New Method for Determining the Nucleation and Crystal‐Growth Rates in Glasses

Abstract

The rates for nucleation (I) and crystal growth (U) for a lithium disilicate (Li 2 O⅐2SiO 2 , LS 2 ) glass were determined, as a function of temperature, using a new differential thermal analysis (DTA) technique. This technique requires in situ nucleation and crystal-growth heat treatment of a small amount of powdered sample inside the DTA apparatus, which then are followed by a DTA scan at a constant heating rate. The I and U values that have been determined at selected temperatures for the LS 2 glass are in excellent agreement with those reported in the literature. The technique also has been used to determine the concentration of quenched-in nuclei in LS 2 glasses prepared from melts that have been quenched at different rates, which are in reasonable agreement with those estimated from theoretical considerations. This new DTA technique is less tedious, requires a smaller amount of sample, and is at least 10 times faster than the conventional methods that have been used to measure I and U. Also, no special sample preparation, other than simply grinding and screening the glass to a particle size that is suitable for use, is required in this technique, whereas grinding, polishing, or etching is required in conventional methods. The excellent agreement in the I or U values that have been determined for the LS 2 glass via the present and conventional methods demonstrates the accuracy, validity, and usefulness of this DTA method for rapid determination of the nucleation and crystal-growth rates in glasses.

General Approach to the Nucleation and Crystal Growth in Sb0.5Se99.5 Glass Explaining the Shape of DSC Curves

“…Finally, the general expression of conversion given by equation (9) can be calculated for surface crystallization including Equations (5,7,10) and giving the form:…”

“…Appropriate prediction of crystallization process allows controlling and optimizing of conditions for new high-tech material production. Crystallization behavior can be studied directly by observing of crystals growing in material under specific conditions 4,6 or indirectly by monitoring specific properties of studied material 3,[7][8][9] . The direct observation of crystal growth is very time consuming, thus the indirect methods are preferred.…”

Study of nucleation in a Se90Te10 chalcogenide glass by microscopy and differential scanning calorimetry

“…By approximating crystalline fraction, a, of glass after nucleation-growth heat treatments, Ray et al proposed a method for the determination of nucleation rates quantitatively; they obtained [18,19] …”

“…More recently, nuclei densities were estimated by calorimetry studies of glass samples subjected to double heat treatments similar to that of Tammann method, and such measurements were found to be comparable to conventional micrography methods [18,19,23]. DSC/DTA analysis thus offers simplicity and the ability to rapidly obtain nucleation data.…”

“…When large numbers of nuclei are present, image analysis (IA) techniques can be used for automated estimation of nuclei in batches of micrographs. For nucleation measurements in glasses, an alternative to the often tedious direct method is the indirect determination using calorimetry [18][19][20].…”