纳米Fe3 O4 颗粒的正电子湮没谱学研究

测量了磁性纳米Fe₃O₄颗粒的X射线衍射谱(XRD)、正电子湮没寿命谱(PALS)和符合多普勒展宽谱(CDBS),研究了不同压力和退火温度对磁性纳米Fe₃O₄颗粒物相、电子结构、缺陷及电子动量分布等的影响. XRD,PALS,CDBS测量结果表明:纳米Fe₃O₄颗粒的缺陷浓度随压力的增加而增大,但物相和缺陷类型并未发生变化;磁性纳米Fe₃O_{4< 关键词： 正电子 3}O₄')" href="#">Fe₃O₄ 寿命谱 多普勒展宽谱     

La掺杂对Bi4Ti3O12薄膜铁电性能的影响

利用Sol-Gel法在Pt/Ti/SiO₂/Si衬底上制备出Bi₄Ti₃O₁₂和Bi_3.25La_0.75Ti₃O₁₂薄膜，研究了La掺杂对Bi₄Ti₃O₁₂薄膜的晶体结构、铁电性能和疲劳特性的影响，发现La掺杂没有改变Bi₄Ti₃O₁₂薄膜的基本晶体结构，并且提高了Bi₄Ti₃O₁₂铁电薄膜的剩余极化值和抗疲劳性能，对La掺杂改善Bi₄Ti₃O₁₂铁电薄膜性能的机理进行了讨论. 关键词： 铁电性能 4Ti₃O₁₂薄膜')" href="#">Bi₄Ti₃O₁₂薄膜 3.25La_0.75Ti₃O₁₂薄膜')" href="#">Bi_3.25La_0.75Ti₃O₁₂薄膜 sol-gel法 La掺杂     

SrBi2Ta2O9/Bi4Ti3O12复合铁电薄膜的制备与特性研究

采用溶胶凝胶工艺在p-Si衬底上制备了SrBi₂Ta₂O₉/Bi₄Ti₃O₁₂复合铁电薄膜. 研究了SrBi₂Ta₂O₉/Bi₄Ti₃O₁₂复合薄膜的微观结构与生长行为、铁电性能和疲劳特性. 研究表明: Si衬底Bi₄Ti< 关键词： 2Ta₂O₉')" href="#">SrBi₂Ta₂O₉ 4Ti₃O₁₂')" href="#">Bi₄Ti₃O₁₂ 复合铁电薄膜 溶胶凝胶工艺     

用于α-Al2O3分子动力学模拟的长程Finnis-Sinclair势函数

用金属势函数描述氧化物是实现金属-氧化物界面分子动力学模拟的关键.基于此,通过拟合α-Al₂O₃的晶格能、晶格常数、弹性常数,获得了一套用于描述α-Al₂O₃的长程Finnis-Sinclair（F-S）势.通过与已报道的描述α-Al₂O₃的EAM势、Glue势和modified Matsui（m-Matsui）势的比较,结果达到或优于前人的结果.进而,在300 K的温度下对 关键词： 长程F-S势 2O₃')" href="#">α-Al₂O₃ 2O₃界面')" href="#">Fe-Al₂O₃界面 2O₃界面')" href="#">Al-Al₂O₃界面     

纳米结构CoxFe3-xO4多孔微球的磁性及交换偏置效应研究

用乙二醇为溶剂,用三氯化铁、二氯化钴和醋酸铵为起始反应试剂,通过溶剂热反应首次合成了纳米结构Co_xFe_3-xO₄多孔微球.用X射线衍射仪(XRD)、透射电子显微镜(TEM)和扫描电子显微镜(SEM)表征样品的结构和形貌,结果表明,所制备的单分散Co_xFe_3-xO₄多孔微球为立方多晶结构,其直径约300 nm,是由约30 关键词： xFe_3-xO₄')" href="#">Co_xFe_3-xO₄ 多孔微球 磁性 交换偏置效应     

Y2(Fe1-x-y,Coy,Crx)17化合 物的结构及居里温度

通过x射线衍射及磁测量手段研究了Y₂(Fe_1-y-x,Co_y,C r_x)₁₇化合物的结 构及居里温度.研究结果表明Y₂(Fe_1-y-x,Co_y,Crx)₁₇化合物具有六 角相的Th₂Ni₁₇型结构.随着x的增加，Y₂(Fe 关键词： 2(Fe_1-y-x')" href="#">Y₂(Fe_1-y-x y')" href="#">Co_y x)_{1 7}化合物')" href="#">Cr_x)_{1 7}化合物 x射线衍射 居里温度     

