Hollow CoFe₂O₄ nanospheres as a high capacity anode material for lithium ion batteries

Hollow structured CoFe?O? nanospheres were synthesized by a hydrothermal method. The uniform hollow nanosphere architecture of the as-prepared CoFe?O? has been confirmed by field emission scanning electron microscopy and transmission electron microscopy analysis, which give an outer diameter of 200-300 nm and a wall thickness of about 100 nm. CoFe?O? nanospheres exhibited a high reversible capacity of 1266 mA h g?1 with an excellent capacity retention of 93.6% over 50 cycles and an improved rate capability. CoFe?O? could be a promising high capacity anode material for lithium ion batteries.     

Facile synthesis of α-MnO2/graphene nanocomposites and their high performance as lithium-ion battery anode

α-MnO₂/graphene nanocomposites are synthesized via a facile wet-chemical route, and α-MnO₂ nanosheets are uniformly distributed on the surface of graphene. Their high performance as lithium ion battery anodes is obtained. Their reversible capacity at C/10 rate is up to 726.5 mA h/g, and maintains up to 635.5 mA h/g after 30 cycles. Such a performance can be partly attributed to high electron conductivity, excellent flexibility and high specific surface area of graphene. Also, α-MnO₂ nanostructures can play a role in preventing the pile of graphene nanosheets with the loss of their active surface area. The present results indicate that α-MnO₂/graphene nanocomposites have potential applications in lithium-ion battery anodes.     

Fabrication and structure characterization of MnCO3/α-Fe2O3 nanocrystal heterostructures

Novel MnCO₃/α-Fe₂O₃ nanocrystal heterostructures, with MnCO₃ nanorods 5-10 nm in diameter and 15-50 nm in length, grown onto the surfaces of the α-Fe₂O₃ nanohexahedrons sized around 30-50 nm, were fabricated via a two-step solvothermal route. The coalescent planes of the heterostructure for the MnCO₃ nanorod and the α-Fe₂O₃ nanohexahedron were determined to be (01?4) and (110), respectively. The formation of the MnCO₃ nanorods from the Mn contained amorphous flakes was tracked by transmission electron microscopy observations at various reaction stages, which suggested a rolling-broken-growth process. Evidenced by the comparative experimental result, the α-Fe₂O₃ nanohexahedrons played an important role in inducing the nucleation and growth of the hexagonal MnCO₃ nanorods on their surfaces.     

Facile synthesis and characterization of ZnFe2O4/α-Fe2O3 composite hollow nanospheres

ZnFe₂O₄/α-Fe₂O₃ composite hollow nanospheres were successfully fabricated via a facile one-pot solvothermal method, utilizing polyethylene glycol as soft template. X-ray diffraction and scanning electron microscopy analysis revealed that the prepared nanospheres with cubic spinel and rhombohedra composite structure had a uniform diameter of about 370 nm, and the hollow structure could be further confirmed by transmission electron microscopy. Energy dispersive X-ray, X-ray photoelectron spectroscopy and Fourier transform infrared techniques were also applied to characterize the elemental composition and chemical bonds in the hollow nanospheres. The ZnFe₂O₄/α-Fe₂O₃ composite hollow nanospheres show attractive light absorption property for potential applications in electronics, optics, and catalysis.     

Novel rose-type magnetic (Fe3O4, γ-Fe2O3 and α-Fe2O3) nanoplates synthesized by simple hydrothermal decomposition

Rose-type magnetic nanoplates (RTMNPs) were synthesized by a simple hydrothermal decomposition method where FeCl₂·4H₂O was solely used as a precursor. The synthesized nanoplates were characterized using XRD, FE-SEM, UV-vis absorption (reflectance) spectra and magnetic hysteresis loops. The resulting nanoplates were in the ranges of size 350-500 nm and width 60-70 nm with high crystallinity, purity (shown by XRD) and reproducibility. These iron oxide nanoplates have a great potential in magnetic nanodevices and biomagnetic applications.     

Cobalt(Ⅱ) coordination polymers as anodes for lithium-ion batteries with enhanced capacity and cycling stability

Coordination polymer Co-btca(H4 btca = 1,2,4,5-benzenetetracarboxylic acid) was synthesized using a simply hydrothermal method.In particular,the as-prepared Co-btca was applied as an anode material for lithium-ion battery for the first time.Single crystal X-ray diffraction results indicated that the asprepared Co-btca displayed unique layer structure,which was beneficial to transport Li ions and electrons.Also,owing to the porous structure and appropriate specific surface area,Co-btca electrode delivered a reversible capacity of 801.3 m A h/g after 50 cycles at a current density of 200 m A/g.The reversible capacity of 773.9 m A h/g was maintained after 200 cycles at a current density of 500 m A/g,exhibiting enhanced cycle stability.It also showed improved rate performance,making it a promising anode material and a new choice for lithium-ion batteries.     

