离子强度调控法合成Fe_3O_4/GO复合物的锂电性能

通过调控溶液中的离子强度,制备Fe_3O_4与氧化石墨烯的复合材料,该方法环境友好且简单。进一步研究Fe_3O_4/GO复合材料作为锂离子电池负极材料的性能,结果与Fe_3O_4纳米颗粒相比有着显着的改善。在电流密度为500mA/g时,充放电循环100次后,Fe_3O_4/GO复合材料的放电比容量仍有930mAh/g。     

Fe3O4@SiO2磁性复合微球的制备与表征

采用化学共沉淀法制备Fe_3O_4颗粒,在其制备过程中控制Fe_3O_4核的长大时间,加入油酸钠作为表面修饰剂来控制Fe_3O_4核的尺寸,然后加入正硅酸乙酯(TEOS)生成纳米级Fe_3O_4@SiO_2复合纳米粒子和亚微米级Fe_3O_4@SiO_2复合微球。通过X射线衍射、透射电镜、能谱分析和红外光谱分析证实Fe_3O_4颗粒表面包覆有SiO_2,并研究了复合粒子的形貌和成分组成,然后进行了磁性能分析。结果表明,Fe_3O_4纳米颗粒、Fe_3O_4@SiO_2复合纳米粒子和亚微米级Fe_3O_4@SiO_2复合微球的饱和磁化强度分别为79.95、34.85和61.51 A·m2/kg,对应的剩磁分别为1.73、1.05和3.07 A·m2/kg,矫顽力分别为1083、755和2002 A/m,亚微米级复合微球的剩磁和矫顽力都显著增大。     

不同形状纳米Fe_3O_4水基磁悬液对人工裂纹缺陷试块的磁粉检测

用两种不同的方法制备了球形及条形颗粒的Fe_3O_4磁悬液,并用X射线衍射(XRD)、透射电子显微镜(TEM)、扫描电子显微镜(SEM)分析测试手段对制备的样品进行了表征。将制备的两种形状的Fe_3O_4磁悬液用于对制作的裂纹试块进行磁粉检测。试验结果表明:在磁化过程中,纯球形纳米Fe_3O_4向缺陷漏磁场处聚集较快,裂纹显示清晰具体;撤走外加磁场后,受磁悬液的扰动,缺陷磁痕被破坏;使用纯球形纳米Fe_3O_4磁悬液所得缺陷磁痕显示不如使用条形纳米Fe_3O_4磁悬液所得磁痕显示清晰。     

Fe2O3在钛合金干滑动磨损及摩擦层形成中的作用

通过在Ti6Al4V合金滑动界面人工添加Fe_2O_3纳米颗粒及其与TiO_2、MoS_2的混合物,试图促进含Fe_2O_3摩擦层在室温下的快速形成;研究了Fe_2O_3、TiO_2、MoS_2在钛合金滑动过程中的作用,并探讨Fe_2O_3相对含量对钛合金磨损行为及磨损机制的影响。结果表明:干滑动下的Ti6Al4V合金耐磨性较差,磨面添加的TiO_2进一步加速磨损,MoS_2一定程度上降低了磨损但并不显著,而Fe_2O_3完全抑制磨损但增大了摩擦系数。高载下,富TiO_2、MoS_2颗粒并不能形成摩擦层,反而聚集在磨面犁沟或者凹坑处,而富Fe_2O_3则容易形成致密的摩擦层覆盖于磨损表面,这证实了钛合金高温耐磨性的改善是由于Fe_2O_3的出现。混合MoS_2+80%(质量分数)Fe_2O_3形成的摩擦层,兼具MoS_2的润滑性和Fe_2O_3的承载能力,给Ti6Al4V合金带来最佳的摩擦磨损性能。     

超顺磁性还原氧化石墨烯/Fe_3O_4空心球纳米复合材料的合成、表征及性能研究（英文）

采用一种简单有效的静电自组装的方法成功合成出还原氧化石墨烯包覆Fe_3O_4空心球纳米复合材料(r-GO/Fe_3O_4)。运用X射线粉末衍射(XRD)、扫描电子显微镜(SEM)、透射电子显微镜(TEM)、高分辨透射电镜(HRTEM)、红外-可见光谱(FT-IR)以及拉曼光谱等手段对合成出的产物进行了系统的表征。r-GO/Fe_3O_4纳米复合材料表现出优良的超顺磁性,室温下的饱和磁化强度高达70.2A·m~2·kg~(-1),并且在外加磁场下可以快速在水溶液中实现分散和分离。较高的饱和磁化强度和优良的水分散性使得这种新型的r-GO/Fe_3O_4纳米复合材料在包括磁共振成像、生物传感器、通信以及微波吸收等领域具有一定的应用价值。     

