共沉淀法制备超细微Fe3O4

采用共沉淀法制备了超细微Fe3O4粉体,以氨水作为沉淀剂,加入到Fe2＋和Fe3＋的混合溶液中,制得Fe3O4粉体粒子．为了使Fe3O4颗粒的分散良好,加入少量油酸．通过扫描电镜、X射线衍射和红外光谱谱图等进行表征、分析,证明由该法所制得的Fe3O4粒子形貌为球形,分散较好．     

Kinetics of Fe3O4 formation by air oxidation

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.     

半金属Fe3O4薄膜的磁控溅射制备及磁电学性能研究

利用交流磁控溅射法,在H2中采用Fe3O4靶材,成功制备了(111)取向的Fe3O4薄膜.对薄膜样品进行XRD测试,研究不同衬底温度对成相的影响.对薄膜表面的XPS测试结果表明所制备薄膜为单相Fe3O4沉积过程中随H2量增大,薄膜表面粗糙度有显著增加.对薄膜进行磁学性能的测试,饱和磁化强度高达5 000Oe,反映了反相晶粒边界(APBs)的存在.Tv以下较低的晶格对称度导致了矫顽场的增大.薄膜的电阻随温度变化曲线(R-T)显示115K附近出现Verwey相变,对R-T曲线的拟和结果显示,Fe3O4薄膜在40～300K温度区间为电子的变程跳跃VRH(Variable range hopping)导电机制.     

草酸溶解Fe_3O_4的动力学模拟与反应机理

大气气溶胶中含铁的矿物在铁的生物地球化学循环中起着重要作用。Fe3O4是气溶胶中一类重要的含铁矿物。采用分光光度法测定Fe3O4在草酸中的溶解特征,分析Fe3O4溶解的速率控制机理并对溶解Fe3O4进行动力学模拟。结果表明,草酸溶解铁的过程可能是受运移和表面反应综合制约的溶解动力学过程,其他动力学模拟结果表明,草酸溶解Fe3O4控制机理比较复杂。     

盐酸羟胺还原法制备Fe3O4/Au磁性纳米复合微粒

Fe3O4/Au磁性纳米复合微粒由于具有一些奇异的物理特征而被广泛的应用于各个领域。因此,有关磁性纳米复合颗粒的制备已成为目前的一个研究热点。实验中用还原法制备了Fe3O4/Au纳米复合微粒,通过扫描电子显微镜对其表面形貌进行了观测,结果表明,制备的FeO/Au纳米复合微粒呈球形,颗粒间没有明显团聚,大小均匀,分散性好。     

铁磁性Fe3O4负载TiO2纳米粒子的制备表征及光催化活性

以FeSO4·7H2O和Degussa P25型TiO2(P25 TiO2)为原料,通过原位生长法制备了具有高催化活性及铁磁性的Fe3O4负载TiO2催化剂(Fe3O4/TiO2).采用高分辨透射电镜(HR-TEM),X射线衍射仪(XRD)和振动样品磁强计(VSM)对所得催化剂的结构和性能进行了表征.紫外光催化降解乙酸溶液的结果表明,Fe3O4/TiO2的催化活性是P25 TiO2的3倍左右.基于上述研究,构建了新型磁性定位光催化体系,通过对弱酸性黄G溶液催化降解的研究,表明即使在无搅拌的状态下,该复合粒子也具有较高的光催化活性,并且可以通过外界磁场有效地分离并加以回收利用,是较为理想的光催化剂.     

Surface Modfication of Fe3O4 Nanoparticles

Nanometer particles are important portion of magnetic fluid. Fe3O4 magnetic nanoparticles were studied in this paper and the surface modification of Fe3O4 nanoparticles was investigated by a series of experiments. Fe3O4 magnetic nanoparticles were synthesized with pH value, temperature, and the dosage of surfactant. The phase, structure, size and magnetism of nanoparticles were tested by X-ray diffration （XRD）, transmission electron microscopy （TEM） and magnetic balance. On the basis of the surface modification coating mechanism, the experimental phenomena and the effects on the variation of size, magnetism and stability of Fe3O4 nanoparticles were theoretically analyzed. X-Ray diffraction spectrum and TEM photograph show that 1） the nanoparticles structure is perfect, 2） the diameter of narnoparticles is small and have good deliquescence, and 3） Sodium oleate is the anion surfactant. Therefore 1） the good condition of surface modification is in an acidic solution, 2） the best temperature of surface modification is at 80 ℃, and 3） the dosage of surfactant should be about 0.6 times of that of Fe^2＋.     

Fe3O4磁流变流体的粘度特性研究

叙述了磁流变流体的磁变效应(Magnetorhelogical Effect,简称MRE),以及Fe3O4磁流变流体的粘度特性实验.以实验为例,对磁流变流体的粘度特性进行研究.介绍有关实验的细节及结果.     

