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Preparation of MXene-Cu2O nanocomposite and effect on thermal decomposition of ammonium perchlorate
Solid State Sciences 35 (2014) 62e65
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Solid State Sciences journal homepage: www.elsevier.com/locate/ssscie
Preparation of MXene-Cu2O nanocomposite and effect on thermal decomposition of ammonium perchlorate Yupeng Gao, Libo Wang*, Zhengyang Li, Aiguo Zhou, Qianku Hu, Xinxin Cao School of Materials Science and Engineering, Henan Polytechnic University, Jiaozuo, Henan 454000, China
a r t i c l e i n f o
a b s t r a c t
Article history: Received 21 February 2014 Received in revised form 11 June 2014 Accepted 15 June 2014 Available online 8 July 2014
MXenes are novel graphene-like 2-D materials. Cu2O is an effective additive for thermal decomposition of ammonium perchlorate (AP). We reported the synthesis of MXene (Ti3C2), Cu2O and MXene-Cu2O respectively. The samples were characterized by means of X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM). Results indicate that the MXene is composed of lots of nanosheets and the thickness is 30 ± 10 nm, and Cu2O nanoparticles nucleate and grow heterogeneously directly on the surface of MXene. The effect of these MXene, Cu2O and MXene-Cu2O samples on the thermal decomposition of AP were investigated using TG-DSC. The results revealed that MXene-Cu2O have a great influence on the thermal decomposition of AP than that of pure MXene and Cu2O. © 2014 Elsevier Masson SAS. All rights reserved.
Keywords: MXene Cu2O Nanocomposite Microstructure Thermal analysis
1. Introduction MXenes are novel graphene-like two-dimensional (2D) transition metal carbides [1]. The 2D materials were made from MAX phases (Ti3AlC2, Ti2AlC, Ta4AlC3, (Ti0.5,Nb0.5)2AlC, (V0.5,Cr0.5)3AlC2, and Ti3AlCN) by HF exfoliating [1,2]. Because of the graphene-like morphology, MXenes are expected to be applied extensively in many areas. It is indicated that MXenes are very promising anode materials for lithium-ion battery [3e5], hydrogen storage materials [6], high capacitors electrode materials [7], and lead adsorption materials [8]. As a p-type semiconductor, Cu2O has been widely used in many fields, such as gas sensing [9e11], catalysis [12,13], electrochemical sensing [14e16], negative electrode materials [17,18], and solar energy conversion [19] due to its unique optical and electrical properties. Recently, graphene-based inorganic oxide composites become one of the most important research frontiers in the application of graphene [20e23]. Taking into account the excellent individual properties of graphene and oxide, the combination of graphene with oxide nanoparticles could give enhanced performances. However there is no report on the MXene-based inorganic oxide composites. Ammonium perchlorate (NH4ClO4 or AP) is an important energetic material which widely used in solid rocket propellants. The
* Corresponding author. Tel./fax: þ86 391 3986910. E-mail address: [email protected] (L. Wang). http://dx.doi.org/10.1016/j.solidstatesciences.2014.06.014 1293-2558/© 2014 Elsevier Masson SAS. All rights reserved.
decomposition of AP are mainly affected by the types of the catalyst, such as Ni, NiO, Fe2O3, MnO2, CuFe2O4 and et al. [24e28] which can decrease the pyrolysis temperature and increase the combustion efficiency. Among them, Cu2O [29] show excellent catalytic effect on the thermal decomposition of AP. MXene has a large specific surface area for nanoparticles to spread and distribute on. Up to now, to the best of our knowledge the catalytic behavior of MXene-Cu2O nanocomposite in the thermal decomposition of AP has not been reported. Therefore, it is attractive to have a study on MXene-Cu2O nanocomposite as effective catalyst for thermal decomposition of AP. In this work, we reported the synthesis of MXene, Cu2O and MXene-Cu2O, and their effect on the thermal decomposition of AP. The results showed that MXene-Cu2O exhibited more excellent performance of the thermal decomposition of AP compared with MXene and Cu2O alone.
