High dispersion and electrochemical capacitive performance of NiO on benzenesulfonic functionalized carbon nanotubes

This work describes an effective method to synthesize structurally uniform composite of nickel oxide/benzenesulfonic functionalized multiwalled carbon nanotubes composite (NiO/f-MWCNTs) using benzenesulfonic MWCNTs as the substrate. Benzenesulfonic group here is bifunctional both for solubilizing MWCNTs into aqueous solution and for tethering Ni²⁺ precursor onto MWCNTs surfaces to facilitate the follow-up chemical deposition of NiO by supplying surface binding and anchoring groups. The composite has a uniform surface dispersion and large coverage of NiO onto f-MWCNTs, which is characterized by X-ray diffraction, transmission electron microscopy, scanning electron microscope, cyclic voltammetry and galvanostatic charge/discharge measurements. The NiO/f-MWCNTs composite improved the utilization of electrochemical capacitive materials and delivered capacity of 384 F/g at the constant current of 0.20 A/g due to f-MWCNTs as substrate.     

Hybrid nickel oxide-carbon fiber composites obtained in the presence of surfactants

The composite material nickel hydroxide (oxide)/carbon fiber has been obtained by hydroxide deposition on the surface of the activated carbon fiber (ACF) via urea hydrolysis in the presence of a surfactant. The organomineral composite NiO/CHIT/carbon fiber has been obtained by electrochemical deposition of nickel hydroxide on the ACF surface in combination with chitosan as well as by cathode deposition on a carbon fiber electrode preliminarily modified by chitosan. The surface of the obtained hybrid materials has been investigated by means of the methods of X-ray photoelectron spectroscopy (XPS), atomic force and scanning electron spectroscopy (AFM and SEM), and cyclic voltamperometry. The composition and properties of the obtained composites have been discussed.     

Nucleation of Solid-State Reactions between Nickel Oxide and Aluminium Oxide

The initial stages of the solid-state reaction between high-quality thin films of nickel oxide and single-crystal aluminum oxide have been investigated. Thin films were grown on specially cleaned and annealed basal-plane (0001) alumina substrates by pulsed-laser deposition. The thin-film reaction couples were then heat-treated in air at 1080° and 1100°C for different times in order to induce the formation of the nickel aluminate spinel. The reaction couples were characterized in cross section by high-resolution scanning electron microscopy and conventional transmission electron microscopy. The films of nickel oxide consisted of two twin variants with a common {111} plane, parallel to the basal plane of alumina, but rotated by 60° or 180° about the 〈111〉 direction normal to that plane. The spinel nucleated where the twin boundaries in the nickel oxide film met the alumina substrate and contained the same twin variants as the original NiO film.     

髋关节整体替代陶瓷材料

许多材料在医学领域应用广泛,例如,整体替换硬组织或软组织的元件(如骨盆、骨头、关节、植牙等)、修补、诊断或矫正仪器(如起搏器、心脏阀等)。这些材料不仅要有好的力学性能,还要保持长期稳定,不能与人体相排斥。由于陶瓷材料在生理环境中具有强度高、生物相容性强和稳定性好的优点,人们研究用陶瓷材料替换骨骼。从20 世纪70 年代起,欧洲人用陶瓷组件置换整个髋关节。这些组件主要由氧化铝和氧化锆单体制成。然而,在有水环境中,氧化锆会发生低温降解。目前人们的研究重点在于提高陶瓷组件的强度和耐磨性,同时缩小其尺寸并延长其使用寿命。研究中使用的材料是氧化锆增韧的氧化铝复合陶瓷和其它氧化铝复合陶瓷,不再是单体陶瓷。另外,还可以使用氧化铝和氧化锆功能梯度复合材料。该梯度材料可以利用电泳沉积法(EPD)制得,其表面为纯氧化铝,中心部分为均匀的氧化铝、氧化锆复合材料,中间过渡部分是呈连续梯度渐变的氧化铝、氧化锆复合材料,烧成后会产生剩余热应力。设计这样的梯度结构是为了使复合材料具有最大表面压应力和最小内部张应力,与纯氧化铝组件相比,提高了强度和耐磨性。     

Nickel catalysts supported on carbon nanofibers: structure and activity in methane decomposition

Structures of Ni catalysts supported on filamentous carbon (CFC) produced by methane decomposition over coprecipitated Ni and Ni-Cu/alumina catalysts were studied by EXAFS and TEM. Thermal pre-treatment in N₂ at 350°C of samples impregnated by nickel nitrate precursor was found to produce either NiO or nickel carbide, Ni₃C, phase. This was explained by different reducing properties of the carbon nanofibers which depend on the surface structure. High stability of the Ni/C catalysts in methane decomposition reaction at 550°C was found with those prepared from only nickel chloride precursor, due to the formation of large (30-70 nm) Ni particles further leading to new carbon filaments growth. Data implies a common mechanism of the filamentous carbon deposition in all Ni-based catalysts, independent of the support (silica, alumina, carbon) being used. However, accumulation of filamentous carbon is strongly influenced by morphology and texture of the support. This revised version was published online in July 2006 with corrections to the Cover Date.     

