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Chemical vapour deposition of zirconium carbide and silicon carbide hybrid whiskers
Materials Letters 64 (2010) 552–554
Contents lists available at ScienceDirect
Materials Letters j o u r n a l h o m e p a g e : w w w. e l s ev i e r. c o m / l o c a t e / m a t l e t
Chemical vapour deposition of zirconium carbide and silicon carbide hybrid whiskers Qiaomu Liu, Litong Zhang, Laifei Cheng, Yiguang Wang ⁎ National Key Laboratory of Thermostructure Composite Materials, Northwestern Polytechnical University, Xi'an, 710072, China
a r t i c l e
i n f o
Article history: Received 13 November 2009 Accepted 1 December 2009 Available online 5 December 2009 Keywords: Chemical vapour deposition Ceramics Hybrid whiskers Silicon carbide Zirconium carbide
a b s t r a c t Zirconium carbide and silicon carbide hybrid whiskers were codeposited by chemical vapour deposition using methyl trichlorosilane, zirconium chloride, methane and hydrogen as the precursors. The zirconium carbide and silicon carbide whiskers were characterized by scanning electron microscopy, energy dispersive X-ray spectroscopy and X-ray diffraction. The results indicate that the codeposition process is more effective in the presence of methane than in the absence of methane. The codeposition process and the growth of zirconium carbide in the whiskers can be accelerated at high temperature in the presence of methane. A growth model was proposed based on the deposition model of carbon, zirconium carbide and silicon carbide. © 2009 Elsevier B.V. All rights reserved.
1. Introduction Zirconium carbide (ZrC) and silicon carbide (SiC) are important high temperature ceramic materials with many applications due to their superior properties, such as high hardness, high melting point, good nuclear property, good thermal shock resistance, and low thermal conductivity [1,2]. However, ZrC or SiC cannot be used alone in ultrahigh temperature environments due to the decomposition of SiC and oxidation of ZrC [1,2]. A combination of ZrC and SiC might be able to endure more aggressive environments [3,4]. ZrC or SiC whiskers preparation by chemical vapour deposition (CVD) has been investigated intensively in the last few decades [5– 11]. Since CVD is a mature method on utilizing whiskers to reinforce and toughen ceramic composites [8–11]. However, the codeposition of ZrC and SiC hybrid whiskers (ZrC–SiC whiskers) has rarely been reported. In this study, ZrC–SiC whiskers were codeposited by CVD using methyl trichlorosilane (MTS: CH3SiCl3), zirconium chloride (ZrCl4), methane (CH4) and hydrogen (H2) as the precursors. A growth model was proposed based on the deposition model of carbon, ZrC and SiC.
2. Experimental The codeposition was performed in a horizontal hot-wall deposition apparatus. The experimental procedures were described in the previous papers [12,13]. MTS was introduced into the deposition chamber by bubbling with H2 at 30 °C.
⁎ Corresponding author. Tel.: +86 29 88494622; fax: +86 29 88494620. E-mail address: [email protected] (Y. Wang). 0167-577X/$ – see front matter © 2009 Elsevier B.V. All rights reserved. doi:10.1016/j.matlet.2009.12.002
After deposition, the morphologies and the compositions of the ZrC–SiC whiskers were characterized by scanning electron microscopy (SEM, JEOL6700F, Tokyo, Japan) in conjunction with energy dispersive X-ray spectroscopy (EDS, GENESIS XM2, EDAX, USA). The phases of the whiskers were characterized by X-ray diffraction (XRD, Rigaku D/max-2400, Tokyo, Japan).
