Journal of the American Ceramic Sociery- VoL. 83. No. 10 (109.5 90° (109.5 0253)"1 1135 90 111 69G0N 12589 Fig. 11. TEM micrographs of a Y-shaped whisker synthesized from powder mixtures at 1420C for 0.5 h based on the right portion of the leg and the right nification view and(b)tilted to a( 110)direction( toward the (111)direction); Fig. 1I(c) shows the left portion of the nd the left head (toward the(11l)direction). Insets in Figs. I l()and(c)show the corresponding on diffraction patterns each set of stacking-fault layers ( Fig. 6(c)). The angles between the axis. Whiskers that were deflected at angles of 125and 70, and stacking-fault planes in the center and those in small portions on the right side of the whisker or those on the left side of the whisker heated at a temperature of 1420.C for 0.5 h, as shown in Figs. vere similar(-109o). To explain this result, HREM observation of type C whisker that was synthesized from CB/SiO2 stacked an angle of 109 also was formed from the stacked powder that powder at a temperature of 1420C for 0 I h was conducted, as was heated at 1420 C for 3 h(see Fig. 10(c). Whisker that was shown in Fig. 9. B-SiC belongs to the face-centered cubic(fcc) deflected at an angle of 125 was composed of two parts: type a ystem and has four equivalent (1ll) planes. If the primary whisker as a common type, as shown on the left side of Fig. 10(a), growth plane of type C whisker is(111)and the whisker is and type B whisker, which had a stacking fault that was inclined observed with the electron beam aligned parallel to the(110) at an angle of 35. to the growth direction, as shown on the right direction, as shown in Fig. 9, only the(lll)and (111) planes can side. Their thickness rarely changed, relative to the whisker type be observed, because the planes that are perpendicular to the( 110) For flat whiskers, however, the radius of type B whisker normally direction are inclined at an angle of 109.5 relative to each other. was smaller than that of type A whisker, as mentioned in section On the other hand. because the whiskers that were formed via 1(2). Thus, the whisker probably does not interlink different types carbothermal reduction had many twin faults, the twin (lily plane of whiskers but is grown as one whisker via the growth of different of the original(lID) plane could exist in the whisker. +, Thus, stacking planes. The growth front of the whisker that was deflected (111)and(111) planes that are perpendicular to the(110) at an angle of 125. probably starts from the end side of a type b direction appear in type C whisker, and the angle between them whisker(see the top side of Fig. 10(a)). Near the enriched carbon also is70.5°(1800-109.5°. The regions labeled“A"and"B"in Fig 9 clearly have a twin relation with each other, in the direction source, which is an agglomerated lump of carbon, the type B perpendicular to the growth direction of the whisker whisker has grown rapidly by stacking the(1l 1) planes inclined at an angle of 35, relative to the growth direction. The growth planes and growth directions are related closely to the surrounding growth (3) Whisker Branching conditions, such as differences in the growth rate, the content of Figures 10 and 1 l show TEM micrographs of the four deflected the inserted stacking faults, and the supply of carbon and sio whiskers, aligned with the electron beam paral the(110)zone source. Under a constant supersaturation of Sio gas, the growtheach set of stacking-fault layers (Fig. 6(c)). The angles between the stacking-fault planes in the center and those in small portions on the right side of the whisker or those on the left side of the whisker were similar (;109°). To explain this result, HREM observation of type C whisker that was synthesized from CB/SiO2 stacked powder at a temperature of 1420°C for 0.1 h was conducted, as shown in Fig. 9. b-SiC belongs to the face-centered cubic (fcc) system and has four equivalent {111} planes. If the primary growth plane of type C whisker is (111) and the whisker is observed with the electron beam aligned parallel to the ^110& direction, as shown in Fig. 9, only the (111) and (111#) planes can be observed, because the planes that are perpendicular to the ^110& direction are inclined at an angle of 109.5°, relative to each other. On the other hand, because the whiskers that were formed via carbothermal reduction had many twin faults, the twin (111)9 plane of the original (111) plane could exist in the whisker.13,14,21 Thus, (111)9 and (1#11#)9 planes that are perpendicular to the ^110& direction appear in type C whisker, and the angle between them also is 70.5° (180° 2 109.5°). The regions labeled “A” and “B” in Fig. 9 clearly have a twin relation with each other, in the direction perpendicular to the growth direction of the whisker. (3) Whisker Branching Figures 10 and 11 show TEM micrographs of the four deflected whiskers, aligned with the electron beam parallel to the ^110& zone axis. Whiskers that were deflected at angles of 125° and 70°, and Y-shaped whiskers, were formed from the mixed powder that was heated at a temperature of 1420°C for 0.5 h, as shown in Figs. 10(a), 10(b), and 11, respectively. A whisker that was branched at an angle of 109° also was formed from the stacked powder that was heated at 1420°C for 3 h (see Fig. 10(c)). Whisker that was deflected at an angle of 125° was composed of two parts: type A whisker as a common type, as shown on the left side of Fig. 10(a), and type B whisker, which had a stacking fault that was inclined at an angle of 35° to the growth direction, as shown on the right side. Their thickness rarely changed, relative to the whisker type. For flat whiskers, however, the radius of type B whisker normally was smaller than that of type A whisker, as mentioned in section III(2). Thus, the whisker probably does not interlink different types of whiskers but is grown as one whisker via the growth of different stacking planes. The growth front of the whisker that was deflected at an angle of 125° probably starts from the end side of a type B whisker (see the top side of Fig. 10(a)). Near the enriched carbon source, which is an agglomerated lump of carbon, the type B whisker has grown rapidly by stacking the (111#) planes inclined at an angle of 35°, relative to the growth direction. The growth planes and growth directions are related closely to the surrounding growth conditions, such as differences in the growth rate, the content of the inserted stacking faults, and the supply of carbon and SiO source. Under a constant supersaturation of SiO gas, the growth Fig. 11. TEM micrographs of a Y-shaped whisker synthesized from powder mixtures at 1420°C for 0.5 h based on the right portion of the leg and the right head ((a) low-magnification view and (b) tilted to a ^110& direction (toward the ^111& direction)); Fig. 11(c) shows the left portion of the leg and the left head (toward the ^111& direction). Insets in Figs. 11(b) and (c) show the corresponding electron diffraction patterns. 2590 Journal of the American Ceramic Society—Seo et al. Vol. 83, No. 10