H2O2氧化法制备Fe3O4纳米颗粒及与共沉淀法制备该样品的比较

在近中性条件下，利用H₂Ｏ₂氧化Fe(OH)2胶体成功制备了Fe₃ Ｏ₄纳米颗粒.分别利用透射电镜(TEM)，x射线衍射仪(XRD)，振动样品磁强计(VSM)和超导量子干涉仪（SQUI D）对样品的形貌，结构，宏观磁性进行了表征和测量.TEM图像表明样品为球形颗粒，直径 大小约18nm，且分布较均匀.XRD结果表明样品为立方尖晶石结构.穆斯堡尔谱测量表明样品 室温下对应两套六线谱，样品的晶体结构存在缺陷，内磁场略小于块体Fe₃Ｏ4的值. 宏观磁测量表明样品的饱和磁化强度可达67×10^-3A·m²/g，在20 K出现了Verw ey转变.选择该法制备的Fe₃Ｏ₄纳米颗粒与共沉淀法得到的样品作 了磁性比较.宏观磁 测量表明共沉淀法制备的样品在外磁场为1T时仍未饱和，磁化强度仅为46×10^-3A·m²/g，在178K出现了超顺磁转变温度，且在测量温度范围内没有发现Verwe y转变. 关键词： 亚铁磁 超顺磁 穆斯堡尔谱     

双金属化合物[Ni(en)2]3[Fe(CN)6]2·2H2O的变温穆斯堡尔谱研究

合成了一维绳梯链状双金属化合物[Ni(en)2]3[Fe(CN)6]2·2H2O,并对其变温穆斯堡尔谱进行了研究,结果表明该分子磁体中铁的电子态为低自旋Fe3 ,而大的四极分裂值(QS)表明此化合物的[Fe(CN)6]3-单元对称结构发生了形变,低温时出现的磁弛豫谱,给出了在该温度点附近出现铁磁耦合相互作用的信息。     

CoFe2O4纳米颗粒的结构、磁性以及离子迁移

聚乙烯醇(PVA)溶胶凝胶法制备出CoFe2O4纳米微粉,用X 射线衍射研究了铁氧体纳米颗粒的结构.测量了CoFe2O4纳米颗粒80-873 K的变温穆斯堡尔谱,发现纳米颗粒的磁转变温度范围为793-813 K,比块体材料的磁性转变温度要低.CoFe2O4纳米颗粒的德拜温度θA=674 K,θB=243 K,比块体材料要小.CoFe2O4纳米颗粒超精细场Hf随温度的变化符合T3/2+T5/2定理.当温度较高时,平均同质异能移IS随温度的升高而减小,并呈线性关系.     

CoFe2O4纳米颗粒的结构、磁性以及离子迁移

聚乙烯醇(PVA)溶胶凝胶法制备出CoFe₂O₄纳米微粉，用X射线衍射研究了铁氧体纳米颗粒的结构.测量了CoFe₂O₄纳米颗粒80—873 K的变温穆斯堡尔谱，发现纳米颗粒的磁转变温度范围为793—813 K，比块体材料的磁性转变温度要低.CoFe₂O₄纳米颗粒的德拜温度θ_A=674 K，θ_B=243 K，比块体材料要小.CoFe₂O₄纳米颗粒超精细场H_f随温度的变化符合T^3/2+T^5/2定理.当温度较高时，平均同质异能移IS随温度的升高而减小，并呈线性关系. 关键词： 纳米颗粒 磁性 穆斯堡尔谱     

纳米SnO2材料的穆斯堡尔谱研究

通过X射线衍射,透射电子显微镜和穆斯堡尔谱测量,确定了在本研究中用水热法制备的半导体SnO₂材料为纳米材料,实验给出该材料的结构特点和Sn原子核的超精细参量,并发现600℃时纳米的SnO₂会转变成晶态大颗粒的SnO₂。 关键词：     

EuBa2Cu3O7的化学键性质和穆斯堡尔谱研究

利用电介质的平均能带模型计算了ＥｕＢａ２Ｃｕ３Ｏ７的化学键参数,得到Ｃｕ（１）－Ｏ键的平均共价性为０．４１４,Ｃｕ（２）－Ｏ键的平均共价性为０．２８１,应用由共价性和极化率定义的化学环境因子计算了＾５７Ｆｅ、＾１１９Ｓｎ在ＥｕＢａ２Ｃｕ３Ｏ７中的穆斯堡尔同质异能位移,确定了＾５７Ｆｅ、＾１１９Ｓｎ的价态和占位情况。     

