Fe, Co, Ni-聚合物-C复合催化剂的制备及对乙醇电催化氧化性能研究

采用模板聚合物与金属离子配位-碳粉负载-还原方法得到的纳米复合材料P-M-C (P为聚合物, M为Fe, Co, Ni金属纳米颗粒, C为碳粉XC72). 利用红外光谱(IR)对中间产物进行了表征, 结果表明所制物质为目标产物P; 透射电镜(TEM)结果表明Fe, Co, Ni纳米粒子粒径多数为20～30 nm, 部分在10 nm左右, 纳米粒子均匀地分散在聚合物P上; 扫描电镜的能谱(SEM-EDS)分析结果证实了Fe, Co, Ni三种元素的存在. 通过循环伏安和计时电流法研究表明, 碱性介质中P-M-C复合催化剂对乙醇电化学氧化具有高催化活性和稳定性; 反向高效液相色谱(HPLC)结果表明乙醇氧化后的产物部分为乙醛和乙酸的混合物.     

Synthesis,characterization and properties of magnetic colloids supported on chitosan

This work proposes the synthesis, characterization and investigation of the stabilization capabilities of chitosan doped with magnetic nanoparticles. Nanoparticles of Fe, Co, Co(II,III) oxide, Ni and Ni/Ag mixture in 2-propanol were synthesized by chemical liquid deposition and the incorporation on the polymeric matrix was performed by solvated metal atom dispersion. Colloids and nanoparticles supported on chitosan were characterized by ultraviolet, Fourier-transform infrared, thermogravimetric analysis, electron diffraction X-ray and magnetic behaviour; transmission and field electronic scanning electron microscopy. The particle size distribution of colloids ranges from 6 to 50 nm with low particle stability due to flocculation after 120 days. The nanoparticles supported on chitosan had a particle size distribution of approximately between 10 and 80 nm, with low particle distribution; however, these particles do not flocculate because the matrix increases the stabilization of nanoparticles. All compounds present superparamagnetic behaviour at low temperature.     

Fabrication of Ni nanoparticles by selective oxidation of permalloy thin film during imidization of polyamic acid

Ni nanoparticles embedded in a polyimide (PI) matrix were fabricated by selectively oxidizing a layer of Ni(80)Fe(20) metal film sandwiched between two PI precursor layers. Ni nanoparticles, formed in a monolayer between two PI layers, had an average particle size of approximately 5 nm. X-Ray photoelectron spectroscopy confirmed that Fe in the film was preferentially consumed, resulting in the formation of Ni nanoparticles.     

Electrospinning preparation, characterization and magnetic properties of cobalt-nickel ferrite (Co(1-x)Ni(x)Fe2)O4) nanofibers

Uniform Co(1-)(x)Ni(x)Fe(2)O(4) (x=0.0, 0.2, 0.4, 0.6, 0.8 and 1.0) nanofibers with average diameter of 110 nm and length up to several millimeters were prepared by calcination of electrospun precursor nanofibers containing polymer and inorganic salts. The as-spun and calcined nanofibers were characterized in detail by TG-DTA, XRD, FE-SEM, TEM, SAED and VSM, respectively. The effect of composition of the nanofibers on the structure and magnetic properties were investigated. The nanofibers are formed through assembling magnetic nanoparticles with poly(vinyl pyrrolidone) as the structure-directing template. The structural characteristics and magnetic properties of the resultant nanofibers vary with chemical composition and can be tuned by adjusting the Co/Ni ratio. Both lattice parameter and particle size decrease gradually with increasing nickel concentration. The saturation magnetization and coercivity lie in the range 29.3-56.4 emu/g and 210-1255 Oe, respectively, and both show a monotonously decreasing behavior with the increase in nickel concentration. Such changes in magnetic properties can mainly be attributed to the lower magnetocrystalline anisotropy and the smaller magnetic moment of Ni(2+) ions compared to Co(2+) ions. Furthermore, the coercivity of Co-Ni ferrite nanofibers is found to be superior to that of the corresponding nanoparticle counterparts, presumably due to their large shape anisotropy. These novel one-dimensional Co-Ni ferrite magnetic nanofibers can potentially be used in micro-/nanoelectronic devices, microwave absorbers and sensing devices.     

