Synthesis and magnetic characterization of nanostructures N/WS2, where N = Ni, Co and Fe

Bimetallic sulfides N/WS₂ (N = Ni, Co and Fe) with atomic ratio N/W + N = 0.85 were prepared by the impregnated thiosalt decomposition (ITD) technique and treated under reducing atmosphere at 400 °C. The composition, morphology, structure and magnetic properties of the samples were characterized by energy dispersive spectrometry (EDS), scanning electron microscopy (SEM), X-ray diffraction (XRD) and vibrating sample magnetometry (VSM) measurements respectively. The Co samples reduced by 24 h exhibited the highest coercivity value.     

Synthesis of aluminum nitride fibres from aluminum silicate fibres by carbothermal reduction method

Aluminum nitride (AlN) fibres were synthesized by carbothermal reduction of aluminum silicate fibres and carbon black in a flowing nitrogen atmosphere. XRD and SEM were employed to study the phase structure, chemical composition and morphologies of the products. It is suggested that aluminum silicate fibres can be converted into AlN fibres by carbothermal reduction. SEM confirmed that the fibres maintained the morphologies of aluminum silicate fibres during reduction, but their details of surface have been altered. A carbothermal nitriding model of the aluminum silicate fibres has been developed.     

Adsorption of Ni on Si(1 0 0) surface

The chemisorption of one monolayer Ni atoms on ideal Si(1 0 0) surface is studied by using the self-consistent tight binding linear muffin-tin orbital method. Energies of adsorption systems of Ni atoms on different sites are calculated. It is found that Ni atoms can adsorb at fourfold site above the surface and bridge site below the surface. The adsorption of Ni atoms can readily diffuse and penetrate into the subsurface. A Ni, Si mixed layer might exist at the Ni-Si(1 0 0) interface. The layer projected density states are calculated and compared with that of the clean surface. The charge transfers are also investigated.     

氮杂碳包Fe、Co、Ni材料的合成及介电特性

采用交流电弧法,在氮气氛下合成了氮杂碳包金属Fe、Co、Ni纳米晶.采用热重分析(TG)法测量了合成材料中Fe、Co、Ni等金属的含量.借助于透射电子显微镜(TEM)、粉末衍射法(XRD)、X光电子能谱法(XPS)等分析手段进行了合成材料的形貌观察和结构表征.采用反射-传输网络参数法在HP8510B矢量网络分析仪上进行了材料复介电常数测量.结果表明氮杂碳包金属Fe、Co、Ni纳米晶在8.2～12.4GHz频率范围内具有复介电特性,其损耗角正切tgδε=ε"/ε′平均值分别达到0.9,0.31和0.30,显示出氮杂碳包金属Fe、Co、Ni纳米晶对微波具有较好的介电损耗特性.     

Synthesis and study of structural,thermal, optical and magnetic properties of stabilized Mn1−x Ni x O system (0·01 <x < 0·30)

A novel chemical passivation route is established to obtain microcrystalline solid solutions of binary oxidé system Mn_1−x Ni _x O (0·01 <x < 0·30). During the passivation process, controlled thermal decomposition of manganous oxalate is carried out to obtain pure MnO and its subsequent reaction with NiO in oxygen-free nitrogen resulted in microcrystalline powder of these solid solutions. The powder is thoroughly characterized by various physicochemical techniques such as XRD, DTA/TG/DTG, diffused reflectance spectra, magnetic susceptibility, TEM, XPS etc. The observed processing-structure-property correlations confirmed the improved thermal stability of these powders (relative to pure MnO) in air. The important role of dopant paramagnetic Ni²⁺ ions in enhancing the passivation of the bulk Mn²⁺ species is explained on the basis of the formation of mixed oxide complex species on the surface of these microcrystalline powders.     

Synthesis and electrochemical characterisation of electrospun lithium titanate ultrafine fibres

The phase pure spinel lithium titanate (Li₄Ti₅O₁₂) in the form of ultrafine fibre was synthesised by the combination of sol–gel and electrospinning techniques. The electrospinning process for the preparation of Li₄Ti₅O₁₂ precursor was optimised to get bead-free fibrous mat with uniform thickness. Crystalline Li₄Ti₅O₁₂ in the form of ultrafine fibre was synthesised by the calcination of the precursor at 800 °C in air for 4 h. The material was characterised by X-ray diffraction, Raman spectroscopy and scanning electron microscopy and subsequently evaluated as an electrode active material using Li metal as a counter electrode. The material exhibited a first cycle specific capacity of 154 mAh g^?1 with good rate capability and cyclability.     

