棒状纳米钡铁氧体的制备及镧掺杂对其性能的影响

为了研究制备工艺和掺杂对纳米钡铁氧体形貌及性能的影响规律,采用柠檬酸溶胶-凝胶法与燃烧相结合的方法制备出了BaFe12O19及掺镧钡铁氧体棒状纳米粒子.采用X射线衍射仪（XRD）,透射电镜（TEM）和磁强样品振荡计（VSM）对BaFe12O19及掺镧钡铁氧体的结构、形貌及磁性能进行了表征.通过对几个主要参数的摸索,得出制备棒状钡铁氧体的最佳工艺条件：pH值为4,煅烧温度为850℃,煅烧时间2h.该条件下制得的BaFe12O19样品分散均匀,呈棒状,直径约为50nm,长径比为6：1,矫顽力高达43460e;采用同样的方法,对钡铁氧体进行了稀土镧元素掺杂,所得掺镧钡铁氧体粒度在纳米范围,也呈现明显的棒状.另外,通过掺杂稀土元素镧使钡铁氧体的成相得到改善,对钡铁氧体的磁性能有一定程度的影响.     

镍锌钴铁氧体/碳纳米管复合吸波材料的制备及表征

采用沸腾回流法制备了Ni0.4Zn0.35Co0.25LaxFe2-xO4/碳纳米管(CNTs)复合吸波材料,考察了镧(La)的掺杂量对复合材料磁性及吸波性能的影响。研究表明:沸腾回流法制备的铁氧体为单相尖晶石结构,纳米铁氧体粒子成功包覆在碳纳米管上。La3+掺杂量x=0.07时,产物的矫顽力(Hc)最大,且吸波性能最佳。     

废旧锂离子电池溶胶-凝胶法制备钴铁氧体的研究

以硫酸加双氧水溶解废旧锂离子电池所得的溶液为原料,以酒石酸为凝胶剂用溶胶-凝胶法制备出具有尖晶石结构的钴铁氧体,借助于XRD、振动样品磁强计对样品的结构和磁性进行了研究.研究表明,制备钴铁氧体的适宜条件为:酒石酸和总金属离子的比例为2:1,pH值=8.2,煅烧温度为500℃,煅烧时间为2h.所得样品的剩余磁化强度为23.5kA·m-1,饱和磁化强度为67.7kA·m-1,矫顽力为45.2kA·m-1.     

活性炭负载Co0.8Zn0.2Fe2O4铁氧体的制备及电磁性能研究

采用溶胶-凝胶法制备活性炭负载纳米钴锌铁氧体复合吸波材料研究。以柠檬酸为络合剂制备Co0.8Zn0.2Fe2O4铁氧体溶胶,加入活性炭于溶胶中,经浓缩制得活性炭/钴锌铁氧体凝胶,再经过低温煅烧,制备出形态和结构理想的活性炭负载钴锌铁氧体复合材料;详细地考察烧结温度、煅烧时间及活性炭与铁氧体的配比等工艺参数对复合材料的形态和结构的影响;分别采用X射线衍射(XRD)、扫描电镜(SEM)和能量散射X射线荧光光谱(EDX)对制备出的复合材料进行形貌、结构及组成表征分析。采用波导法在8.2～12.4GHz波段对活性炭负载纳米钴锌铁氧体复合材料进行电磁参数测试分析,结果表明所制备活性炭负载纳米钴锌铁氧体复合材料具有较高的电、磁损耗角正切值,其吸波性能较好。     

Co1-xZnxFe2O4铁氧体气凝胶的制备及其性能研究

采用醇-水溶液加热法结合超临界流体干燥(SFCD)制备了Co10xZnxFe2O4铁氧体气凝胶,对样品进行了XRD、BET、VSM、ICP及TEM等表征.结果表明.所得铁氧体气凝胶为单一尖晶石结构,具有较高的比饱和磁化强度、较大的矫顽力以及较高的比表面积;在一定范围内,改变Zn含量可以改善CoZn铁氧体气凝胶的性能.     

基于多朗德因子和低磁晶各向异性场的钒镍共掺杂钡铁氧体毫米吸波材料

采用溶胶-凝胶法制备了V5+掺杂和V5+-Ni2+共掺钡铁氧体.采用SEM、XRD、XPS等手段对粉末的微观结构进行了表征,并利用矢量网络分析仪对电磁性能进行了测试.与V5+取代体系相比,V5+-Ni2+共掺杂钡铁氧体可减小其磁晶各向异性场和引入三个不同的Landé因子(g),具有更好的吸波性能.当V5+-Ni2+共掺...     

