目的探讨葡聚糖包裹的超顺磁性Fe_3O_4纳米颗粒(dextran-coated superparamagnetic iron oxides nanoparticles,dextrarr/SPlONP)作为间质注射的MRI造影剂的可行性。方法应用界面共沉淀法,制备dextran/SPIONP,用透射电镜、能谱分析、X...目的探讨葡聚糖包裹的超顺磁性Fe_3O_4纳米颗粒(dextran-coated superparamagnetic iron oxides nanoparticles,dextrarr/SPlONP)作为间质注射的MRI造影剂的可行性。方法应用界面共沉淀法,制备dextran/SPIONP,用透射电镜、能谱分析、X射线衍射、红外光谱测试、热重分析等方法对dextran/SPlONP的大小、磁性能等进行表征,并研究葡聚糖对SPlONP的影响。然后,将dextran/SPIONP稀释成不同剂量,兔舌粘膜下问质注射后的不同时间段,切取前哨淋巴结,行核磁共振波谱分析,确定dextran/SPIONP的最适剂量和最佳检测时间。结果dextran/SPION的平均直径为6～9nm,其表征与经典的共沉淀法制备的颗粒一致,具有超顺磁性,葡聚糖是影响SPIONP饱和磁化强度的主要因素。dextran/SPIONP用于间质注射的最适剂量为含铁量20μmol,最佳检测时间为注射后24h。结论用界面共沉淀法制备的dextran/SPIONP是一种适用于间质注射的MRI造影剂。展开更多
A uniform, dense and defect free Cr2O3 thin film, which is amorphous at ambient temperature, was applied on the surface of intermetallic Fe3Al by electrodeposition reaction sintering, and the effect of this film on th...A uniform, dense and defect free Cr2O3 thin film, which is amorphous at ambient temperature, was applied on the surface of intermetallic Fe3Al by electrodeposition reaction sintering, and the effect of this film on the oxidation of Fe3Al at 900 ℃ in air was studied. The films and the oxide scales were analyzed by TEM, EDAX,SEM and XRD.It is proved that, by surface applied Cr2O3 thin film,a continuous, protective,fine grained α-Al2O3 scale was formed on Fe3Al. As a result, the adherence of the scale and oxidation resistance of Fe3Al were improved.展开更多
The effects of addition of chromium or boron on room temperature tensile properties,fracture behavior and susceptibility to test environments (air vs. vacuuwi of forged Fe3Al have been investigated. The results indica...The effects of addition of chromium or boron on room temperature tensile properties,fracture behavior and susceptibility to test environments (air vs. vacuuwi of forged Fe3Al have been investigated. The results indicated that both chromium and boron result in increasing room temperuture ductility and fracture strength of the Fe3Al alloy whether tested in air or in vacuum. The susceptibility to test envimnment was described with the embrittlement index I: I=(δv-δA)/δv. The embrittlement indexes, for Fe-30Al, Fe-30Al-4Cr and Fe-30Al-0. 13B (at. %), are 24%, 37% and 29%,respectively. Scanning electron microscope examination of fracture surface revealed that the fracture mode of the three alloys remains unchanged, and all of them exhibited a transgranular cleavage fracture mode when tested in vacuum or air.展开更多
The kinetics of Fe3O4 formation by air oxidation of slightly acidic suspension of Fe（OH）2 was studied. The effects of initial concentration of Fe（Ⅱ）, temperature, partial pressure of oxygen, air flow rate and sti...The kinetics of Fe3O4 formation by air oxidation of slightly acidic suspension of Fe（OH）2 was studied. The effects of initial concentration of Fe（Ⅱ）, temperature, partial pressure of oxygen, air flow rate and stirring rate on the oxidation rate were investigated. The results show that Fe3O4 formation is composed of two-step reaction, the first step is the formation of Fe（OH）+2 by oxidation of Fe（OH）+ complex ions, the second step is the formation of magnetite by dehydration and deprotonation of Fe（OH）+ and Fe（OH）+2. The oxidation reaction is zero-order with respect to the concentration of Fe（Ⅱ） and around 0.5-order with respect to partial pressure of oxygen, and oxygen transfer process is rate-limiting step of oxidation reaction with apparent activation energy of 2.74 kJ·mol-1.展开更多
Electrochemical water treatment is an attractive technology for water desalination and softening due to its low energy consumption. Especially, capacitive Deionization(CDI) is promising as a future technology for wate...Electrochemical water treatment is an attractive technology for water desalination and softening due to its low energy consumption. Especially, capacitive Deionization(CDI) is promising as a future technology for water treatment. Graphene(rGO) has been intensively studied for CDI electrode because of its advantages such as excellent electrical conductivity and high specific surface area. However, its 2D dimensional structure with small specific capacitance, high resistance between layers and hydrophobicity degrades ion adsorption efficiency. In this work, we successfully prepared uniformly dispersed Fe3O4/rGO nanocomposite by simple thermal reactions and applied it as effective electrodes for CDI. Iron oxides play a role in uniting graphene sheets, and specific capacitance and wettability of electrodes are improved significantly;hence CDI performances are enhanced. The hardness removal of Fe3O4/rGO nanocomposite electrodes can reach 4.3 mg/g at applied voltage of 1.5V, which is 3 times higher than that of separate r GO electrodes.Thus this material is a promising candidate for water softening technology.展开更多
