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Technical Brief

Analysis of Tribological Properties of Triethanolamine Modified Graphene Oxide Additive in Water PUBLIC ACCESS

[+] Author and Article Information
Jianlin Sun

School of Materials Science and Engineering,
University of Science and Technology Beijing,
30 Xueyuan Road, Haidian District,
Beijing 100083, China
e-mail: sjl@ustb.edu.cn

Shaonan Du

School of Materials Science and Engineering,
University of Science and Technology Beijing,
30 Xueyuan Road, Haidian District,
Beijing 100083, China
e-mail: dsnbeikeda@126.com

Yanan Meng

School of Materials Science and Engineering,
University of Science and Technology Beijing,
30 Xueyuan Road, Haidian District,
Beijing 100083, China
e-mail: mynfighting@163.com

Ping Wu

School of Materials Science and Engineering,
University of Science and Technology Beijing,
30 Xueyuan Road, Haidian District,
Beijing 100083, China;
Department of Foundational Science,
Beijing Union University,
97 North Fourth Ring East Road, Chaoyang District,
Beijing 100101, China
e-mail: ldtwuping@buu.edu.cn

1Corresponding author.

Contributed by the Tribology Division of ASME for publication in the JOURNAL OF TRIBOLOGY. Manuscript received January 9, 2018; final manuscript received June 3, 2018; published online July 24, 2018. Assoc. Editor: Satish V. Kailas.

J. Tribol 141(1), 014501 (Jul 24, 2018) (6 pages) Paper No: TRIB-18-1013; doi: 10.1115/1.4040512 History: Received January 09, 2018; Revised June 03, 2018

In this paper, triethanolamine modified graphene oxide (TMGO) has been synthesized by filtering and drying the high-temperature reaction solution of graphene oxide (GO) and triethanolamine. The tribological performance of TMGO and GO in de-ionized water were investigated using a four-ball tribometer. The microscopic morphology of the worn surface was analyzed by optical microscope and scanning electron microscope (SEM) and energy dispersive spectroscopy (EDS). The results showed that the average friction coefficient (AFC) and wear scar diameter (WSD) of 0.1 wt % TMGO decreased by 21.9% and 6.2% compared with the two values of 0.1 wt % GO, and no corrosion occurred on metal surface. The minimum of the AFC and WSD occurred at 0.3 wt % TMGO. This study provides a new reference for the application of graphene oxide in lubrication.

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Compared with lubricating oil, water is an inexpensive lubricant with some special advantages, such as better cooling capacity and not hazardous to human beings and the environment [1]. But the low extreme pressure performance and the high corrosive property of water seriously affect the quality of the contact surface. Those limit its application in most lubrication occasions [2]. For these reasons, numerous studies on high quality additives have been carried out to ameliorate lubrication properties of water-based lubricants [35]. Kong et al. [6] in their review on tribological mechanism of nanofluids enumerated many nanoparticles as additives dispersed in base fluids. They can improve the antiwear, load carrying, and friction reduction properties of base lubricants.

At present, graphene which is a novel two-dimensional morphology carbon material has attracted interests for its lubrication property due to the unique structural and physical performance [7,8]. A large number of studies have shown that graphene exhibits impressive lubricity not only as a solid lubricant but also as an additive of fluid lubricants [911]. However, as the structure and chemical properties of graphene are stable and the surface energy is high, graphene easily agglomerates in water [12]. In contrast, the surface of graphene oxide (GO) sheets contains more oxygen-containing functional groups (carboxyl, hydroxyl, and carbonyl), thus GO can be dispersed in water [13]. On the flip side, the carboxyl groups of GO result in a low pH of the formative dispersion. Therefore, it is necessary to consider corrosion when using GO as a lubricant additive [14].

Graphene oxide sheets contain reactive oxygen functional groups, which make it easy for modification [15]. Singh et al. [16] synthesized a silica/GO composite powder by hydrothermal method, and compared with pure silica and pure GO, the silica/GO composite provided lower friction and wear rate. Thus, it can be seen that the modifier of additive played an important role in enhancing the properties of the lubricants. This work proposed an easy method to modify GO with triethanolamine and studied the tribological properties of the same concentration of triethanolamine modified graphene oxide (TMGO) and GO. Then, the tribological tests were designed to determine better suitable concentration of TMGO as additive. And the surface quality was analyzed by observing surface morphology using scanning electron microscope (SEM) under different lubrication conditions.

Preparation of Triethanolamine Modified Graphene Oxide.

