α-Fe_2O_3纳米立方体和纳米棒组装空心微球的可控合成及其磁学性能

在0.15mol/LCl-和0.05mol/LSO42-的存在下,通过Fe3 溶液140℃水热反应12h分别得到α-Fe2O3纳米立方体和α-FeOOH纳米棒自组装的微球,将得到的α-FeOOH纳米棒自组装微球经600℃热处理2h后转化为α-Fe2O3纳米棒组装空心微球.利用X射线衍射仪、扫描电子显微镜、透射电子显微镜和红外光谱对所得产物进行表征和分析.结果表明,所制备的单分散的α-Fe2O3纳米立方体为六方单晶结构,其边长为500nm.直径为2~4.5μm的空心微球是由直径约150nm的α-Fe2O3纳米棒组装而成.研究了Cl-和SO42-在纳米立方体和空心微球形成过程中的作用,提出了可能的生长机理.在室温下测试了α-Fe2O3纳米立方体和α-Fe2O3纳米棒自组装微球的磁学特性,其矫顽力和剩余磁化强度分别为2858.3Oe(1Oe=79.58A/m)和0.195emu·g-1(1emu·g-1=15.7914×10-9A·m2·kg-1),218.87Oe和0.071emu·g-1.     

α-Fe2O3纳米立方体和纳米棒组装空心微球的可控合成及其磁学性能

在0．15mol／L Clˉ和0．05mol／L SO4^2-的存在下,通过Fe^3＋溶液140℃水热反应12h分别得到α—Fe2O3纳米立方体和α-FeOOH纳米棒自组装的微球,将得到的α-FeOOH纳米棒自组装微球经600℃热处理2h后转化为α—Fe2O3纳米棒组装空心微球．利用X射线衍射仪、扫描电子显微镜、透射电子显微镜和红外光谱对所得产物进行表征和分析．结果表明,所制备的单分散的α-Fe2O3纳米立方体为六方单晶结构,其边长为500nm．直径为2～4．5μm的空心微球是由直径约150nm的α-Fe2O3纳米棒组装而成．研究了Clˉ和SO4^2-在纳米立方体和空心微球形成过程中的作用,提出了可能的生长机理．在室温下测试了α-Fe2O3纳米立方体和α-Fe2O3纳米棒自组装微球的磁学特性,其矫顽力和剩余磁化强度分别为2858.3 Oe（1 Oe=79．58 A／m）和0．195emu．g^-1（1 emu．g^-1=15．7914×10^-9 A·m^2·kg^-1）,218．87 Oe和0．071 emu．g^-1．     

一步水热法合成三种形貌纳米α-Fe2O3的机理及磁性能研究（摘要）

纳米α-Fe2O3以其优良的生物相容性、环境友好性、稳定性、催化性、以及磁性被广泛的应用于生物医学、颜料、催化、传感以及半导体等领域.为了实现不同形貌纳米α-Fe2O3的工业化可控合成,我们采用一步水热法,通过控制体系的反应时间,依次制备出了纺锤体状、管状和轮胎状的α-Fe2O3纳米结构,并利用X射线衍射仪、扫描电子显微镜和透射电子显微镜对产物进行了表征.体系中磷酸根离子在α-Fe2O3晶面上的特异性吸附是主导α-Fe2O3形貌演进的关键性因素.其作用主要体现在两个方面：一是使α-Fe2O3颗粒产生各向异性生长,形成纳米纺锤体;二是阻止某些晶面参与质子轰击反应,形成α-Fe2O3纳米管,进而促进体系中Fe4（PO4）3（OH）3相的形成与α-Fe2O3相的再结晶,最终形成轮胎状纳米结构.通过超导量子干涉仪对产物的磁性能表征,发现产物的不同形貌以及形状各项异性会对矫顽力、磁化强度以及低温磁性相变温度等磁学参量产生显著的影响.     

