High Temperature Dynamic In-Situ Raman Spectral Characterization of Sodium Borosilicate Glasses
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AJIT JILLAVENKATESA AND ROBERT A. CONDRATE, Sr. Institute of Glass Science and Engineering, NYS College of Ceramics, Alfred University, Alfred, NY 14802
ABSTRACT Dynamic Ranan spectra of sodium borosilicate glasses containing large amounts of boron oxide have been studied as functions of temperature and holding time. Such characterization enabled measuring the changes in the nature and states of the molecular species that were present in the glasses and their melts. The data indicate that boroxol rings involving one or more four-coordinated boron ions in the sodium oxide-containing glasses decreased in concentration as they were heated through melt temperatures as was noted earlier for boroxol groups involving three-coordinated boron ions in pure borosilicate compositions.
INTRODUCTION Structural changes can be noted in the boron oxide portion of the network of boron oxide-containing glasses and melts with changing temperature. Related glass structural investigations with temperature change have been conducted using Raman spectroscopy for glasses containing no alkali oxide additions. For instance, Walrafen et al. [1] have studied the high-temperature structural changes in vitreous boron oxide by Raman spectroscopy. While Furukawa and White [2] investigated high-temperature Raman spectra of B 2 03 glasses that contained higher concentrations of boron oxide, Chakraborty and Condrate (3,4] have studied such spectra for both B 2 0 3 -GeO2 and B 2 0 3 -GeO 2-SiO
2
glasses that contained large amonts of boron oxide. For all of these studies, the spectral data dearly indicated that structural changes occured in the borate portion of the glass networks as one approached and passed through their melt temperatures. The major structural change for each of the investigated glasses involved the breakdown of the boroxol rings possesing only three-coordinated boron ions into either borate chains or isolated borate ( B0 3 ) groups. This current study will extend such spectral/structural investigations to glass compostions which possess boroxol rings containing one or more four-coordinated boron ions.
The study will look at the Raman spectra of sodium
borosilicate glasses containing large amounts of boron oxide at high temperatures. 33 Mat Res. Soc. Symp. Proc. Vol. 321. 01994 Materials Research Society
EXPERIMENTAL PROCEDURES
Preparation of Glasses Ten gram batches of the glass samples containing various compositions were prepared from reagent grade Na 2 CO3, H 3 BO 3 and SiQ 2 . These batches were weighed out and The glasses were melted for eight hours in
melted in a covered platinum crucible.
a SiC globar furnace at temperatures varying from 800 to 1400°C, depending upon glass compostion. The resulting melts were poured into graphite molds to form 10x50 Each glass sample was then annealed at 10'C above its glass transition temperature for 30 minutes. Flat glass specimes of dimensions 5x7x4 mm were cut from the rods. Table 1 lists the different glass compositions studied. mm rods.
Wet chemical analysis of the glass sa
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