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Combustion synthesis of (TiC + SiC) composite powders by coupling strong and weak exothermic reactions
Journal of Alloys and Compounds 492 (2010) L82–L86
Contents lists available at ScienceDirect
Journal of Alloys and Compounds journal homepage: www.elsevier.com/locate/jallcom
Letter
Combustion synthesis of (TiC + SiC) composite powders by coupling strong and weak exothermic reactions Guanghua Liu a,b,∗ , Jiangtao Li a , Kexin Chen b , Heping Zhou b a b
Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Beijing 100190, People’s Republic of China Department of Materials Science and Engineering, State Key Laboratory of New Ceramics and Fine Processing, Tsinghua University, Beijing 100084, People’s Republic of China
a r t i c l e
i n f o
Article history: Received 11 December 2008 Received in revised form 3 December 2009 Accepted 6 December 2009 Available online 28 December 2009 Keywords: Chemical synthesis X-ray diffraction Scanning electron microscopy
a b s t r a c t By coupling strong and weak exothermic reactions, (TiC + SiC) composite powders have been prepared by combustion synthesis. The reaction temperature and heating rate strongly depend on the Ti/Si ratios in the reactant powder mixture. The phase assemblage and microstructure of the products can be manipulated by varying the starting compositions. According to SEM observation, the reaction procedure and formation mechanism of TiC and SiC are discussed. It is proposed that the presence of metallic melt phases is important for the formation of the carbide phases. © 2009 Elsevier B.V. All rights reserved.
1. Introduction Combustion synthesis, also known as self-propagating hightemperature synthesis or briefly SHS, is now a well-established technique to prepare a large variety of inorganic materials [1–3]. This technique usually applies to strong exothermic reaction systems, and for weak exothermic systems the self-sustained combustion reaction is not guaranteed because of the insufficiency of heat energy. In order to carry out combustion synthesis in weak exothermic reaction systems, preliminary or assistant treatment is necessary such as preheating, mechanical activation, and field activation [4,5]. Another approach to realize the self-sustained combustion of a weak exothermic reaction system is to couple it with a strong one. By this means, composite materials will be produced, and the reaction kinetics (such as the reaction temperature and heating rate) can be manipulated by changing the proportions of the two reaction systems. TiC and SiC are two important ceramic materials and their powders have been prepared by combustion synthesis [6–13]. The reaction system of (Ti + C) is highly exothermic and the combustion synthesis of TiC can be readily achieved [14]. The system of (Si + C), however, is far less exothermic and self-sustained com-
∗ Corresponding author at: Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Beijing 100190, People’s Republic of China. Tel.: +86 10 82543695; fax: +86 10 82543693. E-mail address: [email protected] (G. Liu). 0925-8388/$ – see front matter © 2009 Elsevier B.V. All rights reserved. doi:10.1016/j.jallcom.2009.12.033
bustion reaction is difficult with no preliminary treatment. It is expected that, by combining these two combustion reaction systems, (TiC + SiC) composite powders can be produced, which are possible raw materials for preparing consolidated (TiC + SiC) composite ceramics with improved mechanical properties [15–17]. This paper aims at the combustion synthesis of (TiC + SiC) composite powders by coupling the strong exothermic reaction of (Ti + C) with the weak one of (Si + C). The effect of starting composition on the reaction kinetics and the phase composition and microstructure of the products are investigated. Based on the experimental results, the reaction procedure and the growth mechanism of TiC and SiC grains are discussed. 2. Experimental Ti (purity >99.0%, 400 mesh), Si (purity >99.0%, 300 mesh), and carbon black powders were used as the raw materials. According to the starting compositions listed in Table 1, the raw materials were mixed with agate balls in absolute ethanol in a plastic jar and homogenized by ball milling for 8 h. The obtained slurry was dried at 80 ◦ C for 3 h. Then, the reactant powder mixture was loaded into a cylindrical graphite crucible, which was subsequently placed into a special reaction chamber for combustion synthesis. The chamber was evacuated to a vacuum of 100 Pa and then filled with Ar gas to 0.1 MPa. Combustion reaction was triggered by passing an electric current through a tungsten coil closed above the powder mixture. The temperature was recorded by a thermocouple protected with an alumina tube and inserted in the sample. After the combustion reaction was over and the sample cooled down, the product was collected for later characterization. The phase composition was identified by X-ray diffraction (XRD; D8-Advance, Bruker, Germany) using Cu-K␣ radiation. The microstructure was observed by scanning electron microscopy (SEM; JSM-6460LV, JEOL, Japan) equipped with energy dispersive spectroscopy (EDS; INCA, Oxford Instrument, UK).