水热法制备SnO2/α-Fe2O3纳米复合材料

用α-Fe2O3纳米粒子作为前驱物,以SnC l4和NaOH作为反应试剂,通过简单的水热法制备了SnO2/α-Fe2O3纳米复合材料。SnO2/α-Fe2O3纳米复合材料具有有趣的形貌:直径约为20nm的SnO2纳米棒以α-Fe2O3纳米粒子为中心向四周辐射生长。利用X-ray粉末衍射(XRD),透射电镜(TEM)和扫描电镜(SEM)等测试手段对样品的成份、结构、形貌和尺寸进行了表征,初步探讨了SnO2/α-Fe2O3纳米复合材料的形成机理。     

前驱物热稳定性对氧化铁/氧化锡制备的影响

氧化铁纳米复合材料具有优越的磁学和催化性能,近年来在癌症诊断及治疗[1-3]、污染治理[4-6]、电磁屏蔽[7-8]等多个领域得到广泛研究.目前有许多研究集中于如何对复合材料的组成、结构和形貌进行设计合成,例如:利用机械球磨法将SnO2和α-Fe2O3粉体混合制备α-Fe2O3/SnO2 复合材料[9];通过共沉淀法将SnO2复合在α-Fe2O3 的表面[4];或者在Fe3O4表面复合一层C和相应的盐,然后通过煅烧制备Fe3O4/ZrO2和Fe3O4/TiO2微球[10-11].     

纳米化Fe2O3粉体的制备与表征

采用分析纯FeCl3·6H2O和NH3·H2O为主要原料,以均匀沉淀法制备了Fe2O3纳米粉体.通过X射线衍射(XRD)、红外光谱(IR)、扫描电子显微镜(SEM)及差热分析(DTA)等手段研究了热处理温度、分散剂、反应pH值对Fe2O3相变、结构、形貌及纳米属性的影响.结果表明:纳米化增大了Fe2O3的表面能,γ-Fe2O3转变为α-Fe2O3的温度仅为238.2 ℃,比常规粉体降低了约312 ℃;由于量子尺寸效应和表面效应,使用分散剂后α-Fe2O3纳米粉体的分散性、均匀性得到改善,粒径下降,Fe-O键伸缩及弯曲振动IR吸收频率发生蓝移;尤其是硬脂酸钠分散后α-Fe2O3的Fe-O伸缩、弯曲振动吸收频率分别蓝移11.57、10.93 cm-1;获得了液相均匀沉淀法制备Fe(OH)3纳米粉体的最佳工艺条件.     

Cu掺杂α-Fe2O3纳米粉体的掺杂量分析与X射线衍射研究

采用分析纯FeCl3·6H2O和NH3·H2O为主要原料,控制不同n(Cu2+)/n(Fe3+),利用均匀共沉淀法制备了Cu掺杂的α-Fe2O3纳米粉体.通过原子吸收光谱(AAS)和X射线衍射(XRD)分析了样品中Cu2+的掺杂量,并研究了掺杂对α-Fe2O3晶胞参数、晶粒度等的影响.结果表明,Cu掺杂α-Fe2O3仍为刚玉型结构,但晶胞参数a、b、c表现出增大趋势;Cu掺杂使α-Fe2O3晶体结构产生替位杂质缺陷,增大了α-Fe2O3的晶核生长活化能,使其晶粒度减小;随着Cu掺杂量的增大,α-Fe2O3的晶核生长活化能逐渐增大,晶粒度逐渐减小.该研究为α-Fe2O3半导体材料的性能及应用研究提供了指导.     

醋酸钾溶液体系中α-Fe_2O_3纳米微球的离子液体辅助合成及气敏性能研究

以Fe Cl3·6H2O和CH3COOK为反应物,以离子液体1-丁基-3-甲基咪唑氯化物([Bmim]Cl)为结构导向剂和表面活性剂,采用水热合成法在150℃反应8 h制备出结晶度好、形貌规整,直径为10~30 nm的α-Fe2O3纳米微球.考察了[Bmim]Cl的添加量对氧化铁形貌和气敏性能的影响.气敏性能测试结果表明:当离子液体添加量为12 mmol时,α-Fe2O3纳米微球对乙醇的气敏性能最佳.在工作温度为300℃时,对50μL/L乙醇的灵敏度达到7.56,是不添加离子液体时制备的α-Fe2O3的5.6倍,在10~200μL/L的检测范围内灵敏度与浓度具有良好的线性关系(R=98.8%),并且具有良好的选择性和稳定性.本文还详细探讨了α-Fe2O3纳米微球对乙醇的敏感机理,以及工作温度对其气敏性能的影响.     