2. Experimental 2.1. Materials Copper acetate (Cu(CH3COO)2$H2O), glucose (C6H12O6), hydrofluoric acid (HF, 49 wt. % in H2O) and ammonium perchlorate (NH4ClO4) were purchased from Shanghai Chemical Reagents Company, China. All the experimental materials were of analytical grade and used without further purification. Ti3AlC2 was lab-made
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separated by centrifugation, washed with water and ethanol several times, and dried at 70 C in vacuum. Preparation of MXene-Cu2O: 0.1 g MXene, 0.005 mol Cu(CH3COO)2$H2O and 0.01 mol C6H12O6 were dissolved in 100 ml distilled water in a 250 ml round-bottomed flask with magnetic stirring. After stirred for 12 h at room temperature, the mixed transparent solution was heated to 90 C and kept for 5 h. Then the product was separated by centrifugation, washed with water and ethanol several times, and dried at 70 C in vacuum. Preparation of AP/(MXene, Cu2O, MXene-Cu2O) mixtures: 0.01 g MXene, Cu2O or MXene-Cu2O was mixed with 0.49 g of AP, respectively, and ground in an agate mortar. A little acetone was added into the mixtures during the grinding. Then the mixtures were dried in a vacuum oven at 50 C for 12 h. 2.3. Characterization Fig. 1. XRD patterns of the samples.
powders by pressureless sintering in a tube furnace from the mixture of TiH2, Al and C [30]. 2.2. Preparation of MXene, Cu2O, MXene-Cu2O and AP/(Mxene, Cu2O, MXene-Cu2O) mixtures Preparation of MXene: Ten grams of Ti3AlC2 were immersed in 100 ml 49% HF solutions, stirred for 1 min, and then kept for 8 h at room temperature. Thereafter, the samples were centrifugally separated and washed several times with deionized water. The treated powders were dried in a vacuum drying oven. Preparation of Cu2O: In a typical experiment, 0.005 mol Cu(CH3COO)2$H2O and 0.01 mol C6H12O6 were dissolved in 100 ml distilled water in a 250 ml round-bottomed flask with magnetic stirring, then the mixed transparent solution was heated to 90 C and kept for 5 h. After heating for the desired time, the product was
The crystal structure of the obtained samples was characterized with powder X-ray diffraction (XRD, D8 X-ray diffractometer equipment with Cu Ka radiation). The morphology and microstructures of the samples were examined by field emission scanning electron microscopy (FESEM, Hitachi S4800). The catalytic performance of samples for thermal decomposition of ammonium perchlorate was evaluated using a Setaram Evolution 2400 thermal analyzer (TG-DSC), under argon flow of 20 ml/min with a heating rate of 25 K/min from room temperature to 500 C. 3. Results and discussion Fig. 1 shows XRD pattern of the synthesized samples. In Fig. 1, the diffraction peaks of Cu2O with 2q values at 29.5 , 36.4 , 42.3 , 61.3 and 73.5 correspond to the crystal plane (110), (111), (200), (220) and (311) of crystalline Cu2O, respectively (JCPDS 05-0667). The diffraction peaks of MXene with 2q values at 9.0 and 18.4 are belongs to (002) and (004) plane of Ti3C2 MXene [2]. The FESEM images of the MXene, Cu2O and MXene-Cu2O are shown in Fig. 2. From Fig. 2(A), it can be seen that the MXene is
Fig. 2. FESEM images of (A) MXene, (B) Cu2O, (C) MXene-Cu2O.
