- Email: [email protected]
The 873 K isothermal section of La–Ni–Cr ternary system phase diagram
Journal of Alloys and Compounds 376 (2004) 122–124
The 873 K isothermal section of La–Ni–Cr ternary system phase diagram Yinghong Zhuang∗ , Junxia Lü, Jingqi Liu, Cuiyun He, Jianlin Yang Institute of Materials Science, Guangxi University, Nanning, Guangxi 530004, PR China Received 19 November 2003; received in revised form 22 December 2003; accepted 22 December 2003
Abstract The 873 K isothermal section of La–Ni–Cr ternary system phase diagram was investigated by X-ray powder diffraction, differential thermal analysis and electron microscopy techniques. It is composed of 10 single-phase regions, 17 two-phase regions and 8 three-phase regions. At 873 K, the existence of ternary compounds has not been observed in this isothermal section. The maximum solid solubility of Ni in Cr is about 3 at.% Ni, and of Cr in Ni, LaNi5 , La2 Ni7 , LaNi3 , La2 Ni3 , LaNi, La7 Ni3 , is about 35, 20, 15, 8, 9, 9 and 6 at.% Cr, respectively. A solid solubility of Cr in the La7 Ni16 phase has not been observed. © 2004 Elsevier B.V. All rights reserved. Keywords: Phase diagram; La–Ni–Cr ternary system; X-ray diffraction
1. Introduction Phase diagrams, as a tool for advanced materials design, are the “road maps”, that guide and direct us to our numerous goals in fabrication, development, heat treatment, properties, alloy design and basic science. The La–Ni phase diagram is very useful for research in hydrogen storage alloys. LaNi5 -based hydrogen storage alloys are being extensively used as metal hydride battery electrodes for their reversible hydrogen absorption–desorption capability and rapid reaction speed at room temperature and under the usual atmospheric pressure. However, the addition of Co to these LaNi5 -based electrodes greatly increases the price which is unfavorable for use in electric vehicle. Some cheap transitional elements, such as Si, Cu, Fe, Cr, Zn, Sn, may improve the electrode properties and lower the price by partially or completely replacing Co. As a contribution of our systematic study of the La–Ni system [1–4], this paper describes the 873 K isothermal section of the phase diagram of the La–Ni–Cr ternary system. The La–Ni binary phase diagram is taken from [5]. At 873 K eight intermetallic compounds were reported to exist: LaNi5 , La2 Ni7 , LaNi3 , LaNi2 , La2 Ni3 , LaNi, La7 Ni3 and ∗ Corresponding author. Tel.: +86-771-3233530; fax: +86-771-3233530. E-mail address: [email protected] (Y. Zhuang).
0925-8388/$ – see front matter © 2004 Elsevier B.V. All rights reserved. doi:10.1016/j.jallcom.2003.12.027
La3 Ni, while in [1–4] only seven of the above compounds are claimed. The X-ray pattern of the La3 Ni compound is regarded as a combination of the La and La7 Ni3 patterns. In [6,7] it is thought that the LaNi2 compound is a high temperature phase, and transforms into La7 Ni16 under 1003 K. The Cr–Ni binary phase diagram was proposed by Nash [8]. Two intermetallic compounds, Cr7 Ni3 [9] and Cr3 Ni2 [10], were reported. In [11,12] the La–Cr binary phase diagram is described. No compound is reported. By referring to many references, we also did not find any compound. The existence of ternary compounds has not been observed in this isothermal section. Up to now, no data regarding the ternary equilibrium diagram of the La–Ni–Cr system was found in the literature.
2. Experimental details In the present paper, the purity of lanthanum, nickel, chromium is 99.9, 99.99 and 99.95%, respectively. One hundred and fifty-one samples were prepared in an arc furnace and melted three times under an atmosphere of purified argon, each sample weighing 3 g. All samples were sealed in evacuated quartz tubes for homogenization annealing. The heat treatment temperature was determined according to the binary La–Ni phase diagram. The samples which contained less than 25 at.% La were homogenized at 1173 K for 20
Y. Zhuang et al. / Journal of Alloys and Compounds 376 (2004) 122–124
123
days, then they were cooled at a rate of about 10,000/h to 873 K for 20 days and quenched into liquid nitrogen. The X-ray diffraction (XRD) analyses were performed with powder on a Rigaku 3105 X-ray diffractometer (Mo K␣, Zr filter) and on a Rigaku D/Max 2500PC X-ray diffractometer (Cu K␣1 , monochromator) using JADE5 software [13]. The differential thermal analysis (DTA) experiment was studied in differential thermal analyzer produced in Perkin-Elmer.
