表面活性剂在FePt纳米颗粒形貌控制中的应用

采用湿化学还原法制备FePt纳米颗粒,选择复配型表面活性剂柠檬酸和聚乙二醇(PEG)、油酸和油胺,以及单一型表面活性剂十二烷基苯磺酸钠对FePt纳米颗粒进行修饰,比较了三者在FePt纳米颗粒形貌及磁性能上的作用区别。XRD、TEM以及振动样品磁强计表征结果显示,表面活性剂的选择对制备FePt纳米颗粒的结构没有影响,均显示化学无序的面心立方结构;复配型表面活性剂有利于诱导生成各向异性纳米结构,聚合物表面活性剂PEG诱导生成了棒状和米粒状纳米结构;室温下颗粒均显示超顺磁性,但饱和磁化强度M s差别很大,球形颗粒M s相对最大,而棒状颗粒M s相对较小。     

表面活性剂调节高矫顽力FePt纳米颗粒的合成

在表面活性剂聚乙烯吡咯烷酮(PVP)存在的体系中,通过NaBH4还原前驱体Fe(acac)3和H2PtCl6·6H2O,制备出了单分散的尺寸在3.0 nm左右的FePt纳米颗粒。XRD和TEM表征结果显示,表面活性剂PVP的用量影响FePt纳米颗粒相变,但对颗粒的尺寸无明显作用。由此推测,PVP对FePt纳米颗粒的相变起"催化"作用,适量的PVP诱导纳米颗粒的相变,可以通过改变表面活性剂的用量来调节FePt纳米颗粒的磁性能,当表面活性剂PVP单体与FePt前驱体的摩尔比(PVP/FePt)为7时,制得的FePt纳米颗粒经过500℃保温30 min热处理后,矫顽力高达5.2 kOe。     

氧化还原法制备纳米镍粉研究

以氨水、Ni(NO3)2·6H2O为原料,在氧化还原体系下制备纳米镍粉末。讨论了表面活性剂、加料顺序、干燥方式以及煅烧温度等因素对纳米镍制备的影响;用X射线衍射、透射电子显微镜等对样品的成分、晶体结构、粒度及其分布进行了分析。结果表明:制得的纳米金属镍粉纯度高,粒径分布窄,平均粒径为35nm,粒径范围在30～40nm。     

微波溶剂热法制备Fe_3O_4颗粒

采用微波溶剂热法制备了Fe_3O_4颗粒,探讨了加热方式、微波加热时间、表面活性剂对平均粒径大小的影响,利用X射线衍射仪(XRD)、透射电镜(TEM)对样品的形貌和结构进行了表征,利用样品振动磁强计(VSM)对样品的磁学性能进行了表征。得出结论,微波加热1 h获得的纳米Fe_3O_4颗粒形状为粒度均匀的球形,平均粒径为14 nm,具有良好的分散性。所制备样品在室温下表现出一定的超顺磁行为。     

在微波辐射作用下制备纳米CeO2及其表面改性研究

本文以Ce(SO4)2·4H2O和NaOH为反应原料,用表面活性剂聚乙二醇(PEG)分散和保护产品,在微波辐射作用下制备了纳米CeO2.采用红外光谱仪、X射线衍射仪和差热热重联用分析仪对所制得的产品进行表征,产品颗粒粒径为24.9 nm.为了扩大所制备的纳米CeO2的应用范围,用表面活性剂月桂酸钠对其进行表面改性研究,结果表明该工艺具有高效、环保、产品分散性好、粒径小和易于推广等优点.     

