介孔氧化镍的合成、表征和在电化学电容器中的应用

以十二烷基硫酸钠为模板剂, 采用尿素为沉淀剂, 用均匀沉淀法, 适当控制尿素的水解速度, 制备具有介孔结构的氢氧化镍胶体, 在不同温度下焙烧处理得到孔分布集中的氧化镍介孔分子筛. 结果表明, 在523 K下焙烧得到的氧化镍BET比表面达到477.7 m²•g^－1. 结构表征还显示, 介孔氧化镍的孔壁为多晶结构, 其孔结构形成机理应为准反胶束模板机理. 循环伏安法表明用NiO介孔分子筛制备的电极有很好的电容性能. 与浸渍法和阴极沉淀法制得的NiO相比, 这种介孔结构的NiO能够大量用来制作电化学电容器电极, 并且保持较高的比电容量和良好的电容性能.     

Structural analysis of water adsorbed in silica gel

The melting point, T _f of water in a pore decreases as the surface area to pore volume ratio of the pore decreases. Analysis of water absorbed in the pores of silica gels using differential scanning calorimetry (DSC) and dielectric relaxation spectroscopy (DRS) shows that the thickness of the bound, non-freezing water layer adjacent to the pore surface increases as its temperature increases, but that it is independent of the surface silanol concentration, [Si_sOH]. In contrast, the thickness decreases as the cylindrical pore radius r _H decreases. Thus, the increase in the bound water thickness from 0.45 nm for gels with r _H =1.2 nm to 1.2 nm for gels with r _H =7.5 nm is due to the increase from –53°C to –7°C of the temperature (e.g., the melting point T _f ) at which the bound water thickness was measured, and not due to the increase in t _H or the decrease in [Si_sOH]. The T _f of bulk water measured in a DSC was –0.3°C. The boiling point T _v of bulk water measured in a DSC was 81.3°C. T _v increased to 94°C in 7.5 nm pores and to 109°C K in 1.2 nm pores.     

Proton-Conducting Phosphosilicate Films Prepared Using Template for Pore Structure

Ordered mesoporous glass films were prepared using an interfacial silica-surfactant self-assembly technique and their porous and proton conducting properties were investigated. Gel films were deposited on substrates by dip-coating of the mixed-solution of hydrolyzed-alkoxide and non-ionic surfactant C₁₆H₃₃(OCH₂CH₂)₁₀OH. Cubic-orderd mesostructure was formed by dipping the solution, the ordered structure of which decayed gradually with increasing the aging period of the solution and disappeared after aging of 120 h. The resulting ordered mesoporous films obtained following heating at 400°C exhibited surface area and average pore diameters of 1030 m²/g and 2.5 nm, respectively. The obtained glass films exhibited proton conductivity of 10^{– 3} S/cm at 80°C in 70% RH.     

Modification of Non-Hydrolytic Sol-Gel Derived Alumina by Solvent Treatments

The effect of wetting non-hydrolytic derived alumina xerogels with water and organic solvents in the 20–70°C range on the alumina's properties was investigated. Wetting with organic solvents does not affect the alumina. However, contact with water was found to change the sharp crystallization at 800°C to a continuous crystallization starting at 450°C. Water treatment for a day at room temperature (RT) followed by second calcination decreased the surface area by 10%. This decrease in surface area is less pronounced with increasing wetting periods. On the other hand water treatment at 50–70°C followed by a second calcination resulted in a surface area increase of up to 15%. Upon water treatment the total pore volume has decreased from 0.65 (cm³/gr) to 0.48 (cm³/gr) and the average pore size decreased from 6.8 nm to 4.1 nm. The Cl content was found to be uneffected by the water treatment, remaining at 2.5% wt. Wetting with water at elevated temperature (70°C) accelerated the morphological changes, eliminating the crystallization peak at 800°C in one hour. A dissolution-reprecipitation mechanism is suggested to explain the results. In addition, Mass-Spectroscopy of the effluent gas during heat treatment revealed the emission of CO₂ and water upon phase transition into -Al₂O₃, at 1150–1300°C.     