掺杂稀土元素镧的钡铁氧体超微粉末的微波吸收特性研究

采用溶胶-凝胶法制备了掺杂稀土元素镧的钡铁氧体超微粉末,就镧元素的掺杂含量对钡铁氧体吸波性能的影响进行了对比研究.实验表明,用聚乙二醇凝胶法制备的BaLaxFe12-xO19超微粉末,当x为0.03时,对微波吸收效果最佳.在涂层厚度1.0mm,测试频段为7.5～11.9GHz内,吸收量均在25dB以上,在11.6GHz处,吸收峰值达41.4dB.     

少量钴掺杂对Mn-Zn铁氧体结构和磁性质的影响(英文)

采用溶胶凝胶自燃烧法制备了钴掺杂的Mn-Zn铁氧体,研究了少量钴掺杂对其结构和磁性质的影响。利用X射线衍射仪对制备的粉末测试发现,Mn0.4Zn0.6-xCoxFe2O4系列铁氧体都具有纯净的尖晶石结构。晶格常数和饱和磁化强度都随着钴替代量的增加而增加。μi-T线具有两个磁导率最大的峰值并且磁导率的第二峰值随着钴的增加向低温移动。磁导率的第二峰值的温度可以通过改变钴含量来调节。基于铁氧体中磁晶各向异性补偿模型,阐明了少量钴掺杂对铁氧体磁性质影响的作用机理。     

锶铁氧体包覆碳纳米管吸波材料的制备及表征

采用溶胶-凝胶法制备锶铁氧体包覆碳纳米管(CNTs)的吸波材料,并考察了碳纳米管含量对包覆后样品磁性能及吸波性能的影响.经TEM、XRD验证锶铁氧体成功地包覆在碳纳米管表面;ALVSM图中可以看出6%CNTs-SrFe11.5O19的磁性能最佳,矫顽力(Hc)为5916.13Oe.而经网络分析仪测定,5% CNTs-S...     

尖晶石型纳米铁氧体的制备与吸波性能

采用柠檬酸盐溶胶凝胶法制得尖晶石型纳米钴镍锰锌铜铁氧体,通过原子吸收光谱仪测定元素组成,XRD、透射电镜、网络分析仪研究矿物组成并研究其颗粒形貌与吸波性能。试验表明:所得产物为尖晶石立方晶系铁氧体;其中铁元素易于被钴取代,形成CoFe2O4;而Mn、Zn、Cu、Ni趋向于互相掺杂形成固溶铁氧体。铁氧体的平均粒径为50nm。采用网络分析仪研究了5~7GHz,9~11GHz,15~18GHz内铁氧体的吸波性能:尖晶石型立方晶系纳米铁氧体具有良好的微波吸收性能;适量提高锰、锌等掺杂元素含量,有助于提高材料的吸波性能。     

Study of DNA interaction with cobalt ferrite nanoparticles

Interaction of cobalt ferrite nanopowder and nucleic acid was investigated. Superparamagnetic cobalt ferrite nanoparticles (6-12 nm) were prepared by mechanochemical synthesis. Structure of the nanopowder was characterized using X-ray diffraction. It was shown that cobalt ferrite nanoparticles were associated with ssDNA and dsDNA in Tris-buffer resulting in bionanocomposite formation with mass weight relation nanoparticles: DNA 1:(0.083 +/- 0.003) and 1:(0.075 +/- 0.003) respectively. The mechanism of interaction between a DNA and cobalt ferrite nanoparticles was considered basing on the whole set of obtained data: FTIR-spectroscopy, analyzing desorption of DNA from the surface of the particles while changing the chemical content of the medium, and on the modeling interaction of specific biomolecule fragments with surface of a inorganic material. It was supposed that the linkage was based on coordination interaction of the phosphate groups and oxygen atoms heterocyclic bases of DNA with metal ions on the particle surface. These data can be used to design specific magnetic DNA-nanoparticles hybrid structures.     

