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TiO2-supported 2D layered carbon derived from CO2 oxidation Ti3C2 for strengthening Si3N4 ceramic
Materials Letters 256 (2019) 126646
Contents lists available at ScienceDirect
Materials Letters journal homepage: www.elsevier.com/locate/mlblue
TiO2-supported 2D layered carbon derived from CO2 oxidation Ti3C2 for strengthening Si3N4 ceramic Jiongjie Liu a,b, Zixi Wang d, Jun Yang a, Hui Tan a, Zhuhui Qiao a,b,c,⇑, Weimin Liu a a
State Key Laboratory of Solid Lubrication, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, Lanzhou 730000, China Center of Materials Science and Optoelectronics Engineering, University of Chinese Academy of Sciences, Beijing 100049, China c Qingdao Center of Resource Chemistry & New Materials, Qingdao 266000, China d State Key Laboratory of Tribology, Department of Mechanical Engineering, Tsinghua University, Beijing 100084, China b
a r t i c l e
i n f o
Article history: Received 8 May 2019 Received in revised form 27 August 2019 Accepted 7 September 2019 Available online 7 September 2019 Keywords: Ceramic composite Ti3C2 MXenes Carbon platelet Oxidation Mechanical properties Friction and wear
a b s t r a c t Carbon can be applied as an additive to improve the properties of ceramic, but it has some damage effects on the matrix. Herein, the hybrid material of TiO2-supported carbon layers (C/TiO2) was synthesized through the oxidation of Ti3C2 at high temperature, which consisted of the large-scale carbon platelets with a thickness of 33.9 nm and the micron-scale TiO2 particles scattered between layers. By adding of C/TiO2 into Si3N4, the fracture toughness and the tribological properties of the composite achieved a comprehensive enhancement, importantly, without sacrificing the hardness. This was attributed to the bridging between carbon layers and grains, and the loading-support of the in-situ formed TiN. Ó 2019 Elsevier B.V. All rights reserved.
1. Introduction Advanced structural ceramics play an extremely important role in the development of modern industry. Among them, silicon nitride (Si3N4) has been widely used as bearings, valves, turbochargers and engine-parts, depending on its high hardness, excellent chemical stability and oxidation resistance [1,2]. However, because of few grain boundary slip, the brittleness as a major bottleneck has restricted the development of Si3N4 thus far [3]. Because of this, fatigue-induced microcracks are easily formed under dry sliding condition, which roughens the contact surfaces and leads to poor tribological properties of ceramic [4]. To solve these difficulties, the introduction of carbon into the matrix seems to be a good option because its unique twodimensional (2D) structure can jointly meet the requirements of toughening and lubrication [5]. Walker et al. [6] reported a graphene platelets (GPLs) reinforced Si3N4, and the fracture toughness (KIC) of the bulk was increased by 135%. Also, KIC achieved by Ramirez et al. [7] could reach 10.4 MPam1/2 for Si3N4 with 4.3 vol% of reduced graphene oxide (rGO). The fundamental reasons for toughening are the bridging of cracks and the necking of ⇑ Corresponding author at: State Key Laboratory of Solid Lubrication, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, Lanzhou 730000, China. E-mail address: [email protected] (Z. Qiao). https://doi.org/10.1016/j.matlet.2019.126646 0167-577X/Ó 2019 Elsevier B.V. All rights reserved.
