Current issues on glass crystalization

• Grant number: 99/00871-2
• Support Opportunities: Research Projects - Thematic Grants
• Start date: September 01, 1999
• End date: October 31, 2004
• Field of knowledge: Engineering - Materials and Metallurgical Engineering - Nonmetallic Materials
• Principal Investigator: Edgar Dutra Zanotto
• Grantee: Edgar Dutra Zanotto
• Host Institution: Centro de Ciências Exatas e de Tecnologia (CCET). Universidade Federal de São Carlos (UFSCAR). São Carlos , SP, Brazil
• Associated research grant(s): 03/03575-2 - Vladimir Mikhailovich Fokin | Russian Academy of Sciencies - Rússia, AV.EXT; 01/03167-6 - Vladimir Fokin | institute of silicate chemistry of Russian - Russia, AV.EXT; 00/11078-0 - Issak Avramov | Institute of Physical Chemistry - Bulgária, AV.EXT

Abstract

The general objective of this research is to study in detail and to contribute to the solution of several important problems regarding the mechanisms and kinetics of crystal nucleation and growth in glasses. Therefore, crystallization is the focused theme. The main, specific, objectives of this project are: 1. to study the competition between sintering and simultaneous crystallization of powdered glasses, from both theoretical and experimental points of view, and to define the conditions that favor each phenomenon; 2. to examine the possible nucleation of metastable phases (MP) in the initial stages of crystallization in glasses and, in case some MP is found,to determine the favorable conditions and the important variables (thermal history, sludges, etc.) that control this phenomenon; 3. to determine the possible dependence of the nucleus-liquid surface energy with nuclei size and temperature, as well as its influence in the kinetics of crystal nucleation; 4. to study other related phenomena, such as: the possible relationships among the temperature of maximum nucleation, Tmax, the magnitude of the maximum, Imax, and the temperature of glass transition, the effect of water (OH-) in the crystallization, etc. The three first objectives refer to current problems. The integration among them is assured by the focus of the work (crystallization) and by the fact that similar vitreous oxides will be studied, seeking to solve the three problems. However, we would not like to restrict this proposal solely to those three ideas, but also to have freedom to study related subjects, witha certain dynamics (that will depend on the flow of new ideas and of the readness of students and visitors). The theme crystallization is maintained in all sub-projects. Therefore, there is perfect coherence of objectives, of the important theories, of the experimental techniques and of the materials to be used. (AU)