課題番号 ：S-16-ShH-0008・0023
利用形態 ：共同研究型
利用課題名（日本語） ：ナノカーボンマテリアルの構造制御と物性評価
Program Title (English) ：Structure control &property evaluation of nanocarbon materials
利用者名（日本語） ：緒方　啓典
Username (English) ：H. Ogata
所属名（日本語） ：法政大学
Affiliation (English) ：Hosei University

１．概要（Summary ）
Spherical carbons have attracted extensive interest in many fields, such as lithium ion batteries (LIBs), supercapacitors, catalyst supports, gas adsorption because they possess some unique chemical and physical properties, which strongly depend on their size, microstructure, and crystallinity. Here, we have investigated the effects of high temperature annealing on the carbon spheres (CSs), which were synthesized from the hydrothermal carbonization of glucose, in an Ar atmosphere. The morphology, microstructure, and crystallinity of the hydrothermal CSs before and after high temperature treatment (HTT) process were carried out using scanning and transmission electron microscopes, BET surface area analysis, and Raman spectroscopy, respectively. Their electrical properties under compression were also discussed in this work.
２．実験（Experimental）
The CSs were obtained by hydrothermal method, which is similar to Li’s process. In brief, glucose was dissolved in water to form a clear solution, then was put into a 30 ml Teflon-sealed autoclave and maintained at 180 oC for 2h. A brown product was isolated by centrifugation, and was cleaned by three cycles of centrifugation, washing, redispersion in water and in alcohol, and then was dried at 80 oC in a vacuum oven for more than 8h. Subsequently, the dried powder was heated at 900 oC for 1h. The resulting product was named as “synthesized CSs”.
Heat treatment of the synthesized CSs was carried out at 1200, 1800, 2100, 2500 and 2900 oC for 30 min (from room temperature to 2000 oC with 20 oC/min, above 2000 oC to target temperature with 5 oC/min), using a graphite-resistance furnace operating in a high-purity Ar atmosphere at 1 atm. These heat-treated CSs were referred to as CS@1200oC, CS@1800oC, CS@2100oC, CS@2500oC, and CS@2900oC, respectively.
The morphology and microstructure measurements were performed using a Hitachi SU-8000 field emission scanning electron microscope operated (SEM) at 15 kV and a JEOL JEM-2100F transmission electron microscope (TEM) operated at 200 kV, respectively. The crystalline structure was characterized by a RENISHAW inVia Raman spectroscope using the laser with a wavelength of 532 nm. The chemical composition was carried out by energy dispersive X-ray spectroscopy (EDX), which was attached in SU-8000. The BET surface area was examined by ASAP 2020 Physisorption Analyzer.
３．結果と考察（Results and Discussion）
The CSs with 60-250 nm in diameter can be obtained from aqueous glucose solution by hypothermal carbonization, and were treated at the high temperatures of 900-2900 oC in Ar atmosphere. All CSs have high purity, and their morphology, microstructure and porosity strongly depend on the treatment temperatures. These results are supported by EDX, SEM, TEM, Raman and BET surface area analyses. We also measured and compared the electrical properties of the treated CSs under compression, and found that the resistivity of the carbon particles is very dependent on their morphology, microstructure and density. Thus, the hydrothermal CSs provide another choice as electrode in the applications of energy-related devices by tailoring the structure and morphology using HTT
４．その他・特記事項（Others）
Dr. Zhipeng Wang provided helps for this work.
５． 論文・学会発表（Publication/Presentation）
(1) Z. Wang, H. Ogata, G.J.H. Melvin, S. Morimoto, J. Ortiz-Medina, R. Cruz-Silva, M. Fujishige, K. Takeuchi, H. Muramatsu, T. Hayashi, M. Terrones, Y. Hashimoto, M. Endo, “A fast, low-temperature growth of vertical graphene solid waste plastics and their electrochemical properties”, The World Conference on Carbon: Common fundamentals, remarkably versatile applications (Carbon 2016), The Penn Stater Conference Center Hotel, State College, Pennsylvania, USA. 平成28年7月13日.
(2) Z. Wang, H. Ogata, G.J.H. Melvin, M. Obata, S. Morimoto, J. Oritz-Medina, R. Cruz-Silva, M. Fujishige, K. Takeuchi, H. Muramatsu, T. Hayashi, M. Terrones, Y. Hashimoto, and M. Endo, “Structural evolution of hydrothermal carbon spheres induced by high temperatures and their electrical properties under compression”, The 77th Autumn Meeting, Toki Messe, Niigata, Japan.　応用物理学会第77秋季学術講演会, 平成28年9月15日.
(3) Z. Wang, H. Ogata, G.J.H. Melvin, S. Morimoto, J. Oritz-Medina, A. Laura-Elias, M. Fujishige, K. Takeuchi, H. Muramatsu, T. Hayashi, M. Terrones, Y. Hashimoto, M. Endo, “High temperature induced carbon-related nanomaterials from rice husk: synthesis and characterization”, International Symposium on Carbon Nanotube in Commemoration of Its Quarter-Century Anniversary (2016-CNT25),Tokyo Institute of Technology, Tokyo, Japan. 平成28年11月17日.
６．関連特許（Patent）
なし。