热处理工艺对共沉淀CoFe2O4纳米颗粒的缺陷和磁性能的影响

通过化学共沉淀法制备了CoFe2O4纳米颗粒,并在不同的温度下进行热处理,研究了不同热处理工艺对CoFe2O4纳米颗粒的缺陷与磁性能的影响.X射线衍射谱(XRD)显示所有样品具有单一的尖晶石铁氧体结构,振动样品磁强计(VSM)测试显示了所有样品典型的铁磁性特征.红外光谱(FT-IR)显示650℃及以下温度热处理的样品存...     

介孔纳米磁性材料的性能控制(英文)

以SBA-15介孔分子筛为载体,利用溶胶凝胶-浸渍法合成一种新型纳米结构的磁性材料,同时利用XRD及VSM分析了合成介孔材料的微观结构以及磁性能。结果发现,合成材料的Fe2O3纳米颗粒存在于SBA-15的骨架中,而CoFe2O4纳米颗粒存在于介孔孔道中。介孔纳米磁性材料的磁性能可以通过掺杂CoFe2O4及Fe2O3的含量进行控制。掺杂CoFe2O4样品的饱和磁化强度可达未掺杂样品的12倍。此外,利用Kelly-Hankel(δM)曲线研究了合成介孔纳米磁性材料中CoFe2O4与Fe2O3纳米磁性材料间的交换耦合作用,这可以明显提升合成介孔材料的磁性能。     

Co1-xNixFe2O4／SiO2纳米复合材料的磁性

采用溶胶-凝胶法制备了Co1-xNixFe2O4/SiO2(0≤x≤1.0)纳米复合材料.利用XRD,TEM,振动样品磁强计(VSM)和M(o)ssbauer谱测试了900℃热处理样品的结构,晶粒尺寸和磁性.结果表明,样品中Co1-xNixFe2O4铁氧体的平均晶粒尺寸在15-20 nm之间,Ni2+的掺杂引起CoFe2O4晶胞体积减小.VSM结果表明,随Ni2+含量的增加,样品的比饱和磁化强度和矫顽力变小.M(o)ssbauer谱表明,室温下各样品均处于磁有序状态,样品的内磁场随N2+含量的增加而变小.     

有机凝胶-热分解法制备尖晶石型CoFe2O4纤维

以金属钴盐、铁盐及柠檬酸为原料,采用有机凝胶-热分解法成功制备了尖晶石型的CoFe2O4纤维.通过红外光谱(FTIR)、X射线衍射(XRD)、热重-差热分析(TG-DSC)以及扫描电镜(SEM)等分析手段对凝胶的结构、组成、热分解过程以及热处理产物的形貌进行了表征,并分析了影响凝胶可纺性以及纤维产生缺陷的各种因素.结果表明:在pH值为5.5左右的溶液中金属离子与柠檬酸反应形成具有线性分子结构的[(C6H6O7)4CoFe2]n,由这些线性分子所组成的凝胶显示出良好的可纺性.所制备的尖晶石型CoFe2O4纤维由40～50 nm大小的晶粒组成,纤维直径可小于1 μm,长径比达1×106.通过振动样品磁强计(VSM)测得这种尖晶石型CoFe2O4纤维的饱和磁化强度和矫顽力分别为81.97 A·m2/kg和1041.47×79.6 A/m.     

微量Al3+掺杂对钴铁氧体结构与磁学性能的影响

采用固相反应法制备CoFe2-xAlxO4(x=0,0.023,0.046,0.069,0.092)钴铁氧体系列样品,在1300℃氧气气氛下热处理后,采用X射线衍射仪(XRD)、物理性能测试系统(PPMS-9T)对样品的结构与磁性能进行了分析。结果表明,Al3+进入CoFe2O4晶格;本研究范围内微量的Al3+掺杂有助于促进CoFe2O4烧结致密化,微量的Al3+对CoFe2-xAlxO4样品的比饱和磁化强度没有损害,而样品的矫顽力略有降低。     

