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The preparation of silver sulfide nanoparticles in lamellar liquid crystal and application to lubrication
Materials Research Bulletin 40 (2005) 575–582 www.elsevier.com/locate/matresbu
The preparation of silver sulfide nanoparticles in lamellar liquid crystal and application to lubrication Yuanhua Ding, Bing Xu, Rong Guo *, Ming Shen School of Chemistry and Chemical Engineering, Yangzhou University, Yangzhou 225002, PR China Received 26 February 2004; received in revised form 13 December 2004; accepted 1 February 2005
Abstract The silver sulfide (Ag2S) nanoparticles were prepared by the reaction of AgNO3 and Na2S in the lamellar liquid crystal (LLC) formed by Triton X-100, n-C10H21OH and H2O. The size of the particles is about 2–3 nm. The existence of Ag2S nanoparticles can improve the lubrication of the lamellar liquid crystal. # 2005 Elsevier Ltd. All rights reserved. Keywords: A. Inorganic compounds; A. Nanostructures; B. Chemical synthesis; C. X-ray diffraction; D. Mechanical properties
1. Introduction In the recent years, Ag2S particles have been used widely, and there have been many reports on their preparation, crystal structures, light absorbability, fluorescence characteristic and self-organization into 2D and 3D superlattices [1,2]. In tribology domain, Ag2S particles are often used as lubricant additive, high polymer filling and important component in surface coat [3]. Ag2S particles should also have well lubricating performance and anti-wear property. However, because Ag2S nanoparticles are easy to be oxidized in air, the Ag2S particles obtained are commonly in micron dimension, and as a result, their lubricating performance and anti-wear property are decreased. Lamellar liquid crystal (LLC) shows lubrication performance on aluminum alloy surface because of its particular lamellar structure [4–6]. Furthermore, lamellar liquid crystal can be used as a template to * Corresponding author. Tel.: +86 514 7975219; fax: +86 514 7311374. E-mail address: [email protected] (R. Guo). 0025-5408/$ – see front matter # 2005 Elsevier Ltd. All rights reserved. doi:10.1016/j.materresbull.2005.02.001
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prepare nanoparticles. If nanoparticles can exist in lamellar liquid crystal, they will make the layer in lamellar liquid crystal easy to slide, and thus, result in a better lubricating performance [7–10]. In the present paper, we prepared the nanoparticles, silver sulfide (Ag2S), by using the template of Triton X-100/n-C10H21OH/H2O lamellar liquid crystal. We also investigated the lubrication properties of the lamellar liquid crystal with the prepared nanoparticles as additive. The result shows that the existence of the nanoparticles can improve the lubrication performance of the lamellar liquid crystal.
2. Experiment 2.1. Materials Triton X-100 (Sigma, >99%), decanol (Aldrich, 99%), silver nitrate (Aldrich, 99%), sodium sulfide (Aldrich, >99%). Water used was deionized and distilled. 2.2. Determination of the lamellar liquid crystal region Samples with different compositions of Triton X-100, n-C10H21OH and H2O (or 0.2 mol/L AgNO3 or 0.1 mol/L Na2S aqueous solutions) were placed in a thermostat at (25 0.1) 8C for at least 12 h for phase equilibration. The phase boundaries of lamellar liquid crystal were verified by using a polarizing microscope (59X, Shanghai Optical Apparatus Co., China). 2.3. Small angle X-ray diffraction measurements Small angle X-ray diffraction measurements were performed by using a D/max-rc rotating X-ray diffractometer (Japan Rigaku Co.) with Ni filter and Cu radiation (l = 0.1542 nm). The applied tube voltage and the tube current were 50 kV and 180 mA, respectively. 2.4. Preparation of Ag2S nanoparticles Prepare Triton X-100/n-C10H21OH/AgNO3 aq. (0.2 mol/L) lamellar liquid crystal and Triton X-100/ n-C10H21OH/Na2S aq. (0.1 mol/L) lamellar liquid crystal. When the two lamellar liquid crystals are mixed, Ag2S nanoparticles are formed in the solvent layer of the lamellar liquid crystal. Separate the nanoparticles from the lamellar liquid crystal by high-speed centrifugation, wash them sufficiently with absolute alcohol to remove Triton X-100 and decanol, and then make them dried at vacuum for 12 h. 2.5. Characterizations of Ag2S nanoparticles The size and morphology of Ag2S nanoparticles were observed by a transmission electron microscope (Philips Tecnai-12). The structure of Ag2S nanoparticles was confirmed by X-ray diffraction measurements (D/max-rc, Japan Rigaku Co.).