3. Results and discussion The morphologies of the ZrC–SiC whiskers at different deposition temperatures and CH4 flow rates are shown in Fig. 1. The average diameter of the ZrC–SiC whiskers increases from 90 nm to 4 μm with increasing the deposition temperature from 1050 °C to 1250 °C in the presence of CH4 (Fig. 1(a)–(c)). The average diameter of the whiskers is only 200 nm in the absence of CH4 even at 1250 °C (Fig. 1(d)). It is demonstrated that the codeposition of the ZrC–SiC whiskers is more effective in the presence of CH4, and its growth can be accelerated at higher temperature. The results are still confirmed by the XRD and EDS patterns of the ZrC–SiC whiskers (Fig. 2). The results show that the growth of ZrC in the ZrC–SiC whiskers can be accelerated at higher temperature in the presence of CH4. It is believed that a dense coating can be gained at higher temperature, above 1250 °C, in the presence of CH4. The ZrC–SiC whiskers have a ZrC core with a SiC shell at 1250 °C in the presence of CH4 (Fig. 3). There is an obvious element distribution gradient along the radial direction of the whisker. In order to understand the growth mechanism of ZrC–SiC whiskers, a growth model was proposed based on the deposition model of C, ZrC and SiC (Fig. 4). At lower temperatures (b1250 °C), the Si–C bonds in MTS still intact and the derivatives of CH4 are more stable than any of the silicon containing species [14]. Therefore, the deposition of ZrC is
Q. Liu et al. / Materials Letters 64 (2010) 552–554
553
Fig. 1. Surface morphologies of the ZrC–SiC whiskers at different temperatures and CH4 flow rates: (a) 1050 °C, CH4: 6 ml/min; (b) 1150 °C, CH4: 6 ml/min; (c) 1250 °C, CH4: 6 ml/min; (d) 1250 °C, CH4: 0 ml/min.
suppressed. At 1250 °C, MTS decomposes and then forms silicon containing liquid droplets and carbon containing rigid droplets [15,16]. The silicon containing droplets wet the substrate and spread over it (1 in Fig. 4). Simultaneously, carbon containing droplets are formed on these silicon containing droplets. The size of the carbon containing droplets is smaller than that of the silicon containing droplets because its formation is more difficult (2 in Fig. 4) [13,14]. The reduced ZrCl4 (ZrClx, x ≤ 4) species dissolve in the carbon containing droplets and reacts with them to form ZrC [12,13]. At the same time, the gaseous carbon containing species, maybe.CH3, dissolve in the silicon containing droplets and react with them to form SiC [13,15] (3 in Fig. 4). There are almost no reactions that occur between these two droplets due to the poor wettability. The supersaturation of two kinds of droplets results in nucleation of ZrC–SiC whiskers. The whiskers grow outward as the intermediate species continuously dissolve in the droplets (4 in Fig. 4). The size of the droplets determines the whisker diameter. 4. Conclusions ZrC–SiC whiskers were prepared by CVD from the MTS–ZrCl4–CH4–H2 system. The results indicate that the codeposition process is more effective in the presence of CH4 than in the absence of CH4. The growth of ZrC–SiC whiskers and the growth of ZrC in the whiskers can be accelerated at high temperature in the presence of CH4. Considerable experiments are required to obtain more accurate information for codeposition of ZrC–SiC whiskers from the MTS–ZrCl4–CH4–H2 system. The properties characterization of ZrC–SiC whiskers reinforced ceramic composites is in process. Acknowledgement The Natural Science Foundation of China (No. 90716023) supported this work financially.
References [1] Pierson HO. Handbook of refractory carbides and nitrides: properties, characteristics, processing, and applications. New Jersey: Noyes Publications; 1996. [2] Roewer G, Herzog U, Trommer K, Muller E, Fruhauf S. Silicon carbide—a survey of synthetic approaches, properties and applications. In: Jansen M, editor. High performance non-oxide ceramics I. Germany: Springer-Verlag Berlin Heidelberg; 2002. [3] Licheri R, Orrù R, Musa C, Cao G. Combination of SHS and SPS techniques for fabrication of fully dense ZrB2–ZrC–SiC composites. Mater Lett 2008;63:432–5. [4] Wang Z, Dong SM, Zhang XY, Zhou HJ, Wu DX, Zhou Q, et al. Fabrication and properties of Cf/SiC–ZrC composites. J Am Ceram Soc 2008;91:3434–6. [5] Kato A, Tamari N. Some common aspects of the growth of TiN, ZrN, TiC and ZrC whiskers in chemical vapor deposition. J Cryst Growth 1980;149:99–203. [6] Nobuyuki T, Akio K. Catalytic effect of nickel on the growth of zirconium carbide whiskers by chemical