The Ni-based alloy composite coatings reinforced by nanostructured Al2O3-40%TiO2 multiphase ceramic particles were prepared on the surface of 7005 aluminum alloy by plasma spray technology. The microstructure and trib...The Ni-based alloy composite coatings reinforced by nanostructured Al2O3-40%TiO2 multiphase ceramic particles were prepared on the surface of 7005 aluminum alloy by plasma spray technology. The microstructure and tribological properties of the composite coatings were researched. The results show that the composite coatings mainly consist of γ-Ni, α-Al2O3, γ-Al2O3 and rutile-TiO2 etc, and exhibit lower friction coefficients and wear losses than the Ni-based alloy coatings at different loads and speeds. The composite coating bears low contact stress at 3 N and its wear mechanism is micro-cutting wear. As loads increase to 6-12 N, the contact stress is higher than the elastic limit stress of worn surface, and the wear mechanisms change into multi-plastic deformation wear, micro-brittle fracture wear and abrasive wear. With the increase of speeds, the contact temperature of worn surface increases. The composite coating experiences multi-plastic deformation wear, fatigue wear and adhesive wear.展开更多
Both the coarsening of Al2O3 nanoparticles and the growth of Cu nanograins of mechanically milled nanostructured Cu-5 vol.%Al2O3 composites with, and without, trace amounts of Ti during annealing at973 K for 1 h were ...Both the coarsening of Al2O3 nanoparticles and the growth of Cu nanograins of mechanically milled nanostructured Cu-5 vol.%Al2O3 composites with, and without, trace amounts of Ti during annealing at973 K for 1 h were investigated. It was found that doping with a small amount of Ti（e.g. 0.2 wt%） in a nanostructured Cu-5 vol.%Al2O3 composite effectively suppressed the coarsening of Al2O3 nanoparticles during exposure at this temperature. Further, the Ti addition also prevented the concomitant abnormal growth of the copper grains normally caused by the coarsening of the Al2O3 nanoparticles. Energy dispersive X-ray spectroscopy analysis of the Al2O3 nanoparticles in the annealed Cu-5 vol.%Al2 O3-0.2 wt%Ti sample suggested that the Ti atoms either diffused into the Al2O3 nanoparticles or segregated to the Cu/Al2O3 interfaces to form Ti-doped Al2O3 nanoparticles, which was more stable than Ti-free Al2O3 nanoparticles during annealing at high homologous temperatures.展开更多
This work investigates the effects of lubricant sulfur contents on the morphology,nanostructure,size distribution and elemental composition of diesel exhaust particle on a light-duty diesel engine. Three kinds of lubr...This work investigates the effects of lubricant sulfur contents on the morphology,nanostructure,size distribution and elemental composition of diesel exhaust particle on a light-duty diesel engine. Three kinds of lubricant（LS-oil,MS-oil and HS-oil,all of which have different sulfur contents：0.182%,0.583% and 1.06%,respectively）were used in this study. The morphologies and nanostructures of exhaust particles were analyzed using high-resolution transmission electron microscopy（TEM）. Size distributions of primary particles were determined through advanced image-processing software. Elemental compositions of exhaust particles were obtained through X-ray energy dispersive spectroscopy（EDS）. Results show that as lubricant sulfur contents increase,the macroscopic structure of diesel exhaust particles turn from chain-like to a more complex agglomerate. The inner cores of the core-shell structure belonging to these primary particles change little; the shell thickness decreases,and the spacing of carbon layer gradually descends,and amorphous materials that attached onto outer carbon layer of primary particles increase. Size distributions of primary particles present a unimodal and normal distribution,and higher sulfur contents lead to larger size primary particles. The sulfur content in lubricants directly affects the chemical composition in the particles. The content of C（carbon）decreases as sulfur increases in the lubricants,while the contents of O（oxygen）,S（sulfur）and trace elements（including S,Si（silicon）,Fe（ferrum）,P（phosphorus）,Ca（calcium）,Zn（zinc）,Mg（magnesium）,Cl（chlorine）and Ni（nickel））all increase in particles.展开更多
Enantiomeric discrimination plays a crucial role in various scientific domains,including analytical chemistry,chemical biology,pharmaceuticals,and pesticide research.A variety of theoretical frameworks and chiroptical...Enantiomeric discrimination plays a crucial role in various scientific domains,including analytical chemistry,chemical biology,pharmaceuticals,and pesticide research.A variety of theoretical frameworks and chiroptical spectroscopic methods,including optical rotation and circular dichroism,have been devised to identify and quantify enantiomers.Generally,circularly polarized light is utilized to determine the absolute configuration and composition of enantiomers.However,these techniques are not suitable for racemic mixtures or substances with minimal optical activity.Herein,we propose that ultraviolet-visible-absorption chiral anisotropy(UV-Vis-ChA)of chiral nanostructured Au particles(CNAPs)can be utilized for enantiomeric discrimination,using amino acids as a model system.The CNAPs,synthesized via a seed-mediated method using chiral glutathione as the symmetry-breaking agent,exhibit a helical nanocubic structure.Upon the addition of amino acid enantiomers to the CNAPs solution,the decrease in the UV-Vis absorbance of CNAPs solution,with varying rates,was induced by enantiomers with different enantiomeric excess(ee)values.The rate constant of absorbance decrease(k_(Δ))was proportional to the ee values,regardless of polarity,size,or chromophore type.It is speculated that the UV-Vis-ChA results from the selective aggregation of CNAPs due to the formation of coordination bonds with enantiomers which is driven by their spin polarizations.This work provides a cost-effective,broad-spectrum,and quantitative approach to enantiomeric discrimination.展开更多
文摘The Ni-based alloy composite coatings reinforced by nanostructured Al2O3-40%TiO2 multiphase ceramic particles were prepared on the surface of 7005 aluminum alloy by plasma spray technology. The microstructure and tribological properties of the composite coatings were researched. The results show that the composite coatings mainly consist of γ-Ni, α-Al2O3, γ-Al2O3 and rutile-TiO2 etc, and exhibit lower friction coefficients and wear losses than the Ni-based alloy coatings at different loads and speeds. The composite coating bears low contact stress at 3 N and its wear mechanism is micro-cutting wear. As loads increase to 6-12 N, the contact stress is higher than the elastic limit stress of worn surface, and the wear mechanisms change into multi-plastic deformation wear, micro-brittle fracture wear and abrasive wear. With the increase of speeds, the contact temperature of worn surface increases. The composite coating experiences multi-plastic deformation wear, fatigue wear and adhesive wear.