Reversed-phase HPLC determination of Co(II), Ni(II) and Fe(III) as their 2-(2-thiazolylazo)-5-dimethylaminophenol chelates

The optimum chromatographic separation conditions for Co(II), Ni(II), and Fe(III) chelates with 2-(2-thiazolylazo)-5-dimethylaminophenol (TAM) were investigated. The compositions of chelates were also determined by the HPLC method and thus the possible structure of chelates was given. A precolumn derivatization method was used, followed by separation on an octyl-bonded silica stationary phase with a methanol-tetrahydrofuran-water (40:9:51, v/v/v) mobile phase containing pH 5.8 acetate buffer and 1 x 10(-4)M TAM. The detection limits of Co(II), Ni(II), and Fe(III) at 560 nm are 0.03, 0.02 and 0.1 ng (S N = 2 ), respectively. They can be determined by means of the proposed method without interference from other common metal ions and have been determined in five standard alloys with satisfactory results.     

核壳结构Ni0.5Zn0.5Fe2O4/PANI复合纳米材料的制备及表征

采用微乳液法制备出Ni0.5Zn0.5 Fe2O4纳米颗粒以及Ni0.5Zn0.5Fe2O4/PANI核壳结构复合纳米材料,借助FT-IR、XRD、SEM、TEM、VSM等分析手段研究了材料的形貌、结构与磁性能.结果表明:得到的Ni0.5Zn0.5Fe2O4纳米颗粒平均粒径为20hm左右,Ni0.5Zn0.5 Fe2O...     

Synthesis of Nano-catalysts by Induction Suspension Plasma Technology (SPS) for Fischer–Tropsch Reaction

Nanometric catalysts were synthesized through induction suspension plasma technology (SPS) for application in the Fischer–Tropsch synthesis (FTS). Carbon-supported single metal catalysts (Co/C, Fe/C), bimetallic formulations (Co–Fe/C), and ternary (Co–Fe–Mo and Co–Fe–Ni) systems have been considered in this work. SPS has been selected because it simultaneously allows for: (1) atomizing and generating metallic nanoparticles; (2) creating particularly Fe carbides, which are important in Fe-based FTS reaction mechanism; (3) in situ production of the nanometric graphitic-carbon matrix; and (4) saving time in catalyst synthesis, limiting sample preparation steps and eliminating post synthesis treatment before use. Porosity measurements by the Brunauer–Emmett–Teller method indicate that the samples are essentially non-porous. The synthesized catalysts characterized by X-ray Diffraction analysis show the presence of both metallic and carbidic species. The graphitic-carbon matrix has substantial structural defects that make it partly amorphous. Scanning Electron Microscopy analysis coupled with Energy Dispersive X-ray Spectroscopy mapping shows uniform dispersion of the metal moieties in the carbon support. Analysis by Transmission Electron Microscopy imaging displays metal nanoparticles with mean particle size within the 9–15 nm range enveloped in the carbon matrix.     

Preparation and characterization of ultrafine co and ni particles in a polymer matrix

A facile route for in situ synthesis of Co and Ni nanoparticles in a preorganized polyacrylamide gel is reported. Metal-polymer composites were prepared by gamma-irradiation at room temperature. The Co nanoparticles were roughly 3-5 nm in size and were stable in the polymer matrix in the presence of air. The presence of Co and Ni nanoparticles was established by their ability to transfer an electron to methyl viologen {paraquat: 1,1'-dimethyl 4,4'-dipyridinium dichloride; MV(2+) (Cl(-))(2)}. The Co and Ni nanoparticles were probed for their magnetic characteristics by a superconducting quantum interferometer device (SQUID) magnetometer and display a low superparamagnetic blocking temperature T(B) of about 13 and 10 K, respectively. The field-dependent magnetic behavior below T(B) displays the standard features corresponding to superparamagnetism, as expected for very small Co and Ni crystallites. This also suggests that particles are polycrystalline in nature.     

