CHEMICAL ANALYSIS AND PHYSICAL PROPERTY EVALUATION OF LITHIUM BORO-SILICATE GLASS

Glass is an amorphous non-crystalline substance that displays a glass transition near its melting point. Most of the glasses we encounter are borosilicate glasses. The starting materials commonly used for making such types of glasses are quartz, boric acid, alumina and different carbonates. Accurate and rapid glass analysis is a critical factor in resolving batch upset, meeting composition requirements, evaluating compositional changes or meeting customer requirements.

For the present study, a simultaneous ICP-OES, Optima 7000 DV was used for chemical analysis (except silica which was analyzed by wet chemical method) and a DTA/DSC analyzer was used for determining the glass transition and crystallization temperature of an alkali borosilicate glass.

The glass sample was further crushed into fine powder (size: 100 mesh) for digestion. For silica, the sample was fused with sodium peroxide, extracted with dilute acid followed by perchloric acid fuming. Silica was then estimated by gravimetric analysis through hydrofluorization. For the rest of the parameters, the sample was digested using hydrochloric acid, nitric acid, hydrofluoric acid and hydrogen peroxide in a microwave digester at 800 W and 30 psi pressure for 45 minutes. The dual view window of the ICP was used for the analysis under the following operating conditions.

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The program analyzed 12 elements in the sample glass and 9 elements in the CRM glass sample in less than 5 minutes. The calibration curve was made using two standards 5 and 10 mg/L considering reagent blank as 0 mg/L. Thus, the accuracy achieved is within the range of ± 0.20 % for the elements analyzed in ICP and ± 0.25 % for silica analyzed by wet chemical method. Results are as follows in wt%.

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Apart from the above chemical analysis, physical parameters such as glass transition temperature (Tg) and crystallization temperature (Tc) were also determined from the DTA/TGA analyzer, Perkin Elmer STA 6000. As per the definition of glass, an amorphous solid that exhibits a glass transition is termed as glass. The temperature at which an amorphous material undergoes a reversible transition from a hard and relatively brittle state into a rubbery state is known as the glass transition temperature (Tg). On the other hand, crystallization temperature (Tc) is that temperature at which crystals precipitate from a melt of glass when it is cooled slowly. Both these temperature could be identified during DSC scan for the sample glass frit and the STD glass as shown below: 

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The work is produced by: Dr. Saswati Ghosh under guidance of Prof.  Barun Gupta at MSK Central Laboratory Kolkata.
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