graphene. Furthermore, focusing on lubrication of ceramics, the addition of carbon is also very effective [8]. Hyuga et al. [9] reduced the friction coefficient of Si3N4 to 0.25 by adding carbon fibers, due to the formation of carbon transfer films. Although lots of work has been conducted to optimize Si3N4, all composites still face a common challenge, namely, improving the toughness and/or tribological performances but greatly destroying the hardness. For the GPLs-Si3N4 [6], only 1.5 wt% GPLs reduced the hardness of Si3N4 by 30%, which is unacceptable for structural ceramic. Recently, titanium dioxide (TiO2) has been used as an effective additive to enhance the bearing capacity of the substrate [10]. With the incorporation of TiO2, the mechanical properties and wear resistance of the composite can be obviously improved [11]. Therefore, in this work, a TiO2-supported carbon layer (C/ TiO2) hybrid material was synthesized using Ti3C2 as a template. By its addition into the Si3N4 matrix, the mechanical and tribological properties of the composite were comprehensively improved. 2. Results and discussion The scheme diagram of synthesis of C/TiO2 is shown in Fig. S1 (Supplementary Materials). We choose Ti3AlC2 as the precursor material. After HF etching, Al atoms can be selectively removed based on the equation (1), leaving the Ti3C2 structure [12]. Immediately, Ti3C2 is oxidized by CO2 at 700 °C according to the equation
2
J. Liu et al. / Materials Letters 256 (2019) 126646
(2). As the structural template, C atoms and Ti atoms can be transformed into 2D carbon layers and TiO2 particles that are scattered between layers.
2Ti3 AlC2 þ 6HF ! 2Ti3 C2 þ 2AlF3 þ 3H2
ð1Þ
Ti3 C2 þ 3CO2 ! 3TiO2 þ 5C
ð2Þ
Fig. 1a and b show the unique accordion-like structure of Ti3C2. TEM image displays the faint stratification of Ti3C2 and its selected area electron diffraction (SAED) (Fig. 1e). After enlarging the local area, as shown in Fig. 1f, there are many light and dark stripes with a regular orientation, corresponding to (0 0 2) crystal plane of Ti3C2 [13]. By measurement the d-spacing value is about 1.176 nm, indicating a multi-layer superposition with about 5 layers calculated by the Bragg’s law. On the other hand, with the oxidation by CO2, the morphology of Ti3C2 has clearly changed. In addition to the known carbon layers, TiO2 particles about 2 lm are scattered between the layers (Fig. 1c and d). Further, Fig. 1g shows the TEM image of an overall morphology of C/TiO2, where some black particles are loaded on the thin carbon layers. By identifying from the high-resolution TEM (HRTEM) (Fig. 1h), these particles are anatase-TiO2 and the d-spacing of 0.3517 nm corresponds to (1 0 1) plane.
Fig. 2a shows the X-ray diffraction (XRD) patterns of Ti3C2, C/ TiO2 and C/TiO2-containing Si3N4 (Si3N4-C/TiO2). The preparation of Ti3C2 is successful and the characteristic (0 0 2) peak is detected. With the oxidation by CO2, the diffraction peaks corresponding to major anatase-TiO2 and a little rutile-TiO2 can be indexed, suggesting the transformation from Ti3C2 to TiO2. With the addition of C/ TiO2 into Si3N4 and hot press sintering (Supplementary Materials), the peaks of Si2N2O and TiN are found in the composite. A reasonable explanation is that Si3N4 reacts with TiO2 to form new crystal phases, which is experimentally proven by the reference [14]. Besides, the Raman spectra are carried out to identify the existence and structure of carbon (Fig. 2b). The peaks of anatase-TiO2 appear at 152 cm1, 203 cm1, 397 cm1, 512 cm1 and 638 cm1, confirming that TiO2 is produced by oxidation of Ti3C2 [13]. Meanwhile, the two carbon-related peaks at 1359 cm1 (D band) and 1577 cm1 (G band) are detected that correspond to the lattice defects of carbon atoms and the in-plane stretching vibration of sp2 atoms, respectively [7]. After fitting in the inset, the intensity ratio of the D peak and the G peak (ID/IG), as an indicator of carbon detect is 0.98, suggesting a relatively high defect concentration in carbon layers [13]. In addition, two samples, pure Si3N4 (SN) and Si3N4-based composite with 15 wt% C/TiO2 addition (SN-15CT), are chosen to
Fig. 1. (a, b) SEM images of Ti3C2. (c) SEM image of C/TiO2, where local area is enlarged in (d). (e, f) TEM images of Ti3C2, and the inset is SAED image of Ti3C2. (g) TEM image of C/TiO2. (h) HRTEM image of TiO2.
