- Email: [email protected]
In situ growth of TiCxN1−x whiskers in Al2O3 matrix for ceramic cutting tools
Materials Chemistry and Physics 113 (2009) 613–615
Contents lists available at ScienceDirect
Materials Chemistry and Physics journal homepage: www.elsevier.com/locate/matchemphys
In situ growth of TiCx N1−x whiskers in Al2 O3 matrix for ceramic cutting tools B.Q. Liu a,b,∗ , C.Z. Huang b , M.L. Gu c , H.L. Liu b a
School of Mechanical and Electrical Engineering, Weifang University, Weifang 261061, China Center for Advanced Jet Engineering Technologies (CaJET), School of Mechanical Engineering, Shandong University, Jinan 250061, China c School of Mechanical Engineering, Hebei University of Technology, Tianjin 300130, China b
a r t i c l e
i n f o
Article history: Received 12 December 2007 Accepted 9 August 2008 Keywords: TiCx N1−x whisker ␣-Al2 O3 In situ growth Carbothermal reduction process
a b s t r a c t For resolving the dispersing problem of whiskers and fabricating cutting tool materials with excellent properties, an in situ growth technology is used to directly synthesize TiCx N1−x whiskers in ␣-Al2 O3 matrix by a carbothermal reduction process at a temperature range of 1250–1550 ◦ C. The raw materials are consisted of TiO2 , carbon, nickel, and NaCl. Various molar ratios from 1:3, 1:4, 1:5 to 1:7 of TiO2 :C are experimentally used. For the molar ratio 1:3, a few whiskers can be found only at the synthesis temperature of 1550 ◦ C. For the other molar ratios, large amount of whiskers can be observed at the whole synthesis temperature range. The highest yield of whisker is observed when the synthesis temperature is 1250 ◦ C and the molar ratio of TiO2 :C is 1:4. The compound AlO appears at 1250 ◦ C and AlN instead at 1550 ◦ C. The majority of the synthesized whiskers display an ideal aspect ratio of 10–30 with a diameter of 1–3 m. No obviously influence on the whiskers growth by the present of ␣-Al2 O3 matrix powder can be noted. © 2008 Elsevier B.V. All rights reserved.
1. Introduction Due to their hardness and strength, whiskers of transition metal carbides, carbonitrides and nitrides are highly interesting as reinforcing materials in ceramics for cutting tools and other wear-resistant applications [1–4]. However, well dispersing whiskers into a ceramic matrix is very difficult and the agglomerations of these whiskers will severely decrease the density and mechanical properties of the composite [5]. Therefore, new fabrication strategies for whisker toughening ceramic tool materials should be developed. Due to the advantages such as simplifying the process, decreasing the cost and expecting unique properties by unique microstructures, in situ synthesis technology has been an important fabricating strategy for composites [6–8]. The application of such a technology on whisker toughening ceramic tool materials directly synthesizes whiskers in matrixes, avoiding complicated mixing procedures and fabricating composites with excellent mechanical properties [9–11]. In this work, an in situ synthesis technology is used to synthesize a composite powder for fabricating TiCx N1−x whisker toughening alumina matrix ceramic tool material. Various TiO2 :C molar ratios and synthesis temperatures are experimentally used. The yield and
∗ Corresponding author at: School of Mechanical and Electrical Engineering, Weifang University, Weifang 261061, China. Tel.: +86 536 8785603; fax: +86 536 8785603. E-mail address: sdwfl[email protected] (B.Q. Liu). 0254-0584/$ – see front matter © 2008 Elsevier B.V. All rights reserved. doi:10.1016/j.matchemphys.2008.08.024
morphology of the whiskers, as well as the composition of the composite powder, are studied. 2. Experimental procedure Commercial ␣-Al2 O3 with an average grain size of 0.5 m is used as the matrix powder. Commercial TiO2 , amorphous carbon, synthesis pure NaCl are used for the synthesis of TiCx N1−x whiskers. Commercial Ni with an average grain size of 2.3 m is used as the catalyst. All of the raw materials mentioned above are proportionally added to synthesize a composite powder with about 30% TiCx N1−x (calculated by TiC0.3 N0.7 ) in terms of volume. The molar ratio of TiO2 :NaCl:Ni is 1:3:0.5:0.05. The precursor mixtures, in which the molar ratio of TiO2 :C varies from 1:3, 1:4, 1:5 to 1:7, are named as AT303, AT304, AT305 and AT307, respectively. The mixtures are ball-milled for 24 h in ethanol medium. After dried and sieved, each 15 g of the mixture is put into a graphite reactor with a number of small holes on the lid to allow a controlled gas exchange between the reactor and the surrounding atmosphere, heated to the synthesis temperature in 10–12 min in a flowing nitrogen-gas atmosphere and held for 90 min duration time. The various synthesis temperatures are 125 ◦ C, 1350 ◦ C, 1450 ◦ C and 1550 ◦ C, respectively. The obtained phases are characterized by the power X-ray diffractometry (XRD). The yield and morphology of the whiskers in the synthesized composite powder are investigated by a SEM (Hitachi S-570 SEM) and a SEM (Hitachi S-2500 SEM) equipped with an energy-dispersive spectrometer (EDS).