3. Results and discussion 3.1. Phase analysis The compounds Cr7 Ni3 [9] (tetragonal, P42 /mnm, a = 8.71 nm, c = 4.49 nm) and Cr3 Ni2 [10] (tetragonal, P42 /mnm, a = 8.82 nm, c = 4.58 nm) were reported. In the present work, we prepared many samples around them, but we did not find their existence by X-ray diffraction. So we conclude that the Cr7 Ni3 and Cr3 Ni2 compound do not exist under our experimental conditions. In view of the difference between [5] and [1–4] about the La–Ni binary compound, we prepared a series of alloy samples in the La–Ni binary system. The XRD analysis showed that the XRD patterns of the samples near the composition of La3 Ni were obviously composed of the patterns of La and La7 Ni3 , and the XRD patterns of the samples near the composition of LaNi2 were obviously composed of the patterns of La2 Ni3 and La7 Ni16 . So we drew the same conclusion as in [1–4]. The crystal structure and lattice parameter data for the compounds of the La–Ni–Cr ternary system can be found in [14].
Fig. 1. The 873 K isothermal section of the phase diagram of La–Ni–Cr ternary system: (䊊) three-phase region.
4. Conclusion At 873 K, the isothermal section of the phase diagram of the La–Ni–Cr ternary system consists of 10 single-phase regions, 17 two-phase regions and 8 three-phase regions. The 10 single-phase regions are La, Ni, Cr, LaNi5 , La2 Ni7 , LaNi3 , La7 Ni16 , La2 Ni3 , LaNi, La7 Ni3 . The nine two-phase regions are Cr + Ni, Ni + LaNi5 , LaNi5 + La2 Ni7 , La2 Ni7 + LaNi3 , LaNi3 +La7 Ni16 , La7 Ni16 +La2 Ni3 , La2 Ni3 +LaNi, LaNi + La7 Ni3 , La7 Ni3 + La. The eight three-phase regions are Ni+LaNi5 +Cr, LaNi5 +La2 Ni7 +Cr, La2 Ni7 +LaNi3 + Cr, LaNi3 +La7 Ni16 +Cr, La7 Ni16 +La2 Ni3 +Cr, La2 Ni3 + LaNi + Cr, LaNi + La7 Ni3 + Cr, La7 Ni3 + La + Cr. No ternary compound was found.
Acknowledgements 3.2. Solid solubility The X-ray diffraction analysis shows that a certain amount of Ni, Cr atoms can replace each other to form single-phase regions. The maximum solid solubility of Ni in Cr is about 3 at.% Ni, while the maximum solid solubility of Cr in Ni is about 35 at.% Cr by using the vanishing-phase method at 873 K. The results obtained are consistent with the data reported in [8]. The maximum solid solubility of Cr in LaNi5 , La2 Ni7 , LaNi3 , La2 Ni3 , LaNi, and La7 Ni3 is 20, 15, 8, 9, 9 and 6 at.% Cr, respectively. Any solid solubility in other phase has not been observed. 3.3. Isothermal section at 873 K From the comprehensive consideration of XRD analysis of the 151 alloy samples, we confirmed the existence of seven binary compounds, namely LaNi5 , La2 Ni7 , LaNi3 , La7 Ni16 , La2 Ni3 , LaNi, La7 Ni3 at 873 K. The isothermal section of the phase diagram of the ternary system La–Ni–Cr was determined at 873 K (Fig. 1).