添加纳米氧化物颗粒对TC4合金磨损行为的影响

采用摩擦磨损试验机对TC4合金/GCr15钢进行滑动磨损试验,在摩擦界面人工添加纳米氧化物颗粒研究了氧化物种类和颗粒尺寸对TC4合金磨损行为的影响;采用XRD、SEM、EDS等方法表征了TC4合金的磨损特征并探讨了磨损机制。结果表明:氧化物颗粒的种类和尺寸对于TC4合金的磨损行为具有显著影响。TiO_2颗粒急剧促进TC4合金磨损,而Fe_2O_3显著降低磨损;Fe_2O_3粒径越小,TC4合金的磨损失重越小且几乎不随载荷变化而波动。摩擦界面添加TiO_2时,磨损机制与未添加氧化物颗粒的相似,以磨粒磨损和粘着磨损等严重磨损机制为主;当添加Fe_2O_3时,磨损机制由严重向轻微磨损转变。     

纳米铁粉Fe3O4含量对磁流变液正应力特性的影响

设计了测试磁流变液正应力性能的试验装置,搭建了相应的测试系统,通过实验来研究不同纳米级Fe_3O_4颗粒含量对传统磁流变液正应力的影响。实验结果表明,当电流在0~1.5 A,剪切速率给定时,当纳米Fe_3O_4粒子的质量分数从0%~7%变化时,微纳米磁流变液的正应力与传统磁流变液的正应力相比会随着纳米颗粒含量的增大而迅速增大;当磁感应强度在320 m T时,微纳米磁流变液的正应力将达到最大值,然而随着纳米粒子的质量分数从7%~16%变化时,微纳米磁流变的正应力逐渐降低。     

Bi修饰Fe_3O_4的可见光催化性能(英文)

利用水热法合成了Fe_3O_4负载的BiFeO_3。利用固体Fe_3O_4颗粒作为铁离子源,通过表面腐蚀和Bi3+离子在Fe_3O_4颗粒表面的吸附、沉淀,经过适当的处理,得到了不同负载量的BiFeO_3/Fe_3O_4复合可回收可见光催化剂。采用XRD、SEM、TEM表征了样品物相和形貌,用DRS(紫外漫反射光谱)和VSM(振动样品磁强计)表征样品的光吸收特性和磁性能。以刚果红(Congo Red)水溶液为探针,在可见光下(λ420 nm)测试了样品的光催化性能,表明样品具有一定的可见光响应,并随着Bi使用量的增加,可见光催化性能呈现明显增强的规律。     

静电自组装制备Fe2O3-PANI复合粒子的结构与性能

以十六烷基三甲基溴化铵对α-Fe_2O_3纳米颗粒进行表面修饰,控制体系pH值,将聚苯乙烯磺酸钠(PSS)掺杂的纳米聚苯胺(PANI)静电自组装在α-Fe_2O_3粒子表面,形成结构均匀的Fe_2O_3-PANI复合粒子.系统研究了体系的pH值、反应温度、反应时间等因素对复合粒子结构的影响,确定了形成结构均匀复合粒子的最佳工艺条件.应用TEM,XRD,FTIR和电化学工作站对复合粒子进行了结构和性能表征.循环伏安曲线和FTIR光谱分析结果表明,与PANI相比,Fe_2O_3-PANI复合粒子保持了PANI良好的电化学活性,红外吸收能力增强.     

NiFe_2O_4/SiO_2核壳结构纳米颗粒的制备及性能研究（英文）

采用微乳液法成功合成出以磁性铁氧体(NiFe_2O_4)为内核,以氧化硅(SiO_2)为壳层的纳米颗粒。NiFe_2O_4/SiO_2核壳结构纳米复合材料的形成过程是:将合成出的NiFe_2O_4纳米颗粒均匀分散正硅酸乙酯(TEOS)溶液中,然后对TEOS进行水解并在NiFe_2O_4纳米颗粒表面沉淀,将纳米颗粒分离出并进行后续热处理。通过XRD、IR、SEM、TEM等测试手段对纳米颗粒样品的显微组织结构进行了相应分析和观察。研究发现,纳米颗粒具有NiFe_2O_4/SiO_2核壳结构,其晶粒的平均直径大约为40 nm。采用振动样晶磁强计测试样品磁性能可发现纳米颗粒表现出典型的超顺磁性,其饱和磁化强度为12.97 emu·g~(-1)     