Second derivative spectrophotometric method for simultaneous determination of cobalt, nickel and iron using 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol

A simple, sensitive and rapid derivative spectrophotometric method using 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol (5-Br-PADAP) has been developed for simultaneous determination of Co(II), Ni(II) and Fe(II) which have very similar chemical behavior and appear together in many real samples. The complexes of all these metal ions with 5-Br-PADAP were formed immediately at pH 7.0 ammonium acetate buffered solution and were stable for at least 24 h. Second derivative spectra were selected for evaluation, because working wavelength determination was more precise and spectral overlap was less than in the ordinary and first derivative spectra. Three wavelengths at which the complexes exhibit extremum ²D values for Co(II), Ni(II) and Fe(II) were selected as analytical wavelengths, i.e., 640, 600 and 740 nm, respectively. Calibration curves drawn with zero-to-peak values at mentioned wavelengths were linear between 80 and 2000 ng ml⁻¹ for each metal ion. Concentrations of Co(II) and Ni(II) were calculated from the total ²D values and the sum of the linear equations for these three cations at 640 and 600 nm, after Fe(II) assay by making use of the ²D value at 740 nm. Limits of detection (LOD) for Co(II), Ni(II) and Fe(II) were 2.7, 13.9 and 3.0 ng ml⁻¹, respectively. The method has been applied to tool steel and heater resistance wire samples successfully.     

Fe/Co alloys for the catalytic chemical vapor deposition synthesis of single- and double-walled carbon nanotubes (CNTs). 1. The CNT-Fe/Co-MgO system

Mg(0.90)Fe(x)Co(y)O (x + y = 0.1) solid solutions were synthesized by the ureic combustion route. Upon reduction at 1000 degrees C in H2-CH4 of these powders, Fe/Co alloy nanoparticles are formed, which are involved in the formation of carbon nanotubes, which are mostly single and double walled, with an average diameter close to 2.5 nm. Characterizations of the materials are performed using 57Fe M?ssbauer spectroscopy and electron microscopy, and a well-established macroscopic method, based on specific-surface-area measurements, was applied to quantify the carbon quality and the nanotubes quantity. A detailed investigation of the Fe/Co alloys' formation and composition is reported. An increasing fraction of Co2+ ions hinders the dissolution of iron in the MgO lattice and favors the formation of MgFe2O4-like particles in the oxide powders. Upon reduction, these particles form alpha-Fe/Co particles with a size and composition (close to Fe(0.50)Co(0.50)) adequate for the increased production of carbon nanotubes. However, larger particles are also produced resulting in the formation of undesirable carbon species. The highest CNT quantity and carbon quality are eventually obtained upon reduction of the iron-free Mg(0.90)Co(0.10)O solid solution, in the absence of clusters of metal ions in the starting material.     

Fe3O4 and gamma-Fe2O3 nanoparticles for the adsorption of Co2+ from aqueous solution

