Nano-sized Nickel Research Articles

Effect of Cadmium Substitution on Structural and Magnetic Properties of Nano Sized Nickel Ferrite

The structure and crystal phase of the nanocrystalline powders of Ni1–xCdxFe2O4 (0≤x≤0.5) mixed ferrite, synthesized by wet chemical co-precipitation method, were characterized by X-ray diffraction. Results showed that the lattice parameter increased with increasing Cd concentration. Microstructure was studied by scanning electron microscopy. TG/DTA studies were carried out on co-precipitated sulphate complexes. These studies revealed the low ferritization temperature (650 °C) of the ferrite system synthesized by presently adopted route of synthesis and occurrence of simultaneous decomposition and ferritization processes. Further studies by infrared spectroscopy were also conducted. Moreover, magnetic properties of the prepared nanoparticles were studied by magnetization and a.c. susceptibility measurements. The response of prepared Ni1–xCdxFe2O4 mixed ferrites to magnetic field was investigated. Results show that, magnetic susceptibility, Curie temperature, and effective magnetic moment decreased as the Cd content increases.

The use of nano supported nickel catalyst in reduction of p-nitrophenol using hydrazine as hydrogen donor

p-Aminophenol was prepared by hydrogenation of p-nitro phenol over nano-sized nickel catalysts supported on two different supports, SiO2 and Al2O3. Hydrazine hydrate was used as hydrogen source in this reaction. Several loadings of nano-sized Ni were used, thus 20, 5, and 2.5 wt% were prepared. X-ray diffraction (XRD) and electron spin resonance (ESR) were employed to investigate the prepared catalysts. The Ni/Al2O3 was found to be more effective and give high durability. The catalytic activity of the reaction was found to be influenced by both the crystallinity of the nickel and the strain among nano-sized nickel particles. The prepared catalysts showed higher catalytic activity, especially at lower loading. During the reaction, a detectable change of the color was observed from yellow to green and finally to colorless, which enable us to suppose a mechanism of this reaction.

Synthesis of nano-nickel by a wet chemical reduction method in the presence of surfactant (SDS) and a polymer (PVP)

Nano-sized nickel particles have been synthesized by a bottom-up approach, using hydrazine as the reducing agent in the presence of an anionic surfactant - sodium-dodecyl sulphate (SDS). The effect of adding a cationic polymer -polyvinylpyrrolidone (PVP) with an anionic surfactant has been studied at two different temperatures; the rate of reduction increased as the reaction temperature was increased from 60 to 100°C. These nano-aggregated nickel particles were characterized by using SEM with EDX facilities, TEM and XRD. TEM characterization showed the presence of spherical Ni particles as fine as 10 nm in diameter. However, the SEM images showed a very spiky morphology; very small spherical shaped objects were clearly observed within these spiky structures. XRD studies show that the nickel crystals have fcc structure. The combination of SDS/PVP reaction produced nano-sized nickel particles which were much finer than the reactions where SDS was used on its own. PVP has shown some dispersion power and was found to be capable of preventing nickel particles from gradual agglomeration.

Synthesis of Nano-sized Nickel Particles by a Bottom-up Approach in the Presence of an Anionic Surfactant and a Cationic Polymer

Nano-sized nickel particles have been synthesized by a bottom-up approach, using hydrazine as the reducing agent in the presence of an anionic surfactant - sodium-dodecyl sulphate (SDS). The effect of adding a nonionic polymer -polyvinylpyrrolidone (PVP) with an anionic surfactant has been studied at two different temperatures; the rate of reduction increased as the reaction temperature was increased from 60 to 100°C. These nano-aggregated nickel particles were characterized by using SEM with EDX facilities and TEM. TEM characterization showed the presence of spherical Ni particles as fine as 10nm in diameter. However, the SEM images showed a very spiky morphology, very small spherical shaped objects were clearly observed within these spiky structures. The combination of SDS/PVP reaction produced nano-sized nickel particles which were much finer than the reactions where SDS was used on its own. PVP has shown some dispersion power, and was found to be capable of preventing nickel particles from gradual agglomeration. Keywords: Bottom-up; SDS; PVP; 10 nm. © 2010 JSR Publications. ISSN: 2070-0237 (Print); 2070-0245 (Online). All rights reserved. DOI:10.3329/jsr.v2i2.3261 J. Sci. Res. 2 (2), 313-321 (2010)

Enhanced Hydrogen Storage in MWCNTs Decorated by Electroless Nickel Nanoparticles Deposited in Supercritical CO<sub>2</sub> Bath