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2.6. The friction and wear test The lubrication properties of the lamellar liquid crystal with and without Ag2S nanoparticles were evaluated with a high-speed ring-block wear tester at 25 8C. The rotating speed is 800 8 rpm, the test duration 180 s and the load applied 200 N. The 49 mm diametered ring used is made of SAE 2100 steel, with a HRc of 59–61. The block used is Al–Si alloy (Si, 12–15%). Before each test, the ring and block were cleaned by petroleum ether. At the end of each test, the wear scar width (WSW) was measured with a digital microscope.
3. Results and discussion 3.1. The region and structure properties of lamellar liquid crystal Fig. 1 shows the partial phase diagram of Triton X-100/n-C10H21OH/solvent system. The solid line, the dash dotted line and the dash line in Fig. 1 represent the lamellar liquid crystal regions with water, 0.2 mol/L AgNO3 aqueous solution and 0.1 mol/L Na2S aqueous solution as solvent, respectively. Obviously, AgNO3 and Na2S can decrease the stability of the lamellar liquid crystal and make the lamellar liquid crystal region reduced. The structure of the lamellar liquid crystal is illustrated in Fig. 2, in which d is the interlayer space, do the thickness of the amphiphile bilayer, and dw the thickness of the solvent layer. AgNO3 and Na2S exist mostly in the solvent layer, which provides a possibility to use lamellar liquid crystal as a template for the preparation of nanoparticles. The compositions of the lamellar liquid crystals used in this paper are shown by samples 1, 2 and 3 in Fig. 1. The interlayer space, d, of the lamellar liquid crystal is determined by small angle X-ray diffraction. A straight line is obtained by plotting d against R, the volume ratio of the solvent to the other components (Fig. 3), and then, do is
Fig. 1. Lamellar liquid crystal regions (LLC) of Triton X-100/n-C10H21OH/solvent system at 25 8C. Solvent: solid line, H2O; dash dotted line, 0.2 mol/L AgNO3 aq.; dash line, 0.1 mol/L Na2S aq.
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Fig. 2. Illustration of lamellar liquid crystal. d, interlayer space; do, thickness of the amphiphile bilayer; dw, thickness of solvent layer.
obtained by extrapolating the line to zero of the water content. As can be seen from Fig. 3, do = 3.60 nm when the weight ratio of n-C10H21OH to Triton X-100 is 17/83, and do = 3.55 nm when the ratio is 23/77. Thus, the weight ratio of the surfactant to cosurfactant has a very little influence on the thickness of amphiphile bilayer. Since d = dw + do (Fig. 2), the fact that the interlayer space d increases with water content at a given weight ratio of n-C10H21OH to Triton X-100 is because the thickness of the solvent
Fig. 3. The relationship between the interlayer space (d) and the volume ratio (R) of water/(Triton X-100 + decanol).
