Preparation And Structure Of Carbon Encapsulated Fe Hollow Nanoparticles

Carbon-encapsulated metal hollow nanoparticles(CEMHNs) are a new kind of hollow structure nanocomposite, in which graphite arrange around metal hollow nanoparticles located in the center. Because of the carbon layers preventing metal nanoparticles from environment effection, they have good stability in environment.The research focused on the preparation of CEMHNs by co-pyrolysis of 1,3-benzenediol and ferrocene in dimethyl silicon oil, and 1,3-benzenediol is carbon source, ferrocene is the metal source and catalyst to form coated carbon layers. The mechanism to synthesis CEMHNs by in situ reduction through Kirkendall effect was elucidated, based on different synthesis parameters and stages, we also prepared carbon-encapsulated metal oxide nanoparticles, carbon-encapsulated Fe3Si nanoparticles and multi-walled carbon nanotubes. The morphology, Structure and composition of the products above mentioned were characterized by TEM, HREM, XRD, SEM, and EDX measurements, these analysis and measurements were helpful to explain the impact of dimethyl silicon oil in reaction, the mechanism to synthesize product of every stage, and to establish theoretical model.The results show that carbon-encapsulated Fe hollow nanoparticles were obtained by co-pyrolysis of 1,3-benzenediol and ferrocene in dimethyl silicon oil, and the range of CEMHNs particle size distribution is from 20nm to 60nm with distinctive hollow-core structure, and the shell of hollow nanoparticles were constituted by carbon/Fe composite. Besides, carbon-encapsulated Fe3O4 nanoparticles (Fe3O4@C) and half hollow structure nanoparticles which exist gaps between core and shell substance were prepared based on different reduction time. Fe3O4@C nanopartiches size distribution is from 30nm to 60nm, there is not distinctive boundary between carbon shell and Fe3O4 interfaces. The formation of hollow structure is based on diffusion principle of two different phases-no gap between Fe3O4 core and carbon shell in the first generated precursor Fe3O4@C, with in situ reduction time prolonging, reaction product Fe posses different diffusion rate with Fe3O4, inequality diffusion lead to formation of vacant position, and vacant position accumulated to form hollow structure at last. The roles of liquid silicone played in reactions can be concluded as follows:First, silicone oil is high viscosity, which play the role is similar as colloidal to prevent the gathering of nanoparticles synthesized in the early stage of reaction, and to avoid and size distribution uneven caused by local heating; Second, Liquid reaction medium make materials be heated uniformly, effectively prevented that the morphology of product at specific stage is different caused by uneven heating.The preparation of carbon-encapsulated Fe3Si nanoparticles (Fe3Si@C) accomplished by pyrolysis ferrocene in dimethyl silicon oil, and dimethyl silicon oil is not only reaction medium but also silicon source in this reaction. Fe3Si@C nanopartiches size distribution is from 40nm to 80nm, there is not distinctive boundary between carbon shell and Fe3Si core interfaces. Catalysis of Fe3Si is worse to form coated graphite carbon layers, it can be concluded that Fe3Si nanopartiches posses excellent acid corrosion resistance by HCl reaction with different forms of Fe in products.The preparation of multi-walled carbon nanotubes(MWCNTs) was by co-pyrolysis 1,3-benzenediol and ferrocene in dimethyl silicon oil at 420℃, and maintained at a lower constant pressure within the system. The morphology, Structure and composition of different length MWCNTs were characterized and analysed, explained the reasons for different products with different pressure and formation mechanism of MWCNTs.