Zn0.95Co0.05O纳米线和纳米管的电泳沉积法可控合成（英文）

以阳极氧化铝为模板通过电泳沉积法制备Zn0.95Co0.05O纳米线和纳米管,并对电泳沉积法制备纳米线(管)的机理进行研究。系统的结构表征表明所得的纳米管和纳米线是由8～15nm的纤锌矿纳米晶构成的多晶结构,Co2+离子以代位掺杂形式掺入晶格,取代了晶格中的Zn2+离子。磁性表征显示制备的纳米线和纳米管具有室温铁磁性。由于Co在纳米线(管)中表面择优分布,纳米管的磁性明显高于纳米线。     

壳聚糖基碳原位包覆的Fe3O4纳米颗粒的制备及磁性研究

采用原位杂化技术和水热碳化技术相结合的方法,以壳聚糖作为碳源,实现了壳聚糖基碳原位包覆的Fe3O4纳米颗粒的制备,并对其物相、形貌以及磁性进行了系统研究。XRD结果表明原位杂化技术实现了壳聚糖原位包覆Fe3O4纳米颗粒(CS-MNP)的制备;CS-MNP经水热碳化后实现了壳聚糖基碳原位包覆的Fe3O4纳米颗粒(C-MNP)的制备,且水热碳化降低了MNP中氧空位的含量(由Fe2.90O4转变为Fe2.94O4)。C-MNP的TEM形貌清晰表明,MNP纳米颗粒粒径约为25nm,且颗粒表面存在显著的碳包覆层。水热碳化前后,C-MNP表现为超顺磁性,且饱和磁化强度较CS-MNP有所上升(由55.5(A·m2)/kg提高到61.5(A·m2)/kg)。     

基于可见光磁性纳米γ-Fe2O3/TiO2纳米管复合光催化剂

本文研究了基于可见光的磁性复合光催化剂——纳米γ-Fe2O3/TiO2 (NT)异质结阵列的制备方法,还研究了磁性复合光催化剂的表面形貌、微观结构、磁性能及其对亚甲基蓝的催化降解活性作用。研究结果表明,磁性复合光催化剂中的TiO2纳米管阵列呈高度有序,其直径约55nm、壁厚约10nm,沉积在上面的γ-Fe2O3颗粒粒径约15nm。复合光催化剂MHP呈超顺磁性,其超顺磁性来源于γ-Fe2O3的小尺寸效应。在可见光的照射下γ-Fe2O3/TiO2 (NT)的光催化性能明显大于的Fe3O4/TiO2 (NT)或纯TiO2（NT）。γ-Fe2O3和TiO2 (NT)之间的相互作用有利于电荷分离,并将TiO2(NT)红移至到可见光区。此外,γ-Fe2O3和TiO2 (NT)之间所形成的异质结结构有利于阻止光电子和空穴之间的复合。     

碳纳米管/四氧化三铁复合材料的磁性能和电催化性能

采用水热法制备碳纳米管(MWCNT)/四氧化三铁(Fe3O4)复合材料,运用透射电子显微镜(TEM)、X射线衍射(XRD)、傅立叶红外吸收光谱(FTIR)、振动样品磁强计(VSM)以及循环伏安法等对复合材料的微观结构、磁性能以及电化学行为进行研究和分析。结果表明:在MWCNT/Fe3O4复合材料中,磁性Fe3O4纳米颗粒能够对MWCNTs表面较好的包覆,实现了Fe3O4对MWCNTs的表面修饰;Fe3O4含量(质量分数)为62.5%的复合材料容易被磁化,常温下其饱和磁化强度(Ms)为35.89 A·m2/kg,矫顽力(Hc)为0.19 A/m,表现出良好的顺磁性;MWCNTs/Fe3O4修饰玻碳(GC)电极对H2O2的电化学响应具有良好的促进作用,使其氧化还原过电位升高,氧化峰值电流显著增强。     