G. Liu et al. / Journal of Alloys and Compounds 492 (2010) L82–L86
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Table 1 Phase assemblages of the products and the lattice parameters of TiC and SiC for the samples with different starting compositions. Sample
Starting composition
Phase assemblage
aTiC (Å)
aSiC (Å)
TSC-1 TSC-2 TSC-3 TSC-4
0.33Ti + 0.67Si + C (x = 0.33) 0.50Ti + 0.50Si + C (x = 0.50) 0.67Ti + 0.33Si + C (x = 0.67) 0.80Ti + 0.20Si + C (x = 0.80)
TiC(s), SiC(s) TiC(s), SiC(m) TiC(s), SiC(w) TiC(s), SiC(vw)
4.324 4.325 4.322 4.325
4.356 4.358 4.354 4.356
s = strong, m = medium, w = weak, vw = very weak. Note: The starting compositions and the x values are related with the chemical reaction formula: xTi + (1 − x)Si + C = xTiC + (1 − x)SiC.
Fig. 1. Temperature history of TSC-3 during the combustion reaction. The inset shows the heating rate.
3. Results and discussion Fig. 1 shows the temperature history of the sample TSC-3 during combustion synthesis. Once the combustion reaction starts, there is a steep rise in temperature from nearly room temperature to about 1900 ◦ C, and the maximum heating rate (dT/dt) is more than 5000 ◦ C/s. For different samples, the reaction temperature and heating rate depend on the starting composition and increase with an elevated Ti/(Ti + Si) ratio. As shown in Fig. 2, when the Ti/(Ti + Si) ratio changes from 0.33 to 0.80, the reaction temperature increases from 1690 to 2060 ◦ C.
Fig. 2. The maximum reaction temperature and heating rate for the samples with different Ti/(Ti + Si) molar ratios.
Fig. 3 shows the XRD patterns of the reaction products, revealing that (TiC + SiC) composites have been prepared as expected. The reactions between the metallic powders with carbon black are complete with no impurity phases detected. With increasing Ti/(Ti + Si) ratios, there is a corresponding increase in the proportion between TiC and SiC in the products. In other words, the phase assemblage of the product can be manipulated by varying the starting composition. According to the XRD results, the lattice parameters of TiC and SiC are calculated and reported in Table 1. For different sam-
Fig. 3. XRD patterns of the reaction products: (a) TSC-1; (b) TSC-2; (c) TSC-3 and (d) TSC-4.
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Fig. 4. SEM images and EDS spectra of the reaction products: (a) an overview, TSC-2; (b) TiC grains, TSC-2; (c)–(f) SiC grains, from TSC-1 to TSC-4; (g) EDS spectrum of TiC and (h) EDS spectrum of SiC.
G. Liu et al. / Journal of Alloys and Compounds 492 (2010) L82–L86
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Fig. 5. SEM images and EDS spectra of the products collected from sample surface: (a)–(c) micrographs and EDS of SiC grains, from the sample TSC-3 and (d)–(e) micrograph and EDS of TiC grains, from the sample TSC-4.