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composed of lots of nano-sheets and the thickness is 30 ± 10 nm. These nano-sheets stack together like papers with unequal spacing. Fig. 2(B) is the microstructure of Cu2O sample. From Fig. 2(B), Cu2O is with irregular polyhedral morphology and large polyhedrons are constructed by lots of smaller polyhedrons. The Cu2O morphology of MXene-Cu2O (Fig. 2(C)) is different from that shown in Fig. 2(B). Because of large surface area, MXene provides many nucleation sites. Therefore Cu2O heterogeneously nucleate and grow on the surface of MXene directly. Resulted Cu2O crystals are in near-sphere phase with diameter of ~100 nm, while Cu2O crystals in Fig. 2(B) are polyhedrons with size ~1 mm. The effect on AP's thermal decomposition of MXene, Cu2O and MXene-Cu2O were studied by TG-DSC method. The results are shown in Figs. 3 and 4. In Fig. 3, the endothermic peak of AP at 250 C corresponds to the crystal transformation from orthorhombic phase to cubic phase. The exothermic peaks of pure AP at 349.7 C and 462.9 C correspond to the low-temperature decomposition and the high-temperature decomposition [31]. It can be seen that MXene, Cu2O and MXene-Cu2O have obvious catalytic effect to AP's decomposition processes. If Mxene, Cu2O and MXeneCu2O are added respectively, the decomposition temperature gradually decreases. MXene has little effect on the decomposition temperature of AP. The high decomposition temperature of AP in presence of Cu2O only decreases 106.4 C. However, the high decomposition temperature of AP with MXene-Cu2O decreases 121.4 C compared to that of the pure AP. TG and DTG curves are shown in Fig. 4(A) and (B). It is shown that the presence of MXene, Cu2O and MXene-Cu2O can decrease weight-loss temperature and it can be seen that in the range from room temperature to 500 C, two weight loss steps are clearly observed for AP with MXene, Cu2O and MXene-Cu2O. Because MXene additives have no significant catalytic effect, the decrease of weight-loss temperature is not significant, only decreases 12.4 C. While Cu2O and MXene-Cu2O have high catalytic activity, and then, the addition of Cu2O and MXene-Cu2O in AP leads to significant reduction of the weight-loss temperature of decomposition. The thermal decomposition rate of AP with MXene-Cu2O nanocomposite was higher than rate of AP with Cu2O microparticles. The above analysis shows that the MXene-Cu2O nanocomposite has higher catalytic activity comparing with MXene and Cu2O. The catalysis of Cu2O is because adsorbed oxygen on the surface of Cu2O microspheres simplifies the high temperature decomposition of AP as proton acceptor and promotes the decomposition reaction. For MXene-Cu2O, the specific surface area of Cu2O nanoparticles
Fig. 4. TG and dTG curves of samples.
obtained in presence of MXene is increased, which can provide more active sites. Additionaly, due to the good thermal conductivity [8], MXene can significantly improve the heat transfer rate of reaction system. Finally, due to lamella structure, the large specific surface area of MXene is favorable to the adsorption of reactant molecule (NH3, HClO4). And MXene can promote the decomposition of HClO4 gas adsorbed on the surface of MXene layers in the high-temperature decomposition stage, which accelerated the decomposition of AP and reduces the temperature of hightemperature exothermic decomposition process. Therefore, by combining the advantages of those two materials, thermal decomposition temperature of AP is significantly reduced. 4. Conclusion In conclusion, MXene, Cu2O and MXene-Cu2O have been synthesized successfully. The as-synthesized samples were characterized by XRD and FESEM. The results show that the morphology of Cu2O was changed and the particle size decreased in the presence of MXene. The TG-DSC analysis indicates MXene-Cu2O nanocomposite has a higher catalytic activity comparing with MXene and Cu2O on the thermal decomposition of AP. Acknowledgments
Fig. 3. DSC curves of samples.