The work was jointly supported by the National Natural Science Foundation of China and the National Science Foundation of Guangxi. References [1] J. Liu, K. Geng, J. Alloys Compd. 312 (2000) 121–123. [2] H. Zhou, Y. Zhu, J. Liu, Y. Zhuang, S. Yuan, J. Alloys Compd. 345 (2002) 167–169. [3] Y. Zhuang, H. Deng, J. Liu, Q. Yao, J. Alloys Compd. 363 (2004) 228–231. [4] H. Zhou, Q. Yao, Y. Zhuang, J. Alloys Compd., in press. [5] Y.Y. Pan, P. Nash, in: T.B. Massalski, P.R. Subramanian, H. Okamoto, L. Kacprzak (Eds.), Binary Alloy Phase Diagrams, 2nd ed., ASM International, Materials Park, OH, 1991, pp. 2406–2408. [6] A.V. Klimyenko, J. Seuntjens, L.L. Miller, B.J. Beaudry, R.A. Jacobson, K.A. Gschneidner Jr., J. Less-Common Met. 144 (1988) 133–141. [7] V. Paul-Boncour, A. Percheron-Guegan, M. Diaf, J.C. Achard, J. Less-Common Met. 131 (1987) 201–208. [8] P. Nash, Binary Alloy Phase Diagrams, 2nd ed., ASM International, Materials Park, OH, 1991, pp. 1298–1302.
124
Y. Zhuang et al. / Journal of Alloys and Compounds 376 (2004) 122–124
[9] Powder Diffraction File, International Center for Diffraction Data, 1999. [10] Alphabetical Indexes Powder Diffraction File, International Center for Diffraction Data Sets 1–46, 1996, p. 180. [11] R.P. Elliott, Constitution of Binary Alloys, First Supplement, McGraw-Hill, New York, 1965, p. 349.
[12] V.N. Svechnikov, V.G. Ivanchenko, G.F. Kobzenko, Diagramm’ Sostoyaniya Metallicheskikh Sistem, 27 (1981) 60–62 (in Russian). [13] Powder Diffraction File on Rigaku D/Max 2500PC X-ray diffractometer (Cu K␣1 , monochromator) using JADE5 software. [14] P. Villars, Crystallographic data for intermetallic phases, in: Pearson’s Handbook, Desk Edition, ASM, Materials Park, OH, 1997.
The 873 K isothermal section of La–Ni–Cr ternary system phase diagram Yinghong Zhuang∗ , Junxia Lü, Jingqi Liu, Cuiyun He, Jianlin Yang Institute of Materials Science, Guangxi University, Nanning, Guangxi 530004, PR China Received 19 November 2003; received in revised form 22 December 2003; accepted 22 December 2003
Abstract The 873 K isothermal section of La–Ni–Cr ternary system phase diagram was investigated by X-ray powder diffraction, differential thermal analysis and electron microscopy techniques. It is composed of 10 single-phase regions, 17 two-phase regions and 8 three-phase regions. At 873 K, the existence of ternary compounds has not been observed in this isothermal section. The maximum solid solubility of Ni in Cr is about 3 at.% Ni, and of Cr in Ni, LaNi5 , La2 Ni7 , LaNi3 , La2 Ni3 , LaNi, La7 Ni3 , is about 35, 20, 15, 8, 9, 9 and 6 at.% Cr, respectively. A solid solubility of Cr in the La7 Ni16 phase has not been observed. © 2004 Elsevier B.V. All rights reserved. Keywords: Phase diagram; La–Ni–Cr ternary system; X-ray diffraction
1. Introduction Phase diagrams, as a tool for advanced materials design, are the “road maps”, that guide and direct us to our numerous goals in fabrication, development, heat treatment, properties, alloy design and basic science. The La–Ni phase diagram is very useful for research in hydrogen storage alloys. LaNi5 -based hydrogen storage alloys are being extensively used as metal hydride battery electrodes for their reversible hydrogen absorption–desorption capability and rapid reaction speed at room temperature and under the usual atmospheric pressure. However, the addition of Co to these LaNi5 -based electrodes greatly increases the price which is unfavorable for use in electric vehicle. Some cheap transitional elements, such as Si, Cu, Fe, Cr, Zn, Sn, may improve the electrode properties and lower the price by partially or completely replacing Co. As a contribution of our systematic study of the La–Ni system [1–4], this paper describes the 873 K isothermal section of the phase diagram of the La–Ni–Cr ternary system. The La–Ni binary phase diagram is taken from [5]. At 873 K eight intermetallic compounds were reported to exist: LaNi5 , La2 Ni7 , LaNi3 , LaNi2 , La2 Ni3 , LaNi, La7 Ni3 and ∗ Corresponding author. Tel.: +86-771-3233530; fax: +86-771-3233530. E-mail address: [email protected] (Y. Zhuang).
