| Summary: | 博士 === 國立臺灣科技大學 === 化學工程系 === 99 === A system for the measurement of surface tension of melting glasses is developed in this work. The methods used are the sessile and pendant drop tensiometry. The accuracy of tension measurement is compared and discussed at the end of this thesis.
An apparatus for measuring the surface tension of molten glass, B2O3, and Ag at temperature ranging between 500 and 1600 oC was built first. A program for acquiring drop images continuously and locating the edge coordinates is then developed. After that, this tensiometer using the sessile / pendant drop method is used for the study of the dependency of surface tension on temperature. There are three main parts in this thesis: (i) surface tension of molten glass measured by pendant / sessile drop method and we discussed the accuracy of tension measurement by using pendant / sessile drop. Then, we defined a shape factor (Fc), and we discussed about the measurement uncertainty with shape completeness. (ii) Surface tension measurement of molten B2O3 was investigated by pendant drop method and we tried to understand why the surface tension of molten B2O3 vary with temperature in abnormal tendency. (iii) Surface tension of molten Ag was measuerd through sessile drop method and we discuss its surface tension and contact angle on graphite and refractory.
Finally, we examined the results from these three parts. Firstly, the error of surface tension measurement by using the pendant drop method is around 3 mN/m; while the measurement error via the sessile drop method is around 9 – 20 mN/m. The latter is dependent upon the drop contact angle of the sessile drop. Secondly, we find that a complete drop would yield a more accurate result of tension measurement than a fragmented droplet. Thirdly, the surface tension of molten B2O3 inceases with rising temperature. Finally, we find that the contact angle of molten Ag on graphite would change from 140o to 156o with temperature from 1150 to 1175 oC.
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