The effects of applying an electromagnetic interaction of low intensity (EMILI) on the microstructure and corrosion resistance of 7075-T651 Al alloy plates (13 mm in thickness) during modified indirect electric arc (M...The effects of applying an electromagnetic interaction of low intensity (EMILI) on the microstructure and corrosion resistance of 7075-T651 Al alloy plates (13 mm in thickness) during modified indirect electric arc (MIEA) welding were investigated. The welding process was conducted in a single pass with a heat input of ~1.5 kJ/mm. The microstructural observations of the welds were correlated with the effect of EMILI on the local mechanical properties and the corrosion resistance in natural seawater by means of microhardness measurements and electrochemical impedance spectroscopy, respectively. Microstructural characterization of the welds revealed a grain refinement in the weld metal due to the electromagnetic stirring induced by EMILI of 3 mT during welding. In addition, observations in the scanning electron microscope showed that the precipitation of Cu-rich phases and segregation of eutectics were reduced in the heat affected zone (HAZ) also as an effect of EMILI. The high corrosion dissolution of the 7075-T651 welds in natural seawater and the extent of overaging in the HAZ were reduced when welding with EMILI of 3 mT. Thus, EMILI along with the MIEA technique may lead to welded joints with better microstructural characteristics, improved mechanical properties in the HAZ and reduced electrochemical activity.展开更多
Nanosized Ni particles with an average diameter of about 8 nm were prepared by reducing of NiCl 2 with sodium borohydride (NaBH 4 ) in aqueous solution. By moderate annealing in protective atmosphere, the composite gr...Nanosized Ni particles with an average diameter of about 8 nm were prepared by reducing of NiCl 2 with sodium borohydride (NaBH 4 ) in aqueous solution. By moderate annealing in protective atmosphere, the composite grew up to be 15-20 nm particles. Both of the as-prepared and annealed Ni particles were coated by a layer of manganese oxide via decomposition reaction in aqueous KMnO4 solution. Hysteresis loops of as-prepared samples show a large increase in the magnetization with decreasing temperature and an unsaturated component at high magnetic field. In contrast, the ferromagnetic characteristics of annealed one are much stronger with large magnetization and coercivity. The thermomagnetic curves verified the coexistence of ferromagnetic Ni and antiferromangetic Mn oxide phases. But there exists no exchange bias behavior in the samples, even though the interface structure between the ferromagnetic Ni core and the antiferromagnetic manganese oxides has been distinctly formed. The absence of exchange bias probably originates from the weak ferromagnetic characteristic of Ni cores.展开更多
By the combination of high-temperature organometallic synthesis and phase transfer through complete ligand-exchange withmixed phosphate, highly water-dispersible Fe3O4nanoparticles with narrow size distribution are ob...By the combination of high-temperature organometallic synthesis and phase transfer through complete ligand-exchange withmixed phosphate, highly water-dispersible Fe3O4nanoparticles with narrow size distribution are obtained, which show appli-cable response to magnetic field. IR and -potential characterization of this system provides insights into ligand structures onparticle surface.展开更多
Water-soluble magnetite nanocrystals have been prepared by one-step non-alkoxide sol-gel method.The magnetic properties of magnetite nanocrystals obtained are size dependent.The experimental results also reveal that 2...Water-soluble magnetite nanocrystals have been prepared by one-step non-alkoxide sol-gel method.The magnetic properties of magnetite nanocrystals obtained are size dependent.The experimental results also reveal that 2-pyrrolidone not only serves as solvent,but also involves surface coordination which renders the magnetite nanoparticles water-soluble and colloidal solution stable.Although the current synthetic approach is a small modification to the non-alkoxide sol-gel method,it allows us to directly obtain high-quality water-soluble magnetic nanocrystals.In addition,we realize that this method could be easily extended to preparation of many other transition and main group metal oxide water-soluble nanocrystals only from simple metal ion salts.展开更多
One of the primary aims of the actinide community within nanoscience is to develop a good understanding similar to what is currently the case for stable elements. As a consequence, efficient, reliable and versatile sy...One of the primary aims of the actinide community within nanoscience is to develop a good understanding similar to what is currently the case for stable elements. As a consequence, efficient, reliable and versatile synthesis techniques dedicated to the formation of new actinide-based nano-objects （e.g., nanocrystals） are necessary. Hence, a ＂library＂ dedicated to the preparation of various actinidebased nanoscale building blocks is currently being developed. Nanoscale building blocks with tunable sizes, shapes and compositions are of prime importance. So far, the non-aqueous synthesis method in highly coordinating organic media is the only approach which has demonstrated the capability to provide size and shape control of actinide-based nanocrystals （both for thorium