Microbial mats, several millimeters thick and brown-yellow to white in color, were collected in hollow inside of chimney structure from Edmond hydrothermal field on the Central Indian Ridge. Microbes with shapes of ro...Microbial mats, several millimeters thick and brown-yellow to white in color, were collected in hollow inside of chimney structure from Edmond hydrothermal field on the Central Indian Ridge. Microbes with shapes of rod and helical stalk-like filaments were observed in the microbial mats, and are com- monly characterized by their cells completely encrusted by thick mineralized layers, made up of large amounts of amorphous silica and minor amounts of iron oxides. Transmission Electron Microscope observation has demonstrated that the acicular Fe-bearing matter was not only heterogenously dis- tributed on the surface of the cell wall, but also deposited in the inside of cell, suggesting that bio-precipitation of Fe had occurred both on the surface and in the interior of cell. Microbial silicification was also commonly found in the mats. Silica usually precipitated homogeneously on the surface of the microbes and forms micro-laminated layers, which might be controlled by the inorganic process of precipitation in hydrothermal environment. The biomineralization phenomenon in the mi- crobial mats showed that the precipitation of Fe and Si was closely related to microbes in hydrothermal environment. Considering that hydrothermal activities provided required chemical elements for miner- alization, it is suggested that this biomineralization process also might be driven by hydrothermal ac- tivities at the sea floor to some extent.展开更多
The mechanism of perpendicular magnetic anisotropy（PMA）in a MgO-based magnetic tunnel junction（MTJ）has been studied in this article.By comparing the magnetic properties and elementary composition analysis for diff...The mechanism of perpendicular magnetic anisotropy（PMA）in a MgO-based magnetic tunnel junction（MTJ）has been studied in this article.By comparing the magnetic properties and elementary composition analysis for different CoFeB-based structures,such as Ta/CoFeB/MgO,Ta/CoFeB/Ta and Ru/CoFeB/MgO structures,it is found that a certain amount of Fe-oxide existing at the interface of CoFeB/MgO is helpful to enhance the PMA and the PMA is originated from the interface of CoFeB/MgO.In addition,Ta film plays an important role to enhance the PMA in Ta/CoFeB/MgO structure.展开更多
To study the influence of CoFeB/MgO interface on tunneling magnetoresistance （TMR）, different structures of magnetic tunnel junctions （MTJs） are successfully prepared by the magnetron sputtering technique and char...To study the influence of CoFeB/MgO interface on tunneling magnetoresistance （TMR）, different structures of magnetic tunnel junctions （MTJs） are successfully prepared by the magnetron sputtering technique and characterized by atomic force microscopy, a physical property measurement system, x-ray photoelectron spectroscopy, and transmission electron microscopy. The experimental results show that TMR of the CoFeB/Mg/MgO/CoFeB structure is evidently improved in comparison with the CoFeB/MgO/CoFeB structure because the inserted Mg layer prevents Fe-oxide formation at the CoFeB/MgO interface, which occurs in CoFeB/MgO/CoFeB MTJs. The inherent properties of the CoFeB/MgO/CoFeB, CoFeB/Fe-oxide/MgO/CoFeB and CoFeB/Mg/MgO/CoFeB MTJs are simulated by using the theories of density functions and non-equilibrium Green functions. The simulated results demonstrate that TMR of CoFeB/Fe-oxide/MgO/CoFeB MTJs is severely decreased and is only half the value of the CoFeB/Mg/MgO/CoFeB MTJs. Based on the experimental results and theoretical analysis, it is believed that in CoFeB/MgO/CoFeB MTJs, the interface oxidation of the CoFeB layer is the main reason to cause a remarkable reduction of TMR, and the inserted Mg layer may play an important role in protecting Fe atoms from oxidation, and then increasing TMR.展开更多
通过对拉拉矿床矿物共生组合、矿物生成顺序、矿石特征的研究,发现其矿石矿物以磁铁矿为主,铁和铜的硫化物次之,并含有大量稀土矿物和自然金。拉拉矿床至少经历了两期成矿作用:早期为区域变质成矿作用,晚期为热液成矿作用。早期形成Fe R...通过对拉拉矿床矿物共生组合、矿物生成顺序、矿石特征的研究,发现其矿石矿物以磁铁矿为主,铁和铜的硫化物次之,并含有大量稀土矿物和自然金。拉拉矿床至少经历了两期成矿作用:早期为区域变质成矿作用,晚期为热液成矿作用。早期形成Fe REE P矿化,晚期为Cu Mo Au Co (U)矿化。根据这些特征,首次指出该矿床属于铁氧化物 铜 金 铀 稀土型矿床,而不是以往所称的块状硫化物型铜矿。展开更多