Fig. 2. (a) XRD patterns of Ti3C2, C/TiO2 and Si3N4-C/TiO2. (b) Raman spectra of Ti3C2 and C/TiO2, where the D peak and the G peak of C/TiO2 are fitted in the inset.
3
J. Liu et al. / Materials Letters 256 (2019) 126646 Table 1 Mechanical and tribological properties of SN and SN-15CT at room temperature. Samples
Hardness (GPa)
Fracture toughness (MPam1/2)
Friction coefficient
Wear rate (106 mm3/Nm)
SN SN-15CT
15.64 ± 0.25 15.54 ± 0.10
7.47 ± 0.24 8.30 ± 0.21
0.76 ± 0.17 0.59 ± 0.14
6.21 ± 0.27 3.77 ± 0.38
Fig. 3. (a, b and c) SEM images of fracture surfaces of SN-15CT. The inset in (a) is EDS mapping of C element. (d) BESEM image of SN-15CT and EDS mapping of Ti element. (e) SEM image of worn surfaces of SN and SN-15CT, where local area of SN-15CT is enlarged in (f).
evaluate the effect of C/TiO2 on the properties of Si3N4. As shown in Table 1, the reduction in hardness of Si3N4 is very slight despite such a high carbon content. This is mainly due to the loadsupporting of hard phase TiN [10,15]. Meanwhile, the fracture toughness of samples increases from 7.47 MPam1/2 to 8.30 MPam1/2. The friction coefficient shows a downward trend from 0.76 to 0.59, which is probably due to the lubrication of carbon layers [8,9]. Importantly, SN-15CT shows excellent wear resistance and the wear rate is reduced by about half. All these parameters indicate that the addition of C/TiO2 is effective to improve the comprehensive properties of Si3N4. Fig. 3a shows the fracture surface of SN-15CT. It can be seen that the cross section is fully compact but rugged, which represents a typical mode of brittle fracture [16]. Meanwhile, the EDS mapping of C element (inset) shows that carbon is uniformly distributed into the matrix, and because some carbon sheets are exposed to the fracture surface, C element exhibits obvious enrichment behavior. Further, as may be seen, the carbon platelets with a thickness of 33.9 nm are pressed tightly at grain boundaries and wrap the grains (Fig. 3b and c). Therefore, it is worth believing that the main toughening mechanism originates from the bridging of platelet-tograin and the pullout of high energy consumption [5–9]. Besides, Fig. 3d shows the backscattered SEM image (BESEM) of SN-15CT and the corresponding Ti mapping (inset). Combined with XRD results, it is seen that the white TiN particles about 10 lm can achieve high dispersion without agglomeration. The tribological results confirm that the formation of TiN leads to an outstanding anti-wear ability and the width of wear track of SN-15CT is reduced to 532.6 lm (Fig. 3e). The main reasons are as follows: first, because of the toughening of carbon platelets, the coarse microcracks in the SN caused by fatigue effect are replaced by the smaller and denser cracks in the SN-15CT (Figs. 3f and S2), thus
releasing the local stresses and alleviating the brittle peeling of surface materials; second, the wear resistance of ceramics is proportional to the product of the fracture toughness and the hardness. Here, because of constant hardness and enhanced toughness, the composite shows excellent wear resistance. 3. Conclusions In summary, we successfully prepared a C/TiO2 hybrid material by CO2 oxidation Ti3C2, which acted as an additive to truly improve the fracture toughness and tribological properties of Si3N4 without sacrificing the hardness. Because of the presence of carbon platelets at grain boundaries, the bridging of the platelet-to-grain was the main toughening mechanism. Besides, the load-supporting of TiN contributed to excellent wear resistance of composite. The results developed here could provide some insights to enhance the comprehensive properties of structural ceramics. Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. Acknowledgements This work is supported by the National Key R&D Program of China (2018YFB2000100) and National Natural Science Foundation of China (51775532 and 51701227); and one of the authors (Zhuhui Qiao) appreciates the support of the Taishan scholars Program of Shandong Province and the Outstanding Talents of Qingdao Innovations.