vapor deposition. J Less-Common Met 1978;58:147–60. [7] Leu IC, Lu YM, Hon MH. Factors determining the diameter of silicon carbide whiskers prepared by chemical vapor deposition. Mater Chem Phys 1998;56:256–61. [8] Fu QG, Li HJ, Shi XH, Li KZ, Hu ZB, Wei J. Microstructure and growth mechanism of SiC whiskers on carbon–carbon composites prepared by CVD. Mater Lett 2005;59:2593–7. [9] Milewski JV, Gac FD, Petrovic JJ, Skaggs SR. Growth of beta-silicon carbide whiskers by the VLS process. J Mater Sci 1985;20:1160–6. [10] Ci L, Ryu Z, Jin-Phillipp NY, Rühle M. Carbon nanotubes SiC whiskers composite prepared by CVD method. Diam Relat Mater 2007;16:531–6. [11] Johnsson M. Synthesis of boride, carbide, and carbonitride whiskers. Solid State Ion 2004;172:365–8. [12] Wang YG, Liu QM, Liu JL, Zhang LT, Cheng LF. Deposition mechanism for chemical vapor deposition of zirconium carbide coatings. J Am Ceram Soc 2008;91:1249–52. [13] Liu QM, Zhang LT, Cheng LF, Wang YG. Morphologies and growth mechanisms of zirconium carbide films by chemical vapor deposition. J Coat Technol Res 2008;6:269–73. [14] Besmann T, Sheldon B, Moss T, Kaster M. Depletion effects of silicon carbide deposition from methyltrichlorosilane. J Am Ceram Soc 1992;75:2899–903. [15] Loumagne F, Langlais F, Naslain R. Reactional mechanisms of the chemical vapour deposition of SiC-based ceramics from CH3SiCl3–H2 gas precursor. J Cryst Growth 1995;155:205–13. [16] Xu YD, Cheng LF, Zhang LT, Zhou W. Morphology and growth mechanism of silicon carbide chemical vapor deposited at low temperatures and normal atmosphere. J Mater Sci 1999;34:551–5.
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Q. Liu et al. / Materials Letters 64 (2010) 552–554
Fig. 3. Transverse section of the ZrC–SiC whiskers at 1250 °C with CH4: 6 ml/min.
Fig. 4. Growth model of the ZrC–SiC whiskers.
Fig. 2. (a) XRD and (b) EDS patterns of the ZrC–SiC whiskers at different temperatures and CH4 flow rates.
Contents lists available at ScienceDirect
Materials Letters j o u r n a l h o m e p a g e : w w w. e l s ev i e r. c o m / l o c a t e / m a t l e t
Chemical vapour deposition of zirconium carbide and silicon carbide hybrid whiskers Qiaomu Liu, Litong Zhang, Laifei Cheng, Yiguang Wang ⁎ National Key Laboratory of Thermostructure Composite Materials, Northwestern Polytechnical University, Xi'an, 710072, China
a r t i c l e
i n f o
Article history: Received 13 November 2009 Accepted 1 December 2009 Available online 5 December 2009 Keywords: Chemical vapour deposition Ceramics Hybrid whiskers Silicon carbide Zirconium carbide
a b s t r a c t Zirconium carbide and silicon carbide hybrid whiskers were codeposited by chemical vapour deposition using methyl trichlorosilane, zirconium chloride, methane and hydrogen as the precursors. The zirconium carbide and silicon carbide whiskers were characterized by scanning electron microscopy, energy dispersive X-ray spectroscopy and X-ray diffraction. The results indicate that the codeposition process is more effective in the presence of methane than in the absence of methane. The codeposition process and the growth of zirconium carbide in the whiskers can be accelerated at high temperature in the presence of methane. A growth model was proposed based on the deposition model of carbon, zirconium carbide and silicon carbide. © 2009 Elsevier B.V. All rights reserved.
1. Introduction Zirconium carbide (ZrC) and silicon carbide (SiC) are important high temperature ceramic materials with many applications due to their superior properties, such as high hardness, high melting point, good nuclear property, good thermal shock resistance, and low thermal conductivity [1,2]. However, ZrC or SiC cannot be used alone in ultrahigh temperature environments due to the decomposition of SiC and oxidation of ZrC [1,2]. A combination of ZrC and SiC might be able to endure more aggressive environments [3,4]. ZrC or SiC whiskers preparation by chemical vapour deposition (CVD) has been investigated intensively in the last few decades [5– 11]. Since CVD is a mature method on utilizing whiskers to reinforce and toughen ceramic composites [8–11]. However, the codeposition of ZrC and SiC hybrid whiskers (ZrC–SiC whiskers) has rarely been reported. In this study, ZrC–SiC whiskers were codeposited by CVD using methyl trichlorosilane (MTS: CH3SiCl3), zirconium chloride (ZrCl4), methane (CH4) and hydrogen (H2) as the precursors. A growth model was proposed based on the deposition model of carbon, ZrC and SiC.