The effect of alloying element such as Mo,Si or B and its stoichoimetric composition on the tensile properties at room and elevated temperatures,and also on the microstructure of Fe_3Al and FeAl alloys has been invest...The effect of alloying element such as Mo,Si or B and its stoichoimetric composition on the tensile properties at room and elevated temperatures,and also on the microstructure of Fe_3Al and FeAl alloys has been investigated.Two Fe aluminides were found to be obviously strengthened by all of three elements,but seriously embrittled by Mo and Si.An improvemen over the plasicity of FeAl may be made by adding B,and the fracture surface is variedfrom intergranular to transgranular cleavage type.The room temperature plasticity of the Fe-rich Fe_3Al or Al-rich FeAl is much better than that of the stoichoimetric aluminides.An anoma- lous temperature dependence on the yield strength of Fe_3Al in range of 400 to 500℃ or of FeAl in range of 400 to 500℃ was found.Discussion has been carried out by the aspect of microstructure.展开更多
Proper addition of 0.002 wt-% Mg to cast Fe_3Al alloy may obviously improve the room and high temperature tensile properties.Auger spectra show that Mg segregates near grain boundaries as very thin layers.Observation ...Proper addition of 0.002 wt-% Mg to cast Fe_3Al alloy may obviously improve the room and high temperature tensile properties.Auger spectra show that Mg segregates near grain boundaries as very thin layers.Observation under TEM reveals that a suitable amount of Mg enhances ability of cooperative internal deformation so that the dislocations will ease the con- tinuous slip deformation through grain boundaries.The fracture feature of Fe_3Al alloy is of transgranular cleavage at room temperature and cracks initiate at grain boundaries.展开更多
Small amount(0.5-0.8at.%) of niobium addition to the multicomponent alloys based on Fe3Al(Fe-28Al-5Cr-0.5Mo-0.05Zr-0.05B-0.1Ce) results in the microstructural refinement and the increase in the yield strength at tempe...Small amount(0.5-0.8at.%) of niobium addition to the multicomponent alloys based on Fe3Al(Fe-28Al-5Cr-0.5Mo-0.05Zr-0.05B-0.1Ce) results in the microstructural refinement and the increase in the yield strength at temperatures up to 600℃,but is not beneficial to room temperature ductility.Results of microanalysis indicate that the addition of niobium causes the formation of precipitates with complex compositions which strengthen both matrix and grain boundaries and enhance the creep resistance of the alloys.展开更多
文摘目的探讨葡聚糖包裹的超顺磁性Fe_3O_4纳米颗粒(dextran-coated superparamagnetic iron oxides nanoparticles,dextrarr/SPlONP)作为间质注射的MRI造影剂的可行性。方法应用界面共沉淀法,制备dextran/SPIONP,用透射电镜、能谱分析、X射线衍射、红外光谱测试、热重分析等方法对dextran/SPlONP的大小、磁性能等进行表征,并研究葡聚糖对SPlONP的影响。然后,将dextran/SPIONP稀释成不同剂量,兔舌粘膜下问质注射后的不同时间段,切取前哨淋巴结,行核磁共振波谱分析,确定dextran/SPIONP的最适剂量和最佳检测时间。结果dextran/SPION的平均直径为6～9nm,其表征与经典的共沉淀法制备的颗粒一致,具有超顺磁性,葡聚糖是影响SPIONP饱和磁化强度的主要因素。dextran/SPIONP用于间质注射的最适剂量为含铁量20μmol,最佳检测时间为注射后24h。结论用界面共沉淀法制备的dextran/SPIONP是一种适用于间质注射的MRI造影剂。
文摘A uniform, dense and defect free Cr2O3 thin film, which is amorphous at ambient temperature, was applied on the surface of intermetallic Fe3Al by electrodeposition reaction sintering, and the effect of this film on the oxidation of Fe3Al at 900 ℃ in air was studied. The films and the oxide scales were analyzed by TEM, EDAX,SEM and XRD.It is proved that, by surface applied Cr2O3 thin film,a continuous, protective,fine grained α-Al2O3 scale was formed on Fe3Al. As a result, the adherence of the scale and oxidation resistance of Fe3Al were improved.
