Tiefenprofiluntersuchungen an ionenleitenden Gläsern mittels Flugzeit-Sekundärionen-Massenspektrometrie (ToF-SIMS)

In this thesis the behavior of ion-conducting bioactive glasses and polymer membranes is examined. For the analysis, time-of-flight secondary ion mass spectrometry (ToF-SIMS) is mainly used. Thus, a three-dimensional representation of the distribution of elements in the sample is provided. After the synthesis of the bioabsorbable glasses of the general formula CaXA (X% CaO; (55-X)% A2O; 45% P2O5 with X = 20, 30, 40, 50 and A = Na, K, Rb, Cs) and the bioactive 46S4 glass (46.4% SiO2, 25.2% Na2O, 25.2% CaO, 3.2% P2O5) two different experiments are carried out. First, an electro-thermal poling experiment is performed. In this case, an electric field is applied to the glass at an elevated temperature, resulting in a formation of a sodium depletion region under the anode. Combining impedance spectroscopy, depolarization current measurement and ToF-SIMS depth profiling the formation of the depletion region can be observed. The thickness of the depletion layer and the amount of the stored charge can be determined as well. Subsequently, the influence of the polarization on the bioactivity of the glasses is tested. Bioactive glasses are able to form bone-like material on their surface when they come in contact with tissue or bones of the human body and so they strongly bind to the organic material. To study the bioactivity the polarized glasses are placed temporarily in a solution that exactly replicates the conditions of the human body like ion content and pH (simulated body fluid). The subsequent analysis of the surface shows a clear influence of the polarization on the bioactivity and the solubility of the glasses. On the other hand, the technique of the bombardment induced ion transport (BIIT) is applied to the glasses and polymer membrane. Thereby alkali ions are deposited on the surface of the samples using an guided ion beam. This produces a electrical potential gradient that leads to the migration of ions through the material. With ToF-SIMS this diffusion profile can be measured. The depth profile is then compared with the theory using the Nernst-Planck-Poisson equations. Finally, the concentration dependent diffusion coefficient of the alkali ions can be calculated.