The Inherent Electrochemistry of Nickel/Nickel‐Oxide Nanoparticles

The direct detection of nanoparticles is at the forefront of research owing to their environmental and toxicological applications. Herein, we studied the inherent electrochemistry of Ni and NiO nanoparticles and proposed a simple and direct electrochemical method for the determination of the concentrations of both nickel (Ni) and nickel oxide (NiO) nanoparticles in alkaline solution. A highly sensitive voltammetry technique was used to measure the oxidative signal of Ni(OH)₂ that formed spontaneously on the surface of Ni and NiO nanoparticles in alkaline media. Detection limits of 220 μg mL^?1 for Ni and 13 μg mL^?1 for NiO nanoparticles were obtained. Ni and NiO nanoparticles are used as electrode modifiers or as electrochemical signal labels in various biosensing applications. Therefore, methods to rapidly quantify the amount of Ni and NiO nanoparticles are of widespread potential use.     

Sol-Gel Derived Nanocomposites and Nanoporous Oxide Powders and Related Coatings for the Reversible Chemisorption of Hydrogen Sulfide

Two types of nanocomposites and nanoporous powders and related coatings were prepared by the sol-gel route. These silica-based materials contain dispersed reactive oxides, ZnO and ZnCr₂O₄, respectively. Experiments evidenced their ability of reversible chemisorption of H₂S as ZnS. Their attractive porous characteristics (small pore size 2–2.5 nm, high specific surface area 900–1100 m²· g^–1, high porosity 50–60%) are not significantly modified during the successive treatments of H₂S chemisorption and oxide regeneration. These preliminary results encourage to pursue this study which aims at the preparation of nanofilters for the desulfurization of gas mixtures.     

Ionic conduction of a high-temperature modification of Lu<Subscript>2</Subscript>Ti<Subscript>2</Subscript>O<Subscript>7</Subscript>

A nanoceramic product of the composition Lu₂Ti₂O₇ is synthesized by a coprecipitation method with a subsequent sublimation drying and an annealing at 650–1650°C. The conduction of Lu₂Ti₂O₇ synthesized at 1650°C is ionic (10^–3 S cm^–1 at 800°C). Thus, a new material with a high ionic conduction has been discovered. The ordering in Lu₂Ti₂O₇ is studied by methods of RFA, RSA, IK spectroscopy, electron microscopy, and impedance spectroscopy. The existence of a low-temperature phase transition fluorite-pyrochlore at 800°C and a high-temperature conversion order-disorder at 1650°C are established.Translated from Elektrokhimiya, Vol. 41, No. 3, 2005, pp. 298–303.Original Russian Text Copyright © 2005 by Shlyakhtina, Ukshe, Shcherbakova.     

Diffusion of deuterium into silicon single crystals: An investigation with SIMS

Summary Silicon single crystals were annealed at various temperatures between 25 and 350° C in a deuterium discharge and were subsequently analyzed with Secondary Ion Mass Spectrometry (SIMS). Beginning at the surface, the deuterium signal decays exponentially to the interior (decay length 30 nm under bombardment with 9-keV O ₂ ⁺ J ions). The influence of the bombarding energy on the decay length and the disappearance of the deuterium signal after a treatment with HF show that the deuterium profile is due to an ion beam-induced effect. It is concluded from investigations of boron-doped crystals (both implanted and diffused B) that a surface barrier exists for the indiffusion of deuterium, probably the native oxide layer. The permeation rate of deuterium through this barrier is 2×10¹¹ atoms/cm²s at 350° C and decreases strongly with decreasing temperature.

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Diffusion von Deuterium in Silicium-Einkristalle: eine Untersuchung mit SIMS

Zusammenfassung Silicium-Einkristalle wurden bei verschiedenen Temperaturen zwischen 25° C und 350° C in einer Deuteriumentladung getempert und anschließend mittels der Sekundärionen-Massenspektrometrie (SIMS) untersucht. Ausgehend von der Oberfläche nimmt das Deuteriumsignal exponentiell mit der Tiefe ab (Abklinglänge 30 nm bei 9 keV O ₂ ⁺ -Beschuß). Das Verschwinden dieses Oberflächenpeaks nach einer Behandlung mit HF und die Abhängigkeit der Abklinglänge von der Beschußenergie zeigen, daß ein Ionenstrahl-induzierter Effekt vorliegt. Untersuchungen Bor-dotierter Kristalle lassen auf die Existenz einer Oberflächenbarriere, wahrscheinlich die Oxidschicht, für die Eindiffusion von Deuterium schließen. Die Permeation von Deuterium durch diese Barriere beträgt 2×10¹¹ Atome/cm² s bei 350°C und nimmt mit abnehmender Temperatur stark ab.

