铁酸钴纳米晶体材料的制备

以ＦｅＳＯ４·７Ｈ２Ｏ和ＣｏＳＯ４·７Ｈ２Ｏ为原料,首先制备出晶粒细小的盐渍化碱式碳酸盐前驱体。在３００—７００℃焙烧１小时后,制备出ＣｏＦ２Ｏ４纳米晶体材料,经ＸＲＤ和ＴＥＭ检测,粒径为１０—４０ｎｍ,粒度均匀     

铁氧化物薄膜气敏材料的制备及性能研究评述

本文综合介绍近年来在铁氧化物薄膜所敏材料制备方法、性能方面的研究新进展，探讨了各种方法的特点。提出了今后铁氧化物气敏传感器的研究及改进方向。     

铁酸钴钠米晶体材料的制备

以ＦｅＳＯ４．７Ｈ２Ｏ和ＣｏＳＯ４．７Ｈ２Ｏ为原料,首先制备出晶粒细小的盐渍 化碱式碳酸盐前驱体。在３００－７００℃焙烧１小时后,制备出ＣｏＦ２Ｏ４纳米晶体材料,经ＸＲＤ和ＴＥＭ检测,粒径为１０－４０ｎｍ,粒度均匀。     

钴掺杂二氧化锡溶剂热法制备及其气敏性能研究

以SnCl2·2H2O、CoCl2·6H2O和无水乙醇为原料,采用溶剂热法成功制备钴掺杂SnO2粉末。通过XRD、SEM和TEM对所得样品进行物相分析和形貌观察,并将其制成元件进行气敏性能测试。结果表明:所制备的钴掺杂SnO2粉末为四方相金红石结构,钴离子的掺入并没有改变SnO2的晶体结构,对SO2气体具有较高的灵敏度和较好的响应—恢复特性。     

铁氧化物薄膜气敏材料的制备及性能研究评述

本文综合介绍近年来在铁氧化物薄膜气敏材料制备方法、性能方面的研究新进展 ,探讨了各种方法的特点。提出了今后铁氧化物气敏传感器的研究及改进方向     

纳米偏锡酸锌粉末的制备及气敏性能研究

把超声波和低温陈化技术运用到共沉淀法中,制备出了纳米ZnSnO3粉末.XRD和能谱分析表明为纯的ZnSnO3相.TEM分析表明粒度小于40nm.以ZnSnO3为基体的气敏元件对乙醇的灵敏度和选择性都很好,并且对汽油的抗干扰能力强.通过SEM对敏感层的分析解释了气敏特性的成因.     

水热合成制备纳米铁酸铜及其表征

为获得粒径小且分布均匀的铁酸铜(CuFe2O4)粉体,本文中以硝酸铜、硝酸铁及氢氧化钠为反应原料,采用水热法合成了纳米CuFe2O4粉体,研究了前驱体组分、反应温度、保温时间和表面活性剂聚乙烯醇(PVA)对CuFe2O4粉体制备的影响;用X射线衍射(XRD)、粒度分析仪、扫描电子显微镜(SEM)和红外光谱(IR)等分析方法对样品进行了表征。结果表明,前驱体中NO3-的存在将导致产物中铁酸亚铜CuFeO2的产生;在反应温度为320℃、以PVA作分散剂、保温3h的水热条件下可合成纳米CuFe2O4粉体。     

MxLa1—xFeO3气敏材料的制备及表征

采用液相化学共沉淀法制备出ＭｘＬａ１－ｘ ＦｅＯ３气敏材料。利用ＸＲＤ、ＳＥＭ、ＴＥＭ、ＩＲ、ＤＴＡＴＧ等分析技术，对材料的物相组成，结构，形貌等方面进行了表征。研究了各种因素对材料导电特性的影响情况。     

钴/SiO2纳米复合气凝胶的制备及表征

采用含钴硅酸乙酯为原料,通过溶胶－凝胶过程首次制备了高钴含量的比表面积为380-935m^2/g的钴／SiO2纳米复合气凝胶,并研究了其形貌、胶粒粒径及其分布和孔隙分布。     

直接共沉淀法制备掺杂α-Fe_2O_3及其气敏性能的初步研究

采用直接共沉淀法制备(掺杂)α-Fe2O3粉体并对其气敏性能进行了初步研究。采用正交实验法将各实验参数(反应物Fe3+浓度、Sn4+/Fe3+摩尔比、反应液pH值和烧结温度)有规律组合,用直接共沉淀法制备出一系列刚玉型结构的(掺杂)α-Fe2O3粉体,并用厚膜工艺将粉体涂在云母基片上制成了气敏元件。通过对粉体的XRD测试与分析发现,部分Sn4+以类质同象方式进入到α-Fe2O3晶格中,代替了Fe3+,改变了α-Fe2O3的晶胞参数;通过测试元件在不同温度下对甲烷的气敏性能,结果表明,掺杂提高了α-Fe2O3的气敏性,且得到了制备(掺杂)α-Fe2O3粉体的最佳参数。     