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Fig. 4. The relationship between the thickness of the solvent layer and the volume ration (R) of water/(Triton X-100 + decanol).
layer dw increases with water content accordingly (Fig. 4). Fig. 4 also shows the thickness of the solvent layer dw decreases with the increase of the weight ratio of n-C10H21OH to Triton X-100 at a given solvent content (Fig. 4), elucidating the increase of n-C10H21OH content can decrease the value of d. The solvent is distributed in the lamellar liquid crystal in two ways [11–14]: (1) penetrating into the amphiphile bilayer and (2) forming a solvent layer between the amphiphile bilayers. The solvent penetration P can be calculated from the following equation [13]: P¼1
@d=@R do
(1)
When the weight ratio of n-C10H21OH to Triton X-100 is 17/83, P = 52.7%, but when the weight ratio is 23/77, P = 54.7%. Thus, the penetration of water in Triton X-100/n-C10H21OH/H2O lamellar liquid crystal is high. Fig. 4 indicates that dw is very small (<3 nm). Thus, it is possible to prepare nanoparticles in the lamellar liquid crystal. 3.2. The characterization of Ag2S nanoparticles The compositions of the lamellar liquid crystals used for preparing Ag2S nanoparticles are shown by samples 1, 2 and 3 in Fig. 1. The TEM pictures of the Ag2S nanoparticles prepared in the lamellar liquid crystal are shown in Figs. 5a–c. It is clear that the particles are spherical with a size of about 2–3 nm and not significantly affected by the composition of lamellar liquid crystal. Fig. 4 shows that the thickness of the solvent layer in the lamellar liquid crystal decreases by only 0.1–0.2 nm when the weight ratio of nC10H21OH to Triton X-100 changes from 17/83 to 23/77 at a given water content; and the thickness of the solvent layer increases by only 1 nm when the volume ratio R changes from 0.40 to 1.00. Obviously, such a small change in dw cannot remarkably affect the size of Ag2S nanoparticles prepared in the lamellar liquid crystal. Fig. 6 shows that the X-ray diffraction pattern of the Ag2S nanoparticles prepared in the lamellar liquid crystal template (Fig. 6b) is identical to that of the standard sample of Ag2S (Fig. 6a).
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Fig. 5. TEM pictures of Ag2S nanoparticles. Weight ratio of Triton X-100/n-C10H21OH/H2O: (a) 50/16/34; (b) 53.4/10/36.6; (c) 63/11.8/25.2.
3.3. Lubrication properties of the lamellar liquid crystal The wear scar width on the block surface under high-speed ring-block wear tester is one of the characteristics of lubrication properties. Under the same load, the smaller the wear scar width, the better the lubrication performance. Fig. 7 shows that the wear scar width of alloy with the presence of LLC (Fig. 7a) or LLC/Ag2S nanoparticles (Fig. 7b) under a load of 200 N at a speed of 800 rotations/min increases with the solvent content in the lamellar liquid crystal, indicating the order degree of the lamellar liquid crystal decreases with the increase of the solvent content [15]. Compared with the wear scar width of block lubricated by the lamellar liquid crystal without Ag2S nanoparticles (Fig. 7a), the wear scar width of the block lubricated by the lamellar liquid crystal with Ag2S nanoparticles is reduced more remarkably (Fig. 7b), showing that the existence of Ag2S nanoparticles can improve the anti-wear
Fig. 6. X-ray diffraction spectra of Ag2S: (a) standard sample; (b) Ag2S nanoparticles prepared.
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Fig. 7. The relationship between the wear scar width and water content, wH : (a) lamellar liquid crystal; (b) LLC/Ag2S nanoparticles mixed system.
properties of the lamellar liquid crystal system. Fig. 8 shows the wear scar width of the alloy decreases with the increase of the content of Triton X-100 in the lamellar liquid crystal. This is because the order degree of the surfactant and the cosurfactant in the amphiphilc bilayer of the lamellar liquid crystal increases with the content of Triton X-100. The smaller wear scar width of the block lubricated by the lamellar liquid crystal with Ag2S nanoparticles (Fig. 8b) than that without Ag2S nanoparticles (Fig. 8a) illustrates again that the existence of Ag2S nanoparticles can make the anti-wear properties of the lamellar liquid crystal improved.
Fig. 8. The relationship between the wear scar width and Triton X-100 content, wT : (a) lamellar liquid crystal; (b) LLC/Ag2S nanoparticles mixed system.