     

Electroconduction,Association, and Ion–Molecular Interactions in Nickel Chloride Solutions in Methanol at 5–55°C

Results of a conductimetric investigation of nickel chloride in methanol at 5–55°C and electrolyte concentrations of 0.1–5 mM are presented. Limiting equivalent conductivities by Ni²⁺ and Cl^– and constants of ionic association in the first step with the formation of ionic pair NiCl⁺ are determined for asymmetric electrolytes using an extended Lee–Wheaton equation. In dilute nickel chloride solutions in methanol the association of ions in the second step is inessential. The size of dynamic solvation sheaths of the ions and the short-range non-coulombic interion potential suggest that the Ni²⁺ ion forms a kinetically and energetically stable solvated complex with the nearest solvation layer being 400 pm thick and virtually temperature-independent. The nearest kinetically stable solvation sheath of the Cl^– ion comprises mostly hydroxyl groups of methanol molecules and its stability is severely dependent on temperature.     

Synthesis of nanostructured nickel oxide

The process of formation of nickel oxide nanostructured powders by annealing nickel hydroxide in the temperature range 200–700°C was studied. Nickel hydroxide was prepared by precipitation with alkali from nickel nitrate solutions. The annealing process was shown to be multi-step. In the first stage the hydrogel Ni (OH)₂·nH₂O decomposes and partial dehydration of hydroxide occurs. Sizes of the formed particles decrease. At the temperatures above 230°C, further hydrogel decomposition and coalescence of NiO particles proceed. In view of the structural rearrangement of powder at the high temperatures 400–700°C, dehydration process is monitored by the decrease of NiO particles surface area at their coalescence. According to the change in the dehydration mechanism, the hierarchically nanostructured material forms, whose particle sizes are in the range 4–5, 9–12, and 18–40 nm.     

Effect of the Measurement Temperature on the Dispersive Component of the Surface Free Energy of a Heat Treated SiO2 Xerogel

The surface free energy of a monolithic silica xerogel treated at 1000°C has been measured by inverse gas chromatography in the temperature range 25–150°C using n-alkanes. Values of the dispersive component, _S ^D, vary from 49.07 mJ·m^–2 at 25°C to 17.20 mJ·m^–2 at 150°C. The _S ^D value obtained at 25°C is lower than that found for amorphous and crystalline silicas but higher than that found for glass fibres meaning that the heat treatment at 1000°C changes drastically the structure of the silica xerogel showing a surface similar to a glass. However, the higher value of _S ^D in comparison to glass fibres can be attributed to the mesoporous structure present in the silica xerogel. In the temperature range of 60–90°C there exists an abrupt change of the _S ^D values as well as in the dispersive component of the surface enthalpy, h _S ^D. Such abrupt change can be attributed to an entropic contribution of the surface free energy.     

Temperature-dependent dry etching characteristics of III–V semiconductors in HBr- and HI-based discharges

Microwave discharges of HBr/H₂/Ar and H/H₂/Ar with additional do biasing of the sample were used to etch InP, GaAs, and AlGaAs at temperatures between 50–250°C. The etch rates increase by factors of 3–50 and 5–9, respectively, for HBr-and HI-based discharges over this temperature range, but display non-Arrhenius behavior. The etched surfaces became very rough above 100°C for InP with either discharge chemistry due to preferential loss of P, while GaAs and AlGaAs are more tolerant of the elevated temperature etching. The near-surface electrical properties of InP are severely degraded by etch temperatures above 100°C, while extensive hydrogen in-diffusion occurs in GaAs and AlGaAs under these conditions, leading to dopant passivation which can be reversed by annealing at 400°C.     