纳米Fe3O4的合成及表面改性

在对合成纳米Fe3O4颗粒的最适宜反应条件进行探讨的基础上,通过正交实验得到了柠檬酸钠表面改性合成纳米Fe3O4颗粒的最适宜条件可以制得粒径为30～40nm的Fe3O4颗粒。通过红外光谱仪、透射电子显微镜证明合成产物为纳米Fe3O4颗粒,且粒径均匀,分散性好。     

四氧化三铁纳米颗粒的混合碱法合成

采用混合碱媒介法（CHM）制备四氧化三铁纳米颗粒,探索了制备工艺，通过SEM、XRD、TEM表征方法研究了实验合成条件对四氧化三铁纳米产物的形貌和微结构的影响。结果表明：以酞氟铁为原料用混合碱法可制得粒度均匀、粒径范围在100-200nm的四氧化三铁纳米颗粒，所制备的样品具有粒径小、粒度均匀、分散性较好的特点，是性能优良的磁性材料。     

球状氧化铝纳米颗粒的制备与表征

采用液相法制备纳米氧化铝,通过改变反应温度、表面活性剂添加量、铝离子和尿素物质的量比等条件,研究了不同反应条件对生成纳米氧化铝的粒径、形貌等性质的影响。结果表明:纳米氧化铝制备的最佳反应温度是60℃,CTAB的最优含量为0.5%,得到的纳米氧化铝分散性能较好,粒径最小。随着尿素量的增加,制备出的颗粒粒径呈现先减少后增加的趋势,在Al³⁺和尿素物质的量比为1∶1时得到的产物粒度分布最好。最优条件下制得的产物为γ-Al₂O₃,平均粒径约35 nm,组成相均一,微观形貌为球形,粒径分布窄而且分散性较好,在导热填料领域应用前景广阔。     

琥珀酸二异辛酯磺酸钠辅助作用下球形Pd纳米粒子的制备与表征

以琥珀酸二异辛酯磺酸钠(AOT)为表面活性剂,分别以抗坏血酸、硼氢化钠(NaBH4)、七水硫酸亚铁(FeSO4.7H2O)为还原剂,成功地制备了球状的钯纳米粒子。采用扫描电镜和X射线衍射仪对产物进行了表征,钯纳米颗粒的平均粒径约50～150nm。结果表明,当琥珀酸二异辛酯磺酸钠的浓度为15g/L,氯化钯的浓度为0.0025mol/L,抗坏血酸的浓度为0.05mol/L,40℃反应2h时,可制得大小均匀、粒径小、分散性好的钯纳米颗粒。     

无团聚纳米氧化锌的制备与机理研究

借鉴传统的直接沉淀法氧化锌生产工艺优点并进行原理性改进,开发出低成本、产量大、粒径可控、无团聚、高品质新型的纳米氧化锌生产工艺,即沉淀-分散法生产工艺。采用硫酸锌、碳酸氢铵为原料,在反应前加入表面活性剂,制得无团聚表面改性的碱式碳酸锌前驱体,用含有表面活性剂水洗涤,压滤干燥,在350～500℃下保温0.5～1.5h分解制得少团聚的粒径<60nm的纳米氧化锌;然后用无水乙醇作分散介质,将纳米氧化锌球磨2h,进行分散和无团聚化处理,压滤并回收乙醇,即制得无团聚、平均粒径35.6nm纳米氧化锌。     

Study on Composition Distribution and Ferromagnetism of Monodisperse FePt Nanoparticles

Monodisperse FePt nanoparticles with size of 4.5 and 6.0 nm were prepared by simultaneous reduction of platinum acetylacetonate and thermal decomposition of iron pentacarbonyl in benzylether. The crystallography structure, size, and composition of the FePt nanoparticles were examined by X-ray diffraction and transmission electron microscopy. Energy dispersive X-ray spectrometry measurements of individual particles indicate a broad compositional distribution in both the 4.5 and 6 nm FePt nanoparticles. The effects of compositional distribution on the phase-transition and magnetic properties of the FePt nanoparticles were investigated.     

