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.     

Preparation of ultrafine chalcopyrite nanoparticles via the photochemical decomposition of molecular single-source precursors

The synthesis and characterization of ultrafine CuInS2 nanoparticles are described. Ultraviolet irradiation was used to decompose a molecular single source precursor, yielding organic soluble approximately 2 nm sized nanoparticles with a narrow size distribution. UV-vis absorption, 1H and 31P{1H} NMR, and fluorescence spectroscopies and mass spectrometry were used to characterize decomposition of the precursors and nanoparticle formation. The nanoparticles were characterized by high-resolution transmission electron microscopy (HRTEM), scanning electron microscopy energy dispersive X-ray spectroscopy, powder X-ray diffraction (XRD), electron diffraction, inductively coupled plasma analysis, UV-vis absorption spectroscopy, and fluorescence spectroscopy. They have a wurzite-type crystal structure with a copper-rich composition. The hypsochromic shift in their emission band due to quantum confinement effects is consistent with the size of the nanocrystals indicated in the HRTEM and XRD analyses.     

Preparation of ZnO nanoparticles by thermal decomposition of zinc alginate

A new method to produce zinc oxide nanocrystals is presented. The method is based on the thermal decomposition of zinc alginate gels. The gels were produced in the form of beads by ionic gelation between a zinc solution and sodium alginate. The wet beads were heated at 800 and 450 °C for 24 h and the products were characterized by X-ray diffraction (XRD), Scanning Electron Microscopy (SEM) and Transmission electron microscopy (TEM) and micro-Raman spectroscopy. XRD analysis showed that all obtained samples are of wurtzite structure. TEM analysis combined with electron diffraction also showed the presence of single crystals indexed as ZnO hexagonal phase. Crystal size was determined by measuring individual crystals from SEM pictures. It was found that heating temperature and the kind of zinc agent influence the crystal size. Raman scattering revealed the existence of defects in the structure of nanoparticles whose cringing was discussed in the context of recent studies in this field.     

Synthesis of high-luminescent cadmium sulfide nanocrystallites by a novel single-source precursor route

Highly luminescent cadmium sulfide nanocrystallites have been successfully produced by the thermolysis of a novel single-source precursor, cadmium O, O′-dialkyldithiophosphates, which were dissolved in oleic amine. The microstructure and morphology of the as-prepared CdS nanoparticles were characterized using X-ray diffraction, transmission electron microscopy and high resolution transmission electron microscopy. It was found that the as-prepared CdS nanoparticles show a narrow size distribution and high crystallinity. The optical properties of these samples were examined by UV-visible and photoluminescence spectroscopy. Not only an intensive red-light-emitting luminescence phenomenon derived from the solution of the CdS nanocrystallites can be observed easily at room temperature, the band gap of CdS nanocrystallites can also be tailored by changing the length of substituted alkyl chain of single-source precursors.     

Preparation of nickel and Ni-Zn ferrite films by thermal decomposition of metal acetylacetonates

Nickel and Ni-Zn ferrite (Ni_1–x Zn _x Fe₂O₄) films were prepared on various substrates (quartz glass, MgO single crystal, etc.) by thermal decomposition of metal acetylacetonates (Ni (acac)₂ · 2H₂O, Zn (acac)₂ · 2H₂O and Fe (acac)₃). Typical decomposition and heat treatment conditions for obtaining a single phase of NiFe₂O₄ film were as follows: evaporation temperature of Ni-Fe complexes: 230°C, the mole concentration of Fe (acac)₃,R (%) = Fe (acac)₃/(Fe (acac)₃ + Ni (acac)₂ · 2H₂O) = 33, substrate temperature: 330 to 550° C, and heat treatment of the as-grown film: 800 to 1000° C, 1 h. Ni_1–x Zn _x Fe₂O₄ films were obtained by controlling the compositionR in Ni-Fe complexes and the evaporation temperature of Zn (acac)₂ · 2H₂O. The Ni-Zn ferrite film at the compositionx = 0.37 (Ni_0.63Zn_0.37Fe₂O₄) gave the maximum saturation magnetization _s = 60 emu g^–1 and the coercive forceHc 25 Oe. These films showed a magnetic anisotropy which makes the magnetization easy parallel to film surface.     

