1995 Fiscal Year Final Research Report Summary
Probation of Microcrystal Liduid Model and Application to Glass-ceramics Fabrication
| Project/Area Number |
06453123
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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
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| Research Institution | Kyoto Institute of Technology |
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Principal Investigator |
OTA Rikuo Kyoto Institute of Technology, Dept. Chem. & Mat. Tech., Professor, 工芸学部, 教授 (30026124)
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| Co-Investigator(Kenkyū-buntansha) |
FUKUNAGA Jiro Kyoto Institute of Technology, Dept. Chem. & Mat. Tech., Lecturer, 工芸学部, 講師 (80027797)
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| Project Period (FY) |
1994 – 1995
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| Keywords | glass melt / lithium silicate glass / crystallization / DTA / crystallization temperature / Crystal niclei / surface nucleation / microcrystal liquid model |
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| Research Abstract |
The microcrystal liquid model was probed for the lithium silicate melts. It was confirmed that number density of microcrystals and crystal size decreased withh increasing melting (holding) temperature. Results are as follows.
(1) Melts of 33Li_2O・67SiO_2 (in mol%) composition were held at 1035-1200ﾟC for 1-2hrs. Quenched glasses were heat-treated at 600-650ﾟC for 20-45 min. Number density N and crystal size of microcrystals were found to decrease as holding temperature rose. DTA measurements were conducted to determine crystallization temperature Tc on glass specimen having varied thermal history. It was observed that Tc increases as the holding temperature rises.
(2) Variation of number density N was investigated on phase-separating glass of 31Li_2O・69SiO_2 composition. Similar results as mentioned above were obtained. It was implied that microcrystals are present in melts of phase-separating composition.
(3) Lithium rich glass of 35Li2O・35SiO2 composition was investigated for number density and crystal size of crystals after varied holding temperatures. It was learned that N decreases and crystal size decreases with increasing melting temperature. The number density of microcrystals was in the decreasing order when compared at the same holding temparture ; 31Li_2O・69SiO_2>33Li_2O・67SiO_2>35Li_2O・65SiO_2.
(4) 33Na_2O・65SiO_2 glass was studied for this model. Surface nucleation took place preferentially in this glass. Crystal size and amount of crystals develloped by heat-treatment were affected by the holding temperature. It was suggested that some sort of microcrystals are existent in the molten state depend-ing on the melting history.
(5) It was concluded that first step of crystallization can be anticipated from the microcrystal liquid model of melt and this concept could help us to design glass-ceramics of desired number density and desired crystal size.
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