MgFe2O4 nanoparticles were hydrothermally synthesized at 150 ℃ using iron nitrate [Fe(NO3)3·9H2O], magnesium nitrate [Mg(NO3)2·6H2O] and sodium hydroxide (NaOH) as starting materials by carefully controllin...MgFe2O4 nanoparticles were hydrothermally synthesized at 150 ℃ using iron nitrate [Fe(NO3)3·9H2O], magnesium nitrate [Mg(NO3)2·6H2O] and sodium hydroxide (NaOH) as starting materials by carefully controlling the reaction conditions. The influences of several factors such as presence or absence of Na+, molar ratio of Fe3+ / Mg2+, concentration of mental ions, temperature and reaction time on resultant products were investigated in the hydrothermal process. The sample was characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM), and its magnetic properties were measured using vibrating sample magnetometer (VSM).展开更多
将柠檬酸和Super P (SP)作为碳源用喷雾干燥技术制备出具有分级结构的类球形MgFe_2O_4/C (MFO/C)复合材料,使用场发射扫描电子显微镜(FESEM)、透射电子显微镜(TEM)、X射线粉末衍射仪(XRD)、X射线光电子能谱仪(XPS)和电化学测试等手段表...将柠檬酸和Super P (SP)作为碳源用喷雾干燥技术制备出具有分级结构的类球形MgFe_2O_4/C (MFO/C)复合材料,使用场发射扫描电子显微镜(FESEM)、透射电子显微镜(TEM)、X射线粉末衍射仪(XRD)、X射线光电子能谱仪(XPS)和电化学测试等手段表征了样品的形貌、结构和电化学性能。结果表明,在电流密度为0.5 C (500 mA·g^(-1))的条件下这种复合材料的首次放电比容量为1162.7 mAh·g^(-1),200次循环后比容量稳定在约734.5 mAh·g^(-1)。在电流密度为1C (1000 mA·g^(-1))条件下,200次循环后比容量仍保持在约580.4 mAh·g^(-1)。具有优异的循环和倍率性能的原因,可能是SP和柠檬酸分解生成的晶粒间碳形成了良好的导电网络,使材料的导电性提高并缓解了在连续充放电过程中活性物质的团聚和体积膨胀。展开更多
Nanocrystalline Magnesium ferrite has been prepared by chemical co-precipitation technique. Structural characterization has been performed by X-ray diffraction. Formation of ferrites has also been studied by using FTI...Nanocrystalline Magnesium ferrite has been prepared by chemical co-precipitation technique. Structural characterization has been performed by X-ray diffraction. Formation of ferrites has also been studied by using FTIR. Frequency dependence of real and imaginary part of initial permeability has been presented for the samples sintered at different temperatures. Real part of initial permeability, increases with the increase of grain growth. The loss component repre- sented by imaginary part of initial permeability decreases with frequency up to the measured frequency of this study of 13 MHz. Curie temperatures have been determined from the temperature dependence of permeability. Curie temperatures for the samples of this composition do not vary significantly with the variation of sintering temperatures. B-H loop measurements have been carried out by B-H loop tracer. Transport property measurements haven been carried out by electrometer and impedance analyzer.展开更多
Solid state reaction is a conventional method to synthesize structurally stable inorganic solids by mixing powdered reactants together at high pressure （over 1 x 105 mbar （1 mbar = 100 Pa）） and high temperature （...Solid state reaction is a conventional method to synthesize structurally stable inorganic solids by mixing powdered reactants together at high pressure （over 1 x 105 mbar （1 mbar = 100 Pa）） and high temperature （over 1300 K） [1-4]. This method is effective and sophisticated to prepare solid mate- rials, especially the functional complex oxides such as high temperature superconductors, piezoelectrics, dielectrics, etc. However, the chemical reactions cannot be intrinsically con- trolled and integrated at an atomic level in order to achieve the applications of future thin film devices with reduced dimensions [5]. With the desire of designing high-quality products with the micro/nanoscale integration, many pow- erful physical techniques, such as, pulsed-laser deposition （PLD）, molecular beam epitaxy （MBE）, sputtering deposi- tion, etc., have experienced enormous development due to their ability of lattice and/or interfacial controls. Using these growth techniques, layer-by-layer deposition （multilayer and/or superlattice） can be achieved, providing us a platform to tune the crystal structures at an atomic level by controlling the interfacial terminations and epitaxial strain, which are absent in their bulk counterparts [6-8]. From this point of view, well-controlled interfacial structures may also provide the solid state reaction at an atomic level during the physical depositions, which provides us an effective way to design the desired products from the chemical bonding reconstruction.展开更多
文摘MgFe2O4 nanoparticles were hydrothermally synthesized at 150 ℃ using iron nitrate [Fe(NO3)3·9H2O], magnesium nitrate [Mg(NO3)2·6H2O] and sodium hydroxide (NaOH) as starting materials by carefully controlling the reaction conditions. The influences of several factors such as presence or absence of Na+, molar ratio of Fe3+ / Mg2+, concentration of mental ions, temperature and reaction time on resultant products were investigated in the hydrothermal process. The sample was characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM), and its magnetic properties were measured using vibrating sample magnetometer (VSM).
文摘Nanocrystalline Magnesium ferrite has been prepared by chemical co-precipitation technique. Structural characterization has been performed by X-ray diffraction. Formation of ferrites has also been studied by using FTIR. Frequency dependence of real and imaginary part of initial permeability has been presented for the samples sintered at different temperatures. Real part of initial permeability, increases with the increase of grain growth. The loss component repre- sented by imaginary part of initial permeability decreases with frequency up to the measured frequency of this study of 13 MHz. Curie temperatures have been determined from the temperature dependence of permeability. Curie temperatures for the samples of this composition do not vary significantly with the variation of sintering temperatures. B-H loop measurements have been carried out by B-H loop tracer. Transport property measurements haven been carried out by electrometer and impedance analyzer.
基金supported by the National Natural Science Foundation of China(Grant Nos.51332001,11604011,and 11404016)the National Basic Research Program of China(Grant No.2014CB920902)Open Fund of State Key Laboratory of Information Photonics and Optical Communications(Beijing University of Posts and Telecommunications)(Grand No.2016B002)
文摘Solid state reaction is a conventional method to synthesize structurally stable inorganic solids by mixing powdered reactants together at high pressure （over 1 x 105 mbar （1 mbar = 100 Pa）） and high temperature （over 1300 K） [1-4]. This method is effective and sophisticated to prepare solid mate- rials, especially the functional complex oxides such as high temperature superconductors, piezoelectrics, dielectrics, etc. However, the chemical reactions cannot be intrinsically con- trolled and integrated at an atomic level in order to achieve the applications of future thin film devices with reduced dimensions [5]. With the desire of designing high-quality products with the micro/nanoscale integration, many pow- erful physical techniques, such as, pulsed-laser deposition （PLD）, molecular beam epitaxy （MBE）, sputtering deposi- tion, etc., have experienced enormous development due to their ability of lattice and/or interfacial controls. Using these growth techniques, layer-by-layer deposition （multilayer and/or superlattice） can be achieved, providing us a platform to tune the crystal structures at an atomic level by controlling the interfacial terminations and epitaxial strain, which are absent in their bulk counterparts [6-8]. From this point of view, well-controlled interfacial structures may also provide the solid state reaction at an atomic level during the physical depositions, which provides us an effective way to design the desired products from the chemical bonding reconstruction.