Activity and stability of alumina zeolite nickel catalysts

The catalytic properties of nickel catalysts (50 wt.% of alumina and 50 wt.% of Ni,H-ZSM-5) were investigated and related to the amount of NiO (0–8 wt.%) and the method of nickel incorporation (8 wt.% NiO). Consideration was also given to the method by which zeolite and alumina were combined. The cracking properties of the catalysts increased when the amount of NiO was raised up to 4 wt.%. To decrease the content of aromatic hydrocarbons in the products it is necessary to raise the amount of NiO to a higher level than 4 wt.%. The catalyst prepared by peptisation of the mixture of zeolite and aluminium hydrogel (with ageing process) displayed reduced activity and stability because of the low susceptibility of NiO to reduction.     

Graded Casting of Materials with Continuous Gradients

A process is introduced for producing continuously graded materials by slip casting with a continuous flow of slip of changing composition. The approach has been tested using alumina and zirconia slips to produce alumina/zirconia composites with a graded composition. Observation of the microstructure has shown that the phases are relatively well dispersed. Compositional analysis revealed a relatively smooth transition in composition through the thickness of sintered bodies. Results have also indicated that for flow rates up to ∼ 60 cm/min, the highest linear flow rate tested, the casting rate of alumina slips containing 38.6 vol% solids was not affected.     

Kinetics of Thin-Film Reactions of Nickel Oxide with Alumina: II, {1100} and {1102} Reaction Couples

The kinetics of the earliest stages of solid-state reactions between epitactic thin films of nickel oxide (NiO) and {11# 00}- and {11# 02}-oriented single crystals of alumina (Al₂ O₃) have been studied. The starting reaction geometry consisted of a nickel aluminate (NiAl₂ O₄) buffer layer 20 nm thick and a NiO overlayer that was 400 nm thick, both of which were grown via pulsed-laser deposition and were epitactic with the substrate. When heated, the reaction lay-ers thickened mainly as the square root of time (i.e., para-bolic kinetics) increased, which was indicative of reaction-controlled kinetics via diffusion through the product layer. The activation energy for the reaction was 461 kJ/mol for {11# 00} and 464 kJ/mol for the {11# 02}; both values are consistent with measurements made previously using thin-film and bulk reaction geometries. A smaller linear component to the kinetics has also been identified. The results of microstructural characterization and "marker" experiments will also be discussed.     

Fibrous Monolithic Ceramics: IV, Mechanical Properties and Oxidation Behavior of the Alumina/Nickel Systein

Fibrous monolithic ceramics were fabricated in the alumina/nickel system. The microstructure consists of high-aspect-ratio polycrystalline cells of alumina separated by thin cell boundaries of nickel. The nickel content in the material is 3 to 8 vol%. The fibrous monolith with uniaxially aligned cells fails noncatastrophically in flexure. Bridging ligaments of nickel, crack deflection along cell boundaries, and crack branching in the axial direction are observed in flexure bars and notched beams. Strength values range from 246 to 375 MPa. Indentations cause controlled damage on the surface but do not introduce strength-degrading flaws. The alumina/nickel fibrous monoliths also show potential for use at high temperatures in oxidizing environments. Noncatastrophic fracture behavior is observed at room temperature after 10 h at 1200°C in air. The Ni cell boundary network is oxidized to a depth of 50 to 100 μm by this heat treatment. The NiO oxidation product in the cell boundaries reacts partly with alumina from the cells to form NiAI₂O₄, which would provide better protection.     

Thermal residual stress gradients in an alumina–zirconia composite obtained by electrophoretic deposition

In order to understand the mechanical behavior of layered composites with compositional gradient, it is necessary to determine their state of residual stresses. Compositionally graded materials can offer the advantage of eliminating abrupt changes in composition between layers having different thermal expansion coefficient. The existence of a compositional gradient can reduce discontinuities in thermal residual stresses, something beneficial from the point of view of the mechanical properties.We present here a study of the microstructure and state of residual stressses in a layered material made of homogeneous layers of alumina and alumina–zirconia separated by thin (less than 300 μm) intermediate compositionally graded layers. The composite was obtained by controlled deposition of powders from solution using an electrophoretic deposition (EPD) method. The phase distribution and compositional gradient in the sintered composite were investigated using scanning electron microscopy (SEM). Thermal residual stresses generated during cooling after sintering were measured by using fluorescence ruby luminiscence piezo-spectroscopy and the profile of hydrostatic stress on alumina was determined at steps of about 300 μm along the direction of the compositional gradient, and at steps of about 30 μm in the compositionally graded layers. The obtained profile of hydrostatic stresses on alumina grains follows closely the profile of compositional changes along the layered composite. The presence of thin intermediate graded layers reduce significantly changes in stress in the layered composite.     