PEI包覆磁性Fe_3O_4纳米颗粒的制备及性能研究

由于PEI/Fe3O4磁流体具有良好的生物兼容性,因而被广泛应用于生物医药领域。本实验用共沉淀法制备出磁性Fe3O4纳米颗粒,通过一次包覆改性法将PEI（聚乙烯亚胺）包覆在磁性Fe3O4纳米颗粒上。利用X-射线衍射仪（XRD）、透射电子显微镜（TEM）、红外光谱仪（FTIR）、振动样品磁强计（VSM）、热重分析仪（TG）等方法对其进行了表征。结果表明,实验制备出颗粒度为10nm左右的颗粒,PEI较好的吸附在其表面,吸附率为33.6%,颗粒度饱和磁化强度为58.05 emu/g,包覆后有所降低,但较好保持着原有磁性。     

Synthesis and characterization of aminated SiO2/CoFe2O4 nanoparticles

A kind of newly aminated CoFe2O4 nanoparticles were synthesized by grafting process for biomedical applications, which were coated primarily with silicon dioxide（SiO2）. The characterizations of aminated SiO2/CoFe2O4（ASCN） and SiO2-coated CoFe2O4（SCN） nanoparticles were investigated using elemental analysis, thermogravimetric analysis（TGA）, differential thermal analysis（DTA）, infi＇ared spectroscopy（IR）, atomic force microscopy（AFM）, zeta-potential measurement and vibrating sample magneto-metry（VSM） The AFM micrograph shows that the ASCN nanoparticles are approximately spherical with an average diameter of 30 nm. Based on IR and TGA results, it is suggested that the surface of the SiO2-coated CoFe2O4 nanoparticles are graiied with amino compounds. The elemental analysis also shows the presence of 0.98 mmol/g of organic moieties immobilized on the surface ofASCN nanoparticles. Zeta-potential data ofASCN nanoparticles also reveal that amino compounds are bonded onto the surface of SiO2-coated CoFe2O4 nanoparticles by ether linkage. The magnetic parameters show that ASCN nanoparticles still have good magnetic property.     

Fabrication and magnetic force microscopy (MFM) observation of nano scale ferromagnetic nanodot arrays

A novel electron beam lithography technique was utilized to fabricate nano scale magnetic dots array with high periodicity. C₆₀ film (fullerine) was used as an electron beam sensitive resist for electron beam patterning carried out under a high accelerating voltage of 200 kV in a transmission electron microscope with a scanning mode. 50 nm sized permalloy (Py) nanodot arrays were successfully fabricated using the method followed by ion-milling. An array of Co nanodots having a size of 100×70 nm was alternatively prepared by liftoff instead of ion milling so as to prevent surface damage by ion milling. Lift-off does not yield any surface roughness, which is important for device fabrication. Magnetic force microscopy (MFM) observations were carried out on the fabricated Co nanodot arrays. A single domain state could be realized in patterned Co nanodots. MFM tip induced magnetization effects were also clearly demonstrated in the array of Co nanodots.     

一维NiFe1.98RE0.02O4(RE=Pr, Nd, Sm)纳米丝的结构和磁性能

采用溶胶-凝胶法、静电纺丝技术和热处理技术相结合制备了一维NiFe_(1.98)RE_(0.02)O_4 (RE=Pr,Nd,Sm)纳米丝。利用X射线衍射仪(XRD)、傅里叶变换红外光谱仪(FT-IR)、扫描电子显微镜(SEM)和振动样品磁强计(VSM)对NiFe_(1.98)RE_(0.02)O_4 (RE=Pr,Nd,Sm)纳米丝的结构、形貌和磁性能进行表征。结果表明,NiFe_(1.98)RE_(0.02)O_4(RE=Pr,Nd,Sm)纳米丝表面光滑、直径均匀、连续,直径约60nm。掺杂Pr~(3+),Nd~(3+),Sm~(3+)均没有改变NiFe204的尖晶石结构,掺杂均降低了NiFe_2O_4的结晶度,晶粒尺寸D从44.8nm减小到33.8nm。NiFe_(1.98)RE~(0.02)O_4 (RE=Pr,Nd,Sm)纳米丝都表现出软磁特性。NiFe_(1.98)RE_(0.02)O_4 (RE=Pr,Nd,Sm)纳米丝的饱和磁化强度(Ms)分别为39.58,41.10,34.23 A·m~2/kg;矫顽力(H_c)分别为14119.2, 13678.4,15937.6 A/m;其中NiFe_(1.98)Nd_(0.02)O_4纳米丝的M_s (41.10 A·m~2/kg)最大,矫顽力H_c(13678.4A/m)最小,软磁性能最好。     