This work was supported by National Nature Science Foundation of China (51205111, 51002045), Plan for Scientific Innovation Talent of Henan Province (134100510008), Program for Innovative
Y. Gao et al. / Solid State Sciences 35 (2014) 62e65
Research Team of Henan Polytechnic University (T2013-4), Program for Innovative Research Team (in Science and Technology) in the University of Henan Province (No. 2012IRTSTHN007), Opening Project of Henan Key Discipline Open Laboratory of Mining Engineering Materials (MEM12-11). References [1] M. Naguib, M. Kurtoglu, V. Presser, J. Lu, J. Niu, M. Heon, L. Hultman, Y. Gogotsi, M.W. Barsoum, Adv. Mater. 23 (2011) 4248e4253. [2] M. Naguib, O. Mashtalir, J. Carle, V. Presser, J. Lu, L. Hultman, Y. Gogotsi, M.W. Barsoum, ACS Nano 6 (2012) 1322e1331. [3] M. Naguib, J. Come, B. Dyatkin, V. Presser, P.-L. Taberna, P. Simon, M.W. Barsoum, Y. Gogotsi, Electrochem Commun. 16 (2012) 61e64. [4] Q. Tang, Z. Zhou, P. Shen, J. Am. Chem. Soc. 134 (2012) 16909e16916. [5] I.R. Shein, A.L. Ivanovskii, Comp. Mater. Sci. 65 (2012) 104e114. [6] Q.K. Hu, D.D. Sun, Q.H. Wu, H.Y. Wang, L.B. Wang, B.Z. Liu, A.G. Zhou, J.L. He, J. Phys. Chem. A 117 (2013) 14253e14260. [7] M.R. Lukatskaya, O. Mashtalir, C.E. Ren, Y. Dall'Agnese, P. Rozier, P.L. Taberna, M. Naguib, P. Simon, M.W. Barsoum, Y. Gogotsi, Science 341 (2013) 1502e1505. [8] Q.M. Peng, J.X. Guo, Q.R. Zhang, J.Y. Xiang, B.Z. Liu, A.G. Zhou, R.P. Liu, Y.J. Tian, J. Am. Chem. Soc. 136 (11) (2014) 4113e4116. [9] W. Septina, S. Ikeda, M. Alam Khan, T. Hirai, T. Harada, M. Matsumura, L.M. Peter, Electrochim. Acta 56 (2011) 4882. [10] S.Z. Deng, V. Tjoa, H.M. Fan, H.R. Tan, D.C. Sayle, M. Olivo, S. Mhaisalkar, J. Wei, C.H. Sow, J. Am. Chem. Soc. 134 (2012) 4905e4917. [11] H.G. Zhang, Q.S. Zhu, Y. Zhang, Y. Wang, L. Zhao, B. Yu, Adv. Funct. Mater. 17 (2007) 2766e2771. [12] J.Y. Ho, M.H. Huang, J. Phys. Chem. C 113 (2009) 14159e14164.
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[13] G. Mao, D.Q. Chu, L.M. Wang, A.X. Wang, Y.J. Wen, X.Z. Yang, Mater. Lett. 109 (2013) 62e65. [14] L. Zhang, H. Li, Y.H. Ni, J. Li, K.M. Liao, G.C. Zhao, Electrochem. Commun. 11 (2009) 812e815. [15] L.N. Guan, H. Pang, J.J. Wang, Q.Y. Lu, J.Z. Yin, F. Gao, Chem. Commun. 46 (2010) 7022e7024. [16] X.J. Wang, X. Chen, D.G. Evans, W.S. Yang, Sens. Actuators B 160 (2011) 1444e1449. [17] A. Lamberti, M. Destro, S. Bianco, M. Quaglio, A. Chiodoni, C.F. Pirri, C. Gerbaldi, Electrochem Acta 70 (2012) 62e68. [18] X. Wang, L.C. Yang, Y.P. Wu, J. Solid State Chem. 182 (2009) 2486e2490. [19] B.D. Yuhas, P.D. Yang, J. Am. Chem. Soc. 131 (2009) 3756e3761. [20] J.C. Liu, H.W. Bai, Y.J. Wang, Z.Y. Liu, X.W. Zhang, D.D. Sun, Adv. Funct. Mater. 20 (2010) 4175e4181. [21] Z.Y. Yin, S.X. Wu, X.Z. Zhou, X. Huang, Q.C. Zhang, F. Boey, H. Zhang, Small 6 (2010) 307e312. [22] D.H. Wang, R. Kou, D. Choi, Z.G. Yang, Z.M. Nie, J. Li, L.V. Saraf, D.H. Hu, J.G. Zhang, G.L. Graff, J. Liu, M.A. Pope, I.A. Aksay, ACS Nano 4 (2010) 1587e1595. [23] C. Xu, X. Wang, L.C. Yang, Y.P. Wu, J. Solid State Chem. 182 (2009) 2486e2490. [24] H.Z. Duan, X.Y. Lin, G.P. Liu, L. Xu, F.S. Li, J. Mater. Process Tech. 208 (2004) 494e498. [25] Y.P. Wang, J.W. Zhu, X.J. Yang, L.D. Lu, X. Wang, Thermochim. Acta 437 (2005) 106e109. [26] Y.F. Zhang, X.H. Liu, J.R. Nie, L. Yu, Y.L. Zhong, C.J. Huang, Solid State Chem. 184 (2) (2011) 387e390. [27] L.J. Chen, D.Y. Zhu, Solid State Sci. 27 (2014) 69e72. [28] T. Liu, L.S. Wang, P. Yang, B.Y. Hu, Mater. Lett. (2008) 624056e624058. [29] X.Y. Gong, Y.P. Gao, L.B. Wang, P.F. Guo, Nano 8 (5) (2013), 1350047e5. [30] L. Li, A.G. Zhou, L. Xu, Z.Y. Li, L.B. Wang, J. Wuhan. Univ. Technol. 28 (2013) 882e887. [31] L.M. Song, S.J. Zhang, B. Chen, J.J. Ge, X.C. Jia, Colloids Surf. A 360 (2010) 1e5.