0925-8388/$ – see front matter © 2004 Elsevier B.V. All rights reserved. doi:10.1016/j.jallcom.2003.12.027
La3 Ni, while in [1–4] only seven of the above compounds are claimed. The X-ray pattern of the La3 Ni compound is regarded as a combination of the La and La7 Ni3 patterns. In [6,7] it is thought that the LaNi2 compound is a high temperature phase, and transforms into La7 Ni16 under 1003 K. The Cr–Ni binary phase diagram was proposed by Nash [8]. Two intermetallic compounds, Cr7 Ni3 [9] and Cr3 Ni2 [10], were reported. In [11,12] the La–Cr binary phase diagram is described. No compound is reported. By referring to many references, we also did not find any compound. The existence of ternary compounds has not been observed in this isothermal section. Up to now, no data regarding the ternary equilibrium diagram of the La–Ni–Cr system was found in the literature.
2. Experimental details In the present paper, the purity of lanthanum, nickel, chromium is 99.9, 99.99 and 99.95%, respectively. One hundred and fifty-one samples were prepared in an arc furnace and melted three times under an atmosphere of purified argon, each sample weighing 3 g. All samples were sealed in evacuated quartz tubes for homogenization annealing. The heat treatment temperature was determined according to the binary La–Ni phase diagram. The samples which contained less than 25 at.% La were homogenized at 1173 K for 20
Y. Zhuang et al. / Journal of Alloys and Compounds 376 (2004) 122–124
123
days, then they were cooled at a rate of about 10,000/h to 873 K for 20 days and quenched into liquid nitrogen. The X-ray diffraction (XRD) analyses were performed with powder on a Rigaku 3105 X-ray diffractometer (Mo K␣, Zr filter) and on a Rigaku D/Max 2500PC X-ray diffractometer (Cu K␣1 , monochromator) using JADE5 software [13]. The differential thermal analysis (DTA) experiment was studied in differential thermal analyzer produced in Perkin-Elmer.
3. Results and discussion 3.1. Phase analysis The compounds Cr7 Ni3 [9] (tetragonal, P42 /mnm, a = 8.71 nm, c = 4.49 nm) and Cr3 Ni2 [10] (tetragonal, P42 /mnm, a = 8.82 nm, c = 4.58 nm) were reported. In the present work, we prepared many samples around them, but we did not find their existence by X-ray diffraction. So we conclude that the Cr7 Ni3 and Cr3 Ni2 compound do not exist under our experimental conditions. In view of the difference between [5] and [1–4] about the La–Ni binary compound, we prepared a series of alloy samples in the La–Ni binary system. The XRD analysis showed that the XRD patterns of the samples near the composition of La3 Ni were obviously composed of the patterns of La and La7 Ni3 , and the XRD patterns of the samples near the composition of LaNi2 were obviously composed of the patterns of La2 Ni3 and La7 Ni16 . So we drew the same conclusion as in [1–4]. The crystal structure and lattice parameter data for the compounds of the La–Ni–Cr ternary system can be found in [14].
Fig. 1. The 873 K isothermal section of the phase diagram of La–Ni–Cr ternary system: (䊊) three-phase region.