Preparation of titanium carbonitride nanoparticles from a novel refluxing-derived precursor

Titanium carbonitride (TiC_xN_1 − x) nanoparticles were prepared from a novel refluxing-derived precursor. The organic/inorganic hybrid precursor was prepared by two-stage refluxing method using hydrous TiO₂ as titania source and n-Dodecane as carbon source. The precursor was heat-treated to 1350 °C in flowing nitrogen to get TiC_xN_1 − x nanoparticles. Electron microscopy photographs showed the particle size ranged from 20 to 60 nm. X-ray powder diffraction pattern indicated that the product was face-centered cubic TiC_xN_1 − x with a lattice constant a = 4.2872 Å and average crystallite sizes of 33.4 nm. Long time refluxing results in Alkane dehydrogenation and the formation of coke occur and promotes the coke to large scale impinge on TiO₂ nanoparticles as carbon source in the carbothermal reduction-nitridation reaction.     

Low temperature synthesis of bismuth ferrite nanoparticles by a ferrioxalate precursor method

The synthesis of bismuth ferrite by solid-state reaction of Bi₂O₃ and Fe₂O₃ results in the formation of multiphase products. Even coprecipitation followed by calcination leads to the formation of impurity phases. Here, we report the synthesis of magnetoelectric bismuth ferrite by a ferrioxalate precursor method. In this process, bismuth ferrite, synthesized through solutions of some specific salts led to the formation of phase pure (perovskite) nanocrystalline powder (11–22 nm as evident from X-ray diffraction analysis) at a temperature of 600 °C. The synthesized powders were characterized by X-ray diffractometry, thermogravimetry and differential thermal analysis, Fourier transformation infrared spectroscopy and scanning electron microscopy. The synthesis route is simple, energy saving and cost-effective. Such nanosized bismuth ferrite powder may have a potential application in making lead free piezoelectric materials for actuators as well as magnetoelectric sensors.     

凝胶前驱体纤维热分解还原制备铁纤维

以柠檬酸铁为原料,通过水溶液中的聚合反应合成了具有良好可纺性的前驱体溶胶,经过干法纺丝、凝胶化和高温热分解还原,制得了直径约为10~15μm的金属铁纤维.本文研究了不同原料、配比、pH值对溶胶前驱体可纺性的影响,应用傅里叶红外光谱(FTIR)、X射线衍射(XRD)和扫描电镜(SEM)对溶胶前驱体的形成、热分解转化过程及产物的物相组成进行了研究.     

Synthesis of copper and copper(I) oxide nanoparticles by thermal decomposition of a new precursor

The present investigation reports, the novel synthesis of nanoparticles Cu and Cu₂O using thermal decomposition and its physicochemical characterization. The nanoparticles copper powder have been prepared using [Bis(salicylidiminato)copper(II)], [Cu(sal)₂], as precursor. Cu nanoparticles are initially formed and subsequently oxidized to form Cu₂O. Transmission electron microscopy (TEM) analysis demonstrated nanoparticles Cu₂O with an average diameter of about 10 nm. As-prepared copper nano-particles were characterized by X-ray diffraction measurements (XRD), scanning electron microscopy (SEM), energy dispersive analysis of X-rays (EDAX), and Fourier transform infra-red spectroscopy (FTIR). XRD analysis revealed broad pattern for fcc crystal structure of copper metal and cubic cuprite structure for Cu₂O. Optical absorption measured by UV–visible spectroscopy was used to monitor oxidation course of Cu → Cu₂O and to determine the band-gap energy about 2.4 eV for Cu₂O nanoshells.     

Preparation and characterization of ultra-stable biocompatible magnetic fluids using citrate-coated cobalt ferrite nanoparticles

Preparation and characterization of ultra-stable biocompatible cobalt ferrite-based magnetic fluids has been reported. Synthesized samples have core particle diameter in the range of 4.7 to 14.8 nm, as indicated by TEM. Chemical and crystalline data show that the prepared nanoparticles are cobalt ferrite with a slight deviation from the Fe : Co :: 2 : 1 stoichiometry. ATR-FTIR spectroscopy was used to investigate the citrate adsorption onto the nanoparticle surface. The fitted adsorption time-constants were 0.006 and 0.033 min^− 1 for nanoparticle diameter of 4.7 and 14.8 nm, respectively.     