Nano-sized nickel particles were dispersed on multi-walled carbon nanotubes (MWCNTs) via an improved electroless deposition route using a supercritical CO2 fluid. The microstructure, chemical composition and crystallinity of the Ni-decorated CNTs were examined using a transmission electron microscope (TEM), an X-ray energy dispersive spectrometer (EDS), and an X-ray diffractometer (XRD), respectively. The analytical results indicate that, with assistance of the supercritical fluid, Ni nanoparticles with a diameter of approximately 10 nm can be uniformly dispersed on the surface of CNTs. The hydrogen storage capacity of the Ni-decorated CNTs was evaluated with a high-pressure microbalance at room temperature and under a hydrogen pressure of 6.89 MPa. The measured hydrogen adsorption amount of the Ni/CNTs nanocomposite was 1.06 wt%, which was much higher than 0.33 wt% found for the plain CNTs.

Interface microstructure and diffusion of vacuum annealed ceramic coating on superalloy GH202

In order to improve the wear resistance and high-temperature oxidation resistance of superalloy GH202, the ultrafine-grain ceramic coating containing nano-size nickel particles was obtained by flow coat method on the surface of GH202. The interface microstructure between ceramic coating and superalloy GH202 substrate during vacuum diffusion was studied. It is shown that Al 2O 3 oxide layer and (Ti, N) compound exist in the alloy substrate close to interface. During long time diffusion, nano-size nickel powders gradually congregate and grow up, and the confluent interface appears, which shows that the nano-size nickel powders have the effect of restraining the coating from failure.

Effect of initial solution apparent pH on the performance of submerged hybrid system for the p-nitrophenol hydrogenation

Coupling nanocatalysis with ceramic membrane separation can solve the problem of nanocatalyst separation in situ from a reaction mixture. A submerged hybrid system combining nanocatalysis and ceramic membrane separation was designed for the liquid phase hydrogenation of p-nitrophenol to p-aminophenol, and the effect of initial solution apparent pH (pHa) on the performance of submerged hybrid system was investigated in detail. It is demonstrated that as the initial solution pHa is adjusted from 4.5 to 7.5, the catalytic stability of nano-sized nickel is remarkably improved, possibly because the formation of impurity on the nickel surface can be restrained at weak alkaline condition, while the catalytic activity and selectively almost do not change. The membrane permeability is not affected significantly by the initial solution pHa.

Phase formation and change of magnetic properties in mechanical alloyed Ni 0.5Co 0.5Fe 2O 4 by annealing

The effects of milling time and annealing temperature on phase formation, microstructure and magnetic properties of nickel–cobalt ferrite synthesized from oxide precursors by mechanical alloying were studied. The study of milling time effects on phase formation of milled materials showed that if milling continues up to 55 h, single phase nano-sized nickel–cobalt ferrite is obtained. Also, magnetic properties of powders versus milling time and annealing at different temperatures extensively changed, so that annealing at 1200 °C increased the magnetization saturation of the as-milled powder from 15.1 to 53.6 emu/g. X-ray powder diffraction technique (XRD) with Cu–Ka radiation was employed for phase identification. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were also used to determine the morphology and size of the particles. The magnetic properties were measured by a vibration sample magnetometer (VSM).

Graphitic encapsulation of micron- and nano-sized Ni particles using ethylene as precursor

This work deals with the catalytic decomposition of carbon-containing gases (ethylene) over nickel catalysts to grow graphitic capsules at relatively low temperatures (853 K). The influence of different experimental conditions, such as catalyst size, reactant flow ratio (C 2H 4:O 2), gas flow rate and temperature, is studied. The size of the nickel particles determines the type of structures; while nano-sized nickel particles favor the growth of nanofilaments, graphitic capsules occur over nickel microparticles. The use of reducing and oxidizing environments in the growth of graphitic structures over microparticles are compared, the latter being more appropriate for growing nanofilaments. Below 853 K, no graphitic structures are formed. Moreover, a new model is proposed for the encapsulation of the catalyst metal particles by graphite layers.

Gelatin induced reduction of uniform nano-platelets of Ni(OH) 2 to Ni metal

Uniform stable nanosize nickel platelets were prepared by first coating Ni(OH) 2 particles of the same shape with gelatin and then heating them at moderate temperatures in nitrogen without addition of any reducing agents. The resulting platelets consist of a mixture of Ni and NiO. Depending on the amount of gelatin coating and temperature, up to 73% of solids were converted to the metal. Subsequent heating of such powders at 190 °C in a stream of 5% H 2 in N 2 produced only Ni platelets with a modal length of ∼60 nm and several nm thick.

