Nickel nanoparticles

Koltypin Y, Fernandez A, Rojas CT, Campora J, Palma P, Prozorov R, Gedanken A (1999) Encapsulation of nickel nanoparticles in carbon obtained by the sonochemical decomposition of Ni(C8H12)2. Chem Mater 11 1331-1335... 

Shao et al. [25] prepared Mg Ni from magnesium and nickel nanoparticles produced by hydrogen plasma-metal reaction. Two preparation methods were developed to obtain the compound. One is heating the nanoparticles under 0.10 MPa argon pressure at 430°C and the other is under 3.00 MPa hydrogen pressure at 280°C. No hydrogen storage properties of this material were assessed. 

Figure 2.18 Kinetic of the hydrogenolysis of AsPhs on Ni/Si02 (175°C, 12barH2) and XRD analysis of the nickel nanoparticles resulting from such reaction [136].

Ni(CO)4 is the sole binary carbonyl complex of the elements of group 10 that is stable (Table 8.1). However, very few studies in which Ni(CO)4 is used in the preparation of catalysts have been reported [43]. This is probably due to the difficulty of manipulation of Ni(CO)4 and its very high toxicity. However, surface Ni(CO)4 species have been identified after the interaction of CO with highly dispersed supported nickel catalysts prepared by other routes [44]. Recent interest in the use of Ni(CO)4 has focused on the controlled production of nickel nanoparticles for specific purposes, such as in automotive converters [45]. The use of nickel tetracarbonyl as an agent for the nucleation process in the growth of single-wall carbon nanotubes has also been reported [46]. 

Sapkal SB, SheUce KE, Shingate BB, Shingare MS (2009) Nickel nanoparticle-catalyzed facile and efficient one-pot synthesis of polyhydroquinoline derivatives via Hantzsch condensation under solvent-lfee conditions. Tetrahedron Lett 50 1754-1756... 

Moreover, nanostructured materials are useful for the construction of NE. For example, a carbon NE has been reported by sealing of a carbon nanotube under an insulator layer [27]. NE ensembles have been obtained through self-assembling of gold nanoparticles [28] and carbon nanotubes [29] at derivatized substrates. Another interesting approach is the direct growth of carbon nanotubes on electrodes with dispersed catalytic nickel nanoparticles. In this case, highly dispersed carbon NE ensembles can be constructed [30]. 

Nickel-metal bonds, binuclear and polynuclear complexes, homometallic clusters, 8, 111 Nickel nanoparticles, preparation, 12, 87 Nickel-nitriles, synthesis and reactivity, 8, 150 Nickelocenes... 

The specific property of nickel nanoparticles deposited onto silicon substrates of different types of doping was also clearly manifested in another reaction we studied, hydrogenation of multiple bonds. It is known that the optimal situation for catalysis of processes of this kind is presence of a positive charge on metallic particles [43]. This can be achieved upon deposition of Ni nanoparticles onto p-type silicon. Indeed, experiments did show that the activity of Ni nanoparticles onto p-type silicon exceeds by nearly two orders of magnitude the activity of catalysts based on ultra-dispersed platinum and palladium, prepared by other methods. 

On the Fig. 2 we present kinetic curves of hydrogen accumulation at irradiation of the water-ethanol mixtures, containing powdered mesoporous Ti02, preliminary exposed to HTT and calcination at 350 - 500 °C, as well as commercial Ti02 Degussa P25, used without any pre-treatment. It could be seen from the Fig. 2, that the photoprocess proceeds with some acceleration at the initial stage of irradiation ( 0.5 h). This phenomenon may be explained by the formation of nickel nanoparticles and their saturation with atomic and molecular hydrogen (reactions (4)-(8)). 

Simulation results of Eqs. (1-2) in conjunction with equations of evaporative cooling [2,3] are presented and discussed. In particular, the change of radius of nickel nanoparticles of versus time is shown in Fig. 2 with Ni(N03)2 as the impurity which has been preliminary dissolved in the droplet. The initial droplet radius is 2 pm. 

The application of well-dispersed nickel nanoparticles inside the mesopores of MCM-41 by use of a nickel citrate chelate as precursor... 

The results that have been obtained with the catalysts after reduction and passivation are the same as those after calcination, i.e. the textural and structural properties of the support material have completely been retained after the treatments (as determined with nitrogen physisorption. X-ray diflfiaction and transmission electron microscopy). Information concerning the metallic nickel particles has been obtained with X-ray diffraction and transmission electron microscopy. Diflractograms of the catalysts after passivation are shown in Fig. 8. The observed features are exactly the same as for the oxidic systems (Fig. 4) only very broad and low diffractions are visible for the catalyst ex citrate, whereas sharp, intense peaks with a broad onset are observed for the catalyst ex nitrate. Consequently the nickel particles of the catalyst ex citrate have resisted sintering during the reduction treatment, thereby conserving the high dispersion of the catalyst. These results were confirmed by transmission electron microscopy measurements (not shown) only very small nickel nanoparticles situated inside the mesopores were found for the catalyst ex citrate. 

Scheme 4.14 Reduction of rajl-unsaturated carbonyl compounds using nickel nanoparticles.

Reductions. In refluxing isopropanol carbonyl compounds are reduced in the presence of nickel nanoparticles. Reductive amination is also performed under the same... 

Catalytic hydrogenation of alkenes and aUc3mes is achieved with nickel nanoparticles prepared from NiCl2 by reduction with Li and catal)dic amounts of DTBB and an alcohol. ... 

Metastable nickel carbide decomposes into metallic nickel and graphitic carbon that surrounds the nickel nanoparticles. 

Spherical nickel nanoparticles of 12-13nm in diameter can be obtained by reduction of various nickel salts by polyalcohols in the presence of appropriate stabilizers such as... 

T. Quid Ely, C. Amiens, B. Chaudret, E. Snoeck, M. Verelst, M. Respaud, and J, M. Broto. Synthesis of nickel nanoparticles. Influence of aggregation induced by modification of poly(vinylpyrrolidone) chain length on their magnetic properties. Chem. Mater, 11 526—h, 1999... 

Elimination of arsenic and mercury, present as organometallic compounds in crude-oil during extraction, is a major concern, especially for safeguarding the environment, but also for preservation of reforming catalyst activity and for plant protection from corrosion by arsenic and mercury. The usual method consists in trapping the heavy metal by a solid charge. In the IFP-RAM (g) process [121, 122], this charge is constituted of alumina-supported nickel nanoparticles. De facto, the... 

Scheme 18.20 Mechanism of cadmium deposition on a nickel nanoparticle.

Cadmium does not adsorb hydrogen. After full coverage of nickel nanoparticles by zerovalent cadmium atoms, the bimetallic Cd-Ni particle surface no longer activates hydrogen and reaction (18.1) is no longer possible. However, if the deposited atom (M ) is also able to activate the hydrogen molecule, reaction (18.1) must be continued by the formation of several M layers over nickel. This is indeed what has been observed when M =Ni or Co (Scheme 18.21). 

Scheme 18.21 Mechanism of nickel and cobalt deposition on a supported nickel nanoparticle.

---