4
J. Liu et al. / Materials Letters 256 (2019) 126646
Appendix A. Supplementary data Supplementary data to this article can be found online at https://doi.org/10.1016/j.matlet.2019.126646. References [1] [2] [3] [4] [5]
N.P. Padture, Nat. Mater. 15 (2016) 804–809. P. Greil, Adv. Mater. 14 (2002) 709–716. R.O. Ritchie, Nat. Mater. 10 (2011) 817–822. J.J. Liu, J. Yang, Y. Yu, et al., Ceram. Int. 44 (2018) 14327–14334. L. Kvetkova, A. Duszova, P. Hvizdos, et al., Scripta. Mater. 66 (2012) 793–796.
[6] L.S. Walker, V.R. Marotto, M.A. Rafiee, et al., Acs. Nano. 5 (2011) 3182–3190. [7] C. Ramirez, P. Miranzo, M. Belmonte, et al., J. Eur. Ceram. Soc. 34 (2014) 161– 169. [8] H. Hyuga, M.I. Jones, K. Hirao, et al., J. Eur. Ceram. Soc. 24 (2004) 877–885. [9] H. Hyuga, K. Hirao, M.I. Jones, et al., J. Am. Ceram. Soc. 86 (2003) 1081–1087. [10] V. Jaiswal, S. Umrao, Kalyani, et al., Acs. Appl. Mater. Inter. 8 (2016) 11698– 11710. [11] V. Jaiswal, R.B. Rastogi, R. Kumar, et al., J. Mater. Chem. A. 2 (2014) 375–386. [12] G.N. Yushin, E.N. Hoffman, A. Nikitin, et al., Carbon. 43 (2005) 2075–2082. [13] W.Y. Yuan, L.F. Cheng, Y.N. Zhang, et al., Adv. Mater. Inter. 4 (2017). [14] L.X. Wu, W.M. Guo, L.Y. Zeng, et al., J. Am. Ceram. Soc. 100 (2017) 5353–5357. [15] N.C. Acikbas, J. Eur. Ceram. Soc. 38 (2018) 2279–2288. [16] Y. Zhou, H. Hyuga, D. Kusano, et al., Adv. Mater. 23 (2011) 4563-+.
Contents lists available at ScienceDirect
Materials Letters journal homepage: www.elsevier.com/locate/mlblue
TiO2-supported 2D layered carbon derived from CO2 oxidation Ti3C2 for strengthening Si3N4 ceramic Jiongjie Liu a,b, Zixi Wang d, Jun Yang a, Hui Tan a, Zhuhui Qiao a,b,c,⇑, Weimin Liu a a
State Key Laboratory of Solid Lubrication, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, Lanzhou 730000, China Center of Materials Science and Optoelectronics Engineering, University of Chinese Academy of Sciences, Beijing 100049, China c Qingdao Center of Resource Chemistry & New Materials, Qingdao 266000, China d State Key Laboratory of Tribology, Department of Mechanical Engineering, Tsinghua University, Beijing 100084, China b
a r t i c l e
i n f o
Article history: Received 8 May 2019 Received in revised form 27 August 2019 Accepted 7 September 2019 Available online 7 September 2019 Keywords: Ceramic composite Ti3C2 MXenes Carbon platelet Oxidation Mechanical properties Friction and wear
a b s t r a c t Carbon can be applied as an additive to improve the properties of ceramic, but it has some damage effects on the matrix. Herein, the hybrid material of TiO2-supported carbon layers (C/TiO2) was synthesized through the oxidation of Ti3C2 at high temperature, which consisted of the large-scale carbon platelets with a thickness of 33.9 nm and the micron-scale TiO2 particles scattered between layers. By adding of C/TiO2 into Si3N4, the fracture toughness and the tribological properties of the composite achieved a comprehensive enhancement, importantly, without sacrificing the hardness. This was attributed to the bridging between carbon layers and grains, and the loading-support of the in-situ formed TiN. Ó 2019 Elsevier B.V. All rights reserved.