Fe/SBA-3介孔组装体系及其磁特性

用不同的实验工艺制备了一组Fe/SAB-3 介孔复合体系.X射线衍射表明,Fe/SAB-3具有六方排列的孔道结构.通过N2吸附实验可知,这种材料具有极高的比表面积.从傅立叶红外光谱可证实,Fe3＋进入了SAB-3的骨架.样品磁测量结果表明,与通常的α-Fe2O3纳米颗粒相比,纳米Fe/SAB-3介孔复合体系中的纳米α-Fe2O3 粒子的矫顽力（Hc）从1765 Oe下降到87 Oe,比饱和磁化强度（Ms）增加了75.4％.     

单分散α-Fe_2O_3纳米结构空心亚微球的制备及表征

采用一种新的溶液生长法结合多步包覆法在自制的不同粒径SiO2单分散亚微球表面包覆不同厚度的β-FeOOH涂层,得到单分散β-FeOOH/SiO2核壳结构亚微球.实验结果表明,SiO2核心颗粒尺寸对表面涂层的形态和包覆均匀性有很大影响.当SiO2核心颗粒的平均粒径为250 nm左右时,β-FeOOH表面涂层均匀,颗粒间团聚较少,一次包覆后涂层厚度约为35 nm.涂层中β-FeOOH纳米棒的尺寸随着所选SiO2核心颗粒粒径的增大而相应增大.经多次包覆能够显著提高涂层的厚度,3次包覆后β-FeOOH表面涂层厚约100 nm.β-FeOOH/SiO2核壳结构亚微球与质量分数5%的NaOH溶液反应后,于600℃焙烧2 h得到了单分散α-Fe2O3空心微球.单分散α-Fe2O3空心亚微球表层是由α-Fe2O3纳米棒搭建而成的三维网络结构,α-Fe2O3纳米棒的尺寸与核壳结构中β-FeOOH纳米棒的尺寸基本一致.     

One-step synthesis of SnO2 and TiO2 hollow nanostructures with various shapes and their enhanced lithium storage properties

A versatile one-step method for the general synthesis of metal oxide hollow nanostructures is demonstrated. This method involves the controlled deposition of metal oxides on shaped α-Fe(2)O(3) crystals which are simultaneously dissolved. A variety of uniform SnO(2) hollow nanostructures, such as nanococoons, nanoboxes, hollow nanorings, and nanospheres, can be readily generated. The method is also applicable to the synthesis of shaped TiO(2) hollow nanostructures. As a demonstration of the potential applications of these hollow nanostructures, the lithium storage capability of SnO(2) hollow structures is investigated. The results show that such derived SnO(2) hollow structures exhibit stable capacity retention of 600-700?mA h g(-1) for 50?cycles at a 0.2?C rate and good rate capability at 0.5-1?C, perhaps benefiting from the unique structural characteristics.     

γ-Fe(2)O(3) and Fe(3)O(4) magnetic hierarchically nanostructured hollow microspheres: Preparation, formation mechanism, magnetic property, and application in water treatment

In this paper, we report the preparation of γ-Fe(2)O(3) and Fe(3)O(4) magnetic hierarchically nanostructured hollow microspheres by a solvothermal combined with precursor thermal conversion method. These γ-Fe(2)O(3) and Fe(3)O(4) magnetic hierarchically nanostructured hollow microspheres were constructed by three-dimensional self-assembly of nanosheets, forming porous nanostructures. The effects of experimental parameters including molar ratio of reactants and reaction temperature on the precursors were studied. The time-dependent experiments indicated that the Ostwald ripening was responsible for the formation of the hierarchically nanostructured hollow microspheres of the precursors. γ-Fe(2)O(3) and Fe(3)O(4) magnetic hierarchically nanostructured hollow microspheres were obtained by the thermal transformation of the precursor hollow microspheres. Both γ-Fe(2)O(3) and Fe(3)O(4) hierarchically nanostructured hollow microspheres exhibited a superparamagnetic property at room temperature and had the saturation magnetization of 44.2 and 55.4emu/g, respectively, in the applied magnetic field of 20 KOe. Several kinds of organic pollutants including salicylic acid (SA), methylene blue (MB), and basic fuchsin (BF) were chosen as the model water pollutants to evaluate the removal abilities of γ-Fe(2)O(3) and Fe(3)O(4) magnetic hierarchically nanostructured hollow microspheres. It was found that γ-Fe(2)O(3) hierarchically nanostructured hollow microspheres showed a better adsorption ability over SA than MB and BF. However, Fe(3)O(4) hierarchically nanostructured hollow microspheres had the best performance for adsorbing MB.     