2. Experimental The codeposition was performed in a horizontal hot-wall deposition apparatus. The experimental procedures were described in the previous papers [12,13]. MTS was introduced into the deposition chamber by bubbling with H2 at 30 °C.
⁎ Corresponding author. Tel.: +86 29 88494622; fax: +86 29 88494620. E-mail address: [email protected] (Y. Wang). 0167-577X/$ – see front matter © 2009 Elsevier B.V. All rights reserved. doi:10.1016/j.matlet.2009.12.002
After deposition, the morphologies and the compositions of the ZrC–SiC whiskers were characterized by scanning electron microscopy (SEM, JEOL6700F, Tokyo, Japan) in conjunction with energy dispersive X-ray spectroscopy (EDS, GENESIS XM2, EDAX, USA). The phases of the whiskers were characterized by X-ray diffraction (XRD, Rigaku D/max-2400, Tokyo, Japan).
3. Results and discussion The morphologies of the ZrC–SiC whiskers at different deposition temperatures and CH4 flow rates are shown in Fig. 1. The average diameter of the ZrC–SiC whiskers increases from 90 nm to 4 μm with increasing the deposition temperature from 1050 °C to 1250 °C in the presence of CH4 (Fig. 1(a)–(c)). The average diameter of the whiskers is only 200 nm in the absence of CH4 even at 1250 °C (Fig. 1(d)). It is demonstrated that the codeposition of the ZrC–SiC whiskers is more effective in the presence of CH4, and its growth can be accelerated at higher temperature. The results are still confirmed by the XRD and EDS patterns of the ZrC–SiC whiskers (Fig. 2). The results show that the growth of ZrC in the ZrC–SiC whiskers can be accelerated at higher temperature in the presence of CH4. It is believed that a dense coating can be gained at higher temperature, above 1250 °C, in the presence of CH4. The ZrC–SiC whiskers have a ZrC core with a SiC shell at 1250 °C in the presence of CH4 (Fig. 3). There is an obvious element distribution gradient along the radial direction of the whisker. In order to understand the growth mechanism of ZrC–SiC whiskers, a growth model was proposed based on the deposition model of C, ZrC and SiC (Fig. 4). At lower temperatures (b1250 °C), the Si–C bonds in MTS still intact and the derivatives of CH4 are more stable than any of the silicon containing species [14]. Therefore, the deposition of ZrC is
Q. Liu et al. / Materials Letters 64 (2010) 552–554
553
Fig. 1. Surface morphologies of the ZrC–SiC whiskers at different temperatures and CH4 flow rates: (a) 1050 °C, CH4: 6 ml/min; (b) 1150 °C, CH4: 6 ml/min; (c) 1250 °C, CH4: 6 ml/min; (d) 1250 °C, CH4: 0 ml/min.
suppressed. At 1250 °C, MTS decomposes and then forms silicon containing liquid droplets and carbon containing rigid droplets [15,16]. The silicon containing droplets wet the substrate and spread over it (1 in Fig. 4). Simultaneously, carbon containing droplets are formed on these silicon containing droplets. The size of the carbon containing droplets is smaller than that of the silicon containing droplets because its formation is more difficult (2 in Fig. 4) [13,14]. The reduced ZrCl4 (ZrClx, x ≤ 4) species dissolve in the carbon containing droplets and reacts with them to form ZrC [12,13]. At the same time, the gaseous carbon containing species, maybe.CH3, dissolve in the silicon containing droplets and react with them to form SiC [13,15] (3 in Fig. 4). There are almost no reactions that occur between these two droplets due to the poor wettability. The supersaturation of two kinds of droplets results in nucleation of ZrC–SiC whiskers. The whiskers grow outward as the intermediate species continuously dissolve in the droplets (4 in Fig. 4). The size of the droplets determines the whisker diameter. 4. Conclusions ZrC–SiC whiskers were prepared by CVD from the MTS–ZrCl4–CH4–H2 system. The results indicate that the codeposition process is more effective in the presence of CH4 than in the absence of CH4. The growth of ZrC–SiC whiskers and the growth of ZrC in the whiskers can be accelerated at high temperature in the presence of CH4. Considerable experiments are required to obtain more accurate information for codeposition of ZrC–SiC whiskers from the MTS–ZrCl4–CH4–H2 system. The properties characterization of ZrC–SiC whiskers reinforced ceramic composites is in process. Acknowledgement The Natural Science Foundation of China (No. 90716023) supported this work financially.