1. Introduction Advanced structural ceramics play an extremely important role in the development of modern industry. Among them, silicon nitride (Si3N4) has been widely used as bearings, valves, turbochargers and engine-parts, depending on its high hardness, excellent chemical stability and oxidation resistance [1,2]. However, because of few grain boundary slip, the brittleness as a major bottleneck has restricted the development of Si3N4 thus far [3]. Because of this, fatigue-induced microcracks are easily formed under dry sliding condition, which roughens the contact surfaces and leads to poor tribological properties of ceramic [4]. To solve these difficulties, the introduction of carbon into the matrix seems to be a good option because its unique twodimensional (2D) structure can jointly meet the requirements of toughening and lubrication [5]. Walker et al. [6] reported a graphene platelets (GPLs) reinforced Si3N4, and the fracture toughness (KIC) of the bulk was increased by 135%. Also, KIC achieved by Ramirez et al. [7] could reach 10.4 MPam1/2 for Si3N4 with 4.3 vol% of reduced graphene oxide (rGO). The fundamental reasons for toughening are the bridging of cracks and the necking of ⇑ Corresponding author at: State Key Laboratory of Solid Lubrication, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, Lanzhou 730000, China. E-mail address: [email protected] (Z. Qiao). https://doi.org/10.1016/j.matlet.2019.126646 0167-577X/Ó 2019 Elsevier B.V. All rights reserved.
graphene. Furthermore, focusing on lubrication of ceramics, the addition of carbon is also very effective [8]. Hyuga et al. [9] reduced the friction coefficient of Si3N4 to 0.25 by adding carbon fibers, due to the formation of carbon transfer films. Although lots of work has been conducted to optimize Si3N4, all composites still face a common challenge, namely, improving the toughness and/or tribological performances but greatly destroying the hardness. For the GPLs-Si3N4 [6], only 1.5 wt% GPLs reduced the hardness of Si3N4 by 30%, which is unacceptable for structural ceramic. Recently, titanium dioxide (TiO2) has been used as an effective additive to enhance the bearing capacity of the substrate [10]. With the incorporation of TiO2, the mechanical properties and wear resistance of the composite can be obviously improved [11]. Therefore, in this work, a TiO2-supported carbon layer (C/ TiO2) hybrid material was synthesized using Ti3C2 as a template. By its addition into the Si3N4 matrix, the mechanical and tribological properties of the composite were comprehensively improved. 2. Results and discussion The scheme diagram of synthesis of C/TiO2 is shown in Fig. S1 (Supplementary Materials). We choose Ti3AlC2 as the precursor material. After HF etching, Al atoms can be selectively removed based on the equation (1), leaving the Ti3C2 structure [12]. Immediately, Ti3C2 is oxidized by CO2 at 700 °C according to the equation
2
J. Liu et al. / Materials Letters 256 (2019) 126646
(2). As the structural template, C atoms and Ti atoms can be transformed into 2D carbon layers and TiO2 particles that are scattered between layers.
2Ti3 AlC2 þ 6HF ! 2Ti3 C2 þ 2AlF3 þ 3H2
ð1Þ
Ti3 C2 þ 3CO2 ! 3TiO2 þ 5C
ð2Þ
Fig. 1a and b show the unique accordion-like structure of Ti3C2. TEM image displays the faint stratification of Ti3C2 and its selected area electron diffraction (SAED) (Fig. 1e). After enlarging the local area, as shown in Fig. 1f, there are many light and dark stripes with a regular orientation, corresponding to (0 0 2) crystal plane of Ti3C2 [13]. By measurement the d-spacing value is about 1.176 nm, indicating a multi-layer superposition with about 5 layers calculated by the Bragg’s law. On the other hand, with the oxidation by CO2, the morphology of Ti3C2 has clearly changed. In addition to the known carbon layers, TiO2 particles about 2 lm are scattered between the layers (Fig. 1c and d). Further, Fig. 1g shows the TEM image of an overall morphology of C/TiO2, where some black particles are loaded on the thin carbon layers. By identifying from the high-resolution TEM (HRTEM) (Fig. 1h), these particles are anatase-TiO2 and the d-spacing of 0.3517 nm corresponds to (1 0 1) plane.