A Submerged Ceramic Membrane Reactor for the <I>p</I>-Nitrophenol Hydrogenation Over Nano-Sized Nickel Catalysts

The catalytic hydrogenation of p-nitrophenol to p-aminophenol over nano-sized nickel catalysts was carried out in a submerged ceramic membrane reactor. It has been demonstrated that the submerged ceramic membrane reactor is more suitable for the p-nitrophenol hydrogenation over nano-sized nickel catalysts compared with the side-stream ceramic membrane reactor, and the membrane module configuration has a great influence on the reaction rate of p-nitrophenol hydrogenation and the membrane treating capacity. The deactivation of nano-sized nickel is mainly caused by the adsorption of impurity on the surface of nickel and the increase of oxidation degree of nickel.

Synthesis and characterization of nano-sized nickel catalyst supported on SiO2–Al2O3

support on thecatalytic activity of nickel catalyst. The reaction used in this studywas the hydrogenation of p-nitrophenol into p-aminophenol.p-Aminophenolisconsideredtobeveryimportantintermediateinthemanufactureofmanyanalgesicandantipyreticdrugs,suchasparacetamol,acetanilide,phentacin,...etc.[9–15].Itisalsousedasadeveloper in photography (under trade names of activol or azol), inaddition of its use in chemical dye industries [16].There are several methods used in the preparation of p-aminophenolfromp-nitrophenolsuchas:(1)metal/acidreduction[17], (2) catalytic hydrogenation [18], (3) electrolytic reduction[19], (4) homogeneous catalytic transfer hydrogenation [20], and(5) heterogeneous catalytic transfer hydrogenation, etc.Among all previously mentioned methods, direct catalytichydrogenation of p-nitrophenol to p-aminophenol becomes themost important one. This is because it could be an efficient routefor synthesis [15]. Raney nickel [21], nano-sized nickel [22] andseveral noble metal catalysts, such as Pd/C [15], have been used ascatalysts for this reaction. Due to their lowest cost and highercatalytic activity, supported nickel catalysts, are widely used insuch reactions [15–21].Although nickel catalyst is used in hydrogenation reactions[23–29], only few recent researches have been carried out onhydrogenation of p-nitrophenol over nano-sized supported nickelmetal catalyst [10,30,31].The present investigation reports the results of an intensivestudy on preparation and characterization of nano-sized metallicnickel supported on SiO

Synthesis of nickel–rubber nanocomposites and evaluation of their dielectric properties

Nanocomposites based on natural rubber and nano-sized nickel were synthesized by incorporating nickel nanoparticles in a natural rubber matrix for various loadings of the filler. Structural, morphological, magnetic and mechanical properties of the composites were evaluated along with a detailed study of dielectric properties. It was found that nickel particles were uniformly distributed in the matrix without agglomeration resulting in a magnetic nanocomposite. The elastic properties showed an improvement with increase in filler content but breaking stress and breaking strain were found to decrease. Dielectric permittivity was found to decrease with increase in frequency, and found to increase with increase in nickel loading. The decrease in permittivity with temperature is attributed to the high volume expansivity of rubber at elevated temperatures. Dielectric loss of blank rubber as well as the composites was found to increase with temperature.

A Facile Route to Nano-Sized Nickel Sulfide via Thermolysis of Nickel Alkanethiolate

Nano-sized nickel sulfides were synthesized by the thermolysis of nickel alkanethiolates in the presence of coordinating ligands. Nickel alkanethiolates were synthesized by the reaction of the square planar nickel 1-dimethylamino-2-methyl-2-propanolate [Ni(dmamp)2] with various n-alkanethiols. The effect of ligands in the reaction system has been investigated to control the size and shape of nano-sized nickel sulfides. TEM images show that the products are nano-sized nickel sulfides in rod and plate shapes. Nickel alkanethiolates and nano-sized nickel sulfides have been characterized by means of X-ray diffraction and transmission electron microscopy.

Effect of initial solution apparent pH on nano-sized nickel catalysts in p-nitrophenol hydrogenation

Abstract The effect of initial solution apparent pH (pHa) on nano-sized nickel in the catalytic hydrogenation of p-nitrophenol to p-aminophenol was investigated in detail. Experimental results show that the catalytic activity of the nano-sized nickel shows a strong dependence on the initial solution pHa, and is the highest at the initial solution pHa 4.8. At lower or higher pHa values the nano-sized nickel will obviously deactivate, but the deactivation mechanisms are fully different. With respect to the former, the nickel dissolution and the strong adsorption of the complex compound of nickel ion and p-nitrophenol on the surface of nano-sized nickel are the main reasons. The severe agglomeration of nickel particles also causes the deactivation of nickel used at the initial solution pHa 1.6. For the latter the main reasons are the formation of nickel hydroxide surface species and the decrease of p-nitrophenol adsorption on the hydrogenation sites.

