Paweł Stoch

associate professor

Current project

Phosphate glasses network containing iron and/or aluminium from experimental and theoretical point of view.

Funding agency: National Science Center of Poland, grant number 2017/27/B/ST8/01477

Role: Prime Investigator

Summary:

The subject of the research is phosphate glasses containing iron and/or aluminium ions as well as glass-ceramic materials resulting from their crystallization. Phosphate glasses are materials of high technological and application importance. They are characterized by relatively low melting point, relatively high coefficient of thermal expansion, and higher electrical conductivity compared to conventional silicate glasses. Their high thermal expansion coefficient with low liquidus temperature makes them an attractive material as glass sealants for metal-ceramic connections. On the other hand, phosphate glasses with the addition of Ca have biocompatibility and can serve as dental or bone implants. The addition of rare earths makes them potential materials for optoelectronic and laser applications. Due to the existence of easily hydrating P-O-P bonds, they are used as carriers of micronutrients in modern fertilizers with controlled solubility. On the other hand, phosphate glass is characterized by rather low resistance to environmental factors such as water vapor. Nevertheless, the partial replacement of phosphorus by iron and/or aluminium leads to a significant increase in the water-resistance of these glasses. This increase is extremely fast and glass with a content of about 40 mol% Fe2O3 is characterized by very high chemical resistance. It is currently considered as a material for binding, in its structure, particularly hazardous forms of radioactive waste containing significant amounts of chlorides and sulfates, which cannot be immobilized by cementation or vitrification in borosilicate glasses.

The research we are conducting as part of the project is the analysis of interactions between ions in a solid-state. This leads to a specific ordering of the glass network. This gives the glass-specific features. Thus, as a project goal, the determination of phosphorus glass network structure from the P2O5-Fe2O3-Al2O3 system was made by experimental research and molecular modeling using classical and quantum molecular dynamics methods.

In the proposed glasses, iron and aluminium ions can play a dual role depending on the coordination number adopted to oxygen. These atoms can, on the one hand, build a glass network and, on the other, be its modifiers. Currently used research methods do not give an unambiguous answer to this question. This causes that there is a whole range of different types of glass network models. The project envisages proposing a model for the structure of phosphate glasses containing iron and/or aluminium ions using detailed experimental studies in combination with molecular modeling. It is planned to conduct a detailed study of the thermal properties of glasses from the P2O5-Fe2O3-Al2O3 system. On this basis, the conditions for their crystallization will be determined. As a result of the crystallization process, a devitrified materials will be obtained. The obtained glass and the devitrified materials will be subjected to structural research using FTIR, Raman, Mössbauer, MAS-NMR, and XRD spectroscopy. Their mechanical properties will also be determined by the nanoindentance method. Simultaneously with the experimental research, theoretical simulations will be conducted. In the first place, it is expected to carry out a classic molecular dynamics simulation. For this purpose, based on previous studies on glass crystallization, data on density, mechanical properties, as well as based on literature data, the form, and parameters of the potential of interactions between particular ions as well as simulation conditions will be selected. As a result of the simulations carried out, the structure of the glass network of the proposed glasses will be pre-determined. The simulations performed using classical methods will serve as a starting point for the quantum molecular dynamics simulation using the Carl-Parrinello method. As a result, it should lead to a very realistic prediction of the properties of the new glasses based on computer simulations as well as the impact of other additives on them. The simultaneous combination of experimental and theoretical methods in application to amorphous materials gives the project an innovative character.

The project’s results were published in:

  1. Pawel Goj, Aleksandra Wajda, Agata Stoch, Ireneusz Krakowiak and Pawel Stoch An Insight into the Correlation between Chemical Composition Changes of Aluminum-Iron-Polyphosphate Glasses and Thermal Properties Materials, Volume 14, Issue 8, 2021, P-2065.
  2. Pawel Goj, Aleksandra Wajda, Pawel Stoch, Raman imaging as a useful tool to describe crystallization of aluminum/iron containing polyphosphate glasses Journal of the European Ceramic Society, Volume 41, Issue 8, July 2021, Pages 4572-4583.
  3. Paweł Stoch, Paweł Goj, Aleksandra Wajda, Agata Stoch, Alternative insight into aluminium-phosphate glass network from ab initio molecular dynamics simulations, Ceramics International, 47(2021)1891-1902.
  4. Paweł Goj, Paweł Stoch, Influence of CaO on structural features of polyphosphate P2O5-Fe2O3-FeO glasses by molecular dynamics simulations, Journal of Non-Crystalline Solids, 537(2020)120014.
  5. Paweł Stoch, Paweł Goj, Małgorzata Ciecińska, Piotr Jeleń, Artur Błachowski, Agata Stoch, Ireneusz Krakowiak, Influence of aluminum on structural properties of iron-polyphosphate glasses, Ceramics International, 46(2020)19146-19157.
  6. Małgorzata Ciecińska, Paweł Goj, Agata Stoch, Paweł Stoch, Thermal properties of 60P2O5-(40-x)Al2O3-xNa2O glasses, Journal of Thermal Analysis and Calorimetry, 139(2020)1763-1769.
  7. Paweł Goj, Małgorzata Ciecińska, Magdalena Szumera, Paweł Stoch, Thermal properties of Na2O – P2O5 – Fe2O3 polyphosphate glasses, Journal of Thermal Analysis and Calorimetry, 142(2020)203-209.
  8. Paweł Stoch, Paweł Goj, Małgorzata Ciecińska, Agata Stoch, Structural features of 19Al2O3-19Fe2O3-62P2O5 glass from a theoretical and experimental point of view, Journal of Non-Crystalline Solids, 521(2019)119499.
  9. Paweł Goj, Piotr Jeleń, Barbara Marczewska, Paweł Stoch, Effect of β-Irradiation on the structure of iron polyphosphate glass, Journal of Nuclear Materials, 523(2019)198-205.