3. Results and discussion Figs. 1 and 2 are the XRD patterns of the composite powders synthesized at various temperatures. No TiO2 can be detected by the XRD and TiCx N1−x is successfully synthesized. AlO appears at the synthesis temperature of 1250 ◦ C and AlN instead at 1550 ◦ C shown in Fig. 2. The majority of the whiskers display an ideal aspect ratio of 10–30 with a diameter of 1–3 m and a smooth surface shown in
614
B.Q. Liu et al. / Materials Chemistry and Physics 113 (2009) 613–615
Fig. 1. XRD of composite powders synthesized at 1250 ◦ C.
Fig. 3. No obviously whiskers agglomeration can be observed. However, the agglomerations of ␣-Al2 O3 grains can be noted shown in Fig. 3. Such agglomerations can be smashed by moderately dry ballmilled [11], therefore, will not affect the mechanical properties of the tool material. Some whiskers are terminated by a spherical end with a high content of Ni shown in Fig. 4 and Fig. 5, illustrating that the growth of TiCx N1−x whiskers starts from Ni droplets [12]. Some clusters of superfine powder with a nano-scale diameter can be observed either among the alumina grain or adhere to the synthesized whiskers shown in Fig. 3. Such clusters of powder are thought to be the carbon remnants that will severely decrease the density and mechanical properties of the tool material [11]. However, they can be removed by a mixture of water and organic solvent [1]. SEM photographs show that the highest yield of TiCx N1−x whisker occurs at the synthesis temperature of 1250 ◦ C shown in Fig. 3, indicating that low synthesis temperature is more suitable for the growth of TiCx N1−x whiskers. However, high synthesis temperature can increase the compound carbon content in TiCx N1−x whiskers. Comparing the XRD patterns of AT303 from 1250 ◦ C to 1550 ◦ C, the value of the longest line, which is 2.1224, 2.1291, 2.1368 and 2.1329 in turn, exhibits a trend of the x value changing from 0.2 to 0.3. Comparing the XRD patterns of composite powders synthesized at the same temperature (i.e. at 1250 ◦ C), no obvious different x value can be confirmed, indicating that the compound carbon content in TiCx N1−x depends mainly on the synthesis temperature and not on the molar ratio of TiO2 :C in the precursor mixture.
However, moderate molar ratio of TiO2 :C helps to increase the yield of TiCx N1−x whisker [1]. SEM photographs show that there is few whisker in AT303 at the whole synthesis temperature range. Obviously much more whiskers can be observed in AT304 and no apparently higher whisker yield can be confirmed when the carbon loading is further increased to 1:5 and 1:7, indicating that the molar ratio 1:4 is enough for the growth of TiCx N1−x whiskers. The synthesis of AlO and AlN indicates that a carbothermal reduction process can also take place between Al2 O3 and carbon in a nitrogen-gas atmosphere. However, no TiO2 remnant can be
Fig. 2. XRD of AT303 at various temperatures.
Fig. 4. A whisker terminated by a spherical end.
Fig. 3. TiCx N1−x whiskers in Al2 O3 matrix synthesized at 1250 ◦ C.
