JOURNALOF CRYSTAL GROWTH ELSEVIER Journal of Crystal Growth 193(1998)585-591 The effect of vapor phase on the growth of TiC whiskers prepared by chemical vapor deposition Yongwen Yuan" D, * Jinsheng Pan Received 15 April 1998; accepted 15 May 1998 Abstract Quality TiC whiskers with high yield are prepared by a modified chemical vapor deposition(CVD) method. The The effect of vapor phase on the whisker morphology at fixed temperature s studied in detail. It is found that the morphology and size of Tic whiskers are significantly affected by both the flow rate of vapor phase and the C/Tiratio. The C/Tieffect is supposed to be related to the formation of Ni-Ti eutectic liquid phase according to the vapor-liquid-solid (vls)mechanism which is confirmed in this experiment. It is also found that the morphologies of Tic deposits are different at different locations of the substrate depending on the variation of the ontacting time and axial effective concentration of vapor phase along the vertical reaction tube. The high whisker yield is closely related to the movement of the vapor phase. A fast vapor fluid spouting upwards and diverging into the annulus makes the radial concentration of the vapor phase more homogeneous, and it also increases the collision of the vapor species on to the growing fronts and accelerates the mass transition of the Cvd process. c 1998 Elsevier Science B v. All rights reserved PACS:68.70.+w;81.15Gh;81.20.Lb Keywords: TiC whiskers; Chemical vapor deposition; VLS mechanism 1. Introduction is to toughen the brittle ceramic matrix. the re- quired properties of the whiskers for use in CMC Ceramic whiskers are now being used in the are their size and morphology, the compatibility composites for reinforcing and toughening the with matrix materials and the interfacial bonding metal matrix composites(MMC) and ceramic between matrix and whiskers. So far, the cerami matrix composites(CMC)[1, 2]. In ceramic matrix whiskers in use are mainly Sic and Si3N4. How- composites( CMC), the main effect of the whiskers ever, the newly developed Tic whisker has much higher strength, especially high-temperature strength. and corrosion resistance thermal and Corresponding author. Fax: +86 10 62771160 electrical properties, as well as better compatibility 0022-0248/98/-see front matter@ 1998 Elsevier Science B V. All rights reserved PI:S0022-0248(98)00484-9Journal of Crystal Growth 193 (1998) 585—591 The effect of vapor phase on the growth of TiC whiskers prepared by chemical vapor deposition Yongwen Yuan!,",*, Jinsheng Pan!," ! Laboratory of Advanced Materials, Tsinghua University, Beijing 100084, People+s Republic of China " Department of Materials Science and Engineering, Tsinghua University, Beijing 100084, People+s Republic of China Received 15 April 1998; accepted 15 May 1998 Abstract Quality TiC whiskers with high yield are prepared by a modified chemical vapor deposition (CVD) method. The appropriate deposition parameters are found. The effect of vapor phase on the whisker morphology at fixed temperature is studied in detail. It is found that the morphology and size of TiC whiskers are significantly affected by both the flow rate of vapor phase and the C/Ti ratio. The C/Ti effect is supposed to be related to the formation of Ni—Ti eutectic liquid phase according to the vapor—liquid—solid (VLS) mechanism which is confirmed in this experiment. It is also found that the morphologies of TiC deposits are different at different locations of the substrate depending on the variation of the contacting time and axial effective concentration of vapor phase along the vertical reaction tube. The high whisker yield is closely related to the movement of the vapor phase. A fast vapor fluid spouting upwards and diverging into the annulus makes the radial concentration of the vapor phase more homogeneous, and it also increases the collision of the vapor species on to the growing fronts and accelerates the mass transition of the CVD process. ( 1998 Elsevier Science B.V. All rights reserved. PACS: 68.70.#w; 81.15.Gh; 81.20.Lb Keywords: TiC whiskers; Chemical vapor deposition; VLS mechanism 1. Introduction Ceramic whiskers are now being used in the composites for reinforcing and toughening the metal matrix composites (MMC) and ceramic matrix composites (CMC) [1,2]. In ceramic matrix composites (CMC), the main effect of the whiskers * Corresponding author. Fax: #86 10 62771160. is to toughen the brittle ceramic matrix. The re￾quired properties of the whiskers for use in CMC are their size and morphology, the compatibility with matrix materials and the interfacial bonding between matrix and whiskers. So far, the ceramic whiskers in use are mainly SiC and Si3 N4 . How￾ever, the newly developed TiC whisker has much higher strength, especially high-temperature strength, and corrosion resistance, thermal and electrical properties, as well as better compatibility 0022-0248/98/$ — see front matter ( 1998 Elsevier Science B.V. All rights reserved. PII: S 0 0 2 2 - 0 2 4 8 ( 9 8 ) 0 0 4 8 4 - 9