Preparation of fibrous nickel oxide particles

1　INTRODUCTIONThenickeloxide (abbreviatedasNiOthereafter)isaversatilematerialwhichhasbeenfoundmanyap plicationsinindustrialfields .Itisusedasthekeymaterialinmanufactureofbatteryelectrode ,cata lyst,thermalsensitiveelement ,gassensitiveele ment,functionalceramics ,glass ,electroniccompo nentsandsoon[18] .At present,theapproachesavailableforultrafineNiOparticlesproductionincludecarbonylmethod ,laserchemicalmethod ,pyrolysisbymicrowave ,sol gelmethod ,pyrolysisbyultrason ic ,precipitation …     

镍纳米线的简易合成及其气敏性能(英文)

采用水热法,以聚乙二醇(PEG)作为辅助剂,通过先驱物NiC2O4·2H2O合成氧化镍纳米线,并通过SEM和XRD对样品的微观结构进行分析。实验结果显示:PEG对镍线的合成起重要作用,镍纳米线表现出良好的气敏性能。该形态使得氧化镍(NiO)可作为传感器的气敏材料得到应用。     

Facile synthesis of NiO nanowires and their gas sensing performance

The NiO nanowires were prepared by a facile PEG assisted hydrothermal method using NiC₂O₄·2H₂O as a precursor compound. The microstructure of the samples was characterized by SEM and XRD. The gas sensing properties of the NiO nanowires toward ethanol was also investigated. The results show that PEG plays a key role in the synthesis of wire-like NiO. The NiO nanowires show excellent sensing performances to ethanol gas. This morphology holds substantial promise for applying NiO as a potential gas sensing material for future sensor application.     

纤维状镍钴合金粉的制备

采用共沉淀热分解法制备了纤维状Ni Co合金固溶体粉末 ,讨论了反应机理 ,用XRD和SEM等分析手段对粉末形貌、组成进行了表征 ,分析了温度、浓度、表面活性剂对产率、前驱体粉末形貌、分散性等方面的影响 ,探讨了制备纤维状前驱体粉末的最佳工艺条件。结果表明 ,温度和浓度对沉淀率有一定影响 :温度升高 ,适当高的浓度及加入表面活性剂对前驱体粉末的形貌及分散性有较显著的影响。     

Epitaxial deposition of NiO film on a cube-textured Ni substrate by metal-organic chemical vapor deposition

NiO films have been epitaxially grown by metal-organic chemical vapor deposition (MOCVD) on a bi-axially textured Ni substrate using Ni(thd)₂ as a precursor. The NiO film was deposited at 470°C for 10 min at a deposition pressure of 10 Torr and oxygen partial pressure of 0.91 Torr. SEM and AFM observations for the deposited NiO film showed a smooth and dense morphology. X-ray rocking curve and φ-scan showed that the NiO film has a bi-axial texture with a (100)<001> orientation. The out-of-plane and the in-plane deviations were measured to be 4.2° and 6~7° from the FWHM of (200) and (111) planes, respectively.     

Effect of Water Vapor on the High-Temperature Oxidation of Pure Ni

The high-temperature oxidation behavior of pure Ni in air and Ar with and without 30?vol%H₂O at 1,000?°C was investigated to understand the effects of water–vapor on the resulting oxidation kinetics and scale structures. It was found that water–vapor significantly affected the morphology and scale structure of NiO. A duplex NiO scale with a powder-like outer and dense inner NiO layer developed when the Ni was oxidized in atmospheres containing water–vapor. The grain size of the dense inner NiO layer was much smaller than that formed in dry atmospheres. The growth of the powder-like NiO required outward diffusion of Ni and its continued formation occurred at the interface between the powder and dense NiO layers. The dense inner NiO layer grew outward and incorporated the powder-like NiO particles and the resulting grain size of the inner layer was smaller in the presence of water–vapor. The water–vapor is speculated to have prevented sintering of NiO particles during growth of the NiO scale.     