References [1] Pierson HO. Handbook of refractory carbides and nitrides: properties, characteristics, processing, and applications. New Jersey: Noyes Publications; 1996. [2] Roewer G, Herzog U, Trommer K, Muller E, Fruhauf S. Silicon carbide—a survey of synthetic approaches, properties and applications. In: Jansen M, editor. High performance non-oxide ceramics I. Germany: Springer-Verlag Berlin Heidelberg; 2002. [3] Licheri R, Orrù R, Musa C, Cao G. Combination of SHS and SPS techniques for fabrication of fully dense ZrB2–ZrC–SiC composites. Mater Lett 2008;63:432–5. [4] Wang Z, Dong SM, Zhang XY, Zhou HJ, Wu DX, Zhou Q, et al. Fabrication and properties of Cf/SiC–ZrC composites. J Am Ceram Soc 2008;91:3434–6. [5] Kato A, Tamari N. Some common aspects of the growth of TiN, ZrN, TiC and ZrC whiskers in chemical vapor deposition. J Cryst Growth 1980;149:99–203. [6] Nobuyuki T, Akio K. Catalytic effect of nickel on the growth of zirconium carbide whiskers by chemical vapor deposition. J Less-Common Met 1978;58:147–60. [7] Leu IC, Lu YM, Hon MH. Factors determining the diameter of silicon carbide whiskers prepared by chemical vapor deposition. Mater Chem Phys 1998;56:256–61. [8] Fu QG, Li HJ, Shi XH, Li KZ, Hu ZB, Wei J. Microstructure and growth mechanism of SiC whiskers on carbon–carbon composites prepared by CVD. Mater Lett 2005;59:2593–7. [9] Milewski JV, Gac FD, Petrovic JJ, Skaggs SR. Growth of beta-silicon carbide whiskers by the VLS process. J Mater Sci 1985;20:1160–6. [10] Ci L, Ryu Z, Jin-Phillipp NY, Rühle M. Carbon nanotubes SiC whiskers composite prepared by CVD method. Diam Relat Mater 2007;16:531–6. [11] Johnsson M. Synthesis of boride, carbide, and carbonitride whiskers. Solid State Ion 2004;172:365–8. [12] Wang YG, Liu QM, Liu JL, Zhang LT, Cheng LF. Deposition mechanism for chemical vapor deposition of zirconium carbide coatings. J Am Ceram Soc 2008;91:1249–52. [13] Liu QM, Zhang LT, Cheng LF, Wang YG. Morphologies and growth mechanisms of zirconium carbide films by chemical vapor deposition. J Coat Technol Res 2008;6:269–73. [14] Besmann T, Sheldon B, Moss T, Kaster M. Depletion effects of silicon carbide deposition from methyltrichlorosilane. J Am Ceram Soc 1992;75:2899–903. [15] Loumagne F, Langlais F, Naslain R. Reactional mechanisms of the chemical vapour deposition of SiC-based ceramics from CH3SiCl3–H2 gas precursor. J Cryst Growth 1995;155:205–13. [16] Xu YD, Cheng LF, Zhang LT, Zhou W. Morphology and growth mechanism of silicon carbide chemical vapor deposited at low temperatures and normal atmosphere. J Mater Sci 1999;34:551–5.
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Q. Liu et al. / Materials Letters 64 (2010) 552–554
Fig. 3. Transverse section of the ZrC–SiC whiskers at 1250 °C with CH4: 6 ml/min.
Fig. 4. Growth model of the ZrC–SiC whiskers.
Fig. 2. (a) XRD and (b) EDS patterns of the ZrC–SiC whiskers at different temperatures and CH4 flow rates.