The adsorption of Co2+ ions from nitrate solutions using iron oxide nanoparticles of magnetite (Fe3O4) and maghemite (gamma-Fe2O3) has been studied. The adsorption of Co2+ ions on the surface of the particles was investigated under different conditions of oxide content, contact time, solution pH, and initial Co2+ ion concentration. It has been found that the equilibrium can be attained in less than 5 min. The maximum loading capacity of Fe3O4 and gamma-Fe2O3 nanoparticles is 5.8 x 10(-5) and 3.7 x 10(-5) mol m(-2), respectively, which are much higher than the previously studied, iron oxides and conventional ion exchange resins. Co2+ ions were also recovered by dilute nitric acid from the loaded gamma-Fe2O3 and Fe3O4 with an efficiency of 86 and 30%, respectively. That has been explained by the different mechanisms by including both the surface and structural loadings of Co2+ ions. The surface adsorption of Co2+ on Fe3O4 and gamma-Fe2O3 nanoparticles has been found to have the same mechanism of ion exchange reaction between Co2+ in the solution and proton bonded on the particle surface. The conditional equilibrium constants of surface adsorption of Co2+ on Fe3O4 and gamma-Fe2O3 nanoparticles have been determined to be log K=-3.3+/-0.3 and -3.1+/-0.2, respectively. The structural loading of Co2+ ions into Fe3O4 lattice has been found to be the ion exchange reaction between Co2+ and Fe2+ while that into gamma-Fe2O3 lattice to fill its vacancy. The effect of temperature on the adsorption of Co2+ was also investigated, and the value of enthalpy change was determined to be 19 kJ mol(-1).     

Reversed-phase ion-pair high performance liquid chromatographic determination of Co(III)-, Ni(II)-, V(V)- and Fe(III)-2-(2-benzothiazolylazo)-5-(3-sulforpropyl)aminophenol chelates

The separation and determination of Co(III), Ni(II), V(V) and Fe(III) chelates with 2-(2-benzothiazolylazo)-5-(3-sulfopropyl)aminophenol (BTASPAP) by reversed-phase ion-pair HPLC was investigated. In the presence of the oxidant potassium iodate, BTASPAP reacts with Co(III), Ni(II), V(V) and Fe(III) to form stable, negatively charged, water-soluble chelates. The chelates were separated on a C(18) siloxane bonded phase and eluted within 7 min with acetonitrile-acetate-water (36:1:63 v/v) containing 0.2 mol 1(-1) acetic acid-sodium acetate buffer (pH 3.0) and 1.0 mmol 1(-1) tetrabutylammonium bromide. The detection limits of Co(III), Ni(II), V(V) and Fe(III) at 565 nm are 0.3, 0.8, 0.3 and 1.0 ng (signal-to-noise ratio = 2), respectively. The method was applied to the determination of Co, Ni, V and Fe in four samples of standard alloys.     

Metal(II) Formates (M = Fe,Co, Ni,and Cu) Stabilized by Tetramethylethylenediamine (tmeda): Convenient Molecular Precursors for the Synthesis of Supported Nanoparticles

γ‐Alumina supported 3d transition‐metal nanoparticles are commonly used catalysts for several industrial reactions, such as Fischer‐Tropsch, reforming, methanation, and hydrogenation reactions. However, the activity of such catalyst is often limited by the low metal dispersion and a high content of irreducible metal, inherent to the conventional preparation methods in aqueous phase. In this context, we have recently shown that [{Ni(μ²‐OCHO)(OCHO)(tmeda)}₂(μ²‐OH₂)] (tmeda=tetramethylethylenediamine) is a suitable molecular precursor for the formation of 1–2 nm large nanoparticles onto alumina. Here, we explore the synthesis of the corresponding Fe, Co, and Cu molecular precursors, namely [{Fe(μ²‐OCHO)(OCHO)(tmeda)}₄], [{Co(μ²‐OCHO)(OCHO)(tmeda)}₂(μ²‐OH₂ )], [Cu(κ²‐OCHO)₂(tmeda)], which are, like the Ni precursor, soluble in a range of solvents, rendering them convenient metal precursors for the preparation of supported metallic nanoparticles on γ‐alumina. Using a specific adsorption of the molecular precursor on γ‐alumina in a suitable organic solvent, treatment under H₂ provides small and narrowly distributed Fe (2.5±0.9 nm), Co (3.0±1.2 nm), Ni (1.7±0.5 nm), and Cu (2.1±1.5 nm) nanoparticles. XAS shows that the proportion of MAl₂O₄ (M = Co, Ni, Cu) is small, thus illustrating the advantage of using these tailor‐made molecular precursors.     

