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Preparation of tin nanoparticles by solution dispersion
Materials Science and Engineering A359 (2003) 405 /407 www.elsevier.com/locate/msea
Preparation of tin nanoparticles by solution dispersion Yanbao Zhao a,b, Zhijun Zhang b,*, Hongxin Dang a,b a
State Key Laboratory of Solid Lubrication, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, Lanzhou 730000, China b Key Laboratory of Special Lubrication and Functional Materials, Henan University, Kaifeng 475002, China Received 8 March 2003; received in revised form 24 April 2003
Abstract In this paper, we report a novel solution dispersion method for preparing tin nanoparticles from bulk tin. Tin nanoparticles, with average diameter of 30 /40 nm, have the same crystal structure as the bulk tin, and the particle surface has been oxidized. In addition, tin nanoparticles show excellent antiwear properties. # 2003 Elsevier B.V. All rights reserved. Keywords: Preparation; Tin nanoparticles; Characterization; Tribological property
1. Introduction
2. Material and experimental procedures
Due to the potential application in diverse fields, metal nanoparticles have attracted great attention in recent years [1]. These ultra-fine particles often exhibit unusual physical and chemical properties that are distinct from either simple molecules or bulk materials. Current research in this area is motivated by the possible application of these unique properties. Although many methods such as metal vapor deposition [2], chemical reduction [3] and the decompsition of organometallic precursors [4] etc. have been used to prepare metal nanoparticles, all of them cannot be used to produce metal nanoparticles in large scale [5]. Therefore, a principal barrier to the widespread use nanostructured materials has been cost, and it is still arduous task to develop novel methods for preparing metal nanoparticles. Here, we describe a novel solution method to prepare tin nanoparticles, which is different from the conventional chemical reduction [6,7] or thermal decomposition [8] methods. Tin nanoparticles can be directly prepared from bulk tin, without using complex apparatus. We also provide detailed characterization to study the structure, composition, and the anti-wear properties of tin nanoparticles.
2.1. Chemicals and preparation
* Corresponding author. Tel./fax: /86-378-285-2533. E-mail address: [email protected] (Z. Zhang). 0921-5093/03/$ - see front matter # 2003 Elsevier B.V. All rights reserved. doi:10.1016/S0921-5093(03)00395-2
Analytically pure reagent tin granules (99.9% pure) and paraffin oil were purchased from Tianjin Nankai Chemical Co. and Luoyang Chemical Co., respectively. In a typical synthesis: appropriate amounts of commercial tin granules were added to 40 ml of paraffin oil, then the solution was sealed in the 100 ml three necked flasks equipped with stirring equipment, and the solution was heated above 240 8C and vigorously stirred for 10 h. After the reaction was complete, the suspension was cooled and centrifuged to obtain the dried product. 2.2. Characterization Transmission electron microscopy (TEM) and electron diffraction (ED) were carried out on a JEOL model JEM-2010Ex/S electron microscope. The sample for TEM analysis was prepared by placing a drop of colloidal solution on a copper grid coated with a carbon film. Powder X-ray diffraction measurements were performed on an X’ Pert Philips diffractometer using Cu K alpha radiation, operating at 40 kV and 40 mV. The thermal analysis (EXSTAR6000 thermal system) were conducted on the powders in the 20 /720 8C temperature range, with a heating rate of 10 8C min 1 and in flowing air. The antiwear properties were tested
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Y. Zhao et al. / Materials Science and Engineering A359 (2003) 405 /407
with a four-ball machine, under the condition of an angular velocity of 1450 rpm, ambient temperature and 30 min. The balls (diameter 12.7 mm) used in this test were made of GCr15 with an HRc of 64 /66. The base oil was analytically pure paraffin oil with boiling point above 300 8C.
