Glasses with Fictive Temperature-Independent Properties

Rensselaer Polytechnic Institute, Troy NY

Investigators

Abstract

NON-TECHNICAL DESCRIPTION: In general, properties of a glass vary depending upon how fast it was cooled from its melt. There are two different types of glasses: normal glass and anomalous glass and they exhibit the opposite cooling rate dependences of properties. Thus, between these two types of glasses with opposite trends, there should be some special glasses whose properties do not change with cooling rate. These glasses are expected to be useful in many applications. For example, a flat panel display screen made of such glasses would not change its volume during the heat-treatment and electrodes can be placed at precise positions, leading to clearer images on the screen. When a glass is scratched with a hard object, a portion of the glass appears to change its structure and properties, which can lead to easy cracking. The special glass to be investigated in this research appears not to change its properties during scratching and is consequently less likely to crack. One graduate student and two undergraduate students will be trained in this program. At least one of the three students will be female. TECHNICAL DETAILS: Glass prepared under different cooling rates is defined in terms of its fictive temperature, i.e., the temperature at which the liquid freezes into the glassy state. Glasses with fictive temperature-independent properties are expected to exhibit unique characteristics useful in practical application such as non-compaction during liquid crystal display glass processing. Diamond indentation is often used to characterize mechanical properties of glasses, but what is happening during indentation is not clear. It appears that fictive temperature of a glass increases during indentation and the fictive temperature dependence of glass properties plays an important role in mechanical behavior under indentation. Thus, this study of the proposed glasses is expected to lead to the development of glasses with unique properties and clarify what is occurring during indentation in glasses and other brittle materials.