C. Kawai A yamakawa 4 CONCLUSION (a) Thin liquid phase Gas species Si3 N4 whiskers were coated on a-Si3N4 whisker 幸￥YL1 seeds, on which Sioz-Al2O3 Y2O3 oxides were coated, through a VLS mechanism using gas spe Substrate Li Whiskers cies generated by reacting amorphous Si3N4 and TiO2 as source powders. With a thin oxide layer, (b) Thick liquid phase the coated whiskers were fine-grained and had no Gras species droplets on the tips of the whiskers. with a thick oxide layer, the coated whiskers consisted of short whiskers with droplets and long whiskers with no Whiskers droplets. These results indicated that the whisker Nucleation Crystal growt growth proceeded through a vls mechanism. the (Initial stage) (Final stage differences in morphology were considered to be caused by difference in thickness of the resulting Fig. 4. The comparison of whisker growth mechanisms; (a) liquid layer on the seeds hin oxide layer,(b) thick oxide layer. REFERENCES short and have no droplets, and are in the final stage of whisker growth [Fig 4(a) 1. WANG, M. J.& wADA, H, Mater. Sci. Forum, 47 With a thick oxide layer, however, the droplet (1989)267-281 2. WANG, M.J.& WADA, H.,J. Mater. Sci. 25(1990) are easy not to consume, since large droplets are 1690-1698 probably formed on the tips of whiskers due to the 3. HAYASHI, T. KAWABE, S. SArto,H, Yogyo. thick oxide layer. Therefore, whisker growth is Kyokai-shi, 94 (1986)29-30 continued for a long time and is finished when the 4. SAItO. H. hAYaSHI, t.& MiurA, K.,J. Che Soc.Jpn,9(1981)1371-1377 droplets are entirely consumed This results in the 5. BL, Y, YU, Z& ZHANG, P, Science of sintering growth of long whiskers having no droplets. On (1991)334 the other hand, relatively short whiskers having 6. KAWAL, C& YAMAKAWA, A,, J. Am. Ceram. Soc. 79(196)57-58 droplets are also seen with the long whiskers. They KAWAL C.& YAMAKAWA,J Mater. Sci. Lett. 14 probably start to grow after a considerably long (1995)192-193 duration; the liquid laycr remains on the substrate 8. LEVIN. E.M., ROBBINS. C. R& McMURDIE, H. F. Phase Diagram for Ceramists 1969 Supplement. Am. even though most of it is consumed in the growth Ceram Soc., Columbus, oH, 1969, p. 165 The short whisk 9. KATOH, N, Kessyo-Kohgaku-Ilandbook M. Yama an initial stage of whisker growth and have possl- moto kyoritsu-Shuppan, Tokyo, 1911,p.218 OMO. M.. In Chikkakeiso-Ceramics, ed. s. Soh- bility of further elongation with the increase in miya, M. Yoshimura M. Mitomo Uchida-Rokakuho, duration [Fig. 4(b)] Tokyo, 1987, pp. 1-8138 C. Kawai, A. Yamakawa 4 CONCLUSION (a) Thin liquid phase (b) Thick liquid phase Gas species Finished Nucleation whiskers In giowing Crystal growth (Initial stage) (Final stage) Fig. 4. The comparison of whisker growth mechanisms; (a) thin oxide layer, (b) thick oxide layer. short and have no droplets, and are in the final stage of whisker growth [Fig. 4(a)]. With a thick oxide layer, however, the droplets are easy not to consume, since large droplets are probably formed on the tips of whiskers due to the thick oxide layer. Therefore, whisker growth is continued for a long time and is finished when the droplets are entirely consumed. This results in the growth of long whiskers having no droplets. On the other hand, relatively short whiskers having droplets are also seen with the long whiskers. They probably start to grow after a considerably long duration; the liquid layer remains on the substrate even though most of it is consumed in the growth of many long whiskers. The short whiskers are in an initial stage of whisker growth and have possi￾bility of further elongation with the increase in duration [Fig. 4(b)]. S&N4 whiskers were coated on a-S&N4 whisker seeds, on which SiO2--Al#-Y203 oxides were coated, through a VLS mechanism using gas spe￾cies generated by reacting amorphous S&N4 and Ti02 as source powders. With a thin oxide layer, the coated whiskers were fine-grained and had no droplets on the tips of the whiskers. With a thick oxide layer, the coated whiskers consisted of short whiskers with droplets and long whiskers with no droplets. These results indicated that the whisker growth proceeded through a VLS mechanism. The differences in molphology were considered to be caused by difference in thickness of the resulting liquid layer on the seeds. REFERENCES 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. WANG, M. J. & WADA, H., Mater. Sci. Forum, 41 (1989) 267-281. WANG, M. J. & WADA, H., J. Mater. Sci., 25 (1990) 1690-1698. HAYASHI, T., KAWABE, S. & SAITO, H., Yogyo￾Kyokai-shi, 94 (1986) 29-30. SAITO, H., HAYASHI, T. & MIURA, K., J. Chem. Sot. Jpn, 9 (1981) 1371-1377. BI, Y., YU, Z. & ZHANG, P., Science of Sintering, 23 (1991) 3340. KAWAI, C. & YAMAKAWA, A., J. Am. Ceram. Sot., 79 (1996) 57-58. KAWAI, C. & YAMAKAWA, J. Mater. Sci. Lett., 14 (1995) 192-193. LEVIN, E. M., ROBBINS, C. R. & McMURDIE, H. F., Phase Diagram for Ceramists 1969 Supplement. Am. Ceram. Sot., Columbus, OH, 1969, p. 165. KATOH, N., Kessyo-Kohgaku-Handbook. M. Yama￾moto Kyoritsu-Shuppan, Tokyo, 1971, p. 218. MITOMO, M., In Chikkakeiso-Ceramics, ed. S. Soh￾miya, M. Yoshimura & M. Mitomo. Uchida-Rokakuho, Tokyo, 1987, pp. l-8