View PDF VersionPrevious ArticleNext Article
 
DOI: 10.1039/C6RA17061G (Paper) RSC Adv., 2016, 6, 110070-110076

Growth of Mo2C nanoparticles on graphene as lubricant filler for high tribological performances of fabric self-lubricating liner composites

Mingming Yangab, Zhaozhu Zhang*a, Junya Yuanab, Fang Guo*a, Xuehu Menc and Weimin Liua
aState Key Laboratory of Solid Lubrication, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, Tianshui Road 18th, Lanzhou 730000, P. R. China. E-mail: zzzhang@licp.cas.cn; guofang@licp.cas.cn; Fax: +86-931-4968098
bUniversity of Chinese Academy of Sciences, Beijing 100039, P. R. China
cSchool of Physical Science and Technology, Lanzhou University, Lanzhou, 730000, P. R. China

Received 3rd July 2016 , Accepted 2nd November 2016

First published on 3rd November 2016

Abstract

In this article, Mo2C/graphene nanocomposites were synthesized by an in situ carburization of ammonium molybdate adsorbed on the surface of graphene oxide, and its tribological performances as lubricant filler were systematically investigated. Characterizations using X-ray powder diffraction (XRD) and transmission electron microscopy (TEM) demonstrated that the Mo2C (10–30 nm) nanoparticles had been successfully synthesized and were well dispersed on the graphene nanosheets' surfaces. The results of wear tests showed that the Mo2C/graphene-2 reinforced hybrid PTFE/Nomex fabric self-lubricating liner composite exhibited the best tribological properties among all the samples. The excellent tribological performances of the Mo2C/graphene-2 reinforced hybrid PTFE/Nomex fabric self-lubricating liner composite were mainly ascribed to the synergistic lubricating actions of the Mo2C nanoparticles and graphene nanosheets during the sliding process. Besides, the wear mechanisms of the fabric composites are discussed in detail based on the characterizations.

1. Introduction

Phenol-formaldehyde resin (PF) was the first industrialized synthetic resin. It has been widely applied for adhesion, coating, thermal insulation materials, and molding compounds due to its good heat resistance, excellent mechanical strength, easy availability, low-cost raw materials, and simple processability.1–5 However, the wide application of PF as a friction material has promoted extensive research into enhancing its tribological performances. One approach is related to the incorporation of various reinforcing and filling constituents, such as fibers, nanoparticles, abrasives, binders, and fabrics, which at the same time do not damage their mechanical properties.6–8 Hence, it is important to correctly select and properly combine different components for the sake of meeting a large number of requirements of the friction materials, such as good wear resistance, a stable friction coefficient, and reliable mechanical strength, over a wide range of rigorous conditions.

Among these, two-dimensional (2D) fabrics have been widely used as a reinforcement to improve the mechanical and tribological properties of phenolic-based friction materials due to their light weight, facile fabrication, excellent specific strength, corrosion resistance, design flexibility, self-lubricating properties, and lower friction coefficient and wear rate.9–11 However, previous research has mainly focused on the tribological properties of one type of fiber woven out of fabric-reinforced composites,12–18 whereby a hybrid fabric is woven out of two or more kinds of fibers and consequently display two types of surfaces with different compositions of fibers. The satin weave hybrid PTFE/Nomex fabric was woven out of PTFE fibers and Nomex fibers, whereby the side rich in PTFE fibers was used as a friction surface because of the well lubricant properties of the PTFE fibers, while the Nomex fibers side was used as a bonding surface due to its excellent mechanical properties. Although PTFE exhibits excellent lubricant performances, the wear rate of pure PTFE is very high. Therefore, it is necessary to adopt an effective method to improve the tribological performances of hybrid PTFE/Nomex fabric self-lubricating liner composites. Recently, many investigations have focused on carbonaceous material (or inorganic particles)-reinforced polymers or alloys to improve the tribological properties.19–24 However, the tribological properties of hybrid PTFE/Nomex fabric self-lubricating liner composite reinforced by hybrid nanoparticles/graphene composites have rarely been reported.