and uranium, and recently extended to neptunium and plutonium）. In this paper, we demonstrate that the non-aqueous approach is also well adapted to control the chemical composition of the nanocrystals obtained when mixing two different actinides. Indeed, the controlled hot co-injection of thorium acetylacetonate and uranyl acetate （together with additional capping agents） into benzyl ether can be used to synthesize thorium/uranium mixed oxide nanocrystals covering the full compositional spectrum. Additionally, we found that both size and shape are modified as a function of the thorium：uranium ratio. Finally, the magnetic properties of the different thorium/uranium mixed oxide nanocrystals were investigated. Contrary to several reports, we did not observe any ferromagnetic behavior. As a consequence, ferromagnetism cannot be described as a universal feature of nanocrystals of non-magnetic oxides as recently claimed in the literature.展开更多
In this review,we review the progress of research on ZnO-and In2O3-based diluted magnetic oxides(DMOs).Firstly,we present the preparation and characterization of DMOs.The former includes the preparation methods and co...In this review,we review the progress of research on ZnO-and In2O3-based diluted magnetic oxides(DMOs).Firstly,we present the preparation and characterization of DMOs.The former includes the preparation methods and conditions,and the latter includes the characterization techniques for measuring microstructures.Secondly,we introduce the magnetic and transport properties of DMOs,as well as the relationship between them.Thirdly,the origin and mechanism of the ferromagnetism are discussed.Fourthly,we introduce other related work,including computational work and pertinent heterogeneous structures,such as multilayers and magnetic tunnel junctions.Finally,we provide an overview and outlook for DMOs.展开更多
A series of new lanthanide-radical complexes [{Ln（hfac）3}2（NITPhlM）2] （Ln = Nd （1）, Eu （2）, Tb （3）, Er （4）; hfac = hexafluoroacetylacetonate; NITPhlM = 2-[4-（1-imidazole）phenyl]-4,4,5,5-tetramethylimida...A series of new lanthanide-radical complexes [{Ln（hfac）3}2（NITPhlM）2] （Ln = Nd （1）, Eu （2）, Tb （3）, Er （4）; hfac = hexafluoroacetylacetonate; NITPhlM = 2-[4-（1-imidazole）phenyl]-4,4,5,5-tetramethylimidazoline-l-oxyl-3-oxide） have been prepared and characterized. Single crystal X-ray diffraction analyses reveal that these complexes are isostructural with one-dimensional chain structures. These consist in Ln（hfac）3 units bridged by the paramagnetic ligands by the means of coor- dination of their nitronyl nitroxide groups and imidazole rings. Interestingly, each Ln ion is either bound to two nitronyl ni- troxide groups or to two imidazole units, and the different Ln centers alternate along the chain. Magnetic studies show that complex 3 exhibits a single-chain magnet behavior.展开更多
文摘The effects of applying an electromagnetic interaction of low intensity (EMILI) on the microstructure and corrosion resistance of 7075-T651 Al alloy plates (13 mm in thickness) during modified indirect electric arc (MIEA) welding were investigated. The welding process was conducted in a single pass with a heat input of ~1.5 kJ/mm. The microstructural observations of the welds were correlated with the effect of EMILI on the local mechanical properties and the corrosion resistance in natural seawater by means of microhardness measurements and electrochemical impedance spectroscopy, respectively. Microstructural characterization of the welds revealed a grain refinement in the weld metal due to the electromagnetic stirring induced by EMILI of 3 mT during welding. In addition, observations in the scanning electron microscope showed that the precipitation of Cu-rich phases and segregation of eutectics were reduced in the heat affected zone (HAZ) also as an effect of EMILI. The high corrosion dissolution of the 7075-T651 welds in natural seawater and the extent of overaging in the HAZ were reduced when welding with EMILI of 3 mT. Thus, EMILI along with the MIEA technique may lead to welded joints with better microstructural characteristics, improved mechanical properties in the HAZ and reduced electrochemical activity.
基金the National Natural Science Foundation of China (Grant Nos. 50271026 and 50971044)the International S&T Cooperation Program of China (Grant No. 2012DFA51300)
文摘Nanosized Ni particles with an average diameter of about 8 nm were prepared by reducing of NiCl 2 with sodium borohydride (NaBH 4 ) in aqueous solution. By moderate annealing in protective atmosphere, the composite grew up to be 15-20 nm particles. Both of the as-prepared and annealed Ni particles were coated by a layer of manganese oxide via decomposition reaction in aqueous KMnO4 solution. Hysteresis loops of as-prepared samples show a large increase in the magnetization with decreasing temperature and an unsaturated component at high magnetic field. In contrast, the ferromagnetic characteristics of annealed one are much stronger with large magnetization and coercivity. The thermomagnetic curves verified the coexistence of ferromagnetic Ni and antiferromangetic Mn oxide phases. But there exists no exchange bias behavior in the samples, even though the interface structure between the ferromagnetic Ni core and the antiferromagnetic manganese oxides has been distinctly formed. The absence of exchange bias probably originates from the weak ferromagnetic characteristic of Ni cores.