MnO2热分解制备Mn3O4的动力学研究

为了得到MnO2热分解制备Mn3O4的动力学方程,用TG/DTA和XRD研究MnO2的热分解过程。研究表明MnO2的分解是分步进行的,4MnO2=2Mn2O3 O2↑的动力学方程为G(α)=[-ln(1-α)]12(T<625℃)和G(α)=[-ln(1-α)]13(T≥625℃),表观活化能为90.239 kJ/mol;6Mn2O3=4Mn3O4 O2↑的动力学方程为G(α)=[-ln(1-α)]13,表观活化能为204.67 kJ/mol;两个过程属于晶核形成与增长控制过程。     

纳米Fe_3O_4粒子的制备及表面包覆

采用化学共沉淀法和氧化沉淀法制备磁性纳米Fe3O4粒子,并用柠檬酸三钠为表面活性剂包覆制备纳米Fe3O4粒子,同时利用包覆磁性粒子制备水基纳米磁性液体。对两种方法制备的纳米Fe3O4粒子的晶体结构、微观形貌及化学共沉淀法制备的Fe3O4在包覆前后等电点的变化进行了表征。结果表明,化学共沉淀法制备的纳米Fe3O4粒子平均粒径约为20 nm且分布比较均匀,表面活性剂包覆后,等电点由原来的pH=6.70移向pH=2.35,证实了Fe3O4粒子表面被柠檬酸离子所包覆,且制得的磁性液体的稳定性比较高;而氧化沉淀法制备Fe3O4纳米粒子粒径分布是从几十纳米到上百纳米,制得的磁性液体出现很明显的团聚。     

磁性纳米TiO2/Fe3O4复合材料的制备及光催化降解性能

采用均匀沉淀法在Fe3O4表面包覆TiO2,制备新型纳米TiO2/ Fe3O4光催化材料,并通过改变pH值、温度、TiO2/Fe3O4的比例和硫酸钛浓度等得到材料制备的最佳条件.用X射线衍射分析了复合颗粒的形态结构及包覆情况.通过可溶性染料活性艳红X-3B的降解反应,考察了光催化活性.结果表明,用最佳条件制备的复合材料对活性艳红的脱色率达97.12%.光降解动力学结果表明:对活性艳红X-3B染料的光催化降解反应符合一级反应动力学.     

Ag3PO4/Fe3O4/GO复合催化剂的制备及其可见光催化性能

以氧化石墨烯（GO）为基底,利用共沉淀及离子交换两步法制备Ag₃PO₄/Fe₃O₄/GO 复合光催化剂．通过X射线衍射（XRD）、扫描电子显微镜（SEM）、透射电镜（TEM）、热重（TGA）、振动样品磁强计（VSM）及紫外-可见光谱（UV-Vis DRS, UV-4100,带积分球）对样品的特征基团、微观形貌及磁性质、光学性质等进行了鉴定和表征．光催化脱色实验结果表明：Ag₃PO₄/Fe₃O₄/GO 化剂20 min内对10 mg/L罗丹明B模拟水样的脱色率可达97.6%,高于Ag₃PO₄（73.4%）;Ag₃PO₄/Fe₃O₄/GO 系中引入过硫酸钠可以起到强化光催化性能的作用;另外,Ag₃PO₄/Fe₃O₄/GO 剂表现出良好的活性稳定性、热稳定性及结构稳定性。     

Fe3O4磁流体的水热法制备与表征

采用水热法制备了水基Fe3O4磁流体,利用X衍射仪(XRD)和透射电镜(TEM)对磁粒子的组成、结构及粒径进行了分析,利用古埃磁天平研究了磁流体的饱和磁化强度和稳定性,证实所制得的磁粒子为纯相Fe3O4纳米粒子,平均粒径为9nm左右,磁流体饱和磁化强度为46mT,稳定性较好。     

微乳法制备Fe3O4磁性纳米粒子的研究

首先对油包水（W／O）型微乳液进行了制备研究，利用拟三元相图探明了一定条件下的W／O型微乳液中的最佳体系。进而利用此W／O型微乳液作为“微反应器”制备Fe3O4纳米粒子。采用TEM、XRD和IR对所制备的Fe3O4纳米粒子进行了分析表征。     

纳米Fe_3O_4/Co_3O_4催化H_2O_2氧化降解亚甲基蓝

纳米四氧化三钴(Co3O4)催化剂对废水中有机物具有良好的催化降解活性,但纳米催化剂难从溶液中分离的缺点限制了其应用.通过将不同量的纳米Co3O4催化剂自组装在纳米四氧化三铁(Fe3O4)上,制备出了一系列不同纳米Co3O4催化剂含量的纳米Fe3O4/Co3O4,并将该系列纳米Fe3O4/Co3O4用于双氧水(H2O2)氧化降解亚甲基蓝的反应来测试其催化性能和回收再利用性能.实验结果表明,尽管纳米Co3O4催化剂的含量对于纳米Fe3O4/Co3O4的催化性能有所影响,但该系列纳米Fe3O4/Co3O4相对纯纳米Co3O4催化剂仍表现出很好的催化活性和回收再利用性.     

