Preparation, Application And Simulation Of Magnetic Nanoparticles Comprised Of Cobalt

Magnetic nanoparticles have good application foreground in the fields such as catalysis, radio frequency absorber, magnetic resonance imaging and magnetic data storage, due to their unique physical and chemical properties. However nanoparticles unique physical and chemical properties depend on their dimension of the particles and the degree of dispersion. So, it is a hot topics to know preparation of monodisperse single metallic. At the same time, mechanism of nanoparticles’growth, the mechanism of hydrogenation are studied by theoretical workers.In this thesis, we prepared the transition metal acetylacetonates precursors firstly. Then monodisperse Co nanoparticles and CoNi nanoparticles have been prepared via the chemical solution method, which have been further characterized by X-ray diffractions (XRD) Infrared spectrum (IR) and Transmission electron microscopy (TEM). It was researched for catalytic hydrogenating acrylonitrile(containing C=C and C= N) using the prepared cobalt and nickel-cobalt alloy nanoparticles as catalyst. At the same time, the lowest-energy geometric structures and their corresponding stability of Con(n=2-20) clusters have been studied using first-principles method based on the density functional theory(DFT). Finally, the action of H on Co13 cluster and the mechanism of acrylonitrile hydrogenation have been investigated by using Materials Studio6.1.During the preparation of Con Ni-Co alloy nanoparticles, the influences of temperature, reducing agent, and other factors have been considered. The results showed that non-coalescence, and 9.3nm-average-sized Co Nanoparticles can be prepared using the Co(acac)2 as the precursor, hydrogen at atmosphere,1,2-Dodecanediol as the reaction and reductive, by adding protective agents at 250℃. Based on the preparation of the cobalt Nanoparticles, non-coalescence, and 8.2nm-average-sized CoNi alloy Nanoparticles can be prepared using the Co(acac)2 and Ni(acac)2 as the precursors, hydrogen at atmosphere,1,2-Dodecanediol as the reaction and reductive, by adding protective agents at 220℃Catalytic hydrogenating the acrylonitrile and using the prepared cobalt and nickal-cobalt alloy nanoparticles as catalyst, research is done about the effects of temerature and reaction time on the catalytic properties of catalysts and the selectivity to C=C can resch 100%。The lowest-energy geometric structures and their corresponding magnetic moments of Con(n= 2-20) clusters have been studied using first-principles method based on the density functional theory(DFT) using Materials Studio6.1. Firstly, this paper calculats the lowest-energy structure and its isomers with molecular mechanics of FORCITE. Secondly, Con(n= 2-20) clusters are calculated quantum mechanics by using DMol cluster method. According to the binding energy to select the most stable structure, and get so-called magic clusters n=6,13 by investigating the stability of the Con(n= 2-20) clusters from binding energy, Second derivative of the cluster binding energy, Ionization energy, chemistry hardness, formation energy, average bond length, average coordination number and the magnetic moment. According to the results, magnetic moment of the icosahedron Co13 clusters is close to block material. In the optimization process, it is found that for very small cobalt clusters (2≤n≤4), its steady state structure geometric configurations to plane structure, and improved symmetry of clusters can enhance the stability of clusters, and the growth of Con (11≤n≤13) is in an icosahedral pattern, and Con(14≤n≤20) in double icosahedron.Two paths of acrylonitrile hydrogenation were investigated in this work. Pathl hydrogenate directly, Path2 hydrogenate through H shift. Compared to path2, Pathl is more suitable. In Path1 the proportion between selectivity to C=C and selectivity to C≡N is 5:1, which is fit the result of experiment. The energy of intermediate state and transition state referred to path2 is higher than those involved in path1.