According to the description of the preparation of NH2-graphene by Lai et al. [17], the TMGO was synthesized with modification and simplification. First, 0.1 g of GO was dispersed into 50 ml of de-ionized water via 30 min ultrasonication at room temperature to get a uniform and stable suspension. Then, an appropriate amount of concentrated hydrochloric acid was added to the GO solution to adjust pH to 1–2. The GO dispersion was heated to 40 °C, and 1 g of triethanolamine was slowly added and continuously stirred 30 min for a uniform dispersion. The solution was transferred into a Teflon-lined autoclave and heated for reaction at 130 °C for 12 h. The obtained sample was subjected to centrifugal washing with de-ionized water and then filtered to remove the remaining triethanolamine and hydrochloric acid, the whole process repeated at least three times until the pH of the solution is 7–8. Finally, the product was dried at 60 °C for 10 h.

Tribological Tests.

As in the above preparation of 0.1 wt % GO dispersion, the same method was used to prepare TMGO suspensions with mass fraction of 0.05%, 0.1%, 0.2%, 0.3%, 0.4%, and 0.5%. The tribological test was carried out according to the standard method ASTM D2783 on a MRS-10A four-ball tribometer and the picture of the equipment was shown in Fig. 1. Lubricant was added in the oil tank to completely cover the four balls. The material of the ball is GCr15, and the diameter is 12.7 mm. The hardness of the ball is 61–63 HRC (Ra value 24 nm). Before the start of the tribological experiment, balls were washed with acetone, ethanol and then dried to remove the oil of the surface. Friction and wear tests for water, GO suspension, and TMGO suspensions were measured under 98 N, 1200 rpm, and 20 °C for 30 min. Each test must be carried out for at least three times. At the end of each test, the wear scar diameter (WSD) of the steel surface was measured for three times using the optical microscope and averaged.

Morphology and Structure of Triethanolamine Modified Graphene Oxide.

In order to visually evaluate the structure of the synthesized TMGO, the surface morphologies of graphene, GO, and TMGO were characterized by SEM, as shown in Fig. 2. It can be seen that graphene nanosheets in solid powder state had large size and thickness. From Fig. 2(b), we can find that GO surfaces exhibited a flexible sheet structure, and the sheets were small. For TMGO, as shown in Fig. 2(c), the lamellae were thinner and the surface folds were more obvious compared to graphene and GO. Figure 3 shows the infrared (IR) spectra of graphene, GO, and TMGO, and the corresponding IR absorption peaks of GO are shown in Table 1. According to the Fourier transform infrared spectroscopy (FT-IR) spectrum of GO, which demonstrated that the raw material GO contained hydroxyl, carboxyl, and epoxy groups. The peaks of TMGO at 1261.47 cm−1 and 1049.24 cm−1 can be attributed to the antisymmetrical contraction vibration and symmetrical contraction vibration of ether group (C–O–C). It indicated that hydroxyl groups in triethanolamine attacked the epoxy groups in the GO leading to ring-opening reactions. Considering the conditions of the reaction, the reactants did not have strong reduction and the nucleophilicity of the nitrogen atom in triethanolamine, the neutralization reaction of amine and carboxylic acid occurred, as shown in Fig. 4.

Tribological Properties.

The friction coefficient curve, average friction coefficient (AFC) and WSD of water, GO lubricant, and TMGO lubricant are shown in Fig. 5. It can be seen that, with the lubrication of 0.1 wt % TMGO, the friction coefficient was the lowest and the curve was the smoothest. The data of AFC, WSD of TMGO decreased by 21.9% and 6.2% compared with the two values of GO. The pH values of the three lubricants are shown in Table 2. Figure 6 shows the optical microscopic ((a)(c)) of wear surfaces of steel ball lubricated by water, 0.1 wt % GO, and 0.1 wt % TMGO. From Fig. 6, it can be observed that the addition of 0.1 wt % GO can reduce WSD and surface roughness, but caused serious corrosion on the metal surface. This can be explained by the pH of GO in Table 2. When 0.1 wt % TMGO was added to water, the wear scar of the steel ball was the minimum and shallowest, and no corrosion occurred on the surface.

In order to further study the lubrication property of water-based lubricants containing TMGO, the tribological tests of TMGO with different contents were systematically implemented. The friction coefficient curve, AFC and WSD of 0.05 wt %, 0.1 wt %, 0.2 wt %, 0.3 wt %, 0.4 wt %, and 0.5 wt % TMGO are shown in Fig. 7. From Fig. 7, it can be found that when the content of TMGO was 0.3 wt %, the friction coefficient was minimum and the curve was smoothest. The values of AFC and WSD of 0.3 wt % TMGO were minimal. But when the content of TMGO added to 0.5 wt %, values of AFC and WSD were almost the same as 0.05 wt % TMGO, much higher than 0.1 wt % and 0.2 wt %.

