Chen et al. SBE-��-CD cost [26] reported that carbon nanocoils with twisting form were grown by the Ni/Al2O3-catalyzed pyrolysis of acetylene. Ni particles supported on fine Al2O3 powders were prepared by an impregnation method using Ni(NO3)2 as a precursor and was used as the catalyst in their research. It is obvious that the Ni fine particles disperse well during the growth of carbon fiber due to Ni-supporter interaction in Ni/Al2O3. Though Ni catalyst nanoparticle of about 90 nm can be obtained by the induction of Ni(OH)2 clusters insulated by PVP, those Ni nanoparticles tend

to aggregate and grow into larger Ni powder of about 600 nm because of their high surface energy and temperature action. Once the relatively large Ni powder forms, it develops gradually into regular Ni powder with catalytic anisotropy, and double helical carbon fiber begins to grow on catalyst particle. The corresponding mechanism is well visualized in Figure 7. The above analysis suggests that the parameters of carbon coil, such as fiber diameter, coil pitch and gap, are in control using suitable Ni particle. Figure 7 Scheme of corresponding mechanisms of nickel formation and growth of coiled carbon fiber. Conclusions By controlling the reaction temperature and NaOH concentration, Ni nanoparticles with designed size can be obtained by reduction of nickel sulfate LY411575 chemical structure with hydrazine

hydrate employing the Selleck Epacadostat surfactant of PVP. Ni nanoparticles of about 90 nm were obtained at 70°C when the molar concentration of NaOH solution was 0.8 M.

The as-prepared Ni nanoparticles Dipeptidyl peptidase of about 90 nm contain some ultra small crystals less than 50 nm, and they are effective for catalytic growth of CCFs. The diameter of coiled carbon fibers is remarkably larger than that of the Ni particle catalysts. It was proposed that the aggregation and shape changes occurred during the growth of coiled carbon fiber, and the morphology of carbon helix can be adjusted by choosing the proper substrate of Ni catalyst. Acknowledgements This work was financially supported by the National Natural Science Foundation of China (No. 51173148 and No. 51202228), the Special Research Fund for Doctoral Program of Higher Education (No. 20060613004), the 2011 Doctoral Innovation Funds of Southwest Jiaotong University, the Fundamental Research Funds for the Central Universities (No. 2010XS31), and the scientific research expenses Foundation (for new teachers) of University of Electronic Science and Technology of China (No. Y02002012001007). References 1. Motojima S, Kawaguchi M, Nozaki K, Iwanaga H: Growth of regularly coiled carbon filaments by Ni catalyzed pyrolysis of acetylene, and their morphology and extension characteristics. Appl Phys Lett 1990, 56:321–323.CrossRef 2. Motojima S, Hoshiya S, Hishikawa Y: Electromagnetic wave absorption properties of carbon microcoils/PMMA composite beads in W bands. Carbon 2003, 41:2658–2660.CrossRef 3.