Mattia Biesuz

High entropy oxides are the “far west of ceramurgy”: the configurational entropy-stabilization of new phases promises the development of new materials with still unexplored properties. Some recent results have shown that this class of materials is particularly interesting in the field of Li-ion batteries because of their large Li storage capacity and conductivity. However, still little is known about their point defect chemistry and how Li is incorporated into their structure.

The goal of this thesis is to deepen the defect chemistry of high entropy oxides through high-temperature diffraction, thermal expansion measurements, density measurements, XPS, positron annihilation spectroscopy, and electrochemical measurements. The work might include a short secondment abroad.

The predicted residual stresses induced by the chemical tempering of silicate glasses are far larger than the experimental ones. This suggests that at the ion-exchange temperature the glass can reduce the mechanical stresses through a deep structural re-arrangement. 

The goal of this master thesis activity is to study ion-exchange processes where diffusion is aided by the application of an external electric field. We aim at reducing the ion exchange temperature down to 350°C (or below) to minimize stress relaxation taking place through thermally activated processes. The students will characterize the residual stresses by optical method, and the glass structure after ion exchange by NMR, Raman, FTIR, and positron annihilation spectroscopy.

The predicted residual stresses induced by the chemical tempering of silicate glasses are far larger than the experimental ones. This suggests that at the ion-exchange temperature the glass can reduce the mechanical stresses through a deep structural re-arrangement. 

The goal of this master thesis activity is to identify the stress relaxation mechanisms. This will be the base to engineer new glass compositions/chemical tempering conditions to maximize the residual compressive stresses on the glass surface. To achieve the goals the student will combine different structural characterization techniques including NMR, Raman, FTIR, and positron annihilation spectroscopy.