Luiz F.P. Pereira graduated at Metallurgical Engineering from the Federal University of Minas Gerais in Brazil (2017). During his engineering degree, he was awarded a scholarship to spend eighteen months at the University of Derby (UK), where he obtained a “Diploma of higher Education in Mechanical Engineering”. His engineering final project was developed at the University of Lille (France). There, structure-property relationship of molybdenum-phosphate glasses has been investigated and led to an article publication.1 Luiz started his Ph.D. in November 2017 at CEA Marcoule and Mines ParisTech under Dr. Annabelle Laplace and Dr. Franck Pigeonneau supervision. His current project is entitled “Mechanism of oxygen bubble formation in nuclear waste vitrification context”. He is curious and interested by materials science, especially glasses.

Luiz F.P. Pereira

Annabelle Laplace1, Franck Pigeonneau2.
1 CEA Marcoule, DEN, DE2D, SEVT, LDMC – BP17171, F-30207 Bagnols-sur-Cèze, France
2 MINES ParisTech, PSL Research University, CEMEF – Centre de mise en forme des matériaux, CNRS UMR7635, CS 10207, Claude Daunesse 06904 Sophia Antipolis cedex, France

Bubble formation in glass melts has been subject to research for decades. Not only glass scientists but also geochemists study their formation mechanisms and their behaviour. There are different types of bubbles generated during glass making process. In glassmaking industry, CO2, N2, H2O are the main observed gases. Other different types of gases, such as molecular oxygen (O2) are also observed. Bubbles containing O2 gas mainly result from redox reactions of polyvalent elements in glass melts and that could help to evacuate smaller bubbles containing gases from raw material decomposition.
The present work aims to study the mechanisms of oxygen bubble formation coming from redox reaction of polyvalent elements incorporated in the glass melt. Borosilicate glass composition has been selected for its interest as glass matrix for nuclear waste conditioning. Cerium is selected as polyvalent element as it may be found in nuclear waste. The chosen material was characterised in terms of physical properties, such as viscosity, high temperature density and surface tension. Post-mortem scanning electron microscope (SEM) approach was used to observe bubbles in the investigated material after thermal treatment varying temperature and duration. In order to support the understanding of oxygen bubble formation, glass oxygen partial pressure (PO2) evolution with time for different temperatures was reached experimentally as well.
This talk covers the main results obtained by SEM post-mortem approach. Bubble number density and size evolution with time at 1000°C are presented in figure 1. Taking into consideration these two latter features along with the mentioned characterisations, a model for oxygen bubble formation in glass melt is presented. The impact of temperature and time on oxygen bubble formation are also taken into account.

Figure 1: Left – normalised probability density function (PDF) versus diameter.
Right – cumulative distribution function (CDF) versus diameter.