1991 Fiscal Year Final Research Report Summary
Study on the enlargement of glass-forming regions by the sol-gel method
| Project/Area Number |
02453067
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| Research Category |
Grant-in-Aid for General Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Research Field |
無機工業化学・無機材料工学
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| Research Institution | Kyoto Institute of Technolygy |
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Principal Investigator |
OTA Rikuo Kyoto Institute of Technology, Professor, 工芸学部, 教授 (30026124)
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| Co-Investigator(Kenkyū-buntansha) |
FUKUNAGA Jiro Kyoto Institute of Technology, Lecturer, 工芸学部, 講師 (80027797)
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| Project Period (FY) |
1990 – 1991
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| Keywords | Gel region / Glass-forming region / Thermal Stability / Crystallization temperature / Critical cooling rate / Sol-gel method / B_2O_3-Na_2O system / SiO_<>-Na_2O system |
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| Research Abstract |
Glasses are obtained via sol-gel process. Glass-forming ability of a system is regarded as closely related with the gelation ability, which is reflected in its thermal stability. In the present study basic systems such as B_2O_3-Na_2O, B_2O_3Na_2O-Al_2O_3 (TiO_2) and SiO_2-Na_2O systems were chosen to study gel regions, thermal stability and glass-forming ability. First, variations of gel regions were investigated with the addition of water or catalysts (hydrochloric acid or ammonium). Gel regions were at B_2O_3 <100 mol% and>60 mol% in the B_2O_3-Na_2O system. Gel regions emerged in Al_2O_3 rich compositions in the B_2O_3-Na_2O-Al_2O_3 sys- tem, and gel region was at SiO_2=60-100 mol% in the SiO_2-Na_2O system. Little effect was observed with water of ammonium addition, but with HCl addition crystals precipitated in most compositions except SiO_2=100 mol% composition. Gelation time was reduced with the addition of water or NH_4OH. DTA measurements were conducted on gels with a heating rate 5ﾟC/min to determine the crystallization temperature Tc. Liquidus temperature Tl was determined by DTA method or by direct observation with a hot-stage microscope. Tc/Tl ratio was assumed to represent the thermal stability of a gel or a glass. In the Tc/Tl-composition curvea maximum and a minimum were observed at B_2O_3= 70 and 80 mol%, respectively, in the B_2O_3-Na_2O system. Similar Tc/Tl dependency was identified for melt-quenched glasses. It was proved that Tc/Tl ratio indicates the gelation ability or the glass-forming ability of a system. Tc/Tl - Q* (critical cooling rate for glass formation) relationship was established among the experimental data. Computer simulations were made to confirm this relationship.
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