B.Q. Liu et al. / Materials Chemistry and Physics 113 (2009) 613–615
615
cessfully synthesized. The majority of TiCx N1−x whiskers in the powder has an ideal aspect ratio of 10–30 with a diameter of 1–3 m. The molar ratio of TiO2 :C 1:4 and low synthesis temperature such as 1250 ◦ C are more suitable for the growth of TiCx N1−x whiskers. The compound carbon fraction in TiCx N1−x increases at high synthesis temperature. The carbothermal reduction process can also take place between Al2 O3 and carbon in a nitrogen-gas atmosphere. However, the presence of large amount of ␣-Al2 O3 matrix powder has little effect on the growth of TiCx N1−x whiskers. Acknowledgements This project is supported by National Outstanding Young Scholar Science Foundation of NSFC (50625517) and Encouragement Foundation for Distinguished Young Scientist of Shandong Province (2006BS05013). References
Fig. 5. EDS pattern for point “1”.
detected at the whole synthesis temperature range, indicating a preferential reaction between TiO2 and carbon. As a result, no significant influence on the growth of TiCx N1−x whiskers by the present of ␣-Al2 O3 matrix powder can be noted. 4. Conclusions An in situ growth TiCx N1−x whiskers toughening Al2 O3 ceramic matrix composite powder for fabricating cutting tools is suc-
[1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12]
N. Ahlen, M. Johnsson, M. Nygren, J. Mater. Sci. Lett. 18 (1999) 1071–1074. L. Sun, J.S. Pan, Mater. Lett. 53 (2002) 63–67. Z. Zhao, M. Johnsson, Z.J. Shen, Mater. Res. Bull. 37 (2002) 1175–1187. E. Laarz, M. Carlsson, B. Vivien, M. Johnsson, M. Nygren, L. Bergstrom, J. Eur. Ceram. Soc. 21 (2001) 1027–1035. J.X. Deng, Z.Q. Li, X. Ai, Mater. Rev. 5 (1994) 72–75, (in Chinese). Y.Q. Wu, Y.F. Zhang, J.K. Guo, Mater. Rev. 14 (2000) 20–22, (in Chinese). G.J. Zhang, Z.Z. Jin, Mater. Rev. 2 (1996) 62–65, (in Chinese). G.J. Zhang, Z.Z. Jin, X.M. Yue, Mater. Rev. 11 (1997) 1–4, (in Chinese). L. Mariappan, T.S. Kannan, A.M. Umarji, Mater. Chem. Phys. 75 (2002) 284–290. B.Q. Liu, C.Z. Huang, X.Y. Lu, M.L. Gu, H.L. Liu, Ceram. Int. 33 (2007) 1475–1480. B.Q. Liu, C.Z. Huang, M.L. Gu, H.T. Zhu, H.L. Liu, Mater. Sci. Eng. A 460/461 (2007) 146–148. N. Ahlen, M. Johnsson, M. Nygren, J. Am. Ceram. Soc. 79 (1996) 2803–2808.
Contents lists available at ScienceDirect
Materials Chemistry and Physics journal homepage: www.elsevier.com/locate/matchemphys
In situ growth of TiCx N1−x whiskers in Al2 O3 matrix for ceramic cutting tools B.Q. Liu a,b,∗ , C.Z. Huang b , M.L. Gu c , H.L. Liu b a
School of Mechanical and Electrical Engineering, Weifang University, Weifang 261061, China Center for Advanced Jet Engineering Technologies (CaJET), School of Mechanical Engineering, Shandong University, Jinan 250061, China c School of Mechanical Engineering, Hebei University of Technology, Tianjin 300130, China b
a r t i c l e
i n f o
Article history: Received 12 December 2007 Accepted 9 August 2008 Keywords: TiCx N1−x whisker ␣-Al2 O3 In situ growth Carbothermal reduction process
a b s t r a c t For resolving the dispersing problem of whiskers and fabricating cutting tool materials with excellent properties, an in situ growth technology is used to directly synthesize TiCx N1−x whiskers in ␣-Al2 O3 matrix by a carbothermal reduction process at a temperature range of 1250–1550 ◦ C. The raw materials are consisted of TiO2 , carbon, nickel, and NaCl. Various molar ratios from 1:3, 1:4, 1:5 to 1:7 of TiO2 :C are experimentally used. For the molar ratio 1:3, a few whiskers can be found only at the synthesis temperature of 1550 ◦ C. For the other molar ratios, large amount of whiskers can be observed at the whole synthesis temperature range. The highest yield of whisker is observed when the synthesis temperature is 1250 ◦ C and the molar ratio of TiO2 :C is 1:4. The compound AlO appears at 1250 ◦ C and AlN instead at 1550 ◦ C. The majority of the synthesized whiskers display an ideal aspect ratio of 10–30 with a diameter of 1–3 m. No obviously influence on the whiskers growth by the present of ␣-Al2 O3 matrix powder can be noted. © 2008 Elsevier B.V. All rights reserved.