Surface Organic Modification of Fe3O4 Magnetic Nanoparticles

The surface organic modification of Fe3O4 nanoparticles with silane coupling reagent KH570 was studied.The modified and unmodified nanoparticles were characterized by FT-IR,XPS and TEM.The spectra of FT-IR and XPS revealed that KH570 was coated onto the surface of Fe3O4 nanoparticles to get Fe-O-Si bond and an organic coating layer also was formed.Fe3O4 nanoparticles were spheres partly with mean size of 18.8 nm studied by TEM,which was consistent with the result 17.9 nm calculated by Scherrer'S equation.KH570 was adsorbed on surface and formed chemistry bond to be steric hindrance repulsion which prevented nanoparticles from reuniting.Then glycol-based Fe3O4 magnetic liquids dispersed stably was gained.     

磁性高分子微球Fe3O4／PMMA的制备与表征

以油酸作为表面活性剂,采用化学共沉淀法制备了具有良好晶型、分散性好的纳米四氧化三铁。以甲基丙烯酸甲酯（MMA）作为反应单体,DVB为交联剂,使用水溶性引发剂KPS,采用单体聚合法制备磁性高分子微球Fe30dPMMA,该磁性高分子微球具有明显的核壳结构,粒子尺寸约为500nm。     

Modification of Fe3O4 Magnetic Nanoparticles by L-dopa or Dopamine as an Enzyme Support

Fe3O4 magnetic nanoparticles were prepared by co-precipitation of Fe2+ and Fe3+ in an ammonia solution,and its size was about 36 am measured by an atomic force microscope.Fe3O4 magnetic nanopanicles were modified by L-dopa or dopamine using sonication method.The analysis of FTIR clearly indicated the formation of Fe-O-C bond.Direct immobilization of trypsin(EC:3.4.21.4)on Fe3O4 magnetic nanoparticles with L-dopa and dopamine spacer was investigated using glutaraldehyde as a coupling agent.No significant changes in the size and magnetic property of the three kinds of magnetic nanoparticles linked with or without trypsin were observed.The existence of the spacer molecule on magnetic nanoparticles could greatly improve the activity and the storage stability of bound trypsin through increasing the flexibility of enzyme and changing the microenvironment on nanoparticles surface compared to the naked magnetic nanoparticles.     

Fe_3O_4/SiO_2复合粒子的制备及对Cd~(2+)的吸附性能研究

采用共沉淀法制备出粒径为10nm左右、具有超顺磁性的Fe3O4纳米粒子,在Fe3O4纳米粒子外包覆SiO2合成了磁性Fe3O4/SiO2复合粒子,研究了该复合粒子对水溶液中Cd2+离子的吸附性能.利用透射电子显微镜(TEM)、X射线衍射仪(XRD)、红外光谱(FTIR)、振动样品磁强计(VSM)和原子吸收分光光度计(AAS)对样品进行表征,考察了SiO2不同包覆量对吸附剂吸附性能的影响.结果表明:随着SiO2包覆量的增大,SiO2壳层厚度增大,内核中包埋的Fe3O4粒子数量增多,Fe3O4/SiO2复合粒子尺寸随着增大,由50nm左右增大到300 nm左右;Fe3O4纳米粒子表现出了良好的磁性能,比饱和磁化强度达73.6A·m2·kg-1,Fe3O4/SiO2复合粒子的比饱和磁化强度随SiO2包覆量的增大而逐渐减小;Fe3O4/SiO2复合粒子的吸附率随着SiO2包覆量的增多而逐渐增大,最大吸附率为91.0%.     

SiO2/Fe2O3复合颜料的制备工艺

在Fe2O3颗粒的悬浮液中以硅酸钠为硅源,稀盐酸调节反应体系的pH值,合成SiO2-Fe2O3核-壳粒子.研究Fe2O3表面包覆SiO2的影响因素,确定最优改性剂和改性条件.采用XRD、SEM对表面改性前后的Fe2O3进行表征,用酸溶率评价包膜效果.以硅酸钠作为硅源,在反应温度85℃、pH值为9~10、改性时间为2 h时,制备出SiO2-Fe2O3复合颜料.包覆后的Fe2O3的耐温性和耐酸性显著提高,干粉耐温性达到1000℃.