A gas-chromatography study of adsorption properties of silica modified by stable nickel nanoparticles obtained in reverse micelles under γ-radiation

Stable nano-sized nickel particles are prepared using the radiation-chemical synthesis in reverse micelles. Adsorption properties of raw silica (silochrome, S-120), the silochrome modified by a micelle-forming compound (AOT), and the silochrome modified by the nano-sized nickel particles are studied using gas chromatography method. The retention times for different test-compounds at different temperatures are determined for these adsorbents. Specific retention volumes of the test-compounds, as well as the thermodynamic adsorption characteristics, are determined. After the modification, the initial adsorption heat for n-hydrocarbons increases, which points out to the higher surface roughness of the modified samples. For the nickel-nanoparticle-modified silica, the contribution of specific interactions of polar compounds is less than that for the unmodified silica; this can be explained by screening the active centers (OH-groups) of the silica gel by the metal nanoparticles. The silica polarity decreases after the modification. The gas chromatography method allows detecting the difference in the properties of nanocomposites containing Ni- and NiO-nanoparticles.

Nickel Decoration on Multi-Walled Carbon Nanotubes Using Multi-Step Impregnation Method

In this work, nano-sized nickel particles were dispersed on multi-walled carbon nanotubes using multi-step impregnation method, to use them as hydrogen storage media. The dispersion degree of nickel particles on multi-walled carbon nanotubes is inversely proportional to the nickel concentration of solution. It was observed that the low nickel concentration is efficient to decorate nickel particles into the inner space. Multi-step impregnation method of MWNTs through several times with low nickel concentration is more efficient to manufacture Ni-MWNTs having well dispersed metallic nickel particles.

Nanoindentation of heterogeneous carbonaceous films containing Ni nano-crystals

Composite films of nano-size nickel grains embedded in a carbonaceous matrix are synthesized by a PVD process of C 60 fullerenes and Ni acetate. The morphology of the nano-composite films is characterized by TEM, selected area electron diffraction, chemical analysis and AFM. Correlations with deposition parameters and typical structure changes are found. The mechanical properties are analyzed by nanoindentation. The load–displacement charts show typical pop-ins correlated with the heterogeneous nano-structure. The depth dependent hardness and indentation modulus vary according to the nano-composite structure and reflect the changes of the mechanical properties in the film.

Evaluation of Nano-Sized Nickel Dispersed Alumina Materials

In order to develop new ceramics for a power electric device, alumina/nickel (Ni) nanocomposites were fabricated using the soaking method and the pulse electric current sintering technique. The volume fractions of Ni were 0.5, 1, and 5% in γ–alumina powder. 10mass% α–alumina powder was added as a sintering seed. SEM and TEM observations revealed that the nanocomposites exhibited an intra-granular fracture mode, and agglomerated Ni particles existed mostly along alumina grain boundaries especially for 5vol% Ni. The experimental results showed that the strength and fracture toughness values of the nanocomposites were higher than those of monolithic alumina, and the thermal conductivity decreased slightly with increase in Ni content. Moderate improvements in the strength and fracture toughness seemed to result from the fact that the nano-sized Ni particles dispersed within alumina grains creating dislocations around the Ni particles, which reduced sintering residual stresses in alumina grains and expanded the frontal process zone size. It was concluded that nanocomposites with a lower Ni content had better mechanical, electrical, and thermo-mechanical properties.

Reactive adsorption of sulfur compounds in diesel on nickel supported on mesoporous silica

Sulfur compounds in commercial diesel were selectively removed by reactive adsorption using metallic nickel nanoparticles supported on mesoporous silica. Nanosize nickel particles were supported on mesoporous silica SBA-15 and KIT-6 by impregnation of nickel nitrate and subsequent reduction. X-ray diffraction and transmission electron microscopy study revealed that the maximum nickel concentration achieved was 30wt% for both the substrates, before particle agglomeration sets. Under these conditions, the best dynamic adsorption capacity observed was 1.7mg/g at 10ppmw S breakthrough level with a high sulfur diesel (240ppmw) on 30wt% Ni/SBA-15. For a low sulfur diesel (11.7ppmw), the corresponding result was 0.47mg/g for the same adsorbent at 0.1ppmw S breakthrough level, which is suitable for fuel cell applications.