In the present work, we used a convenient and eco-friendly method to synthesize Mo2C/graphene nanocomposites and in detail investigated the effect of the Mo2C and graphene ratio on the tribological performances of the hybrid PTFE/Nomex fabric self-lubricating liner composites. The characteristic peaks of graphene and Mo2C observed by XRD indicated that graphene oxide and Mo2C were reduced and grown on the graphene nanosheets' surfaces during the carburization process, respectively. The TEM characterizations demonstrated that the Mo2C nanoparticles were well dispersed on the graphene sheets' surfaces. Besides, the results of the wear test revealed that Mo2C/graphene-2 reinforced hybrid PTFE/Nomex fabric phenolic composite exhibited the lowest wear rate and a relatively lower friction coefficient. This was mainly attributed to the synergistic effect of the good lubricant performance of graphene and the high load-carrying capacity of Mo2C.

2. Experimental

2.1 Materials

The satin weave hybrid PTFE/Nomex fabric (volume fraction of PTFE to Nomex: 1[thin space (1/6-em)]:[thin space (1/6-em)]3) was woven out of PTFE fibers (fineness: 400 Denier) and Nomex fibers (fineness: 200 Denier), which were purchased from DuPont Plant. The adhesive resin (204 phenolic resin) was provided by Shanghai Xing-Guang Chemical Plant (China). Graphene oxide (GO) was provided by Nanjing XFNANO Materials Tech Co., Ltd, China. Ammonium molybdate (A.R. > 99.8%) was purchased from Fengyue Chemical Reagent Co., Ltd (Tianjin, China). Acetone, ethanol, and ethylacetate were all of analytical grade and used as received. The water was deionized by distillation. The chemical compositions of the counterpart pin (AISI 1045 steel) were: C 0.42–0.5, Si 0.17–0.37, Mn 0.5–0.8, P 0.035, S 0.035, Cr 0.25, Ni 0.25, Cu 0.25, Fe balance in wt%.

2.2 Preparation of the Mo2C/graphene composites

The Mo2C/graphene composites were prepared according to the literature.25 Typically, graphene oxide (250 mg, 185 mg, 125 mg, respectively) was dissolved in 30 ml distilled water, and then 98 mg of ammonium molybdate was mixed in the solution. The mixed solution was treated by sonication for 2 h to obtain a well-dispersed aqueous solution. After that, the aqueous solution was maintained at 130 °C in an oven (3 h) to remove the solvent, and the resulting dried GO-supported ammonium molybdate was placed on a quartz boat and heated at 800 °C in a tube furnace for 2 h under an Ar atmosphere with a heating rate of 6 °C min−1. Finally, the Mo2C/graphene composites were obtained. The samples were denoted as: Mo2C/graphene-1 ((NH4)6Mo7O24·4H2O[thin space (1/6-em)]:[thin space (1/6-em)]GO = 98 mg[thin space (1/6-em)]:[thin space (1/6-em)]125 mg), Mo2C/graphene-2 ((NH4)6Mo7O24·4H2O[thin space (1/6-em)]:[thin space (1/6-em)]GO = 98 mg[thin space (1/6-em)]:[thin space (1/6-em)]185 mg), and Mo2C/graphene-3 ((NH4)6Mo7O24·4H2O[thin space (1/6-em)]:[thin space (1/6-em)]GO = 98 mg[thin space (1/6-em)]:[thin space (1/6-em)]250 mg). Mo2C particles were also prepared using (NH4)6Mo7O24·4H2O and glucose (molar ratio of 1[thin space (1/6-em)]:[thin space (1/6-em)]1) as raw materials. Fig. 1 is a schematic diagram of the preparation process of the Mo2C/graphene composites.
image file: c6ra17061g-f1.tif
Fig. 1 Schematic diagram of the preparation process of the Mo2C/graphene composites.