类花状ZnO-CoFe2 O4 复合纳米管束的制备及其电磁波吸收特性

在90 ℃水溶液中采用两步晶体生长法制备出类花状ZnO-CoFe₂O₄复合纳米管束.ZnO纳米管束的管壁厚度大约为60 nm,管的直径大约为350 nm,CoFe₂O₄纳米颗粒连续包覆在ZnO纳米管束的表面,CoFe₂O₄纳米颗粒尺寸小于40 nm, 壳层厚度随着CoFe₂O₄在ZnO-CoFe₂O_{4 关键词： 类花状 2}O₄')" href="#">ZnO-CoFe₂O₄ 纳米管束 微波吸收剂     

H+5团簇离子及其中性团簇产物H3和H4

报道了H⁺₅的实验结果.分析讨论了H⁺₅的 形成和分解途径.根据理论分析，以稳定的H⁺₃为核心与一个或多个氢分子结合可能形成稳定的H^{+_n氢团簇离子.另一方面，在高频离子源中, 有发生H+₃与H₂反应的条件.实 验中，从高频离子源引出的离子束被静电加速器加速，然后用9 关键词： +}₅团簇离子')" href="#">H⁺₅团簇离子 3中性团簇')" href="#">H₃中性团簇 4中性团簇')" href="#">H_{4中性团簇}     

Fe3O4薄膜的电输运及光诱导特性研究

用脉冲激光沉积法在(111)Si衬底上成功制备了高度择优取向的Fe₃O₄薄膜.电阻-温度关系表明Fe₃O₄薄膜的Verwey转变(T_V)约在122 K,低温段(T_V)输运特征满足Mott变程跳跃模型,高温段(T>T_V)为小极化子输运.激光作用下的光电导实验发现,在整个温区表现为光致电阻率减小,而且低温段的电阻变化率比高温段要大很多.分析认为Fe₃O₄薄膜的光致电阻率变化主要与激光激发t_2g电子的转移有关. 关键词： 3O₄薄膜')" href="#">Fe₃O₄薄膜 小极化子 光诱导特性     

在氧-水蒸气存在下单相Sr2(Gd,Ce)2Cu2RuO10的合成及其电学性质

传统固相反应所合成的锶系钌铜氧化物，通常总伴有少量铁磁性SrRuO₃杂相.采 用氧(或空 气)_水蒸气混合气氛下的新型固相反应，既能成功合成锶系钌铜氧化物的前驱物纯相Sr₂G dRuO₆(211相), 也能进一步在相对低的温度下成功合成锶系钌铜氧1222纯相化 合物RuSr₂(Gd,Ce)₂Cu₂O₁₀ (Ru_1222）， 使其中SrRuO _{关键词： 水蒸气参与的新型固相反应 2}(Gd')" href="#">RuSr₂(Gd 2Cu_{2< /sub>O10纯相')" href="#">Ce)2Cu2< /sub>O10纯相 3杂相')" href="#">SrRuO3杂相 电学性质}     

Roles of oleic acid during micropore dispersing preparation of nano-calcium carbonate particles

In the present work, nano-calcium carbonate powder was prepared by micropore dispersion method with assistance of oleic acid as surfactant. CO₂ gas was dispersed into the Ca(OH)₂/H₂O slurry via a glass micropore-plate with the diameter of micropore about 20 μm. To investigate the effect of oleic acid on the size of CaCO₃ particles, different amount of oleic acid was added in Ca(OH)₂/H₂O slurry at 5 °C and 25 °C, respectively. XRD patterns show that cubic calcite is the only crystalline phase in all cases. ZPA data and TEM photo indicate that the average particle size synthesized at 5 °C without oleic acid is of about 40 nm, slightly smaller than that of prepared at 25 °C, and that the dispersity of sample prepared at 5 °C is better than that of 25 °C. When oleic acid is added in both temperatures, the average particle size decreases a little. FT-IR spectra demonstrate that oleic acid interacts with Ca²⁺ and carbon-carbon double bond existed on the surface of particle. Consequently, two opposite roles of oleic acid during the process of preparation of nano-CaCO₃ were proposed, namely preventing nanoparticles from growing during reaction and making nanoparticles reunite to a certain extent after reaction.     