Structure and magnetic characterizations of cobalt ferrite films prepared by spray pyrolysis

Cobalt ferrite films were prepared by spray pyrolysis with post-annealing. For the as-deposited film, the differential scanning calorimetry measurement shows a crystallization peak at around 375 °C during the isochronal heating at 20 °C/min, and the X-ray diffraction pattern shows its amorphous-like characteristic. The isothermal post-annealings were performed for 2 h at various temperatures from 400 to 700 °C, leading to the crystallization of films, forming the spinel structure. The cross-sectional analysis with scanning electron microscopy shows that the film's thickness keeps almost constant after annealing, and the layered granular structure appears when the annealing temperature is high. The magnetic hysteresis loops of as-deposited and annealed films show that both the saturation magnetization and coercivity increase with the annealing temperature, due to the crystallization of CoFe₂O₄ phase.     

Synthesis of strontium ferrite nanoparticles by coprecipitation in the presence of polyacrylic acid

Strontium ferrite nanoparticles were prepared by coprecipitation in a PAA aqueous solution. The average diameter of the mixed hydroxide precipitates was 3.1 nm. From the thermal analysis by TGA/DTA and the phase analysis by XRD, it was shown that the appropriate molar ratio of Sr/Fe in aqueous solution was 1/8 and the precursor could yield pure strontium ferrite after calcination at above 700°C. The average diameters of the strontium ferrite nanoparticles calcined at 700 and 800°C were 34 and 41 nm, respectively. The magnetic measurements indicated that their saturation magnetization (57-59 emu/g) reached 85-88% of the theoretical one and increased with the decrease of temperature at 5-400 K. Their coercivity values (55-67 Oe) were much lower than those reported earlier, revealing the resultant nanoparticles were superparamagnetic. All the magnetic properties observed reflected the nature of nanoparticles and also concerned with their morphology and microstructure.     

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.     

Preparation of cobalt ferrite nanoparticles by using spent Li-ion batteries

Cobalt ferrite nanoparticles are a soft magnetic material have been extensively used in many electronic and magnetic applications. In this study, Co_0.8Fe_2.2O₄ nanoparticles with particle size of about 23.5 nm were directly synthesized by sol–gel auto-combustion and calcination methods using spent Li-ion batteries as raw materials. The overall process involves four steps: formation of homogeneous sols; formation of dried gels; combustion of the dried gels; and calcination of the dried gels after combustion at 1173 K for 2 h. The DTA–TG and IR were used to study the auto-combustion and thermal decomposition of the precursor, the morphology and structure of cobalt ferrite nanoparticles were characterized by XRD and TEM techniques. Moreover, the precise metal ion stoichiometry of cobalt ferrite nanoparticles was analyzed by ICP. The results revealed that the auto-combustion process was considered as a heat-induced exothermic oxidation–reduction reaction between nitrate ions and carboxyl group. The XRD patterns of calcination the dried gels after combustion confirmed the single phase spinel structure for the synthesized materials. The crystallite size was calculated from the most intense peak (3 1 1) using the Scherrer equation. The TEM photograph also shown that cobalt ferrite nanoparticles were well-dispersed and with little aggregation.     

钴铁氧体纳米粒子制备及其镧掺杂的磁性能研究

为了制备性能良好的钴铁氧体及改善其磁性能,通过改进的溶胶凝胶自蔓延燃烧法成功地制备了钴铁氧体(CoFe2O4)及掺镧(La)钴铁氧体纳米粒子.采用X射线衍射(XRD),透射电镜(TEM)、能谱分析(EDS)、振动样品磁场计(VSM)对所得粒子进行了结构、形貌、成分及磁性能表征.测试结果表明,利用改进的溶胶凝胶法制得钴铁氧体粒度均匀,且成相温度较低,500℃煅烧1h时平均粒径12nm左右;通过掺杂稀土镧元素对所得铁氧体的相结构有较强的影响,所得掺镧钴铁氧体与目标产物一致;所得钴铁氧体具有较高的矫顽力(737.33Oe),并且通过稀土元素镧的掺杂提高了钴铁氧体的矫顽力.     

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.     

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.     

Memory-core characteristics of cobalt substituted lithium ferrite

The memory-core characteristics of compositions in the system Li0.47-1/2x-1/2yCoxZnyNi0.06Fe2.47-1/2x-1/2yO4have been studied. The cobalt and zinc contents have been varied from zero to 0.02 and from zero to 0.12, respectively. It is demonstrated that small amounts of cobalt decrease the temperature coefficient of the coercive force and, in the zinc-containing materials, produce improved square-loop properties. These materials demonstrate improved pulse response properties when compared with unsubstituted lithium ferrite.     

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.