3. Results and discussion 3.1. TEM and ED studies Fig. 1 shows TEM images and ED pattern (insert) of tin samples. The shape of these nanoparticles is irregular, but close to spherical. The particles have wide size distribution and the average particle diameter is in the range of 30 /40 nm. The large size distribution is naturally caused by the broad size distribution of the liquid tin droplets formed by stirring effect. Corresponding ED pattern (insert) consists of two sharp rings and two faint rings. The rings can be indexed according to metallic tin and tin oxide phase. The d spacing values (dhkl ) of 0.318 and 0.1760 nm calculated from the ED rings are readily assigned to the 001 crystal plane of tin and 112 crystal planes of SnO, respectively. The faint rings with plane distances of 0.264 and 0.239 nm are consistent with (006) and (115) planes of SnO2. ED data indicate that tin nanoparticles have a crystalline tin core with a mixed tin oxide shell. 3.2. XRD studies In order to further confirm the crystalline structure of tin nanoparticles, we performed powder X-ray diffraction (XRD) measurements (Fig. 2). The XRD patterns of tin samples exhibit prominent peaks at scattering angles (2u) of 30.80, 32.20, 44.10, 45.25, and 55.90 which can be assigned to scattering from the 200, 101, 220, 211,
Fig. 1. The TEM image and ED pattern (insert) of tin nanoparticles.
Fig. 2. The XRD pattern of the prepared tin samples.
and 301 crystal planes, respectively, of body center tetragonal phase of tin. The lattice parameter for the unit cell of tin sample is calculated as a /5.80 and c / 3.16 in good agreement with the known lattice parameter for bulk b-Sn (a /5.83 and c /3.18). In addition, the sample shows additional peaks, where the scattering peak of 101 crystal planes of SnO is seen at 2u value of 30.00, and three weak and broad peaks are seen at 2u values of 26.70, 34.00 and 52.30, matching the 110, 101 and 211 crystal planes of SnO2, which indicate the formation of mixed tin oxides at the particle surface.
3.3. Thermal analysis Fig. 3 gives DTA/TG analysis of tin nanoparticles. As the temperature increases, the sample shows one endothermic peak and multiple exothermic peaks on the DTA curve. The endothermic peak is observed at 230 8C and is attributed to the melting of metal tin. In the TG curve, the sample presents two successive weight loss and one weight increase processes. The first weight loss range takes place at 150 /300 8C, and corresponding DTA curve shows no thermal effect (only tin melting), which indicate that organic molecules at the surfaces of the tin particles are weakly absorbed. The second weight
Fig. 3. DTA and TG curves of tin nanoparticles, at a heating rate of 10 8C min 1, in flowing air.
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surface oxide layer, tin droplets can be gradually separated into nanosized tin droplets, which are converted into tin nanoparticles when the temperature is reduced. 3.5. Tribological properties
Fig. 4. The relationship between the DWS of base oil and base oil plus 1.0% tin nanoparticles as a function of applied load.
loss range of 300/400 8C, accompanying two exothermic peaks, suggests a further release of solvent molecules from the surface of the tin particles. The total weight loss from room temperature to 400 8C is about 7%, which indicates that the samples contained at least 7% organic molecules. The weight increase above 400 8C, with an accompanying exothermic process, can be attributed to the oxidation of tin. According to these results, we conclude that the tin nanoparticle samples contain metal tin and organic molecules. 3.4. Proposed the mechanism for formation of tin nanopartarticles First, large metal droplets are dispersed into small droplets in solvent by stirring forces, but these small droplets are thermodynamically unstable. Since the total surface energy of the system is increasing. Therefore, the small droplets should coagulate and form large ones to reduce total surface energy of the system. However, the fresh surfaces of the tin droplets are high active and easily form tin oxide through reaction with oxygen. Once a mixed oxide layer is formed, the possibility of aggregation is suppressed. In addition, the tin oxide layer seems to adsorb solvent molecules, which might improve the stability of tin droplets in solvent. As the oxide layer thickens around the droplets, it not only can keep tin droplets isolated in the solvent, but permits cracking and fragmentation. With the presence of a
Fig. 4 gives the relationship between the diameters of wear scar (DWS) of base oil and base oil plus 1.0% tin nanoparticles as a function of applied load. For the paraffin oil, the DWS is 0.72 mm at a load of 300 N, and the system-scuffing load is below 400 N. It can be seen that the tin nanoparticles have excellent antiwear properties under the different loads. At the load of 300 N, the DWS of base oil containing 1.0% tin nanoparticles is 0.47 mm, which is large below that of base oil. With the increase in load applied, the DWS of base oil containing 1.0% tin nanoparticles is larger, but the friction system could be lubricated effectively even at 600 N; thus the tin nanoparticles have excellent antiwear properties.