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4. Conclusions 1. Because of the limitation of the size of the solvent layer in the lamellar liquid crystal, Ag2S nanoparticles can be obtained with a size of about 2–3 nm. 2. Ag2S nanoparticles can improve the anti-wear property of lamellar liquid crystal of Triton X-100/nC10H21OH/H2O system. Acknowledgement This work is supported by the National Natural Science Foundation of China (29733110).
References [1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12] [13] [14] [15]
L. Motte, F. Billoudet, E. Lacaze, J. Douin, M.P. Pileni, J. Phys. Chem. B 101 (1997) 138. C. Kaito, Y. Saito, K. Fujita, J. Cryst. Growth 94 (1989) 967. Q. Zhao, S. Bahadur, Wear 217 (1998) 62. S. Bhattacharya, R. Salher, J.L. Lauer, et al., Tribol. Trans. 31 (1987) 442. F.E. Lockwood, M.T. Bechaita, S.E. Friberg, ASLE Trans. 30 (1987) 539. C.S. Ma, G.Z. Li, Q. Shen, et al., J. Disp. Sci. Technol. 20 (1999) 1025. P.Q. Yan, R. Guo, M. Shen, Acta Physico-Chim. Sinica 11 (1993) 218. P.Q. Yan, R. Guo, M.C. Huang, Chin. Sci. Bull. 39 (1994) 1289. R. Guo, J. Disp. Sci. Technol. 20 (1999) 105. H.M. Yang, Z.D. Chen, X.H. Zhang, R. Guo, H.Q. Wang, Tribology 20 (2000) 214. R. Guo, Acta Physico-Chim. Sinica 7 (1991) 703. S.E. Friberg, R. Guo, A.J.I. Ward, J. Phys. Chem. 92 (1988) 7247. S.E. Friberg, R. Guo, Langmuir 4 (1988) 796. R. Guo, P.Q. Yan, Z.M. Liu, X.S. Zhu, M. Shen, Acta Chim. Sinica 10 (1994) 468. H.M. Yang, R. Guo, H.Q. Wang, Acta Physico-Chim. Sinica 16 (2000) 592.
The preparation of silver sulfide nanoparticles in lamellar liquid crystal and application to lubrication Yuanhua Ding, Bing Xu, Rong Guo *, Ming Shen School of Chemistry and Chemical Engineering, Yangzhou University, Yangzhou 225002, PR China Received 26 February 2004; received in revised form 13 December 2004; accepted 1 February 2005
Abstract The silver sulfide (Ag2S) nanoparticles were prepared by the reaction of AgNO3 and Na2S in the lamellar liquid crystal (LLC) formed by Triton X-100, n-C10H21OH and H2O. The size of the particles is about 2–3 nm. The existence of Ag2S nanoparticles can improve the lubrication of the lamellar liquid crystal. # 2005 Elsevier Ltd. All rights reserved. Keywords: A. Inorganic compounds; A. Nanostructures; B. Chemical synthesis; C. X-ray diffraction; D. Mechanical properties
1. Introduction In the recent years, Ag2S particles have been used widely, and there have been many reports on their preparation, crystal structures, light absorbability, fluorescence characteristic and self-organization into 2D and 3D superlattices [1,2]. In tribology domain, Ag2S particles are often used as lubricant additive, high polymer filling and important component in surface coat [3]. Ag2S particles should also have well lubricating performance and anti-wear property. However, because Ag2S nanoparticles are easy to be oxidized in air, the Ag2S particles obtained are commonly in micron dimension, and as a result, their lubricating performance and anti-wear property are decreased. Lamellar liquid crystal (LLC) shows lubrication performance on aluminum alloy surface because of its particular lamellar structure [4–6]. Furthermore, lamellar liquid crystal can be used as a template to * Corresponding author. Tel.: +86 514 7975219; fax: +86 514 7311374. E-mail address: [email protected] (R. Guo). 0025-5408/$ – see front matter # 2005 Elsevier Ltd. All rights reserved. doi:10.1016/j.materresbull.2005.02.001
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prepare nanoparticles. If nanoparticles can exist in lamellar liquid crystal, they will make the layer in lamellar liquid crystal easy to slide, and thus, result in a better lubricating performance [7–10]. In the present paper, we prepared the nanoparticles, silver sulfide (Ag2S), by using the template of Triton X-100/n-C10H21OH/H2O lamellar liquid crystal. We also investigated the lubrication properties of the lamellar liquid crystal with the prepared nanoparticles as additive. The result shows that the existence of the nanoparticles can improve the lubrication performance of the lamellar liquid crystal.