超声辅助均匀沉淀法由前躯体ZnS制备ZnO纳米颗粒及其表征

前躯体ZnS在超声辅助60℃的低温条件下,采用醋酸锌为锌源、硫代乙酰胺为硫源来制备,然后采用在空气中热处理前躯体ZnS的方法制备了直径约为20~40 nm的ZnO纳米颗粒。所得产物分别采用红外光谱(FTIR)、热重-差热分析(TGA-DTA)、X射线衍射(XRD)、场发射扫描电镜(FE-SEM)、透射电镜(TEM)、电子能谱(EDS)和荧光光谱(PL)进行表征。实验结果表明,所得产物ZnO为六方纤锌矿结构,且结晶性很好,并且随着超声时间的延长其粒径有所降低。室温PL光谱表明,样品在400~550 nm内有3个较强的荧光发射峰。     

Magnetic Properties of FePt Nanoparticles Prepared by a Micellar Method

FePt nanoparticles with average size of 9 nm were synthesized using a diblock polymer micellar method combined with plasma treatment. To prevent from oxidation under ambient conditions, immediately after plasma treatment, the FePt nanoparticle arrays were in situ transferred into the film-growth chamber where they were covered by an SiO₂ overlayer. A nearly complete transformation of L1₀ FePt was achieved for samples annealed at temperatures above 700 °C. The well control on the FePt stoichiometry and avoidance from surface oxidation largely enhanced the coercivity, and a value as high as 10 kOe was obtained in this study. An evaluation of magnetic interactions was made using the so-called isothermal remanence (IRM) and dc-demagnetization (DCD) remanence curves and Kelly–Henkel plots (ΔM measurement). The ΔM measurement reveals that the resultant FePt nanoparticles exhibit a rather weak interparticle dipolar coupling, and the absence of interparticle exchange interaction suggests no significant particle agglomeration occurred during the post-annealing. Additionally, a slight parallel magnetic anisotropy was also observed. The results indicate the micellar method has a high potential in preparing FePt nanoparticle arrays used for ultrahigh density recording media.     

Optical and Photocatalytic Properties of Spinel ZnCr2O4 Nanoparticles Synthesized by a Hydrothermal Route

In this paper, a simple hydrothermal route has been developed to synthesize ZnCr₂O₄ nanoparticles. Experimental results show that the as-prepared ZnCr₂O₄ nanoparticles have an average particle size of <5 nm. The ZnCr₂O₄ nanoparticles have a direct band gap about 3.46 eV and exhibit blue emission in the range of 300–430 nm, centered at 358 nm when excited at 220 nm. Furthermore, the nanoparticles show apparent photocatalytic activities for the degradation of methylene blue under UV light irradiation.     

负载型Pt@Pd纳米粒子的制备与催化性能研究

用聚N-乙烯基乙酰胺接枝聚丙烯腈/聚苯乙烯(PNVA-g-PAN/PSt)聚合物微球为载体,H2PtCl6为金属源,无水乙醇为还原剂,将配位的Pt4+离子原位还原成为Pt纳米粒子负载于PNVA-g-PAN/PSt微球表面,进而在Pt纳米粒子上将Pd2+还原,制备了负载型Pt@Pd纳米粒子。用透射电子显微镜(TEM)对所制负载型Pt@Pd纳米粒子的形态与尺寸大小进行表征,结果显示,Pt@Pd纳米粒子均匀分布在聚合物微球表面;TEM和X-射线衍射结果显示,Pt@Pd纳米粒子的平均粒径随H2PtCl6与PdCl2比例的增加出现先增大后减小的变化趋势,粒径在9~22.2 nm之间;对肉桂酸产率的测定结果显示,该负载型Pt@Pd纳米粒子对碘代苯与丙烯酸交叉偶联反应有良好催化活性。     

Size Controlling of L1<Subscript>0</Subscript>-FePt Nanoparticles During High Temperature Annealing on the Surface of Carbon Nanotubes