磁场对纳米MnZn铁氧体前驱体形貌的影响

采用SEM，XRD，TEM，TG等手段研究了磁场对共沉淀法制备纳米MnZn铁氧体前驱体形貌及晶态结构的影响。结果表明，随着磁感应强度增大并达到某一临界值时，纳米颗粒形貌由球状向链状转变，继续增加磁感应强度将获得针状、棒状或纤维状的颗粒，10T强磁场下获得棒状颗粒呈现单晶结构。热重分析表明10T磁场下获得的纳米颗粒由于单维尺寸增加而导致活性降低。根据晶体生长理论，讨论了磁场影响纳米颗粒形核和长大过程的机理。     

Fabrication of SiC by carbothermal-reduction reactions of mountain leather asbestos

Fibrous magnesium silicate (Mg₆Si₄O₁₀(OH)₈: mountain leather asbestos) of Serbian origin was used as Si precursor for the synthesis of SiC by carbothermal-reduction process. As a reducing agent, carbon (from various precursors) was used. Formation of β-SiC was confirmed by XRD and SEM/EDS analyses. Porous SiC particles obtained at 1873 K possess longish plate-like morphology. The results show that reduction reaction is assisted by liquid phase formation, as well as vapor phase transport, and that mountain leather asbestos can be very effective mineral precursor for preparation of silicon carbide.     

Generation of nanocrystalline NiO particles by solution combustion method and its Zn?NiO composite coating for corrosion protection

The nanocrystalline nickel oxide (NiO) particles have been successfully prepared by a simple, fast, economical, and eco‐friendly solution‐combustion method using Ni(NO₃)₂ · 6H₂O (oxidizer) and sugar (dextrose as fuel). The as‐prepared compound was calcined for an hour at different temperatures. The synthesized NiO was characterized by XRD, TGA, SEM/EDX, TEM, XPS, FT‐IR, and UV–Vis spectral methods. The crystallite sizes of the NiO particles were measured. Rietveld refinement of X‐ray data matches the cubic structure with space group of Fm3m (No. 225). The thermal behavior of as‐prepared compound was examined. Scanning electron micrographs show uniform cubic like morphology of NiO and its chemical composition was measured. The TEM results reveal that the particle sizes were in the order of 70–80 nm. The red shift was noticed in UV–Vis absorption spectra. As an application part the Zn? NiO composite coating was prepared by electrodeposition method and its corrosion behavior was analyzed by Tafel, impedance and anodic polarization in aggressive medium.     

Effect of Technical Parameters on Surface Morphology of Electrodeposition of Iridium Layer in Aqueous System

在水体系中利用直流电沉积的方法以IrCl3为主盐在铂基体上制备出了Ir层。利用SEM、EDS和XPS对不同工艺参数下所制备Ir层的表面形貌及成分进行了分析,并最终获得了最优的电沉积工艺条件。结果表明:IrCl3主盐浓度对Ir层形貌有较大影响,浓度太低时电沉积的铱层太薄,导致铱层易起皮或产生裂纹,故适当提高主盐的浓度有利于改善Ir层质量;在一定的pH值范围内,电沉积所制备的Ir层表面形貌差别不大,表面均比较平整,Ir颗粒比较均匀、致密;电流密度对Ir层表面形貌尤其是对Ir层结晶颗粒的大小和致密性影响较大;电沉积溶液的温度太低时,不能沉积出Ir层,温度太高时,则沉积出的Ir层粗糙、表面形貌不均匀。     

Synthesis and characterization of neodymium oxide nanoparticles

The nanometric precursors of neodymium oxide of various morphology from fibrous to well-dispersed spheroidal were prepared via a solvothermal reaction routes. The precursors and their thermal evolution to neodymium oxide phase were characterized by means of X-ray diffraction (XRD), transmission electron microscopy (TEM) and scanning electron microscopy (SEM). It was found that the reaction parameters, kind of solvent as well as neodymium salt used played a key role for the product formation of desired morphology and structure. Similarly, kind of neodymium oxide precursor determined the morphology and the crystal structure (haxagonal or cubic) of the final oxide. The potential application of Nd₂O₃ precursors prepared by solvothermal method as convenient material for preparation of homogeneous thin coatings on planar substrates is shown.     