碳包钴纳米颗粒/聚二甲基硅氧烷复合热界面材料的制备和性能

为了制备具有良好的热导率、热稳定性、导电性和柔顺性的纳米颗粒填充硅树脂复合材料,首先以乙基封端聚二甲基硅氧烷(PDMS)为基体材料,以碳包钴纳米颗粒(C@Co)为填料,采用研磨共混法制备了C@Co/PDMS复合热界面材料。然后,运用TEM、XRD、Raman和SEM分别对C@Co的微观结构、物相、石墨化程度和分散性进行了研究。最后,研究了C@Co含量对复合热界面材料的热导率、热稳定性、导电性和柔顺性的影响。结果表明:该复合热界面材料的热导率随着C@Co含量的增加而增大,当C@Co的含量为24wt%时,复合材料的热导率达到最大值1.64 W/(m·K),比纯PDMS的提高了10.7倍;TG分析表明,添加24wt%的C@Co后,复合材料的起始分解温度和最终分解温度比纯PDMS的分别提高了约70℃和80℃,说明C@Co能提高复合材料的热稳定性;随着C@Co含量的增加,复合热界面材料的电导率非线性增大,拟合试差计算的逾渗阀值为10wt%,即C@Co含量小于10wt%时复合材料的绝缘性良好,而填充24wt%的C@Co时复合材料的电导率为9.38×10-3 S·m-1;复合材料的硬度适中,处于17.6~26.8HA范围内,表明该复合材料的柔顺性较好。因此,24wt%C@Co/PDMS复合材料不仅能满足热界面材料电性能的基本要求,且具有良好的热导率、热稳定性和柔顺性。     

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.     

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.     

Preparation and characterization of CuO nanorods by thermal decomposition of CuC2O4 precursor

Synthesis of copper oxide (CuO) nanorods was achieved by thermal decomposition of the precursor of CuC₂O₄ obtained via chemical reaction between Cu(CH₃COO)₂·H₂O and H₂C₂O₄·2H₂O in the presence of surfactant nonyl phenyl ether (9)/(5) (NP-9/5) and NaCl flux. Transmission electron microscopy (TEM), X-ray diffraction (XRD), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), selected-area electron diffraction (SAED) and high-resolution TEM (HRTEM) were used to characterize the structure features and chemical compositions of the as-made nanorods. The results showed that the as-prepared nanorods is composed of CuO with diameter of 30-100 nm, and lengths ranging from 1 to 3 μm. The mechanism of formation of CuO nanorods was also discussed.     

喷射共沉淀法制备纳米铁酸钴及气敏性能表征

尖晶石结构的复合氧化物已经成为一类重要的气体敏感材料.本文采用喷射共沉淀法制备了纳米铁酸钴,使用TG-DTA、XRD和TEM分析了结构特征.研究了纳米铁酸钴的气敏特性并探讨了气敏机理.     

Preparation and characterization of NiO nanorods by thermal decomposition of NiC2O4 precursor

Synthesis of nickel oxide (NiO) nanorods was achieved by thermal decomposition of the precursor of NiC₂O₄ obtained via chemical reaction between Ni(CH₃COO)₂·2H₂O and H₂C₂O₄·2H₂O in the presence of surfactant nonyl phenyl ether (9)/(5) (NP-9/5) and NaCl flux. Transmission electron microscopy (TEM), X-ray diffraction (XRD), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), selected area electron diffraction (SAED) and high-resolution transmission electron microscopy (HRTEM) were used to characterize the structure features and chemical compositions of the as-made nanorods. The results showed that the as-prepared nanorods is composed of NiO with diameter of 10–80 nm, and lengths ranging from 1 to 3 micrometers. The mechanism of formation of NiO nanorods is also discussed.     