1. Introduction Due to their hardness and strength, whiskers of transition metal carbides, carbonitrides and nitrides are highly interesting as reinforcing materials in ceramics for cutting tools and other wear-resistant applications [1–4]. However, well dispersing whiskers into a ceramic matrix is very difficult and the agglomerations of these whiskers will severely decrease the density and mechanical properties of the composite [5]. Therefore, new fabrication strategies for whisker toughening ceramic tool materials should be developed. Due to the advantages such as simplifying the process, decreasing the cost and expecting unique properties by unique microstructures, in situ synthesis technology has been an important fabricating strategy for composites [6–8]. The application of such a technology on whisker toughening ceramic tool materials directly synthesizes whiskers in matrixes, avoiding complicated mixing procedures and fabricating composites with excellent mechanical properties [9–11]. In this work, an in situ synthesis technology is used to synthesize a composite powder for fabricating TiCx N1−x whisker toughening alumina matrix ceramic tool material. Various TiO2 :C molar ratios and synthesis temperatures are experimentally used. The yield and
∗ Corresponding author at: School of Mechanical and Electrical Engineering, Weifang University, Weifang 261061, China. Tel.: +86 536 8785603; fax: +86 536 8785603. E-mail address: sdwfl[email protected] (B.Q. Liu). 0254-0584/$ – see front matter © 2008 Elsevier B.V. All rights reserved. doi:10.1016/j.matchemphys.2008.08.024
morphology of the whiskers, as well as the composition of the composite powder, are studied. 2. Experimental procedure Commercial ␣-Al2 O3 with an average grain size of 0.5 m is used as the matrix powder. Commercial TiO2 , amorphous carbon, synthesis pure NaCl are used for the synthesis of TiCx N1−x whiskers. Commercial Ni with an average grain size of 2.3 m is used as the catalyst. All of the raw materials mentioned above are proportionally added to synthesize a composite powder with about 30% TiCx N1−x (calculated by TiC0.3 N0.7 ) in terms of volume. The molar ratio of TiO2 :NaCl:Ni is 1:3:0.5:0.05. The precursor mixtures, in which the molar ratio of TiO2 :C varies from 1:3, 1:4, 1:5 to 1:7, are named as AT303, AT304, AT305 and AT307, respectively. The mixtures are ball-milled for 24 h in ethanol medium. After dried and sieved, each 15 g of the mixture is put into a graphite reactor with a number of small holes on the lid to allow a controlled gas exchange between the reactor and the surrounding atmosphere, heated to the synthesis temperature in 10–12 min in a flowing nitrogen-gas atmosphere and held for 90 min duration time. The various synthesis temperatures are 125 ◦ C, 1350 ◦ C, 1450 ◦ C and 1550 ◦ C, respectively. The obtained phases are characterized by the power X-ray diffractometry (XRD). The yield and morphology of the whiskers in the synthesized composite powder are investigated by a SEM (Hitachi S-570 SEM) and a SEM (Hitachi S-2500 SEM) equipped with an energy-dispersive spectrometer (EDS).
3. Results and discussion Figs. 1 and 2 are the XRD patterns of the composite powders synthesized at various temperatures. No TiO2 can be detected by the XRD and TiCx N1−x is successfully synthesized. AlO appears at the synthesis temperature of 1250 ◦ C and AlN instead at 1550 ◦ C shown in Fig. 2. The majority of the whiskers display an ideal aspect ratio of 10–30 with a diameter of 1–3 m and a smooth surface shown in
614
B.Q. Liu et al. / Materials Chemistry and Physics 113 (2009) 613–615
Fig. 1. XRD of composite powders synthesized at 1250 ◦ C.
Fig. 3. No obviously whiskers agglomeration can be observed. However, the agglomerations of ␣-Al2 O3 grains can be noted shown in Fig. 3. Such agglomerations can be smashed by moderately dry ballmilled [11], therefore, will not affect the mechanical properties of the tool material. Some whiskers are terminated by a spherical end with a high content of Ni shown in Fig. 4 and Fig. 5, illustrating that the growth of TiCx N1−x whiskers starts from Ni droplets [12]. Some clusters of superfine powder with a nano-scale diameter can be observed either among the alumina grain or adhere to the synthesized whiskers shown in Fig. 3. Such clusters of powder are thought to be the carbon remnants that will severely decrease the density and mechanical properties of the tool material [11]. However, they can be removed by a mixture of water and organic solvent [1]. SEM photographs show that the highest yield of TiCx N1−x whisker occurs at the synthesis temperature of 1250 ◦ C shown in Fig. 3, indicating that low synthesis temperature is more suitable for the growth of TiCx N1−x whiskers. However, high synthesis temperature can increase the compound carbon content in TiCx N1−x whiskers. Comparing the XRD patterns of AT303 from 1250 ◦ C to 1550 ◦ C, the value of the longest line, which is 2.1224, 2.1291, 2.1368 and 2.1329 in turn, exhibits a trend of the x value changing from 0.2 to 0.3. Comparing the XRD patterns of composite powders synthesized at the same temperature (i.e. at 1250 ◦ C), no obvious different x value can be confirmed, indicating that the compound carbon content in TiCx N1−x depends mainly on the synthesis temperature and not on the molar ratio of TiO2 :C in the precursor mixture.