2.3 Preparation of the hybrid fabric/phenolic composites

The hybrid PTFE/Nomex fabric was cleaned with petroleum ether and ethanol sequentially in a Soxhlet extractor and then dried in an oven at 50 °C. The adhesive solution was prepared by mixing the adhesive with a mixed solvent of acetone, ethanol, and ethylacetate with the volume ratio of 1[thin space (1/6-em)]:[thin space (1/6-em)]1[thin space (1/6-em)]:[thin space (1/6-em)]1. Subsequently, the hybrid fabric was immersed in the adhesive solution with the content of filler of 1.5 wt%. After several cycles of immersion, the mass fraction of the hybrid PTFE/Nomex fabric in the fabric/resin composite reached to about 75 ± 5%. Finally, the prepregs were cut into pieces and adhered onto the AISI-1045 steel (size of φ 45 mm × φ 8 mm, surface roughness of 0.45 μm) using 204 phenolic resin and then cured at 180 °C for 2 h. In the following text, the untreated fabric composite is termed as composite A, while the graphene reinforced fabric composite is termed as composite B, Mo2C particles reinforced fabric composite is termed as composite C, the mixed graphene and Mo2C reinforced fabric composite is termed as composite D, Mo2C/graphene-1 reinforced fabric composite is termed as composite E, Mo2C/graphene-2 reinforced fabric composite is termed as composite F, and Mo2C/graphene-3 reinforced fabric composite is termed as composite G.

2.4 Material characterization

The EDXA images and morphology of the worn surfaces of the composites and their counterpart steel pins were analyzed on a JSM-5600LV scanning electron microscope (SEM) equipped with an energy dispersive X-ray analyzer (EDXA). The morphology and microstructure of the Mo2C/graphene nanocomposites were investigated by FEI Tecnai F30 transmission electron microscopy (TEM). X-ray photoelectron spectroscopy (XPS) measurements were conducted on a VGESCALAB210 spectrometer. X-ray powder diffraction (XRD) analysis was carried out on an XRD system (Philips Corp., The Netherlands), operating with Cu-K radiation at a scanning step of 0.5° per s over the 2θ range of 10° to 80°.

2.5 Friction and wear tests

The friction and wear behavior of the hybrid fabric self-lubricating liner composites were investigated using a Xuanwu-III pin-on-disk friction and wear tester (Fig. 2).26 The pin-on-disk tester consisted of loading a stationary pin sliding against a rotating disk that was affixed with the hybrid PTFE/Nomex fabric self-lubricating liner composites. The flat-ended AISI-1045 pin (diameter 2 mm) was fixed to the load arm with a chuck. The distance between the center of the pin and the axis was free: comprising a vertical one, which allowed normal load application by direct contact with the disk, and a horizontal one, for friction measurement. Prior to each test, the pin was polished with 350, 700, and 900 grade water-proof abrasive papers sequentially to a surface roughness Ra of 0.15 μm, and then cleaned with acetone. The sliding was performed at room temperature, with the applied loads in the range of 70–100 MPa and a speed of 0.26 m s−1 (sliding distance of 1872 m). At the end of each test, the corresponding wear volume loss (V) of the composite was obtained by measuring the depth of the wear scar on a micrometer (resolution: 0.001 mm). The wear performances was expressed by the wear rate (ω, m3 (N m)−1) as follows: ω = V/(PL), where V is the wear volume loss in m3, P is the load in newton, and L is the sliding distance in meters. The sliding time was 2 h under dry sliding conditions. The friction coefficient was the ratio of the measured friction force and the load. It was measured from the frictional torque gained by a load cell sensor, which was acquired directly by the computer running the friction measure software. Each experiment was carried out three times and the average value was used.
image file: c6ra17061g-f2.tif
Fig. 2 Schematic diagram of the pin-on-disc wear tester.