Contents lists available at ScienceDirect
Solid State Sciences journal homepage: www.elsevier.com/locate/ssscie
Preparation of MXene-Cu2O nanocomposite and effect on thermal decomposition of ammonium perchlorate Yupeng Gao, Libo Wang*, Zhengyang Li, Aiguo Zhou, Qianku Hu, Xinxin Cao School of Materials Science and Engineering, Henan Polytechnic University, Jiaozuo, Henan 454000, China
a r t i c l e i n f o
a b s t r a c t
Article history: Received 21 February 2014 Received in revised form 11 June 2014 Accepted 15 June 2014 Available online 8 July 2014
MXenes are novel graphene-like 2-D materials. Cu2O is an effective additive for thermal decomposition of ammonium perchlorate (AP). We reported the synthesis of MXene (Ti3C2), Cu2O and MXene-Cu2O respectively. The samples were characterized by means of X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM). Results indicate that the MXene is composed of lots of nanosheets and the thickness is 30 ± 10 nm, and Cu2O nanoparticles nucleate and grow heterogeneously directly on the surface of MXene. The effect of these MXene, Cu2O and MXene-Cu2O samples on the thermal decomposition of AP were investigated using TG-DSC. The results revealed that MXene-Cu2O have a great influence on the thermal decomposition of AP than that of pure MXene and Cu2O. © 2014 Elsevier Masson SAS. All rights reserved.
Keywords: MXene Cu2O Nanocomposite Microstructure Thermal analysis
1. Introduction MXenes are novel graphene-like two-dimensional (2D) transition metal carbides [1]. The 2D materials were made from MAX phases (Ti3AlC2, Ti2AlC, Ta4AlC3, (Ti0.5,Nb0.5)2AlC, (V0.5,Cr0.5)3AlC2, and Ti3AlCN) by HF exfoliating [1,2]. Because of the graphene-like morphology, MXenes are expected to be applied extensively in many areas. It is indicated that MXenes are very promising anode materials for lithium-ion battery [3e5], hydrogen storage materials [6], high capacitors electrode materials [7], and lead adsorption materials [8]. As a p-type semiconductor, Cu2O has been widely used in many fields, such as gas sensing [9e11], catalysis [12,13], electrochemical sensing [14e16], negative electrode materials [17,18], and solar energy conversion [19] due to its unique optical and electrical properties. Recently, graphene-based inorganic oxide composites become one of the most important research frontiers in the application of graphene [20e23]. Taking into account the excellent individual properties of graphene and oxide, the combination of graphene with oxide nanoparticles could give enhanced performances. However there is no report on the MXene-based inorganic oxide composites. Ammonium perchlorate (NH4ClO4 or AP) is an important energetic material which widely used in solid rocket propellants. The
* Corresponding author. Tel./fax: þ86 391 3986910. E-mail address: [email protected] (L. Wang). http://dx.doi.org/10.1016/j.solidstatesciences.2014.06.014 1293-2558/© 2014 Elsevier Masson SAS. All rights reserved.
decomposition of AP are mainly affected by the types of the catalyst, such as Ni, NiO, Fe2O3, MnO2, CuFe2O4 and et al. [24e28] which can decrease the pyrolysis temperature and increase the combustion efficiency. Among them, Cu2O [29] show excellent catalytic effect on the thermal decomposition of AP. MXene has a large specific surface area for nanoparticles to spread and distribute on. Up to now, to the best of our knowledge the catalytic behavior of MXene-Cu2O nanocomposite in the thermal decomposition of AP has not been reported. Therefore, it is attractive to have a study on MXene-Cu2O nanocomposite as effective catalyst for thermal decomposition of AP. In this work, we reported the synthesis of MXene, Cu2O and MXene-Cu2O, and their effect on the thermal decomposition of AP. The results showed that MXene-Cu2O exhibited more excellent performance of the thermal decomposition of AP compared with MXene and Cu2O alone.