4. Conclusion Tin nanoparticles can be prepared by a simple and efficient solution dispersion method, which might be suitable for many low melting point metals or alloys.
References [1] Y. Sun, Y. Xia, Science 298 (2002) 2176. [2] R.P. Andres, J.D. Bielefeld, J.I. Henderson, D.B. Janes, V.R. Kolagunta, C.P. Kubiak, W.J. Mahoney, R.G. Osifchin, Science 273 (1996) 1690. [3] A. Henglein, J. Phys. Chem. B 104 (2000) 6683. [4] C.B. Murray, S. Sun, W. Gaschler, H. Doyle, T.A. Betley, C.R. Kagan, IBM J. Res. Dev. 45 (2001) 47. [5] W.Y. Yu, H.F. Liu, Chem. Mater. 10 (1998) 1205. [6] C.S. Yang, Q. Liu, S.M. Kauzlarich, B. Phillips, Chem. Mater. 12 (2000) 983. [7] N. Avramova, N.S. Neykov, S.K. Peneva, J. Phys. D: Appl. Phys. 29 (1996) 1300. [8] C. Nayral, T. Ould-Ely, A. Maisonnat, B. Chaudret, P. Fau, L. Lescouze`res, A. Peyre-Lavigne, Adv. Mater. 11 (1999) 61.
Preparation of tin nanoparticles by solution dispersion Yanbao Zhao a,b, Zhijun Zhang b,*, Hongxin Dang a,b a
State Key Laboratory of Solid Lubrication, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, Lanzhou 730000, China b Key Laboratory of Special Lubrication and Functional Materials, Henan University, Kaifeng 475002, China Received 8 March 2003; received in revised form 24 April 2003
Abstract In this paper, we report a novel solution dispersion method for preparing tin nanoparticles from bulk tin. Tin nanoparticles, with average diameter of 30 /40 nm, have the same crystal structure as the bulk tin, and the particle surface has been oxidized. In addition, tin nanoparticles show excellent antiwear properties. # 2003 Elsevier B.V. All rights reserved. Keywords: Preparation; Tin nanoparticles; Characterization; Tribological property
1. Introduction
2. Material and experimental procedures
Due to the potential application in diverse fields, metal nanoparticles have attracted great attention in recent years [1]. These ultra-fine particles often exhibit unusual physical and chemical properties that are distinct from either simple molecules or bulk materials. Current research in this area is motivated by the possible application of these unique properties. Although many methods such as metal vapor deposition [2], chemical reduction [3] and the decompsition of organometallic precursors [4] etc. have been used to prepare metal nanoparticles, all of them cannot be used to produce metal nanoparticles in large scale [5]. Therefore, a principal barrier to the widespread use nanostructured materials has been cost, and it is still arduous task to develop novel methods for preparing metal nanoparticles. Here, we describe a novel solution method to prepare tin nanoparticles, which is different from the conventional chemical reduction [6,7] or thermal decomposition [8] methods. Tin nanoparticles can be directly prepared from bulk tin, without using complex apparatus. We also provide detailed characterization to study the structure, composition, and the anti-wear properties of tin nanoparticles.