Fig. 2a shows the X-ray diffraction (XRD) patterns of Ti3C2, C/ TiO2 and C/TiO2-containing Si3N4 (Si3N4-C/TiO2). The preparation of Ti3C2 is successful and the characteristic (0 0 2) peak is detected. With the oxidation by CO2, the diffraction peaks corresponding to major anatase-TiO2 and a little rutile-TiO2 can be indexed, suggesting the transformation from Ti3C2 to TiO2. With the addition of C/ TiO2 into Si3N4 and hot press sintering (Supplementary Materials), the peaks of Si2N2O and TiN are found in the composite. A reasonable explanation is that Si3N4 reacts with TiO2 to form new crystal phases, which is experimentally proven by the reference [14]. Besides, the Raman spectra are carried out to identify the existence and structure of carbon (Fig. 2b). The peaks of anatase-TiO2 appear at 152 cm1, 203 cm1, 397 cm1, 512 cm1 and 638 cm1, confirming that TiO2 is produced by oxidation of Ti3C2 [13]. Meanwhile, the two carbon-related peaks at 1359 cm1 (D band) and 1577 cm1 (G band) are detected that correspond to the lattice defects of carbon atoms and the in-plane stretching vibration of sp2 atoms, respectively [7]. After fitting in the inset, the intensity ratio of the D peak and the G peak (ID/IG), as an indicator of carbon detect is 0.98, suggesting a relatively high defect concentration in carbon layers [13]. In addition, two samples, pure Si3N4 (SN) and Si3N4-based composite with 15 wt% C/TiO2 addition (SN-15CT), are chosen to
Fig. 1. (a, b) SEM images of Ti3C2. (c) SEM image of C/TiO2, where local area is enlarged in (d). (e, f) TEM images of Ti3C2, and the inset is SAED image of Ti3C2. (g) TEM image of C/TiO2. (h) HRTEM image of TiO2.
Fig. 2. (a) XRD patterns of Ti3C2, C/TiO2 and Si3N4-C/TiO2. (b) Raman spectra of Ti3C2 and C/TiO2, where the D peak and the G peak of C/TiO2 are fitted in the inset.
3
J. Liu et al. / Materials Letters 256 (2019) 126646 Table 1 Mechanical and tribological properties of SN and SN-15CT at room temperature. Samples
Hardness (GPa)
Fracture toughness (MPam1/2)
Friction coefficient
Wear rate (106 mm3/Nm)
SN SN-15CT
15.64 ± 0.25 15.54 ± 0.10
7.47 ± 0.24 8.30 ± 0.21
0.76 ± 0.17 0.59 ± 0.14
6.21 ± 0.27 3.77 ± 0.38
Fig. 3. (a, b and c) SEM images of fracture surfaces of SN-15CT. The inset in (a) is EDS mapping of C element. (d) BESEM image of SN-15CT and EDS mapping of Ti element. (e) SEM image of worn surfaces of SN and SN-15CT, where local area of SN-15CT is enlarged in (f).