Synthesis of Graphene–Magnetite Nanoparticle Composite Using Mechanical Milling and Electrochemical Exfoliation

This work describes a two-step methodology for synthesizing a magnetite nanoparticle-graphene composite. In the first step, iron metal powder was ball milled with graphite to produce a mixture that was subsequently compacted to produce a pellet. In the second step, electrochemical exfoliation of this pellet was performed to produce graphene decorated with magnetite nanoparticles. Formation of graphene was established by methods such as x-ray diffraction, Raman spectroscopy, and x-ray photoelectron spectroscopy. The formation of magnetite nanoparticle-graphene composite was established by transmission-electron-microscopy-based imaging and electron diffraction methods. The magnetite nanoparticles on the graphene sheet had an average size of ~12 nm and were nonuniformly distributed.     

有机两相法制备巯基羧酸修饰的小尺寸贵金属纳米粒子

以生物相容性较好的巯基羧酸分子为保护剂、NaBH4为还原剂,采用有机两相法制备金属纳米粒子,实现了对纳米粒子的表面功能化。该方法制备的纳米材料粒径小(5 nm),单分散性好。讨论了巯基羧酸与金属前驱体之间的投料比、还原剂NaBH4的量以及巯基羧酸分子链长等因素对纳米粒子形貌的影响。除Au外,该方法还适用巯基羧酸对Ag、Pt和Pd等多种纳米粒子的表面修饰。     

Transition in the nanoporous structure of iron oxides during the oxidation of iron nanoparticles and nanowires

Changes in morphology during the oxidation of iron nanoparticles and nanowires in the temperature range 473–873 K have been studied by transmission electron microscopy. Iron nanoparticles and wires become hollow nanoparticles and nanotubes of magnetite at temperatures below 673 K as a result of vacancy aggregation during the oxidation process, resulting from the outward diffusion of iron ions through the magnetite layer. On the other hand, the hollow magnetite transforms into duplex porous structures with an interior nanopore and additional nanovoids at higher temperatures above 673 K, where the inner and outer diameters of magnetite nanotubes shrink and the phase transformation from magnetite to maghemite occurs. Transition in the porous structure seems to be related to the outward diffusion of vacancies from interior pore and the phase transformation from magnetite to maghemite.     

Direct transformation from goethite to magnetite nanoparticles by mechanochemical reduction

We present a novel method for synthesizing highly crystalline superparamagnetic magnetite (Fe₃O₄) nanoparticles (particle size about 15 nm) with relatively high saturation magnetization by direct transformation via ball-milling treatment from an amorphous goethite precipitate in a water system at room temperature. The obtained product was characterized by transmission electron microscopy, X-ray diffraction, and energy-dispersive X-ray spectroscopy; the particle size was measured by dynamic light scattering particle size analysis, and magnetic properties were measured by superconducting quantum interference device magnetometer. The mechanochemical effect induced by ball-milling treatment generates hydrogen gas, which contributes in reduction of part of the goethite, without addition of reducing agents, to give ferrous hydroxide. The mechanochemical effect also promotes solid-phase reaction between ferrous hydroxide and goethite to give magnetite, simultaneously crystallizing the formed magnetite nanoparticles while inhibiting particle growth with addition of neither heat nor additives such as surfactants and organic solvents. Thus, mechanochemical reduction provides an easy route for the synthesis of crystalline magnetite nanoparticles from ferric ion solution.     

Synthesis and characterization of CoFe2O4 nanoparticles

The reverse microemulsion composition consisting of 37.0% cyclohexane, 26.0% surfactant （TX-10 and AEO9）, 13.0% n-pentanol and 24.0% aqueous phase was investigated and chosen for the preparation of cobalt ferrite nanoparticles. Then silicon dioxide was coated onto the surface of the magnetite nanoparticles. The two kinds of nanoparticles were characterized by means of X-ray diffractometry（XRD）, scanning electron microscopy （SEM）, infrared spectroscopy （IR）, and energy dispersion spectrometry （SEM-EDS）. The SEM results indicate that both nanoparticles have narrow size distribution, less agglomeration and are in the size range of 10 -60 nm. XRD patterns show that there is not any peak detected except for the peaks of CoFe2O4, and imply that the coated silicon dioxide is amorphous. IR absorption spectra of the samples show the characteristic bands of Si—O—Si group and Fe—O group. SEM-EDS indicates that the molar ratio of Fe to Si is 96.11 ： 3.89. These results prove that a thin film of SiO2 is coated on the surface of the magnetite nanoparticles. And the characterization of cobalt ferrite nanoparticles prepared by conventional precipitation method are compared.     

