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The Synthesis Design And Performance Study Of Branched Nickel Nanomaterials And Cobalt Nanomaterials

Posted on:2014-04-14Degree:MasterType:Thesis
Country:ChinaCandidate:H Y QiuFull Text:PDF
GTID:2251330398983460Subject:Chemical Engineering and Technology
Abstract/Summary:PDF Full Text Request
Branched metal nanocrystals attract the attention of many people because their dense corner and edge made them have promising application in catalysis, sensing, electronics and so on.Very recently, a novel approach that applies the strong surface adsorption of small adsorbents, such as H2and CO to control the surface shape of nanocrystal, has been successful in several systems. For example, Pd tetrapod nanocrystals were synthesized by a CO-assisted approach. Pd cubic dendrites and fivefold stars were obtained under H2condition.Ni surfaces have strong interactions with H2molecules. The adsorption/desorption kinetics of atomic H on Ni surfaces with various crystal face indexes have been investigated experimentally and theoretically. The atomic hydrogen-surface interaction should be an effective pathway to control the surface kinetics of metallic nickel, which finally stimulates the anisotropic overgrowth of Ni nanocrystals. In the present study we demonstrate a H2-assisted approach for the synthesis of branched Ni nanocrystals with predictable morphologies, such as secondary-branching particles, and multipods. It was demonstrated that H2pressure in the synthetic autoclaves plays a key role in controlling the branching behavior of Ni nanocrystals. Compared with their spherical counterparts, these branched Ni nanocrystals show the enhanced catalytic activity in the model heterogeneous hydrogenation reactions, such as acetophenone and nitrobenzene hydrogenations.Based on this work, we developed an approach to synthesis of Co nanocrystals, and discussed the stirring speed, reaction time, and the pressure of H2which determines the shape of cobalt. compared to static method to produce Co nanoparticles, this urchin-like cobalt rich in surface area,which have good catalytic activites. and this need more reaearch.
Keywords/Search Tags:branched Ni nanocrystals, multipods, surfacemorphology, catalytic performance, linear Co nanocrystals
PDF Full Text Request
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