2. Experimental 2.1. Materials Copper acetate (Cu(CH3COO)2$H2O), glucose (C6H12O6), hydrofluoric acid (HF, 49 wt. % in H2O) and ammonium perchlorate (NH4ClO4) were purchased from Shanghai Chemical Reagents Company, China. All the experimental materials were of analytical grade and used without further purification. Ti3AlC2 was lab-made
Y. Gao et al. / Solid State Sciences 35 (2014) 62e65
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separated by centrifugation, washed with water and ethanol several times, and dried at 70 C in vacuum. Preparation of MXene-Cu2O: 0.1 g MXene, 0.005 mol Cu(CH3COO)2$H2O and 0.01 mol C6H12O6 were dissolved in 100 ml distilled water in a 250 ml round-bottomed flask with magnetic stirring. After stirred for 12 h at room temperature, the mixed transparent solution was heated to 90 C and kept for 5 h. Then the product was separated by centrifugation, washed with water and ethanol several times, and dried at 70 C in vacuum. Preparation of AP/(MXene, Cu2O, MXene-Cu2O) mixtures: 0.01 g MXene, Cu2O or MXene-Cu2O was mixed with 0.49 g of AP, respectively, and ground in an agate mortar. A little acetone was added into the mixtures during the grinding. Then the mixtures were dried in a vacuum oven at 50 C for 12 h. 2.3. Characterization Fig. 1. XRD patterns of the samples.
powders by pressureless sintering in a tube furnace from the mixture of TiH2, Al and C [30]. 2.2. Preparation of MXene, Cu2O, MXene-Cu2O and AP/(Mxene, Cu2O, MXene-Cu2O) mixtures Preparation of MXene: Ten grams of Ti3AlC2 were immersed in 100 ml 49% HF solutions, stirred for 1 min, and then kept for 8 h at room temperature. Thereafter, the samples were centrifugally separated and washed several times with deionized water. The treated powders were dried in a vacuum drying oven. Preparation of Cu2O: In a typical experiment, 0.005 mol Cu(CH3COO)2$H2O and 0.01 mol C6H12O6 were dissolved in 100 ml distilled water in a 250 ml round-bottomed flask with magnetic stirring, then the mixed transparent solution was heated to 90 C and kept for 5 h. After heating for the desired time, the product was
The crystal structure of the obtained samples was characterized with powder X-ray diffraction (XRD, D8 X-ray diffractometer equipment with Cu Ka radiation). The morphology and microstructures of the samples were examined by field emission scanning electron microscopy (FESEM, Hitachi S4800). The catalytic performance of samples for thermal decomposition of ammonium perchlorate was evaluated using a Setaram Evolution 2400 thermal analyzer (TG-DSC), under argon flow of 20 ml/min with a heating rate of 25 K/min from room temperature to 500 C. 3. Results and discussion Fig. 1 shows XRD pattern of the synthesized samples. In Fig. 1, the diffraction peaks of Cu2O with 2q values at 29.5 , 36.4 , 42.3 , 61.3 and 73.5 correspond to the crystal plane (110), (111), (200), (220) and (311) of crystalline Cu2O, respectively (JCPDS 05-0667). The diffraction peaks of MXene with 2q values at 9.0 and 18.4 are belongs to (002) and (004) plane of Ti3C2 MXene [2]. The FESEM images of the MXene, Cu2O and MXene-Cu2O are shown in Fig. 2. From Fig. 2(A), it can be seen that the MXene is
Fig. 2. FESEM images of (A) MXene, (B) Cu2O, (C) MXene-Cu2O.