2.1. Chemicals and preparation
* Corresponding author. Tel./fax: /86-378-285-2533. E-mail address: [email protected] (Z. Zhang). 0921-5093/03/$ - see front matter # 2003 Elsevier B.V. All rights reserved. doi:10.1016/S0921-5093(03)00395-2
Analytically pure reagent tin granules (99.9% pure) and paraffin oil were purchased from Tianjin Nankai Chemical Co. and Luoyang Chemical Co., respectively. In a typical synthesis: appropriate amounts of commercial tin granules were added to 40 ml of paraffin oil, then the solution was sealed in the 100 ml three necked flasks equipped with stirring equipment, and the solution was heated above 240 8C and vigorously stirred for 10 h. After the reaction was complete, the suspension was cooled and centrifuged to obtain the dried product. 2.2. Characterization Transmission electron microscopy (TEM) and electron diffraction (ED) were carried out on a JEOL model JEM-2010Ex/S electron microscope. The sample for TEM analysis was prepared by placing a drop of colloidal solution on a copper grid coated with a carbon film. Powder X-ray diffraction measurements were performed on an X’ Pert Philips diffractometer using Cu K alpha radiation, operating at 40 kV and 40 mV. The thermal analysis (EXSTAR6000 thermal system) were conducted on the powders in the 20 /720 8C temperature range, with a heating rate of 10 8C min 1 and in flowing air. The antiwear properties were tested
406
Y. Zhao et al. / Materials Science and Engineering A359 (2003) 405 /407
with a four-ball machine, under the condition of an angular velocity of 1450 rpm, ambient temperature and 30 min. The balls (diameter 12.7 mm) used in this test were made of GCr15 with an HRc of 64 /66. The base oil was analytically pure paraffin oil with boiling point above 300 8C.
3. Results and discussion 3.1. TEM and ED studies Fig. 1 shows TEM images and ED pattern (insert) of tin samples. The shape of these nanoparticles is irregular, but close to spherical. The particles have wide size distribution and the average particle diameter is in the range of 30 /40 nm. The large size distribution is naturally caused by the broad size distribution of the liquid tin droplets formed by stirring effect. Corresponding ED pattern (insert) consists of two sharp rings and two faint rings. The rings can be indexed according to metallic tin and tin oxide phase. The d spacing values (dhkl ) of 0.318 and 0.1760 nm calculated from the ED rings are readily assigned to the 001 crystal plane of tin and 112 crystal planes of SnO, respectively. The faint rings with plane distances of 0.264 and 0.239 nm are consistent with (006) and (115) planes of SnO2. ED data indicate that tin nanoparticles have a crystalline tin core with a mixed tin oxide shell. 3.2. XRD studies In order to further confirm the crystalline structure of tin nanoparticles, we performed powder X-ray diffraction (XRD) measurements (Fig. 2). The XRD patterns of tin samples exhibit prominent peaks at scattering angles (2u) of 30.80, 32.20, 44.10, 45.25, and 55.90 which can be assigned to scattering from the 200, 101, 220, 211,
Fig. 1. The TEM image and ED pattern (insert) of tin nanoparticles.
Fig. 2. The XRD pattern of the prepared tin samples.
and 301 crystal planes, respectively, of body center tetragonal phase of tin. The lattice parameter for the unit cell of tin sample is calculated as a /5.80 and c / 3.16 in good agreement with the known lattice parameter for bulk b-Sn (a /5.83 and c /3.18). In addition, the sample shows additional peaks, where the scattering peak of 101 crystal planes of SnO is seen at 2u value of 30.00, and three weak and broad peaks are seen at 2u values of 26.70, 34.00 and 52.30, matching the 110, 101 and 211 crystal planes of SnO2, which indicate the formation of mixed tin oxides at the particle surface.
