H.J. Choi, J--G. Lee/ Ceramics International 26(2000)7-12 5 Hm Fig 4. BF images [(a) and(c), and Sad patterns [(b)and (d) of the VlssCW. than 0. 2 um were grown on the substrate [Fig. 1(a showed heavy stacking faults along the entire whisker Sic whiskers grown in the rice-hulls batch were length, which was evidenced by the contrast bands in observed in a wide variation of the diameters within the the bF image and streaks in the Sad pattern. Fig range of less that 0.6 um [Fig. 1(b)]. It may be due to the shows the BF image and SAD patterns of Sic whiskers gradual decrease of the Sio generation rate with time in grown in the rice-hulls batch. Some whiskers showed the rice-hulls batch. Generally, the diameter of Sic alternating section without stacking faults [ marked A in whiskers is decreased with increasing Sio generation Fig. 3(a)] and with heavy stacking faults [marked B in rate [10). The VLSSCW that was grown by using the Fe Fig. 3(a). The Sad patterns of sections A and b also powder was thick with the diameters of 2-8 um showed, respectively, no stacking faults and heavy [Fig. I(c)]. Liquid droplets at the end of the whiskers. stacking faults [Fig. 3(b)and(c)]. It was inferred that which are typical for the VLS mechanism [6, 10-13, 17]. these whiskers are the vSSCw [6]. The other whiskers were found in the VLSSCW. All whiskers in this study showed Moire patterns [marked C in Fig 3(a)], which were identified as cubic 3C SiC(B-phase) by XRD. The was the evidence of the presence of dislocations and intensity ratio of the XRD peak at 33.6 and 41.4, 133.6/ stacking faults in the whiskers [14]. Therefore, it 1414, of the vSSCw, tssCw and vlssCw were 2.8 believed that the vsscw and tsscw were simulta- 0l and 0.1l, respectively (Table 1). The intensity ratio neously grown in the rice-hulls. Fig. 4 shows the BF increased with contents of stacking faults [7, 17]. The images and SAD patterns of VLSSCW. The VLSSCW RD results indicated that there are heavy stacking with a diameter of about 2 um showed no contrast band faults in the VSSCW and little stacking faults in the in the BF image[Fig 4(a)] and streaks in the Sad pat Ⅴ LSSCV tern [Fig. 4(b)]. Other VLSSCW with a diameter of The bright field(BF) image [Fig. 2(a)] and selected about 7 um showed contrast bands in the narrow region area diffraction(SAD) pattern[Fig. 2(b)] of the VSSCw indicated by the arrow in Fig. 4(c)that indicates thethan 0.2 mm were grown on the substrate [Fig. 1 (a)]. SiC whiskers grown in the rice-hulls batch were observed in a wide variation of the diameters within the range of less that 0.6 mm [Fig. 1(b)]. It may be due to the gradual decrease of the SiO generation rate with time in the rice-hulls batch. Generally, the diameter of SiC whiskers is decreased with increasing SiO generation rate [10]. The VLSSCW that was grown by using the Fe powder was thick with the diameters of 2±8 mm [Fig. 1(c)]. Liquid droplets at the end of the whiskers, which are typical for the VLS mechanism [6,10±13,17], were found in the VLSSCW. All whiskers in this study were identi®ed as cubic 3C SiC (-phase) by XRD. The intensity ratio of the XRD peak at 33.6 and 41.4, I33.6/ I41.4, of the VSSCW, TSSCW and VLSSCW were 2.83, 1.01 and 0.11, respectively (Table 1). The intensity ratio increased with contents of stacking faults [7,17]. The XRD results indicated that there are heavy stacking faults in the VSSCW and little stacking faults in the VLSSCW. The bright ®eld (BF) image [Fig. 2(a)] and selected area di€raction (SAD) pattern [Fig. 2(b)] of the VSSCW showed heavy stacking faults along the entire whisker length, which was evidenced by the contrast bands in the BF image and streaks in the SAD pattern. Fig. 3 shows the BF image and SAD patterns of SiC whiskers grown in the rice-hulls batch. Some whiskers showed alternating section without stacking faults [marked A in Fig. 3(a)] and with heavy stacking faults [marked B in Fig. 3(a)]. The SAD patterns of sections A and B also showed, respectively, no stacking faults and heavy stacking faults [Fig. 3(b) and (c)]. It was inferred that these whiskers are the VSSCW [6]. The other whiskers showed Moire patterns [marked C in Fig. 3 (a)], which was the evidence of the presence of dislocations and stacking faults in the whiskers [14]. Therefore, it is believed that the VSSCW and TSSCW were simulta￾neously grown in the rice-hulls. Fig. 4 shows the BF images and SAD patterns of VLSSCW. The VLSSCW with a diameter of about 2 mm showed no contrast band in the BF image [Fig. 4(a)] and streaks in the SAD pat￾tern [Fig. 4(b)]. Other VLSSCW with a diameter of about 7 mm showed contrast bands in the narrow region indicated by the arrow in Fig. 4(c) that indicates the Fig. 4. BF images [(a) and (c)], and SAD patterns [(b) and (d)] of the VLSSCW. 10 H.-J. Choi, J.-G. Lee / Ceramics International 26 (2000) 7±12