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Fabrication of rectangular 2,6-diamino-3,5-dinitropyrazine-1-oxide Microtubes
Materials Letters 65 (2011) 1018–1021
Contents lists available at ScienceDirect
Materials Letters j o u r n a l h o m e p a g e : w w w. e l s ev i e r. c o m / l o c a t e / m a t l e t
Fabrication of rectangular 2,6-diamino-3,5-dinitropyrazine-1-oxide Microtubes Jin Chen 1, Zhiqiang Qiao, Lili Wang, Fude Nie, Guangcheng Yang ⁎, Hui Huang Institute of Chemical Materials, China Academy of Engineering Physics, Mianyang 621900, China
a r t i c l e
i n f o
Article history: Received 30 October 2010 Accepted 2 January 2011 Available online 6 January 2011 Keywords: Recrystallization Microstructure LLM-105 Rectangular Microtubes
a b s t r a c t Rectangular 2,6-diamino-3,5-dinitropyrazine-1-oxide (LLM-105) microtubes were prepared via a simple recrystallization process using [Bmim]CF3SO3 as good solvent and water as poor solvent. The microtube is of average diameter of about 10 μm and has a unique rectangular cross-section architecture. Based on the analysis of scanning electron microscopy (SEM) and X-ray powder diffraction (XRD), a tentative formation mechanism of rectangular LLM-105 microtubes was proposed as an etching process. Differential scanning calorimetric (DSC) and thermogravimetric (TG) curves revealed that a shift of approximately 22 °C toward lower temperature in the exothermic peak was observed for LLM-105 microtubes in comparison with LLM-105 raw material. © 2011 Elsevier B.V. All rights reserved.
1. Introduction Since the first discovery of carbon nanotubes in 1991 [1], considerable attention has been focused on the fabrication of microand nano-tube structures, owing to their unique physical and chemical properties and potential applications in the areas of electronics, optics, sensors, biological systems, and even as building blocks for nanoscale devices [2–6]. Since then, many types of nanotubes such as inorganic nanotubes, organic/polymeric and biomolecule nanotubes [7–11] have been prepared by various methods. However, those nanotubes usually possess a circular cross-section, and only a few literatures have reported the preparation of nanotubes with an exceptional rectangular crosssection. For example, Wang et al. [12] successfully synthesized rectangular WO3·H2O nanotubes by a rolling mechanism with the aid of intercalated polyaniline. Zhou et al. [13] reported the synthesis of rectangular polyaniline sub-microtubes in dilute sodium dodecyl sulfate solution by the oxidation polymerization of aniline at room temperature. Yoon et al. [14] introduced a highly crystalline rectangular nanotube structure of metal-free tetra (4-pyridyl) porphyrin by a vaporization–condensation–condensation–recrystallization process. 2,6-diamino-3,5-dinitropyrazine-1-oxide [LLM-105, Fig. 1(c)] is a realistic high-performance energetic material. It is very thermally stable and insensitive to shock, spark and friction because of intensive π conjugative system and intra- and inter-molecular hydrogen bonds between molecules [15,16]. In recent years, micro- and nano-structured energetic materials have attracted tremendous research interest for their improved performances in energy release and ignition properties ⁎ Corresponding author. Tel.: +86 816 2485072. E-mail addresses: [email protected] (J. Chen), [email protected] (G. Yang). 1 Tel.: +86 816 2485072. 0167-577X/$ – see front matter © 2011 Elsevier B.V. All rights reserved. doi:10.1016/j.matlet.2011.01.005
compared with their bulk counterpart, and potential applications in microscale energy-demanding system [17]. However, to our best knowledge, micro- and nano-structured LLM-105 have rarely been prepared, especially hollow tubular structures. In this paper, we for the first time report a facile recrystallization process for the preparation of LLM-105 microtubes with a distinctive rectangular cross-section. The rectangular microtubes may be highly desirable for microenergetic systems because the remarkable tubular microstructures may exhibit exceptional properties in energy release that are not achievable in other nanostructures. 2. Experimental LLM-105 raw material was synthesized as reported [18], with a purity of 97.0%. Main impurities in raw material was 2,6-diamino-3, 5-dinitropyrazine. 1-butyl-3-methylimidazolium trifluoromethanesulfonate ([Bmim]CF3SO3, ≥98.0%, Merck) was used as-received. Ultra-pure water with a resistivity of 18.2 MΩ cm was produced using a Milli-Q apparatus (Millipore). In a typical process, a solution of LLM-105 was prepared by dissolving 0.03 g LLM-105 raw material in 7.5 mL [Bmim]CF3SO3 at the temperature of 90 °C. 15 mL of ultra-pure water of 90 °C was added into the solution under magnetic stirring by using a micro-sampling peristaltic pump (Cole-Parmer 78001-30). After cooled down to room temperature, a yellow solid was formed. The product of powder was finally obtained by filtration, washing with ultra-pure water and drying in vacuum oven. Morphologies of LLM-105 samples were examined by scanning electron microscope (SEM, Hitachi TM-1000). X-ray powder diffraction (XRD) patterns were recorded on a Bruker D8 Advance diffractometer with Cu Kα radiation (λ = 0.15406 nm). The differential scanning calorimetry/thermogravimetry (DSC/TG) analysis on the LLM-105
J. Chen et al. / Materials Letters 65 (2011) 1018–1021
Fig. 1. SEM images of (a) the prepared rectangular LLM-105 microtubes (inset: enlarged SEM image showing the open tip and rectangular cross-section); (b) LLM-105 raw material; (c) molecular structure of LLM-105 [16].
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material. The sharp peaks in pattern (a) prove that the LLM-105 microtubes are well-crystalline. By comparing (a) and (b), it can be observed that the relative intensity of most diffraction peaks, excepting the peaks at 2θ = 11.0° and 21.2°, become very weak for rectangular microtubes. The sharp peak at 2θ = 11.0° can be assigned to the center distance between adjacent LLM-105 molecules which arrange orderly to form layers via intermolecular N–H···O hydrogen bonds. The other sharp peak at 2θ = 21.2° can be attributed to the periodic distance between layers that are formed via π–π stacking interaction of LLM-105 molecules [15]. Thus, it can be concluded that the molecular arrangement becomes more ordered in rectangular microtubes than in the raw material. The strong intermolecular hydrogen bonds and π–π interaction induce the LLM-105 molecules to self-assemble orderly on specific crystal faces in the formation process of the rectangular microtubes. To gain insight into the formation mechanism of the rectangular LLM-105 microtubes, the morphologies of products collected at different reaction stages were observed by SEM (Fig. 3). The reaction with 10 min primarily generated rectangular microrods with a diameter of 7 μm [Fig. 3(a)]. By prolonging the reaction time to 20 min, the ends of some microrods curved inwards [Fig. 3(b)]. After about 60 min, hollow tubular structures with rectangular crosssection were obtained with a diameter of about 10 μm [Fig. 3(c)]. On the basis of the above time-dependent morphology evolution, the formation process of LLM-105 microtubes can be proposed as follows: the etching of LLM-105 by [Bmim]CF3SO3 has occurred in this process. It starts at the center of the rectangular microrods and toward the interior along the length axis, until hollow tubular structures are formed [Fig. 3(d)]. The process is similar to the etching process occurring in DAPMP microtubes [19] and hematite nanotubes [20]. The etching process may be caused by crystal defects, as happening in the formation of ZnO nanodisks. Etching was induced at the center of the rectangular microrods with a high rate since there probably existed a high density of defects [21]. Furthermore, the diameter of the final microtubes was larger than that of the initial microrods, which indicates that the recrystallization and the etching process occurred simultaneously. The thermal properties of the rectangular LLM-105 microtubes and LLM-105 raw material were investigated by DSC/TG. Fig. 4 shows the thermal analysis results. Two exotherms appear in the LLM-105 raw material. One occurs between 276.2 °C and 296.8 °C, assigned to the decomposition of 2,6-diamino-3,5-dinitropyrazine which remains in raw material; the other between 339.5 °C and 375.5 °C, corresponding to the decomposition of LLM-105 raw material. However, only a single exotherm forms in LLM-105 microtubes, indicating that the
samples were carried out by a simultaneous thermal analyzer (NETZSCH STA 449C). 3. Results and discussion The SEM images reveal that LLM-105 microtubes with rectangular cross-section [Fig. 1(a)] can be formed from the raw material of irregular morphology [Fig. 1(b)]. The rectangular LLM-105 microtubes are of high morphology purity, and the average diameter and wall thickness are approximately 10 μm and 1 μm, respectively, and the length exceeds 150 μm. No surfactant, template, or catalyst was employed in the preparation process. Only two solvents ([Bmim] CF3SO3 and water) were used besides the LLM-105 raw material. It is expected that LLM-105 molecules gradually segregated from [Bmim] CF3SO3 with dripping of water, and self-assembled into microtubes in water, as LLM-105 is virtually insoluble in water. Fig. 2(a) and (b) show the XRD patterns of the rectangular LLM-105 microtubes and LLM-105 raw material, respectively. The XRD patterns indicate that the peaks of rectangular microtubes have completely the same diffraction angles as those of the raw material, implying that rectangular microtube is of the same crystal structure as the raw
Fig. 2. XRD patterns of (a) the rectangular LLM-105 microtubes; and (b) LLM-105 raw material.
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J. Chen et al. / Materials Letters 65 (2011) 1018–1021
Fig. 3. Morphology evolution of the rectangular LLM-105 microtubes with reaction time: SEM images of the products obtained after (a) 10 min, (b) 20 min, (c) 60 min; and (d) proposed process of tube formation.
microtubes have a higher purity. The exotherm occurs in the region of 300.5 °C–346 °C, with a peak value at 330.6 °C. Comparing with the raw material, the exothermic peak shifts to lower temperature by approximately 22 °C. Furthermore, the weight loss of microtubes takes place at about 240 °C, while the starting temperature of raw material is about 270 °C. It indicates that hollow tubular structures make LLM-105 decompose at a lower temperature. In contrast with raw material, the microtubes have a larger specific surface area and thin walls with a thinness of only about 1 μm, and the hollow structure can be considered as a type of crystal defect. These factors may affect the thermal properties of LLM-105 microtubes and result in the decrease of thermal decomposition temperature. Significantly, such interesting thermal properties suggest that the LLM-105
microtubes may be a better form of LLM-105 for microenergetics applications. 4. Conclusion In summary, rectangular LLM-105 microtubes with a mean diameter of about 10 μm were prepared via a simple recrystallization process. The changes of peak intensity in XRD patterns probably originated the ordered self-assembly of LLM-105 molecules on specific crystal faces. A tentative formation mechanism of rectangular LLM-105 microtubes was proposed as an etching process caused by [Bmim]CF3SO3. The rectangular LLM-105 microtubes have lower thermal decomposition temperature that may find applications in microenergetic system. Acknowledgments This work was supported by the Key Foundation of China Academy of Engineering Physics (grant nos. 2009A0302017 and 2010B03007) and a grant from the Institute of Chemical Materials, China (grant no. 626010929). References
Fig. 4. Thermal analysis results of rectangular LLM-105 microtubes and LLM-105 raw material: (a) DSC curve of LLM-105 microtubes, (b) DSC curve of LLM-105 raw material, (c) TG curve of LLM-105 microtubes, (d) TG curve of LLM-105 raw material.
[1] Sumio I. Nature 1991;354:56–8. [2] Fan YC, Zhao MW, He T, Wang ZH, Zhang XJ, Xi ZX, et al. J Appl Phys 2010;107: 094304 (6 pp). [3] Zhao YS, Xu JJ, Peng AD, Fu HB, Ma Y, Jiang L, et al. Angew Chem Int Ed 2008;47: 7301–5. [4] Tian YS, Hu CG, He XS, Cao CL, Huang GSH, Zhang KY. Sens Actuators, B 2010;144: 203–7. [5] Song YY, Stein FS, Bauer S, Schmuki P. J Am Chem Soc 2009;131:4230–2. [6] Alireza N, Gregory LW, Shu P, Kyeongjae C, Fabian PWR. Nano Lett 2003;3: 1187–90. [7] Zhai TY, Gu ZJ, Ma Y, Yang WS, Anisimov AS, Franssila S, et al. Mater Chem Phys 2006;100:281–4.
J. Chen et al. / Materials Letters 65 (2011) 1018–1021 [8] Zeng J, Liu CH, Huang JL, Wang XP, Zhang SY, Li GP, et al. Nano Lett 2008;8: 1318–22. [9] Liu ZQ, Zhang DH, Han S, Li CH, Lei B, Lu WG, et al. J Am Chem Soc 2005;127:6–7. [10] Bong DT, Clark TD, Granja JR, Ghadiri MR. Angew Chem Int Ed 2001;40:988–1011. [11] Shimizu T, Masuda M, Minamikawa H. Chem Rev 2005;105:1401–43. [12] Wang ZX, Zhou SX, Wu LM. Adv Funct Mater 2007;17:1790–4. [13] Zhou CQ, Han J, Guo R. J Phys Chem B 2008;112:5014–9. [14] Yoon SM, Hwang IC, Kim KS, Choi HC. Angew Chem Int Ed 2009;48:2506–9. [15] Averkiev BB, Antipin MY, Yudin IL, Sheremetev AB. J Mol Struct 2002;606:139–46. [16] Tran TD, Pagoria PF, Hoffman DM, Cunningham B, Simpson RL, Lee RS, et al. Livermore (CA): Lawrence Livermore National Laboratory; Report No. : CA 94551.
1021
[17] Rossi C, Zhang KL, Estève D, Alphonse P, Tailhades P, Vahlas C. J Microelectromech Syst 2007;16:919–31. [18] Pagoria PF, Lee GS, Mitchell AR, Schmidt RD. Presented at the Insensitive Munition and Energetic Materials Technology Symposium; 2001 October 8-11; Bordeaux, France. [19] Zhang XJ, Zhang XH, Shi WSH, Meng XM, Lee CS, Lee S. Angew Chem Int Ed 2007;46:1525–8. [20] Jia CJ, Sun LD, Yan ZG, You LP, Luo F, Han XD, et al. Angew Chem 2005;117:4402–7. [21] Li F, Ding Y, Gao PX, Xin XQ, Wang ZL. Angew Chem 2004;116:5350–4.
Contents lists available at ScienceDirect
Materials Letters j o u r n a l h o m e p a g e : w w w. e l s ev i e r. c o m / l o c a t e / m a t l e t
Fabrication of rectangular 2,6-diamino-3,5-dinitropyrazine-1-oxide Microtubes Jin Chen 1, Zhiqiang Qiao, Lili Wang, Fude Nie, Guangcheng Yang ⁎, Hui Huang Institute of Chemical Materials, China Academy of Engineering Physics, Mianyang 621900, China
a r t i c l e
i n f o
Article history: Received 30 October 2010 Accepted 2 January 2011 Available online 6 January 2011 Keywords: Recrystallization Microstructure LLM-105 Rectangular Microtubes
a b s t r a c t Rectangular 2,6-diamino-3,5-dinitropyrazine-1-oxide (LLM-105) microtubes were prepared via a simple recrystallization process using [Bmim]CF3SO3 as good solvent and water as poor solvent. The microtube is of average diameter of about 10 μm and has a unique rectangular cross-section architecture. Based on the analysis of scanning electron microscopy (SEM) and X-ray powder diffraction (XRD), a tentative formation mechanism of rectangular LLM-105 microtubes was proposed as an etching process. Differential scanning calorimetric (DSC) and thermogravimetric (TG) curves revealed that a shift of approximately 22 °C toward lower temperature in the exothermic peak was observed for LLM-105 microtubes in comparison with LLM-105 raw material. © 2011 Elsevier B.V. All rights reserved.
1. Introduction Since the first discovery of carbon nanotubes in 1991 [1], considerable attention has been focused on the fabrication of microand nano-tube structures, owing to their unique physical and chemical properties and potential applications in the areas of electronics, optics, sensors, biological systems, and even as building blocks for nanoscale devices [2–6]. Since then, many types of nanotubes such as inorganic nanotubes, organic/polymeric and biomolecule nanotubes [7–11] have been prepared by various methods. However, those nanotubes usually possess a circular cross-section, and only a few literatures have reported the preparation of nanotubes with an exceptional rectangular crosssection. For example, Wang et al. [12] successfully synthesized rectangular WO3·H2O nanotubes by a rolling mechanism with the aid of intercalated polyaniline. Zhou et al. [13] reported the synthesis of rectangular polyaniline sub-microtubes in dilute sodium dodecyl sulfate solution by the oxidation polymerization of aniline at room temperature. Yoon et al. [14] introduced a highly crystalline rectangular nanotube structure of metal-free tetra (4-pyridyl) porphyrin by a vaporization–condensation–condensation–recrystallization process. 2,6-diamino-3,5-dinitropyrazine-1-oxide [LLM-105, Fig. 1(c)] is a realistic high-performance energetic material. It is very thermally stable and insensitive to shock, spark and friction because of intensive π conjugative system and intra- and inter-molecular hydrogen bonds between molecules [15,16]. In recent years, micro- and nano-structured energetic materials have attracted tremendous research interest for their improved performances in energy release and ignition properties ⁎ Corresponding author. Tel.: +86 816 2485072. E-mail addresses: [email protected] (J. Chen), [email protected] (G. Yang). 1 Tel.: +86 816 2485072. 0167-577X/$ – see front matter © 2011 Elsevier B.V. All rights reserved. doi:10.1016/j.matlet.2011.01.005
compared with their bulk counterpart, and potential applications in microscale energy-demanding system [17]. However, to our best knowledge, micro- and nano-structured LLM-105 have rarely been prepared, especially hollow tubular structures. In this paper, we for the first time report a facile recrystallization process for the preparation of LLM-105 microtubes with a distinctive rectangular cross-section. The rectangular microtubes may be highly desirable for microenergetic systems because the remarkable tubular microstructures may exhibit exceptional properties in energy release that are not achievable in other nanostructures. 2. Experimental LLM-105 raw material was synthesized as reported [18], with a purity of 97.0%. Main impurities in raw material was 2,6-diamino-3, 5-dinitropyrazine. 1-butyl-3-methylimidazolium trifluoromethanesulfonate ([Bmim]CF3SO3, ≥98.0%, Merck) was used as-received. Ultra-pure water with a resistivity of 18.2 MΩ cm was produced using a Milli-Q apparatus (Millipore). In a typical process, a solution of LLM-105 was prepared by dissolving 0.03 g LLM-105 raw material in 7.5 mL [Bmim]CF3SO3 at the temperature of 90 °C. 15 mL of ultra-pure water of 90 °C was added into the solution under magnetic stirring by using a micro-sampling peristaltic pump (Cole-Parmer 78001-30). After cooled down to room temperature, a yellow solid was formed. The product of powder was finally obtained by filtration, washing with ultra-pure water and drying in vacuum oven. Morphologies of LLM-105 samples were examined by scanning electron microscope (SEM, Hitachi TM-1000). X-ray powder diffraction (XRD) patterns were recorded on a Bruker D8 Advance diffractometer with Cu Kα radiation (λ = 0.15406 nm). The differential scanning calorimetry/thermogravimetry (DSC/TG) analysis on the LLM-105
J. Chen et al. / Materials Letters 65 (2011) 1018–1021
Fig. 1. SEM images of (a) the prepared rectangular LLM-105 microtubes (inset: enlarged SEM image showing the open tip and rectangular cross-section); (b) LLM-105 raw material; (c) molecular structure of LLM-105 [16].
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material. The sharp peaks in pattern (a) prove that the LLM-105 microtubes are well-crystalline. By comparing (a) and (b), it can be observed that the relative intensity of most diffraction peaks, excepting the peaks at 2θ = 11.0° and 21.2°, become very weak for rectangular microtubes. The sharp peak at 2θ = 11.0° can be assigned to the center distance between adjacent LLM-105 molecules which arrange orderly to form layers via intermolecular N–H···O hydrogen bonds. The other sharp peak at 2θ = 21.2° can be attributed to the periodic distance between layers that are formed via π–π stacking interaction of LLM-105 molecules [15]. Thus, it can be concluded that the molecular arrangement becomes more ordered in rectangular microtubes than in the raw material. The strong intermolecular hydrogen bonds and π–π interaction induce the LLM-105 molecules to self-assemble orderly on specific crystal faces in the formation process of the rectangular microtubes. To gain insight into the formation mechanism of the rectangular LLM-105 microtubes, the morphologies of products collected at different reaction stages were observed by SEM (Fig. 3). The reaction with 10 min primarily generated rectangular microrods with a diameter of 7 μm [Fig. 3(a)]. By prolonging the reaction time to 20 min, the ends of some microrods curved inwards [Fig. 3(b)]. After about 60 min, hollow tubular structures with rectangular crosssection were obtained with a diameter of about 10 μm [Fig. 3(c)]. On the basis of the above time-dependent morphology evolution, the formation process of LLM-105 microtubes can be proposed as follows: the etching of LLM-105 by [Bmim]CF3SO3 has occurred in this process. It starts at the center of the rectangular microrods and toward the interior along the length axis, until hollow tubular structures are formed [Fig. 3(d)]. The process is similar to the etching process occurring in DAPMP microtubes [19] and hematite nanotubes [20]. The etching process may be caused by crystal defects, as happening in the formation of ZnO nanodisks. Etching was induced at the center of the rectangular microrods with a high rate since there probably existed a high density of defects [21]. Furthermore, the diameter of the final microtubes was larger than that of the initial microrods, which indicates that the recrystallization and the etching process occurred simultaneously. The thermal properties of the rectangular LLM-105 microtubes and LLM-105 raw material were investigated by DSC/TG. Fig. 4 shows the thermal analysis results. Two exotherms appear in the LLM-105 raw material. One occurs between 276.2 °C and 296.8 °C, assigned to the decomposition of 2,6-diamino-3,5-dinitropyrazine which remains in raw material; the other between 339.5 °C and 375.5 °C, corresponding to the decomposition of LLM-105 raw material. However, only a single exotherm forms in LLM-105 microtubes, indicating that the
samples were carried out by a simultaneous thermal analyzer (NETZSCH STA 449C). 3. Results and discussion The SEM images reveal that LLM-105 microtubes with rectangular cross-section [Fig. 1(a)] can be formed from the raw material of irregular morphology [Fig. 1(b)]. The rectangular LLM-105 microtubes are of high morphology purity, and the average diameter and wall thickness are approximately 10 μm and 1 μm, respectively, and the length exceeds 150 μm. No surfactant, template, or catalyst was employed in the preparation process. Only two solvents ([Bmim] CF3SO3 and water) were used besides the LLM-105 raw material. It is expected that LLM-105 molecules gradually segregated from [Bmim] CF3SO3 with dripping of water, and self-assembled into microtubes in water, as LLM-105 is virtually insoluble in water. Fig. 2(a) and (b) show the XRD patterns of the rectangular LLM-105 microtubes and LLM-105 raw material, respectively. The XRD patterns indicate that the peaks of rectangular microtubes have completely the same diffraction angles as those of the raw material, implying that rectangular microtube is of the same crystal structure as the raw
Fig. 2. XRD patterns of (a) the rectangular LLM-105 microtubes; and (b) LLM-105 raw material.
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J. Chen et al. / Materials Letters 65 (2011) 1018–1021
Fig. 3. Morphology evolution of the rectangular LLM-105 microtubes with reaction time: SEM images of the products obtained after (a) 10 min, (b) 20 min, (c) 60 min; and (d) proposed process of tube formation.
microtubes have a higher purity. The exotherm occurs in the region of 300.5 °C–346 °C, with a peak value at 330.6 °C. Comparing with the raw material, the exothermic peak shifts to lower temperature by approximately 22 °C. Furthermore, the weight loss of microtubes takes place at about 240 °C, while the starting temperature of raw material is about 270 °C. It indicates that hollow tubular structures make LLM-105 decompose at a lower temperature. In contrast with raw material, the microtubes have a larger specific surface area and thin walls with a thinness of only about 1 μm, and the hollow structure can be considered as a type of crystal defect. These factors may affect the thermal properties of LLM-105 microtubes and result in the decrease of thermal decomposition temperature. Significantly, such interesting thermal properties suggest that the LLM-105
microtubes may be a better form of LLM-105 for microenergetics applications. 4. Conclusion In summary, rectangular LLM-105 microtubes with a mean diameter of about 10 μm were prepared via a simple recrystallization process. The changes of peak intensity in XRD patterns probably originated the ordered self-assembly of LLM-105 molecules on specific crystal faces. A tentative formation mechanism of rectangular LLM-105 microtubes was proposed as an etching process caused by [Bmim]CF3SO3. The rectangular LLM-105 microtubes have lower thermal decomposition temperature that may find applications in microenergetic system. Acknowledgments This work was supported by the Key Foundation of China Academy of Engineering Physics (grant nos. 2009A0302017 and 2010B03007) and a grant from the Institute of Chemical Materials, China (grant no. 626010929). References
Fig. 4. Thermal analysis results of rectangular LLM-105 microtubes and LLM-105 raw material: (a) DSC curve of LLM-105 microtubes, (b) DSC curve of LLM-105 raw material, (c) TG curve of LLM-105 microtubes, (d) TG curve of LLM-105 raw material.
[1] Sumio I. Nature 1991;354:56–8. [2] Fan YC, Zhao MW, He T, Wang ZH, Zhang XJ, Xi ZX, et al. J Appl Phys 2010;107: 094304 (6 pp). [3] Zhao YS, Xu JJ, Peng AD, Fu HB, Ma Y, Jiang L, et al. Angew Chem Int Ed 2008;47: 7301–5. [4] Tian YS, Hu CG, He XS, Cao CL, Huang GSH, Zhang KY. Sens Actuators, B 2010;144: 203–7. [5] Song YY, Stein FS, Bauer S, Schmuki P. J Am Chem Soc 2009;131:4230–2. [6] Alireza N, Gregory LW, Shu P, Kyeongjae C, Fabian PWR. Nano Lett 2003;3: 1187–90. [7] Zhai TY, Gu ZJ, Ma Y, Yang WS, Anisimov AS, Franssila S, et al. Mater Chem Phys 2006;100:281–4.
J. Chen et al. / Materials Letters 65 (2011) 1018–1021 [8] Zeng J, Liu CH, Huang JL, Wang XP, Zhang SY, Li GP, et al. Nano Lett 2008;8: 1318–22. [9] Liu ZQ, Zhang DH, Han S, Li CH, Lei B, Lu WG, et al. J Am Chem Soc 2005;127:6–7. [10] Bong DT, Clark TD, Granja JR, Ghadiri MR. Angew Chem Int Ed 2001;40:988–1011. [11] Shimizu T, Masuda M, Minamikawa H. Chem Rev 2005;105:1401–43. [12] Wang ZX, Zhou SX, Wu LM. Adv Funct Mater 2007;17:1790–4. [13] Zhou CQ, Han J, Guo R. J Phys Chem B 2008;112:5014–9. [14] Yoon SM, Hwang IC, Kim KS, Choi HC. Angew Chem Int Ed 2009;48:2506–9. [15] Averkiev BB, Antipin MY, Yudin IL, Sheremetev AB. J Mol Struct 2002;606:139–46. [16] Tran TD, Pagoria PF, Hoffman DM, Cunningham B, Simpson RL, Lee RS, et al. Livermore (CA): Lawrence Livermore National Laboratory; Report No. : CA 94551.
1021
[17] Rossi C, Zhang KL, Estève D, Alphonse P, Tailhades P, Vahlas C. J Microelectromech Syst 2007;16:919–31. [18] Pagoria PF, Lee GS, Mitchell AR, Schmidt RD. Presented at the Insensitive Munition and Energetic Materials Technology Symposium; 2001 October 8-11; Bordeaux, France. [19] Zhang XJ, Zhang XH, Shi WSH, Meng XM, Lee CS, Lee S. Angew Chem Int Ed 2007;46:1525–8. [20] Jia CJ, Sun LD, Yan ZG, You LP, Luo F, Han XD, et al. Angew Chem 2005;117:4402–7. [21] Li F, Ding Y, Gao PX, Xin XQ, Wang ZL. Angew Chem 2004;116:5350–4.