evaluate the effect of C/TiO2 on the properties of Si3N4. As shown in Table 1, the reduction in hardness of Si3N4 is very slight despite such a high carbon content. This is mainly due to the loadsupporting of hard phase TiN [10,15]. Meanwhile, the fracture toughness of samples increases from 7.47 MPam1/2 to 8.30 MPam1/2. The friction coefficient shows a downward trend from 0.76 to 0.59, which is probably due to the lubrication of carbon layers [8,9]. Importantly, SN-15CT shows excellent wear resistance and the wear rate is reduced by about half. All these parameters indicate that the addition of C/TiO2 is effective to improve the comprehensive properties of Si3N4. Fig. 3a shows the fracture surface of SN-15CT. It can be seen that the cross section is fully compact but rugged, which represents a typical mode of brittle fracture [16]. Meanwhile, the EDS mapping of C element (inset) shows that carbon is uniformly distributed into the matrix, and because some carbon sheets are exposed to the fracture surface, C element exhibits obvious enrichment behavior. Further, as may be seen, the carbon platelets with a thickness of 33.9 nm are pressed tightly at grain boundaries and wrap the grains (Fig. 3b and c). Therefore, it is worth believing that the main toughening mechanism originates from the bridging of platelet-tograin and the pullout of high energy consumption [5–9]. Besides, Fig. 3d shows the backscattered SEM image (BESEM) of SN-15CT and the corresponding Ti mapping (inset). Combined with XRD results, it is seen that the white TiN particles about 10 lm can achieve high dispersion without agglomeration. The tribological results confirm that the formation of TiN leads to an outstanding anti-wear ability and the width of wear track of SN-15CT is reduced to 532.6 lm (Fig. 3e). The main reasons are as follows: first, because of the toughening of carbon platelets, the coarse microcracks in the SN caused by fatigue effect are replaced by the smaller and denser cracks in the SN-15CT (Figs. 3f and S2), thus
releasing the local stresses and alleviating the brittle peeling of surface materials; second, the wear resistance of ceramics is proportional to the product of the fracture toughness and the hardness. Here, because of constant hardness and enhanced toughness, the composite shows excellent wear resistance. 3. Conclusions In summary, we successfully prepared a C/TiO2 hybrid material by CO2 oxidation Ti3C2, which acted as an additive to truly improve the fracture toughness and tribological properties of Si3N4 without sacrificing the hardness. Because of the presence of carbon platelets at grain boundaries, the bridging of the platelet-to-grain was the main toughening mechanism. Besides, the load-supporting of TiN contributed to excellent wear resistance of composite. The results developed here could provide some insights to enhance the comprehensive properties of structural ceramics. Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. Acknowledgements This work is supported by the National Key R&D Program of China (2018YFB2000100) and National Natural Science Foundation of China (51775532 and 51701227); and one of the authors (Zhuhui Qiao) appreciates the support of the Taishan scholars Program of Shandong Province and the Outstanding Talents of Qingdao Innovations.
4
J. Liu et al. / Materials Letters 256 (2019) 126646
Appendix A. Supplementary data Supplementary data to this article can be found online at https://doi.org/10.1016/j.matlet.2019.126646. References [1] [2] [3] [4] [5]
N.P. Padture, Nat. Mater. 15 (2016) 804–809. P. Greil, Adv. Mater. 14 (2002) 709–716. R.O. Ritchie, Nat. Mater. 10 (2011) 817–822. J.J. Liu, J. Yang, Y. Yu, et al., Ceram. Int. 44 (2018) 14327–14334. L. Kvetkova, A. Duszova, P. Hvizdos, et al., Scripta. Mater. 66 (2012) 793–796.
[6] L.S. Walker, V.R. Marotto, M.A. Rafiee, et al., Acs. Nano. 5 (2011) 3182–3190. [7] C. Ramirez, P. Miranzo, M. Belmonte, et al., J. Eur. Ceram. Soc. 34 (2014) 161– 169. [8] H. Hyuga, M.I. Jones, K. Hirao, et al., J. Eur. Ceram. Soc. 24 (2004) 877–885. [9] H. Hyuga, K. Hirao, M.I. Jones, et al., J. Am. Ceram. Soc. 86 (2003) 1081–1087. [10] V. Jaiswal, S. Umrao, Kalyani, et al., Acs. Appl. Mater. Inter. 8 (2016) 11698– 11710. [11] V. Jaiswal, R.B. Rastogi, R. Kumar, et al., J. Mater. Chem. A. 2 (2014) 375–386. [12] G.N. Yushin, E.N. Hoffman, A. Nikitin, et al., Carbon. 43 (2005) 2075–2082. [13] W.Y. Yuan, L.F. Cheng, Y.N. Zhang, et al., Adv. Mater. Inter. 4 (2017). [14] L.X. Wu, W.M. Guo, L.Y. Zeng, et al., J. Am. Ceram. Soc. 100 (2017) 5353–5357. [15] N.C. Acikbas, J. Eur. Ceram. Soc. 38 (2018) 2279–2288. [16] Y. Zhou, H. Hyuga, D. Kusano, et al., Adv. Mater. 23 (2011) 4563-+.