微波水解法制备针形α-Fe2O3纳米粒子

为了研究微波在纳米晶粒形成中的作用,用FeCl     

树枝状α-Fe2O3的制备与生长过程研究

以K4[Fe(CN)6]、PEG400和H2O2为原料,通过水热法制备了树枝状α-Fe2O3,并采用XRD、SEM、TEM、SAED和Raman技术对其微观形貌和结构进行了分析。研究发现α-Fe2O3树枝的主干生长方向为[101-0],分枝的生长方向为[11-00]和[011-0],进一步对树枝状α-Fe2O3的生长过程和形成机理进行了讨论。     

Electrospinning route for α-Fe2O3 ceramic nanofibers and their gas sensing properties

In this paper, α-Fe₂O₃ ceramic nanofibers were prepared by electrospinning poly(vinyl alcohol)/Fe (NO₃)₃·9H₂O composite nanofibers and followed by calcination. The morphologies and structures of the as-prepared samples were characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR). The gas sensing properties of the sensor based on the as-prepared α-Fe₂O₃ nanofibers were investigated in detail. The experimental results exhibited that our product held rapid response-recovery and high sensitivity characteristics to ethanol vapor. The response and recovery time of the sensor to C₂H₅OH vapor (from 100 to 5000 ppm) are about 3 and 5 s, respectively.     

Uniform α-Fe2O3 nanotubes fabricated for adsorption and photocatalytic oxidation of naphthalene

Uniform α-Fe₂O₃ nanotubes with small aspect ratio were successfully fabricated by a hydrothermal method. In situ Fourier-transform infrared spectroscopy was used to study the mechanistic details of adsorption and photocatalytic oxidation of naphthalene over theα-Fe₂O₃ nanotubes. A possible degradation mechanism of naphthalene was proposed.     

Preparation and characterization of hollow α-Fe2O3 irregular microspheres

Hollow α-Fe₂O₃ irregular microspheres were prepared at 160 °C from a hydrolyzing Fe(ClO₄)₃ solution by adding sodium polyanethol sulphonate. The particles were characterized by ⁵⁷Fe Mössbauer, X-ray diffraction, Fourier transform infrared spectroscopy, field emission scanning electron microscopy and energy dispersive X-ray spectroscopy. The walls of these hollow particles consisted of elongated subunits composed of elongated and thin α-Fe₂O₃ rods. The precipitation of hollow α-Fe₂O₃ irregular microspheres was governed by the preferential adsorption of sulphonate/sulphate groups. The lateral aggregation of elongated thin rods and subunits also played an important role in the formation of hollow α-Fe₂O₃ irregular microspheres.     

熔盐法制备α-Fe2O3一维纳米针状材料

采用自制的大面积四靶溅射设备,并结合基片的调速双轴旋转,成功研制出3英寸双面CeO2薄膜及YBa2Cu3O7-δ(YBCO)薄膜.通过对所制备薄膜的微观结构、表面形貌以及电性能的分析测试,得到的CeO2薄膜与YBCO薄膜具有良好的c轴外延取向,CeO2薄膜的(002)峰与YBCO薄膜的(005)峰FWHM均小于1°.薄膜厚度均匀性良好,厚度起伏在±5%以内.YBCO薄膜Tc分布在88.5～90K,△TC＜1K,Jc＞1×106A/cm2,Rs(10GHz,77K)两面分别为0.53mΩ和0.56mΩ,能较好地满足微波器件研制中的需要.     

Microwave-assisted synthesis and humidity sensing of nanostructured α-Fe2O3

Nanocrystalline α-Fe₂O₃ has been prepared on a large-scale by a facile microwave-assisted hydrothermal route from a solution of Fe(NO₃)₃·9H₂O and pentaerythritol. A systematic study of the morphology, crystallinity and oxidation state of Fe using different characterization techniques, such as transmission electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy was performed. It reveals that nanostructured α-Fe₂O₃ comprises bundles of nanorods with a rhombohedral crystalline structure. The individual nanorod has 8-10 nm diameter and ∼50 nm length. The as-prepared nanostructured α-Fe₂O₃ (sensor) gives selective response towards humidity. The sensor shows high sensitivity, fast linear response to change in the humidity with almost 100% reproducibility. The sensor works at room temperature and rejuvenates without heat treatment. The as-prepared nanostructured α-Fe₂O₃ appears to be a promising humidity sensing material with the potential for commercialization.     

不同形貌α-Fe2O3的水热法制备及性能研究

以Fe(NO_3)_3·9H_2O为原料,聚乙烯吡咯烷酮作为表面活性剂,NaOH、Na_2CO_3、CH_3COONa为形貌改变剂,采用水热法制备出不同形貌的α-Fe_2O_3,并研究了不同因素对产物形貌的影响。利用SEM、EDS、XRD、FTIR等手段对其物相及微观形貌进行表征,并探讨其生长机理。通过光催化降解酸性大红模拟废水考察不同形貌α-Fe_2O_3的光催化性能,实验结果表明,类桑葚状α-Fe_2O_3对酸性大红模拟废水的降解效果最好,降解率高达99.01%,具有潜在的光催化应用前景。     

Green synthesis of hematite (α-Fe2O3) submicron particles

Iron oxide microparticles have been synthesized through a green technique using hydrogen peroxide under sunlight irradiation. The X-ray powder diffraction measurement shows that these particles are hematite (α-Fe₂O₃). The microstructure and particle size were investigated using scanning electron microscopy. The magnetic characterization shows the presence of Morin transition at about 258 K, which is very close to the normal value (263 K) of bulk hematite. These hematite particles show typical antiferromagnetic behavior at low temperature and weak ferromagnetic behavior at room temperature.     