3.3. Thermal analysis Fig. 3 gives DTA/TG analysis of tin nanoparticles. As the temperature increases, the sample shows one endothermic peak and multiple exothermic peaks on the DTA curve. The endothermic peak is observed at 230 8C and is attributed to the melting of metal tin. In the TG curve, the sample presents two successive weight loss and one weight increase processes. The first weight loss range takes place at 150 /300 8C, and corresponding DTA curve shows no thermal effect (only tin melting), which indicate that organic molecules at the surfaces of the tin particles are weakly absorbed. The second weight
Fig. 3. DTA and TG curves of tin nanoparticles, at a heating rate of 10 8C min 1, in flowing air.
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surface oxide layer, tin droplets can be gradually separated into nanosized tin droplets, which are converted into tin nanoparticles when the temperature is reduced. 3.5. Tribological properties
Fig. 4. The relationship between the DWS of base oil and base oil plus 1.0% tin nanoparticles as a function of applied load.
loss range of 300/400 8C, accompanying two exothermic peaks, suggests a further release of solvent molecules from the surface of the tin particles. The total weight loss from room temperature to 400 8C is about 7%, which indicates that the samples contained at least 7% organic molecules. The weight increase above 400 8C, with an accompanying exothermic process, can be attributed to the oxidation of tin. According to these results, we conclude that the tin nanoparticle samples contain metal tin and organic molecules. 3.4. Proposed the mechanism for formation of tin nanopartarticles First, large metal droplets are dispersed into small droplets in solvent by stirring forces, but these small droplets are thermodynamically unstable. Since the total surface energy of the system is increasing. Therefore, the small droplets should coagulate and form large ones to reduce total surface energy of the system. However, the fresh surfaces of the tin droplets are high active and easily form tin oxide through reaction with oxygen. Once a mixed oxide layer is formed, the possibility of aggregation is suppressed. In addition, the tin oxide layer seems to adsorb solvent molecules, which might improve the stability of tin droplets in solvent. As the oxide layer thickens around the droplets, it not only can keep tin droplets isolated in the solvent, but permits cracking and fragmentation. With the presence of a
Fig. 4 gives the relationship between the diameters of wear scar (DWS) of base oil and base oil plus 1.0% tin nanoparticles as a function of applied load. For the paraffin oil, the DWS is 0.72 mm at a load of 300 N, and the system-scuffing load is below 400 N. It can be seen that the tin nanoparticles have excellent antiwear properties under the different loads. At the load of 300 N, the DWS of base oil containing 1.0% tin nanoparticles is 0.47 mm, which is large below that of base oil. With the increase in load applied, the DWS of base oil containing 1.0% tin nanoparticles is larger, but the friction system could be lubricated effectively even at 600 N; thus the tin nanoparticles have excellent antiwear properties.
4. Conclusion Tin nanoparticles can be prepared by a simple and efficient solution dispersion method, which might be suitable for many low melting point metals or alloys.
References [1] Y. Sun, Y. Xia, Science 298 (2002) 2176. [2] R.P. Andres, J.D. Bielefeld, J.I. Henderson, D.B. Janes, V.R. Kolagunta, C.P. Kubiak, W.J. Mahoney, R.G. Osifchin, Science 273 (1996) 1690. [3] A. Henglein, J. Phys. Chem. B 104 (2000) 6683. [4] C.B. Murray, S. Sun, W. Gaschler, H. Doyle, T.A. Betley, C.R. Kagan, IBM J. Res. Dev. 45 (2001) 47. [5] W.Y. Yu, H.F. Liu, Chem. Mater. 10 (1998) 1205. [6] C.S. Yang, Q. Liu, S.M. Kauzlarich, B. Phillips, Chem. Mater. 12 (2000) 983. [7] N. Avramova, N.S. Neykov, S.K. Peneva, J. Phys. D: Appl. Phys. 29 (1996) 1300. [8] C. Nayral, T. Ould-Ely, A. Maisonnat, B. Chaudret, P. Fau, L. Lescouze`res, A. Peyre-Lavigne, Adv. Mater. 11 (1999) 61.