A study of phase transfer processes of Ag nanoparticles

With the protection of sodium oleate, Ag nanoparticles are produced through the reduction of AgNO₃ with NaBH₄ in an aqueous solution. The possible mechanism of phase transfer of the Ag nanoparticles was discussed. At a suitable concentration of sodium oleate, after adding NaH₂PO₄, the oleic acid molecule can change its position on the surface of Ag nanoparticles under the effects of water and toluene and become amphipathic. So most of the nanoparticles form a film between water/toluene. For the case of a higher concentration of sodium oleate, excess sodium oleate will form a closed monolayer film on the surface of the Ag nanoparticles. After adding NaH₂PO₄, the oleic acid molecule cannot move on the Ag nanoparticles surface, thus the colloid particles are hydrophobic but not amphipathic. So most of the particles transfer to the organic phase. UV–Vis spectra, TEM and conventional metallographic microscopy are used to characterize the Ag nanoparticles and nanoparticles films.     

Re-examination of characteristic FTIR spectrum of secondary layer in bilayer oleic acid-coated Fe3O4 nanoparticles

Bilayer oleic acid-coated Fe₃O₄ nanoparticles can be applied in more areas than single layer oleic acid-coated ones because they can be well dispersed not only in nonpolar carrier liquids but also in polar carrier liquids, while the single layer oleic acid-coated ones can be dispersed only in nonpolar carrier liquids. Therefore, it is of significance to characterize the surface structure of bilayer and single layer oleic acid-coated Fe₃O₄ nanoparticles. However, there existed a discrepancy in the characteristic FTIR spectrum of the secondary layer in bilayer oleic acid-coated Fe₃O₄ nanoparticles. The goal of this paper was to resolve the discrepancy through using FTIR and TGA together with dispersibility to characterize the surface structure of bilayer and single layer oleic acid-coated Fe₃O₄ nanoparticles. The results showed that the band at 1710 cm⁻¹ was the characteristic band of the secondary layer in bilayer oleic acid-coated Fe₃O₄ nanoparticles. It can be used to distinguish whether the oleic acid-coated Fe₃O₄ nanoparticles are bilayer or not.     

Preparation of magnetite aqueous dispersion for magnetic fluid hyperthermia

An aqueous magnetic suspension was prepared by dispersing amphiphilic co-polymer-coated monodispersed magnetite nanoparticles synthesized through thermal decomposition of iron acetylacetonate (Fe(acac)₃) in a mixture of oleic acid and oleylamine. The average diameter of narrow-size-distributed magnetite nanoparticles varied between 5 and 12 nm depending on the experimental parameters such as reaction temperature, metal salt concentration and oleic acid/oleylamine ratio. Though the as-synthesized particles were coated with oleate and were dispersible in organic solvent, their surfaces were modified using amphiphilic co-polymers composed of poly(maleic anhydride-alt-1-octadecene) and polyethylene glycol-methyl ether and made dispersible in water. Infrared spectra of the sample indicated the existence of −COOH groups on the surface for further conjugation with biomolecules for targeted cancer therapy.     

Fe3O4@Au纳米星颗粒作为循环SERS基底用于农药残留物的检测

本文首先采用共沉淀的方法制备了Fe3O4纳米颗粒,随后经柠檬酸钠和对苯二酚还原氯金酸的方法在Fe3O4纳米颗粒的表面生成刺状Au纳米结构,进而获得Fe3O4@Au纳米星颗粒。该Fe3O4@Au纳米星颗粒作为SERS基底,用作农药残留物福美双和敌瘟磷的检测。由于高密度的Au纳米结构的尖端效应,该基底显示出高敏感的SERS活性。最后利用Fe3O4纳米颗粒的磁性,将其用于循环SERS测试,研究了其循环使用特性。     

Relaxation phenomena in ensembles of CoFe2O4 nanoparticles

Collective magnetic behavior of CoFe₂O₄ nanoparticles with diameters of 76, 16, 15 and 8 nm, respectively, prepared by different chemical methods has been investigated. Particle composition, size and structure have been characterized by inductive coupled plasma (ICP), transmission electron microscopy (TEM) and powder X-ray diffraction (PXRD). Basic magnetic properties have been determined from the temperature dependence of magnetization and magnetization isotherms measurements. The three samples exhibit characteristic of a superparamagnetic system with the presence of strong interparticle interactions. Magnetic relaxation phenomena have been examined via frequency-dependent ac susceptibility measurements and aging and memory effect experiments. For the particles coated with oleic acid, it has been demonstrated that the sample reveals all attributes of a super-spin glass (SSG) system with strong interparticle interactions.     