ples, the calculated lattice parameters are close despite the change in the proportions of TiC and SiC. Fig. 4 shows the SEM images of the reaction products from different samples. These products consist of coarse spherical agglomerates and each agglomerate is composed of TiC or SiC grains. Most TiC grains have a size of several microns, which changes little in the samples with different starting compositions. The grain size of SiC, however, is affected by the starting composition and becomes larger with increasing Ti/(Ti + Si) ratios. For example, in the sample TSC-1 with Ti/(Ti + Si) = 0.33, submicron SiC grains are obtained with an average size of about 0.3 m, but in TSC-4 with Ti/(Ti + Si) = 0.8, most SiC grains are larger than 1.0 m. Besides the grain size, the morphology of SiC grains also depends on the starting composition. With a Ti/(Ti + Si) ratio in the range of 0.33–0.67, equiaxed SiC grains are obtained, and when the Ti/(Ti + Si) ratio increases to 0.8, most SiC grains develop into a faceted shape. This transition of grain morphology from equiaxed to faceted shape is thought to be caused by the increase in reaction temperature. At a higher temperature, the mass transportation (via mechanisms such as evaporation–condensation, surface diffusion, and lattice diffusion) will be enhanced, and the morphology transi-
tion of SiC grains can take place more easily. In this way, at a higher temperature, the SiC grains tend to transform to the equilibrium crystallization shape with the minimum total surface energy and generally bounded by the low-index crystalline planes with lower surface energy. The dependence of the grain size and morphology of SiC on the starting compositions can be attributed to the elevation of reaction temperature with increasing Ti/(Ti + Si) ratios. This dependence, at the same time, indicates the possibility of controlling the microstructure of the product by changing the starting composition. As shown in Fig. 2, for all the samples the reaction temperature is above the melting point of Ti (1670 ◦ C) and that of Si (1412 ◦ C). In this way, the synthesis of TiC and SiC is thought to be fulfilled by the reaction of carbon with Ti or Si melt. Briefly, the combustion reaction can be divided into three steps. The first step is the formation of a Ti or Si metallic melt, which inclines to maintain a spherical shape to reduce the surface energy. In the second step, the carbon particles are wetted by the metallic melt and dispersed in it. The dissolution of a small amount of carbon in the melt can also take place. In the last step, the metallic melt reacts with carbon to produce carbides. During the combustion reaction, each bead of metallic melt can be
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regarded as a reaction unit, which keeps its spherical shape after the reaction and transforms into an agglomerate of carbide grains, as shown in Fig. 4(a). The reaction procedure proposed above is also supported by SEM observation on the products collected from the surface of samples. Fig. 5(a) shows a spherical agglomerate with an inner core and an outer shell consisting of fine round particles, which are shown more clearly in Fig. 5(b). By EDS analysis, the inner core is composed of SiC grains, and the outer shell with fine particles contains much oxygen and thus expected to be silica. The spherical agglomerate with the core–shell structure is proposed to result from a bead of Si melt. Fig. 5(d) shows the crystallization of TiC grains from Ti melt, where the boundaries of TiC grains are not so distinct as those in Fig. 4(b). This difference can be explained by more dissipation of heat energy at the surface of the sample compared with the interior part. 4. Conclusion
imental results, it is proposed that the combustion reaction can be briefly divided into three steps: the formation of metallic melt phases, the dispersion and dissolution of carbon particles in the metallic melts, and finally the formation of carbides. References [1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12]
Combustion synthesis of (TiC + SiC) composite powders have been realized by coupling strong and weak exothermic reactions. With an increasing Ti/(Ti + Si) ratio in the reactant powder mixture, both the reaction temperature and heating rate are raised. The Ti/(Ti + Si) ratio also has an influence on the phase assemblage, grain size, and grain morphology of the products. Based on the exper-
[13] [14] [15] [16] [17]
Z.A. Munir, A.T. Umberto, Mater. Sci. Rep. 3 (1989) 277. A.G. Merzhanov, Ceram. Int. 21 (1995) 371. J.J. Moore, H.J. Feng, Prog. Mater. Sci. 39 (1995) 243. R.M. Ren, Z.G. Yang, L. Shaw, Ceram. Eng. Sci. Proc. 19 (1998) 461. A. Feng, Z.A. Munir, J. Appl. Phys. 76 (1994) 1927. S.D. Dunmead, D.W. Readey, C.E. Semler, J.B. Holt, J. Am. Ceram. Soc. 72 (1989) 2318. C.L. Yeh, Y.D. Chen, Ceram. Int. 31 (2005) 719. M.F. Beaufort, N. Karnatak, S. Dubois, J. Mater. Syn. Proc. 10 (2002) 277. J.C. Han, X.H. Zhang, J.V. Wood, Mater. Sci. Eng. A 280 (2000) 328. B. Cochepin, V. Gauthier, D. Vrel, S. Dubois, J. Cryst. Growth 304 (2007) 481. F. Maglia, U. Anselmi-Tamburini, C. Deidda, F. Delogu, G. Cocco, Z.A. Munir, J. Mater. Sci. 39 (2004) 5227. Y.Q. Liu, L.F. Zhang, Q.Z. Yan, X.D. Mao, Q. Feng, C.C. Ge, Int. J. Miner. Metall. Mater. 16 (2009) 322. D. Kata, J. Lis, R. Pampuch, Solid State Ionics 101–103 (1997) 65. S. Yin, Combustion Synthesis (in Chinese), Metallurgical Industry Press, Beijing, 1999. J.H. Liversage, D.S. McLachlan, I. Sigalas, M. Herrmann, J. Am. Ceram. Soc. 90 (2007) 2189. L.J. Wang, W. Jiang, J. Mater. Sci. 39 (2004) 4515. Y.W. Kim, S.G. Lee, Y.I. Lee, J. Mater. Sci. 35 (2000) 5569.
