Narrow Results

The Free-energy Concentration Expansion Method (FCEM) was utilized for the prediction of compositional structures in Ni–Cu–Rh cubo-octahedron nanoclusters in comparison to recently reported Ni–Cu–Pd data. While both systems exhibit site-specific, sequentially competitive surface segregation (and resultant core separations), remarkable differences governed by the opposite heteronuclear effective interactions, were noted in the surface compositional patterns. Thus, at relatively low temperatures "mixed" Cu/Pd ordering takes place at the Ni–Cu–Pd cluster surface, whereas in the Ni–Cu–Rh cluster Cu and Ni populate separate low and high-coordinated surface sites, thus forming a kind of "demixed surface order". Dissimilarities in the temperature dependence are discussed in terms of the interplay of segregation and compositional order. Such findings may have implications in heterogeneous catalysis and other technologies based on highly dispersed alloyed particles.

Nickel films electrodeposited from chloride and sulfate baths at pH 3.8 have been investigated. The influence of the plating baths on the electrochemical growth and the characteristics of nickel were studied by means of cyclic voltammetry, potentiostatic steps (chronoamperometry), atomic force microscopy (AFM) and X-ray diffraction (XRD) techniques. The electrocrystallization mechanism was analyzed using the Scharifker and Hills model. The nucleation mechanism was found to be progressive at -1.1 V versus SCE, while at elevated overpotentials (more negative than -1.2 V versus SCE) instantaneous nucleation behavior was obtained. AFM characterization of the deposits indicated that the baths composition influences greatly the morphology of the deposits. XRD analysis indicated polycrystalline growth of the Ni film with a preferred (111) orientation with the fcc structure for both baths. The Ni crystallite sizes are 19–31 nm for the sulfate bath and 14–33 nm for the chloride one.

Carbon Nanotubes (CNTs) filled with metals can be used in capacitors, sensors, rechargeable batteries and so on. In this study, the process of Nickel filling into single wall CNTs was studied by molecular dynamics (MD) simulation. Three models consisting of Nickel atoms and CNTs were established. These models were cooled from 1500 K to 100 K to analyze the factors that influence the filling height, such as temperature, the force between Carbon and Nickel atoms, as well as CNTs diameter. The results showed that filling height increased as the temperature and the force between Carbon–Nickel atoms rised. Filling height reduced with the increasing diameter of CNTs.

Ni@onion-like carbon (OLC)/reduced graphene oxide (RGO) nanocomposites were synthesized, and their multicomponent microstructure was confirmed by X-ray diffraction, transmission electron microscopy, Raman spectra, the thermal gravimetric analysis and magnetic hysteresis loops. The obtained nanocomposite possesses a unique structure, in which core–shell Ni@OLC nanocapsules are decorated on the surface of RGOs. The synergistic effect of the dielectric loss of RGO and OLC and the magnetic loss of Ni nanoparticles can be constructed. The RGO can provide tremendous electric dipoles. Multi-interface among RGO, OLC and Ni nanoparticles can enhance dielectric performance and cause multiple reflections. The combination of these merits makes the nanocomposite a promising candidate material for electromagnetic absorber. The 20wt.% nanocomposite-paraffin composite can possess an optimal reflection loss (RL) of $-47.5$dB at 9.75GHz with a thickness of 3.1mm. When the thickness is 2.0mm, the RL of composite can reach $-32.6$dB at 17.4GHz. The effective frequency is 6.54GHz (11.16–17.7GHz) for 2.4mm thickness layer.

The current demand for more sustainable catalytic processes has seen a clear shift from the classical noble-metal-based catalysts to cheaper and abundant metals. The focus on earth-abundant transition-metal-based catalysts has been marred by synthetic and characterization challenges but is ultimately achieving the desired catalytic results. To extract the catalytic potential of earth-abundant transition-metal-based complexes, great care concerning the design of the supporting ligands is required. Under certain conditions, monoanionic bidentate chelates present a good strategy to tackle those goals. The 2-iminopyrrolyl framework is a good example of that: Its huge electronic and steric tuning potential has paved the way for diverse coordination chemistries of first-row transition metals, from manganese to copper. With such metal complexes in hand, several catalytic applications have been studied, namely polymerization, hydrofunctionalization and click chemistry. This chapter features the main catalytic achievements of complexes of earth-abundant metals bearing 2-iminopyrrolyl ligands and their respective mechanistic insights and structure–reactivity relationships.

The catalytic functionalization of C–H, C–OH and C–C bonds belongs to the most important processes in nature and the industry. In nature, this process occurs via involvement of enzymes, effectively and selectively, usually with very high turnover numbers. The pivotal role in enzymatic activity is played by the metal center cofactors, which involve several bioavailable transition metals, such as, iron, copper, manganese and zinc. In the industry, bond functionalization requires the presence of metal catalysts; therefore, a bio-inspired design of metal catalysts is a challenging approach. The recent advances in the catalysis of industrially important reactions, namely the oxidation and hydrocarboxylation of alkanes, the oxidation of alcohols and C–C coupling are reported. Convenient, environmentally friendly methods are presented, and the role and efficacy of the various transition-metal (iron, copper, zinc, manganese, nickel, vanadium, palladium and cobalt) catalysts are explored.