Synthesis of alpha-Fe nanoparticles by solventless thermal decomposition

A new preparation for highly crystalline and monodisperse Fe3O4 nanoparticle is reported. This synthesis requires the use of rather complicated procedures including delicate control of surfactants ratios and inert reaction conditions due to the toxic and unstable nature of the precursors none the less because thermal decomposition methods were tried to synthesize monodispersed inorganic nanocrystallites until very recently. The synthesis of Fe3O4 nanocrystallites by using Fe(+2)-oleate2 complex was studied. The Fe(+2)-oleate2 complex was prepared from the reaction of iron chloride and sodium oleate in water. The thermal decomposition of the complex at the reduced pressure (0.3 torr) and about 300 degrees was done without any solvent. We demonstrated that a new solventless synthesis of size- and shape-monodisperse Fe3O4 nanoparticles depends on the amount of Na-oleate. And it is possible to remove the oleate ligand using reduction process. We confirmed that the nanoparticles changed from Fe3O4 to alpha-Fe phase obtained higher magnetic properties and crystallites by a vibrating sample magnetometer (VSM) and x-ray powder diffraction (XRD). Removal of the organic surfactant and other volatile components surrounding Fe3O4 nanoparticles was detected by fourier transform infrared spectroscopy (FT-IR).     

Mössbauer effect studies and X-ray diffraction analysis of cobalt ferrite prepared in powder form by thermal decomposition method

Cobalt ferrite (Co_xFe_3?xO₄) is prepared in powder form by thermal decomposition of iron and cobalt salts and is analysed by X-ray diffraction and Mössbauer spectroscopic techniques. The variation of Mössbauer parameters, lattice parameters and crystallite size of the products formed with variation in the composition of Fe and Co ratios are studied. The studies confirm the formation of nano-size cobalt ferrite particles with defect structure and it is found to be maximum for the Fe : Co = 60 : 40 ratio of the initial precursor oxides.     

Preparation and characterization of cobalt ferrite by the polymerized complex method

Magnetic nanoparticles of Co-ferrite were prepared by the polymerized complex method. Heating in vacuum of a precursor solution containing citric acid (CA), ethylene glycol (EG) and cobalt and iron salts with a molar ratio of Co/Fe/CA/EG=1/2/9/22.5 at 130 °C produced a brownish transparent polymeric gel, which have been characterized by IR and NMR spectroscopy. The results of both techniques suggest two types of reactions: the formation of metal-CA complexes and successive esterification reactions between CA and EG. The organic fraction was removed by controlled thermal treatments (200–800 °C) whereby the bimetallic oxide was formed. The powders obtained were characterized by X-ray diffraction (XRD), vibrational sample magnetometry (VSM) and transmission electron microscopy (TEM). XRD analysis showed the presence of CoFe₂O₄ at 400 °C. The saturation magnetization values of the samples increased as a function of calcination temperature and reached a maximum of 79.8 emu/g at 800 °C. The TEM images showed spherical nanoparticles with sizes between 20 and 40 nm.     

化学共沉淀法制备MnZn铁氧体前驱物微粉及其性能

首先对Me(Me=Fe2+、Mn2+、Zn2+)在Me-NaOH-H2O体系中的沉淀行为进行了必要的热力学分析,在此基础上,通过化学共沉淀法制备了尖晶石型的MnZn铁氧体前驱物微粉。利用XRD、SEM对前驱物粉料的粒度分布、物相以及表面形貌进行了表征与测试,并结合TG-DSC(热重与差热扫描分析)对前驱物微粉的煅烧温度进行了分析。前驱物微粉的磁性能由振动样品磁强计(VSM)来表征。实验表明Me在Me-NaOH-H2O体系中共沉范围为10.0～10.7。在此pH范围内,配以一定的盐溶液流速及搅拌速度下,可直接制备出具有尖晶石结构的前驱物微粉,并有效地解决了共沉淀制粉中的洗涤困难的问题。前驱物粉的磁性能测试表明,比饱和磁化强度σs≈64.09A.m2/kg,比剩余磁化强度σr≈3.08A.m2/kg,矫顽力Hc≈0.51A/m。