4. Conclusion At 873 K, the isothermal section of the phase diagram of the La–Ni–Cr ternary system consists of 10 single-phase regions, 17 two-phase regions and 8 three-phase regions. The 10 single-phase regions are La, Ni, Cr, LaNi5 , La2 Ni7 , LaNi3 , La7 Ni16 , La2 Ni3 , LaNi, La7 Ni3 . The nine two-phase regions are Cr + Ni, Ni + LaNi5 , LaNi5 + La2 Ni7 , La2 Ni7 + LaNi3 , LaNi3 +La7 Ni16 , La7 Ni16 +La2 Ni3 , La2 Ni3 +LaNi, LaNi + La7 Ni3 , La7 Ni3 + La. The eight three-phase regions are Ni+LaNi5 +Cr, LaNi5 +La2 Ni7 +Cr, La2 Ni7 +LaNi3 + Cr, LaNi3 +La7 Ni16 +Cr, La7 Ni16 +La2 Ni3 +Cr, La2 Ni3 + LaNi + Cr, LaNi + La7 Ni3 + Cr, La7 Ni3 + La + Cr. No ternary compound was found.
Acknowledgements 3.2. Solid solubility The X-ray diffraction analysis shows that a certain amount of Ni, Cr atoms can replace each other to form single-phase regions. The maximum solid solubility of Ni in Cr is about 3 at.% Ni, while the maximum solid solubility of Cr in Ni is about 35 at.% Cr by using the vanishing-phase method at 873 K. The results obtained are consistent with the data reported in [8]. The maximum solid solubility of Cr in LaNi5 , La2 Ni7 , LaNi3 , La2 Ni3 , LaNi, and La7 Ni3 is 20, 15, 8, 9, 9 and 6 at.% Cr, respectively. Any solid solubility in other phase has not been observed. 3.3. Isothermal section at 873 K From the comprehensive consideration of XRD analysis of the 151 alloy samples, we confirmed the existence of seven binary compounds, namely LaNi5 , La2 Ni7 , LaNi3 , La7 Ni16 , La2 Ni3 , LaNi, La7 Ni3 at 873 K. The isothermal section of the phase diagram of the ternary system La–Ni–Cr was determined at 873 K (Fig. 1).
The work was jointly supported by the National Natural Science Foundation of China and the National Science Foundation of Guangxi. References [1] J. Liu, K. Geng, J. Alloys Compd. 312 (2000) 121–123. [2] H. Zhou, Y. Zhu, J. Liu, Y. Zhuang, S. Yuan, J. Alloys Compd. 345 (2002) 167–169. [3] Y. Zhuang, H. Deng, J. Liu, Q. Yao, J. Alloys Compd. 363 (2004) 228–231. [4] H. Zhou, Q. Yao, Y. Zhuang, J. Alloys Compd., in press. [5] Y.Y. Pan, P. Nash, in: T.B. Massalski, P.R. Subramanian, H. Okamoto, L. Kacprzak (Eds.), Binary Alloy Phase Diagrams, 2nd ed., ASM International, Materials Park, OH, 1991, pp. 2406–2408. [6] A.V. Klimyenko, J. Seuntjens, L.L. Miller, B.J. Beaudry, R.A. Jacobson, K.A. Gschneidner Jr., J. Less-Common Met. 144 (1988) 133–141. [7] V. Paul-Boncour, A. Percheron-Guegan, M. Diaf, J.C. Achard, J. Less-Common Met. 131 (1987) 201–208. [8] P. Nash, Binary Alloy Phase Diagrams, 2nd ed., ASM International, Materials Park, OH, 1991, pp. 1298–1302.
124
Y. Zhuang et al. / Journal of Alloys and Compounds 376 (2004) 122–124
[9] Powder Diffraction File, International Center for Diffraction Data, 1999. [10] Alphabetical Indexes Powder Diffraction File, International Center for Diffraction Data Sets 1–46, 1996, p. 180. [11] R.P. Elliott, Constitution of Binary Alloys, First Supplement, McGraw-Hill, New York, 1965, p. 349.
[12] V.N. Svechnikov, V.G. Ivanchenko, G.F. Kobzenko, Diagramm’ Sostoyaniya Metallicheskikh Sistem, 27 (1981) 60–62 (in Russian). [13] Powder Diffraction File on Rigaku D/Max 2500PC X-ray diffractometer (Cu K␣1 , monochromator) using JADE5 software. [14] P. Villars, Crystallographic data for intermetallic phases, in: Pearson’s Handbook, Desk Edition, ASM, Materials Park, OH, 1997.