The Detailed Mechanism of Oxidation of Ni-P Alloys

DTA in conjuction with X-ray diffraction analysis with a high-temperature camera and infrared spectroscopy was employed to determine the mechanism of oxidation of Ni-P alloys. Amorphous Ni-P powders were obtained from a nickel(II) sulphate bath as a nickel source and sodium dihydrophosphate(I) as a reducing agent. The crystallization product is composed of two phases: (f.c.c.) Ni and (b.c.t.) Ni₃P. The amorphous to crystalline transformation takes place in the temperature range 280–330°C. Ni₃P samples were heated from room temperature to 1050°C in air atmosphere at 5°C min⁻¹. It was found that the first stage of oxidation of Ni₃P goes through the intermediate phase of Ni₁₂P₅ formation to Ni₂P. Some exothermic reactions were observed. Heating runs were interrupted after each reaction for crystal structure determination by IR spectrometry. Infrared spectra are reported and it is shown that the structure units present in the amorphous products at about 700°C were the oxoanions PO₃ ⁻ and P₂O₇ ⁻. The final products of the oxidation process are NiO and Ni₃(PO₄)₂. This revised version was published online in July 2006 with corrections to the Cover Date.     

UV-Visible Absorption Characteristics of TEOS-Derived and Cr-Doped Silica Sonogels Aged in Different pH Solutions and Heat Treated up to 600°C

Cr-doped xerogels were obtained by sol-gel process from the acid-catalyzed and ultrasound-stimulated hydrolysis of tetraethoxysilane (TEOS) with addition of CrCl₃6H₂O in water solution during the liquid step of the process. The gels were aged immersed in different pH solutions for about 30 days, after that they were allowed to dry. The samples were annealed at temperatures ranging from 40 to 600°C and analyzed by UV-visible absorption spectroscopy. Cr³⁺ is the preferable oxidation state of the chromium ion in the gels annealed up to 250–300°C, in the case of aging in solutions of pH = 5 and 11. A high UV absorption below 320 nm, due to the host gel, and different absorption bands, depending on the temperature, due to the chromium ion were observed in the xerogels at temperatures below 250°C, in the case of aging in solutions of pH = 1 and 2. These absorption bands have not been assigned. Above 300°C up to 600°C, Cr⁵⁺, and possibly Cr⁶⁺, are the preferable oxidation states of the chromium ion independent of the pH of the aging solution, so the xerogels turn to a yellowish appearance in all cases.     

Preparation of Lithiated Co- and Ni-Oxide Powders and Thin Films by Wet Chemistry Processing

Layered lithiated Co- and Ni-oxide powders and thin films with rhombohedral (R m) structure were prepared by a peroxo wet chemistry route from Li(I), Co(II) and Ni(II) acetate precursors and the addition of H2O2. XRD analysis revealed that xerogel films and powders possessed a typical layered structure. Layered (R m) Li_0.99Co_1.01O₂ powder and Li_0.97Co_1.03O₂ films were formed around 500°C, while Li_0.93Ni_1.07O₂ powder and Li_0.94Ni_1.06O₂ oxide films were prepared around 550°C. The stoichiometry of the oxide films and powders was dependent on the heat-treatment temperature. The structure of sols, gels, xerogels and thin films was established from XRD spectra and from the FT-IR spectra, confirming their layered structure.     

Preparation of Porous Cordierite with Thermally Stable Pore Structure

A cordierite ceramic with a thermally stable pore structure was prepared by a simple modification of a sol-gel reaction of alkoxide precursors, synthesized from Mg metal or Mg acetate, Al(i-OPr)₃, and partially prehydrolyzed Si(OEt)₄. For aging and drying, wet cordierite gel was treated with water vapor at 150°C to strengthen the gel network through enhanced hydrolysis and condensation reactions. The cordierite xerogels showed BET surface areas between 220–410 m²/g, depending on the catalyst and treatment conditions used. In particular, water vapor treated xerogel displayed comparatively thermally stable pore characteristics, which exhibited only a 4–17% decrease in BET surface area up to 700°C, while samples prepared using the conventional sol-gel method showed a 55–91% reduction. Both the DTA and XRD patterns showed that crystallization began at 900°C leading to the -Cordierite phase and the subsequent phase transition to -cordierite at temperatures between 1050 to 1250°C.     