The effect of water on the reduction of nickel/alumina catalysts

The crucial role of water in the reduction of calcined nickel/alumina catalysts is demonstrated. A fraction of nickel oxide in the catalysts is reduced as NiO powder in the absence of water vapour, and as a nickel aluminate in the presence of water. A much higher dispersion of nickel is attained when the reduction is carried out at low concentration of water vapour.     

低热固相法制备纳米氧化镍

比较了四水合乙酸镍与三种有机酸(草酸、酒石酸和乙二胺四乙酸)在室温条件下发生固相化学反应的速度,选取反应速度最快的草酸(和四水合乙酸镍)为原料,用室温固相化学反应合成出前驱配合物,进而热分解得到纳米氧化镍粉末,产物用X射线粉末衍射和透射电镜进行了表征。结果表明,产物纳米氧化镍为球形立方晶系结构,平均粒径为15nm,并初步探讨了分解温度对产物粒径大小、分散性的影响及低热固相反应制备纳米粒子的机理。     

Studies on Sodium Lignosulfonate Depolymerization Over Al2O3 Supported Catalysts Loaded with Metals and Metal Oxides in a Continuous Flow Reactor

The aim of this work was to study the how various heterogeneous catalysts perform upon lignosulfonate decomposition reactions. The main target of the study was to obtain extractable phenolic compounds as potential renewable chemicals for the production of fuel components and chemicals. The nature of the heterogeneous catalyst was found to have a great impact on the obtained product yields and the composition of the product mixture. Initially, a nickel–tungsten on alumina (NiW/Al₂O₃) reference catalyst was applied upon screening the influence of catalyst particle size and various reaction parameters. Significantly increasing product yields with decreasing catalyst particle size indicated that the lignosulfonate transformation takes place on the external catalyst surface due to large macromolecular structure of the feedstock. The contact time (space time velocity) and catalyst particle size were the most important factors influencing the selectivity profiles towards various products as well as the yields observed. The highest conversion to phenolics was obtained over in-house-prepared NiO/Al₂O₃ and NiMo/Al₂O₃ catalysts with various NiO and MoO₃ loadings.     

Deactivation studies over NiO/γ-Al2O3 catalysts for partial oxidation of methane to syngas

Two types of NiO/γ-Al₂O₃ catalysts prepared by the impregnation and the sol–gel method were used for the partial oxidation of methane to syngas at 850°C (GHSV1.8×10⁵ lkg⁻¹ h⁻¹). The effects of the carbon deposition, the loss and sintering of nickel and the phase transformation of γ-Al₂O₃ support on the catalytic performance during 80 h POM reaction were investigated with a series of characterization such as XRD, BET, AAS, TG, and XPS. The results indicated that the carbon deposition and the loss and sintering of nickel could not cause the serious decrease of catalytic performance over NiO/γ-Al₂O₃ catalyst during the short-time reaction. However, the slow process of the support γ-Al₂O₃ phase transforming into -Al₂O₃ could slowly decrease the performance of NiO/γ-Al₂O₃ catalysts. Aimed at the reasons of the deactivation, an improved catalyst was obtained by the complexing agent-assisted sol–gel method.     

负载型Ni催化剂上对硝基酚加氢合成对氨基酚的研究

研究了以硅藻土、锐钛型TiO2、Al2O3和高岭土为载体制备的负载型Ni催化剂催化对硝基酚加氢制备对氨基酚的活性。采用XRD与TPR技术表征了催化剂的结构与还原性能。负载型催化剂具有单一的对氨基酚选择性。NiO与载体硅藻土和锐钛型TiO2有弱的相互作用,制备的催化剂还原后有较高的催化活性。Al2O3和高岭土与NiO有较强的相互作用,抑制了还原后金属Ni的催化加氢活性。     

Developing high-transmittance heterojunction diodes based on NiO/TZO bilayer thin films

