1998 Fiscal Year Final Research Report Summary
Habit Change and Growth Mechanism of NaBrO_3 and NaClO_3
| Project/Area Number |
08640612
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Petrology/Mineralogy/Science of ore deposit
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| Research Institution | University of Tokushima |
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Principal Investigator |
INOUE Tetsuo Univ.of Tokushima, Faculty of Engineering, Professor, 工学部, 教授 (60005923)
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| Co-Investigator(Kenkyū-buntansha) |
NISHOKA Kazumi Univ.of Tokushima, Faculty of Engineering, Professor, 工学部, 教授 (90035650)
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| Project Period (FY) |
1996 – 1998
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| Keywords | Sodium bromate / crystal habit / aqueous solution / in-situ observation |
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| Research Abstract |
The effects of impurities, (1)acetic acid, 1.15 mol% and (2) sodium acetate (anhydrous), 1.0 mol%, upon the habit changes of NaBrO_3 crystals have been investigated. The crystals were grown from aqueous solution under the following conditions ; (i) supersaturations : ln(C/Ce)=0 - 0.4, (Ce : equilibrium mole fraction), (ii)growth temperatures : 20-64ﾟC.The results of habit changes were shown in a plot of growth temperature against supersaturation (such a plot is called a morphodrome). It was found that the impurity effects on the habit changes were more important in the low supersaturation range than in the high supersaturation range. The process of crystal growth was observed in-situ under an optical microscope. A heating stage was set on the microscope stage. The heating stage was composed of the heating and cooling unit using Peltier element. The results were summarized as follows.
(1) (1) The domain of {100} (cubic habit) is located at the higher temperature region as compared to {111}(tetrahedral habit) for wide range of supersaturations for both pure and doped solutions.
(2) The acetic acid doping raised the transition temperature for the change from {111} (tetrahedral habit) to {100} (cubic habit), but the sodium acetate doping decreased the temperature in comparison with the pure case for the low supersaturation range.
(3) The transition temperature from {111} (tetrahedral habit) to {100}(cubic habit) decreased with increasing of supersaturation in all cases.
(4) The domain of intermediate shape in the case of sodium acetate doping was larger than the other cases.
(5) It was considered that the doping of acetic acid decreased the growth rates of {111}, whereas the doping of sodium acetate decreased the growth rates of {100}.
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