氢还原硝酸银气溶胶制备纳米银粉(英文)

采用高频超声波发生器生成硝酸银气雾滴,然后用氢气还原硝酸银制备纳米银粉。研究前驱体浓度和反应温度对产物粒径、形貌和晶粒尺寸的影响。在200℃的氢气气氛中,以硝酸银为原料制得的纳米银粉中含有氧化物。当反应温度超过200℃时可以制得纯银粉;X射线衍射分析表明,所制得样品的晶粒尺寸为29～47nm。研究表明反应温度对产物的粒径有明显影响。随着前驱体浓度的增加,所得纳米粉末的晶粒尺寸增加。SEM观察表明,产物银粉呈球形,粒径为210～525nm。反应温度和前驱体浓度对产物粒径有明显影响。     

Hydrothermal synthesis of CeO2 nano-particles

Nano-crystalline particles of CeO₂ have been synthesized via a low temperature hydrothermal synthesis process. Two types of precursors were studied—cerium hydroxide and ceria acetate. The precursors were adjusted to a basic (pH 10) and acidic (pH 4) medium before hydrothermal treatment at various durations of 6, 12, 18, and 24 h at 250 °C using a Teflon-lined hydrothermal bomb. The synthesized samples were characterized using DTA/TGA, XRD and TEM. Based on the characterization results, both precursor systems produced crystalline ceria nano-particles after 6 h of hydrothermal synthesis at 250 °C. The average crystallite sizes were 6 and 15 nm for the hydroxide and acetate system, respectively. The acetate precursor system appeared to produce better particles in terms of crystallinity and morphology. Based on the DTA/TGA analysis, hydrothermal synthesis had been effective in reducing the amount of intermediate products. With increasing hydrothermal treatment duration of up to 24 h, the samples did not exhibit a remarkable improvement in properties. The synthesized nano-particles were subsequently heat treated at 500 and 1000 °C for 2 h. After the heat treatment, enhanced crystallinity and growth in crystallite size was observed, but particles appeared more agglomerated.     

SnO2 coated Ni particles prepared by fluidized bed chemical vapor deposition

A Fluidized Bed Metal–Organic Chemical Vapor Deposition (FB-MOCVD) process was developed for the growth of tin oxide thin films on large hollow Ni particles. Tetraethyl tin was used as tin source and dry air both as fluidization gas and oxidant reagent. The SnO₂ films were grown in a FBCVD reactor under reduced pressure (13.3 kPa) in the temperature range of 633–663 K. A series of specific experiments was carried out to optimize the design of the reactor and to determine the range of experimental parameters (flow rate, pressure, temperature) leading to good fluidization of the large hollow Ni particles used as base material. The SnO₂ films deposited on particles exhibited a dense nodular surface morphology similar to that previously observed on flat substrates. The relative thickness of the films was determined by EDS analyses and the real values were measured by SEM on cross-sections of particles. The SnO₂ films exhibit satisfactory thickness uniformity from one particle to another in the same batch and from run to run. XRD studies revealed that the films exhibited good crystallinity with the cassiterite structure. Traces of NiO were found at the SnO₂/Ni interface. Finally, the SnO₂ CVD coated-Ni particles were used as anodes in an electrochemical cell. The potential limit of oxygen evolution measured was that of the SnO₂ layer despite the initial porosity of the hollow Ni particles inherent to their preparation. This work is the first step towards the preparation of high specific surface area electrodes.     

Synthesis and characterization of Sm3+-doped CeO2 powders

Sm3 -doped CeO2 (denoted as Ce1-xSmxO2) powders with different morphologies were successfully synthesized via a precursor-growth-calcination approach, in which precursor was first synthesized by a hydrothermal method and Ce1-xSmxO2 powders were finally obtained through a calcination process. The products were characterized with X-ray diffractometry(XRD), field emission scanning electron microscopy(FE-SEM) and fluorescence spectroscopy. The results reveal that the Ce1-xSmxO2 powders obtained by calcining the precursors prepared in the absence and presence of poly(vinyl pyrrolidone) (PVP) exhibit bundle- and sphere-like morphology, respectively. The possible growth process was proposed by preparing a series of intermediate morphologies during the shape evolution of CeO2 based on the SEM image observation. It is also found that the luminescence intensity of bundle-like Ce1-xSmxO2 is enhanced in comparison with that of sphere-like one due to its special morphology.     