In this study, radio frequency magnetron sputtering was used to deposit nickel oxide thin films (NiO, deposition power of 100 W) and titanium-doped zinc oxide thin films (TZO, varying deposition powers) on glass substrates to form p(NiO)-n(TZO) heterojunction diodes with high transmittance. The structural, optical, and electrical properties of the TZO and NiO thin films and NiO/TZO heterojunction devices were investigated with scanning electron microscopy, X-ray diffraction (XRD) patterns, UV-visible spectroscopy, Hall effect analysis, and current-voltage (I-V) analysis. XRD analysis showed that only the (111) diffraction peak of NiO and the (002) and (004) diffraction peaks of TZO were observable in the NiO/TZO heterojunction devices, indicating that the TZO thin films showed a good c-axis orientation perpendicular to the glass substrates. When the sputtering deposition power for the TZO thin films was 100, 125, and 150 W, the I-V characteristics confirmed that a p-n junction characteristic was successfully formed in the NiO/TZO heterojunction devices. We show that the NiO/TZO heterojunction diode was dominated by the space-charge limited current theory.     

Low temperature atomic layer deposition of nickel sulfide and nickel oxide thin films using Ni(dmamb)2 as Ni precursor

Nickel(II) 1-dimethylamino-2-methyl-2-butoxide (Ni(dmamb)₂) with water and hydrogen sulfide as oxygen and sulfur sources was employed in atomic layer deposition (ALD) of nickel oxide (NiO) and nickel sulfide (NiS) thin films. Both NiO and NiS thin films demonstrate temperature-independent growth rates per cycle of 0.128?nm/cycle and 0.0765?nm/cycle, at 130–150?°C and 80–160?°C, respectively. Comparison of two nickel-based thin film materials demonstrates dissimilar deposition features depending on the reactivity of the Ni precursor, i.e., Ni(dmamb)₂ with anion sources provided by the water and hydrogen sulfide reactants. Difference in reactivity observed for NiO and NiS ALD processes is further investigated by density functional theory (DFT) simulations of surface reactions, which indicated that H₂S demonstrate higher reactivity with surface-adsorbed Ni precursor than H₂O. The material properties of ALD NiO and NiS thin films including stoichiometry, crystallinity, band structure, and electronic properties were analyzed by multiple experimental techniques, showing potential of ALD NiS as electrode or catalyst for energy-oriented devices.     

Electrodeposition of nickel oxide nanoparticles on glassy carbon surfaces: application to the direct electron transfer of tyrosinase

This work describes the performance of a tyrosinase/nickel oxide nanoparticles/glassy carbon (Tyr/NiO NPs/GC) electrode. This electrode was prepared by first applying a NiO NPs electrochemical deposition onto the GC electrode surface and then tyrosinase immobilization was applied to the surface of electrodeposited NiO NPs. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) procedures demonstrated the existence of different NiO NP geometrical structures. These geometrical structures could lead to better immobilization of proteins on their surfaces. The copper containing enzyme tyrosinase successfully achieved electrical contact with the electrode because of the unique structural alignment of tyrosinase enzyme on the nanometer-scale nickel oxide surfaces. This method could be suitable for application to nanofabricated devices facilitating better performance. It was concluded that tyrosinase can be effectively applied to nanometer-scale nickel oxide surfaces.     

纳米氧化镍制备及表征

以六水硝酸镍和氨水为原料,采用配位均匀沉淀法制备了纳米氧化镍。探讨了制备条件对氧化镍前驱体产率和纳米氧化镍平均粒径的影响,得出最佳工艺条件：镍离子浓度为0.8 mol/L,反应物配比［n（氨水）/n（硝酸镍）］为3∶1,沉淀反应温度为80 ℃,反应时间为90 min,焙烧温度为400 ℃,焙烧时间为1 h。同时,利用X射线衍射（XRD）和透射电镜（TEM）等分析方法对产品组成和形貌进行了表征,结果显示,实验制得的氧化镍纳米晶属标准面心立方晶系结构,晶粒呈球形,平均粒径约为12 nm。     

Electrochemical preparation and characterization of Ni/SiC compositionally graded multilayered coatings

In our study, Ni/SiC functionally graded coatings have been obtained by electrochemical deposition of silicon carbide microparticles (mean diameter 2 μm) from nickel Watts baths with different concentrations of SiC particles in solution. The SiC particles were characterized by electroacustics technique in order to determine zeta potential and particle size. Moreover, the effect of the concentration of SiC particles in solution on the amount of SiC deposited in the nickel layer was investigated. Further experiments showed that the degree of particle incorporation provoked changes in the texture of the nickel matrix. The characterization of the coatings proved that the Ni/SiC graded composite coatings were bright and compact, presented good adhesion and improved the hardness and wear resistance of pure nickel electrodeposits.