Effect of chemical composition on the viscosity shift factor

• Grant number: 25/26431-5
• Support Opportunities: Scholarships in Brazil - Scientific Initiation
• Start date: January 01, 2026
• End date: December 31, 2026
• Field of knowledge: Engineering - Materials and Metallurgical Engineering - Nonmetallic Materials
• Principal Investigator: Ricardo Felipe Lancelotti
• Grantee: Pedro Henrique Moya Ramos
• Host Institution: Centro de Ciências Exatas e de Tecnologia (CCET). Universidade Federal de São Carlos (UFSCAR). São Carlos , SP, Brazil
• Associated research grant: 13/07793-6 - CeRTEV - Center for Research, Technology and Education in Vitreous Materials, AP.CEPID

Abstract

The shift factor (K) is a coefficient found in glass-forming materials thatcorrelates different heating rates with the viscosity of the material. In other words,measuring the fictive temperature (Tf, the temperature at which the glassy materialupon cooling from the melt has its structure frozen in) at various heating ratesexhibits the same dependence of viscosity on temperature. Knowing K enablessimple viscosity determination via calorimetry. Several literature works report acomposition-independent value of K = 11.35 ± 0.16, however, recent studiescontradict this, indicating that the shift factor for lead metasilicate glass (PbSiO3) iseither K = 10.1 ± 0.2 or K = 10.9 ± 0.1. The fact is that both studies relied on hightemperature viscosity data from the literature, which may significantly influence theresults due to possible compositional deviations. Therefore, this project aims toevaluate the shift factor of a series of lead silicate glasses, (PbO)x(SiO2)100-x, with x= 30, 40, 50, 60, and 70 mol%, using calorimetry (DSC) at various heating rates andviscosity measurements at both low and high temperatures, in order to determinewhether there is indeed a correlation with glass composition. (AU)