Contents lists available at ScienceDirect
Journal of Alloys and Compounds journal homepage: www.elsevier.com/locate/jallcom
Letter
Combustion synthesis of (TiC + SiC) composite powders by coupling strong and weak exothermic reactions Guanghua Liu a,b,∗ , Jiangtao Li a , Kexin Chen b , Heping Zhou b a b
Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Beijing 100190, People’s Republic of China Department of Materials Science and Engineering, State Key Laboratory of New Ceramics and Fine Processing, Tsinghua University, Beijing 100084, People’s Republic of China
a r t i c l e
i n f o
Article history: Received 11 December 2008 Received in revised form 3 December 2009 Accepted 6 December 2009 Available online 28 December 2009 Keywords: Chemical synthesis X-ray diffraction Scanning electron microscopy
a b s t r a c t By coupling strong and weak exothermic reactions, (TiC + SiC) composite powders have been prepared by combustion synthesis. The reaction temperature and heating rate strongly depend on the Ti/Si ratios in the reactant powder mixture. The phase assemblage and microstructure of the products can be manipulated by varying the starting compositions. According to SEM observation, the reaction procedure and formation mechanism of TiC and SiC are discussed. It is proposed that the presence of metallic melt phases is important for the formation of the carbide phases. © 2009 Elsevier B.V. All rights reserved.
1. Introduction Combustion synthesis, also known as self-propagating hightemperature synthesis or briefly SHS, is now a well-established technique to prepare a large variety of inorganic materials [1–3]. This technique usually applies to strong exothermic reaction systems, and for weak exothermic systems the self-sustained combustion reaction is not guaranteed because of the insufficiency of heat energy. In order to carry out combustion synthesis in weak exothermic reaction systems, preliminary or assistant treatment is necessary such as preheating, mechanical activation, and field activation [4,5]. Another approach to realize the self-sustained combustion of a weak exothermic reaction system is to couple it with a strong one. By this means, composite materials will be produced, and the reaction kinetics (such as the reaction temperature and heating rate) can be manipulated by changing the proportions of the two reaction systems. TiC and SiC are two important ceramic materials and their powders have been prepared by combustion synthesis [6–13]. The reaction system of (Ti + C) is highly exothermic and the combustion synthesis of TiC can be readily achieved [14]. The system of (Si + C), however, is far less exothermic and self-sustained com-
∗ Corresponding author at: Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Beijing 100190, People’s Republic of China. Tel.: +86 10 82543695; fax: +86 10 82543693. E-mail address: [email protected] (G. Liu). 0925-8388/$ – see front matter © 2009 Elsevier B.V. All rights reserved. doi:10.1016/j.jallcom.2009.12.033
bustion reaction is difficult with no preliminary treatment. It is expected that, by combining these two combustion reaction systems, (TiC + SiC) composite powders can be produced, which are possible raw materials for preparing consolidated (TiC + SiC) composite ceramics with improved mechanical properties [15–17]. This paper aims at the combustion synthesis of (TiC + SiC) composite powders by coupling the strong exothermic reaction of (Ti + C) with the weak one of (Si + C). The effect of starting composition on the reaction kinetics and the phase composition and microstructure of the products are investigated. Based on the experimental results, the reaction procedure and the growth mechanism of TiC and SiC grains are discussed. 2. Experimental Ti (purity >99.0%, 400 mesh), Si (purity >99.0%, 300 mesh), and carbon black powders were used as the raw materials. According to the starting compositions listed in Table 1, the raw materials were mixed with agate balls in absolute ethanol in a plastic jar and homogenized by ball milling for 8 h. The obtained slurry was dried at 80 ◦ C for 3 h. Then, the reactant powder mixture was loaded into a cylindrical graphite crucible, which was subsequently placed into a special reaction chamber for combustion synthesis. The chamber was evacuated to a vacuum of 100 Pa and then filled with Ar gas to 0.1 MPa. Combustion reaction was triggered by passing an electric current through a tungsten coil closed above the powder mixture. The temperature was recorded by a thermocouple protected with an alumina tube and inserted in the sample. After the combustion reaction was over and the sample cooled down, the product was collected for later characterization. The phase composition was identified by X-ray diffraction (XRD; D8-Advance, Bruker, Germany) using Cu-K␣ radiation. The microstructure was observed by scanning electron microscopy (SEM; JSM-6460LV, JEOL, Japan) equipped with energy dispersive spectroscopy (EDS; INCA, Oxford Instrument, UK).