Fabrication of multilayer Nb2O5 nanoporous film by anodization of niobium foils

Multilayer Nb2O5 nanoporous films were successfully synthesized on Nb surfaces by the control anodization process in ethylene glycol containing 4 vol% HF and 2 vol% H2O2 electrolyte. The nanoporous films are characterized in detail by field-emission scanning electron microscopy(FESEM), transmission electron microscopy(TEM), and X-ray diffraction(XRD). The Nb2O5 nanoporous films have a multilayer morphology with the side wall thickness of *5 nm, irregular pores with a diameter of *25 nm, and a length of up to 7.39 lm, depending on the anodization time. A mechanism for the multilayer Nb2O5 nanoporous formation was also discussed. These nanoporous materials can be very useful in the fields of solar cells, gas sensors, catalysts, optical filters, and capacitors.     

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在140~180℃利用水热合成法制备了Co Fe2O4纳米颗粒。使用X射线衍射仪和振动磁强计检测Co Fe2O4纳米颗粒。结果表明:随着合成温度的升高,该颗粒的矫顽力先增大后减小,在160℃时出现峰值,晶粒尺寸和饱和磁化强度则持续增加。对上述Co Fe2O4纳米颗粒进行磁分离处理,结果表明:该颗粒的晶粒尺寸和矫顽力都有一定程度的提高,其中原产物晶粒尺寸越小,晶粒尺寸和矫顽力提高的效果越明显。说明磁分离可以去除样品中的超顺磁颗粒,减小样品的晶粒尺寸分布,提高样品的矫顽力。     

Preparation and characterization of PEG-PEI/Fe3O4 nano-magnetic fluid by co-precipitation method

PEG-PEI/Fe3O4 nano-magnetic fluids with different mass fractions of reactant were prepared by co-precipitation method. Besides particle size analyzer, the methods of XRD, IR, VSM and AFM were adopted to characterize the synthesized samples. Covalent bonding of PEG, PEI and Fe3O4 exhibits superparamagnetism. The TEM photograph shows that the particles are of stable dispersion and little aggregation, with smooth surface, spherical shape and a diameter of about 80 nm, which meets the requirements of nano-materials. When the mass fraction of PEI in reactant is 25%, the particle size, Zeta-potential and pEGFP-CI DNA loading efficiency are all satisfactory. In this case, PEG-PEI/Fe3O4 nano-magnetic fluids can be used as gene vectors or targeted drug carriers.     

Synthesis of BaFe12O19/MFe2O4 (M=Co,Mn) by sol-gel method

Composites of M-type hexaferrite BaFe12O19 and spinel ferrites MFe2O4 (M=Co, Mn) were directly synthesized by sol-gel method. The structure of composites was analyzed by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The formation of BaFe12O19 /CoFe2O4 composite was proved by XRD patterns with coexistence of diffraction peaks of the two kinds of ferrites, BaFe12O19 and CoFe2O4. Compared with BaFe12O19 , the diffraction peaks of CoFe2O4 are fairly weak, revealing the dominant structure of hexaferrite in the composite. SEM micrographs provide further evidence and the particle size of composites is about several hundred nanometer, meaning that the co-synthesizing sol-gel method can be in favor of the formation of finer particles. However, the diffraction peaks of MnFe2O4 can be hardly found in BaFe12O19 /MnFe2O4 composite, revealing the synthesis conditions are not favorable for the formation of MnFe2O4. Substitution reaction of Ba or Fe by Mn may be proposed.     

FERROMAGNETIC RESONANCE STUDIES OF Co/CoFe_2O_4 MULTILAYERS

1.IntroductionMultilayershaveattractedconsiderableattentionfromfundamentalandtechnologicalinterests.Manynewphenomenainmetal-metalmultilayers,suchasthereductionorenhancementofmagnetizationatinterfaces[1],themagneticanisotropyl'1,theoscillatoryinterlay...