文摘The effects of addition of chromium or boron on room temperature tensile properties,fracture behavior and susceptibility to test environments (air vs. vacuuwi of forged Fe3Al have been investigated. The results indicated that both chromium and boron result in increasing room temperuture ductility and fracture strength of the Fe3Al alloy whether tested in air or in vacuum. The susceptibility to test envimnment was described with the embrittlement index I: I=(δv-δA)/δv. The embrittlement indexes, for Fe-30Al, Fe-30Al-4Cr and Fe-30Al-0. 13B (at. %), are 24%, 37% and 29%,respectively. Scanning electron microscope examination of fracture surface revealed that the fracture mode of the three alloys remains unchanged, and all of them exhibited a transgranular cleavage fracture mode when tested in vacuum or air.
文摘The kinetics of Fe3O4 formation by air oxidation of slightly acidic suspension of Fe（OH）2 was studied. The effects of initial concentration of Fe（Ⅱ）, temperature, partial pressure of oxygen, air flow rate and stirring rate on the oxidation rate were investigated. The results show that Fe3O4 formation is composed of two-step reaction, the first step is the formation of Fe（OH）+2 by oxidation of Fe（OH）+ complex ions, the second step is the formation of magnetite by dehydration and deprotonation of Fe（OH）+ and Fe（OH）+2. The oxidation reaction is zero-order with respect to the concentration of Fe（Ⅱ） and around 0.5-order with respect to partial pressure of oxygen, and oxygen transfer process is rate-limiting step of oxidation reaction with apparent activation energy of 2.74 kJ·mol-1.
基金supported by international cooperation program for science and technology funded by the Ministry of Science,ICT&Future Planning(NRF-2014K1A3A1A09063208)
文摘Electrochemical water treatment is an attractive technology for water desalination and softening due to its low energy consumption. Especially, capacitive Deionization(CDI) is promising as a future technology for water treatment. Graphene(rGO) has been intensively studied for CDI electrode because of its advantages such as excellent electrical conductivity and high specific surface area. However, its 2D dimensional structure with small specific capacitance, high resistance between layers and hydrophobicity degrades ion adsorption efficiency. In this work, we successfully prepared uniformly dispersed Fe3O4/rGO nanocomposite by simple thermal reactions and applied it as effective electrodes for CDI. Iron oxides play a role in uniting graphene sheets, and specific capacitance and wettability of electrodes are improved significantly;hence CDI performances are enhanced. The hardness removal of Fe3O4/rGO nanocomposite electrodes can reach 4.3 mg/g at applied voltage of 1.5V, which is 3 times higher than that of separate r GO electrodes.Thus this material is a promising candidate for water softening technology.
文摘The effect of alloying element such as Mo,Si or B and its stoichoimetric composition on the tensile properties at room and elevated temperatures,and also on the microstructure of Fe_3Al and FeAl alloys has been investigated.Two Fe aluminides were found to be obviously strengthened by all of three elements,but seriously embrittled by Mo and Si.An improvemen over the plasicity of FeAl may be made by adding B,and the fracture surface is variedfrom intergranular to transgranular cleavage type.The room temperature plasticity of the Fe-rich Fe_3Al or Al-rich FeAl is much better than that of the stoichoimetric aluminides.An anoma- lous temperature dependence on the yield strength of Fe_3Al in range of 400 to 500℃ or of FeAl in range of 400 to 500℃ was found.Discussion has been carried out by the aspect of microstructure.
文摘Proper addition of 0.002 wt-% Mg to cast Fe_3Al alloy may obviously improve the room and high temperature tensile properties.Auger spectra show that Mg segregates near grain boundaries as very thin layers.Observation under TEM reveals that a suitable amount of Mg enhances ability of cooperative internal deformation so that the dislocations will ease the con- tinuous slip deformation through grain boundaries.The fracture feature of Fe_3Al alloy is of transgranular cleavage at room temperature and cracks initiate at grain boundaries.
文摘Small amount(0.5-0.8at.%) of niobium addition to the multicomponent alloys based on Fe3Al(Fe-28Al-5Cr-0.5Mo-0.05Zr-0.05B-0.1Ce) results in the microstructural refinement and the increase in the yield strength at temperatures up to 600℃,but is not beneficial to room temperature ductility.Results of microanalysis indicate that the addition of niobium causes the formation of precipitates with complex compositions which strengthen both matrix and grain boundaries and enhance the creep resistance of the alloys.