All these results indicated that when the content of TMGO was 0.1 wt % or 0.2 wt %, the TMGO nanoplates in the contact area of the friction pairs were less, which cannot sufficiently give full play to the lubrication. When the mass fraction of TMGO was 0.4% or 0.5%, TMGO nanoplates tended to agglomerate to exhibit dispersion unevenness, which affected the performance of lubrication.

Figure 8 shows SEM images of wear scars under various lubrication conditions. To determine the elemental composition of wear scar lubricated by 0.3 wt % TMGO, analysis on the energy dispersive spectroscopy (EDS) result was carried out. It can be seen that the rubbing surface lubricated by water suffered worse wear, because severe microploughing wear and adhesive wear occurred on the surface of the ball (Fig. 8(a)). There were a lot of corrosion pits on the surface lubricated with 0.1 wt % GO. The worn surface lubricated by 0.1 wt % TMGO showed less furrows, and no corrosion pits appeared on the surface of the scar. This indicated that 0.1 wt % TMGO not only improved the lubrication effect but also would not corrode metal surface. From Figs. 8(c) and 8(d), when the content of TMGO was 0.3 wt %, the surface of the wear scar was smoother and flatter corresponding to the lowest friction coefficient. Therefore, it can be concluded from the completed experiments that water containing 0.3 wt % TMGO has better tribological properties.

In this study, TMGO was successfully prepared by the simplifying hydrothermal reaction. Then, TMGO was characterized by SEM and FT-IR spectroscopy to demonstrate that triethanolamine was grafted on the substrate of GO by ring-opening reaction with the epoxy group. The tribological properties experimental results indicated that water-based lubricant with TMGO had better lubrication performance and did not corrode the metal surface compared with GO. The better concentration of TMGO as water-based lubricant additive was 0.3 wt %. When the concentration of TMGO reached to 0.5 wt %, TMGO molecules easily agglomerated in water affecting the performance of lubrication.

  • Beijing Natural Science Foundation (No. 2182041).