2. Experiment 2.1. Materials Triton X-100 (Sigma, >99%), decanol (Aldrich, 99%), silver nitrate (Aldrich, 99%), sodium sulfide (Aldrich, >99%). Water used was deionized and distilled. 2.2. Determination of the lamellar liquid crystal region Samples with different compositions of Triton X-100, n-C10H21OH and H2O (or 0.2 mol/L AgNO3 or 0.1 mol/L Na2S aqueous solutions) were placed in a thermostat at (25 0.1) 8C for at least 12 h for phase equilibration. The phase boundaries of lamellar liquid crystal were verified by using a polarizing microscope (59X, Shanghai Optical Apparatus Co., China). 2.3. Small angle X-ray diffraction measurements Small angle X-ray diffraction measurements were performed by using a D/max-rc rotating X-ray diffractometer (Japan Rigaku Co.) with Ni filter and Cu radiation (l = 0.1542 nm). The applied tube voltage and the tube current were 50 kV and 180 mA, respectively. 2.4. Preparation of Ag2S nanoparticles Prepare Triton X-100/n-C10H21OH/AgNO3 aq. (0.2 mol/L) lamellar liquid crystal and Triton X-100/ n-C10H21OH/Na2S aq. (0.1 mol/L) lamellar liquid crystal. When the two lamellar liquid crystals are mixed, Ag2S nanoparticles are formed in the solvent layer of the lamellar liquid crystal. Separate the nanoparticles from the lamellar liquid crystal by high-speed centrifugation, wash them sufficiently with absolute alcohol to remove Triton X-100 and decanol, and then make them dried at vacuum for 12 h. 2.5. Characterizations of Ag2S nanoparticles The size and morphology of Ag2S nanoparticles were observed by a transmission electron microscope (Philips Tecnai-12). The structure of Ag2S nanoparticles was confirmed by X-ray diffraction measurements (D/max-rc, Japan Rigaku Co.).
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2.6. The friction and wear test The lubrication properties of the lamellar liquid crystal with and without Ag2S nanoparticles were evaluated with a high-speed ring-block wear tester at 25 8C. The rotating speed is 800 8 rpm, the test duration 180 s and the load applied 200 N. The 49 mm diametered ring used is made of SAE 2100 steel, with a HRc of 59–61. The block used is Al–Si alloy (Si, 12–15%). Before each test, the ring and block were cleaned by petroleum ether. At the end of each test, the wear scar width (WSW) was measured with a digital microscope.
3. Results and discussion 3.1. The region and structure properties of lamellar liquid crystal Fig. 1 shows the partial phase diagram of Triton X-100/n-C10H21OH/solvent system. The solid line, the dash dotted line and the dash line in Fig. 1 represent the lamellar liquid crystal regions with water, 0.2 mol/L AgNO3 aqueous solution and 0.1 mol/L Na2S aqueous solution as solvent, respectively. Obviously, AgNO3 and Na2S can decrease the stability of the lamellar liquid crystal and make the lamellar liquid crystal region reduced. The structure of the lamellar liquid crystal is illustrated in Fig. 2, in which d is the interlayer space, do the thickness of the amphiphile bilayer, and dw the thickness of the solvent layer. AgNO3 and Na2S exist mostly in the solvent layer, which provides a possibility to use lamellar liquid crystal as a template for the preparation of nanoparticles. The compositions of the lamellar liquid crystals used in this paper are shown by samples 1, 2 and 3 in Fig. 1. The interlayer space, d, of the lamellar liquid crystal is determined by small angle X-ray diffraction. A straight line is obtained by plotting d against R, the volume ratio of the solvent to the other components (Fig. 3), and then, do is
Fig. 1. Lamellar liquid crystal regions (LLC) of Triton X-100/n-C10H21OH/solvent system at 25 8C. Solvent: solid line, H2O; dash dotted line, 0.2 mol/L AgNO3 aq.; dash line, 0.1 mol/L Na2S aq.