Synthesis of Ni-poor NiO nanoparticles for p-DSSC applications

To improve the performances of p-Dye Sensitized Solar Cell (p-DSSC) for the future, the synthesis of modified p-type nickel oxide semiconductor, commonly used as photocathode in such devices, was initiated with Ni₃O₂(OH)₄ as precursor. This specific nickel oxyhydroxide was first characterized by X-ray photo-electron spectroscopy and magnetic susceptibility measurements. Then its thermal decomposition was thoroughly studied in order to control the particles size of the as-prepared NiO nanopowders. Low temperature decomposition in air of this precursor allows the formation of Ni_1−xO nanoparticles with a large amount of Ni vacancies and specific surface areas up to 250 m² g⁻¹. Its ammonolysis at 250 °C leads to nanostructured N-doped NiO (NiO:N) materials.     

Preparation and Properties of Nb-Coated Barium Titanate Composite Particles by Surface Modification with Nb Alkoxide in Hydrophobic Solvent

Chemical processing for the preparation of Nb-coated barium titanate composite particles was investigated using surface modification technology, hydrolyzing Nb ethoxide on the surface of barium titanate particles dispersed in hydrophobic solvent.It was confirmed from the measurements of specific surface area and zeta potential as well as SEM, TEM and EDX observations of the resulting composite particles that the original barium titanate particles were coated uniformly with hydrolysis product of Nb ethoxide.Barium titanates coated with 1 wt% of Nb as oxide were well sintered at 1200–1300°C. The dielectric constants of the sintered barium titanates showed flattened temperature dependence, but it depended upon the average particle size of original barium titanate. The sintered bodies of Nb-coated barium titanate powders with average particle size of 0.2 m gave dielectric constants of 2000–3000 and those of barium titanate with average particle size of 0.5 m showed dielectric constants of 3000–4000 at room temperature.The microstructure of the sintered barium titanate coated with Nb oxide consisted of grains of about 1 m, smaller than those of sintered original barium titanate.     

Nickel(II) Oxide Solubility and Phase Stability in High Temperature Aqueous Solutions

A platinum-lined, flowing autoclave facility was used to investigate the solubility behavior of nickel(II) oxide (NiO) in deoxygenated ammonium and sodium hydroxide solutions, between 21 and 315°C. Solubilities were found to vary between 0.4 and 400 nmol-kg^–1. The measured nickel ion solubilities were interpreted via a Ni(II) ion hydroxo- and ammino-complexing model, and thermodynamic functions for these equilibria were obtained from a least-squares analysis of the data. Two solid phase transformations were observed: at temperatures below 149°C, the activity of Ni(II) ions in aqueous solution was controlled by a hydrous Ni(II) oxide (theophrastite) solid phase rather than by anhydrous NiO (bunsenite); above 247°C, Ni(II) activities were controlled by cubic rather than by rhombohedral bunsenite.     

Electrical Properties of Transparent Doped Oxide Films

In the present study n-type and p-type transparent conductive TiO₂ films were prepared by using sol-gel method. The n-type TiO₂ films were obtained by using Ti(OC₃H ₇ ⁱ )₄ solutions co-doped with Ru and Ta. The films were uniform and transparent in all the conditions, and their crystalline phases were anatase when HCl or HNO₃ was used as a catalyst. The resistivity decreased with increasing Ta content and increased with increasing Ru content. Most of the films showed resistivity minima at a heat-treatment temperature of 700°C. The lowest resistivity of 10¹ 10² cm was attained. The p-type TiO₂ films were obtained by using Ti(OC₃H ₇ ⁱ )₄ solutions co-doped with Co and Nb (Sb). The films were also uniform and transparent when AcAc was used, while samples heat-treated at 800°C became opaque when HCl was added. Rutile single phase appeared when the films were heat-treated at 700°C. Logarithmic resistivity of films co-doped with Co and Nb was directly proportional to the reciprocal absolute temperature. On the other hand, the slopes for films co-doped with Co and Sb were different below and above 200°–220°C. The activation energy at the low-temperature region is as low as 0.17 eV, and the resistivity at room temperature is 10⁴ 10⁵ cm.