The design and fabrication of low-cost, high-effidency, and stable oxygen-evolving catalysts are essential for promoting the overall efficiency of water electrolysis. In this study, mesoporous Ni1-xFexOy （0 〈 x 〈 1...The design and fabrication of low-cost, high-effidency, and stable oxygen-evolving catalysts are essential for promoting the overall efficiency of water electrolysis. In this study, mesoporous Ni1-xFexOy （0 〈 x 〈 1, 1 〈y 〈 1.5） nanorods were synthesized by the facile thermal decomposition of Ni-Fe-based coordination polymers. These polymers passed their nanorod-like morphology to oxides, which served as active catalysts for oxygen evolution reaction （OER）. Increasing the Fe-doping amount to 33 at.% decreased the particle size and charge-transfer resistance and increased the surface area, resulting in a reduced overpotential （-302 mV） at 10 mA/cm^2 and a reduced Tafel slope （-42 mV/dec）, which were accompanied by a far improved OER activity compared with those of commercial RuO2 and IrO2 electrocatalysts. At Fe-doping concentrations higher than 33 at.%, the trend of the electrocatalytic parameters started to reverse. The shift in the dopant concentration of Fe was further reflected in the structural transformation from a NiO （〈33 at.% Fe） rock-salt structure to a biphasic NiO/NiFe204 （33 at.% Fe） heterostructure, a NiFe204 （66 at.% Fe） spinel structure, and eventually to α-fe203 （100 at.% Fe）. The efficient water-oxidation activity is ascribed to the highly mesoporous one-dimensional nanostructure, large surface area, and optimal amounts of the dopant Fe. The merits of abundance in the Earth, scalable synthesis, and highly efficient electrocatalytic activity make mesoporous Ni-Fe binary oxides promising oxygen-evolving catalysts for water splitting.展开更多
基金Supported by the National Natural Science Foundation of China (Grant Nos. 40532011, 40403004 and 40473032)
文摘Microbial mats, several millimeters thick and brown-yellow to white in color, were collected in hollow inside of chimney structure from Edmond hydrothermal field on the Central Indian Ridge. Microbes with shapes of rod and helical stalk-like filaments were observed in the microbial mats, and are com- monly characterized by their cells completely encrusted by thick mineralized layers, made up of large amounts of amorphous silica and minor amounts of iron oxides. Transmission Electron Microscope observation has demonstrated that the acicular Fe-bearing matter was not only heterogenously dis- tributed on the surface of the cell wall, but also deposited in the inside of cell, suggesting that bio-precipitation of Fe had occurred both on the surface and in the interior of cell. Microbial silicification was also commonly found in the mats. Silica usually precipitated homogeneously on the surface of the microbes and forms micro-laminated layers, which might be controlled by the inorganic process of precipitation in hydrothermal environment. The biomineralization phenomenon in the mi- crobial mats showed that the precipitation of Fe and Si was closely related to microbes in hydrothermal environment. Considering that hydrothermal activities provided required chemical elements for miner- alization, it is suggested that this biomineralization process also might be driven by hydrothermal ac- tivities at the sea floor to some extent.
基金supported by the National Defense Advance Research Foundation(No.9140A08XXXXXX0DZ106)the Basic Research Program of Ministry of Education,China(No.JY10000925005)+2 种基金the Scientific Research Program Funded by Shaanxi Provincial Education Department(No.11JK0912)the Scientific Research Foundation of Xi’an University of Science and Technology(No.2010011)the Doctoral Research Startup Fund of Xi’an University of Science and Technology(No.2010QDJ029)
文摘The mechanism of perpendicular magnetic anisotropy（PMA）in a MgO-based magnetic tunnel junction（MTJ）has been studied in this article.By comparing the magnetic properties and elementary composition analysis for different CoFeB-based structures,such as Ta/CoFeB/MgO,Ta/CoFeB/Ta and Ru/CoFeB/MgO structures,it is found that a certain amount of Fe-oxide existing at the interface of CoFeB/MgO is helpful to enhance the PMA and the PMA is originated from the interface of CoFeB/MgO.In addition,Ta film plays an important role to enhance the PMA in Ta/CoFeB/MgO structure.
