2588 Journal of the American Ceramic Sociery--Seo et al VoL. 83. No. 10 o985 20 (b) 405 紧 Fig 9.(a) TEM image and(b)and(c) HREM images of type C whisker synthesized from the stacked powder at 1420.C for 0. I h. Insets in Figs. 9(b)and (c) schematically depict the lattice configuration of each arrangement Also, the synthesis of sic powder under vacuum was attempted,(2) Whisker-Growth Direction and Insertion Direction of sing a mixture of CB and Sio as shown in Fig. l(e). The Stacking Faults Sic content synthesized under m was of the sic content that was synthesized in hydrogen-gas atmosphere. The Figure 6 shows TEM micrographs and electron diffraction synthesized powders composed primarily of angular particles patterns of the three different whiskers, each aligned with the with various facets, whereas whiskers rarely were observed, as electron beam parallel to(1 10)zone axis. The type A whisker(Fig shown in Fig. 5. Their synthesis reaction probably is caused by 6(a) has a relatively flat surface and the stacking-fault planes are direct reaction of the CB and SiO,(solid-solid reaction), indepen- perpendicular to the growth direction. The type B whisker(Fig dent of the gas component. the main whisker formatio 6(b)) has a rough surface and the stacking-fault planes are inclined mechanism in the SiO2-carbon-hydrogen-gas system was solid- 35, relative to the growth direction. The type C whisker(Fig. 6(c) gas reaction between Sio and CB, such as that described in has a rough sawtooth surface and the stacking faults exist concur. reaction(2), and their grow dependent closely on their rently in three different (111) planes. Type a and type B whiskers preparation conditions, such as Sio generation and the stacking were synthesized from the mixed powder, and type C whisker was manner of CB synthesized from the stacked powder at a temperature of 1420CAlso, the synthesis of SiC powder under vacuum was attempted, using a mixture of CB and SiO2 powder, as shown in Fig. 1(e). The SiC content synthesized under vacuum was ;1⁄20 of the SiC content that was synthesized in hydrogen-gas atmosphere. The synthesized powders were composed primarily of angular particles with various facets, whereas whiskers rarely were observed, as shown in Fig. 5. Their synthesis reaction probably is caused by direct reaction of the CB and SiO2 (solid–solid reaction), indepen￾dent of the gas component.16 Thus, the main whisker formation mechanism in the SiO2–carbon–hydrogen-gas system was solid– gas reaction between SiO and CB, such as that described in reaction (2), and their growth was dependent closely on their preparation conditions, such as SiO generation and the stacking manner of CB. (2) Whisker-Growth Direction and Insertion Direction of Stacking Faults Figure 6 shows TEM micrographs and electron diffraction patterns of the three different whiskers, each aligned with the electron beam parallel to ^110& zone axis. The type A whisker (Fig. 6(a)) has a relatively flat surface and the stacking-fault planes are perpendicular to the growth direction. The type B whisker (Fig. 6(b)) has a rough surface and the stacking-fault planes are inclined 35°, relative to the growth direction. The type C whisker (Fig. 6(c)) has a rough sawtooth surface and the stacking faults exist concur￾rently in three different {111} planes. Type A and type B whiskers were synthesized from the mixed powder, and type C whisker was synthesized from the stacked powder at a temperature of 1420°C Fig. 9. (a) TEM image and (b) and (c) HREM images of type C whisker synthesized from the stacked powder at 1420°C for 0.1 h. Insets in Figs. 9(b) and (c) schematically depict the lattice configuration of each arrangement. 2588 Journal of the American Ceramic Society—Seo et al. Vol. 83, No. 10