Xu, P. , Chen, Q. , Cao, L. , Tu, T. , Wan, Y. , Gao, J. , and Pu, J. , 2017, “ Tribological Performance of Pullulan Additives in Water-Based Lubricant,” Tribol. Mater. Surf. Interface, 11(2), pp. 83–87. [CrossRef]
Tomala, A. , Karpinska, A. , Werner, W. S. M. , Olver, A. , and Störi, H. , 2010, “ Tribological Properties of Additives for Water-Based Lubricants,” Wear, 269(11–12), pp. 804–810. [CrossRef]
Xu, J. , Yang, S. , Niu, L. , Liu, X. , and Zhao, J. , 2017, “ Study on Tribological Properties of Antimony Nanoparticles as Liquid Paraffin Additive,” ASME J. Tribol., 139(5), p. 051801. [CrossRef]
Kinoshita, H. , Nishina, Y. , Alias, A. A. , and Fujii, M. , 2014, “ Tribological Properties of Monolayer Graphene Oxide Sheets as Water-Based Lubricant Additives,” Carbon, 66, pp. 720–723. [CrossRef]
Rasheed, A. K. , Khalid, M. , Rashmi, W. , Gupta, T. C. S. M. , and Chan, A. , 2016, “ Graphene Based Nanofluids and Nanolubricants—Review of Recent Developments,” Renewable Sustainable Energy Rev., 63, pp. 346–362. [CrossRef]
Kong, L. , Sun, J. , and Bao, Y. , 2017, “ Preparation, Characterization and Tribological Mechanism of Nanofluids,” RSC Adv., 7(21), pp. 12599–12609. [CrossRef]
Zheng, D. , Cai, Z. , Shen, M. , Li, Z. , and Zhu, M. , 2016, “ Investigation of the Tribology Behaviour of the Graphene Nanosheets as Oil Additives on Textured Alloy Cast Iron Surface,” Appl. Surf. Sci., 387, pp. 66–75. [CrossRef]
Zhang, L. , Pu, J. , Wang, L. , and Xue, Q. , 2015, “ Synergistic Effect of Hybrid Carbon Nanotube−Graphene Oxide as Nanoadditive Enhancing the Frictional Properties of Ionic Liquids in High Vacuum,” ACS Appl. Mater. Interfaces, 7(16), pp. 8592–8600. [CrossRef] [PubMed]
Zhao, W. , Zeng, Z. , Peng, S. , Wu, X. , Xue, Q. , and Chen, J. , 2013, “ Fabrication and Investigation the Microtribological Behaviors of Ionic Liquid–Graphene Composite Films,” Tribol. Trans., 56(3), pp. 480–487. [CrossRef]
Bai, L. , Srikanth, N. , Zhao, B. , Liu, B. , Liu, Z. , and Zhou, K. , 2016, “ Lubrication Mechanisms of Graphene for DLC Films Scratched by a Diamond Tip,” J. Phys. D, 49(48), pp. 485302–485312. [CrossRef]
Ota, J. , Hait, S. K. , Sastry, M. I. S. , and Ramakumar, S. S. V. , 2015, “ Graphene Dispersion in Hydrocarbon Medium and Its Application in Lubricant Technology,” RSC Adv., 5(66), pp. 53326–53332. [CrossRef]
Zhang, W. , Zhou, M. , Zhu, H. , Tian, Y. , Wang, K. , Wei, J. , Ji, F. , Li, X. , Li, Z. , Zhang, P. , and Wu, D. , 2011, “ Tribological Properties of Oleic Acid-Modified Graphene as Lubricant Oil Additives,” J. Phys. D, 44(20), pp. 205303–205306. [CrossRef]
Zhao, J. , Li, Y. , Wang, Y. , Mao, J. , He, Y. , and Luo, J. , 2017, “ Mild Thermal Reduction of Graphene Oxide as a Lubrication Additive for Friction and Wear Reduction,” RSC Adv., 7(3), pp. 1766–1770. [CrossRef]
Alias, A. A. , Kinoshita, H. , Nishina, Y. , and Fujii, M. , 2016, “ Dependence of pH Level on Tribological Effect of Graphene Oxide as an Additive in Water Lubrication,” Int. J. Automot. Mech. Eng., 13(1), pp. 3150–3156. [CrossRef]
Jiang, G. , Lin, Z. , Chen, C. , Zhu, L. , Chang, Q. , Wang, N. , Wei, W. , and Tang, H. , 2011, “ TiO2 Nanoparticles Assembled on Graphene Oxide Nanosheets With High Photocatalytic Activity for Removal of Pollutants,” Carbon, 49(8), pp. 2693–2701. [CrossRef]
Singh, V. K. , Elomaa, O. , Johansson, L. , Hannula, S. , and Koskinen, J. , 2014, “ Lubricating Properties of Silica/Graphene Oxide Composite Powders,” Carbon, 79, pp. 227–235. [CrossRef]
Lai, L. , Chen, L. , Zhan, D. , Sun, L. , Liu, J. , Lim, S. H. , Poh, C. K. , Shen, Z. , and Lin, J. , 2011, “ One-Step Synthesis of NH2-Graphene From In Situ Graphene-Oxide Reduction and Its Improved Electrochemical Properties,” Carbon, 49(10), pp. 3250–3257. [CrossRef]
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References