基金Supported by the National Defense Advance Research Foundation under Grant No 9140A08XXXXXX0DZ106the Basic Research Program of Ministry of Education of China under Grant No JY10000925005+2 种基金the Scientific Research Program Funded by Shaanxi Provincial Education Department under Grant No 11JK0912the Scientific Research Foundation of Xi'an University of Science and Technology under Grant No 2010011the Doctoral Research Startup Fund of Xi'an University of Science and Technology under Grant No 2010QDJ029
文摘To study the influence of CoFeB/MgO interface on tunneling magnetoresistance （TMR）, different structures of magnetic tunnel junctions （MTJs） are successfully prepared by the magnetron sputtering technique and characterized by atomic force microscopy, a physical property measurement system, x-ray photoelectron spectroscopy, and transmission electron microscopy. The experimental results show that TMR of the CoFeB/Mg/MgO/CoFeB structure is evidently improved in comparison with the CoFeB/MgO/CoFeB structure because the inserted Mg layer prevents Fe-oxide formation at the CoFeB/MgO interface, which occurs in CoFeB/MgO/CoFeB MTJs. The inherent properties of the CoFeB/MgO/CoFeB, CoFeB/Fe-oxide/MgO/CoFeB and CoFeB/Mg/MgO/CoFeB MTJs are simulated by using the theories of density functions and non-equilibrium Green functions. The simulated results demonstrate that TMR of CoFeB/Fe-oxide/MgO/CoFeB MTJs is severely decreased and is only half the value of the CoFeB/Mg/MgO/CoFeB MTJs. Based on the experimental results and theoretical analysis, it is believed that in CoFeB/MgO/CoFeB MTJs, the interface oxidation of the CoFeB layer is the main reason to cause a remarkable reduction of TMR, and the inserted Mg layer may play an important role in protecting Fe atoms from oxidation, and then increasing TMR.
文摘通过对拉拉矿床矿物共生组合、矿物生成顺序、矿石特征的研究,发现其矿石矿物以磁铁矿为主,铁和铜的硫化物次之,并含有大量稀土矿物和自然金。拉拉矿床至少经历了两期成矿作用:早期为区域变质成矿作用,晚期为热液成矿作用。早期形成Fe REE P矿化,晚期为Cu Mo Au Co (U)矿化。根据这些特征,首次指出该矿床属于铁氧化物 铜 金 铀 稀土型矿床,而不是以往所称的块状硫化物型铜矿。
文摘The design and fabrication of low-cost, high-effidency, and stable oxygen-evolving catalysts are essential for promoting the overall efficiency of water electrolysis. In this study, mesoporous Ni1-xFexOy （0 〈 x 〈 1, 1 〈y 〈 1.5） nanorods were synthesized by the facile thermal decomposition of Ni-Fe-based coordination polymers. These polymers passed their nanorod-like morphology to oxides, which served as active catalysts for oxygen evolution reaction （OER）. Increasing the Fe-doping amount to 33 at.% decreased the particle size and charge-transfer resistance and increased the surface area, resulting in a reduced overpotential （-302 mV） at 10 mA/cm^2 and a reduced Tafel slope （-42 mV/dec）, which were accompanied by a far improved OER activity compared with those of commercial RuO2 and IrO2 electrocatalysts. At Fe-doping concentrations higher than 33 at.%, the trend of the electrocatalytic parameters started to reverse. The shift in the dopant concentration of Fe was further reflected in the structural transformation from a NiO （〈33 at.% Fe） rock-salt structure to a biphasic NiO/NiFe204 （33 at.% Fe） heterostructure, a NiFe204 （66 at.% Fe） spinel structure, and eventually to α-fe203 （100 at.% Fe）. The efficient water-oxidation activity is ascribed to the highly mesoporous one-dimensional nanostructure, large surface area, and optimal amounts of the dopant Fe. The merits of abundance in the Earth, scalable synthesis, and highly efficient electrocatalytic activity make mesoporous Ni-Fe binary oxides promising oxygen-evolving catalysts for water splitting.