Ellipsoidal hollow nanostructures assembled from anatase TiO2 nanosheets as a magnetically separable photocatalyst

A simple approach was proposed to synthesize three types of ellipsoidal hollow nanostructures whose shells are assembled from anatase TiO(2) nanosheets (NSs) with exposed (001) facets. Among them, ellipsoid Fe(3)O(4)@TiO(2)-NS nanorattles can be readily generated as a magnetically separable photocatalyst with enhanced activity through in situ reduction of the α-Fe(2)O(3) core.     

Fe3O4的X射线微结构特征与催化活性间的关系

湿法工艺制备的不同晶型Fe2O3, 经水煤气还原后Fe3O4的X射线衍射微结构特征, 用分析微应变和晶粒尺寸的Voigt函数单峰分析法进行了测定。Fe3O4微应变大小同催化活性间存在一种对应关系。γ-Fe2O3还原的Fe3O4比α型还原的有更大的晶格畸变, 在325℃, 500空速条件下, CO转化率达97%以上, 比后者高出30%多。这种畸变结构在工业催化反应条件下能长期稳定, 但经600℃高温处理后, 畸变减小,活性下降。湿法工艺可以获得具有不同活性的Fe3O4前身, γ-Fe2O3与Fe3O4晶体结构上的类似, 使它在还原过程中, 能把这种高活性的结构状态保留下来。     

Formation and transformation kinetics of amorphous iron(III) oxide during the thermally induced transformation of ferrous oxalate dihydrate in air

Focusing on the formation and transformation of amorphous Fe(2)O(3) in the course of the thermally induced transformations of ferrous oxalate dehydrate in air, the kinetics and physico-geometric mechanisms of the respective reaction steps were investigated systematically by means of thermoanalytical methods, complemented by other techniques. The final product of α-Fe(2)O(3) is produced by heating the sample to 700 K via intermediates of poorly crystalline anhydrous FeC(2)O(4) and amorphous Fe(2)O(3), where the external shape and size of the original sample particles are retained during the overall course of reactions. The initial parts of all the three distinguished reaction steps, that is, thermal dehydration of crystalline water, oxidative decomposition of anhydrous FeC(2)O(4) and crystallization of amorphous Fe(2)O(3), are controlled kinetically by the formation or reconstruction of the surface product layers. The surface product layers play important roles of regulating the physico-geometric kinetic behavior of the established parts of the reactions. The oxidative decomposition of intermediate anhydrous FeC(2)O(4), characterized as the formation process of amorphous Fe(2)O(3), arrests in the final stage of the reaction. The as-produced amorphous Fe(2)O(3), protected probably by the outer shell of the surface product layer and the residual anhydrous FeC(2)O(3), crystallizes to α-Fe(2)O(3) being induced by the surface crystallization. Aiming to contribute notably toward provision of the establishment of the novel fabrication routes of nanosized iron oxides by the controlled crystallization of amorphous Fe(2)O(3), the possible factors controlling and/or affecting the formation and transformation kinetics of amorphous Fe(2)O(3) were discussed.     

一种新型纺锤状α-Fe_2O_3纳米晶的合成、表征及其表面性能(英文)

合成了一种新型的具有单晶结构的α-Fe2O3纳米晶(NFO-1).在我们的合成方法中,样品的形貌和结构在低反应浓度体系中运用无机盐和有机模板进行双重调控,同时用溶剂挥发诱导自组装(EISA)来加速反应和在不改变形貌结构的前提下获得高产率样品.所得α-Fe2O3纳米晶的形貌和结构对其表面修饰功能有明显的影响,NFO-1因其特殊的纺锤状形貌而与表面功能试剂(多巴胺)之间的化学作用有明显的增强.并且,本文所描述的合成方法同样适用于其他过渡金属氧化物纳米单晶的合成.我们预期,这种方法可为新型纳米材料的合成提供新的途径.     