3. Results and discussion

TEM images of the Mo2C and Mo2C/graphene composites are shown in Fig. 3. Fig. 3a shows that the Mo2C nanoparticles possess a granular microstructure with an average diameter of 40–50 nm. Furthermore, it is clear that numerous particles are joined together and agglomerate. The TEM images of three kinds of Mo2C/graphene hybrids are shown in Fig. 3b and 2d. Compared with the Mo2C/graphene-1 (see Fig. 3b), the morphologies and the distributions of the decorated Mo2C particles for Mo2C/graphene-2 and Mo2C/graphene-3 were totally different. The decorated Mo2C particles for Mo2C/graphene-1 tend to aggregate due to the increased Mo2C content. For Mo2C/graphene-2 and Mo2C/graphene-3, however, the graphene nanosheets' surfaces were decorated with uniformly dispersed Mo2C nanoparticles with diameters of 10–15 nm (see Fig. 3c and d). This is attributed to the bonding in the graphene framework, which effectively avoids the agglomeration of Mo2C nanoparticles.25 The EDX spectrum of the Mo2C/graphene-2 from its TEM image is shown in Fig. 3e. High intensity peaks of the Mo element appear, indicating that the Mo2C nanoparticles were successfully anchored on the graphene nanosheets' surfaces.
image file: c6ra17061g-f3.tif
Fig. 3 TEM images of pure Mo2C particles (a), Mo2C/graphene-1 (b), Mo2C/graphene-2 (c), Mo2C/graphene-3 (d), and EDX spectra of Mo2C/graphene-2 (e).

Fig. 4a shows the XRD patterns of graphene oxide, graphene, Mo2C, and three kinds of Mo2C/graphene nanocomposites. After the carburization process, a broad peak appears at around 23.78°, which can be ascribed to the (002) planes of graphene. Furthermore, the disappearance of the peak at 11° indicates that graphene oxide was reduced to graphene after thermal treatment in the Ar atmosphere at 800 °C for 2 h. The main diffraction peaks of Mo2C were: 34.1, 37.7, 39.3, 52.2, 61.5, 74.6, and 75.5° and were indexed to the (100), (002), (101), (102), (110), (103), (112), and (201) crystalline planes, demonstrating that a high purity of Mo2C particles were successfully synthesized. For the Mo2C/graphene nanocomposites, the diffraction peaks of Mo2C and graphene could be observed simultaneously. This result indicated that the Mo2C nanoparticles were successfully anchored on the graphene nanosheets' surfaces. Besides, the peaks intensities became stronger with increasing the content of Mo2C in the Mo2C/graphene nanocomposites. These results are consistent with the previous literature reports.25,27–29


image file: c6ra17061g-f4.tif
Fig. 4 (a) XRD patterns of graphene oxide, graphene, Mo2C, and Mo2C/graphene composites, (b) XPS spectra of Mo2C and Mo2C/graphene composites.

The compositions of the Mo2C and Mo2C/graphene nanocomposites were analyzed by XPS. The corresponding elemental compositions of Mo2C and the Mo2C/graphene nanocomposites are listed in Table 1. From Fig. 4b, it was clearly found that C (285 eV), O (532 eV), and Mo (Mo3d 232 eV, Mo3p 398 eV) were the main elements coexisting in the Mo2C and Mo2C/graphene nanocomposites. The content of Mo gradually increases with the graphene oxide content decreasing.

Table 1 Relative atomic concentrations on the surfaces of the samples
Samples Surface composite (at%)
C Mo O
Mo2C 77.68 5.54 16.78
Mo2C/graphene-1 82.95 5.23 11.82
Mo2C/graphene-2 87.71 2.84 11.45
Mo2C/graphene-3 86.11 2.66 11.23