Effects of a 10 T external magnetic field on the thermal decomposition of Fe, Ni, and Co acetyl acetonates

The current investigation is centered on the thermal decomposition (700 degrees C) of acetyl acetonates of Ni, Co, and Fe in a closed reactor that was conducted by employing an external magnetic field (MF) of 10T. Interestingly, reactions of Co and Ni acetyl acetonates under a 10T MF produce Co and Ni nanoparticles (NPs) coated with carbon, while Fe acetyl acetonate produces Fe3O4 uncoated with carbon. Additionally, it is observed that all the as-formed magnetic particles tend to align in one dimension along applied MF; thus, this process can be used to fabricate large arrays of magnetic nanoparticles. The effect of an applied MF to synthesize morphologically and compositionally different products from corresponding precursors with their mesoscopic organization is the key theme of the present paper, explained with a plausible mechanism.     

Structure and Electrochemical Properties of Carbon Nanotubes Synthesized with Catalysts Obtained by Decomposition of Co,Ni, and Fe Polyoxomolybdates Supported by MgO

Carbon nanotubes (CNTs) were synthesized by thermal decomposition of methane at 900 °C using Co–Mo/MgO, Fe–Mo/MgO, and Ni–Mo/MgO catalysts. To obtain metallic nanoparticles, polyoxomolybdate clusters of Co, Ni, and Fe deposited on MgO were thermally decomposed at 700 °С, and the obtained oxides were heated in a carbon-containing atmosphere. The method of transmission electron microscopy (TEM) testified formation of one to ten walled CNTs with the average outer diameter depending on the catalyst used. Raman spectroscopy data confirmed the presence of single-walled CNTs in the samples obtained with Co–Mo/MgO and Fe–Mo/MgO catalysts. The electrochemical properties demonstrated by the obtained materials in supercapacitors are shown to be functions of their structural and compositional features.     

CO氧化反应中H2O对MOx和Au/MOx催化性能的影响

过渡金属氧化物［1,2］及负载型贵金属催化剂［3～13］是催化氧化消除CO的有效催化剂,一直是研究的热点. 虽然对MOx和Au/MOx上CO的氧化性能研究得较多,但大多是在无水条件下进行的;涉及催化剂抗水性能的报道较少［3,9,10］,且仅限于对催化剂活性的研究. Haruta等［3］对Au/Fe2O3,Au/Co3O4和Au/TiO 2等体系开展了一些工作, 认为水对CO氧化活性有促进作用. 本文重点考察了水对MOx(M=Al,Ca,Co,Cr,Cu,Fe,La,Mn,Ni和Zn)催化剂上CO氧化活性的影响,以及水对Au/MOx 催化剂活性及稳定性的影响.     

Synthetic control over magnetic moment and exchange bias in all-oxide materials encapsulated within a spherical protein cage

This work focuses on the synthetic control of magnetic properties of mixed oxide magnetic nanoparticles of the general formula Fe(3-x)Co(x)O(4) (x < or = 0.33) in the protein cage ferritin. In this biomimetic approach, variations in the chemical synthesis result in the formation of single-phase Fe(3-x)Co(x)O(4) alloys or intimately mixed binary phase Fe/Co oxides, modifying the chemical structure and magnetic behavior of these particles, as characterized by static and dynamic magnetization measurements and X-ray absorption spectroscopy.     