Study of preparation and magnetic properties of silica-coated cobalt ferrite nanocomposites

The structure and the magnetic properties of silica-coated cobalt ferrite nanoparticles (80 wt% CoFe₂O₄), prepared by sol–gel method and submitted to thermal treatments in the range 800–1,000 °C, were investigated through XRD, FT-IR, TEM and VSM. The effects of thermal treatment temperatures on the structure and magnetic properties of nanoparticles were examined. A silica shell thickness of about 5 nm was synthesized on top of cobalt ferrite nanoparticles. The non-crystalline silica confines the growth of cobalt ferrite nanoparticles, i.e., the particle sizes are almost independent of the thermal treatment. Saturation magnetization (Ms) was decreased slightly and coercivity (Hc) was increased, when the non-crystalline silica was coated on the surface of cobalt ferrite nanoparticles.     

A new aluminum-based metal matrix composite reinforced with cobalt ferrite magnetic nanoparticle

A new composite with cobalt ferrite magnetic nanoparticle dispersed in an aluminum matrix has been prepared using the ball-milling technique followed by compaction and sintering. Our efforts were largely focused on investigating the contribution of cobalt ferrite to the enhancement of structural, mechanical and magnetic properties of aluminum. Incorporation of 1–10 weight (wt)% of nanosized cobalt ferrite into the aluminum matrix could affect remarkable change in mechanical properties. Enhancement of hardness value, elastic modulus, and compressive strength was observed in the case of cobalt ferrite-incorporated aluminum matrix as compared to the pure aluminum sample. Incorporation of cobalt ferrite could impart considerable improvement of magnetization value of the aluminum matrix with a saturation magnetization of 17.07 emu/g for the aluminum sample reinforced with 10 wt% of cobalt ferrite. A decrease in coercive force in the sample arising from the increase in surface effects and inter-particle interaction between the ferromagnetic cobalt ferrite and soft phases in the matrix was also observed.     

In situ fabrication and characterization of cobalt ferrite nanorods/graphene composites

Cobalt ferrite nanorods/graphene composites were prepared by a one-step hydrothermal process using NaHSO₃ as the reducing agent and 1-propyl-3-hexadecylimidazolium bromide as the structure growth-directing template. The reduction of graphene oxide and the in situ formation of cobalt ferrite nanorods were accomplished in a one-step reaction. The structure and morphology of as-obtained composites were characterized by field emission scanning electron microscopy, transmission electron microscopy, high resolution transmission electron microscopy, atomic force microscope, X-ray diffractometer, Fourier transform infrared spectra, X-ray photoelectron spectroscopy and Raman spectroscopy. Uniform rod-like cobalt ferrites with diameters of about 100 nm and length of about 800 nm were homogeneously distributed on the graphene sheets. The hybrid materials showed a saturation magnetization of 42.5 emu/g and coercivity of 495.1 Oe at room temperature. The electromagnetic parameters were measured using a vector network analyzer. A minimum reflection loss (RL) of − 25.8 dB was observed at 16.1 GHz for the cobalt ferrite nanorods/graphene composites with a thickness of 2 mm, and the effective absorption frequency (RL < − 10 dB) ranged from 13.5 to 18.0 GHz. The composites exhibited better absorbing properties than the cobalt ferrite nanorods and the mixture of cobalt ferrite nanorods and graphene.     

Modification of spin coating method and its application to grow thin films of cobalt ferrite

Spin coating method has been modified to widen its scope for applications. The film deposition assembly is suitably designed. With this modification, it is possible to use common inorganic chemicals in the form of their aqueous solutions as starting materials to grow thin films of binary/ternary oxides. This method is applied to grow thin films of cobalt ferrite. The structure, morphology and magnetic properties of thin films of cobalt ferrite have been determined by using X-ray diffraction, Scanning electron microscopy and vibrating sample magnetometer respectively. The results show that the present technique is useful to deposit thin films of cobalt ferrite, which are qualitatively comparable to the films grown by other wet chemical techniques.     

