Vol.9 No.3 2017

Research paper : A super-growth method for single-walled carbon nanotube synthesis (K. Hata)−171−Synthesiology - English edition Vol.9 No.3 (2017) There were mountains of difculties and issues in realizing the mass production of single-walled CNTs by the super-growth method, but I was looking only at the possibilities of the super-growth method, not the difculties.3.1.2 Development of mass production technology in the NEDO “Carbon Nanotube Capacitor Development Project”Fortunately, AIST obtained an opportunity to develop a mass production process by the super-growth method jointly with Zeon Corporation, in the “Carbon Nanotube Capacitor Development Project (FY 2000~2010),” a nanotechnology program of the New Energy and Industrial Technology Development Organization (NEDO) from 2006 (Fig. 7). It is presently known as a prime example of a successful national project, but it was fraught with hardship in the beginning.First, one of the absolute conditions in starting the project was to nd a partner company with whom we would develop the mass production technology by the super-growth method. Mr. Motoo Yumura who was my superior at the time contacted eight companies that were engaging in CNT R&D and interviewed some of the companies. All companies said, “The super-growth method is wonderful. But we have been conducting R&D for CNTs using our original technology. It is difcult to abandon this technology and switch over to the super-growth method.” We were unable to meet a partner that would truly work on the mass production process by the super-growth method. Through an introduction, we met Mr. Kohei Arakawa who was the managing director of the Zeon Corporation.Mr. Arakawa had experience in CNT research (at the time, it was called simply carbon, not CNT) when he was working at Nikkiso Co., Ltd. He listened to our story with zeal and keenness. He immediately calculated the cost of mass production, determined that it would be viable as business, and obtained permission from the president to go forward on the R&D. I intuitively felt that super-growth would not be realized unless we teamed up with Mr. Arakawa.Immediately afterward, the asbestos issue arose. In June 2005, it was reported that workers and families of two companies that were manufacturing asbestos died of malignant mesothelioma. Since CNT had a similar form as asbestos, there was concern that it might cause a similar health problem, and we were ooded with inquiries every day. The permission of CNT R&D was withdrawn, and it seemed we could no longer work with Mr. Arakawa. However, we did not give up. First, Mr. Arakawa asked us to evaluate the amount of CNTs that adhered to the HEPA lter in the laboratory. As a result, it was found that the concentration of CNTs floating in the air in the lab environment was lower than the concentration of asbestos in regular air. Mr. Arakawa directly requested the president for CNT R&D one day before the deadline for application to the NEDO Project, and obtained the president’s permission for R&D.While it felt like treading on thin ice, we were able to start the project with wonderful members who worked hard to realize the single-walled CNTs by the super-growth method.4 Research scenario for achieving the goalWhen the project started, we extracted the technical issues that had to be tackled. The main technical issues listed were as follows: the development of a substrate that was low cost and could be easily upscaled to a large surface area, to replace the silicon wafer; the development of a coating type catalyst to replace the iron thin film catalyst formed by the sputtering method; the development of synthesis technology for synthesizing uniform, vertical arrays by controlling and adding water to a large surface area at PPM level; the development of continuous synthesis technology to continuously transport the substrate material; and others (Fig. 8). Diverse technical issues also included the development of a metal synthesis furnace to replace the quartz furnace, cleaning technology of the furnace, reuse technology of the substrate material, generation of a low-cost gas atmosphere, and others.Since it was necessary to solve all the issues in five years, we took an approach that we named the “black box strategy.” First, we weighed all issues. The issues with absolutely no solution were labeled “black,” the issues that could be solved with abundant human and monetary resources were “grey,” and the issues that had been solved were “white.” Next, the limited research resources were prioritized to turn the black issues grey. Also, to complete the whole picture in a short time, individual elemental technologies were developed concurrently as much as possible, and the elemental technologies were integrated later to complete Fig. 7 Organization of Carbon Nanotube Capacitor ProjectCapacitor Group: Kenji TamamitsuMass Production Group: Mitsugu UeshimaLeaders: Sumio Iijima, Kohei ArakawaFocused researchVertical collaboration• Industrial mass productionResearch Center for Advanced Carbon Materials, AISTResearch Institute of Energy, AISTNippon Chemi-ConZeonDevelop mass production technologyDevelop fundamental technologyDevelop super capacitor• User

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