G. Liu et al. / Journal of Alloys and Compounds 492 (2010) L82–L86
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Table 1 Phase assemblages of the products and the lattice parameters of TiC and SiC for the samples with different starting compositions. Sample
Starting composition
Phase assemblage
aTiC (Å)
aSiC (Å)
TSC-1 TSC-2 TSC-3 TSC-4
0.33Ti + 0.67Si + C (x = 0.33) 0.50Ti + 0.50Si + C (x = 0.50) 0.67Ti + 0.33Si + C (x = 0.67) 0.80Ti + 0.20Si + C (x = 0.80)
TiC(s), SiC(s) TiC(s), SiC(m) TiC(s), SiC(w) TiC(s), SiC(vw)
4.324 4.325 4.322 4.325
4.356 4.358 4.354 4.356
s = strong, m = medium, w = weak, vw = very weak. Note: The starting compositions and the x values are related with the chemical reaction formula: xTi + (1 − x)Si + C = xTiC + (1 − x)SiC.
Fig. 1. Temperature history of TSC-3 during the combustion reaction. The inset shows the heating rate.
3. Results and discussion Fig. 1 shows the temperature history of the sample TSC-3 during combustion synthesis. Once the combustion reaction starts, there is a steep rise in temperature from nearly room temperature to about 1900 ◦ C, and the maximum heating rate (dT/dt) is more than 5000 ◦ C/s. For different samples, the reaction temperature and heating rate depend on the starting composition and increase with an elevated Ti/(Ti + Si) ratio. As shown in Fig. 2, when the Ti/(Ti + Si) ratio changes from 0.33 to 0.80, the reaction temperature increases from 1690 to 2060 ◦ C.
Fig. 2. The maximum reaction temperature and heating rate for the samples with different Ti/(Ti + Si) molar ratios.
Fig. 3 shows the XRD patterns of the reaction products, revealing that (TiC + SiC) composites have been prepared as expected. The reactions between the metallic powders with carbon black are complete with no impurity phases detected. With increasing Ti/(Ti + Si) ratios, there is a corresponding increase in the proportion between TiC and SiC in the products. In other words, the phase assemblage of the product can be manipulated by varying the starting composition. According to the XRD results, the lattice parameters of TiC and SiC are calculated and reported in Table 1. For different sam-
Fig. 3. XRD patterns of the reaction products: (a) TSC-1; (b) TSC-2; (c) TSC-3 and (d) TSC-4.
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Fig. 4. SEM images and EDS spectra of the reaction products: (a) an overview, TSC-2; (b) TiC grains, TSC-2; (c)–(f) SiC grains, from TSC-1 to TSC-4; (g) EDS spectrum of TiC and (h) EDS spectrum of SiC.
G. Liu et al. / Journal of Alloys and Compounds 492 (2010) L82–L86
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Fig. 5. SEM images and EDS spectra of the products collected from sample surface: (a)–(c) micrographs and EDS of SiC grains, from the sample TSC-3 and (d)–(e) micrograph and EDS of TiC grains, from the sample TSC-4.
ples, the calculated lattice parameters are close despite the change in the proportions of TiC and SiC. Fig. 4 shows the SEM images of the reaction products from different samples. These products consist of coarse spherical agglomerates and each agglomerate is composed of TiC or SiC grains. Most TiC grains have a size of several microns, which changes little in the samples with different starting compositions. The grain size of SiC, however, is affected by the starting composition and becomes larger with increasing Ti/(Ti + Si) ratios. For example, in the sample TSC-1 with Ti/(Ti + Si) = 0.33, submicron SiC grains are obtained with an average size of about 0.3 m, but in TSC-4 with Ti/(Ti + Si) = 0.8, most SiC grains are larger than 1.0 m. Besides the grain size, the morphology of SiC grains also depends on the starting composition. With a Ti/(Ti + Si) ratio in the range of 0.33–0.67, equiaxed SiC grains are obtained, and when the Ti/(Ti + Si) ratio increases to 0.8, most SiC grains develop into a faceted shape. This transition of grain morphology from equiaxed to faceted shape is thought to be caused by the increase in reaction temperature. At a higher temperature, the mass transportation (via mechanisms such as evaporation–condensation, surface diffusion, and lattice diffusion) will be enhanced, and the morphology transi-