基金supported financially by the China Scholarship Council (CSC)National Natural Science Foundation of China (Project No. 51271115)+1 种基金the Ministry of Science and Technology, China (Project No. 2012CB619600)the SJTU-UNSW Strategic Collaboration to conduct this investigation
文摘Both the coarsening of Al2O3 nanoparticles and the growth of Cu nanograins of mechanically milled nanostructured Cu-5 vol.%Al2O3 composites with, and without, trace amounts of Ti during annealing at973 K for 1 h were investigated. It was found that doping with a small amount of Ti（e.g. 0.2 wt%） in a nanostructured Cu-5 vol.%Al2O3 composite effectively suppressed the coarsening of Al2O3 nanoparticles during exposure at this temperature. Further, the Ti addition also prevented the concomitant abnormal growth of the copper grains normally caused by the coarsening of the Al2O3 nanoparticles. Energy dispersive X-ray spectroscopy analysis of the Al2O3 nanoparticles in the annealed Cu-5 vol.%Al2 O3-0.2 wt%Ti sample suggested that the Ti atoms either diffused into the Al2O3 nanoparticles or segregated to the Cu/Al2O3 interfaces to form Ti-doped Al2O3 nanoparticles, which was more stable than Ti-free Al2O3 nanoparticles during annealing at high homologous temperatures.
基金supported by the National Natural Science Foundation of China(No.50906062)
文摘This work investigates the effects of lubricant sulfur contents on the morphology,nanostructure,size distribution and elemental composition of diesel exhaust particle on a light-duty diesel engine. Three kinds of lubricant（LS-oil,MS-oil and HS-oil,all of which have different sulfur contents：0.182%,0.583% and 1.06%,respectively）were used in this study. The morphologies and nanostructures of exhaust particles were analyzed using high-resolution transmission electron microscopy（TEM）. Size distributions of primary particles were determined through advanced image-processing software. Elemental compositions of exhaust particles were obtained through X-ray energy dispersive spectroscopy（EDS）. Results show that as lubricant sulfur contents increase,the macroscopic structure of diesel exhaust particles turn from chain-like to a more complex agglomerate. The inner cores of the core-shell structure belonging to these primary particles change little; the shell thickness decreases,and the spacing of carbon layer gradually descends,and amorphous materials that attached onto outer carbon layer of primary particles increase. Size distributions of primary particles present a unimodal and normal distribution,and higher sulfur contents lead to larger size primary particles. The sulfur content in lubricants directly affects the chemical composition in the particles. The content of C（carbon）decreases as sulfur increases in the lubricants,while the contents of O（oxygen）,S（sulfur）and trace elements（including S,Si（silicon）,Fe（ferrum）,P（phosphorus）,Ca（calcium）,Zn（zinc）,Mg（magnesium）,Cl（chlorine）and Ni（nickel））all increase in particles.
基金supported by the National Key R&D Program of China(No.2021YFA1200301,S.A.C.)the National Natural Science Foundation of China(No.21931008,S.A.C.)the Shanghai Pilot Program for Basic Research-Shanghai Jiao Tong University(No.21TQ1400219).
文摘Enantiomeric discrimination plays a crucial role in various scientific domains,including analytical chemistry,chemical biology,pharmaceuticals,and pesticide research.A variety of theoretical frameworks and chiroptical spectroscopic methods,including optical rotation and circular dichroism,have been devised to identify and quantify enantiomers.Generally,circularly polarized light is utilized to determine the absolute configuration and composition of enantiomers.However,these techniques are not suitable for racemic mixtures or substances with minimal optical activity.Herein,we propose that ultraviolet-visible-absorption chiral anisotropy(UV-Vis-ChA)of chiral nanostructured Au particles(CNAPs)can be utilized for enantiomeric discrimination,using amino acids as a model system.The CNAPs,synthesized via a seed-mediated method using chiral glutathione as the symmetry-breaking agent,exhibit a helical nanocubic structure.Upon the addition of amino acid enantiomers to the CNAPs solution,the decrease in the UV-Vis absorbance of CNAPs solution,with varying rates,was induced by enantiomers with different enantiomeric excess(ee)values.The rate constant of absorbance decrease(k_(Δ))was proportional to the ee values,regardless of polarity,size,or chromophore type.It is speculated that the UV-Vis-ChA results from the selective aggregation of CNAPs due to the formation of coordination bonds with enantiomers which is driven by their spin polarizations.This work provides a cost-effective,broad-spectrum,and quantitative approach to enantiomeric discrimination.