Xu, P. , Chen, Q. , Cao, L. , Tu, T. , Wan, Y. , Gao, J. , and Pu, J. , 2017, “ Tribological Performance of Pullulan Additives in Water-Based Lubricant,” Tribol. Mater. Surf. Interface, 11(2), pp. 83–87. [CrossRef]
Tomala, A. , Karpinska, A. , Werner, W. S. M. , Olver, A. , and Störi, H. , 2010, “ Tribological Properties of Additives for Water-Based Lubricants,” Wear, 269(11–12), pp. 804–810. [CrossRef]
Xu, J. , Yang, S. , Niu, L. , Liu, X. , and Zhao, J. , 2017, “ Study on Tribological Properties of Antimony Nanoparticles as Liquid Paraffin Additive,” ASME J. Tribol., 139(5), p. 051801. [CrossRef]
Kinoshita, H. , Nishina, Y. , Alias, A. A. , and Fujii, M. , 2014, “ Tribological Properties of Monolayer Graphene Oxide Sheets as Water-Based Lubricant Additives,” Carbon, 66, pp. 720–723. [CrossRef]
Rasheed, A. K. , Khalid, M. , Rashmi, W. , Gupta, T. C. S. M. , and Chan, A. , 2016, “ Graphene Based Nanofluids and Nanolubricants—Review of Recent Developments,” Renewable Sustainable Energy Rev., 63, pp. 346–362. [CrossRef]
Kong, L. , Sun, J. , and Bao, Y. , 2017, “ Preparation, Characterization and Tribological Mechanism of Nanofluids,” RSC Adv., 7(21), pp. 12599–12609. [CrossRef]
Zheng, D. , Cai, Z. , Shen, M. , Li, Z. , and Zhu, M. , 2016, “ Investigation of the Tribology Behaviour of the Graphene Nanosheets as Oil Additives on Textured Alloy Cast Iron Surface,” Appl. Surf. Sci., 387, pp. 66–75. [CrossRef]
Zhang, L. , Pu, J. , Wang, L. , and Xue, Q. , 2015, “ Synergistic Effect of Hybrid Carbon Nanotube−Graphene Oxide as Nanoadditive Enhancing the Frictional Properties of Ionic Liquids in High Vacuum,” ACS Appl. Mater. Interfaces, 7(16), pp. 8592–8600. [CrossRef] [PubMed]
Zhao, W. , Zeng, Z. , Peng, S. , Wu, X. , Xue, Q. , and Chen, J. , 2013, “ Fabrication and Investigation the Microtribological Behaviors of Ionic Liquid–Graphene Composite Films,” Tribol. Trans., 56(3), pp. 480–487. [CrossRef]
Bai, L. , Srikanth, N. , Zhao, B. , Liu, B. , Liu, Z. , and Zhou, K. , 2016, “ Lubrication Mechanisms of Graphene for DLC Films Scratched by a Diamond Tip,” J. Phys. D, 49(48), pp. 485302–485312. [CrossRef]
Ota, J. , Hait, S. K. , Sastry, M. I. S. , and Ramakumar, S. S. V. , 2015, “ Graphene Dispersion in Hydrocarbon Medium and Its Application in Lubricant Technology,” RSC Adv., 5(66), pp. 53326–53332. [CrossRef]
Zhang, W. , Zhou, M. , Zhu, H. , Tian, Y. , Wang, K. , Wei, J. , Ji, F. , Li, X. , Li, Z. , Zhang, P. , and Wu, D. , 2011, “ Tribological Properties of Oleic Acid-Modified Graphene as Lubricant Oil Additives,” J. Phys. D, 44(20), pp. 205303–205306. [CrossRef]
Zhao, J. , Li, Y. , Wang, Y. , Mao, J. , He, Y. , and Luo, J. , 2017, “ Mild Thermal Reduction of Graphene Oxide as a Lubrication Additive for Friction and Wear Reduction,” RSC Adv., 7(3), pp. 1766–1770. [CrossRef]
Alias, A. A. , Kinoshita, H. , Nishina, Y. , and Fujii, M. , 2016, “ Dependence of pH Level on Tribological Effect of Graphene Oxide as an Additive in Water Lubrication,” Int. J. Automot. Mech. Eng., 13(1), pp. 3150–3156. [CrossRef]
Jiang, G. , Lin, Z. , Chen, C. , Zhu, L. , Chang, Q. , Wang, N. , Wei, W. , and Tang, H. , 2011, “ TiO2 Nanoparticles Assembled on Graphene Oxide Nanosheets With High Photocatalytic Activity for Removal of Pollutants,” Carbon, 49(8), pp. 2693–2701. [CrossRef]
Singh, V. K. , Elomaa, O. , Johansson, L. , Hannula, S. , and Koskinen, J. , 2014, “ Lubricating Properties of Silica/Graphene Oxide Composite Powders,” Carbon, 79, pp. 227–235. [CrossRef]
Lai, L. , Chen, L. , Zhan, D. , Sun, L. , Liu, J. , Lim, S. H. , Poh, C. K. , Shen, Z. , and Lin, J. , 2011, “ One-Step Synthesis of NH2-Graphene From In Situ Graphene-Oxide Reduction and Its Improved Electrochemical Properties,” Carbon, 49(10), pp. 3250–3257. [CrossRef]

Figures

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Fig. 1

Schematic diagram of tribological test

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Fig. 2

Scanning electron microscope images of graphene (a), GO (b), and TMGO (c)

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Fig. 3

FT-IR spectra of graphene, GO, and TMGO

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Fig. 4

Schematic illustration for the preparation of TMGO

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Fig. 5

(a) Friction coefficients and (b) AFC and WSD of the wear scars lubricated by water, 0.1 wt % GO and 0.1 wt % TMGO

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Fig. 6

Optical microscopic images of the wear scar surfaces of steel ball lubricated by (a) water, and water added with (b) 0.1 wt % GO and (c) 0.1 wt % TMGO

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Fig. 7

(a) Friction coefficient and (b) AFC and WSD of the wear scars lubricated by different concentration TMGO suspensions

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Fig. 8

Scanning electron microscope images of the wear scars lubricated by (a) water: (b) 0.1 wt % GO, (c) 0.1 wt % TMGO, and (d) 0.3 wt % TMGO, and EDS spectra of the regions I and II

Tables

Table Grahic Jump Location
Table 1 FT-IR absorption peaks of GO
Table Grahic Jump Location
Table 2 The pH values of water, GO, and TMGO

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