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Y. Gao et al. / Solid State Sciences 35 (2014) 62e65
composed of lots of nano-sheets and the thickness is 30 ± 10 nm. These nano-sheets stack together like papers with unequal spacing. Fig. 2(B) is the microstructure of Cu2O sample. From Fig. 2(B), Cu2O is with irregular polyhedral morphology and large polyhedrons are constructed by lots of smaller polyhedrons. The Cu2O morphology of MXene-Cu2O (Fig. 2(C)) is different from that shown in Fig. 2(B). Because of large surface area, MXene provides many nucleation sites. Therefore Cu2O heterogeneously nucleate and grow on the surface of MXene directly. Resulted Cu2O crystals are in near-sphere phase with diameter of ~100 nm, while Cu2O crystals in Fig. 2(B) are polyhedrons with size ~1 mm. The effect on AP's thermal decomposition of MXene, Cu2O and MXene-Cu2O were studied by TG-DSC method. The results are shown in Figs. 3 and 4. In Fig. 3, the endothermic peak of AP at 250 C corresponds to the crystal transformation from orthorhombic phase to cubic phase. The exothermic peaks of pure AP at 349.7 C and 462.9 C correspond to the low-temperature decomposition and the high-temperature decomposition [31]. It can be seen that MXene, Cu2O and MXene-Cu2O have obvious catalytic effect to AP's decomposition processes. If Mxene, Cu2O and MXeneCu2O are added respectively, the decomposition temperature gradually decreases. MXene has little effect on the decomposition temperature of AP. The high decomposition temperature of AP in presence of Cu2O only decreases 106.4 C. However, the high decomposition temperature of AP with MXene-Cu2O decreases 121.4 C compared to that of the pure AP. TG and DTG curves are shown in Fig. 4(A) and (B). It is shown that the presence of MXene, Cu2O and MXene-Cu2O can decrease weight-loss temperature and it can be seen that in the range from room temperature to 500 C, two weight loss steps are clearly observed for AP with MXene, Cu2O and MXene-Cu2O. Because MXene additives have no significant catalytic effect, the decrease of weight-loss temperature is not significant, only decreases 12.4 C. While Cu2O and MXene-Cu2O have high catalytic activity, and then, the addition of Cu2O and MXene-Cu2O in AP leads to significant reduction of the weight-loss temperature of decomposition. The thermal decomposition rate of AP with MXene-Cu2O nanocomposite was higher than rate of AP with Cu2O microparticles. The above analysis shows that the MXene-Cu2O nanocomposite has higher catalytic activity comparing with MXene and Cu2O. The catalysis of Cu2O is because adsorbed oxygen on the surface of Cu2O microspheres simplifies the high temperature decomposition of AP as proton acceptor and promotes the decomposition reaction. For MXene-Cu2O, the specific surface area of Cu2O nanoparticles
Fig. 4. TG and dTG curves of samples.
obtained in presence of MXene is increased, which can provide more active sites. Additionaly, due to the good thermal conductivity [8], MXene can significantly improve the heat transfer rate of reaction system. Finally, due to lamella structure, the large specific surface area of MXene is favorable to the adsorption of reactant molecule (NH3, HClO4). And MXene can promote the decomposition of HClO4 gas adsorbed on the surface of MXene layers in the high-temperature decomposition stage, which accelerated the decomposition of AP and reduces the temperature of hightemperature exothermic decomposition process. Therefore, by combining the advantages of those two materials, thermal decomposition temperature of AP is significantly reduced. 4. Conclusion In conclusion, MXene, Cu2O and MXene-Cu2O have been synthesized successfully. The as-synthesized samples were characterized by XRD and FESEM. The results show that the morphology of Cu2O was changed and the particle size decreased in the presence of MXene. The TG-DSC analysis indicates MXene-Cu2O nanocomposite has a higher catalytic activity comparing with MXene and Cu2O on the thermal decomposition of AP. Acknowledgments
Fig. 3. DSC curves of samples.
This work was supported by National Nature Science Foundation of China (51205111, 51002045), Plan for Scientific Innovation Talent of Henan Province (134100510008), Program for Innovative
Y. Gao et al. / Solid State Sciences 35 (2014) 62e65
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