Synthesis of highly stable graphite-encapsulated metal (Fe, Co, and Ni) nanoparticles

Graphite-encapsulated metal magnetic nanoparticles have been attracted for biological applications because of their high magnetization of the encapsulated particles. However, most of the synthetic methods have limitations in terms of scalability and economics because of the demanding synthetic conditions and low yields. Here, we show that well-controlled graphite-encapsulated metal (Fe, Co, and Ni) nanoparticles can be synthesized by a hydrothermal method, simply by mixing metal source with sucrose as a carbon source. The saturation magnetization (Ms) values of Fe/C, Co/C, and Ni/C were 86.6, 43.8, and 113.1?emu/g, respectively. The Fe/C and Ni/C showed higher Ms values than bulk Fe₃O₄ (75.5?emu/g). The graphite-encapsulated metal nanoparticles showed good stability against acid and base environments.     

Preparation of self-supporting nickel targets from Ni, Ni and Ni

The investigation of the distribution of the fusion-barrier height by heavy-ion collisions requires thin self-supporting targets. To increase the accuracy of the measurement the thickness and homogeneity has to be known as precisely as possible.We prepared the self-supporting nickel foils out of the isotopes ⁵⁸Ni, ⁶⁰Ni and ⁶¹Ni. The resulting targets were between 75 and 105 μg/cm^² thick. The foils were produced on copper backing by electron-beam gun evaporation and by extracted ion-beam sputtering, both in high vacuum. To obtain self-supporting nickel foils the copper was removed by etching. We will discuss and compare both methods.     

Synthesis and Characterization of ZnO and Ni Doped ZnO

ZnO and Zn_1−x Ni _x O (x=1, 2 and 3 mol %) were prepared by the sol gel via ultrasonication method with the Ni concentrations of 1, 2, and 3 mol %. The samples were characterized by high resolution scanning electron microscopy, X-ray diffraction, TEM, and UV-DRS spectroscopy. The XRD spectrum reveals that all the samples are of hexagonal wurtzite structures. The crystallite size decreases with increasing Ni concentration. The Ni concentration is determined by the energy dispersive X-ray technique. From the UV spectra, upon Ni doping the characteristic peak is red shifted which is the indication of decrease in the band gap. Magnetization measurements reveal that Ni doped ZnO shows paramagnetism with enhanced Ni concentration.     

Magnetic,Mössbauer and electrical properties of Ti-substituted Ni0·3Zn0·7Fe2O4

The effect of addition of Ti⁴⁺ in small amounts (1/2, 1, 2, 5, 10% by weight of TiO₂) under oxidising conditions on magnetisation, M?ssbauer spectra and resistivity of Ni_0·3Zn_0·7Fe₂O₄ is studied. Analysis of the magnetic data on the basis of 3 sublattice Yafet-Kittel model gives the transfer rate of Fe³⁺ ions between theA andB sublattices, the distribution of Ti⁴⁺ and vacancies between them and the five exchange constants of Ni-Zn ferrite. The observed M?ssbauer spectra at room temperature are quadrupole doublets and those at liquid nitrogen temperature are magnetic sextets with large relaxation effects. The resistivity shows an increase by about two orders of magnitude due to Ti⁴⁺ addition. This paper is dedicated to the memory of the late Dr N S Satya Murthy.     

Ti2Cu0.8Ni0.2合金的氢化与晶化

对晶态及非晶态Ｔｉ２Ｃｕ０．８Ｎｉ０．２贮氢合金进行氢化。若吸氢程度不高，氢原子是填隙原子，进入钛四面体，对合金结构影响不大，保持晶态及非晶态状态。     

Evolution of interface diffusion and structure of Ni films sputter-deposited on Si(0 0 1)

Ni films were deposited on Si(0 0 1) substrates at 190°C by dc plasma-sputtering in Ar gas in order to investigate the Ni diffusion phenomena into the substrate and its effect on the structure of Ni films. The deposition time was 10, 15 or 30 min. The Ni/Si samples were studied by cross-sectional transmission electron microscopy and Rutherford backscattering. Ni adatoms are confirmed to diffuse into the Si substrate forming a diffusion layer. The diffusion layer consists of two regions. The first one is of homogeneous thickness and locates adjacent to the interface of film and substrate. The second one consists of several isosceles triangles with vertex angle of about 70° standing on the front of first region. Both the thickness of the first region and the number of triangles in the second region increase with increasing deposition time. The compositional ratio of Ni to Si in the diffusion layer is 1.3±0.1. The Ni films have a lot of voids at the interface and a rough surface. The density of the film is estimated to be 25% lower than that of bulk Ni. The thickness of the Ni films does not increase linearly with deposition time.     

