1991 Fiscal Year Final Research Report Summary
Practical CO_2-Laser Separation of Silicon Isotopes
| Project/Area Number |
01850183
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| Research Category |
Grant-in-Aid for Developmental Scientific Research
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| Allocation Type | Single-year Grants |
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| Research Field |
工業物理化学
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| Research Institution | Kyoto Institute of Technology |
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Principal Investigator |
ARAI Shigeyoshi Kyoto Institute of Technology, Chemistry and Materials Technology, Professor, 工芸学部, 教授 (10087538)
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| Co-Investigator(Kenkyū-buntansha) |
KOBAYASHI Kuniaki Leonix Co., Managing Director, 常務取締役
SUZUKI Toshio Nisshin Bouseki Co., Laboratory for Research and Development, Director, 取締役研究所長
ISHIKAWA Yo-ichi Kyoto Institute of Technology, Chemistry and Materials Technology, Assistant Pro, 工芸学部, 助教授 (00167248)
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| Project Period (FY) |
1989 – 1991
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| Keywords | Laser Isotope Separation / Photon Decomposition / Silicon Isotopes / Hexafluorodisilane / Infrared Photochemistry |
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| Research Abstract |
Naturally occurring silicon consists of three stable isotopes : 92.23% of ^<28>Si, 4.67% of ^<29>Si, and 3.10% of ^<30>Si. The infrared multiple-photon decomposition (IRMPD) of hexafluotodisilane (Si_2F_6) is highly isotopically selective under favorable experimental condisions. The products are gaseous SiF_4 and white powders. Larg-scale silicon isotope separation based on the IRMPD of natual Si_2F_6 has been carried out using a commercially avalable high-power CO_2 TEA laser and a flow system. The irradiation vessel had a length of 4 m and a total volume of 13.7 liters. The lase beam was mildly focussed into the vessel by a BaF_2 lens with a focal length of 3 m. The entrance window was blown with an argon gas stream in order to provent deposition of white powders on it. Partial pressures of Si_2F_6 renged from 2 to 4 Torr. The product SiF_4 and unreacted Si_2F_6 condensed into the trap cooled with liquid nitrigen and separated from each other by low-temperature distillation. SiF_4 with a ^<30>Si-atom fraction of 33% was obtained at a production rate of 0.014 mol h^<-1>, where 2.3-Torr Si_2F_6 was irradiated with 5-6-J laser pulses at 951.19 cm^<-1>. The pulse repetiotion was 10 Hz. SiF_4 containing 12% of ^<20>Si was obtained under a slightly different condtion, i. e., at 954.55 cm^<-1> ; the production rate was 0.018 mol h@^<-1>. When 39 % of initial Si_2F_6 was decomposed in the laser irradiation at 954.55 cm^<-1>, that is, the flow rate inside the vessel is slow, residual Si_2F_6 showed a ^<28>Si-atom fraction of 99.7%. Teh production rate of the Si_2F_6 was 0.042 mol h^<-1>. The deposition of white powder was troublesome to the flow apparatus. Howser, the addition of HI to Si_2F_6 was found significantly to reduce the formation of white powders. These results show that the present laser separation of silicon isotopes is satisfactrily practicable.
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