However, moderate molar ratio of TiO2 :C helps to increase the yield of TiCx N1−x whisker [1]. SEM photographs show that there is few whisker in AT303 at the whole synthesis temperature range. Obviously much more whiskers can be observed in AT304 and no apparently higher whisker yield can be confirmed when the carbon loading is further increased to 1:5 and 1:7, indicating that the molar ratio 1:4 is enough for the growth of TiCx N1−x whiskers. The synthesis of AlO and AlN indicates that a carbothermal reduction process can also take place between Al2 O3 and carbon in a nitrogen-gas atmosphere. However, no TiO2 remnant can be
Fig. 2. XRD of AT303 at various temperatures.
Fig. 4. A whisker terminated by a spherical end.
Fig. 3. TiCx N1−x whiskers in Al2 O3 matrix synthesized at 1250 ◦ C.
B.Q. Liu et al. / Materials Chemistry and Physics 113 (2009) 613–615
615
cessfully synthesized. The majority of TiCx N1−x whiskers in the powder has an ideal aspect ratio of 10–30 with a diameter of 1–3 m. The molar ratio of TiO2 :C 1:4 and low synthesis temperature such as 1250 ◦ C are more suitable for the growth of TiCx N1−x whiskers. The compound carbon fraction in TiCx N1−x increases at high synthesis temperature. The carbothermal reduction process can also take place between Al2 O3 and carbon in a nitrogen-gas atmosphere. However, the presence of large amount of ␣-Al2 O3 matrix powder has little effect on the growth of TiCx N1−x whiskers. Acknowledgements This project is supported by National Outstanding Young Scholar Science Foundation of NSFC (50625517) and Encouragement Foundation for Distinguished Young Scientist of Shandong Province (2006BS05013). References
Fig. 5. EDS pattern for point “1”.
detected at the whole synthesis temperature range, indicating a preferential reaction between TiO2 and carbon. As a result, no significant influence on the growth of TiCx N1−x whiskers by the present of ␣-Al2 O3 matrix powder can be noted. 4. Conclusions An in situ growth TiCx N1−x whiskers toughening Al2 O3 ceramic matrix composite powder for fabricating cutting tools is suc-
[1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12]
N. Ahlen, M. Johnsson, M. Nygren, J. Mater. Sci. Lett. 18 (1999) 1071–1074. L. Sun, J.S. Pan, Mater. Lett. 53 (2002) 63–67. Z. Zhao, M. Johnsson, Z.J. Shen, Mater. Res. Bull. 37 (2002) 1175–1187. E. Laarz, M. Carlsson, B. Vivien, M. Johnsson, M. Nygren, L. Bergstrom, J. Eur. Ceram. Soc. 21 (2001) 1027–1035. J.X. Deng, Z.Q. Li, X. Ai, Mater. Rev. 5 (1994) 72–75, (in Chinese). Y.Q. Wu, Y.F. Zhang, J.K. Guo, Mater. Rev. 14 (2000) 20–22, (in Chinese). G.J. Zhang, Z.Z. Jin, Mater. Rev. 2 (1996) 62–65, (in Chinese). G.J. Zhang, Z.Z. Jin, X.M. Yue, Mater. Rev. 11 (1997) 1–4, (in Chinese). L. Mariappan, T.S. Kannan, A.M. Umarji, Mater. Chem. Phys. 75 (2002) 284–290. B.Q. Liu, C.Z. Huang, X.Y. Lu, M.L. Gu, H.L. Liu, Ceram. Int. 33 (2007) 1475–1480. B.Q. Liu, C.Z. Huang, M.L. Gu, H.T. Zhu, H.L. Liu, Mater. Sci. Eng. A 460/461 (2007) 146–148. N. Ahlen, M. Johnsson, M. Nygren, J. Am. Ceram. Soc. 79 (1996) 2803–2808.