形貌控制法合成一种新型的纤维状镍钴合金粉末前驱体(英文)

通过选择性控制合成条件,制备一种新型的纤维状镍钴合金粉末前驱体。该前驱体中镍、钴摩尔配比精确。采用X-射线衍射仪(XRD)、扫描电镜(SEM)、红外光谱(FT-IR)和能谱(EDS)研究前驱体粉末的成分与形貌;考察溶液pH值、反应温度、金属离子浓度和表面活性剂对前驱体粉末的形貌和分散性的影响。结果表明:前驱体的形貌取决于前驱体中氨的含量,这种纤维状前驱体为一种复杂的含氨草酸镍钴复盐。形貌控制合成纤维状镍钴合金粉末前驱体的最佳条件为:氨作为配位剂和pH值调节剂,草酸为沉淀剂,反应温度为50～65°C,镍、钴离子总浓度为0.5～0.8mol/L,PVP为分散剂,溶液pH值控制在8.0～8.4.     

Electrochemical properties of NiO/Co-P nanocomposite as anode materials for lithium ion batteries

NiO/Co-P nanocomposite is prepared by an electroless cobalt plating technique. The as-prepared composite is characterized by means of X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDS), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) techniques. SEM and TEM images reveal that the NiO particles are about 200 nm in size, which are modified by Co-P nanoparticles of about 30 nm. The electrochemical properties as anode materials for lithium ion batteries are examined by cyclic voltammetry (CV) and discharge-charge tests. The results show that, compared with the bare NiO without electroless cobalt plating, NiO/Co-P nanocomposite exhibits a smaller polarization and a better rate capability, which is attributed to the Co-P nanoparticles.     

Synthesis and characterization of W-Cu nanopowders by a wet-chemical method

A wet-chemical process was employed to prepare W-Cu nanopowders. Precursors containing some tungstates were obtained by adding precipitants into a complex solution containing ammonium metatungstate and copper nitrate, afterwards spray-drying the complex solutions. The precursor powders were then calcined and hydrogen-reduced to convert into W-Cu powders. Phase constitution and morphology of the precursors, the calcined powders, as well as the reduced powders were characterized. Relations between the ratio of W to Cu in the complex solutions and the phase constitution of the calcined precursors were investigated. The effects of the reduction temperature and H₂ flow rate on the hydrogen reduction kinetics and the crystallite size of the W-Cu powder were also studied. It was shown that the wet-chemical process produces W-Cu powders with nanosized particles of about 100 nm. The composition of the calcined precursors varies with the ratio of W to Cu in the complex solution, and only CuWO₄ was found in the calcined precursors when the ratio of W to Cu is 74:26(wt.%). The reduction temperature and H₂ flow rate have a great influence on the hydrogen-reduction process and the crystallite size of the resulting W-Cu powders.     

金刚石表面非均匀形核法包覆氧化铝的动力学

采用非均匀形核法在金刚石颗粒表面包覆了一层Al2O3层,研究溶液pH值和Al(NO3)3的滴加量对其包覆率和覆层形貌的影响,分析其包覆的动力学方程。采用扫描电子显微镜(SEM)观察不同包覆阶段颗粒表面的覆层形貌。结果表明:当pH在4.5～5.5范围内,pH值越大,晶体长大系数越大,生长速率越快;溶液析晶过程受过饱和度影响,过饱和度越大,析晶驱动力越大。晶核孕育期受pH影响,滴加量相同的条件下,当pH在4.5～5.5范围内,pH值越大,晶核孕育期越短。     

固相块中微纳尺度Gd211粒子的控制及其对单畴GdBCO超导块材性能的影响

通过控制Gd211固相块烧结温度的方法,获得了系列具有不同显微组织结构的Gd211先驱固相块;在此基础上,采用顶部籽晶熔渗生长法,制备了系列单畴GdBCO超导块材。并对其熔渗生长前后之宏观形貌、显微组织结构、以及单畴GdBCO超导块材的磁悬浮力进行了研究。结果表明,只有当先驱固相块的微观结构满足：Gd211粒子均为球状或椭球状颗粒、平均粒径较小、气孔率适中的条件时,单畴GdBCO超导块材中的Gd211粒子平均粒径最小,样品的磁通钉扎力和磁悬浮力最大(约38.7 N,样品直径20 mm,测试温度77 K,永磁体直径20 mm,表面磁场0.5 T)。该研究结果对于如何从微观结构上控制固相先驱块和单畴REBCO超导块材中RE211粒子的形状、粒径大小、气孔率、以及提高其超导性能提供了科学的依据和思路。