Preparation of alumina–silica–nickel nanocomposite by in situ reduction through sol–gel route
12 Sep 2001-Science and Technology of Advanced Materials (IOP Publishing)-Vol. 2, Iss: 3, pp 449-454
TL;DR: In this paper, the presence of nickel particles of size ∼20nm in the nano-pores of an alumina-silica nanocomposite has been detected using X-ray diffraction and transmission electron micrograph.
About: This article is published in Science and Technology of Advanced Materials.The article was published on 2001-09-12 and is currently open access. It has received 14 citations till now. The article focuses on the topics: Nickel & Chloride.
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TL;DR: In this paper, a mixture of silica, organic, and carbon aerogels with metallic Ni and Pd was synthesized by impregnation, with Ni(acac)2 or Pd(acAC)2, of the silica wet gels followed by ethanol supercritical drying.
Abstract: We have prepared silica, organic, and carbon aerogels doped with metallic Ni and Pd through sol-gel processes. Silica aerogel nanocomposites have been synthesized by impregnation, with Ni(acac)2 or Pd(acac)2, of the silica wet gels followed by ethanol supercritical drying. Organic aerogels were prepared by sol-gel copolymerization of formaldehyde with the potassium salt of 2,4-dihydroxybenzoic acid, followed by ion exchange with either Ni(NO3)2·6H2O or Pd(OAc)2 and CO2 supercritical drying. No special reduction step was needed. Organic aerogels were further carbonized to obtain carbon aerogels. Pd organic and carbon aerogels containing 20–40% palladium nanoparticles are good catalysts for the Mizoroki–Heck reaction.
57 citations
TL;DR: In this paper, aniline was used as stabilizing agent for the Pd nanoparticles and the average particle size of the nanoparticles calculated from X-ray diffraction patterns were ∼24 nm and ∼28 nm, respectively.
50 citations
TL;DR: In this paper, the self-propagating low-temperature combustion method was used to produce nanocrystalline particles of zinc ferrite, which were characterized for chemical and phase composition, morphology and magnetic properties.
Abstract: The self-propagating low-temperature combustion method was used to produce nanocrystalline particles of zinc ferrite. The products were characterized for chemical and phase composition, morphology and magnetic properties. The results obtained showed the formation of single-phase zinc ferrite nanoparticles with an average particle size of about 40 nm. As-synthesized powder displayed good magnetic property. Due to the simplicity and low cost of this process, it could also become a valuable starting point for the generation of other mixed and complex ferrites.
49 citations
Cites background from "Preparation of alumina–silica–nicke..."
...As the research community is gaining a deeper understanding of these unique behaviours and applications of nanostructured materials, a new field of study known as ‘nanotechnology’ has emerged (Bhattacharyya et al 2001; Kondic and Diez 2009)....
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TL;DR: In this paper, the phase purity of ZnFe 2 O 4 was confirmed by X-ray diffraction studies and high resolution transmission electron microscopic analysis and selected area diffraction pattern also confirmed the correct crystalline phase formation.
44 citations
TL;DR: In this article, the authors deal with the synthesis of NiO/SiO 2 nanocomposites fabricated by embedding nickel oxide particles, obtained from hexahydrated nickel nitrate (Ni(NO 3 ) 2 ·6H 2 O), in a silica matrix, through sol-gel method based on hydrolysis and condensation of tetraethyl orthosilicate (TEOS) alkoxide.
17 citations
References
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TL;DR: In this article, high-density nickel-dispersed-alumina composites with superior mechanical properties were obtained by the hydrogen reduction and the hot pressing of alumina-nickel oxide (Al2O3/NiO) mixed powders by using NiO or nickel nitrate (Ni(NO3)2·nH2O) as a dispersion source of nickel metal.
Abstract: High-density nickel–dispersed-alumina (Al2O3/nickel) composites with superior mechanical properties were obtained by the hydrogen reduction and the hot pressing of alumina–nickel oxide (Al2O3/NiO) mixed powders. The mixtures were prepared by using NiO or nickel nitrate (Ni(NO3)2·nH2O) as a dispersion source of nickel metal. Microstructural investigations of the composite fabricated using nitrate powder revealed that fine nickel particles, } 100 nm in diameter, dispersed homogeneously at the matrix grain boundaries, forming the intergranular nanocomposite. High strength (.1 GPa) and high-temperature hardness were registered for the composite that contained a small amount of nickel dispersion. The ferromagnetic properties of nickel, such as high coercive force, were observed, because of the fine magnetic dispersions, which indicates a functional value of structural composites.