Fig. 5 shows the mean friction coefficients and wear rate of the hybrid PTFE/Nomex fabric self-lubricating liner composites reinforced with different fillers under the load of 70 MPa at the speed of 0.26 m s−1. When graphene, Mo2C, and the mixture of graphene and Mo2C incorporated into the hybrid fabric composite, the friction coefficient increased. When the Mo2C/graphene composites were incorporated into hybrid PTFE/Nomex fabric self-lubricating liner composite, however, the friction coefficient decreased. Furthermore, the Mo2C/graphene-2 nanocomposites reinforced fabric composite exhibited the lowest friction coefficient. The use of fillers other than the mixture of graphene and Mo2C remarkably reduced the wear rate of the fabric composites. Compared with the unfilled hybrid PTFE/Nomex fabric self-lubricating liner composite, the composite with Mo2C/graphene-2 exhibited the best wear resistance, which was mainly attributed to the synergistic effect of the good lubricant performance of graphene and the high load-carrying capacity of Mo2C (Table 2) in the fabric composite. Besides, compared to the Mo2C/graphene-2 reinforced fabric composite, the fabric composite reinforced with a mixture of graphene and Mo2C displayed a higher friction coefficient and wear rate, thus demonstrating that the synergistic lubricating performance was closely related to the composite microstructure.


image file: c6ra17061g-f5.tif
Fig. 5 (a) Mean friction coefficients and (b) mean wear rates at 70 MPa, 0.26 m s−1, of a hybrid PTFE/Nomex fabric/phenolic composite reinforced with different fillers.
Table 2 Hardness of the hybrid fabric composites reinforced with different fillers
Samples Hardness (HRB)
Composite A 22.0 ±1.8
Composite B 22.57 ±0.4
Composite C 25.7 ±0.5
Composite D 24.87 ±0.4
Composite E 24.1 ±0.3
Composite F 23.8 ±0.35

SEM images of the worn surfaces of the hybrid PTFE/Nomex fabric self-lubricating liner composites modified by different fillers are presented in Fig. 6. Fig. 6a shows the SEM image of the worn surface of the unfilled hybrid PTFE/Nomex fabric self-lubricating liner composite. Numerous fibers-matrix de-bonding and wear debris, and excessive peeled-out and cut-off fibers appear on the worn surface, which support its highest wear rate. When graphene and Mo2C were incorporated into the hybrid PTFE/Nomex fabric self-lubricating liner composite, there are relatively fewer fibers pulled out and cut off from the fabric composites in the worn surface (Fig. 6b and c). These results demonstrate that graphene and Mo2C possessed excellent lubricant performances and a high load-carrying capacity, respectively. Furthermore, the worn surface of the Mo2C/graphene-2 reinforced fabric composite was quite smooth, and the phenolic groups were strongly combined with the fibers and thus very few fibers were exposed (see Fig. 6e). This observation indicated that the Mo2C/graphene-2 composite provided an excellent lubricant phase and a high load-carrying capacity phase.


image file: c6ra17061g-f6.tif
Fig. 6 SEM images of the worn surfaces of: (a) composite A, (b) composite B, (c) composite C, (d) composite E, (e) composite F, and (f) composite G.

Fig. 7 shows the influence of the applied load on the friction coefficient and wear rate of the unfilled and Mo2C/graphene-2 reinforced hybrid PTFE/Nomex fabric self-lubricating liner composites. It should be noted that the friction coefficient of the two kinds of hybrid PTFE/Nomex fabric self-lubricating liner composites decrease, while the wear rate increases with the increase in applied load. This phenomenon is mainly attributed to the phenolic resin softening and decomposing because of the temperature increase from the rubbing surface. As can see from Fig. 7a and b, however, the friction coefficient and the wear rate of the Mo2C/graphene-2 reinforced fabric composite at different applied loads are lower than that of the pristine hybrid fabric self-lubricating liner composite. During the sliding process, Mo2C nanoparticles with graphene act as load-bearing materials and a solid lubricant to improve the mechanical properties and tribological properties. Mo2C/graphene-2 incorporated into the hybrid fabric self-lubricating liner can decrease the actual contact surface between two rubbing surfaces and further reduce the friction coefficient and wear rate.30 The above results also indicated that Mo2C/graphene-2 is an excellent lubricant filler for the hybrid PTFE/Nomex fabric self-lubricating liner composite.


image file: c6ra17061g-f7.tif
Fig. 7 (a) Mean friction coefficients and (b) mean wear rates at 0.26 m s−1 for composite A and composite F.