高TC GdBa2 Cu3O7—δ中Fe的结合强度与氧配位

本文对不同氧浓度的GdBa₂(Cu_1－xFe_x)₃O_7—δ系(其中x=0.005－0.001)进行了温度范围从20K到300K的⁵⁷Fe穆斯堡尔谱分析.处于正交相的谱具有四条四极双线,其中三条来自Cu(1)位,而具有最小四极分裂值的一条来自Cu(2)位.从各谱线相对强度对温度的依赖关系,可得Cu(1)位置上不同区域的德拜温度.织构样品用来分析各四极双线的极化情况.以幻角测量时,可Cu(1)位的振动各向异性(Goldanskii-Karyagin Effect).Cu(1)位上最大的四极分裂双线表明其具有最低的德拜温度和最强的振动各向异性.     

非晶Fe89.7 P10.3合金纳米线阵列的磁性研究

利用电化学沉积方法在阳极氧化铝模板中制备了Fe89.7P10.3非晶合金纳米线阵列.利用x射线衍射仪、透射电子显微镜、振动样品磁强计和穆斯堡尔谱仪研究了样品的结构和磁性,发现纳米线阵列是非晶结构,且拥有垂直磁各向异性和高的矫顽力,Hc=3.04×104A/m.纳米线内部的平均超精细场和平均同质异能移分别为2.15×106 A/m和0.07 mm/s;而纳米线末端的平均超精细场(2.33×106A/m)大于内部的值,平均同质异能移(0.04mm/s)小于内部的值.另外,纳米线内部Fe原子磁矩与线轴的夹角约为16°,而在纳米线末端Fe原子磁矩与线轴的夹角约为28°.这些结果表明,由于形状各向异性,在纳米线中实现了无序非晶合金磁矩的有序排列.     

Sono-assisted preparation of highly-efficient peroxidase-like Fe3O4 magnetic nanoparticles for catalytic removal of organic pollutants with H2O2

Fe₃O₄ magnetic nanoparticles (Fe₃O₄ MNPs) with much improved peroxidase-like activity were successfully prepared through an advanced reverse co-precipitation method under the assistance of ultrasound irradiation. The characterizations with XRD, BET and SEM indicated that the ultrasound irradiation in the preparation induced the production of Fe₃O₄ MNPs possessing smaller particle sizes (16.5 nm), greater BET surface area (82.5 m² g^?1) and much higher dispersibility in water. The particle sizes, BET surface area, chemical composition and then catalytic property of the Fe₃O₄ MNPs could be tailored by adjusting the initial concentration of ammonia water and the molar ratio of Fe²⁺/Fe³⁺ during the preparation process. The H₂O₂-activating ability of Fe₃O₄ MNPs was evaluated by using Rhodamine B (RhB) as a model compound of organic pollutants to be degraded. At pH 5.4 and temperature 40 °C, the sonochemically synthesized Fe₃O₄ MNPs were observed to be able to activate H₂O₂ and remove ca. 90% of RhB (0.02 mmol L^?1) in 60 min with a apparent rate constant of 0.034 min^?1 for the RhB degradation, being 12.6 folds of that (0.0027 min^?1) over the Fe₃O₄ MNPs prepared via a conventional reverse co-precipitation method. The mechanisms of the peroxidase-like catalysis with Fe₃O₄ MNPs were discussed to develop more efficient novel catalysts.     

Mechanisms of effective gold shell on Fe3O4 core nanoparticles formation using sonochemistry method

Sonochemical synthesis (sonochemistry) is one of the most effective techniques of breaking down large clusters of nanoparticles (NPs) into smaller clusters or even individual NPs, which ensures their dispersibility (stability) in a solution over a long duration. This paper demonstrates the potential of sonochemistry becoming a valuable tool for the deposition of gold (Au) shell on iron oxide nanoparticles (Fe₃O₄ NPs) by explaining the underlying complex processes that control the deposition mechanism. This review summarizes the principles of the sonochemistry method and highlights the resulting phenomenon of acoustic cavitation and its associated physical, chemical and thermal effects. The effect of sonochemistry on the deposition of Au NPs on the Fe₃O₄ surface of various sizes is presented and discussed. A Vibra-Cell ultrasonic solid horn with tip size, frequency, power output of ½ inch, 20 kHz and 750 W respectively was used in core@shell synthesis. The sonochemical process was shown to affect the surface and structure of Fe₃O₄ NPs via acoustic cavitation, which prevents the agglomeration of clusters in a solution, resulting in a more stable dispersion. Deciphering the mechanism that governs the formation of Au shell on Fe₃O₄ core NPs has emphasized the potential of sonication in enhancing the chemical activity in solutions.     