High-density arrays of InGaN nanorings, nanodots, and nanoarrows fabricated by a template-assisted approach

Dense, crystalline arrays of InGaN nanorings, nanodots, and nanoarrows have been fabricated on GaN substrates by template-assisted nano-area selective growth. To create the nanostructures, we have used nanoporous anodic alumina films as templates to pattern nanopores in an SiO2 transfer layer, and then used this patterned SiO2 layer as a template for nitride growth by metalorganic chemical vapor deposition. We have varied the diameter of the deposited nitride nanostructures from 35 to 250 nm by changing the initial anodic alumina template structure. In addition, by controlling the nitride growth time we have created various types of nanostructures, from nanorings to nanoarrows. This structural evolution begins with the nucleation and formation of a nanoring structure, followed by coalescence and growth to form faceted nanodots, and finally lateral overgrowth to form faceted nanoarrows.     

α-Fe2O3 nanotubes with superior lithium storage capability

Polycrystalline α-Fe(2)O(3) nanotubes with thin walls have been synthesized by one-step template-engaged precipitation of Fe(OH)(x) followed by thermal annealing. In virtue of the unique structural features, these α-Fe(2)O(3) nanotubes exhibit superior lithium storage capabilities with exceptional high-rate capacity retention as a potential anode material for lithium-ion batteries.     

Al掺杂α-Fe2O3材料的制备、表征和气敏特性

采用均相沉淀法制备了纯α-Fe2O3(300 ℃煅烧)和Al掺杂α-Fe2O3(300和400 ℃煅烧), 使用SEM, XRD, ICP和红外光谱等手段进行表征, 并利用气敏仪测试无水乙醇和90＃汽油在不同条件下对材料的响应性能. 结果表明, 微量Al掺杂不改变α-Fe2O3材料的物相, 但会阻碍晶粒生长, 使颗粒变小及Fe2O3晶格间隙中的铁原子数目增多, 材料的导电率增大, 从而显著提高材料的气敏性能. Al掺杂α-Fe2O3对乙醇的响应性能优于对汽油的响应性能, 在乙醇气氛中, 材料对湿度仍然不敏感. 经400 ℃煅烧的Al掺杂α-Fe2O3稳定性较好, 可作为检测乙醇气体的半导体气敏材料.     

Reaction products and kinetics of the reaction of NO2 with γ-Fe2O3

The reaction of NO(2) with Fe(2)O(3) has relevance for both atmospheric chemistry and catalysis. Most studies have focused on hematite, α-Fe(2)O(3), as it is the thermodynamic stable state of iron oxide; however, other forms of Fe(2)O(3) naturally occur and may have different chemistries. In this study, we have investigated the reaction products and kinetics for NO(2) reacting with γ-Fe(2)O(3) powder using diffuse reflectance infrared Fourier transform spectroscopy and compared the results to those of previous studies of NO(2) reacting with α-Fe(2)O(3). Both α- and γ-Fe(2)O(3) produce surface-bound nitrate at the pressures examined in this study (24-212 mTorr); surface-bound nitrite products are observed at all pressures for γ-Fe(2)O(3) whereas nitrite was only observed on α-Fe(2)O(3) at lower pressures. Surface-bound NO(+) and Fe-NO products are observed on γ-Fe(2)O(3), which have not been observed with α-Fe(2)O(3). The reaction kinetics show a first-order dependence on NO(2) pressure and this is used to support the hypothesis of unimolecular reaction of adsorbed NO(2) with the γ-Fe(2)O(3) surface as the slow step in the reaction mechanism. The difference in product formation between NO(2) reacting with γ-Fe(2)O(3) and previous studies of α-Fe(2)O(3) illustrate the fact that care must be taken in generalizing reactivity of different polymorphs.