The detection of genomic DNA from bacterial cells using iron oxide nanoparticles synthesized by a hydrothermal process

We used iron oxide nanoparticles in order to extract purified DNA from bacterial cells. Magnetite (Fe₃O₄) and maghemite (γ-Fe₂O₃) are synthesized with FeSO₄·7H₂O via a hydrothermal process and used as a medium to detect DNA. Various characterizations were performed including X-ray powder diffraction (XRD), high resolution transmission electron microscopy (HRTEM), field emission scanning electron microscopy, vibrating sample magnetometry, and Mössbauer spectroscopy. According to the XRD results, the XRD peaks of the synthesized magnetite and maghemite nanoparticles corresponded well with JCPDS standard data, respectively. The particle size of the iron oxide nanoparticles was about 20 nm, and the particle shape was almost spherical, which was confirmed by observation of the HRTEM image. The magnetite nanoparticles have a face-centeredcubic inverse spinel structure with a space group Fd \(\bar 3\) m, as confirmed by HRTEM and Mössbauer spectroscopy analyses. An agarose gel eletrophoresis analysis was performed to confirm the extraction ability of DNA using these iron oxide nanoparticles, revealing stronger reaction of the maghemite nanoparticles than the magnetite nanoparticles.     

Characterization of CO2 plasma-treated polyethylene surface bearing carboxylic groups

The surface modification of high density polyethylene by a CO₂ microwave plasma is described with the aim of fixing carboxylic groups. The characterization is discussed in terms of functionalization, degradation, crystallization and cross-linking. The formation of carboxylic acids seems mainly favored by the presence of the CO₂ active species. The degradation leading via chain scissions to the formation of volatile byproducts is shown to be heterogeneous by mainly affecting amorphous zones. The structural modification is associated with a twisting motion of macromolecular chains having defects to more organized conformations. Finally, cross-linking appears weak due to the absence of chromophoric sites and of VUV radiations in the plasma.     

Plasma functionalization of silicon carbide crystalline nanoparticles in a novel low pressure powder reactor

In order to functionalize silicon carbide nanopowders with carboxylic groups, an r.f. (13.56 MHz) low pressure plasma reactor has been developed so that particles can be stirred during the processing to try to coat them on their whole surface. Coatings in an O₂/hexamethyldisilazane (HMDSN) mixture have first been optimized on flat substrates; X-ray Photoelectron Spectroscopy (XPS) analysis showed that the O₂/HMDSN gas mixture resulted in a coating evolving from a polymer-like structure to a more inorganic SiO_x-like structure as the oxygen ratio increased. For a large O₂/HMDSN value, carboxylic groups were detected on the sample surface. Silicon carbide nanoparticles have then been plasma processed in such a reactive atmosphere. XPS, Time of Flight Secondary Ion Mass Spectroscopy (ToF-SIMS) and Transmission Electron Microscopy (TEM) analyses evidenced the surface modification of the processed powder and confirmed the grafting of carboxylic groups.     

Magnetic multiresonance behavior of Fe@Al2O3 nanoembedments and microstructural evolution during mechanosynthesis

The embedding of metal nanoparticles into an insulating ceramic matrix can provide encapsulation and prevent their oxidation and agglomeration. A nanoembedment powder with the Fe nanoparticles embedded into Al₂O₃ matrix is prepared by high-energy ball milling. Starting from the highly exothermic reactant mixture of magnetite and aluminum, Fe nanoparticles were in situ formed in Al₂O₃ matrix by mechanochemical reaction. It is found that a post-reaction milling significantly narrows the size distribution of Fe nanoparticles. The mechanism for the two-stage milling process was proposed. The microwave permeability of nanoembedments exhibited a multiresonance behavior, which was the evidence for monodispersed Fe nanoparticles. The Fe@Al₂O₃ nanoembedments are potential candidates as microwave absorber and left-handed materials.     

在有机添加剂存在的情况下共沉淀制备纳米Fe3O4及其性能

在有机添加剂甲基丙烯酸乙酯存在的情况下,采用共沉淀方法从Fe2 与Fe3 的水溶液中制备了Fe3O4纳米粒子.分别通过X射线衍射、透射电镜研究了其结构与形貌.结果表明:当溶液中甲基丙烯酸乙酯浓度为0.015 mol/L时,所制备的纳米粒子为单一的Fe3O4相;粒子呈球形,半径大约为15～30 nm.同时,采用振动样品磁强计对Fe3O4纳米粒子的磁性能进行了表征.结果显示,在不同温度下测得的M-H/T曲线与温度无关,表明该粒子具有典型的超顺磁性.