Mono-size FePt nanoparticles with particles size about 2.5 nm have been prepared by polyol method on the surface of carbon nanotubes (CNTs). The CNTs functinalization time and the mass ratio of nanoparticles to CNTs affects on the CNTs surface coating. The as-synthesis nanocomposites have a superparamagnetic behavior with chemically disordered fcc structure at room temperature and they can be transformed into chemically ordered fct structure after thermal annealing above 600 °C. Their magnetic behavior changes from the superparamagnetic to the ferromagnetic with a large coercivity up to 0.83 T for the nanocomposites which annealed at 800 °C. The CNTs surfaces as a substrate prevent the agglomeration of nanoparticles during high temperature annealing and the FePt nanoparticles after annealing at 800 °C have finite size with an average about 10 nm. The structure, composition and magnetic properties of nanocomposite were characterized by X-ray diffraction, transmission electron microscopy, Fourier transform infrared spectroscopy and vibrating sample magnetometer.     

Sinter-free phase conversion and scanning transmission electron microscopy of FePt nanoparticle monolayers

Thermally robust monolayers of 4-6 nm diameter FePt nanoparticles (NPs) were fabricated by combining chemical synthesis and atomic layer deposition. Spin-cast monolayers of FePt NPs were coated with thin, 11 nm-thick layers of amorphous Al(2)O(3), followed by annealing to convert the FePt NPs from an alloy (A1) into intermetallic FePt (L1(0)) and FePt(3) (L1(2)) phases. The Al(2)O(3) layer serves as a barrier that prevents sintering between NPs during annealing at temperatures up to 730 °C. Electron and X-ray diffraction in conjunction with high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) show that as-synthesized A1 FePt NPs convert into L1(0) and L1(2) phase NPs through annealing. HAADF-STEM measurements of individual NPs reveal imperfect ordering and show that the NP composition determines which intermetallic phase is obtained. Mixed-phase NPs with L1(0) cores and FePt(3) L1(2) shells were also observed, as well as a smaller number of unconverted A1 NPs. These results highlight the need for improved control over the compositional uniformity of FePt NPs for their use in bit-patterned magnetic recording.     

Chemical synthesis of FePt nanoparticles with high alternate current magnetic susceptibility for biomedical applications

The present paper describes ordered alloy FePt nanoparticles with high magnetic susceptibility to alternate current (ac) fields at around room temperature for biomedical applications such as magnetic sensing devices for diagnostics and magnetic hyperthermia for cancer therapy. Since ac magnetic susceptibility takes the maximum value at a temperature near the blocking temperature of magnetic nanoparticles, the blocking temperature of the FePt nanoparticles is required to be adjusted at around room temperature to improve biomedical performances. Ordered alloy FePt has much higher magnetic anisotropy than iron oxides, and it can be the best candidate in the case of their particle size less than 10 nm. The ordered alloy FePt nanoparticles are synthesized by reduction of Fe and Pt organo-metallic compounds with tetraethylene glycol using poly(N-vinyl-2-pyrrolidone) (PVP) as a protective agent. PVP is a water-soluble polymer, and is proper to obtain dispersion into water. Influences of reaction temperature on crystallite size (particle size) and blocking temperature and the relationship between the blocking temperature and the value of ac magnetic susceptibility at around room temperature are investigated. Furthermore, PVP concentration at the synthesis to obtain well dispersed nanoparticle-suspension is examined.     

尖晶石型铁氧体CoFe_（2-x）Ni_xO_4（x=0.1～0.5）结构及光催化性能的研究

采用溶胶-凝胶法制备了铁氧体CoFe2-xNixO（4x=0.1~0.5）系列样品。利用XRD,SEM对纳米颗粒的结构、形貌进行了表征。结果表明,所合成的样品为尖晶石型,呈圆球状,粒径均匀,直径约为50nm。通过甲基橙的降解情况对其脱色率进行了研究。结果表明,经过B位Ni2＋掺杂的CoFe2-xNixO（4x=0.1~0.5）系列样品,其脱色率明显提高。