Magnetic behavior of cobalt ferrite nanowires prepared by template-assisted technique

Spinel cobalt ferrite nanowires were successfully prepared in mesoporous silica SBA-15 as a host matrix followed by slow thermal decomposition of the precursors inside the silica-based template. The formation and phase control of as-synthesized nanostructured cobalt ferrites were confirmed by X-ray diffraction (XRD) measurements at different annealing temperatures ranging from 500 to 1000 °C. The one-dimensional spinel nanostructures were identified by recording the transmission electron microscopy (TEM) images after a selective removal of the silica template in aqueous solution of NaOH. The final product was also characterized using infrared spectroscopy (FT-IR) and vibration sample magnetometer (VSM). The presence of SBA-15 lowers the formation temperature of cobalt ferrite nanowires compared to the corresponding bulk material. The nanowires annealed up to 700 °C exhibited magnetic behavior characteristic for soft magnetic materials, whereas samples annealed at temperature higher than 700 °C revealed magnetic behavior characteristic for hard magnetic materials with rectangular form and large coercive field.     

Spindly cobalt ferrite nanocrystals: preparation, characterization and magnetic properties

In this paper we describe the preparation of homogeneously needle-shaped cobalt ferrite (CoFe(2)O(4)) nanocrystals on a large scale through the smooth decomposition of urea and the resulting co-precipitation of Co(2+) and Fe(3+) in oleic acid micelles. Furthermore, we found that other ferrite nanocrystals with a needle-like shape, such as zinc ferrite (ZnFe(2)O(4)) and nickel ferrite (NiFe(2)O(4)), can be prepared by the same process. Needle-shaped CoFe(2)O(4) nanocrystals dispersed in an aqueous solution containing oleic acid exhibit excellent stability and the formed colloid does not produce any precipitations after two months, which is of prime importance if these materials are applied in magnetic fluids. X-ray diffraction (XRD) measurements were used to characterize the phase and component of the co-precipitation products, and demonstrate that they are spinel ferrite with a cubic symmetry. Transmission electron microscopy (TEM) observation showed that all the nanocrystals present a needle-like shape with a 22?nm short axis and an aspect ratio of around?6. Varying the concentration of oleic acid did not bring about any obvious influence on the size distribution and shapes of CoFe(2)O(4). The magnetic properties of the needle-shaped CoFe(2)O(4) nanocrystals were evaluated by using a vibrating sample magnetometer (VSM), electron paramagnetic resonance (EPR), and a M?ssbauer spectrometer, and the results all demonstrated that CoFe(2)O(4) nanocrystals were superparamagnetic at room temperature.     

Arsenic adsorption on cobalt and manganese ferrite nanoparticles

The adsorption of As(III) on cobalt and manganese ferrite nanoparticles (NPs) was studied. The ferrite NPs were synthesized using the Massart-assisted microwave hydrothermal treatment. All the NPs exhibited the spinel structure with a formula such as M _x Fe_3?x O₄, where M = Co or Mn, and x runs from 0.21 to 1.14. The changes in the stoichiometry caused different effects on the physical properties as well on the As(III) adsorption capacity of the NPs. The adsorption data were fitted in very good agreement with the Freundlich model. It was concluded that As(III) was better attracted to ferrimagnetic cobalt ferrite NPs, given that the arsenic removal was significantly higher than that exhibited by superparamagnetic manganese-substituted ferrite NPs.     

The role of cobalt ferrite magnetic nanoparticles in medical science

The nanotechnology industry is rapidly growing and promises that the substantial changes that will have significant economic and scientific impacts be applicable to a wide range of areas, such as aerospace engineering, nano-electronics, environmental remediation and medical healthcare. In this area, cobalt ferrite nanoparticles have been regarded as one of the competitive candidates because of their suitable physical, chemical and magnetic properties like the high anisotropy constant, high coercivity and high Curie temperature, moderate saturation magnetization and ease of synthesis. This paper introduces the magnetic properties, synthesis methods and some medical applications, including the hyperthermia, magnetic resonance imaging (MRI), magnetic separation and drug delivery of cobalt ferrite nanoparticles.     

Microwave absorbent properties of nanosized cobalt ferrite powders prepared by coprecipitation and subjected to different thermal treatments

Cobalt ferrite nanopowders were produced by means of two methods using a common precipitating agent. After precipitation, in the first method the cobalt ferrite was calcined, whilst in the second method the precipitation was followed by a hydrothermal treatment. Characterization of the obtained powders was achieved by X-ray diffraction and scanning electron microscopy–energy dispersive X-ray analysis (SEM–EDAX). Frequency dependence of the complex dielectric permittivity and complex magnetic permeability, over the frequency range 0.1–6 GHz, was also studied. By means of the above mentioned investigations, the structure, morphology and microwave absorbent properties of the powders obtained by both methods were compared.