261 citations
TL;DR: A review of the current status of research and development on the structure and properties of nanocrystalline materials can be found in this paper, where a critical analysis of this aspect and grain growth is presented.
Abstract: The present article reviews the current status of research and development on the structure and properties of nanocrystalline materials. Nanocrystalline materials are polycrystalline materials with grain sizes of up to about 100 nm. Because of the extremely small dimensions, a large fraction of the atoms in these materials is located at the grain boundaries, and this confers special attributes. Nanocrystalline materials can be prepared by inert gas-condensation, mechanical alloying, plasma deposition, spray conversion processing, and many other methods. These have been briefly reviewed. A clear picture of the structure of nanocrystalline materials is emerging only now. Whereas the earlier studies reasoned out that the structure of grain boundaries in nanocrystalline materials was quite different from that in coarse-grained materials, recent studies using spectroscopy, high-resolution electron microscopy, and computer simulation techniques showed unambiguously that the structure of the grain boundaries is the same in both nanocrystalline and coarse-grained materials. A critical analysis of this aspect and grain growth is presented. The properties of nanocrystalline materials are very often superior to those of conventional polycrystalline coarse-grained materials. Nanocrystalline materials exhibit increased strength/hardness, enhanced diffusivity, improved ductility/toughness, reduced density, reduced elastic modulus, higher electrical resistivity, increased specific heat, higher thermal expansion coefficient, lower thermal conductivity, and superior soft magnetic properties in comparison to conventional coarse-grained materials. Recent results on these properties, with special emphasis on mechanical properties, have been discussed. New concepts of nanocomposites and nanoglasses are also being investigated with special emphasis on ceramic composites to increase their strength and toughness. Even though no components made of nanocrystalline materials are in use in any application now, there appears to be a great potential for applications in the near future. The extensive investigations in recent years on structure-property correlations in nanocrystalline materials have begun to unravel the complexities of these materials, and paved the way for successful exploitation of the alloy design principles to synthesize better materials than hitherto available.
207 citations
TL;DR: In this paper, the optical absorption spectra of glass-metal nanocomposite films have been measured over the wavelength range 200 to 2000 nm, and effective medium theories of Maxwell-Garnett and Bruggeman, respectively, have been used to calculate theoretically the absorption of these materials.
Abstract: Glass-metal nanocomposites incorporating ultrafine particles of iron, nickel, cobalt and manganese, respectively, in a silica glass matrix have been prepared by heat treatment of a gel derived from a sol containing silicon tetraethoxide and a suitable metal organic compound. Metal particles in all the nanocomposites are isolated and spherical-shaped with diameters ranging from 3 to 10 nm. Films of these nanocomposites with thickness of the order of a few micrometres have been prepared on glass slides by a simple dip-and-pull technique. Optical absorption spectra of the nanocomposite films have been measured over the wavelength range 200 to 2000 nm. Effective medium theories of Maxwell-Garnett and Bruggeman, respectively, have been used to calculate theoretically the optical absorption of these materials. The Maxwell-Garnett theory gives results which are in better agreement with experimental data than those obtained from Bruggeman formalism. The filling factor f as estimated from the least-squares fit of the experimental results with the Maxwell-Garnett theory has a value in the range 1 to 4%.
92 citations
Abstract: Different reaction paths of mullite formation via sol-gel processing techniques are reviewed. These variations are due to differences in hydrolysis/gelation behaviours of the silica and alumina components used. Variations of pH during processing without altering other variables follow three different routes of mullite formation. In the highly acidic region(pH ⩽ 1), the gel does not exhibit a 980 °C exotherm but forms γ-Al2O3. Mullite forms at high temperature by diminution of α-Al2O3 and β-cristobalite, respectively. In the pH range of 3–4.5, gels exhibit a 980 °C exotherm and develop only mullite. In the highly alkaline region (pH ∼ 14), the gel produces a Si-Al spinel phase at the 980 °C exotherm and mullite formation at the ∼ 1330 °C exotherm takes place from the intermediate Si-Al spinel phase.
47 citations