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Fig. 2. Illustration of lamellar liquid crystal. d, interlayer space; do, thickness of the amphiphile bilayer; dw, thickness of solvent layer.
obtained by extrapolating the line to zero of the water content. As can be seen from Fig. 3, do = 3.60 nm when the weight ratio of n-C10H21OH to Triton X-100 is 17/83, and do = 3.55 nm when the ratio is 23/77. Thus, the weight ratio of the surfactant to cosurfactant has a very little influence on the thickness of amphiphile bilayer. Since d = dw + do (Fig. 2), the fact that the interlayer space d increases with water content at a given weight ratio of n-C10H21OH to Triton X-100 is because the thickness of the solvent
Fig. 3. The relationship between the interlayer space (d) and the volume ratio (R) of water/(Triton X-100 + decanol).
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Fig. 4. The relationship between the thickness of the solvent layer and the volume ration (R) of water/(Triton X-100 + decanol).
layer dw increases with water content accordingly (Fig. 4). Fig. 4 also shows the thickness of the solvent layer dw decreases with the increase of the weight ratio of n-C10H21OH to Triton X-100 at a given solvent content (Fig. 4), elucidating the increase of n-C10H21OH content can decrease the value of d. The solvent is distributed in the lamellar liquid crystal in two ways [11–14]: (1) penetrating into the amphiphile bilayer and (2) forming a solvent layer between the amphiphile bilayers. The solvent penetration P can be calculated from the following equation [13]: P¼1
@d=@R do
(1)
When the weight ratio of n-C10H21OH to Triton X-100 is 17/83, P = 52.7%, but when the weight ratio is 23/77, P = 54.7%. Thus, the penetration of water in Triton X-100/n-C10H21OH/H2O lamellar liquid crystal is high. Fig. 4 indicates that dw is very small (<3 nm). Thus, it is possible to prepare nanoparticles in the lamellar liquid crystal. 3.2. The characterization of Ag2S nanoparticles The compositions of the lamellar liquid crystals used for preparing Ag2S nanoparticles are shown by samples 1, 2 and 3 in Fig. 1. The TEM pictures of the Ag2S nanoparticles prepared in the lamellar liquid crystal are shown in Figs. 5a–c. It is clear that the particles are spherical with a size of about 2–3 nm and not significantly affected by the composition of lamellar liquid crystal. Fig. 4 shows that the thickness of the solvent layer in the lamellar liquid crystal decreases by only 0.1–0.2 nm when the weight ratio of nC10H21OH to Triton X-100 changes from 17/83 to 23/77 at a given water content; and the thickness of the solvent layer increases by only 1 nm when the volume ratio R changes from 0.40 to 1.00. Obviously, such a small change in dw cannot remarkably affect the size of Ag2S nanoparticles prepared in the lamellar liquid crystal. Fig. 6 shows that the X-ray diffraction pattern of the Ag2S nanoparticles prepared in the lamellar liquid crystal template (Fig. 6b) is identical to that of the standard sample of Ag2S (Fig. 6a).
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Fig. 5. TEM pictures of Ag2S nanoparticles. Weight ratio of Triton X-100/n-C10H21OH/H2O: (a) 50/16/34; (b) 53.4/10/36.6; (c) 63/11.8/25.2.