热解法制备KY3F10: Yb, RE(RE=Er, Ho, Tm)纳米晶及其特性研究

有机染料和量子点等荧光标记材料存在发射光谱宽、 光热稳定性差和细胞毒性等缺陷, 限制了其在生物学研究中的应用. 镧系掺杂上转换发光材料不存在"自发荧光"和"光漂白"现象, 灵敏度高, 长期稳定性好, 利于活体检测. 论文首次采用热解法, 以油酸和十八烯为表面活性剂和溶剂, 制备了KY₃F₁₀: Yb, RE(RE=Er, Ho, Tm) 纳米晶. 研究了油酸含量对产物形貌和粒径尺寸的影响, 当油酸与十八烯的比例为3:1时, 为制备类球形单分散纳米晶体的最佳工艺条件, 在980 nm半导体激光器激发下, 样品KY₃F₁₀: Yb, RE(RE=Er, Ho, Tm) 分别发射出较强的黄绿、 绿色和蓝色光, 这些结果显示KY₃F₁₀: Yb, RE(RE=Er, Ho, Tm) 纳米粒子作为生物探针在多重荧光标记方面具有优异的特性.     

Study of molecular surface coating on the stability of maghemite nanoparticles

In this study γ-Fe₂O₃ nanoparticle, surface-coated with increasing amount of oleic acid, have been prepared while the stability against particle degradation under laser excitation intensity was investigated. Maghemite nanoparticle was obtained via oxidation of magnetite nanoparticle, the latter synthesized by co-precipitation of Fe (II) and Fe (III) ions in alkaline medium. By varying the experimental conditions of surface-coating maghemite nanoparticles with oleic acid, samples with different grafting coefficient were obtained and investigated using X-ray diffraction and different spectroscopic techniques, namely Raman, Mössbauer, and infrared. The amount of oleic acid adsorbed on the maghemite surface was estimated via the carbon content obtained from elemental analysis.     

Microwave synthesis of magnetic Fe3O4 nanoparticles used as a precursor of nanocomposites and ferrofluids

Methods to synthesize magnetic Fe₃O₄ nanoparticles and to modify the surface of particles are presented in the present investigation. Fe₃O₄ magnetic nanoparticles were prepared by the co-precipitation of Fe³⁺ and Fe²⁺, NH₃·H₂O was used as the precipitating agent to adjust the pH value, and the aging of Fe₃O₄ magnetic nanoparticles was accelerated by microwave (MW) irradiation. The obtained Fe₃O₄ magnetic nanoparticles were characterized by Fourier transform infrared spectroscopy (FT-IR), transmission electron microscopy (TEM), X-ray powder diffraction (XRD) and vibrating sample magnetometer (VSM). The average size of Fe₃O₄ crystallites was found to be around 8–9 nm. Thereafter, the surface of Fe₃O₄ magnetic nanoparticles was modified by stearic acid. The resultant sample was characterized by FT-IR, scanning electron microscopy (SEM), XRD, lipophilic degree (LD) and sedimentation test. The FT-IR results indicated that a covalent bond was formed by chemical reaction between the hydroxyl groups on the surface of Fe₃O₄ nanoparticles and carboxyl groups of stearic acid, which changed the polarity of Fe₃O₄ nanoparticles. The dispersion of Fe₃O₄ in organic solvent was greatly improved. Effects of reaction time, reaction temperature and concentration of stearic acid on particle surface modification were investigated. In addition, Fe₃O₄/polystyrene (PS) nanocomposite was synthesized by adding surface modified Fe₃O₄ magnetic nanoparticles into styrene monomer, followed by the radical polymerization. The obtained nanocomposite was tested by thermogravimetry (TG), differential scanning calorimetry (DSC) and XRD. Results revealed that the thermal stability of PS was not significantly changed after adding Fe₃O₄ nanoparticles. The Fe₃O₄ magnetic fluid was characterized using UV–vis spectrophotometer, Gouy magnetic balance and laser particle-size analyzer. The testing results showed that the magnetic fluid had excellent stability, and had susceptibility of 4.46×10⁻⁸ and saturated magnetization of 6.56 emu/g. In addition, the mean size d (0.99) of magnetic Fe₃O₄ nanoparticles in the fluid was 36.19 nm.