Modification in structural,optical, morphological,and electrical properties of zinc oxide (ZnO) nanoparticles (NPs) by metal (Ni,Co) dopants for electronic device applications

In the present work, Zinc Oxide (ZnO) nanoparticles (NPs) were synthesized by the chemical co-precipitation method using Zinc Chloride as the initial chemical, while Nickel and Cobalt chloride as dopants. Phase identification of metal (Ni, Co) doped Zinc Oxide nanoparticles (NPs) was observed using x-ray diffraction (XRD). The small lattice distortion or phase changes appeared due to shifting of diffraction angles peaks towards larger angle in ZnO are corresponded to metal (Ni, Co) dopant. The average crystallite size appears to decrement in NP size from 7.67 nm to 6.52 nm and 5.35 nm to 5.17 nm with increasing 5 % to 80 % of metal (Ni, Co) dopant respectively. The optical characteristics, including the absorption spectra of the prepared sample were observed through UV–Vis spectroscopy, Meanwhile SEM confirmed the observation of composition change in specimen with metal (Ni, Co) dopant concentration. The bandgap value was also found decrement 5.23 eV to 5.05 eV with increment of metal (Ni, Co) dopant concentration. The functional groups were measured by Fourier transformation infrared spectroscopy (FTIR). FTIR peaks found the metal (Ni, Co) doped ZnO with the vibration mode of (Zn²⁺ –O^2?) ions due to the increment of dopant concentrations. Furthermore, electrical results show the ohmic behavior of prepared samples. These findings indicate the possibility of tuning optical, structural and electrical properties of metal (Ni, Co) doped ZnO with various dopant concentrations of Nickel and will have great potential to find application in optoelectronic devices.     

活性炭负载Pt-Ni双金属催化剂上甘油水溶液原位加氢反应性能

采用KBH4液相还原法制备了系列活性炭(AC)负载的Pt-M(M=Fe,Ni,Co,Zn,Cu)双金属催化剂,考察了该系列催化剂对甘油水溶液原位加氢制备1,2-丙二醇反应的催化性能.结果表明,当Pt负载量(质量分数)为2.0%,Pt/Ni质量比为1∶1时,在220℃和1.0 MPa氮气压力下反应8 h,2%Pt-2%Ni/AC催化剂上甘油转化率和1,2-丙二醇选择性分别达到98.7%和60.5%;且在5次重复使用过程中,催化剂保持较高的稳定性.采用氮气物理吸附-脱附实验、X射线衍射(XRD)、透射电子显微镜(TEM)、选区电子衍射(SAED)及X射线光电子能谱(XPS)等对催化剂的结构和形貌进行了表征.结果表明,粒径约为2 nm的纳米颗粒在活性炭载体上均匀分散,纳米粒子中金属多以还原态形式存在,Ni原子进入Pt晶格中形成的Pt-Ni物种使Pt与Ni之间表现出强相互作用力.通过比较Pt/AC,Ni/AC与Pt-Ni/AC双金属催化剂的催化性能,推断Pt能够促进甘油水溶液重整而Ni有利于氢解反应,Pt-Ni金属间协同作用是Pt-Ni/AC催化剂对甘油原位加氢反应具有优良催化性能的重要原因.     

Formation of CO(x)-free H2 and cup-stacked carbon nanotubes over nano-Ni dispersed single wall carbon nanohorns

Transitional metals (M) were dispersed on single-wall carbon nanohorns (M/SWCNHs, M = Fe, Co, Ni, Cu) by simple thermal treatment of the deposited metal nitrate without H(2) reduction. Nanometallic Ni particles on SWCNH were evidenced by high-resolution transmission electron microscopic observation and X-ray photoelectron spectroscopy. The nano-Ni dispersed on SWCNH showed the highest CH(4) decomposition activity; the activity of used transitional metals decreases in the order Ni ? Co > Fe ? Cu. On the other hand, the reaction rate over Ni/SWCNH was much larger than that over Ni/Al(2)O(3), and the former provided CO(x)-free H(2) and cup-stacked carbon nanotubes, while Ni/Al(2)O(3) produced CO(x) in addition to H(2). SWCNH was superior to Al(2)O(3) as the catalyst support of Ni for the CH(4) decomposition reaction.