低温水热法制备形貌可控纳米α-Fe2O3的研究

以FeCl3.6H2O、尿素为主要原料,以聚乙烯吡咯烷酮(PVP)或十二烷基苯磺酸钠(SDBS)为表面活性剂,乙二醇为分散剂,采用低温水热法制备了不同形貌的α-Fe2O3,分析讨论了加入表面活性剂及乙二醇作为分散剂对产物形貌的影响,采用热重-差热分析(TG-DTA)研究样品的热分解过程,利用X射线衍射(XRD)、扫描电镜(SEM)对样品成分、粒度、形貌等进行了表征分析。结果表明:表面活性剂和分散剂可以控制颗粒的形貌,加入不同的表面活性剂、分散剂及控制其用量可以得到形貌不同的纳米α-Fe2O3。     

Template-free synthesis and characterization of snowflake-like α-Fe2O3 microstructures

Single-crystalline α-Fe₂O₃ with a micro-snowflake-like morphology has been synthesized though a hydrothermal reaction in a K₃[Fe(CN)₆] solution without the assistance of any template or surfactant. The morphology and structure of the synthesized hematite were characterized in detail by X-ray diffraction, scanning electron microscopy and transmission electron microscopy. A possible growth process of α-Fe₂O₃ crystals has been proposed, and NaOH plays a crucial role in the formation of the snowflake-like structure. Additionally, magnetic investigations show that the α-Fe₂O₃ crystals exhibit a weakly ferromagnetic property at room temperature with a coercive force of 134 Oe and remnant magnetization of 0.67 emu g^− 1.     

Preparation and characterization of γ-Fe2O3/ZnO composite particles

γ-Fe₂O₃/ZnO composite particles were prepared via a simple solution method using surface-modified γ-Fe₂O₃ nanoparticles as seeds. The phases and purity of the as-prepared γ-Fe₂O₃/ZnO composite particles were characterized by XRD analysis, and the morphology was studied by SEM, which showed that the γ-Fe₂O₃/ZnO composites are of typical sphere-like morphology with diameters in the range of 300-400 nm. The γ-Fe₂O₃/ZnO composites exhibit magnetic response to an external magnet field and efficient characteristic emissions of ZnO under UV excitation, respectively, indicating that these nontoxic, emissive and magnetic nanoparticles may find use as chemical/biological sensors especially in areas that directly impact human health.     

Strain-regulated sensing properties of α-Fe2O3 nano-cylinders with atomic carbon layers for ethanol detection

The sensitivity of ethanol sensor is of paramount importance in a variety of areas,including chemical production with ethanol,alcohol testing for driving safety,etc.Herein,α-Fe₂O₃ nano-cylinders with atomic carbon layers are synthesized,for the first time,through in-situ catalytic chemical vapor deposition combined with hydrothermal techniques for the detection of ethanol.The reported α-Fe₂O₃@C nano-cylinders with double surficial strain effects deliver an ethanol detection sensitivity of 8 times as compared with α-Fe₂O₃ nano-cylinders,10 times higher as compared with its detection sensitivity to ammonia,para-xylene,methanol and benzene.The sensor also exhibits over-14-day operation stability and the minimum detection limit of 10 ppm.To our best knowledge,the performances surpass those of previously reported α-Fe₂O₃.Such attractive performances are attributed to the enhanced charge transfer in α-Fe₂O₃ owing to the double surficial strain effects of α-Fe₂O₃@C nano-cylinders and the efficient adsorption of ethanol with atomic carbon layers.     

Preparation and combustion properties of α-Fe2O3 coated Zr particles

Zirconium particles with irregular morphology and broad size distribution were uniformly coated by spherical α-Fe₂O₃ crystal grain via a facile route without polymer or surfactant as directing agents. The synthesized α-Fe₂O₃/Zr composite particles were characterized by X-ray diffraction, scanning electron microscopy, energy dispersion X-ray, UV-vis spectroscopy and Raman spectroscopy. The synthesis mechanism could be explained by cooperated heterogeneous nucleation and solid state transformation reaction. The combustion properties of α-Fe₂O₃/Zr composite particles were investigated. Compared with Zr particles, the combustion lasting time decreased from 16 s of Zr particles to 0.13 s of α-Fe₂O₃/Zr composite particles, and the top point of temperature reached in combustion increased from 2004 °C of Zr particles to 2378 °C of α-Fe₂O₃/Zr particles.