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Synthesis and Characterization of Cobalt-Carbon Core-Shell Microspheres in Supercritical Carbon Dioxide System
?Jun-song Yang ,Qian-wang Chen*
Author NameAffiliationE-mail
?Jun-song Yang Hefei National Laboratory for Physical Sciences at Microscale, Department of Materials Science and Engineering, Department of Chemistry, University of Science and Technology of China, Hefei 230026, China  
Qian-wang Chen* Hefei National Laboratory for Physical Sciences at Microscale, Department of Materials Science and Engineering, Department of Chemistry, University of Science and Technology of China, Hefei 230026, China cqw@ustc.edu.cn 
Abstract:
The synthesis of cobalt-carbon core-shell microspheres in supercritical carbon dioxide system was investigated. Cobalt-carbon core-shell microspheres with diameter of about 1 μm were prepared at 350 oC for 12 h in a closed vessel containing an appropriate amount of bis(cyclopentadienyl)cobalt powder and dry ice. Characterization by a variety of techniques, including X-ray powder diffraction, X-ray photoelectron spectroscopy, Transmission electron microscope, Fourier transform infrared spectrum and Raman spectroscopy analysis reveals that each cobalt-carbon core-shell microsphere is made up of an amorphous cobalt core with diameter less than 1 μm and an amorphous carbon shell with thickness of about 200 nm. The possible growth mechanism of cobalt-carbon core-shell microspheres is discussed, based on the pyrolysis of bis(cyclopentadienyl)cobalt in supercritical carbon dioxide and the deposition of carbon or carbon clusters with odd electrons on the surface of magnetic cobalt cores due to magnetic attraction. Magnetic measurements show 141.41 emu/g of saturation magnetization of a typical sample, which is lower than the 168 emu/g of the corresponding metal cobalt bulk material. This is attributed to the considerable mass of the carbon shell and amorphous nature of the magnetic core. Control of magnetism in the cobalt-carbon core-shell microspheres was achieved by annealing treatments.
Key words:  Cobalt-carbon core-shell microspheres, Supercritical carbon dioxide system
FundProject:国家自然科学基金
Synthesis and Characterization of Cobalt-Carbon Core-Shell Microspheres in Supercritical Carbon Dioxide System
杨俊松,陈乾旺*
摘要:
研究了钴碳核壳微球在超临界二氧化碳体系中的合成过程. 在密闭的不锈钢高压反应釜中,适量的二茂钴和干冰在350 oC下,反应12 h后合成直径大约1 μm的钴碳核壳微球。通过X射线衍射、X射线光电子谱、透射电子显微镜、傅利叶红外光谱(FT-IR)以及拉曼光谱的分析,钴碳核壳微球是由直径小于1 μm的非晶钴核和厚度约为200 nm的非晶碳壳组成. 其生长机理可能是:二茂钴在超临界二氧化碳体系中的热分解,带单电子的碳原子或基团由于磁性作用沉积在磁性的钴核上. 由于非晶碳壳的存在,钴碳核壳微球的磁饱和强度141.
关键词:  钴-碳核壳微球,超临界二氧化碳体系
DOI:10.1088/1674-0068/21/01/76-80
分类号: