- Email: [email protected]
Fabrication of hexagonally arranged porous carbon films by proton beam irradiation and carbonization
Radiation Physics and Chemistry 163 (2019) 18–21
Contents lists available at ScienceDirect
Radiation Physics and Chemistry journal homepage: www.elsevier.com/locate/radphyschem
Fabrication of hexagonally arranged porous carbon films by proton beam irradiation and carbonization
T
Byoung-Min Leea, Van-Tien Buib,c, Hwa Su Leea, Sung-Kwon Honga, Ho-Suk Choib,∗∗, Jae-Hak Choia,∗ a
Department of Polymer Science and Engineering, Chungnam National University, Daejeon, 34134, South Korea Department of Chemical Engineering and Applied Chemistry, Chungnam National University, Daejeon, 34134, South Korea c Faculty of Materials Technology, National Key Lab. of Polymer and Composite Materials, HoChiMinh University of Technology, Vietnam National University, HoChiMinh City, Viet Nam b
A R T I C LE I N FO
A B S T R A C T
Keywords: Proton beam irradiation Carbonization Polystyrene Improved phase separation Hexagonal array
Hexagonally-arranged porous carbon films (HaPCFs) were prepared by proton beam irradiation and carbonization of hexagonally-arranged porous polystyrene films (HaPPSFs). HaPPSFs prepared by an improved phase separation method were irradiated with 150-keV proton beam at a fluence of 4 × 1016 ions cm−2 to enhance the thermal stability for high-temperature carbonization. Proton beam irradiation of HaPPSFs was found to induce crosslinking and surface oxidation reactions. The proton beam-irradiated HaPPSFs were carbonized at 800 °C under an inert atmosphere, resulting in the formation of HaPCFs. The prepared HaPCFs were found to have pseudo-graphitic structures containing both ordered and disordered graphitic structures. The prepared HaPCFs showed a good electrical conductivity.
1. Introduction Hexagonally-arranged porous carbons films (HaPCFs) have attracted much attention because of their potential applications in lithium ion batteries (Ramakrishnan et al., 2017), supercapacitors (Sheng et al., 2017), dye-sensitized solar cells (Cha et al., 2018), and CO2 capture (Tian et al., 2016). HaPCFs are generally fabricated by carbonization of hexagonally-arranged porous polymer films prepared by various methods, such as breath-figure, improved phase separation, templating, and UV lithography (Escalé et al., 2012). Among them, an improved phase separation (IPS) method is the most promising approach for the mass production of highly-ordered hexagonally-arranged porous polymer films under an ambient air condition. Various polymer films with large-scale, hexagonally-arranged porous structures were successfully prepared by this IPS method (Bui et al., 2015, 2017). However, the crosslinking of polymer films is necessary to enhance the thermal stability for high-temperature carbonization. Typical crosslinking methods include photo-crosslinking, thermal crosslinking, and radiation (electron or ion beam) crosslinking. Among them, radiation crosslinking based on proton beam irradiation is the most powerful method to crosslink polymers at room temperature without the use of initiators and crosslinkers. Furthermore, carbon clusters consisting of ∗
sp2-and sp3-carbon structures formed by proton beam irradiation at a high fluence are converted into graphitic carbon structures by hightemperature carbonization. Recently, carbon films and patterns have been prepared by the carbonization of proton beam-irradiated polymer films and patterns, respectively (Jung et al., 2015, 2016; Lee et al., 2018). In this study, for the first time, HaPCFs were prepared from a cheap and commercially-available polystyrene (PS) by proton beam irradiation and carbonization. Hexagonally-arranged porous PS films (HaPPSFs) prepared by the IPS method were irradiated with proton beam to crosslink HaPPSFs at room temperature and then carbonized at a high temperature under an inert atmosphere, resulting in the formation of HaPCFs. The prepared HaPCFs were characterized in terms of their chemical structures and elements, surface morphology, carbon and crystalline structures, and conductivity. 2. Experimental PS pellets (15NFI, Mw: 35,000) were purchased from LG Chemicals Company. Chloroform and methanol were supplied by Sigma-Aldrich. HaPPSFs were prepared by the IPS method according to the method reported in our recent paper (Bui et al., 2015). The HaPPSFs on SiO2/Si
Corresponding author. Corresponding author. E-mail addresses: [email protected] (H.-S. Choi), [email protected] (J.-H. Choi).
∗∗
https://doi.org/10.1016/j.radphyschem.2019.05.006 Received 21 September 2018; Received in revised form 20 March 2019; Accepted 2 May 2019 Available online 08 May 2019 0969-806X/ © 2019 Elsevier Ltd. All rights reserved.
Radiation Physics and Chemistry 163 (2019) 18–21
B.-M. Lee, et al.
sheet resistance were observed using a field-emission scanning electron microscope (FE-SEM, (Merlin Compact, ZEISS, Germany) and a 4-point probe surface resistivity meter (CMT-SR1000N, Advanced Instrument Technologies, Korea).
3. Results and discussion 3.1. FT-IR and XPS Changes in the chemical structures of HaPPSFs resulting from proton beam irradiation were investigated by ATR-FTIR spectroscopy. As shown in Fig. 1, the ATR-FTIR spectra of the HaPPSFs show characteristic peaks at 3025 (aromatic CH), 2921 (aliphatic C–H), 1600 to 1450 (aromatic rings), and 752 cm−1 (=C–H), respectively. For PIHaPPSFs, new peaks appeared at 1716 and 1665 cm−1 corresponding to C]O and C]C, respectively, due to the surface oxidation and dehydrogenation of PS resulting from proton beam irradiation (Song et al., 2015). XPS analysis was carried out to further investigate the changes in the chemical elements brought about by proton beam irradiation and carbonization, and the results are shown in Fig. 2. As seen in Fig. 2a, the atomic percentages of carbon (283 eV) and oxygen (537 eV) of HaPPSFs were 96.56% and 3.44%, respectively. In case of the PI-HaPPSFs, the oxygen content increased to 16.88% and the carbon content decreased to 83.12% due to the surface oxidation of the HaPPSFs after proton beam irradiation. After carbonization, the carbon content increased to 94.16%, while the oxygen content decreased to 5.84% due to the removal of non-carbon elements during carbonization. Therefore, the [O]/[C] ratio of HaPCFs decreased to 0.06, indicating the formation of HaPCFs composed of mostly carbon atoms by carbonization. As shown in Fig. 2b, the HaPPSFs showed characteristic peaks corresponding to the chemical structure of pristine PS at 285 eV (C–C/C–H) and 291.8 eV (satellite π - π*) (McGettrick et al., 2017; Kim et al., 2016). In the case
Fig. 1. ATR-FTIR spectra of HaPPSFs and PI-HaPPSFs.
wafers were irradiated with 150-keV proton beam using a 300-keV ion implanter (Advanced Radiation Technology Institute, Korea Atomic Energy Research Institute) at a dose of 4 × 1016 ions cm−2 and a current density of 0.5 μA cm−2. The proton beam-irradiated HaPPSFs (PIHaPPSFs) were carbonized at 800 °C for 1 h in a tubular furnace (Youlsan, Korea) under a N2 atmosphere. Changes in the chemical structures and elements were investigated by using an attenuated total reflection Fourier-transform infrared spectrometer (ATR-FTIR, Spectrum Two, PerkinElmer, Korea) and an X-ray photoelectron spectrometer (XPS, MultiLab, 2000; ThermoElectron Corporation, England). Carbon and crystalline structures were analyzed by using a Raman spectrometer (LabRam ARAMIS, Horiba Jobin-Yvon, France) with an Ar-ion laser (514.5 nm) and an X-ray diffractometer (XRD, X'Pert Pro Multi-Purpose, PANalytical, Netherlands) equipped with CuKα radiation in a range of 2θ = 5–50°, respectively. The surface morphology and
Fig. 2. XPS survey spectra (a) and C1s narrow spectra of (b) HaPPSFs, (c) PI-HaPPSFs, and (d) HaPCFs. 19
Radiation Physics and Chemistry 163 (2019) 18–21
B.-M. Lee, et al.
Fig. 3. (a) Raman spectrum of HaPCFs and (b) XRD patterns of HaPPSFs, PI-HaPPSFs, and HaPCFs.
Fig. 4. FE-SEM images of (a) HaPPSFs, (b) PI-HaPPSFs, and (c–d) HaPCFs.
irradiation-induced dehydrogenation, crosslinking, and surface oxidation. In case of the HaPCFs, a broad peak at 26.4° corresponding to the (002) plane of the typical graphitic structures newly appeared (Lee et al., 2017). These results also confirmed the formation of pseudographitic carbon structures in the HaPCFs. FE-SEM images of HaPPSFs, PI-HaPPSFs, and HaPCFs are shown in Fig. 4. The diameter and depth of the structures in the HPSFs were 2.0 and 1.8 μm, respectively. In addition, the thicknesses of the walls between the structures in the HaPPSFs were 1.44 μm. After proton beam irradiation, the dimensions of the structures in the HaPPSFs were not significantly changed. However, the diameter and depth of the HaPCFs were 2.4 and 0.75 μm, respectively, due to the removal of non-carbon atoms during carbonization. These results imply that the HaPPSFs were converted HaPCFs with a significant reduction in depth and no change in diameter during carbonization. The prepared HaPCFs showed a good electrical conductivity of 68.42 S cm−1.
of PI-HaPPSFs (Fig. 2c), peaks for C]C (284.6 eV), C–C (285 eV), C–O (286.3 eV), and O–C]O (288.6 eV) newly appeared, indicating that dehydrogenation, crosslinking, and surface oxidation had occurred in the HaPPSFs due to proton beam irradiation (Kim et al., 2016; Kondyurin et al., 2008). After carbonization (Fig. 2d), a graphitic C]C peak was very dominant, whereas the intensity of other peaks was remarkable reduced. These results confirm that HaPCFs with graphitic C]C structures were successfully formed by the carbonization of PIHaPPSFs. Raman spectroscopy was employed to characterize the carbon structures of the HaPCFs (Fig. 3a). The HaPCFs showed the characteristic D- and G-bands at 1359 and 1599 cm−1, respectively. The D- and G-bands are related to disordered and graphitic carbon structures, respectively. The intensity ratio of D-band/G-band (ID/IG) was 0.92, indicating the presence of pseudo-graphitic carbon structures with both disordered and graphitic structures in the HaPCFs (Elsehly et al., 2018). To further study the crystalline structures, XRD analysis was performed, and the results are shown in Fig. 3b. A broad and strong peak around 19.2° indicates the amorphous nature of the HaPPSFs. After proton beam irradiation, this peak completely disappeared due to proton beam
4. Conclusions Highly-ordered HaPCFs were successfully prepared by sequential 20
Radiation Physics and Chemistry 163 (2019) 18–21
B.-M. Lee, et al.
IPS, proton beam irradiation, and carbonization. HaPPSFs prepared by the IPS method were irradiated with proton beam to enhance the thermal stability for high-temperature carbonization. Proton beam irradiation on HaPPSFs induced dehydrogenation, crosslinking, and the formation of carbon clusters. The PI-HaPPSFs were transformed to HaPCFs with pseudo-graphitic carbon structures by carbonization. The HaPCFs showed a high electrical conductivity of 68.42 S cm−1. The proton beam irradiation-based method is a promising method for the preparation of carbon materials with various shapes, which is desirable for application in electronic and energy devices, such as transistors, supercapacitors, batteries, and fuel cells.
Elsehly, E.M., Chechenin, N.G., Makunin, A.V., Shemukhin, A.A., Motaweh, H.A., 2018. Enhancement of CNT-based filters efficiency by ion beam irradiation. Radiat. Phys. Chem. 146, 19–25. Escalé, P., Rubatat, L., Billon, L., Save, M., 2012. Recent advances in honeycomb-structured porous polymer films prepared via breath figures. Eur. Polym. J. 48, 1001–1025. Jung, C.H., Kim, W.J., Jung, C.H., Hwang, I.T., Khim, D., Kim, D.Y., Lee, J.S., Ku, B.C., Choi, J.H., 2015. A simple PAN-based fabrication method for microstructured carbon electrodes for organic field-effect transistors. Carbon 87, 257–268. Jung, J.M., Hong, J.H., Hwang, I.T., Shin, J., Kim, Y.J., Jeong, Y.G., Jung, C.H., Choi, J.H., 2016. Facile construction of electrically-conductive carbon patterns from a cheap coal-type pitch and their application to electric heating devices. J. Ind. Eng. Chem. 39, 188–193. Kim, D., Kirakosyan, A., Choi, J., 2016. Electron-irradiated polymer brushes for hollow carbon nanosphere arrays. Macromol. Rapid Commun. 37, 1507–1512. Kondyurin, A., Gan, B.K., Bilek, M.M.M., McKenzie, D.R., Mizuno, K., Wuhrer, R., 2008. Argon plasma immersion ion implantation of polystyrene films. Nucl. Instrum. Methods Phys. Res. Sect. B Beam Interact. Mater. Atoms 266, 1074–1084. Lee, B.M., Jung, J.M., Hwang, I.T., Shin, J., Hong, S.K., Jung, C.H., Jeong, Y.G., Choi, J.H., 2018. Fabrication and electric heating behavior of carbon thin films from waters-soluble poly(vinyl alcohol) via simple dry and ambient stabilization and carbonization. Appl. Surf. Sci. 456, 561–567. Lee, H.S., Baek, G.Y., Hwang, I.T., Jung, C.H., Choi, J.H., 2017. Preparation of porous carbon films from polyacrylonitrile by proton beam irradiation and carbonization. Radiat. Phys. Chem. 141, 369–374. McGettrick, J.D., Speller, E., Li, Z., Tsoi, W.C., Durrant, J.R., Watson, T., 2017. Use of gas cluster ion source depth profiling to study the oxidation of fullerene thin films by XPS. Org. Electron. 49, 85–93. Ramakrishnan, P., Baek, S.H., Park, Y., Kim, J.H., 2017. Nitrogen and sulfur co-doped metal monochalcogen encapsulated honeycomb like carbon nanostructure as a high performance lithium ion battery anode material. Carbon 115, 249–260. Sheng, L., Jiang, L., Wei, T., Liu, Z., Fan, Z., 2017. Spatial charge storage within honeycomb-carbon frameworks for ultrafast supercapacitors with high energy and power densities. Adv. Energy Mater. 7, 1700668. Song, X., Dai, Z., Xiao, X., Li, W., Zheng, X., Shang, X., Zhang, X., Cai, G., Wu, W., Meng, F., Jiang, C., 2015. formation of carbonized polystyrene sphere/hemisphere shell arrays by ion beam irradiation and subsequent annealing or chloroform treatment. Sci. Rep. 5, 17529. Tian, W., Zhang, H., Sun, H., Suvorova, A., Saunders, M., Tade, M., Wang, S., 2016. Heteroatom (N or N-S)-Doping induced layered and honeycomb microstructures of porous carbons for CO2 capture and energy applications. Adv. Funct. Mater. 26, 8651–8661.
Acknowledgements This research was supported by a grant from the National Research Foundation (NRF) of Korea funded by the Korean government (MSIT; NRF- 2017R1A4A1015360). Appendix A. Supplementary data Supplementary data to this article can be found online at https:// doi.org/10.1016/j.radphyschem.2019.05.006. References Bui, V.T., Lee, H.S., Choi, J.H., Choi, H.S., 2015. Highly ordered and robust honeycomb films with tunable pore sizes fabricated via UV crosslinking after applying improved phase separation. Polymer 74, 46–53. Bui, V.T., Thuy, L.T., Tran, Q.C., Nguyen, V.T., Dao, V.D., Choi, J.S., Choi, H.S., 2017. Ordered honeycomb biocompatible polymer films via a one-step solution-immersion phase separation used as a scaffold for cell cultures. Chem. Eng. J. 320, 561–569. Cha, S.M., Nagaraju, G., Sekhar, S.C., Bharat, L.K., Yu, J.S., 2018. Fallen leaves derived honeycomb-like porous carbon as a metal-free and low-cost counter electrode for dye-sensitized solar cells with excellent tri-iodide reduction. J. Colloid Interface Sci. 513, 843–851.
21
Contents lists available at ScienceDirect
Radiation Physics and Chemistry journal homepage: www.elsevier.com/locate/radphyschem
Fabrication of hexagonally arranged porous carbon films by proton beam irradiation and carbonization
T
Byoung-Min Leea, Van-Tien Buib,c, Hwa Su Leea, Sung-Kwon Honga, Ho-Suk Choib,∗∗, Jae-Hak Choia,∗ a
Department of Polymer Science and Engineering, Chungnam National University, Daejeon, 34134, South Korea Department of Chemical Engineering and Applied Chemistry, Chungnam National University, Daejeon, 34134, South Korea c Faculty of Materials Technology, National Key Lab. of Polymer and Composite Materials, HoChiMinh University of Technology, Vietnam National University, HoChiMinh City, Viet Nam b
A R T I C LE I N FO
A B S T R A C T
Keywords: Proton beam irradiation Carbonization Polystyrene Improved phase separation Hexagonal array
Hexagonally-arranged porous carbon films (HaPCFs) were prepared by proton beam irradiation and carbonization of hexagonally-arranged porous polystyrene films (HaPPSFs). HaPPSFs prepared by an improved phase separation method were irradiated with 150-keV proton beam at a fluence of 4 × 1016 ions cm−2 to enhance the thermal stability for high-temperature carbonization. Proton beam irradiation of HaPPSFs was found to induce crosslinking and surface oxidation reactions. The proton beam-irradiated HaPPSFs were carbonized at 800 °C under an inert atmosphere, resulting in the formation of HaPCFs. The prepared HaPCFs were found to have pseudo-graphitic structures containing both ordered and disordered graphitic structures. The prepared HaPCFs showed a good electrical conductivity.
1. Introduction Hexagonally-arranged porous carbons films (HaPCFs) have attracted much attention because of their potential applications in lithium ion batteries (Ramakrishnan et al., 2017), supercapacitors (Sheng et al., 2017), dye-sensitized solar cells (Cha et al., 2018), and CO2 capture (Tian et al., 2016). HaPCFs are generally fabricated by carbonization of hexagonally-arranged porous polymer films prepared by various methods, such as breath-figure, improved phase separation, templating, and UV lithography (Escalé et al., 2012). Among them, an improved phase separation (IPS) method is the most promising approach for the mass production of highly-ordered hexagonally-arranged porous polymer films under an ambient air condition. Various polymer films with large-scale, hexagonally-arranged porous structures were successfully prepared by this IPS method (Bui et al., 2015, 2017). However, the crosslinking of polymer films is necessary to enhance the thermal stability for high-temperature carbonization. Typical crosslinking methods include photo-crosslinking, thermal crosslinking, and radiation (electron or ion beam) crosslinking. Among them, radiation crosslinking based on proton beam irradiation is the most powerful method to crosslink polymers at room temperature without the use of initiators and crosslinkers. Furthermore, carbon clusters consisting of ∗
sp2-and sp3-carbon structures formed by proton beam irradiation at a high fluence are converted into graphitic carbon structures by hightemperature carbonization. Recently, carbon films and patterns have been prepared by the carbonization of proton beam-irradiated polymer films and patterns, respectively (Jung et al., 2015, 2016; Lee et al., 2018). In this study, for the first time, HaPCFs were prepared from a cheap and commercially-available polystyrene (PS) by proton beam irradiation and carbonization. Hexagonally-arranged porous PS films (HaPPSFs) prepared by the IPS method were irradiated with proton beam to crosslink HaPPSFs at room temperature and then carbonized at a high temperature under an inert atmosphere, resulting in the formation of HaPCFs. The prepared HaPCFs were characterized in terms of their chemical structures and elements, surface morphology, carbon and crystalline structures, and conductivity. 2. Experimental PS pellets (15NFI, Mw: 35,000) were purchased from LG Chemicals Company. Chloroform and methanol were supplied by Sigma-Aldrich. HaPPSFs were prepared by the IPS method according to the method reported in our recent paper (Bui et al., 2015). The HaPPSFs on SiO2/Si
Corresponding author. Corresponding author. E-mail addresses: [email protected] (H.-S. Choi), [email protected] (J.-H. Choi).
∗∗
https://doi.org/10.1016/j.radphyschem.2019.05.006 Received 21 September 2018; Received in revised form 20 March 2019; Accepted 2 May 2019 Available online 08 May 2019 0969-806X/ © 2019 Elsevier Ltd. All rights reserved.
Radiation Physics and Chemistry 163 (2019) 18–21
B.-M. Lee, et al.
sheet resistance were observed using a field-emission scanning electron microscope (FE-SEM, (Merlin Compact, ZEISS, Germany) and a 4-point probe surface resistivity meter (CMT-SR1000N, Advanced Instrument Technologies, Korea).
3. Results and discussion 3.1. FT-IR and XPS Changes in the chemical structures of HaPPSFs resulting from proton beam irradiation were investigated by ATR-FTIR spectroscopy. As shown in Fig. 1, the ATR-FTIR spectra of the HaPPSFs show characteristic peaks at 3025 (aromatic CH), 2921 (aliphatic C–H), 1600 to 1450 (aromatic rings), and 752 cm−1 (=C–H), respectively. For PIHaPPSFs, new peaks appeared at 1716 and 1665 cm−1 corresponding to C]O and C]C, respectively, due to the surface oxidation and dehydrogenation of PS resulting from proton beam irradiation (Song et al., 2015). XPS analysis was carried out to further investigate the changes in the chemical elements brought about by proton beam irradiation and carbonization, and the results are shown in Fig. 2. As seen in Fig. 2a, the atomic percentages of carbon (283 eV) and oxygen (537 eV) of HaPPSFs were 96.56% and 3.44%, respectively. In case of the PI-HaPPSFs, the oxygen content increased to 16.88% and the carbon content decreased to 83.12% due to the surface oxidation of the HaPPSFs after proton beam irradiation. After carbonization, the carbon content increased to 94.16%, while the oxygen content decreased to 5.84% due to the removal of non-carbon elements during carbonization. Therefore, the [O]/[C] ratio of HaPCFs decreased to 0.06, indicating the formation of HaPCFs composed of mostly carbon atoms by carbonization. As shown in Fig. 2b, the HaPPSFs showed characteristic peaks corresponding to the chemical structure of pristine PS at 285 eV (C–C/C–H) and 291.8 eV (satellite π - π*) (McGettrick et al., 2017; Kim et al., 2016). In the case
Fig. 1. ATR-FTIR spectra of HaPPSFs and PI-HaPPSFs.
wafers were irradiated with 150-keV proton beam using a 300-keV ion implanter (Advanced Radiation Technology Institute, Korea Atomic Energy Research Institute) at a dose of 4 × 1016 ions cm−2 and a current density of 0.5 μA cm−2. The proton beam-irradiated HaPPSFs (PIHaPPSFs) were carbonized at 800 °C for 1 h in a tubular furnace (Youlsan, Korea) under a N2 atmosphere. Changes in the chemical structures and elements were investigated by using an attenuated total reflection Fourier-transform infrared spectrometer (ATR-FTIR, Spectrum Two, PerkinElmer, Korea) and an X-ray photoelectron spectrometer (XPS, MultiLab, 2000; ThermoElectron Corporation, England). Carbon and crystalline structures were analyzed by using a Raman spectrometer (LabRam ARAMIS, Horiba Jobin-Yvon, France) with an Ar-ion laser (514.5 nm) and an X-ray diffractometer (XRD, X'Pert Pro Multi-Purpose, PANalytical, Netherlands) equipped with CuKα radiation in a range of 2θ = 5–50°, respectively. The surface morphology and
Fig. 2. XPS survey spectra (a) and C1s narrow spectra of (b) HaPPSFs, (c) PI-HaPPSFs, and (d) HaPCFs. 19
Radiation Physics and Chemistry 163 (2019) 18–21
B.-M. Lee, et al.
Fig. 3. (a) Raman spectrum of HaPCFs and (b) XRD patterns of HaPPSFs, PI-HaPPSFs, and HaPCFs.
Fig. 4. FE-SEM images of (a) HaPPSFs, (b) PI-HaPPSFs, and (c–d) HaPCFs.
irradiation-induced dehydrogenation, crosslinking, and surface oxidation. In case of the HaPCFs, a broad peak at 26.4° corresponding to the (002) plane of the typical graphitic structures newly appeared (Lee et al., 2017). These results also confirmed the formation of pseudographitic carbon structures in the HaPCFs. FE-SEM images of HaPPSFs, PI-HaPPSFs, and HaPCFs are shown in Fig. 4. The diameter and depth of the structures in the HPSFs were 2.0 and 1.8 μm, respectively. In addition, the thicknesses of the walls between the structures in the HaPPSFs were 1.44 μm. After proton beam irradiation, the dimensions of the structures in the HaPPSFs were not significantly changed. However, the diameter and depth of the HaPCFs were 2.4 and 0.75 μm, respectively, due to the removal of non-carbon atoms during carbonization. These results imply that the HaPPSFs were converted HaPCFs with a significant reduction in depth and no change in diameter during carbonization. The prepared HaPCFs showed a good electrical conductivity of 68.42 S cm−1.
of PI-HaPPSFs (Fig. 2c), peaks for C]C (284.6 eV), C–C (285 eV), C–O (286.3 eV), and O–C]O (288.6 eV) newly appeared, indicating that dehydrogenation, crosslinking, and surface oxidation had occurred in the HaPPSFs due to proton beam irradiation (Kim et al., 2016; Kondyurin et al., 2008). After carbonization (Fig. 2d), a graphitic C]C peak was very dominant, whereas the intensity of other peaks was remarkable reduced. These results confirm that HaPCFs with graphitic C]C structures were successfully formed by the carbonization of PIHaPPSFs. Raman spectroscopy was employed to characterize the carbon structures of the HaPCFs (Fig. 3a). The HaPCFs showed the characteristic D- and G-bands at 1359 and 1599 cm−1, respectively. The D- and G-bands are related to disordered and graphitic carbon structures, respectively. The intensity ratio of D-band/G-band (ID/IG) was 0.92, indicating the presence of pseudo-graphitic carbon structures with both disordered and graphitic structures in the HaPCFs (Elsehly et al., 2018). To further study the crystalline structures, XRD analysis was performed, and the results are shown in Fig. 3b. A broad and strong peak around 19.2° indicates the amorphous nature of the HaPPSFs. After proton beam irradiation, this peak completely disappeared due to proton beam
4. Conclusions Highly-ordered HaPCFs were successfully prepared by sequential 20
Radiation Physics and Chemistry 163 (2019) 18–21
B.-M. Lee, et al.
IPS, proton beam irradiation, and carbonization. HaPPSFs prepared by the IPS method were irradiated with proton beam to enhance the thermal stability for high-temperature carbonization. Proton beam irradiation on HaPPSFs induced dehydrogenation, crosslinking, and the formation of carbon clusters. The PI-HaPPSFs were transformed to HaPCFs with pseudo-graphitic carbon structures by carbonization. The HaPCFs showed a high electrical conductivity of 68.42 S cm−1. The proton beam irradiation-based method is a promising method for the preparation of carbon materials with various shapes, which is desirable for application in electronic and energy devices, such as transistors, supercapacitors, batteries, and fuel cells.
Elsehly, E.M., Chechenin, N.G., Makunin, A.V., Shemukhin, A.A., Motaweh, H.A., 2018. Enhancement of CNT-based filters efficiency by ion beam irradiation. Radiat. Phys. Chem. 146, 19–25. Escalé, P., Rubatat, L., Billon, L., Save, M., 2012. Recent advances in honeycomb-structured porous polymer films prepared via breath figures. Eur. Polym. J. 48, 1001–1025. Jung, C.H., Kim, W.J., Jung, C.H., Hwang, I.T., Khim, D., Kim, D.Y., Lee, J.S., Ku, B.C., Choi, J.H., 2015. A simple PAN-based fabrication method for microstructured carbon electrodes for organic field-effect transistors. Carbon 87, 257–268. Jung, J.M., Hong, J.H., Hwang, I.T., Shin, J., Kim, Y.J., Jeong, Y.G., Jung, C.H., Choi, J.H., 2016. Facile construction of electrically-conductive carbon patterns from a cheap coal-type pitch and their application to electric heating devices. J. Ind. Eng. Chem. 39, 188–193. Kim, D., Kirakosyan, A., Choi, J., 2016. Electron-irradiated polymer brushes for hollow carbon nanosphere arrays. Macromol. Rapid Commun. 37, 1507–1512. Kondyurin, A., Gan, B.K., Bilek, M.M.M., McKenzie, D.R., Mizuno, K., Wuhrer, R., 2008. Argon plasma immersion ion implantation of polystyrene films. Nucl. Instrum. Methods Phys. Res. Sect. B Beam Interact. Mater. Atoms 266, 1074–1084. Lee, B.M., Jung, J.M., Hwang, I.T., Shin, J., Hong, S.K., Jung, C.H., Jeong, Y.G., Choi, J.H., 2018. Fabrication and electric heating behavior of carbon thin films from waters-soluble poly(vinyl alcohol) via simple dry and ambient stabilization and carbonization. Appl. Surf. Sci. 456, 561–567. Lee, H.S., Baek, G.Y., Hwang, I.T., Jung, C.H., Choi, J.H., 2017. Preparation of porous carbon films from polyacrylonitrile by proton beam irradiation and carbonization. Radiat. Phys. Chem. 141, 369–374. McGettrick, J.D., Speller, E., Li, Z., Tsoi, W.C., Durrant, J.R., Watson, T., 2017. Use of gas cluster ion source depth profiling to study the oxidation of fullerene thin films by XPS. Org. Electron. 49, 85–93. Ramakrishnan, P., Baek, S.H., Park, Y., Kim, J.H., 2017. Nitrogen and sulfur co-doped metal monochalcogen encapsulated honeycomb like carbon nanostructure as a high performance lithium ion battery anode material. Carbon 115, 249–260. Sheng, L., Jiang, L., Wei, T., Liu, Z., Fan, Z., 2017. Spatial charge storage within honeycomb-carbon frameworks for ultrafast supercapacitors with high energy and power densities. Adv. Energy Mater. 7, 1700668. Song, X., Dai, Z., Xiao, X., Li, W., Zheng, X., Shang, X., Zhang, X., Cai, G., Wu, W., Meng, F., Jiang, C., 2015. formation of carbonized polystyrene sphere/hemisphere shell arrays by ion beam irradiation and subsequent annealing or chloroform treatment. Sci. Rep. 5, 17529. Tian, W., Zhang, H., Sun, H., Suvorova, A., Saunders, M., Tade, M., Wang, S., 2016. Heteroatom (N or N-S)-Doping induced layered and honeycomb microstructures of porous carbons for CO2 capture and energy applications. Adv. Funct. Mater. 26, 8651–8661.
Acknowledgements This research was supported by a grant from the National Research Foundation (NRF) of Korea funded by the Korean government (MSIT; NRF- 2017R1A4A1015360). Appendix A. Supplementary data Supplementary data to this article can be found online at https:// doi.org/10.1016/j.radphyschem.2019.05.006. References Bui, V.T., Lee, H.S., Choi, J.H., Choi, H.S., 2015. Highly ordered and robust honeycomb films with tunable pore sizes fabricated via UV crosslinking after applying improved phase separation. Polymer 74, 46–53. Bui, V.T., Thuy, L.T., Tran, Q.C., Nguyen, V.T., Dao, V.D., Choi, J.S., Choi, H.S., 2017. Ordered honeycomb biocompatible polymer films via a one-step solution-immersion phase separation used as a scaffold for cell cultures. Chem. Eng. J. 320, 561–569. Cha, S.M., Nagaraju, G., Sekhar, S.C., Bharat, L.K., Yu, J.S., 2018. Fallen leaves derived honeycomb-like porous carbon as a metal-free and low-cost counter electrode for dye-sensitized solar cells with excellent tri-iodide reduction. J. Colloid Interface Sci. 513, 843–851.
21