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Some carbon fibers synthesized by the author [2, 3] and his research group from camphor under different but specific conditions are shown in Figure 1.4. These are grown by chemical vapor deposition technique. It is observed that though precursor was the same, i.e., camphor, by altering the nature and form of catalyst, carbon fibers of different morphologies are obtained. For this growth, nickel in different forms was used as a catalyst. Nickel plate, cleaned by acid followed by acetone, gave carbon fiber as shown in Figure 1.4a. When the top surface of nickel was oxidized and then cleaned, it gave carbon fiber as shown in Figure 1.4b. It grew from one point on the catalyst surface in a cauliflower-like shape. In another experiment, camphor was pyrolyzed without using any catalyst. Under this condition, plate type (cactus type) carbon fiber was obtained (Figure 1.4c). These fibers also contained some small beads attached to the fiber. In one experiment nickel powder of size 20 nm spread over nickel plate was used. Under this condition, branched carbon fiber as shown in Figure 1.4d was obtained, with Ni catalyst sitting at the center. Vapor-grown carbon fibers (VGCFs) (Figure 1.4e) were obtained by pyrolysis on the Ni coated quartz substrate. All these experiments were carried out under argon atmosphere at temperature 750 °C.

Figure 1.4 SEM images of carbon fibers (CF) synthesized from camphor as precursors by pyrolyzing them at 700 °C in presence of argon under varying conditions: (a) Long tubelike CF over nickel plate, (b) cauliflower-like CF over oxidized nickel plate, (c) CF grown without using any catalyst, (d) branched carbon fibers obtained at temperature 750 °C, with Ni sitting at the center, and (e) VGCFs obtained by pyrolysis on the Ni coated quartz substrate (Source: Debabrata Pradhan, 2003) [4].