Authors: C-J Su, L-S Hsu, T-W. Wu, C-J Liu and S-H Lin
Affilation: Chung Shan Medical University, Taiwan
Pages: 13 - 16
Keywords: spiral carbon nanofibers, Pd metal cluster
The spiral carbon nanofibers consisting of Pd metal cluster were grown by the Pd2(dba)3-catalyzed decomposition of gaseous acetylene on molecular sieves (Linde 13X) support. The microstructure and composition of the spiral carbon nanofibers were characterized by transmission electron microscope (TEM) and selective area diffraction (SAD). Besides the irregularly curved carbon nanotubes, the TEM image shown in Fig. 1 clearly displays two types of spiral structure of the carbon nanofibers, which are distinguished according to their pitch (p) to diameter (2r) ratio, or equivalently, the pitch angle of the helix, j=arctan(p/2pr).1,2 The p and 2r values of a typical type I nanofiber in Fig. 1 are found to be roughly 140 and 70 nm, respectively, which leads to j=32°. Most of the helices observed belong to type I nanofibers. A typical type II nanofiber has p and 2r values of about 110 and 27 nm, respectively, which leads to a large pitch angle (j=52°). The SAD data show that the black spots inside the carbon nanofibers in Fig. 1 are palladium metal (not PdO) clusters of diameters 40-60 nm. This is the fist incorporation of Pd nanoparticles inside carbon nanofibers. These Pd metal clusters show a small hysteresis from magnetization vs. magnetic field data and metallic behavior from resistivity measurement. They will also be studied by synchrotron-radiation-excited photoemission and photoabsorption experiments.
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