Fig. 8 and 9 show the SEM images of the worn surfaces and counterpart pin of the composites A and F. As can be seen in the micrographs for composite A (see Fig. 8a), a large number of cut-off fibers, excessive fiber breakage, and numerous wear debris can be observed, which result in easy breakage of the hybrid fabric composite. The low load-carrying capacity of composite A caused an easy pulverization of the fibers. Besides, the counterpart pin surface was very rough. Many wear debris and furrows on the entire surface can be found, indicating that the counterpart pin undergoes severe damage (see Fig. 9a and b). The analysis results of the SEM images of the worn surfaces are consistent with the data from the friction coefficient and wear rate. For composite F, only a few damaged fibers and wear debris were found on the worn surface (see Fig. 8b), which demonstrates that the incorporation of Mo2C/graphene-2 into the hybrid PTFE/Nomex fabric self-lubricating liner composite can significantly enhance the tribological performances. Furthermore, the transfer film formed on the counterpart pin sliding against composite F was smooth and continuous (see Fig. 9c and d). The evenly dispersed Mo elements on the counterpart pin surface demonstrate that continuous and uniform transfer films were formed on the counterpart pin. The formed transfer film can then effectively prevent direct contact of the metallic counterpart pin and the fabric composite.31 Hence, the composite F displayed a lower wear rate.


image file: c6ra17061g-f8.tif
Fig. 8 SEM images for composite A (a) and composite F (b).

image file: c6ra17061g-f9.tif
Fig. 9 SEM images of the worn surfaces of the counterpart pins sliding against” composite A (a) and (b), and composite F (c) and (d). The inset is the EDXA images of Mo. The applied load and sliding speed in the tests were 80 MPa and 0.26 m s−1, respectively.

4. Conclusion

In summary, we used a simple and environmentally friendly method to synthesize Mo2C/graphene nanocomposites. The XRD and TEM analyses demonstrated that the Mo2C nanoparticles were successfully synthesized and were uniformly decorated on the graphene nanosheets' surfaces. Besides, we incorporated graphene, Mo2C, and Mo2C/graphene nanocomposites into a hybrid PTFE/Nomex fabric self-lubricating liner composite to systemically study its tribological performances. The wear tests results indicated that the Mo2C/graphene-2 reinforced hybrid PTFE/Nomex fabric self-lubricating liner composite exhibited the lowest friction coefficient and wear rate. Compared with the unfilled hybrid fabric composite, the Mo2C/graphene-2 reinforced hybrid PTFE/Nomex fabric self-lubricating liner composite underwent mild wear and the counterpart pin formed a uniform and continuous transfer film. These results were mainly attributed to the excellent synergistic effect of the excellent lubricant performance of graphene and the high load-carrying capacity of the Mo2C nanoparticles.

Acknowledgements

The authors acknowledge the financial support of the National Natural Science Foundation of China (Grant No. 51375472, 51305429 and 51675252).