基金supported by the National Natural Science Foundation of China (Grant No. 20673031)the National Basic Research Program of China (Grant No. 2011CB932803)
文摘By the combination of high-temperature organometallic synthesis and phase transfer through complete ligand-exchange withmixed phosphate, highly water-dispersible Fe3O4nanoparticles with narrow size distribution are obtained, which show appli-cable response to magnetic field. IR and -potential characterization of this system provides insights into ligand structures onparticle surface.
基金supported by the National Natural Science Foundation of China (Grant No. 50901052, 51071109)Projects of Shanghai Science and Technology Committee (Grant No. 10dz2211300)Program for Young Excellent Talents in Tongji University (Grant No. 2009KJ003)
文摘Water-soluble magnetite nanocrystals have been prepared by one-step non-alkoxide sol-gel method.The magnetic properties of magnetite nanocrystals obtained are size dependent.The experimental results also reveal that 2-pyrrolidone not only serves as solvent,but also involves surface coordination which renders the magnetite nanoparticles water-soluble and colloidal solution stable.Although the current synthetic approach is a small modification to the non-alkoxide sol-gel method,it allows us to directly obtain high-quality water-soluble magnetic nanocrystals.In addition,we realize that this method could be easily extended to preparation of many other transition and main group metal oxide water-soluble nanocrystals only from simple metal ion salts.
文摘One of the primary aims of the actinide community within nanoscience is to develop a good understanding similar to what is currently the case for stable elements. As a consequence, efficient, reliable and versatile synthesis techniques dedicated to the formation of new actinide-based nano-objects （e.g., nanocrystals） are necessary. Hence, a ＂library＂ dedicated to the preparation of various actinidebased nanoscale building blocks is currently being developed. Nanoscale building blocks with tunable sizes, shapes and compositions are of prime importance. So far, the non-aqueous synthesis method in highly coordinating organic media is the only approach which has demonstrated the capability to provide size and shape control of actinide-based nanocrystals （both for thorium and uranium, and recently extended to neptunium and plutonium）. In this paper, we demonstrate that the non-aqueous approach is also well adapted to control the chemical composition of the nanocrystals obtained when mixing two different actinides. Indeed, the controlled hot co-injection of thorium acetylacetonate and uranyl acetate （together with additional capping agents） into benzyl ether can be used to synthesize thorium/uranium mixed oxide nanocrystals covering the full compositional spectrum. Additionally, we found that both size and shape are modified as a function of the thorium：uranium ratio. Finally, the magnetic properties of the different thorium/uranium mixed oxide nanocrystals were investigated. Contrary to several reports, we did not observe any ferromagnetic behavior. As a consequence, ferromagnetism cannot be described as a universal feature of nanocrystals of non-magnetic oxides as recently claimed in the literature.
基金supported by China National Funds for Distinguished Young Scientists(Grant No.51025101)the National Natural Science Foundation of China(Grant Nos.11274214,11104173 and 61204097)+1 种基金the Research Fund for the Doctoral Program of Higher Education(Grant No. 20101404120002)the Youth Science Foundation of Shanxi Province (Grant Nos.2011021021-1,2011021021-2 and 2012021020-2)
文摘In this review,we review the progress of research on ZnO-and In2O3-based diluted magnetic oxides(DMOs).Firstly,we present the preparation and characterization of DMOs.The former includes the preparation methods and conditions,and the latter includes the characterization techniques for measuring microstructures.Secondly,we introduce the magnetic and transport properties of DMOs,as well as the relationship between them.Thirdly,the origin and mechanism of the ferromagnetism are discussed.Fourthly,we introduce other related work,including computational work and pertinent heterogeneous structures,such as multilayers and magnetic tunnel junctions.Finally,we provide an overview and outlook for DMOs.
基金financially supported by the National Natural Science Foundation of China (20971072, 91122013, 90922032)the Fundamental Research Funds for the Central Universities
文摘A series of new lanthanide-radical complexes [{Ln（hfac）3}2（NITPhlM）2] （Ln = Nd （1）, Eu （2）, Tb （3）, Er （4）; hfac = hexafluoroacetylacetonate; NITPhlM = 2-[4-（1-imidazole）phenyl]-4,4,5,5-tetramethylimidazoline-l-oxyl-3-oxide） have been prepared and characterized. Single crystal X-ray diffraction analyses reveal that these complexes are isostructural with one-dimensional chain structures. These consist in Ln（hfac）3 units bridged by the paramagnetic ligands by the means of coor- dination of their nitronyl nitroxide groups and imidazole rings. Interestingly, each Ln ion is either bound to two nitronyl ni- troxide groups or to two imidazole units, and the different Ln centers alternate along the chain. Magnetic studies show that complex 3 exhibits a single-chain magnet behavior.
