Fe-encapsulating carbon nano onionlike fullerenes from heavy oil residue
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Xuguang Liu Key Laboratory of Interface Science and Engineering in Advanced Materials (Taiyuan University of Technology), Ministry of Education, Taiyuan 030024, China; and College of Chemistry and Chemical Engineering, Taiyuan University of Technology, Taiyuan 030024, China
Bingshe Xua) Key Laboratory of Interface Science and Engineering in Advanced Materials (Taiyuan University of Technology), Ministry of Education, Taiyuan 030024, China; and College of Materials Science and Engineering, Taiyuan University of Technology, Taiyuan 030024, China (Received 18 August 2007; accepted 7 February 2008)
Fe-encapsulating carbon nano onionlike fullerenes (NOLFs) were obtained by chemical vapor deposition (CVD) using heavy oil residue as carbon source and ferrocene as catalyst precursor in an argon flow of 150 mL/min at 900 °C for 30 min. Field-emission scanning electron microscopy (FE-SEM), high-resolution transmission electron microscopy (HRTEM), energy-dispersive spectroscopy (EDS), x-ray diffraction (XRD), and Raman spectroscopy were used to characterize morphology and microstructure of the products. The results show that Fe-encapsulating NOLFs collected at the outlet zone of quartz tube had core/shell structures with sizes ranging from 3 to 6 nm and outer shells composed of poorly crystallized graphitic layers. Their growth followed particle self-assembling growth mechanism, and all atoms in the graphite sheets primarily arose from Fe-carbide nanoparticles.
I. INTRODUCTION
Since the establishment of the method for the preparation of fullerenes in macroscopic quantities by Krätschmer et al.,1 the novel spherical carbon material, nano onionlike fullerenes (NOLFs), has attracted widespread attention in the materials science community. Metal-encapsulating NOLFs have potential application in many fields such as magnetic data storage, xerography, and magnetic resonance imaging.2 At present, metal-encapsulating NOLFs have been prepared by various techniques, such as electron irradiation,3 arc discharge,4 plasma,5 explosive decomposition of organometal,6 and chemical vapor deposition (CVD).7 Among these methods, CVD appears promising because of its relatively low cost and potentially high yield.7 Heavy oil residue, a by-product of petroleum processing, is a black solid mixture consisting of many kinds of hydrocarbons and their derivatives. The use of heavy a)
Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/JMR.2008.0174 J. Mater. Res., Vol. 23, No. 5, May 2008
http://journals.cambridge.org
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oil residue is restricted by its high softening point, heavy average molecular weight, high condensed aromatics content, high density, low H/C atom ratio (1.16–1.39), high carbon residue (35.8%–54.6%), and high content of heavy metal and heteroatoms such as S and N. Heavy oil residue creates fatal effects on catalytic transformation, hydrocracking, and even environment. However, heavy oil residue would have a positive contribution when considered as a feedstock for carbon mate
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