References

  1. H. Kazuhisa and A. Masakatsu, React. Funct. Polym., 2013, 73, 256–269 CrossRef.
  2. G. W. Yi and F. Y. Yan, Wear, 2007, 262, 121–129 CrossRef CAS.
  3. U. S. Hong, S. L. Jung, K. H. Cho, S. J. Kim and H. Jang, Wear, 2009, 266, 739–744 CrossRef CAS.
  4. C. Q. Liu, K. Z. Li, H. J. Li, S. Y. Zhang and Y. L. Zhang, Polym. Degrad. Stab., 2014, 102, 180–185 CrossRef CAS.
  5. S. A. Song, Y. S. Chung and S. S. Kim, Compos. Sci. Technol., 2014, 103, 85–93 CrossRef CAS.
  6. J. Fei, H. J. Li, Y. W. Fu, L. H. Qi and Y. L. Zhang, Wear, 2010, 269, 534–540 CrossRef CAS.
  7. J. Fei, H. J. Li, J. F. Huang and Y. W. Fu, Tribol. Int., 2012, 56, 30–37 CrossRef CAS.
  8. H. J. Song, Z. Z. Zhang and Z. Z. Luo, Surf. Coat. Technol., 2006, 201, 2760–2767 CrossRef CAS.
  9. M. Sharma, J. Bijwe and P. Mitschang, Wear, 2011, 271, 2261–2268 CrossRef CAS.
  10. A. Aktas, M. Aktas and F. Turan, Compos. Struct., 2013, 103, 119–135 CrossRef.
  11. L. H. Sun, Z. G. Yang and X. H. Li, Mater. Sci. Eng., A, 2008, 497, 487–494 CrossRef.
  12. S. Tiwari, J. Bijwe and S. Panier, J. Mater. Sci., 2012, 47, 2891–2898 CrossRef CAS.
  13. B. Shivamurthy, K. Udaya Bhat and S. Anandhan, Mater. Des., 2013, 44, 136–143 CrossRef CAS.
  14. A. Majumdar, B. Singh Butola and A. Srivastava, Mater. Des., 2014, 54, 295–300 CrossRef CAS.
  15. F. S. Su, Z. Z. Zhang, K. Wang and W. M. Liu, Mater. Sci. Eng., A, 2006, 430, 307–313 CrossRef.
  16. Q. H. Wang, X. R. Zhang and X. Q. Pei, Mater. Des., 2010, 31, 1403–1409 CrossRef CAS.
  17. A. K. Kadiyala and J. Bijwe, Wear, 2013, 301, 802–809 CrossRef CAS.
  18. S. Tiwari, J. Bijwe and S. Panier, Wear, 2011, 270, 688–694 CrossRef CAS.
  19. H. Wang, G. Y. Xie, Z. G. Zhu, Z. Ying and Y. Zeng, Composites, Part A, 2014, 67, 268–273 CrossRef CAS.
  20. L. J. Cui, H. Z. Geng, W. Y. Wang, L. T. Chen and J. Gao, Carbon, 2013, 54, 277–282 CrossRef CAS.
  21. A. D. Moghadam, E. Omrani, P. L. Menezes and P. K. Rohatgi, Composites, Part B, 2015, 77, 402–420 CrossRef.
  22. M. Tabandeh-Khorshid, E. Omrani, P. L. Menezes and P. K. Rohatgi, Engineering Science and Technology, an International Journal, 2016, 19, 463–469 CrossRef.
  23. L. Prchlik, S. Samphath, J. Gutleber, G. Bancke and A. W. Ruff, Wear, 2011, 249, 1103–1115 CrossRef.
  24. E. Omrani, A. D. Moghadam, P. L. Menezes and P. K. Rohatgi, in Ecotribology, Springer International Publishing, 2016, pp. 63–103 Search PubMed.
  25. B. B. Wang, G. Wang and H. Wang, J. Mater. Chem., 2015, 3, 17403–17411 RSC.
  26. M. M. Yang, X. T. Zhu, G. N. Ren, X. H. Men, F. Guo, P. L. Li and Z. Z. Zhang, Eur. Polym. J., 2015, 67, 143–151 CrossRef CAS.
  27. T. D. Dao and H. M. Jeong, Mater. Res. Bull., 2015, 70, 651–657 CrossRef CAS.
  28. C. Y. Tang, A. Sun, Y. S. Xu, Z. Z. Wu and D. Z. Wang, J. Power Sources, 2015, 296, 18–22 CrossRef CAS.
  29. L. L. He, Y. Qin and P. Chen, RSC Adv., 2015, 5, 43141–43147 RSC.
  30. E. Omrani, B. Barari, A. D. Moghadam, P. K. Rohatgi and K. M. Pollai, Tribol. Int., 2015, 92, 222–232 CrossRef CAS.
  31. A. R. Konicek, P. W. Jacobs, M. N. Webster and A. M. Schilowitz, Tribol. Int., 2016, 94, 14–19 CrossRef CAS.
This journal is © The Royal Society of Chemistry 2016
Click here to see how this site uses Cookies. View our privacy policy here.