical performance.
基金sponsored by National Key R&D Program of China (No.2020YFB2008400)Key Technology and Development Program of Henan Province (No.232102231024)。
文摘Increasing the recrystallization temperature to achieve better high-temperature performance is critical in the development of molybdenum alloys for ultrahightemperature applications,such as the newest generation of multitype high-temperature nuclear reactors.In this study,an innovative strategy was proposed to improve the performance of molybdenum alloys at high temperature by using the two-dimensional MAX(where M is an early transition metal,A is an A-group element and X is C or N)ceramic material Ti_(3)AlC_(2).The relationships between flow stress,strain rate and temperature were studied.The microstructure,distribution of misorientation and evolution of dislocations in the Mo-Ti_(3)AlC_(2) alloy were analyzed.The microscopic mechanism of the Ti_(3)AlC_(2) phase in the molybdenum alloy at high temperatures was clarified.The experimental results showed that the peak flow stress of Mo-Ti_(3)AlC_(2) at 1600℃ reached 155 MPa,which was161.8% greater than that of pure Mo.The activation energy of thermal deformation of Mo-Ti_(3)AlC_(2) was as large as537 kJ·mol~(-1),which was 17.6% more than that of pure Mo.The recrystallization temperature reached 1600℃ or even higher.The topological reaction of the Ti_(3)AlC_(2) phase consumed a large amount of energy at high temperatures,resulting in increases in the deformation activation energy.Nanolayer structures of AlTi_3 and Ti-O Magneli-phase oxides(Ti_nO_(2n-1)) were formed in-situ,which relied on kink bands and interlayer slip,resulting in many dislocations during deformation.Therefore,the special two-dimensional of the structure Ti_(3)AlC_(2) ceramic inhibited the recrystallization behavior of the Mo alloy.The results of this study can provide theoretical guidance for the development of a new generation of molybdenum alloys for use in ultrahigh-temperature environments.
基金financial support from the program of China Scholarship Council (No. 201404490058)Marie-Curie (No. 268696)+2 种基金the National Key Research and Development Program of China (No. 2016YFE0701203)the National Natural Science Foundation of China (No. 51574196)the 111 Project (No. B08040)
文摘In this study, cold spraying（CS） was used to deposit a mixture of nickel-coated graphite and 40 vol.% Al powder（Ni-Gr/Al） on a steel substrate aiming to effectively preserve a certain volume fraction of graphite in the deposited Ni-Gr/Al composite coating. The microstructure of the as-sprayed coating and the effect of post-spray heat-treatment（PSHT） temperatures on the in-situ formation of Ni-Al intermetallic phases in coating were studied. The tribological behaviors of the as-sprayed coating and the PSHTed coating under 450？C were tested at 25？C, while the as-sprayed coating was tested at 450？C for comparison.As a result, the Ni-Gr particles showed a homogenous distribution in the coating. The multilayer Ni-Al intermetallics-coated graphite/Al composite coating was achieved in situ after the PSHT of 450？C, where the graphite did decompose at 550？C leaving big pores in the coating. The coefficients of friction（COF）of the CSed coating and the PSHTed coating were measured at 450？C as well as 25？C, which showed a similar tendency, much higher than that of the CSed coating tested at 25？C. The lubrication phase（graphite） improved the formation of a graphite film during sliding friction and decreased the COF, while the hard Ni-Al intermetallic phases contributed to the increase of COF.
基金supported by CONACYT-Mexico,Lab Ex PERSYVAL-Lab(No.ANR-11-LABX-0025)Equipex ROBOTEX(No.ANR-10-EQPX-44-01)
文摘This paper proposes a simple solution for the stabilization of a mini-quadcopter carrying a 3DoF（degrees of freedom） manipulator robot in order to enhance its achievable workspace and application profile. Since the motion of the arm induces torques which degrade the stability of the system, in the present work, we consider the stabilization of both subsystems： the quadcopter and the robotic arm. The mathematical model of the system is based on quaternions. Likewise, an attitude control law consisting of a bounded quaternion-based feedback stabilizes the quadcopter to a desired attitude while the arm is evolving. The next stage is the translational dynamics which is simplified for control（nonlinear） design purposes. The aforementioned controllers are based on saturation functions whose stability is explicitly proved in the Lyapunov sense. Finally, experimental results and a statistical study validate the proposed control strategy.