多孔SiO2包裹磁性纳米颗粒Fe3O4的制备与表征

采用加热分解油酸铁法制备了Fe₃O₄磁性纳米颗粒,并用有机模板和反相微乳液相结合的方法将磁性纳米颗粒包裹在多孔二氧化硅中.用红外光谱(FTIR)研究了不同的处理方式对油酸铁表面官能团的影响及油酸的反应浓度和加热分解油酸铁的过程中升温速率对Fe₃O₄纳米颗粒的影响.结果表明,用乙醇和丙酮处理后的固态蜡状油酸铁表面的油酸基团会受到损害,将不利于加热分解时形成单分散性的Fe₃O₄纳 关键词： 3O₄纳米颗粒')" href="#">Fe₃O₄纳米颗粒 2包裹')" href="#">多孔SiO₂包裹 反相微乳液法 油酸铁     

Dynamics of H2O molecules in ferroelectric K4Fe(CN)6 · 3H2O

The infrared spectrum of potassium ferrocyanide trihydrate has been recorded both in the para and ferroelectric phases. From a combined study of the IR and Raman spectra, it is concluded that there are two sets of water molecules present in the lattice, one set being involved in stronger hydrogen bonding than the other. The ferroelectric transition appears to be associated with an ordering of the water dipoles.     

Growth and characterization of Fe3O4 nanoparticles in silica matrix

Nano-magnetic Fe₃O₄ particles coated with silica are synthesized. The study of structural and magnetic properties was carried out using X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and vibrating sample magnetometer (VSM) techniques. The VSM results show that these kinds of composite particles exhibit superparamagnetic behavior with zero coercivity and remanence. The magnetic spheroid alumina carriers containing these magnetic composite particles were prepared by an internal gelation process. The SiO₂ coatings prevent the reaction between Fe₃O₄ and Al₂O₃ during the sintering process and maintain the superparamagnetic behavior of the catalyst carriers.     

Electrostatic self-assembly of Fe3O4 nanoparticles on carbon nanotubes

Carbon nanotubes (CNTs)-based magnetic nanocomposites can find numerous applications in nanotechnology, integrated functional system, and in medicine owing to their great potentialities. Herein, densely distributed magnetic Fe₃O₄ nanoparticles were successfully attached onto the convex surfaces of carbon nanotubes (CNTs) by an in situ polyol-medium solvothermal method via non-covalent functionalization of CNTs with cationic surfactant, cetyltrimethylammonium bromide (CTAB), and anionic polyelectrolyte, poly(sodium 4-styrenesulfonate) (PSS), through the polymer-wrapping technique, in which the negatively charged PSS-grafted CNTs can be used as primer for efficiently adsorption of positively metal ions on the basis of electrostatic attraction. X-ray diffractometry (XRD), X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM) analysis have been used to study the formation of Fe₃O₄/CNTs. The Fe₃O₄/CNTs nanocomposites were proved to be superparamagnetic with saturation magnetization of 43.5 emu g^?1. A mechanism scheme was proposed to illustrate the formation process of the magnetic nanocomposites.     

Magnetically induced controlled release from glucose-modified liposomes loaded with Fe3O4 nanoparticles

Journal of Nanoparticle Research - Nd–Fe–B magnetic materials were prepared using the binary alloy method with addition of Ho nanopowder to grain boundaries to improve the magnetic,...     

Size-controlled synthesis of Fe2O3 and Fe3O4 nanoparticles onto zeolite by means of a modified activated-coprecipitation method: effect of the HCl concentration during the activation

Tubular nanofibers (TNFs) of vanadium pentoxide (V₂O₅) were synthesized by electrospinning technique using a single spinneret for the first time by controlling the properties of the precursor solution. A partially miscible polymeric solution of vanadium oxytrihydroxide [VO(OH)₃] was produced by hydrolysis of vanadyl acetylacetonate in Poly(vinylpyrrolidone) (PVP). The phase-separated polymer solution formed the core of the electrospun fibers whereas the VO(OH)₃ formed the shell; the core PVP has been removed by controlled heat treatment. The TNFs had an inner diameter ~60?nm and wall thickness ~±100?nm. The capacitive behavior of the V₂O₅ TNFs was studied using cyclic voltammetry and galvanostatic cycling techniques. The studies showed ideal stable supercapacitive characteristics in the electrospun V₂O₅ TNFs.