镍纳米管阵列的电沉积合成及其磁学性能表征

以氧化铝膜为模板、金属汞为电阴极,采用简单的直流电沉积方法制备出高度有序的镍纳米管阵列。利用扫描电子显微镜、透射电子显微镜、选区电子衍射、能谱仪、X射线粉末衍射和样品振动磁强计对样品进行形貌表征、成分及磁性能分析。结果表明,阵列中的镍纳米管彼此平行,尺寸均匀,纳米管外径为260～360nm;镍纳米管阵列表现出良好的磁各向异性,其易磁化方向垂直于镍纳米管阵列。以金属汞为电阴极是易形成纳米管的关键条件。     

Synthesis of xLi2MnO3·(1 − x)LiMO2 (M = Cr, Mn, Co, Ni) nanocomposites and their electrochemical properties

A series of 0.4Li₂MnO₃·0.6LiMO₂ (M = Ni_1/3Co_1/3Mn_1/3 and Ni_1/3Cr_1/3Mn_1/3) cathode materials are prepared by a co-precipitation method with subsequent quenching. Crystal structures of samples are investigated by X-ray diffraction and electron diffraction, which show a co-existence of rhombohedral and monoclinic structures indicating nanocomposite characteristics of the sample of 0.4Li₂MnO₃·0.6Li Ni_1/3Cr_1/3Mn_1/3O₂. The average particle size distributions of the powders are analyzed to be an order 400 and 100 nm. The 0.4Li₂MnO₃·0.6LiMO₂ (M = Ni_1/3Co_1/3Mn_1/3 and Ni_1/3Cr_1/3Mn_1/3) electrodes, which consist of a well balanced partial phases of rhombohedral and monoclinic can deliver a high reversible capacity of 220-230 mAh/g during an extended cycling.     

纳米Ni0.5Zn0.5Fe2O4铁氧体的制备及电磁损耗特性研究

采用NH4 HCO3与FeCl3·6H2O、Zn(NO3)2·6H2O、Ni(NO3)2·6H2O进行室温固相反应制得Fe(OH)3、Zn3(OH)4CO3·H2O、Ni3(OH)4CO3·4H2O混合前驱物,先经微波加热,再热分解制得纳米粉体.利用激光粒度分析仪、XRD、SEM和TEM对分解产物进行了表征,获得了形貌为球形、颗粒分布均匀、平均粒度为62nm、尖晶石结构的纳米Ni0.5Zn0.5Fe2O4复合铁氧体粉体.经测试样品的相对介电常数和相对磁导率后,发现该纳米铁氧体粉体在100～1800MHz内具有良好的电损耗和磁损耗性能.     

Synthesis and characterisation of alumina fibres using organic/inorganic composite sol

Abstract

The polyvinyl butyral–Al(NO₃)₃ composite sols and alumina fibres were synthesised by the sol–gel process in an aqueous solution using the polyvinyl butyral (PVB) and Al(NO₃)₃.9H₂O (AN). The viscosity of PVB–AN composite sol increased with increasing AN content and aging time when it was laid at room temperature. The addition of AN leads to the formation of new weak peak and the deviation of diffraction angle to higher degrees according to the X-ray diffraction patterns (XRD). The exothermic peak of PVB disappeared and a weak endothermic peak was observed in differential scanning calorimetry curves of composite powders. The XRD pattern of fibres sintered at 1200°C showed the formation of α-alumina and the fibres showed smooth surface and uniform diameter.     

Synthesis and structure refinement of layered double hydroxides of Co, Mg and Ni with Ga

Homogeneous precipitation by urea hydrolysis results in the formation of highly ordered layered double hydroxides of divalent metal ions (Co, Mg, Ni) and Ga. Structure refinement shows that these carbonate containing layered hydroxides crystallize with rhombohedral symmetry (space group R-3m) in the structure of the 3R ₁ polytype. An analysis of the structure shows that, coulombic attraction between the layer and interlayer remains invariant in different layered hydroxides, whereas the strength of hydrogen bonding varies. The Ni-Ga LDH has the weakest hydrogen bonding and Co-Ga, the strongest, as reflected by the layer-interlayer oxygen-oxygen distances. The poor polarity of the OH bond in the Ni-Ga hydroxide points to the greater covalency of the (M²⁺/M′³⁺)-oxygen bond in this compound as opposed to the Co-Ga hydroxide. These observations are supported by IR spectra.     

Synthesis and properties of A6B2(OH)16Cl2·4H2O (A = Mg, Ni, Zn, Co, Mn and B = Al, Fe) materials for environmental applications

Double layered hydroxide materials of composition A₆B₂(OH)₁₆Cl₂·4H₂O (A = Mg, Ni, Zn, Co, Mn and B = Al, Fe) were synthesized by chemical precipitation at 60 °C. Different levels of crystallinity and ordering degree were observed depending upon the chemical environment or the combination between divalent and trivalent cations. The results from high-resolution transmission electron microscopy revealed that nanostructured layered samples were obtained with interplanar spacing compatible with previous literature. Raman scattering was employed to investigate the complex band structure observed, particularly the lattice vibrations at lower frequencies, which is intimately correlated to the cationic radius of both divalent and trivalent ions. The results showed that strongly coordinated water and chloride ions besides highly structured hydroxide layers have a direct influence on the stability of the hydrotalcites. It was observed that transition and decomposition temperatures varied largely for different chemical compositions.