tion of SiC grains can take place more easily. In this way, at a higher temperature, the SiC grains tend to transform to the equilibrium crystallization shape with the minimum total surface energy and generally bounded by the low-index crystalline planes with lower surface energy. The dependence of the grain size and morphology of SiC on the starting compositions can be attributed to the elevation of reaction temperature with increasing Ti/(Ti + Si) ratios. This dependence, at the same time, indicates the possibility of controlling the microstructure of the product by changing the starting composition. As shown in Fig. 2, for all the samples the reaction temperature is above the melting point of Ti (1670 ◦ C) and that of Si (1412 ◦ C). In this way, the synthesis of TiC and SiC is thought to be fulfilled by the reaction of carbon with Ti or Si melt. Briefly, the combustion reaction can be divided into three steps. The first step is the formation of a Ti or Si metallic melt, which inclines to maintain a spherical shape to reduce the surface energy. In the second step, the carbon particles are wetted by the metallic melt and dispersed in it. The dissolution of a small amount of carbon in the melt can also take place. In the last step, the metallic melt reacts with carbon to produce carbides. During the combustion reaction, each bead of metallic melt can be
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regarded as a reaction unit, which keeps its spherical shape after the reaction and transforms into an agglomerate of carbide grains, as shown in Fig. 4(a). The reaction procedure proposed above is also supported by SEM observation on the products collected from the surface of samples. Fig. 5(a) shows a spherical agglomerate with an inner core and an outer shell consisting of fine round particles, which are shown more clearly in Fig. 5(b). By EDS analysis, the inner core is composed of SiC grains, and the outer shell with fine particles contains much oxygen and thus expected to be silica. The spherical agglomerate with the core–shell structure is proposed to result from a bead of Si melt. Fig. 5(d) shows the crystallization of TiC grains from Ti melt, where the boundaries of TiC grains are not so distinct as those in Fig. 4(b). This difference can be explained by more dissipation of heat energy at the surface of the sample compared with the interior part. 4. Conclusion
imental results, it is proposed that the combustion reaction can be briefly divided into three steps: the formation of metallic melt phases, the dispersion and dissolution of carbon particles in the metallic melts, and finally the formation of carbides. References [1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12]
Combustion synthesis of (TiC + SiC) composite powders have been realized by coupling strong and weak exothermic reactions. With an increasing Ti/(Ti + Si) ratio in the reactant powder mixture, both the reaction temperature and heating rate are raised. The Ti/(Ti + Si) ratio also has an influence on the phase assemblage, grain size, and grain morphology of the products. Based on the exper-
[13] [14] [15] [16] [17]
Z.A. Munir, A.T. Umberto, Mater. Sci. Rep. 3 (1989) 277. A.G. Merzhanov, Ceram. Int. 21 (1995) 371. J.J. Moore, H.J. Feng, Prog. Mater. Sci. 39 (1995) 243. R.M. Ren, Z.G. Yang, L. Shaw, Ceram. Eng. Sci. Proc. 19 (1998) 461. A. Feng, Z.A. Munir, J. Appl. Phys. 76 (1994) 1927. S.D. Dunmead, D.W. Readey, C.E. Semler, J.B. Holt, J. Am. Ceram. Soc. 72 (1989) 2318. C.L. Yeh, Y.D. Chen, Ceram. Int. 31 (2005) 719. M.F. Beaufort, N. Karnatak, S. Dubois, J. Mater. Syn. Proc. 10 (2002) 277. J.C. Han, X.H. Zhang, J.V. Wood, Mater. Sci. Eng. A 280 (2000) 328. B. Cochepin, V. Gauthier, D. Vrel, S. Dubois, J. Cryst. Growth 304 (2007) 481. F. Maglia, U. Anselmi-Tamburini, C. Deidda, F. Delogu, G. Cocco, Z.A. Munir, J. Mater. Sci. 39 (2004) 5227. Y.Q. Liu, L.F. Zhang, Q.Z. Yan, X.D. Mao, Q. Feng, C.C. Ge, Int. J. Miner. Metall. Mater. 16 (2009) 322. D. Kata, J. Lis, R. Pampuch, Solid State Ionics 101–103 (1997) 65. S. Yin, Combustion Synthesis (in Chinese), Metallurgical Industry Press, Beijing, 1999. J.H. Liversage, D.S. McLachlan, I. Sigalas, M. Herrmann, J. Am. Ceram. Soc. 90 (2007) 2189. L.J. Wang, W. Jiang, J. Mater. Sci. 39 (2004) 4515. Y.W. Kim, S.G. Lee, Y.I. Lee, J. Mater. Sci. 35 (2000) 5569.