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| March 4, 1999 No.0878 | ||
| MHI DEVELOPS WORLD'S FIRST TECHNOLOGY TO PRODUCE SUPERIOR-GRADE GRAPHITE BY MICROWAVES |
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| Achieved temperature mark of 3,200°C | ||||||
| Tokyo, March 4, 1999 -- Mitsubishi Heavy Industries, Ltd. (MHI) has developed the world first technology in producing graphite from carbon powder by using microwaves, which was conventionally considered impossible. Graphite is commonly used for crucibles and battery's electrolytic anodes, as well as lubricants, paint and glitters. Graphite is also used for the anodes of lithium-ion batteries, with increasing applications in mobile phones, lap-top computers and other mobile devices. | ||||||
In the same process, MHI has also achieved a heating temperature of 3,200°C . High heating temperature is an essential factor in enhancing the products' quality and enables the production of a superior grade of graphite. This very high temperature with microwave heating is also a world first achievement, producing the highest grade graphite at a laboratory level. MHI's technology will enable the development of next generation graphite production processes with various features enabling improvement in the work environment and a transition from batch production to continuous production. MHI has applied for the patents of this new production system based on this technology in Japan. Based on its experience of using microwaves in heating carbon, MHI has challenged microwave heating of carbon powder, which is generally assumed to be very difficult, and succeeded in finding an appropriate heating method through persistent R&D. The graphitization of carbon powder using microwaves has not been realized previously because of difficulty in heating of carbon powder due to its high electric conductivity and reflection of microwaves. In achieving a final goal of a 3,200°C mark temperature, which enables baking of the highest-grade graphite, MHI first staged a targeted temperature of 2,500°C , and then stepped up to 2,900°C and subsequently 3,200°C . High temperature heating aligns carbon's intricate molecular structure and enables the production of high-grade graphite, which is a key to enhance a battery's capacity and charge/discharge efficiency, a decisive factor for battery capability. According to the research conducted by MHI to present, the higher the temperature rises, as heated by microwave, the more the graphitization of the material advances. MHI has verified that the distance between graphite layers becomes 0.336 nanometers at above 3,000°C , resulting in higher graphite quality. At present, graphite is being produced by a graphitizing furnace which uses a batch production system. However, the production work environment using this method tends to be poor due to the heat and carbon dust generated in the process of filling carbon powder into heating vessels, removing vessels from furnace and extracting products from vessels. At the same time, batch production requires several days from the start of heating of carbon powder to product extraction via the cooling process. Therefore, the improvement of the work environment and the enhancement of efficiency through continuous production have been a major issue in producing graphite, in addition to graphite quality. The demand for rechargeable batteries such as the lithium-ion battery is rapidly increasing for the use of various electronic devices. According to a statistic published by the Ministry of International Trade and Industry, the shipment of lithium-ion batteries in Japan in 1997 has jumped to approximately 209.7 billion yen, from 40.3 billion yen in 1995 and 150.6 billion yen in 1996. Furthermore, demand for efficient batteries is expected to skyrocket with electric cars becoming popular, as will the demand for electrolytic anodes. The research and development of this system has been jointly conducted by MHI's Kobe Shipyard & Machinery Works, Takasago Research & Development Center and Hiroshima Research & Development Center. |