3.3. Lubrication properties of the lamellar liquid crystal The wear scar width on the block surface under high-speed ring-block wear tester is one of the characteristics of lubrication properties. Under the same load, the smaller the wear scar width, the better the lubrication performance. Fig. 7 shows that the wear scar width of alloy with the presence of LLC (Fig. 7a) or LLC/Ag2S nanoparticles (Fig. 7b) under a load of 200 N at a speed of 800 rotations/min increases with the solvent content in the lamellar liquid crystal, indicating the order degree of the lamellar liquid crystal decreases with the increase of the solvent content [15]. Compared with the wear scar width of block lubricated by the lamellar liquid crystal without Ag2S nanoparticles (Fig. 7a), the wear scar width of the block lubricated by the lamellar liquid crystal with Ag2S nanoparticles is reduced more remarkably (Fig. 7b), showing that the existence of Ag2S nanoparticles can improve the anti-wear
Fig. 6. X-ray diffraction spectra of Ag2S: (a) standard sample; (b) Ag2S nanoparticles prepared.
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Fig. 7. The relationship between the wear scar width and water content, wH : (a) lamellar liquid crystal; (b) LLC/Ag2S nanoparticles mixed system.
properties of the lamellar liquid crystal system. Fig. 8 shows the wear scar width of the alloy decreases with the increase of the content of Triton X-100 in the lamellar liquid crystal. This is because the order degree of the surfactant and the cosurfactant in the amphiphilc bilayer of the lamellar liquid crystal increases with the content of Triton X-100. The smaller wear scar width of the block lubricated by the lamellar liquid crystal with Ag2S nanoparticles (Fig. 8b) than that without Ag2S nanoparticles (Fig. 8a) illustrates again that the existence of Ag2S nanoparticles can make the anti-wear properties of the lamellar liquid crystal improved.
Fig. 8. The relationship between the wear scar width and Triton X-100 content, wT : (a) lamellar liquid crystal; (b) LLC/Ag2S nanoparticles mixed system.
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4. Conclusions 1. Because of the limitation of the size of the solvent layer in the lamellar liquid crystal, Ag2S nanoparticles can be obtained with a size of about 2–3 nm. 2. Ag2S nanoparticles can improve the anti-wear property of lamellar liquid crystal of Triton X-100/nC10H21OH/H2O system. Acknowledgement This work is supported by the National Natural Science Foundation of China (29733110).
References [1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12] [13] [14] [15]
L. Motte, F. Billoudet, E. Lacaze, J. Douin, M.P. Pileni, J. Phys. Chem. B 101 (1997) 138. C. Kaito, Y. Saito, K. Fujita, J. Cryst. Growth 94 (1989) 967. Q. Zhao, S. Bahadur, Wear 217 (1998) 62. S. Bhattacharya, R. Salher, J.L. Lauer, et al., Tribol. Trans. 31 (1987) 442. F.E. Lockwood, M.T. Bechaita, S.E. Friberg, ASLE Trans. 30 (1987) 539. C.S. Ma, G.Z. Li, Q. Shen, et al., J. Disp. Sci. Technol. 20 (1999) 1025. P.Q. Yan, R. Guo, M. Shen, Acta Physico-Chim. Sinica 11 (1993) 218. P.Q. Yan, R. Guo, M.C. Huang, Chin. Sci. Bull. 39 (1994) 1289. R. Guo, J. Disp. Sci. Technol. 20 (1999) 105. H.M. Yang, Z.D. Chen, X.H. Zhang, R. Guo, H.Q. Wang, Tribology 20 (2000) 214. R. Guo, Acta Physico-Chim. Sinica 7 (1991) 703. S.E. Friberg, R. Guo, A.J.I. Ward, J. Phys. Chem. 92 (1988) 7247. S.E. Friberg, R. Guo, Langmuir 4 (1988) 796. R. Guo, P.Q. Yan, Z.M. Liu, X.S. Zhu, M. Shen, Acta Chim. Sinica 10 (1994) 468. H.M. Yang, R. Guo, H.Q. Wang, Acta Physico-Chim. Sinica 16 (2000) 592.